sign in sign up
<<
Home , 576p, 8VSB, Aperture grille, Bally Sports San Diego, Beam deflection tube, Blanking level

Dictionary of and Technology Newnes is an imprint of Elsevier Science.

Copyright © 2002, Elsevier Science (USA). All rights reserved. [This page intentionally left blank.] No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the publisher.

Recognizing the importance of preserving what has been written, Elsevier Science prints its books on acid- paper whenever possible.

Library of Congress Cataloging-in-Publication Data

ISBN: 1-878707-99-X

British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library.

The publisher offers special discounts on bulk orders of this book. For information, please contact:

Manager of Special Sales Elsevier Science 225 Wildwood Avenue Woburn, MA 01801-2041 Tel: 781-904-2500 : 781-904-2620

For information on all Newnes publications available, contact our World Wide Web home page at: http://www.newnespress.com

10 9 8 7 6 5 4 3 2 1

Printed in the of America Dictionary of Video and Television Technology

Keith Jack Vladimir Tsatsulin

An imprint of Elsevier Science

Amsterdam Boston London New York Oxford Paris San Francisco Tokyo [This is a blank page.] CONTENTS

Preface ...... vii About the Authors ...... ix

# ...... 1 A ...... 3 B...... 22 ...... 39 D ...... 75 E ...... 100 F ...... 113 G ...... 129 H ...... 135 I ...... 146 J ...... 159 K ...... 161 L ...... 164 ...... 176 N ...... 193 O ...... 199 P ...... 205 Q ...... 224 R...... 227 S ...... 239 T ...... 271

v U ...... 289 V ...... 292 W ...... 311 X ...... 316 Y ...... 317 Z ...... 319

APPENDIX A: Associations ...... 321 APPENDIX B: Standards Organizations...... 325

vi PREFACE

Just a few short years ago, the applications for video were fairly confined— analog broadcast and , analog VCRs, analog settop boxes with limited functionality, and simple analog video capture for PCs. Since that time, a tremendous and rapid conversion to has taken place, with consequent changes in broadcast standards and technologies. “Convergence” is the buzzword that has come to mean this rapid coming together of various technologies that were previously unrelated. Today we have: • DVD and SuperVCD players and recorders, with entire movies being stored on one disc, with newer designs supporting capability for even higher video quality.

• Digital VCRs and , that store and video on tape.

• Digital settop boxes, which interface the television to the , satellite, or broadcast system. Many also support interactivity, , sophisticated graphics, and access.

• Digital , which receive and display digital TV broadcasts, either via cable, satellite, or over-the-air. Both standard-definition (SDTV) and high-definition (HDTV) versions are available.

• Game consoles, with high-definition graphics and powerful process- ing, and with the newer systems supporting DVD playback and internet access.

vii • Video editing on the PC, using real-time MPEG decoding, fast MPEG encoding, and other powerful techniques.

• Digital transmission of content for broadcast, cable and satellite sys- tems, with the conversion to HDTV underway.

This is a complex and ever-changing and there is a need for a refer- ence that documents the evolving terminology, standards, and acronyms. The Dictionary of Video and Television Technology contains the most up-to- date terms and their usage. The book is a valuable reference for engineers working in the fields of analog and digital video, broadcast personnel, tech- nicians, or anyone charged with the task of understanding, using, or implementing video and television signals. We hope this companion vol- ume to the popular Video Demystified, 3rd Edition proves just as valuable to those creating and working with the converging technologies of the 21st century.

viii ABOUT THE AUTHORS

Keith Jack has architected and introduced to market over 25 multimedia ICs for the PC and consumer markets. Currently director of product mar- keting for Sigma Designs, Inc., he is working on next-generation digital video and audio solutions. He has a BSEE from Tri-State University in Angola, Indiana, and holds two patents for . Vladimir Tsatsulin is a retired military officer with an electronics engineer- ing degree from MVIZRU Military Academy. Following his retirement from the military, he worked as a TV technology professor at “Elektrons” state company in Riga, and later was a member of the expert group that developed a TV and PC database for the Invention Machine Co. Today Tsatsulin is a technical writer and translator for the Belorussian State Univer- sity of Informatics and Electronics in Minsk, . He is co-author of The English-Russian Dictionary on Television and Audio/Video Equipment, a - dard reference now in its third edition.

ix [This is a blank page.] #

0h A reference time moment at the mid-level crossing cable, many digital cable systems continue to use point of the leading edge of the sync pulse. This QAM technology. is the default timing reference in the TV environ- 2-D Two-dimensional. ment (as opposed to the active line start which is (2+3)D mode A mixture mode in which both the commonly used in computing environments). Syn.: 2D-image and the 3D-image are displayed as mixed. line datum; line start [moment]; time datum. 2.5D effect A digital video effect similar to a 2D effect 0v A reference time moment given by the line datum but with the appearance of three dimensions. E.g., coincident with the beginning of the first equaliz- a picture can be distorted and put on the surface of ing pulse (525-line standard) or with the beginning a disk to give the illusion of being put on a sphere. If of the first broad pulse in the vertical sync group this disk is rotated 90 degrees about its x-axis it will (625-line and 1125-line standards). Commonly ac- be seen to be a single line, providing its 2D nature. cepted as a timing reference point for framing A true 3D effect may be rotated and viewed about and SCH determination in 625-line standard. Syn.: any axis and still maintain an appropriate shape. frame datum. 2D effect A digital video effect where picture trans- 1.78:1 16:9 ratio for “wide-screen” TV. formations and manipulations are restrained within 10-bit The generic description for equipment having a an arbitrary plane surface. data path 10 bits wide. Such a path can represent 2H Sync pulse with period of two lines, the rising edge data having up to 1024 different values (four times of which marks the start of a line with positive that of an 8-bit system). polarity of V component in a PAL sig- 100% [color] bars 1. In PAL/SECAM countries and in nal or the start of a Dr line in Dr/Db sequence in a : color bars with the nomenclature 100/0/100/0. SECAM chrominance signal. Syn.: 7.8 kHz; Dr/Db 2. In the USA and other NTSC countries: color bars ; PAL switch; PAL switching signal; SECAM with the nomenclature 100/7.5/100/7.5. switch. 12-12-12 rule The maximum number of stations that 3C Computer, communication, consumer. Color can be owned by one company: 12 TV stations, 12 videophone is an example of a 3C integrated product. AM stations, and 12 FM radio stations. This 3-D Also 3D. Three-dimensional. rule of the FCC replaces the longtime limitation of 3-D display technology A technique, developed by 7-7-7. Sanyo Electric Co. Ltd of Osaka, that does not re- 12-14 truck Ku-track, named for the GHz range. quire special viewing glasses. Instead, a proprietary 12-14 unit Ku-track. image splitter separates images into right-side and Number of active vertical scanning lines in inter- left-side elements. The splitter works in conjunction laced scan format specified by HDTV standard with a conventional LCD to produce the image. A adopted by the FCC. See Interlaced scanning. special algorithm and digital-signal processing can 1,300-nm optical-wavelength transmission window produce real-time 3-D images from ordinary 2-D sig- An optical wavelength frequently used for cable-TV nals such as conventional TV and video programming. trunk and other multi-km fiber-optic systems. 3:2 pull-down A method used to map (24 fps) 16-VSB system Zenith’s 16-level digital transmission onto 480-line TV (30 fps), in which one system, using vestigial sideband modulation tech- occupies three TV fields, the next two, and so forth. nology. Can send two digital HDTV MPEG-2 signals Since the two fields of alternate TV frames are from on a single 6-MHz cable channel, doubling the num- different film frames, operations such as rotoscoping ber of HDTV signals on a cable channel. Alternately, are not possible, and editing must be done care- it can be used to deliver as many as 24 SDTV MPEG- fully. Advanced equipment can unravel the 3:2 2 channels, or a mix of HDTV and SDTV channels. sequence to allow frame-by-frame treatment. With a data rate of 38.8 megabits/s, it has twice the 3/4-inch U (EIAJ) Video The first data rate of 8-VSB. Although designed for digital mass-produced and practical videocassette format

1 4:1:1 Y’CbCr

and machine to be used in the US. Introduced by AM radio stations, and seven FM radio stations; now in 1971, this format uses the trade 12-12-12. name U-matic (shortened to just U), which has be- 7.8 kHz See 2H. come synonymous with the machine. It was en- 780p Number of active vertical scanning lines in pro- dorsed as the standard for 3/4" tape recording by gressive scan format specified by HDTV standard the Electronic Industry Association of Japan (EIAJ). adopted by the FCC. See Progressive scanning. 4:1:1 Y’CbCr Means that for every four horizontal Y’ 8mm Hi-Fi High sound quality built into the 8mm video samples, there is one sample each of Cb and Cr. recording format. This format was originally designed 4:2:0 Y’CbCr Means that for every block of 2 x 2 Y’ to automatically incorporate AFM hi-fi recording in samples, there is one sample each of Cb and Cr. all 8mm camcorders and VCRs. Unlike standard VCRs There are three variations of 4:2:0 YCbCr, with the that place the separate audio track longitudinally difference being the position of Cb and Cr sampling on the tape, 8mm AFM units “write” the audio track relative to Y. on the tape diagonally along with the video infor- 4:2:2 Also CCIR 601, ITU-R BT.601. The most com- mation. The high quality sound, however, is restricted monly accepted standard for component digital to one monophonic track, thereby not necessarily video. The active picture area of the luminance Y’ producing stereo. Some 8mm units are equipped component is 720 horizontally by 480 or 576 with Pulse Modulation, a digital audio record- lines vertically (per frame). Each of the color differ- ing process that can produce stereo audio. ence signals, Cb and Cr, are sub-sampled horizon- 8mm/VHS, VCR; Sony A dual-deck VCR that can edit tally so that, per frame, they each have 360 pixels from 8mm to VHS and vice versa. Both decks have horizontally by 480 or 576 lines vertically. At 8 bits high-end features such as stereo audio and the ca- per , the total active picture rate is 166 Mbps. pability of accommodating high- recordings The full including line and field blanking (Hi8 and S-VHS), but in standard resolution only. In- periods is 216 Mbps. Likewise for 10 bits per pixel, cluded are several editing features, including jog/ the active picture data rate is 207 Mbps with the shuttle controls. full bit rate at 270 Mbps. This is the standard for 8mm video. A mini-video format that uses digital studio equipment; the terms “4:2:2” and a compact cassette (60-, 90- or 120-minute lengths) “601” are often used synonymously (but techni- and is capable of producing hi-fi audio. Flying erase cally incorrectly). heads provide smooth edits and clean scene transi- 4:2:2 Y’CbCr Means that for every two horizontal Y’ tions. The video quality of the 8mm format equals samples, there is one sample each of Cb and Cr. that of VHS in many respects and surpasses it, al- 4:4:4 Y’CbCr Means that for every Y’ sample, there is though only slightly, in color reproduction. In addi- one sample each of Cb and Cr. tion, its built-in hi-fi audio capability offers superior 4fsc Four times the of the NTSC or PAL color sound to competing formats. However, 8mm video . Also the sampling rate of a D2 digital is not compatible with most home VCRs. Some mod- video signal with respect to the subcarrier frequency els have added advanced features, such as automatic of an NTSC or PAL analog video signal. focus, glitch-free editing and the capability of su- 5.1 A type of using six audio chan- perimposing time and date upon an image. Other nels: left, center, right, left rear (or side) surround, competitive formats include Hi8, S-VHS, S-VHS-C, right rear (or side) surround, and a subwoofer, con- VHS-C. sidered the “.1” since it is -limited. 8-pin connector A type of jack commonly used for the 601 See 4:2:2. VTR-to-monitor connection; provides a full set of au- 7-7-7 rule An FCC restriction that formerly limited own- dio and video connections—one ground and one lead ership by one company to a maximum of seven TV each for audio-in, audio-out, video-in, and video-out. stations (of which only five could be VHF), seven 8-VSB See vestigial sideband.

2 A

A The cable TV midband channel occupying 120-126 ABC Commonly refers to the American MHz. May also refer to an advertising rate for com- Corporation or the Australian Broadcasting Corpo- mercials (see AAA rate). ration. May also be an abbreviation for automatic A&E Abbreviation for Arts and Entertainment cable brightness control. channel. aberration In CRT displays, a of an image A.F. Abbreviation for audio frequency. caused by failure of the beam to focus all A/D Short for analog-to-digital converter. points accurately on the screen. A/D converter Short for analog-to-digital converter. ABL Abbreviation for automatic brightness limiter. A/PAL An early version of PAL used in Ireland and the above the line A budget category that includes the . Characteristics were 405 lines per artistic or creative elements, primarily nontechnical frame, 50 fields per second, 2:1 interlaced. personnel and activities. A-1 The cable TV midband channel occupying abstract set A set, such as on a TV program, 108-114 MHz. that has a neutral background. A-2 The cable TV midband channel occupying AC adapter An external device for equipment that 114-120 MHz. May also refer to Antenne-2, or the converts (AC) power into direct second French state broadcast TV network. current (DC) power. AA The cable TV hyperband channel occupying AC coupled AC coupling passes a signal through a 300-306 MHz. May also refer to an advertising rate to remove any DC offset, or the overall for commercials (see AAA rate). voltage level that the video signal “rides” on. One AAA rate The most expensive advertising rate for ra- way to find the signal is to remove the DC offset by dio and TV commercials. AA is the next lower rate, AC coupling, and then do DC restoration to add a followed by the A rate, and finally the B rate (the known DC offset (one that we selected). Another lowest rate). reason AC coupling is important is that it can re- A-B color frame code Another name for color frame move large (and harmful) DC offsets. code. AC hum A low-pitched sound (50 or 60 Hz) heard A-B mix A transition where one video source (A) fades whenever AC power is converted into sound. It is out while another video source (B) fades in. The usually the result of ground loops or inadequate amount of each source used to generate the result shielding of cables. is determined by the relative position of a mixer fader AC interlock A safety function on equipment that turns arm. When the fader arm is all the way at the source off power when the back of the device is opened. A side, then only video source A appears at the AC transmission See Alternating-current transmission. output. Also means cross-fade or mix. AC’97, AC’98 These are definitions by Intel for the A-B roll A video editing system where two or more audio I/O implementation for PCs. Two chips are sources are used, in conjunction with a video mixer, defined: an analog audio I/O chip and a digital con- to dissolves and other transitions between troller chip. The digital chip will eventually be re- the different sources. placed by a software solution. The goal is to increase A-B roll editing An editing procedure using two syn- the audio performance of PCs and lower cost. chronized sources of the same program material. AC-3 Original name for Dolby® Digital. Also, the ver- A-B switch A device that inputs two video sources (A sion of Dolby compressed audio used in some movie and B), and outputs either A or B. Since it doesn’t theaters for surround sound. affect the signal quality, it is also called a passive ACATS Abbreviation for Advisory Committee on switcher. Advanced Television Service. A-B test A direct comparison of sound and/or picture ACC Abbreviation for automatic color control. quality of two sources, or devices, by playing one, accelerating See . then the other. accelerating electrode An electrode that accelerates

3 acceleration voltage

the of an electron beam. See also Electron acoustics The reverberation of sound, or lack of it, in gun. a room. Acoustics can affect the results of the audio acceleration voltage A voltage that produces an ac- recording. Some parts of a room have “dead” spots celeration of a beam of charged particles. while others are more “lively.” The built-in micro- accentuation Another name for pre-emphasis. phone of a video operates better in dead accentuator Another name for a circuit that provides areas; hiss and occur in live portions of a room. pre-emphasis. ACS Abbreviation for alternate channel selectivity. access In videotex, the number of frames requested action line See Line. by a user. action shot See Moving shot. access time In video, the amount of time it takes to action track A digital video effect where fast-moving reach the desired point of a program. objects appear to remain on-screen. This effect re- ACE head On newer VCRs, the control-track and au- quires motion detection to isolate the moving ob- dio heads are combined into one unit. This head is jects so that they may be frozen and accumulated often referred to as the ACE head, for Audio, Con- into a single image. The technique was developed trol, and audio Erase. for sports action replay analysis. Also called image achromatic Without color or varying brightness trail-freeze. information. May also refer to being capable of trans- active filter A filter that requires power to operate. mitting without breaking it up into its constitu- Also refers to a filter designed to reject noise and ent . Also see Monochromatic. ripple that may otherwise be transmitted to a TV achromatic color A shade of gray. Also see Variables . of perceived color. active image The visual portion of a video signal. achromatic lens A lens corrected for chromatic aber- active image area See Active picture area. ration. In its simplest form, it consists of a pair of active interval The portion of an active line that con- lenses, designed so that the dispersion produced by tains video information. Also see Trace interval and one lens (being divergent) corrects the dispersion Sawtooth. produced by the other (being convergent). Usually, active lines The scan lines of a video signal that con- a convex lens of crown glass and a concave lens of tain picture information. Most, if not all, of these flint glass are used. The combination brings all col- lines are visible on the display. Scan lines that do not ors closer to the same focal point. contain video information are usually said to be in achromatic locus The area on the chromaticity dia- the vertical blanking interval. gram that contains all points representing accept- active material A fluorescent material used in CRT able reference white standards. Also called the displays. achromatic region. active mixer An audio mixer that compensates for achromatic point A point on the chromaticity dia- signal losses. Some active mixers can also modify gram representing an acceptable reference white the audio signal by compressing it, adding echo, or standard. modifying a specific frequency range. achromatic region See Achromatic locus. active part The portion of a video that car- achromatic stimulus A visual stimulus that gives the ries picture information. Also called analog active sensation of white light and thus has no color. part. ACK Abbreviation for automatic . active picture area The useful portion of a video dis- acoustic delay line A delay line used to delay sound. play. It may be mechanical or electronic. active pixel region The area of the display used for acoustic feedback This may occur when the input to the actual display of information. There may be a a system (such as a microphone) receives sound from visible region not used to display information, called the output of the system (such as a speaker), form- the border region. ing an uncontrolled closed loop. It usually results in active position The position on a display where sub- a high-pitched squeal. sequent actions will occur. acoustic holography Using a single-frequency sound active satellite See . to produce a 3D image of an object. It is usu- active scan line See Active lines. ally viewed on a CRT display. active signal correction A common name for the acoustic wave A wave that is transmitted through a fuzzy logic used in some video equipment. See ASC. solid, liquid, or gaseous material as a result of vibra- active video The part of the video waveform that tions of the particles. Also called a sound wave. contains picture information. Most of the active acoustic wave device A device used in signal pro- video, if not all of it, is visible on the display. cessing that transfers acoustic waves on a substrate, active-matrix LCD Active matrix is a technique for enabling a wide variety of processing functions to making color LCD displays, by using to be performed. Delay lines, attenuators, phase make up each of the pixels. The most common type shifters, etc. may be implemented. of active matrix LCD is based on a technology known

4 addressable box

as TFT. The two terms, active matrix and TFT, are proportional to the fineness of detail in that por- often used interchangeably. tion. A portion of the picture with little detail can actuator In general, a device, under the control of an be transmitted with very few bits, and this provides electrical signal, which carries out a mechanical ac- extra time for transmitting portions with high de- tion. It may also refer to the VCR device that causes tail. A buffer is used to restore the original spatio- the video head to be moved to the videotape track. temporal relationship. If the entire picture has high In satellite TV, it controls the movement of the satel- detail, the buffer may become overloaded, so the lite dish so that it receives the strongest signal. rate of information transfer is reduced by reducing ACTV Abbreviation for Advanced Compatible high-frequency details. This, of course, reduces the Television. image quality by introducing artifacts. ACTV-1 In 1988, a proposed system described by ADC, A/D Abbreviation for analog-to-digital converter. Isnardy had undergone computer simulation at the Add-A-Vision A combined film and TV camera sys- Research Center. The system was tem based on the Mitchell BNC but of British de- named ACTV-1, for “Advanced Compatible TV, First sign. A variant of Add-A-Vision known as EFS (Elec- System.” It was intended to provide a 16:9 wide- tronic Filming System) is basically similar, but em- screen picture, while being compatible with stan- ploys the Mitchell Mark 2 camera. dard NTSC receivers, and use the standard 6-MHz additive color system Color based on the addition NTSC channel. To accomplish this, a second subcar- of light. For video, the three primary colors are , rier was added to the NTSC signal. This second sub- green, and blue. These may be added together in carrier was a 395th multiple of one-half the line fre- varying amounts to generate any other color. Color quency, or about 3.1075171 MHz. An additional printing and film use the subtractive color system. “helper signal,” quadrature modulated with the pic- additive primaries Three colors from which all other ture carrier, was used to improve the vertical resolu- colors can be generated by adding some mixture of tion. The ACTV-1 receiver was to be a 16:9 wide- them together. screen 525-line progressive TV. add-on recording Also called transition editing re- ACTV-2 This proposed system used two 6-MHz NTSC cording. Most VCRs allow pause during recording, channels, with the ACTV-1 system being used for but due to timing problems, there is usually a distur- one of the channels. The ACTV-2 system was an bance of the picture during playback at the place extension of the ACTV-1 system. The ACTV-2 where the pause was used. To eliminate this distur- receiver was to be a 16:9, 1050-line interlaced TV. bance, transition editing recording backs up the tape adaptation The dynamic change of the type of audio for about 2.2 seconds during pause recording. When or video processing performed, dependent on the the pause is released, the deck will play back for sound or picture content. about 1.2 seconds while aligning the control timing adapter A device that makes electrical and mechani- already on the videotape to the desired timing. Af- cal connections between equipment not originally ter about 1.2 seconds, the deck to the intended to be used together. record mode, with the overall effect of there being adaptive comb decoder A NTSC/PAL no artifacts during playback. that uses an adaptive comb filter. address search Also known as VASS or VHS Address adaptive comb filter A filter that performs luminance Search System, it is a VCR feature that permits the (Y) and chrominance (C) separation based on the user to assign a number to each index stop by mark- picture content. The frequency responses of the Y ing it magnetically or electronically. Most VCRs use and C filters look like the teeth on a comb, hence one or more search methods to find a specific scene the name comb filter. on a videotape. These machines automatically place adaptive control Processing that varies automatically an electronic mark on the tape each time the Record to generate the desired results regardless of the in- button is activated, thereby marking the beginning put. The automatic gain control (AGC) is an example of every program recorded. Other features allow for of an adaptive control: the gain of the var- specific scenes within a program to be marked. ies automatically to generate a constant output level, address track In VCRs, a path for laying down a spe- regardless of the input level. cific code number for each frame of video on the adaptive range coding A process that condenses the tape. This code consists of a time so that, for ex- entire NTSC or PAL video bandwidth into a digital ample, 00:27:14:03 would be read as 00 hours, 27 signal that can be recorded on tape. The technique minutes, 14 seconds, and 3 frames. requires the use of high-grade metal-particle tape. addressability The ability of a cable or satellite TV adaptive transform/sub-band coding See Zenith provider to control a set-top box in a subscriber’s -Compatible HDTV System. home. If communication from the set-top box to adaptive transformation A video compression tech- the provider is also possible, it is called a two-way nique. The amount of information that must be system. Otherwise, it is called a one-way system. transmitted for a particular portion of the image is addressable box A set-top box used by cable and

5 addressable converter

satellite TV providers that supports addressability. It the additional information to display an improved connects between the cable outlet (or ) picture, usually with a 16:9 . None of and the TV, allowing viewers to order and receive the techniques were popular, although PALplus was pay-per-view programs and subscription channels. introduced in . addressable converter See Addressable box. Advanced (ADTV) A proposed fully addressable decoder See Addressable box. digital HDTV system, since replaced by the ATSC addressable programming A cable or satellite TV HDTV standard; Advanced Television Research Con- provider may enable or disable a specific program sortium (Thomson Consumer Electronics, , from being decoded and displayed by a specific ad- NBC, David Sarnoff Research Center, Compression dressable box. For example, a viewer orders a pay- Laboratories Inc.). The baseband input was 1050 per-view movie. They call a phone number; a com- lines, 2:1 interlaced, and 59.94 fields/s. Source cod- puter answers and confirms the request. The pro- ing was based on the ISO MPEG draft specification vider then sends a coded message, which is received for the transportation of moving images over com- by the viewer’s addressable set-top box. The mes- munication data networks. ADTV modified the sage temporarily enables that particular set-top box MPEG standard to handle the more stringent require- to descramble the channel, offering the desired pro- ments of HDTV, and it referred to its scheme as gram. MPEG++. After video and audio signals were digi- addressable set-top box See Addressable box. tized and encoded, the transport encoder separated addressable system A cable or satellite TV system data into two streams in order of their importance that supports addressable programming. to overall system operation. Data critical for main- adjacent channel A channel that is immediately next taining the basic integrity of received pictures — typi- to another channel in frequency. For example, NTSC cally the gray-scale levels, audio signals, data- channels 5 and 6 are adjacent. However, channels 4 headers and motion descriptors — were assigned and 5 are not since they are separated by non-TV High Priority (HP). The low-frequency coefficients and signals. then the higher frequency (fine detail) coefficients adjacent sound carrier The RF carrier that conveys formed the Standard Priority (SP) data stream. As- the audio information for the channel immediately signment states were adaptive, so SP data could tran- below the desired channel. scend to the HP stream when HP loading was light. adjacent video carrier The RF carrier that conveys The two streams were formatted into separate 148- the video information for the channel immediately byte data transport cells. The cell format was similar above the desired channel. to data-communication packets. The single-byte ser- adjacent-channel interference Interference caused vice header identified the type of data being carried by an adjacent channel. in the main 120-byte block. The two data streams adjacent-channel selectivity The ability of a receiver were quadrature amplitude-modulated onto sepa- to reject signals on adjacent channels. rate carriers contained within a 6-MHz band. The adjustment switches For a display, the controls for HP channel was 960 kHz wide; the SP channel oc- horizontal synchronization, vertical synchronization, cupied 3.84 MHz, and was filtered to have mini- luminance, hue, contrast, etc. mum power at the NTSC carrier . ADTV ADO Abbreviation for Digital by Ampex receivers had similar functioning filters so that a co- Corporation. This is a video special effects device channel NTSC station did not interfere with HDTV for creating effects such as flips and twists. reception. ADP Abbreviation for automatic data processing. advanced editing Special VCR features to assist in ADSL Asymmetric Digital Subscriber Line, a technol- making glitch-free, professional-looking edits. Such ogy that converts existing copper lines features may include assemble editing, edit preview, into access paths for multimedia and high- superimposer, and the flying erase data communications while maintaining the regu- head. lar phone voice services. The ANSI T1 committee has advanced systems See System terminology. standardized Discrete Multi-Tone (DMT) as the line advanced television A family of TV systems that im- code to be used in ADSL. See DMT. prove the quality of standard TV. This includes EDTV, ADTV Abbreviation for Advanced Digital Television. IDTV, HDTV. advance ratings When an audience-survey company Advanced Television Systems Committee The ne- provides a preview (by telephone) to a client of the cessity for standardizing the HDTV format in the ratings of a radio or TV program or station. United States required the FCC to make a choice Advanced Compatible Television Several techniques that would have a large economic impact. To make were developed to transmit additional information the choice with impartiality and expertise, the FCC within the NTSC and PAL video signal. Conventional appointed an ad hoc committee, the ATSC, to study TVs would ignore the additional information, and competing proposals, including field testing, and display the usual picture. Advanced TVs would use make a recommendation to the FCC.

6 alpha channel

Advisory Committee on Advanced Television Ser- to compress files and reduce high digital video and vice Established in 1987 at the request of the United audio data rates. States television broadcast industry. The original plan alias See Aliasing. was to develop an advanced television system using alias frequency An erroneous lower frequency ob- reserved, but unassigned, frequency spectrum. An- tained when a periodic signal is sampled at a rate other objective became the development of a digi- equal to or less than twice the signal’s frequency. tal HDTV standard. aliasing Distortion in a video signal. It shows up in AES/EBU digital audio interface A commonly used different ways depending on the type of aliasing in digital audio interface specified as a result of coop- question. When the sampling rate interferes with eration between the Audio Engineering Society and the frequency of program material the aliasing takes the European Broadcasting Union. It is a serial trans- the form of aliasing frequencies that are known as mission format for two-channel linearly represented sidebands. Spectral aliasing is caused by interference digital audio data. Each audio sample is carried by a between two frequencies such as the luminance and sub-frame containing: 20 bits of sample data, 4 bits chrominance signals. It appears as herringbone pat- of auxiliary data (which may be used to extend the terns, wavy lines where straight lines should be and sample to 24 bits), 4 other bits of data and a 4-bit lack of color fidelity. Temporal aliasing is caused when preamble. Two sub-frames make up a frame that information is lost between line or field scans. It contains one sample from each of two audio chan- appears when a is focused on a CRT nels. Frames are further grouped into 192 frame and the lack of scanning synchronization produces blocks. AES/EBU signal includes channel status data a very annoying flickering on the screen of the re- containing information about signal emphasis, sam- ceiving device. In sampling, aliasing is the impair- pling frequency, channel mode (stereo, mono, etc.), ment produced when the input signal contains fre- use of auxiliary bits (extend to 24 bits or other uses), quency components equal to or higher than half of and a CRC (cyclic redundancy code) for error check- the sampling rate. Typically produces jagged steps ing. There are several allowed sampling frequencies on diagonal edges. See also Nyquist limit. Syn.: alias. within the 32-kHz to 48-kHz range, the most aliasing noise A distortion component that is created common being 44.1 and 48 kHz. when frequencies present in a sampled signal are AFC Abbreviation for automatic frequency control. equal to or greater than one-half the sample rate. AFM See Beta hi-fi. alignment In VCRs, the angle the video heads make AFT Abbreviation for automatic fine tuning. with the tracks on the videotape. Misalignment of- afterglow See Persistence. ten causes distortion, signal loss, video noise and AFV Abbreviation for audio-follows-video. . May also refer to TV tuners and IF AGC Abbreviation for automatic gain control. operating at the correct frequency. aggregate Gathered into, or considered as, a whole. alignment disc See Test disc. A picture image is perceived as an aggregate of in- alignment tape A special-purpose videotape contain- dividual points. ing audio and video reference signals that are used agile receiver A satellite receiver that can be tuned to to correctly adjust the recording and playback heads any desired channel. of VCRs. Alignment tapes are produced by manu- AIF Audio Interchange File. An audio file format de- facturers and are not generally available to the pub- veloped by Apple® Computer to store high quality lic. They are normally for use within the company sampled sound and musical instrument information. and its authorized service centers. aircraft flutter Sudden changes in the quality of a TV alkali metal An alkali-producing metal, such as lithium, picture, caused by the reflection of the TV signal cesium, or sodium, that has photoelectric charac- from an aircraft flying somewhere over the direct teristics. Commonly used in and cam- path between a and receiver. The re- era tubes. flected signal interferes with the normal signal at all-channel tuning The ability of a TV or VCR to the receiving . receive all the available channels. airplane flutter. See Aircraft flutter. all-digital This term means that everything is done airwaves Slang for radio waves, used in radio and TV digitally—storage, processing, editing, etc. No broadcasting. analog signals are present in the system. ALC Abbreviation for automatic level control or auto- alpha See alpha channel and alpha mix. matic light control. alpha channel The alpha channel is used to specify alfecon An iron/silicon/aluminum alloy, used for video an alpha value for each sample. The alpha value is heads. used to control the blending, on a sample-by-sample alfesil An iron/silicon/aluminum alloy, used in video basis, of two images: pixel = (alpha)(pixel A heads. color) + (1 - alpha)(pixel B color). Alpha typically has algorithm A formula, or set of steps, used to simplify, a normalized value of 0 to 1. In a computer environ- modify, or predict data. Complex algorithms are used ment, the alpha values can be stored in additional

7 alpha mix

bit planes of frame buffer memory. A 32-bit frame aluminized screen A CRT display that has a thin coat- buffer actually has 24 bits of color, 8 each for red, ing of aluminum on the back of the phosphor layer. green, and blue, along with an 8-bit alpha channel. Electrons readily penetrate the coating, activating Also see Alpha mix. the phosphors to produce an image. The aluminum alpha mix This is a way of combining two images reflects outward light that would otherwise go back using the alpha channel. The box that appears over inside the tube, thereby improving the brilliance and the left-hand shoulder of a news anchor is put there contrast of the display. Also called a metal-backed by an alpha mixer. Wherever the samples of the little screen, metallized screen, and mirror-backed screen. box appear in the frame buffer, an alpha number of AM, A method of encoding “1” is put in the alpha channel. Wherever they don’t data onto a carrier, such that the amplitude of the appear, an alpha number of “0” is placed. When carrier is proportional to the data value. the alpha mixer sees a “1” coming from the alpha amateur TV (ATV) A part of ham radio in which hob- channel, it displays the little box. Whenever it sees a byists send and receive TV (also called fast-scan TV) “0,” it displays the news anchor. (Of course, it pictures. doesn’t matter if a “1” or a “0” is used, but you get AMA-type screen Actuated-mirror array (AMA) dis- the point.) play system for civilian uses. Developed by Daewoo alpha wrap When the videotape almost completely Electronics Co. Ltd., Seoul. The AMA system can be encircles the head drum of the VCR, permitting the applied to almost all kinds of TVs, projectors and use of only one head. laptop portable displays. If used on 40" or larger alphabetic Pertaining to letters of the alphabet. TVs, it can drastically increase the screen brightness alphageometric In videotex, simple picture descrip- because AMA-type screens are 10 times more effi- tion instructions that enable line drawings, colored cient in light production and 2,000 times quicker in polygons, curved lines, etc., in addition to text, to response time than LCD screens. be displayed. An accepted standard for ambience Reflected light or sound that reaches the alphageometric display is the North American Pre- viewer or listener from a variety of directions. Light sentation Level Protocol Syntax (NAPLPS). See or sound waves bounce off the ceiling, walls and Alphamosaic, Alphaphotographic. other boundaries of an area. alphamosaic In videotex and , a method of ambient light The normal illumination. The term is coding that displays a mosaic of 2 x 3 rectangles. commonly used with projection TV systems and This method uses a simple and inexpensive decoder, video , since how these devices function in but is restricted to text and graphics that do not ambient light is one method of measuring their require curved or diagonal lines. See Alphageometric, effectiveness. Alphaphotographic. ambient noise Refers to normal background noise, alphanumeric Using both letters and numbers. which can be measured with a sound-level meter. alphanumeric code Pertaining to a character set that ambient-light filter A filter used in front of a display represents numbers or letters of the alphabet. to reduce the amount of ambient light reflecting off alphanumeric display The display of information us- the display. The filter, generally of a dull finish, can ing only letters and numbers. When a display is called be incorporated into the faceplate of the display or an alphanumeric display, it is usually not capable of it can be a separate sheet of plastic. displaying sophisticated graphics. American Museum of the Moving Image A show- alphaphotographic In videotex, a method of coding place that emphasizes the hardware of the TV and that allows photographic quality images to be dis- film industry, including costumes, sets and other played. The time needed for transmission and the paraphernalia. Located in Queens, New York, the complexity of decoding restricts its use. See museum exhibits a variety of equipment, ranging Alphageometric, Alphamosaic. from 19th-century devices to the Sony Walkman. alternate channel selectivity The ability of a tuner to Other highlights include interactive exhibits, video focus on one channel at a time, while rejecting inter- art displays, video screenings and a host of consumer ference from adjacent channels. The tuner’s ability to products based on popular TV shows and personali- suppress this interference is measured in dB; the higher ties. the number, the better the performance. A rating of American Television Alliance (ATVA) Consists of about 80 dB is considered excellent. This term should General Instrument Corp. (GI) and Massachusetts not be confused with capture ratio, referring to two Institute of Technology (MIT). channels occupying the same frequency. AML Abbreviation for amplitude-modulated link. alternating-current transmission A method of trans- AML frequencies In an AML system, there are four mission used in TV in which the direct-current com- groups of frequencies: C, D, E, and F. Group C chan- ponent of the luminance signal is not transmitted. nels add 12,646.5 MHz to the VHF frequency. Group A direct-current restorer must be used in this form D channels add 12,705.7 MHz to the VHF frequency. of transmission. See direct-current transmission. Group E channels add 12,898.5 MHz to the VHF

8 analog-to-digital converter

frequency. Group F channels add 12,958.5 MHz to analog The representation and measurement of the the VHF frequency. performance or behavior of a system by continu- A-mode See MUSE-9 system. ously variable physical entities such as current, volt- AMOL/SID Abbreviation for Automated Measurement ages, etc. Analog data yields an exact replication of Of Lineups/Source IDentification. An identification the original information. Most conventional VCRs, signal included in the vertical blanking interval (VBI), for example, record information using the analog broadcast by virtually all TV networks. It is used by process. Analog differs from digital, which duplicates TV-ratings services to identify the network, show, information in a discrete, or discontinuous, form, as date, time, hour, minute and second of a broadcast. with more advanced VCRs. As part of the AMOL system, the signal helps a TV- analog active lines See Active lines. ratings service verify when specific shows and com- analog active part See Active part. mercials were broadcast on local stations. analog channel A transmission channel that is used amp Short for amplifier. to transmit an . amplified coupler A device typically used to boost a analog component format A format that uses three TV signal so it can be adequately received by several signals to specify color and brightness. The most TVs and VCRs throughout the home. common video formats are YPbPr and YUV. amplifier A device that outputs a magnified version analog See Analog component of the input signal. format. amplifier power The amount of magnification an analog encryption A video scrambling method that amplifier can produce, usually specified in watts. The operates within the standard video bandwidth. Some larger the number, the greater the magnification the approaches may result in degradation of the origi- amplifier can produce. nal video signal when it is decoded. amplitude Strictly, the peak value of a signal in the analog monitor In reality, all displays based on CRT positive or negative direction. The difference be- technology are analog. Some analog monitors are tween minimum and maximum values is the peak- incorrectly called digital monitors since they ac- to-peak amplitude. May also refer to the value of cept digital signals, and convert them to analog a signal in the positive or negative direction at a internally. particular moment. analog signal processing The conventional method amplitude distortion See Distortion. used by audio and video equipment manufacturers amplitude fading See Fading. to reproduce a signal. A broadcast signal is produced amplitude modulation A method of encoding data in the shape of a series of waves, each wave height onto a carrier, such that the amplitude of the carrier representing voltage while the distance between is proportional to the data. peaks in these waves determines the frequency of amplitude-modulated link This system converts cable that part of the signal. These components of the TV frequencies to frequencies and trans- signal, along with others, are separated, amplified mits the signal to a receiving site, where the micro- and fed into VCRs, TV sets and so on for reproduc- wave frequencies are converted back down to the tion. Much of the original quality of the signal, how- standard cable TV frequencies. The AML system used ever, is lost through this process, although some units by cable operators is called community-antenna ra- are better able to rebuild the signal than others, dio service (CARS) and is in the frequency band of thereby producing a better picture. A more sophis- 12-12.95 GHz. The studio transmitter link AML ser- ticated approach to reproducing a signal is by means vice is used for connecting studio facilities, usually of digital signal processing. in a city, to the transmitter or up-link site out of the analog tuning A method of tuning a TV, VCR, etc. city. The antenna systems used at these frequencies Analog tuning permits setting the system to any are usually parabolic dishes of 4-10 feet in diam- channel within its frequency range. This tuner, be- eter. Also see Cable television service. cause of its manual capability, either of the mechani- amplitude-shift keying A method of encoding data cal or electronic variety, differs from the frequency- onto a carrier, such that a finite number of different synthesis tuner, that is preset. amplitude levels of the carrier are produced. analog video Video signals that use a continuous- anaglyph An image made up of two slightly different time signal, with varying amplitude. views, in contrasting colors, of the same subject. analog/digital converter See Analog-to-digital When viewed through a pair of corresponding color converter. filters, the image seems three-dimensional. analog-to-digital converter A device that transforms anaglyphic method A three-dimensional viewing a signal from analog form to digital form. This is method based on colored light, such as the familiar done by taking samples of the analog signal at regu- red and green viewing glasses. It usually yields im- lar intervals. Each analog sample value is then con- perfect pictures because the filters fail to eliminate verted into a binary code. For video applications, the complementary color completely. additional functions are usually incorporated, such

9 analogue

as automatic gain, filtering and clamp- from the air. Also, a or set of metal rods con- ing. An ADC for digitizing video must be capable of structed for the purpose of intercepting waves in sampling at 10 to 150 million samples per second. the air and changing them into an electrical signal Sometimes also called a digitizer. that is sent to a TV receiver. TV antennas are af- analogue The European spelling of analog. fected by various external factors, such as the loca- anamorphic Viewed picture format with geometric tion of the , the contours of the land deformation of the wide-screen picture aimed to and certain obstructions, and the physical condition achieve full vertical screen occupation while using of the antenna and connecting cables. Most anten- the conventional TV display. nas (except satellite dishes) utilize the dipole tech- anamorphic lens A special that allows nique: two equal rods or arms, each as long as 1/4 the user to make in wide-screen format the wavelength of the anticipated signal. The an- using a standard video camera. tenna lead-in is located at the center of the two arms. ANC/WNL Abbreviation for Automatic Noise Cancel- Since direction is important for maximum reception, ing and White Noise Limiting. These circuits are in most antennas have a combination of reflecting rods some TVs to process the video and sound signals. and directors (shorter rods) to provide additional di- Non-video data transmitted within a rectivity. Commercial TV antennas are usually de- digital video data stream, usually during the hori- signed for local (15-20 miles), suburban or mid-range zontal and vertical blanking intervals. It may be digital (20-30 miles), or fringe use. audio, teletext, etc. antenna combiner A device that combines the sig- ancillary timecode BT.1366 defines how to transfer nals from several antennas, each of which is aimed VITC and LTC as ancillary data in digital component at a different TV station. Antenna combiners are interfaces. helpful where all the TV transmitters are not located angle modulation Modulation where the angle of a in a single direction. sine-wave carrier is the characteristic varied from its antenna coupler A device that is used when more normal value. Phase modulation and FM are par- than one TV is connected to a single antenna. Also ticular forms of angle modulation. known as an antenna splitter, it helps prevent im- angle of view (AOV) The area or width of a subject or pedance mismatch and interference between TVs. scene that a lens takes in or covers. The AOV de- Several commercial types are available. The resistance pends on the focal length of the lens and is given by antenna splitter prevents some impedance mismatch the equation cot A/2 = 2F/W, where A is the AOV, F and offers some isolation, but contributes to a re- is the focal length of the length and W is the width duction in signal strength. The antenna of the photosensitive surface. The smaller F, the splitter reduces both impedance mismatch and greater the AOV. For example, a 12.5mm focal length insertion loss. has a wider angle than a 75mm lens. antenna farm The location for the transmitting an- ANIK The name given to Canadian TV, and more re- tennas for most or all of the TV stations in an area. cently, to Canadian TV satellites. ANIK is an Inuit antenna rotator A small motor mounted externally on word meaning “brother.” ANIK satellites have both an antenna mask and remotely controlled to adjust 4-GHz C-band and 12-GHz Ku-band transponders. the antenna direction so that it receives the best pos- animation Also called time lapse. See Frame-by-frame sible signal from a TV station. In some areas where recording, intervalometer, interval timer, optical ani- multiple TV stations do not transmit their signals from mation, pipeline architecture, pixilation, time lapse a central location, a single is not ef- video. fective. Either several antennas or a single antenna anode-voltage-stabilized camera tube Syn.: high- with a rotator must be used for best reception. electron-velocity camera tube. See Camera tube. See antenna splitter See Antenna coupler. also . antenna-switching circuitry Controls to select alter- anomalistic period The interval of time between one nate inputs to the TV set (pay decoder, TV games, passage of a satellite through its apogee and the VCR, etc.). Found in the front-end stages of some next consecutive passage. TV sets. It improves reception of cable-TV signals. anomalous propagation Accidental transmission of anti-alias filter A filter (typically a lowpass filter) used VHF radio waves beyond the horizon, probably to bandwidth-limit a signal to less than one-half the caused by temperature inversion in the lower atmo- sampling rate. Also called an anti-aliasing filter. sphere. anti-aliasing The process of smoothing jagged edges, ANSI Abbreviation for American National Standards especially along curved or diagonal edges of dis- Institute. This organization sets standards for the played objects, such as graphics and text. computer languages, electrical specifications, com- anti-aliasing circuitry An electronic circuit that per- munications protocols, etc. forms anti-aliasing. Many professional character antenna In TV, that part of a transmitter or receiver generators offer anti-aliasing as one of their features. facility that sends out waves into or accepts them anti-aliasing filter See Anti-alias filter.

10 aperture response

anti- tail gun A device in a TV camera tube to so, and to have a Gaussian distribution of energy, reduce or eliminate streaks, called comets. so that the signal changes with a more rounded tran- anti-copy signal See Anti-piracy signal. sition. This effectively reduces the high frequency anti-logarithmic amplifier Used in 3D-image TV cam- content of the signal, and compensation must be era systems to form a depth video signal. made by increasing the gain in the high frequen- The French teletext system. cies, taking care not to exceed the bandwidth of antiPAL test pattern A video signal that has a delib- the channel or unduly increase noise or introduce erately wrong PAL switch function. The polarity of phase distortion. the U component, instead of the V component, is aperture corrector An equalizer designed specifically switched. This enables measuring the performance to offset aperture distortion. of the line averaging function in the PAL decoder. aperture delay The time from an edge of the input When it works correctly, the display has no color clock of the ADC until the time the ADC actually takes since the antiPAL chrominance is cancelled by the the sample. The smaller this number, the better. decoder’s line averaging. aperture distortion Attenuation of the high-frequency anti-piracy signal A method of preventing pre-re- components of a TV picture signal caused by the corded videotapes from being “pirated” or dupli- finite cross-sectional area of the scanning beam in cated illegally. One system places a special signal the camera. The beam then covers several mosaic electronically on the tape; another modifies the hori- globules in the camera simultaneously, causing loss zontal and vertical sync pulse and the color burst of picture detail. phase, causing rolling or other forms of instability in aperture grille A slotted metal screen located just the picture during the copying process. Supposedly, behind the inside of a TV display tube’s screen sur- this signal has no effect during playback on a TV face, used to limit the points at which the electrons set. Also called anti-copying signal. hit the phosphor coating of the screen. A Sony in- anti-reflection coating A thin coating deposited on vention, the function is similar to that of a shadow the surface of glass to reduce reflection of ambient mask, the purpose of both being to ensure the re- light. production of a true color TV picture. See also Color anti-top flutter pulse Disables the phase detector picture tube. during equalization and framing times. aperture jitter The uncertainty in the aperture delay. AO A category of the movie rating system that indi- The aperture delay time changes a little bit each time, cates the program is for adults, 18 and older. and that little bit of change is the aperture jitter. AOD Abbreviation for audio optical deflector. aperture mask . An opaque disk be- AOM Abbreviation for audio optical modulator. hind the faceplate of a color picture tube; it has a APC Abbreviation for automatic phase control. precise pattern of holes through which the electron APEL Abbreviation for Advanced Product Evaluation beams are directed to the color dots on the screen. Laboratory. aperture reduction ring An accessory on some pro- aperture An opening through which electrons, light, jection TV systems to make the image appear sharper radio waves, or other radiation can pass. The aper- by cutting down on the f stop, or aperture, of the ture in the electron gun of a CRT determines the projecting lens. The disadvantage is that using a size of the electron beam. The aperture in a TV cam- smaller aperture also decreases the amount of light era is the effective diameter of the lens that controls transmitted to the screen. the amount of light entering the camera tube. The aperture response The aperture response of a com- dimensions of the horn mouth or parabolic reflec- ponent or system is a graph of the peak-to-peak tor determine the aperture of a microwave antenna. amplitude of its response (e.g., of the variations in The aperture in a lens is an adjustable orifice con- reflected light) as a function of the TV line number. trolling the amount of light transmitted by a lens. Assume that a pattern of black-and-white lines of The maximum diameter of the aperture in relation varying widths is scanned by a narrow light beam, to the focal length of the lens determines its theo- and the peak-to-peak variation in the reflected light retical speed. Its effective speed depends also on from the black and light lines is measured. On lines the transmission of the glass elements of the lens. that are much wider than the diameter of the spot, aperture correction Method of compensating for loss these variations will be of full amplitude. As the width of higher picture frequencies caused by the scan- of the lines is decreased so that the scanning spot ning spot in a camera tube having a finite size, and always overlaps a portion of black and white line, thus failing to respond sharply to sudden vertical the amplitude of the variations will decrease. When boundaries between dark and light areas. Consider the width of the lines is twice the diameter of the a square spot of finite size scanning a sharp black- spot, the variations disappear. The width of these to-white transition. The resulting signal output lines is specified by its reciprocal, the number of al- changes level with a linear slope. In practical elec- ternate black and white lines (counting both black tron devices the spot tends to be circular or nearly and white lines) that can be fitted into the vertical

11 aperture slit

dimension of the picture. This parameter is known art card A cardboard (generally 11"x14") with a dark as the TV Line Number. The aperture response of a background and light letters (although it may be component or system can be specified either by its black letters on a white background). As used in TV, response to a square-wave pattern, i.e., alternate it contains credits and other information and is dark and light bars, known as the contrast transfer mounted on an easel in front of a TV camera. function (CTF), or by its response to a theoretical Article 810 See National Electrical Code. pattern in which the cross-sectional darkness of the artifacts in a video signal; spurious signals bars varies sinusoidally, the modulation transfer func- created artificially (hence the term artifact) by the tion (MTF). The CTF is physically measurable, but imaging process. One of the most common is cross- the MTF is more useful for analytic purposes. Aper- luminance, a characteristic of composite systems ture response is a universal criterion for specifying employing a color subcarrier. It is a dot pattern that picture definition and other aspects of imaging sys- results from failure of the subcarrier signals on suc- tem performance. It can be used for film images, cessive frames to cancel each other completely, e.g., camera lenses, TV camera imagers, video amps and on vertical edges of areas with high saturation. They other bandwidth-limiting components, the scanning can also be produced by moving objects in an inter- process, receiver picture tubes, and the human eye. laced scanning and appear as interline flicker. They aperture slit In 3D-image display with parallax bar- can be eliminated or greatly reduced by the use of rier, an interval between the stripe barriers. A viewer progressive scanning and component color systems. observes the displayed image through the aperture In the video domain, artifacts are blemishes, noise, slits by both eyes. snow, spots, etc. When you have an image artifact, APL Abbreviation for average picture level. something is wrong with the picture from a visual apochromatic lens A lens that has been corrected for standpoint. Don’t confuse this term with not hav- chromatic aberration for three colors. ing the display properly adjusted. For example, if the apple tube A color CRT with vertical red, green, and hue control is set wrong, the picture will look bad, blue phosphor stripes. The spacing varies at the top but this is not an artifact. An artifact is some physi- and bottom of the CRT, so the face somewhat cal disruption of the image. resembles an apple. artificial HDTV See Osborne compression system. Applegate diagram A diagram used to illustrate the artificial satellite See Satellite. principle of electron bunching in velocity-modulated Arts & Entertainment A cable TV advertiser-supported tubes (e.g., , traveling-wave tube). network specializing in cultural programs, documen- APT Abbreviation for automatic picture transmission. taries, variety shows and chiefly foreign feature . APTV Abbreviation for Associated Press TV. ASC 1. American Society of Cinematographers. 2. Aquadag A trademark of Acheson Colloids Co. for Active Signal Correction. Syn.: fuzzy logic (in Sony their brand of colloidal graphite in water, widely used usage—see, e.g., KV-27XBR50, Sony monitor/ to produce a conductive coating on the inside sur- receiver). face of the glass envelope for CRTs, where it col- ASCII American Standard Code for Information Inter- lects secondary electrons emitted by the fluorescent change, a code for transmitting data, made up of screen. Also used on the outside of some picture 128 letters, numbers, symbols, and special tubes, where it serves as the final capacitor of the each represented by a unique binary number. high-voltage filter circuit. ASIC Application specific . ARC Abbreviation for adaptive range coding. ASK Abbreviation for amplitude-shift keying. arc of good location The portion of the geosynchro- aspect ratio The width-to-height ratio of a display. It nous orbit (22,300 miles above the equator) that is usually expressed as two numbers separated by a provides coverage of a country. colon (width:height), such as 4:3 or 16:9. It may be archiving The storage of TV shows, movies and other expressed as a normalized single number, such as programs for future playback. 1.33. A 35-mm frame of film measures 36 x 24 mm, arcing A curved movement, as in the circular motion meaning it that it has an aspect ratio of 3:2. Since it of a TV pedestal camera, for which the instructions is different in size from a 4:3 or 16:9 TV screen, a are “arc left” and “arc right.” little bit of the sides or tops of movies are chopped ARO Abbreviation for Audio Receive Only, small dish off when displayed on TV. antennas used by radio networks for music and news aspect ratio conversion Conversion of the TV pic- programming distribution from TV satellites. ture geometry preserving the scanning standard, A-roll The primary material, as opposed to B-roll. In e.g., from the so-called anamorphic format to video editing, alternate scenes are arranged on two letterbox format. The video signal itself is aspect- reels (A-roll and B-roll) and then assembled. ratio independent. ARS board RF record/playback amplifier, servo circuit, aspheric corrector plate Lens, one surface of which and audio signal record/playback circuit; is specially shaped and is not part of the surface of a VCR. sphere as are the surfaces of most lenses. Used in

12 ATV

some large-screen TV projectors and some wide- variable bit rate services such as data and full mo- range room lenses. tion video) technologies. The result is the bandwidth ASR Abbreviation for automatic standard recognition. guarantee of combined with the assemble edits Edits that record all aspects of the high efficiency of . program (audio, video, and control) at the same time. asynchronous transmission The transmission mode assembly edit VCR feature that allows for clean tran- by which characters may be sent with random tim- sitions when adding audio or video sequences to ing. The data bits of each character are introduced prerecorded material. Also an editing technique in by a start bit and followed by a stop bit. The asyn- which pretaped segments are rerecorded end-to-end chronous mode is common for low-speed transmis- in a preferred order with selected transitions. sion, less than 2.4 Kbps. astigmatism 1. A type of spherical aberration in which ATC See ancillary timecode. light rays from a single point of an object do not ATM See Asynchronous Transfer Mode. converge at the corresponding point in the image. atomic bomb wipe A transition in which a scene is 2. A defect in an optical or electron lens that causes slowly moved up on the screen (suggesting an atom focusing in different axial planes to occur at differ- bomb cloud) as it is replaced by another scene. ent points along the lens axis. As a result of astig- ATR Abbreviation for audio tape recorder. matism, a point object gives rise to an image in the ATSC Advanced Television Systems Committee, a pri- form of a horizontal line at another point. Normally vate sector organization founded in 1982 to develop the best compromise is between these two points voluntary standards for the entire spectrum of where the image has the form of a of least advanced television systems, including high defini- confusion, representing equal vertical and horizon- tion (HDTV). See HDTV. tal resolution. ATSC A/49 Defines the ghost cancellation reference Astra ’s broadcast satellite. Frequency signal for NTSC. band: 11.2-11.45 GHz. Channels: 16 transponders. ATSC A/52 Defines the () audio compres- : linear. sion for ATSC HDTV. Asymmetric Digital Subscriber Line See ADSL. ATSC A/53, A/54 Defines ATSC HDTV for the USA. asymmetrical compression Techniques where the ATSC A/57 Defines the program, episode, and version decompression process is not the reverse of the com- ID for ATSC HDTV. pression process. Asymmetrical compression is more ATSC A/58 PSIP for . compute-intensive on the compression side so that ATSC A/63 Defines the method for handling 25 and the decompression of video images can be easily per- 50 Hz video for ATSC HDTV. formed at the desktop or in applications where so- ATSC A/65 Defines the program and system informa- phisticated are not cost effective. In short, any tion protocol (PSIP) for ATSC HDTV. compression technique that requires a lot of process- ATSC A/70 Defines the method for ing on the compression end, but little processing to for ATSC HDTV. decompress the image. Used in DVD-Video creation, ATSC A/90, A/91 Defines the data broadcast stan- where time and cost can be incurred on the produc- dard for ATSC HDTV. tion end, but playback must be inexpensive and easy. ATSC A/92 Defines IP multicasting using data broad- asymmetrical-sideband transmission Vestigial side- casting for ATSC HDTV. band transmission. attached A physical channel of a digital picture ma- asynchronous Refers to circuitry and operations with- nipulator is said to be attached to a logical channel out common timing (clock) signals. of a controller when the physical channel is success- asynchronous transfer mode (ATM) The technology fully acquired by the controller. selected by the CCITT in 1988 to realize a B-ISDN. It attenuation cable A cable designed to connect the is a fast, cell-switched technology based on a fixed- line-level audio output of one device to the low- length 53-byte cell. All transmissions level microphone input of another device. (whether audio, data, imaging or video) are divided attenuation distortion Syn. frequency distortion. See into a series of cells and routed across an ATM - Distortion. work consisting of links connected by ATM switches. attributes display In videotex, a means of modifying Each ATM link comprises a constant stream of ATM the presentation of characters on the screen. At- cell slots into transmissions that are placed or left tributes may be applied to the full screen, a full row, idle, if unused. The most significant benefit of ATM part of a row (serial), or to subsequently printed is its uniform handling of services allowing one net- characters (parallel). work to meet the needs of many broadband ser- ATV Abbreviation for Advanced Television or amateur vices. ATM accomplishes this because its cell-switch- television. 1. Advanced Television. Refers to any type ing technology combines the best advantages of of advanced TV system not presently in general use both circuit-switching (for constant bit rate services or production. The most recent example of ATV is such as voice and image) and packet-switching (for the HDTV system now reaching the marketplace.

13 ATV identification

ATV standards in North America include standard, audio cable tester A device designed to check cables enhanced, and high-definition versions. Although for shorts, phasing, continuity, etc. Used mostly by ATV systems are collectively considered to offer - professionals, the cable tester is used with standard ter quality than the NTSC signal, they can carry XLR3 pin-type cables and 3-conductor phone plugs. multiple pictures of lower quality and can also sup- audio cue The identification of an event by the use of port the cancellation of artifacts in ordinary NTSC a sound to alert those producing either an audio or signals. 2. Amateur TV. Sending pictures by ama- video tape to the fact that something is about to teur radio. You’d expect this abbreviation to apply happen. In video productions, certain words in the equally to fast-scan TV (FSTV), slow-scan TV (SSTV) script are used as “cues” to denote shifts in action, and fax, but it’s generally applied only to FSTV. camera position, microphones, or other technical ATV identification Short for Amateur TV identification. events; in electronic editing, audio cues are often ATVA Abbreviation for American Television Alliance. used to signal edit points. ATVA-P 6-MHz HDTV/EDTV format. Scanning: audio decoder Accessory used in conjunction with 787.5/59.94, sequential; channel coding: digital. The VCR-equipped stereo sound to send the signals to signal is sampled initially at a rate well above the various speakers for the purpose of creating a the- Nyquist limit. By various bandwidth reduction tech- atrical effect at home. The audio decoder picks up niques, the bit rate is brought within the capacity of the encoded stereo track on the videotape and in- a 6-MHz frequency band. terprets the appropriate paths for the signal, AU (also SND) Interchangeable file formats used in directing it to front, back and side speakers. Sun and other workstations. Basically it is a raw audio circuit A circuit to separate the audio data format preceded by a header. audio information from its carrier. This carrier is ac- audimeter An early device attached to home TV sets tually a subcarrier that is impressed onto the video and designed to measure a family’s viewing habits. carrier. Placed in representative homes, it was used by the audio distribution amplifier A device designed to A.C. Nielsen Company to measure the popularity of improve the sound quality of videotapes. A typical TV shows. The rating information determined the model contains a special filter circuit that decreases advertising rates of the shows and which shows buzz and other noise, a microphone input for mix- would be renewed or cancelled. In addition, the rat- ing sound-on-sound or adding narration, bass and ings revealed which channel or channels were treble tone control, etc. Some models provide a by- watched the most. pass feature for comparison of the affected and audio Latin for “I hear.” Used to describe frequencies unaffected signal. is often used to prevent capable of being heard by the human ear, between generation loss of audio when duplicating tapes. 15 Hz and 20 kHz. The sound segment of a video- audio dub To rerecord the audio portion of a video tape, VCR, VDP or other component. Also, the input, tape without disturbing the video portion of the sig- output, cable wire, attachment or other feature, ac- nal; also, to make a copy of an audio tape. cessory or software referring to the sound portion of audio dubbing narration The addition of narration a system. For example, there are audio inputs, audio to a videotape. The process requires the following cables, audio mixers, etc. Slang for sound. steps: Connect an external microphone into the mic audio alarm A feature that presents an audible signal input of the VCR. If you decide to use the built-in to tell the user that certain functions have been ac- mic of the video camera, connect the camera to the tivated. For instance, some VCRs beep once when VCR. Turn down the volume of the TV set to avoid recording begins and twice when it ends. feedback. Press Audio Dub, start the tape and the audio bandwidth In reference to videotape, the pa- narration. rameters or audio range of a tape. Although hu- audio dubbing recorded music The addition of mu- man hearing can respond to frequencies from ap- sic to a previously recorded videotape. One simple proximately 15 or 20 Hz to 20 kHz, the audio por- procedure is to place the mic next to one of the tion of a videotape has a bandwidth that is much speakers and switch the sound system to mono. shorter, somewhere from 50 Hz to 10 kHz, depend- Another, more desirable, method is to connect the ing on certain tolerance limits measured in dB. This amplifier or receiver of a stereo system or an audio- poorer response is caused by the small area of the tape recorder to the audio input of the VCR. tape allotted to the audio track and by the extremely audio equalizer See Equalizer. slow speed at which the tape travels past the audio audio essay A discussion of a specific film or program head. Higher-quality tapes extend these numbers on added to a commercial or videotape. Usu- both ends of the bandwidth to produce less distor- ally applied to classic works, the audio essay, which tion, hiss, etc. However, the audio bandwidths of utilizes one of the stereo channels, presents an “ex- most tapes do not present any true limitations to pert” who takes the viewer on an oral and visual many low-priced VCRs since these machines have journey of the production. The historian or critic an even shorter range than that of the videotape. covers such items as biographical information per-

14 audio/video dub

taining to the performers or director, missing or as an RCA-type plug, also has a small shaft, but it is added scenes, interviews and related still shots and surrounded by a petal-shaped metal cup. trailers. audio A device that can be used in audio; audio expander A feature on an audio processor to e.g., between a VCR and a stereo system. The audio improve the dynamic range of sound. processor usually contains such features as inputs audio expansion circuitry A development found in for microphones, VCRs and tape; a multiple-band TVs to provide a simulated stereo effect when re- equalizer for improved sound; a stereo delay simu- ceiving monaural broadcasts, cable TV, or signals lator and an audio expander to extend the from monaural external units (VCR, video disc player, dynamic range of the sound signals. etc.) connected to the rear panel audio/video inputs. audio response The ability to reproduce audio sig- audio for video The term to describe two compo- nals. Better-quality videotapes, especially those listed nents of audio production used in the video me- as HG (high grade), produce less hiss, or an above- dium: 1. High-quality stereophonic audio. 2. Multi- average signal-to-noise ratio. Tapes of poorer qual- track production techniques. The adaptation of these ity cause more audio distortion, hiss, etc. Audio re- components for the medium of video has given pro- sponse becomes more critical in the slower speed duction teams the ability to further improve TV modes of both Beta and VHS machines. The aver- through the introduction of creative, high-quality age listener can respond to frequencies from ap- audio. proximately 20 Hz to 20 kHz. Videotape, however, audio (AFM) See Beta hi-fi. falls short of this range, and is somewhere between audio head In video, a stationary magnetic head ca- 50 Hz and 10 kHz. Distortion and poor response pable of recording and playing back sound signals. result beyond these parameters. Tapes that exceed After receiving the audio signal, the head pulses it this audio bandwidth range (within certain tolerance onto the videotape during recording or takes it from limitations measured in dB) may be considered bet- the tape for reproduction during playback. The au- ter than average, although most home video ma- dio head is the third and last process that affects chines have a range narrower than that of most the videotape. The erase head is the first, followed tapes. DVD-Video and DVD-Audio offer much im- by the video heads. The audio head assembly is proved audio capabilities over videotapes. sometimes called the audio/control head and con- audio signal An electrical signal whose frequency falls tains three heads. One performs the audio record- within the audible range, the lowest measured at ing and playback, the second is designed for audio about 15 to 20 Hz and the highest at approximately dubbing and the third is the control track head that 20 kHz. transmits pulses onto the tape to control the start audio signal-to-noise ratio In videotape, a measure- of each alternate field, that is, to track the original ment that determines the loudness of an undistorted recorded signal. signal relative to tape noise. Audio signal-to-noise audio input A jack, often located at the rear of a VCR ratio is measured in dB. The larger the number, the and TV, that accepts audio signals. better the audio quality of the tape. audio modulation Refers to modifying a carrier with audio subcarrier The carrier wave that transmits au- audio information so that it may be mixed with the dio information within a video broadcast signal. video information and transmitted. Audio are frequency modulated. They are audio optical deflector (AOD) In 3D viewing systems, transmitted above the video, in the 4.5 to 8.0 MHz a device that serves as a horizontal scanning sys- range for NTSC and from 5.5 to 8.5 MHz for PAL/ tem. SECAM broadcasts. audio optical modulator (AOM) In 3D viewing sys- audio/control head See Audio head. tems, a device that serves as an optical modulating audio/video amplifier An accessory that adds sound system. The incident laser beam is intensity modu- processing to videotapes. The unit usually comes lated by the AOMs in response to a video signal. equipped with multiple audio/video inputs and out- audio output A jack, often located at the rear of a puts on its rear panel and digitally delayed audio VCR, DVD player, and TV, that outputs audio sig- modes that offer such special effects as stage, sta- nals. One, two (for stereo), or six audio outputs may dium, theater and matrix. The switchable amplifier be present. may power several channels, depending upon the audio plug The metal connector at either end of an watts-per-channel used. Some models accommodate audio cable that fits into component receptacles S-VHS and ED-Beta formats and feature a title gen- called jacks. The three basic types of audio plugs erator and a video enhancer. used in home video are mini-plugs, phono plugs and audio/video combiner Device serving to embed sev- phone plugs. The mini-plug is a smaller version of eral digital audio signals within a digital video signal and similar to the phone (for telephone) plug. Both stream (usually using a ). have a shaft that protrudes from a metal sleeve. The audio/video dub A video camera feature that per- phono (from phonograph) plug, often referred to mits the replacement of a current segment of audio

15 audio/video input

and video information on tape with new material. transitions produced in the video mode can auto- When audio/video dub is activated, new informa- matically activate fades between complex audio tion is inserted over both tracks. Most present cam- balances. Thus, video edits and scene transitions can eras offer this feature while other models provide contain more tightly synchronized crossfades. Also, only audio dub. AFV facilitates the addition of music, dialog and spe- audio/video input Basic RCA jacks found on VCRs cial audio effects to multi-track master tape before and TV monitor/receivers. Stereo models provide one a work print is produced. input for video and two for audio. Mono units offer audio-follows-video switcher A switcher that only one audio and one video jack. changes both audio and video sources with the push audio/video memory function A feature, found on of one button. some TVs, that permits optimum control set-ups to audio-mix control A stereo VCR feature that desig- be stored in memory for later recall. nates the amount of audio each channel feeds to audio/video mixer An editing accessory that allows the mono RF output. Table-model and portable ste- switching back and forth between two video sources, reo VCRs produce dual channel sound by means of such as two VCRs or a VCR and camcorder. Some two individual audio tracks laid down on the top A/V mixers offer additional features such as a fader, portion of the videotape. During the normal stereo wipe effects and special-effects generator. There are playback, both tracks are utilized. The audio-mix manual and electronic mixers. The electronic type control, however, permits an increase in either left- may use computer software and IR technology to or right-channel sound by simply rotating the knob. “learn” the tape transport commands of the record- audition The preliminary studio test of a performer, ing VCR. The user simply marks and names the act, or complete program for a TV or radio show. scenes on the footage to be edited and instructs augmentation channel See Terrestrial HDTV broad- the mixer that scenes should appear in the final tape. casting, MUSE-9 system. audio/video mute Special electronic circuits designed augmented reality A subset of virtual reality which to silence a TV set to circumvent annoying noise and attempts to generate a composite view for the user static. The mute feature also darkens the screen of the real world combined with a computer-gener- when the tuner is between channels or a videotape ated virtual scene. The technology has applications ends. Muting is sometimes referred to as blanking. in medicine, the military, entertainment, and manu- audio/video processor A multi-function device for facturing. use with various video components. The processor aural signal The audio portion of a TV signal; the usually provides inputs and outputs for audio and picture portion is called the video signal. video switching, an audio and video distribution aural transmitter The equipment used to transmit amp, a video stabilizer, an image enhancer, an RF the audio portion of a TV program. The audio and converter, etc. Some sophisticated models may of- video transmitters together make up the TV trans- fer color tint control, color intensity control, split mitter. screen enhancer, audio/video mute, a bypass switch AUSSAT ’s broadcast satellite. Frequency band: and a fade duration control. 12.25-12.75 GHz, 15 channels. Polarization: cross- audio/video receiver A separate unit designed to polarized continental beams. function as a control center of home entertainment authoring The process of using multimedia applica- systems. These systems usually accommodate sev- tions to create multimedia materials for others to eral audio inputs (CD, phono, tape and line) and view. Multimedia authoring uses many tools, from several video inputs (VCRs, DVD and cable/satellite the text editor or desktop publishing application, to set-top box). Some units permit two-way dubbing, tools for capturing and manipulating video images includes S-video and component video terminals and or editing audio files. offer memory that can store several surround sound authoring platform A computer that has been out- settings as well as “memorize” 30 stations for in- fitted with the hardware for creating material to be stant recall. viewed in a multimedia box. The video quality of audio/video signal See Signal. the authoring platform has to be high enough that Audio/Video Support System (AVSS) In DVI runtime the playback equipment is the limiting factor. software, the software package that plays motion auto channel search See Automatic channel scan. video and audio. auto cue and play Functions of VCRs. Just insert a audio/video switcher See Switcher. pre-recorded video cassette without an erasure pre- audio-follows-video An advanced feature of a pro- vention tab and the VCR turns itself on, then skips fessional/industrial editing console or switcher that over the no-signal portion and immediately starts permits the audio signal to follow the video edit playback at the beginning of the recording. operations, thereby facilitating audio crossfades to auto image stabilization Syn.: Lens stabilization. be produced under editor control. AFV offers a wide auto lock switch A feature, found on some range of possibilities for professional editors. Scene camcorders, designed to simplify and speed up the

16 automatic color circuitry

operation of the camera. When the user activates automatic backlight compensator Syn.: Backlight the Auto lock switch, it simultaneously sets the auto- switch. focus system, white balance, shutter speed and back- automatic backspace editing A VCR feature that light compensator. eliminates frame overlapping for glitch- and distor- auto play See auto cue and play. tion-free transitions. A built-in microprocessor, after auto program See Automatic channel scan. checking the signals of the control track, makes cer- auto repeat A VCR feature that allows the viewer to tain that a new recording starts at the end of the automatically play back a videotape. Auto repeat last frame each time a recording is begun from the differs from repeat play, a feature that plays a vid- Pause mode. eotape up to a specific point, stops and rewinds to automatic brightness control (ABC) 1. A TV receiver a previous point, and continues to play that portion circuit to keep the average brightness of the repro- of the tape indefinitely until the button is pressed duced image essentially constant. Its action is like again. that of an automatic volume control in a sound re- auto selection tool An imaging term. A tool that se- ceiver. Also called automatic background control. lects an entire area within a specified range of color 2. In a TV receiver, a circuit that automatically ad- values around a selected pixel. justs the brightness of the display in accordance with auto start See auto cue and play. the level of ambient light near the receiver. A pho- auto tracking A VCR feature that seeks out the most tocell may be used to measure the ambient light, its accurate playback tracking position for a given vid- output, after amplification, being used to control eotape. Since VCRs differ in their video head place- the grid bias of the picture tube. ment, some tapes, especially those recorded at the automatic brightness limiter (ABL) A circuitry in TVs slowest speed, may not play properly on other VCRs. to limit the maximum beam current to prevent Many machines come equipped with a manual track- overdriving the CRT. ing control to adjust for these variations; auto track- automatic channel scan A TV or VCR feature that ing handles these differences automatically. automatically programs the TV or VCR tuner memory auto/manual aperture control A device that places to lock in only active channels. Usually operated from the control of the f-stops or aperture openings into the unit, the ACS, sometimes de- the hands of the user. Many camcorders feature scribed as auto program, automatic channel search, automatic iris control, a less desirable feature for or programmable scan, searches up and down those some camera owners who prefer to make their own channels active in a particular area and ignores the selections. Some users choose to open or close the inactive ones that only bring in noise and static. lens one or two additional stops for special automatic channel search Automatic channel scan. effects. automatic chapter search A videodisc player feature auto/manual iris control Syn.: Auto/manual aper- that, when activated, takes the viewer to a particu- ture control. lar selection on the disc. This chapter search feature auto-assemble Generation of an edited master by a is often found on the remote control unit of a player. video or audio-for-video edit controller using an ex- automatic chroma control Automatic color control. isting edit decision list. automatic chroma correction See Automatic chroma autodialer A device which, when activated by a short gain control. code or mnemonic key or, in videotex, by the selec- automatic chroma gain control Automatic correc- tion of a number from a menu, causes the dialing of tion of chrominance channel gain typically using a prerecorded telephone number. subcarrier burst level as a reference. Syn.: ACC, auto-focus Also called automatic focus. A process built automatic chroma correction. into some video cameras in which an impulse of in- automatic chrominance control Automatic color visible light is emitted to the subject and returned control. to a pair of IR sensors. This distance is then calcu- automatic color circuitry Electronic circuits built into lated by an IC. Finally, a drive motor adjusts the lens. some TV sets, TV monitors and monitor/receivers , and Akai were among the first com- designed to retain factory-preset color levels. Auto- panies to feature auto-focus in their cameras. Some matic color circuitry locks in this balanced color ar- of today’s video cameras offer a more sophisti- rangement regardless of discrepancies between cated—and more accurate—auto-focus technique. channels and scenes. One disadvantage or criticism Instead of relying on the not-too-precise IR reflec- of this feature concerns the viewer’s preference— tion to measure distances, the focal adjustment of the colors may appear too weak, too intense, too these later cameras operates directly off the bluish, etc. However, the color circuitry usually comes image-sensing elements. with a switch that can be deactivated so that the auto-framing See Automatic framing. colors can be adjusted manually. Also a technician automatic background control Automatic bright- can modify the automatic color circuitry so that it ness control. operates more to the owner’s liking.

17 automatic color compensation automatic color compensation A feature found on automatic focus compensation A projection TV fea- some TV sets which monitors the three color guns ture that adjusts for the disparity in projection dif- or electron beams so that the colors retain their ac- ferences between the lens and the center of the curacy for the life of the CRT. Under normal condi- screen and the lens and the edges of the screen. tions, tubes lose their color intensity as they age. automatic focusing Electrostatic focusing in which With the addition of the special electronic circuitry, the focusing anode of a TV picture tube is internally the TV set can compensate for this imbalance. connected through a to the cathode so that automatic color control (ACC) A circuit in a color TV no external focusing voltage is required. set to keep color intensity levels essentially constant automatic framing A video camera zoom lens fea- despite variations in the strength of the received color ture that keeps the size of the subject constant. signal. Also called automatic chroma control and Whether the subject moves toward or away from automatic chrominance control. the camera, the automatic framing function main- automatic color purifier Automatic degausser. tains the original size of the image. Canon was the automatic color tint control See Color tint control. first company to offer the special zoom lens fea- automatic contrast control A circuit that maintains ture, also known as auto-framing, on some of its the contrast of the TV picture at a constant average higher-price 8mm camcorders. level. The manual contrast control determines the automatic frequency control (AFC) A circuit that average level and the automatic contrast control locks onto a chosen frequency and will not drift away maintains this average, despite variations in signal from that frequency; a technique to lock onto and strength as different stations are tuned in. track a desired frequency. Used in TV transmitters, automatic contrast correction A TV feature that helps VCRs, and TV receivers to keep undesirable changes to bring out almost imperceptible detail in overly to a minimum. bright or extremely dark sections of a screen image. automatic gain control (AGC) A control circuit that automatic degausser An arrangement of degauss- automatically changes the gain (amplification) of a ing coils mounted around a color TV picture tube, signal so the desired output signal remains essen- combined with a special circuit that energizes these tially constant despite variations in input signal coils only while the set is warming up after being strength. In a camcorder, this feature is designed to turned on. The coils demagnetize any parts of the increase the signal only to the degree that the im- receiver that have been affected by the earth’s mag- age gains an even intensity. AGC increases a blank netic field or by the field of any nearby home appli- signal to gray; in poorly lighted scenes it adds noise ance. Automatic degaussing permits a color TV re- to shadowed areas and produces less saturated col- ceiver to be moved around a home without read- ors. Usually in the form of a switch, the AGC when justing purity controls. Also called automatic color activated has one disadvantage: some deterioration purifier. occurs in the video image. In most VCRs a circuit automatic digital tracking A VCR feature that auto- controls the intensity of incoming audio and video matically monitors its own playback. Special circuitry signals so that they match predetermined output continually compares the RF signals on the video- levels while taping off the air or recording with a tape to reference signals in the circuit. If the two camcorder. AGC is different from the sensitivity signals are not in sync, the special circuit emits a switch that affects the general amplification of the correcting signal to the capstan servo, which per- video signal. In audio, the AGC automatically boosts mits the video head to make adjustment for the best or attenuates audio signals to optimum levels. AGC possible signal. is also known as automatic level control, a feature automatic fade control A video camera feature de- found on other instruments such as a color noise signed to provide fade-outs at the end of scenes meter, where it serves to stabilize input levels. and fade-ins at the openings. When the fade con- automatic hue control A signal inserted into the ver- trol is engaged during the middle of a scene, noth- tical blanking interval to help a TV set adjust the ing occurs until the end, when the fade-out ends proper color. Found on only a few TV models, auto- the scene. If the control is pressed before starting matic hue control, which is placed on line 18 of the the camera, the scene will open with a fade-in. Some blanking interval, may cause a problem when pre- cameras can be programmed to fade in and out on recorded tapes encoded with the anti-piracy code a scene. Macrovision are played. The anti-piracy signal uses automatic fine-tuning (AFT) control A circuit on such this same line for its white pulses that are placed units as VCRs and TV sets that keeps the frequency here to defeat copying the tape information to an- of the oscillator in the tuner correct for best color other VCR. Automatic hue control is similar in func- picture by compensating for drift and incorrect tun- tion to automatic color circuitry. ing. Eliminates the need for careful manual fine-tun- automatic image stabilization As applied to video ing each time a station is changed. cameras, a method of achieving a steady recorded automatic focus See Auto-focus. picture while the user is walking with the video cam-

18 automatic transition editing

era. Normally, the results of such camera recording automatic program delay A professional/industrial show up as images that are jumpy at best or unin- unit designed to provide delays from a few minutes telligible at worst. The use of servo mechanisms and to several days, play back multiple feeds simulta- rapidly responding compensating motors converts neously and accommodate incoming feed record- camera movement into relatively smooth pictures. only sessions. Delay actions are operated via time Modern video cameras do the stabilization electroni- codes, are frame-accurate and are affixed to the stu- cally by using only a portion of the CCD array to dio reference clock. Some units can handle a sched- capture the image. What portion of the CCD array ule of up to 1,000 events that can be programmed is used to capture the image is determined by the for automatic operation. amount and type of movement. All this is accom- automatic program edit A feature, found mainly on plished by activating a special switch on cameras top-of-the-line combination players, that equipped with automatic image stabilization. aids in the process of dubbing from disc to tape. automatic iris control A camcorder feature designed Once the user enters the length of tape selected for to automatically operate the lens opening by “read- recording, the player automatically calculates the ing” the average light within a scene. If the auto- number of tracks that can be recorded within that matic control cannot be overridden manually, then time range. there is no way to correct for extreme light or dark automatic programming A feature on VCRs designed backgrounds, etc. Some cameras are equipped with for presetting a number of programs on different auto/manual aperture control, a more desirable channels and at various times to record automatically. method, offering both flexibility and automation. automatic sag compensation Refers to a feature, automatic level control (ALC) When used to describe built into some test instruments such as color video an audio signal control, means the same as AGC. noise meters, that helps to produce uniform input automatic light control (ALC) In video, an electronic signals. circuit that modifies any incoming light to a prede- automatic scan tracking A feature, found on some termined level. In a vidicon camera, it is the control VCRs, designed to provide distortion-free slow mo- that automatically adjusts the target voltage to com- tion from freeze frame to play mode. See Visual scan. pensate for variations in light levels. The ALC af- automatic standard recognition (ASR) A circuit that fects light the way the AGC affects video. automatically selects the video standard of the re- automatic lock A DVD player feature that holds the ceived signal. When TV reception is difficult, because optical assembly in place when the power is shut the signals are weak, noisy, or badly distorted, this off. Similar to a “park” program for a computer disk feature can be turned off and the video transmis- drive, the automatic lock helps to prevent damage sion standard chosen manually. to the internal assembly whenever the machine has automatic switchover A feature that enables a de- to be moved. vice to accommodate either 110V or 220V opera- automatic pedestal control A process that automati- tion without any manual adjustment. cally adjusts the pedestal height in a received TV automatic timing See Programmable timer. signal as a function of input signal strength or some automatic tint control A circuit in color TVs to main- other specified parameter. tain the correct flesh tones. automatic phase control (APC) 1. A circuit in color automatic tracking A method of holding the video TV sets to reinsert a 3.58-MHz carrier signal with head of a VCR on the track during playback. Track- exactly the correct phase and frequency by synchro- ing adjustments are sometimes necessary to play nizing it with the transmitted color-burst signal. 2. back a tape recorded on a different machine. An automatic frequency-control circuit in which the automatic tracking reset A feature, found on some difference between two frequency sources is fed to older VCRs, that sets the tracking control to its de- a phase detector that produces the required control fault setting each time a videotape is ejected or when signal. the power is turned off. Without this feature, the automatic picture control A switch in some VCR owner must reset the tracking control manu- color TVs to disable one or more of the regular con- ally. Otherwise, the next recording will permanently trols and use corresponding preset varlues. Pushing be “off center,” a familiar problem with forgetful one button corrects for accidental misadjustment of VCR owners. Automatic tracking reset differs from controls. Sometimes also referred to as an automatic auto tracking, which works completely automati- gain control. cally, requiring no adjustments. automatic picture transmission (APT) A slow-scan automatic transition editing A process that permits TV system in weather satellites; it is capable of trans- glitch-free editing by automatically winding video- mitting conventional TV pictures of clouds in the tape back a few frames when recording is stopped. daytime and IR pictures of clouds in at night. Each When record is resumed, ATE aligns the beginning image is stored for about 200 seconds in a vidicon of the new recording with the end of the previous while being scanned for transmission to earth. one, thereby eliminating glitches and picture

19 automatic turn-on

breakup. The problem with some types of ATE is out using special glasses for the viewer. Large lenses that the last part of the previous scene is sometimes are employed and the viewer must be in a very spe- lost. Also, exact editing is almost impossible. JVC cific, fixed location to watch the 3D picture. It is not was one of the first manufacturers to offer this edit- compatible with normal TV programming. ing technique found today on many VCRs and por- autostereoscopic system A 3D-image display sys- table models. Other VCR manufacturers use differ- tem that doesn’t require special glasses. ent approaches, all of which achieve similar results— auto-stop circuit A circuit that puts a VCR into stop almost glitch-free edits. Sony, for example, intro- mode if any of the detectors that generate the auto- duced its time-phase circuit. When the tape restarts, stop operations sense a need to automatically stop its movement is delayed electronically by special cir- the machine. See Head drum rotation detector, Tape cuitry until the beginning of a field rather than the end sensor, and Tape slack sensor. middle of one. ATE is also known as edit-start, edit- autotiming The capability of some digital video equip- start control, scene transition stabilizing. ment to automatically adjust input video timing to automatic turn-on See auto cue and play. match a reference video input. Eliminates the need automatic variable frequency scanning A feature for manual timing adjustments. of display monitors that allows them receive a range auto-transition A transition (such as a mix or wipe) of signals that allows the user to switch from video that occurs without the use of a manual control, to . Some models can scan from such as a fader arm. Auto-transitions may be trig- 15 to 36 kHz while others offer more limited ranges gered from a button on the switcher, or externally such as 31.5 and 35 kHz. Several monitors designed in the case of an editor (such as via a GPI interface). exclusively for computers call this feature In a DVE or a “take” button (which may “multisync.” be remote controlled) will usually trigger a predefined automatic white balance A feature on camcorders transition. In this context, “take” is sometimes called to help simplify white balance control. By aiming “auto-transition.” the camera at a white card or similar object and auto-winder See Rewinder. pressing a button for a few seconds, a special circuit aux See Auxiliary . in the camera scrutinizes and compares the RGB auxiliary bus Some video mixers have extra switching channels and automatically corrects them. Some- buses that allow video signals connected to the times automatic white balance is only one, two, or switcher to be fed to external equipment such as three controls used on a camera for color adjust- digital effects systems, slow-motion VTRs, etc. The ment. Other cameras have improved the automatic auxiliary bus usually has no specific mixer function; white balance adjustment by allowing it to be put it is a utility feature. Syn.: aux. on hold. By preventing the adjustment from chang- auxiliary preset button A feature found on some ing automatically to match the shifting light condi- VCRs that is designed for setting in advance the tions, the camera user can capture the dramatic output channel of a decoder that may be required changes in such scenes as sunsets without the cam- for some cable TV systems. era compensating for these light changes. auxiliary radio services, CATV Three auxiliary radio auto-phasing A video mixer with auto-phasing has services, Multipoint Distribution Service (MDS), Mul- the ability to compensate for timing differences be- tichannel Multipoint Distribution Service (MMDS), tween the input sources, allowing it to perform tran- and Cable Television Relay Service (CARS), are used sitions free of artifacts. This is usually accomplished to supplement and broaden the coverage of CATV by built-in line or frame synchronizers. systems. auto-setup A type of professional/industrial TV moni- auxiliary trigger A video camera option that provides tor that adjusts itself automatically, thereby elimi- an additional pause button. It can be useful in cer- nating the fine tuning previously required by tech- tain situations such as shooting in awkward or un- nicians. These monitors are especially useful in view- usual positions. ing the same image when interchanging videotapes available light The amount of natural or artificial light from one facility to another. Another advantage is that is present. Light is measured in lux or footcandle the capture of the same image when several auto- numbers. The lower the number, the greater the setup monitors, adjusted for the same color tem- sensitivity of the camera. perature, are arranged in a row. average picture level (APL) The average level of the autosizing 1. Syn.: Character sizing. 2. In graphics luminance within an active picture. Usually expressed hardware, autosizing refers to a monitor’s ability to as a percentage of reference white level. APL is of- accept signals at one resolution and display the im- ten incorrectly used instead of “flat field.” age at a different resolution. Without autosizing, average transmitted power In TV transmitting sys- an image must be adjusted manually so that it fills tems, a power depending on the picture content, the screen properly. being minimum for an all-white picture and maxi- autostereogram A technique used for 3D TV with- mum for all black. The NTSC/PAL

20 azimuth technique

waveform is inefficient in its power use, and most produce can be placed next to each other, eliminat- of it is used for the sync and blanking pulses. See ing the guardbands or spaces previously required Rated transmitted power. between tracks. This permits storing more informa- AVI Audio-video interleaving. Microsoft® Video for tion on the tape. Sony first introduced the azimuth Windows file format for combining video and au- system in 1975. Some Super-VHS camcorders have dio into a single block in time, such as a video frame. a double-azimuth 4-head system that reduces the ASF is intended to replace AVI. size of noise bars during the search mode and pro- AVO Audiovisual object. In MPEG-4, audiovisual ob- vides noise-free still frames. 2. A compass bearing jects (also AV objects) are the individual media ob- expressed in degrees of rotation CW from true north. jects of a scene, such as video objects, images, and It is one of the two coordinates (azimuth and eleva- 3D objects. AVOs have a time dimension and a local tion) used to align a satellite antenna. coordinate system for manipulating the AVO. azimuth blanking Automatic blanking of a AVSS Abbreviation for Audio-Video Support System. transmitter beam as the antenna scans a predeter- A-weighted See Weighting noise. mined horizontal sector of its scanning region. This axis Relating to digital picture manipulation, the x axis may be used to prevent interference with TVs in a is a horizontal line across the center of the screen, city close to the search radar site. the y axis is a vertical line, and the z axis is perpen- azimuth-elevation (Az-El) mount An antenna mount dicular to plane of the x and y axes, indicating depth that tracks satellites by moving in two directions. and distance. The azimuth is the horizontal plane and elevation is axis of action See Line. up from the horizon. AYH option See HP 89400. azimuth error correction Electronic circuitry designed azimuth 1. The angle of the in rela- to help correct artifacts in prerecorded Dolby sur- tion to the tape path. To prevent crosstalk, or the round sound. It helps with such problems as dia- confusion of the video heads in playing back the logue, targeted for the front center channel, being proper tracks that are crowded together, the head directed to the rear speakers. gap angle is lifted slightly away from the perpen- This recording is used in VHS to dicular. In Beta format the tilt is 7 degrees. Thus, eliminate the interference, or crosstalk, picked up each of the two heads lays down a different pattern by a video head. Since adjacent video tracks touch, on the tape. It is as if one recording head placed a video head can pick up some information from down a horizontal design within its diagonal track the adjacent track. The azimuth of the head gaps while the second head recorded a vertical pattern. assure that head “A” only gives an output when When the tape is played back, each head can re- scanning across a track made by head “A.” Head trieve only the design or pattern it recorded, thereby “B,” therefore, only gives an output when scanning eliminating crosstalk. The azimuth system provides across a track made by head “B.” a second advantage. The tracks that the two heads azimuth technique See Azimuth recording.

21 B

b 1. Bit; for example, bps for bits per second. 2. Bi- back matching The matching of the input and out- nary; for example, 1101b for the binary number put of electronic devices to reduce signal reflection 1101. and . Also known as impedance matching. B 1. Blue. 2. CATV midband channel, 126-132 MHz. back plate The electrode to which the stored charge 3. See AAA rate. 4. Byte. 5. Baud. 6. Bel. 7. TV image of a camera tube is capacitively coupled. Syn.: standard; Australia, Austria, Denmark, , Fin- signal electrode. Used in vidicon, iconoscope. land, , , , , , Is- back porch The area of the analog video waveform rael, , , , , between the end of horizontal sync and the start of Norway, , , Rhodesia, , active video. In NTSC and PAL video signals, this part Singapore, , Sweden, Switzerland, , Yu- is largely occupied by the color burst. goslavia. Characteristics: 625 lines/frame, 50 fields/ back porch clamping The process of resetting video s, interlace—2:1, 25 fr/s, 15,625 lines/s, aspect ra- signal level offset to zero by using the black level at tio—4:3, video band—5 MHz, RF band—7 MHz, the back porch as a reference. Syn.: clamping; black visual polarity—negative, sound modulation—F3, level clamping. pre-emphasis—50 us, deviation 50 kHz, gamma of back porch switching Video signal switching per- picture signal—0.5, used band—VHF. formed within the vertical blanking interval to mini- B channel A “bearer” channel is a fundamental com- mize the visibility of switching artifacts. Syn.: vertical ponent of ISDN interfaces. It carriers 64,000 bits/s interval switching. in either direction, is circuit switched and should be back projection When the projection is placed be- able to carry either voice or data. Can be used for hind a screen (as it is in TV and various video videophone (see Common intermediate format). conferencing applications where the image is dis- B&W Black-and-white. played on a monitor or a fabric screen) it is described b/s Bits per second. as a back projection system. In these systems the B+ Supply voltage; the plus sign indicates the polarity. viewer sees the image via the transmission of light B+ boost A circuit in TV sets that adds to, or boosts, as opposed to reflection used in front projection sys- the basic B+ voltage. The boost source is a by-prod- tems. Audiences generally prefer back projection uct of the horizontal deflection system. See also systems since they seem brighter. Damper. back up In camcorders, an indicator on the menu dis- baby 750-watt spotlight. play. When the indicator appears, the settings are baby legs Low camera tripod. retained even when the battery is removed, as long back channel A means of communication from users as the lithium battery is in place. to content providers. As content providers are trans- back-back porch The portion of a back porch that mitting interactive television (analog or digital) to follows the color burst. users, users can also connect through a back chan- background 1. Short form of the term color back- nel to a Web site, for example. The back channel ground—the same as matte generator. 2. One of can be used to provide feedback, purchase goods the video sources involved in keying. Specifically, the and services, etc. A simple type of back channel is background video is the video that has parts of it an Internet connection using a modem. replaced with the key fill, or foreground video. When back light Light placed behind objects in a scene and associated with chroma-keying, for example in a pointing toward the camera to provide a rim of light, weather report, the background is the weather map that outlines the object and creates a sense of depth and the foreground is the weather reporter. by setting off that object from the rest of the scene. background color In videotex, the color of the area See Lighting. of the character cell not occupied by the foreground back lot An area of a movie studio or TV station where color; the color of the remaining area of the charac- exterior scenes are shot. ter. The color may be any from the available color

22 band

tables or be transparent, in which case the full-screen of the preceding segments also can be backtimed background color (or the cumulative result of all pic- from the end of the program working toward the ture elements previously set or the video picture) is beginning. seen. backward compatibility The capability of an improved background generator Usually part of vision mixer. or enhanced piece of hardware to accept software The color and sometimes even the texture of the designed for an earlier model. For instance, S-VHS generated background is adjusted with such con- VCRs, that require special tape to benefit from the trols as “Luminance,” ”Chrominance,” ”Hue,” etc. improved features of the VCR, can play back stan- Syn.: matte generator. dard videotapes. However, the conventionally re- background music jack An audio feature on some corded tapes will not reflect the higher quality of camcorders that permits the user to connect an ex- S-VHS VCR . See also Compatibility. ternal sound source during the recording process. Baer, Ralph Developed the first video games in 1971 Adding background sound while the original record- while he was employed by Magnavox. ing is in progress eliminates the usual generation Baird, John Logie Pioneer in British TV, inventor of the loss that is inherent in tape editing when music is first marketable home videodisc system in 1928. Us- recorded after a recording session. ing a TV system based on electro-mechanics (a light- background video See Background. sensitive cell and a mechanical revolving disc), he was backing The plastic-ribbon base, usually mylar, onto able to send a TV signal from London to New York in which is coated the oxide formulation of both au- 1928. The BBC employed his system when TV was dio and video tape. The backing is resistant to stretch- introduced into England in 1929. Within a few years ing and decomposition. A binder to hold a coating the process succumbed to an all-electronic TV sys- of magnetic oxide particles is placed on the back- tem developed in the USA by such scientists as ing. Backing is also called base film. Vladimir Zvorykin and T. Farnsworth. backlight switch On some video cameras with auto- balanced converter See Balun. matic iris control, a feature designed to provide one balanced modulator A modulator in which the car- f-stop more light. In a scene containing a bright rier and modulating signal are introduced in such a background with a dark subject, the automatic iris way that the output contains the two sidebands usually reads the darker part of the picture, causing without carrier. Used in color TV transmitters to ap- the main subject to be underexposed. Activating the ply the I and Q signals to the subcarriers, as well as backlight switch compensates for this by adding in suppressed-carrier communications transmitters. more light. Different from a contrast compensation balop Balopticon, an opaque projector made by Baush switch, the backlight switch only opens the lens and Lomb (hence the name) that casts positive im- wider. The backlight switch is sometimes listed as ages by reflection for a TV camera. The images gen- an automatic backlight compensator. erally are artwork on a large slide (a balop) used as backspace edit A feature on many VCRs whereby the background for a TV or film scene or as part of a tape will automatically rewind a certain number of sequence, such as a card or slide of a book jacket, frames to create a clean cut when the camera is product, name and address of a sponsor, or other reactivated. identification. backspacing 1. Reverse cueing technique. 2. A fea- balun BAlanced to UNbalanced. An adapter used for ture on VCRs designed to eliminate picture breakup converting 300 ohms into 75 ohms. Usually supplied between scenes by backing up the tape when the with a VCR to convert 300-ohm antenna wire, the Pause mode is engaged. Then when Record is balun is often needed to connect a video game, VCR pressed, the tape begins at the end of the previ- or other component to a TV set, etc. One example of ously recorded section. On some machines the tape its function involves connecting a 300-ohm video is backed up over the last few frames of the previ- game to a 75-ohm projection TV system. Also used ous scene. to balance the impedance of an outdoor antenna backtiming 1. Reverse cueing technique for editing (usually 300 ohms) to the impedance of modern TV backspace used in electronic editing. 2. A technique sets and VCRs (usually 75 ohms). There are two types in live news, variety, or other programs in which the of baluns: a VHF-only and UHF/VHF model. Some- last segment is rehearsed and timed. Thus, in the times called balanced converter, bazooka (slang), line- actual broadcast, as the time to begin this segment balance converter, and matching transformer. approaches, the director is prepared to stretch it, balun coil A set of balun coils are found between speed it up, or replace it. In TV news programs, antenna connection and TV tuner to match the in- backtime is the clock time (the actual time) at which put of 300 ohms to 75 ohms at the tuner input. the last segment should begin if the program is to banana tube A type of color picture tube in which end on time. Thus, if the last segment is 40 s long television signals were sent through a long, thin tube, and the newscast must end at 11:28:55, the last followed by RGB signals flashed at timed intervals. segment must begin at its backtime, 11:28:15. Each band In audio/video, a span or range of frequency

23 band separator

signals. Most TV sets and VCRs can be adjusted for bandwidth Say you want two 56-Kbps any one of three ranges: L (low band) for VHF chan- circuits right now for a videoconference. Use one of nels 2-6; H (high band) for VHF channels 7-13, mid- the newer pieces of equipment band A-I and superband J-W; and U for UHF channels and “dial up” the bandwidth you need. An example 14-83. However, more sophisticated machines of- of such a piece of equipment is an inverse multi- fer four ranges: VHF low (channels 2-6), VHF mid- plexer. Uses for bandwidth on demand include video high (channels 7-13 and cable A-I), UHF (14-83) and conferencing, LAN interconnection and disaster re- VHF super (for superband channels on cable). TV covery. Bandwidth on demand is typically only for satellites work within two frequency ranges. Large digital circuits and it’s typically carved out via a T-1 dish antennas require the popular C-band, whereas permanently connected from a customer’s premises smaller dish antennas utilize the Ku-band. to a long distance carrier’s central office, also called band separator An accessory that separates incom- a POP—Point of Presence. ing UHF, VHF and AM antenna signals so that they bandwidth reduction, EUREKA-95 HDMAC system can be directed to their respective terminals. Some To transmit the 21-MHz luminance baseband com- band separators accept a 300-ohm (twin lead) in- patibly to the D-MAC and D2-MAC receivers, band- put while others take a 75-ohm input and, with a width reduction by a factor of approximately four is built-in matching transformer (75 to 300 ohms), pro- required. This is accomplished by the coding and vide a VHF output as well as a UHF output. Band decoding process as follows. The encoder has separator is essentially a set of filters. “branches” for three degrees of motion: an 80-ms band switch See Turret tuner. (4 fields) branch for stationary and slowly moving banding A video defect in TV transmission in which areas of the scene; a 40-ms (2 fields) branch for strips of the picture differ from adjacent areas, of- moving areas; and a 20-ms (1 field) branch for rapid ten due to a videotape player. motion and sudden scene changes. These branches bandpass filter A circuit that transmits alternating are switched to the transmission channel by the currents whose frequencies are between given up- motion processor. The switching signals are also per and lower cutoff values, while substantially at- transmitted to the receiver via DATV channel, where tenuating all frequencies outside this band. Used in the branch in use at a particular time, after decod- TVs, VCRs. These filters are also used in signal pro- ing, is connected to the receiver for processing and cessors to affect color and definition to allow only a display at the 1250/50/2:1/16:9 rates of the camera selected range of frequencies to pass through. or equipment at the transmitter. band-stop filter A filter that attenuates alternating The chrominance signals, each of 10.5 MHz base- currents whose frequencies are between given up- band, are transmitted after similar 3-branch encod- per and lower cutoff values while transmitting fre- ing, but without . The encoding quencies above and below this band. It is the in the 80-ms branch extends over four fields. Hence, opposite of a bandpass. The band rejected is gener- the luminance bandwidth for stationary areas is re- ally much wider than that suppressed by a trap. Also duced from 21 MHz to 5.25 MHz. But the 40-ms and called band-rejection filter, bandstop filter, and 20-ms branches extend only over two fields and one rejector circuit. field, respectively, so additional bandwidth reduction bandwidth (BW) 1. Refers to the frequency range is required. This is achieved by several processes, e.g., transmitted by an analog system. In video systems, “quincunx” scanning (scanning of successive picture specifying the highest frequency value is sufficient, elements alternately from two adjacent lines) on al- since all video systems must transmit frequencies ternate fields, which produces a synthetic interlace; down to 30 Hz or lower. In transmission, the U.S. and line shuffling that interleaves high-definition analog and digital SDTV channel width is 6 MHz. 2. samples so that two lines within a field are transmit- Incorrectly used as the equivalent of information- ted as one MAC/packet line, to which the D-MAC carrying capability of digital TV systems, e.g. “the and D2-MAC receivers respond compatibly. The clues compression system has a 6-MHz bandwidth.” The required to perform the inverse operations at the re- particular artifacts generated by such systems may ceiver are transmitted over the DATV channel. make nonsense of the quoted frequency bandwidth requirements The bandwidth required response. by a TV signal is half the number of pixels transmit- bandwidth compression A technique to reduce the ted per second. A wide bandwidth is required to bandwidth needed to transmit a given amount of resolve fine detail while maintaining a high enough information. Bandwidth compression is used to picture repetition rate to avoid objectionable flicker. transmit voice, video and data. This explains the huge spectrum requirements of TV bandwidth efficiency In TV, the ratio of picture qual- systems. ity to RF bandwidth. Bandwidth Segmented Orthogonal Frequency bandwidth, HDTV (color set and color-difference set). Division BST-OFDM attempts to im- See SMPTE 240 standard. prove on COFDM by modulating some OFDM car-

24 baseband

riers differently from others within the same multi- Barkhausen A term applied to a display of one or two . A given transmission channel may therefore black vertical lines on the left side of the TV picture be “segmented,” with different segments tube due to some spurious behavior (oscillation) in being modulated differently. the circuit. These lines are usually seen best when bank 1. A set of similar devices connected together there is no picture on the screen (just a blank raster). for use as a single device (bank of ). 2. A Barkhausen magnet A permanent magnet mounted storage area (data bank). 3. In film and TV, rows of on the horizontal output tube of a TV receiver to lighting. 4. In broadcasting, a pool or collection of reduce Barkhausen oscillations. commercials (commercial bank). Barkhausen oscillation An undesired oscillation in bank timer A VCR timer-related feature that can store the horizontal output tube of a TV receiver; it causes several sets of timer-recording instructions under one or more ragged dark vertical lines on the left different categories. On-screen menus help the side of the picture. viewer to code in timing information under such barn doors Adjustable flaps that fit over a video light topics as news, cinema, cartoons and drama. These to concentrate the beam in a broad or narrow path. instructions are then entered into the timer section Also called flippers. for upcoming recordings. barracuda British TV and film slang for a telescopic bar A common test pattern component. The bar looks light support, made from lengths of metal pole. on a TV screen as a vertical strip, usually specified by barrel distortion 1. The characteristic distortion of a color, level and edge rise-time, e.g. 75% 2T White scene by a wide-angle lens: a rounded and out-of- Bar. Sometimes the bar component is called “- proportion look around the edges of the scene, dows” or ”box.” caused by objects being too close to the lens. 2. bar code A pattern of vertical lines of differing widths. Distortion in which all four sides of a received TV These can be read by a bar-code scanner to provide picture bulge outward, like a barrel. See Distortion. data to a VCR . See also LCD digital scanner pro- barrel effect Vertical edge distortion of a screen im- gramming system. age. The effect tends to be more pronounced in rear bar code programming A VCR feature that simpli- projection TV systems. fies transmitting recording instructions to the clock/ barrier display section In (2+3)D-image display sys- timer of the VCR. VCRs that come equipped with tem with parallax barriers, a section in which the this programming function provide a pen-like de- number of parallax barriers, width aperture ratio, vice, called a bar-code scanner, and a programming shape including the interval, and generating posi- card containing a list of days, time segments and tion can be freely programmably controlled in channel numbers. The owner, using the scanner, sim- accordance with an instructed input. ply checks off the appropriate day, time and chan- barrifocal mirror system One of the 3D-image dis- nel on the card for each program to be recorded. play systems that doesn’t require special glasses. The information is then transferred to the VCR to bars and red Popular two-part test pattern with stan- be displayed for confirmation on the TV screen. dard color bars above red field. Useful for the de- bar generator A that delivers pulses tection of noise and moire. Professional jargon uniformly spaced in time and synchronized to pro- sometimes refers to this signal as “Bars in Blood”! duce a stationary bar pattern on a TV screen. A color- Syn.: split field/red. bar generator produces these bars in different colors base The part of an electron tube that has the pins, on the screen of a color TV set. leads, or other terminals to which external connec- bar pattern The pattern of repeating color bars pro- tions are made either directly or through a socket. duced by a bar generator, for adjusting color TV base film Backing. receivers. base light The general illumination of an area. The barrier grid See stabilizing mesh. base light helps provide the camcorder with a light- bar tilt Time domain parameter indirectly showing low- ing level above that which is needed to prevent elec- frequency response distortion by checking bar wave- tronic noise. All video units, such as VCRs and form. The tilt of the flat top of the bar is usually cameras, produce video noise that affects the video expressed as a percentage of the bar’s amplitude, signal. The base light, which is usually located over ignoring overshoots. Syn.: tilt. the subject, helps to overcome this. bar-code scanner An optical character reader that baseband 1. The band of frequencies containing the can automatically read data from documents bear- information, prior to modulation (and subsequent ing information formed with a special bar code. See to demodulation). The band that transmits picture also LCD digital scanner programming system. and synchronizing signals in TV; the band contain- barker audio See Video inversion. ing all the modulated subcarriers in a carrier system. barker channel A channel to advertise the pay TV When applied to audio and video, baseband means service to nonpaying would-be viewers. The main an audio or video signal that is not RF modulated audio channel can be used as a barker channel. (to channel 3 or 4 for example). 2. In satellite TV,

25 baseband signaling

the raw audio and video signals prior to modulation cludes all elements transmitted including coordina- and broadcasting. Most satellite headend equipment tion elements, the baud rate is not necessarily equiva- utilizes baseband inputs. More exactly, the compos- lent to the data rate, and baud is not necessarily ite unclamped, non-de-emphasized and unfiltered synonymous with bits/s. receiver output. This signal contains the complete bazooka Slang for a large item. Slang term for balun. set of FM modulated audio and data subcarriers. BB 1. Black burst. 2. CATV hyperband channel, 306- baseband signaling The transmission of a digital sig- 312 MHz. See TV channel assignments. nal without modulation. Only one signal at a time BBC [color] bars Color bars with the nomenclature can be present on a baseband channel. 100/0/100/25 in 625/50/2:1 scanning standard. baseband transmission A type of data transmission BBC standard The British Broadcasting Company in in which each medium carries only one signal, or London began transmissions in 1929, but their first channel, at a time. service was more or less experimental even though baseband video Same as composite video (CVS or the public was “invited” to buy receivers. It was an CVBS). electromechanical system with a picture resolution baseline sequential JPEG The most popular of the of 30 lines and a field rate of 25 Hz. Then, in 1936, JPEG modes that employs the lossy DCT (Discrete an all-electronic system was adopted and the stan- Cosine Transform) to compress image data as well as dard was set at 405 lines/50 Hz, which has remained lossless processes based on variations of DPCM (Dif- in effect since then as the standard for VHF black ferential Pulse Code Modulation). The “baseline” sys- and white TV in England. tem represents a minimum capability that must be BCU A big close-up of a picture in photography, film, present in all Sequential JPEG decoder systems. In this or TV; ECU is an extreme close-up. mode, image components are compressed either in- BDC Block Downconversion. dividually or in groups. A single scan pass completely beam 1. A semi-coherent of electrons. 2. A nar- codes a component or group of components. row stream of essentially unidirectional electromag- basic cable A term referring to the minimum services netic radiation (as in a ) or charged a U.S. subscriber of a CATV system gets for the mini- particles (as in an electron beam). mum monthly charge. These services usually include beam adjustment A control on vidicon cameras that VHF and UHF channels, CNN, religious and weather regulates the amount of current flowing in the beam. channels and other programming nationally distrib- beam angle See Cathode-ray tube. uted. Other services, like HBO, require additional beam bender Ion-trap magnet. See Ion trap. monthly fees. beam bending Deflection of the scanning beam by basic rate interface (BRI) There are two “interfaces” the electrostatic field of the charges stored on the in ISDN: BRI and PRI. In BRI, you get two bearer B- target of a camera tube. channels at 64 kilobits/s and a data D-channel at 16 beam blanking Blanking. kilobits/s. The bearer B-channels are designed for beam convergence The adjustment that makes the PCM voice, video conferencing, group four facsimile three electron beams of a 3-gun color picture tube machines, or whatever you can squeeze into 64,000 meet or cross at a shadow-mask hole. bits/s full duplex. The data D-channel is for bringing beam current The current of a scanning beam in in information about incoming calls and taking out camera or TV CRTs. information about outgoing calls. It is also for ac- A color picture tube with a cess to slow-speed data networks, like videotex, single electron gun and in which the screen is com- packet switched networks, etc. One BRI standard is posed of horizontal stripes of red, green and blue the “U” interface, which uses two . Another phosphors arranged in sequence. A grid of horizon- BRI standard is the “T” interface, using four wires. tal wires is mounted close to the screen and, by ap- basic set A film, TV, or stage set with furniture and plying suitable potentials to these wires the electron scenery but without props. beam can be deflected so as to strike the phosphor basic television service A charge for delivery of TV stripe giving the required color. Also called beam- broadcast by cable; typically a monthly fee for the switching tube. lowest level of service. beam indexing Refers to a signal generated by an basket Cassette lift mechanism in front-loading VCRs. electron beam that is deflected and fed back to a Also called elevator. control device. Beam indexing is one of several meth- bat blacks In video, to fade out; to turn a picture to ods of presenting images upon a screen. darkness or superimpose over a picture. beam landing errors Errors that can occur when the battery See Lead acid battery, Nickel cadmium electron beam does not strike the target correctly, battery. owing to distortions of the magnetic fields. This may baud (B) A unit used to measure the number of times/ happen in cameras and TV CRTs in areas where two s that a data transmission channel changes state. fields interact, such as line and frame deflecting Since, even in a binary channel, the baud rate in- fields.

26 -SX beam magnet Convergence magnet. petitor, the VHS format. Although the originator of beam splitting Method of dividing the color compo- home VCR, Beta has almost completely disappeared nents of the image so they can be cast upon more in the U.S. Other companies, including Zenith, than one vidicon target area (or tube); used in 2-, 3- Toshiba, Marantz and Sanyo, had originally selected and 4-tube color cameras. the Beta format for their VCRs and video cameras, beam-indexing tube A color TV picture tube with a but have since abandoned that format in favor of single electron gun and in which the screen is com- the more successful VHS. posed of vertical stripes of red, green and blue phos- Beta hi-fi A full-frequency stereo process for VCRs phors arranged in sequence. A beam indexing system developed by Sony in 1982. Conventional video ste- operated, e.g., by signals from vertical stripes inter- reo as found on VHS machines uses longitudinal leaved with the red, green and blue groups ensures sound tracks (tape passing across a stationary head), that at any instant the electron gun is always but this method produces poor sound quality be- switched to the phosphor stripe on which the beam cause of two factors. The tape speed of video ma- is incident. chines is very slow, only a fraction of that of audio beam-splitting systems Devices for splitting a light recorders. Secondly, the small space of the tape al- beam to form two or more separate images from a lotted to the normal mono audio track has to be single lens. Often used in color TV cameras to form split in half to provide for the dual channels neces- the three primary color images. Beam-splitting can sary for stereo. For these reasons, a noise reduction be accomplished by prisms, semi-reflecting surfaces system such as Dolby B is required to improve some and dichroic mirrors. of the less-than-adequate sound. Sony avoided these beam-switching tube Beam deflection tube. two shortcomings by using the video heads to place beamwidth The acceptance angle of an antenna, usu- the FM-modulated audio (AFM — Audio FM) sig- ally measured between half-power (3 dB) points. nals onto the tape, superimposing the channels over bearding A video distortion appearing as short black the video signal. A greater dynamic range results, lines to the right of bright objects. It’s caused by with a frequency response said to be from approxi- interruptions in the horizontal sync of the tape. mately 20-20,000 Hz. The portion of the tape oth- Beck, Stephen Video artist, electronic engineer. Work- erwise assigned to the audio signal can still be used ing with a video synthesizer, he originated the con- for a mono sound track (to keep the system com- cept of combining color, form, texture and motion patible with other Beta machines). It can also be used to produce abstract kinetic video art. His works are as a third audio track for different functions, such recognized worldwide. In the early 1970s he worked as recording a foreign language. on a PBS series called “Video Visionaries.” Betacam Sony’s trade name for component analog beeper feedback See Audio alarm, Trigger alarm. tape recording format. The term is often incorrectly bel Symbol: B. A relative measurement, equal to the associated with component analog video interfac- logarithm to the base 10 of the ratio of two amounts ing in general. The system has continued to be de- of power. One power value is a reference value. The veloped over the years, offering models for the decibel, a smaller unit equal to 1/10 B, is more com- professional/industrial markets. Digital versions also monly used. exist as the high-end Digital Betacam and Betacam bell filter Filter in a SECAM decoder to de-empha- SX for ENG and similar applications. size the chrominance signal prior to frequency de- Betacam color bars Historically these bars followed modulation. early Betacam signal levels, giving rise to 75% color bells and whistles Special effects, flashy graphics, bars in YPrPb format with PrPb gain boosted by a and other extras added to films, TV programs, or factor 1.333. At the righthand side of the pattern, any audiovisual presentation. the “black set” test and 100% white bar are added. below the line Technical and production costs as in- In the 625 version the white level is 700 mV, in the dicated in the program budget—includes produc- 525 version the white level is 100 IRE (714.825 mV). tion equipment and technical personnel. Betacam SP The Sony trademarked “Superior Perfor- BER (or B.E.R.) Bit Error Rate. Accuracy of digital de- mance” analog component video tape recording modulation or decoding. Analogous to SNR, but re- format similar to the Betacam format. Betacam SP fers to digital transmission. players will play back Betacam recordings but not best time available (BTA) An instruction with a pur- vice-versa. Betacam SP is recorded on oxide or metal chase order for a TV or radio station to broadcast a tape. commercial at the most favorable time available. Betacam-SX Sony’s trademark for a component digi- Beta format A system of home videotaping using a tal tape recording format with signal compression. special 2-hub plastic videocassette, 1/2-inch tape and Developed for news acquisition. Compression is simi- recording speeds incompatible with other formats. lar to MPEG-2, but with fixed GOP structure to al- Introduced for home use in 1975 by Sony, the Beta low easier edits. The digital signal recorded on tape format uses a cassette smaller than that of its com- uses a higher level of digital compression (DCT-based)

27 Betamax

than Digital Betacam, which results in a lower bit- grams are sent to a station or cable system when rate after coding. At the interface level it is compat- they are needed for the station’s schedule. After a ible with D-1 format, i.e. conforms to ITU-R BT.656. program is broadcast, that station or system sends Betacam-SX players can play back analog compo- it on to the next operation. nent Betacam SP tapes. bidirectional Describes a microphone that accepts Betamax Sony’s trade name for its initially popular sound waves from two different directions, while 1/2-inch Beta format VCR. The first Betamax, the attenuating sound waves from any other direction. SL-7200, was introduced in 1975. The Betamax has bifilar transformer A transformer in which wires for virtually disappeared in the U.S., losing marketshare the two windings are wound side by side to give to the VHS format. extremely tight coupling. When used as TV IF trans- Betascan Sony-developed feature found on Beta VCRs formers to couple stagger-tuned IF stages, the high that allows for quick picture search (15x, Beta III). coupling eliminates the need for a DC blocking Betaskipscan Sony Betamax feature that provides in- capacitor. stant switching from high-speed FF or REW mode BIFS Binary format for scenes. In MPEG-4, a set of to Betascan search mode to determine location on elements called nodes that describe the layout of a the tape. multimedia layout. BIFS-Update streams update the bezel In video, the frame surrounding a video picture scene in time, BIFS-Anim streams animate the stream that has different proportions from that of the TV in time. BIFS are organized in a tree-lined hierarchi- screen. For example, when some cable or broadcast cal scene graph structure derived from VRML. stations present a wide-screen theatrical film in its Bildschirmtext (Btx, BTX) Now called Datex-J. The correct aspect ratio (about 16:9), the top and bot- public videotex system in the Federal Republic of tom portions of the screen (4:3 aspect ratio) remain Germany. blank. Some local and network stations provide a billy- A prefix denoting one thousand million, synony- decorative bezel to replace the normally black por- mous with “giga.” tions of the screen. Bezels may come in different binary gradation A gradation of black and white. proportions. binary pair Synonymous with bistable circuit. BF Burst flag. binary variable A variable that can have one of two B frames Bi-directional predictive frames used by values (0 or 1). Also known as two-valued variable. MPEG. These are composed by assessing the differ- binary-coded character A character represented by ence between the previous and the next frames in a a binary code. television picture sequence. As they contain only pre- binder A chemical adhesive to hold the magnetic ox- dictive information, they do not make up a com- ide particles to the backing or base of the video- plete picture and so have the advantage of taking tape. The quality of the binder is important in that up much less data than the I frames. However, to its composition determines the number of dropouts see the original picture requires a whole sequence that are likely to occur. of MPEG pictures to be decoded. See MPEG. bipolar PG In VCRs, pulse generator signals that have BG Burst flag. both positive and negative excursions. bias light Internal illumination of a TV camera tube bipolar sync See Tri-level sync. that reduces or removes the halo (reflected light that bird Jargon or nickname for communications satellites. extends beyond the desired boundaries). birdseye In film and TV, a spotlight with a reflector biased automatic gain control Syn.: delayed AGC. back invented by Clarence Birdseye (1886-1956), It is a process that comes into operation only for who is better known for developing methods for signals above a predetermined level. quick-freezing foods. bible In the production of a TV series, the general out- B-ISDN Broadband ISDN. See ISDN. line of plots and character development prepared bistable Having two states. before the first program of the season. Some pro- bistable circuit A circuit that can be triggered to adopt ducers refuse to bible the show, in order to main- one of two stable states. Also known as binary pair, tain the flexibility to make plot and cast changes bistable trigger circuit, trigger pair. during the season. bistable trigger circuit Syn.: bistable circuit. biconcave A lens configuration in which the lens ele- bit A single binary information unit. Usually represented ment has an inward curve on both sides. by “0” or ”1.” As a jargon term can be used to biconvex A lens configuration in which the lens ele- describe a single step of the quantization scale. ment has an outward curve on both sides. A magni- bit assignment In video compression, the process of fying glass is the most common example of a creating the compressed data bit stream from the biconvex lens. raw output of the compression algorithm. bicycling The shipment of videotape recordings of TV bit bucket Any device able to store digital data— programs from one transmitting entity to another. whether it be video, audio or other types of data. In order to save film and videotape costs, the pro- bit budget The total number of bits available on the

28 black burst

media being used. In DVD, the bit budget of a single- structure that contains the parameters of a bitmap sided/single-layer DVD5 disk is 4.7 GB. including its location in memory, its dimensions, and bit depth The number of levels that a pixel might have, its pixel format. such as 256 with an 8-bit depth or 1,024 with a bitmap font A special format of a text font that con- 10-bit depth. tains pixel values for each text character. bitmap A digital representation of an image in which bitmapping A technique used in graphics display in the bit-mapped characters, composed of dots or which the information displayed on a screen corre- pixels, are readable on a screen. sponds, pixel by pixel, with bits held in memory. bit parallel format See Parallel digital [video] inter- bits per pixel (bpp) The number of bits used to repre- face format. sent the color value of each pixel in a digitized bit pattern A sequence of bits. Bit patterns may be image. used to represent characters in a binary code. bits per second The number of bits transmitted per bit plane In digital video, with display hardware that second over a communications line. has more than one video memory array contribut- BK Black. ing to the displayed image in real time, each memory BL Black; also blue, depending on the context, so when array is called an image plane. However, if the ar- in doubt, spell it out. rays have only one bit-per-pixel, they may be called blab-off-switch British slang for a remote-control de- bit planes. vice to mute the sound of a TV program, such as bit rate Relating to the speed of a device, e.g., the during the commercials. speed with which binary digits can be transferred black Very dark. Pitch black or pure black means to- over a communications channel. May be measured tally without light. Television black reflects a very in bits/s or baud. It is the digital equivalent of band- small amount of light from the screen, about 3% width. reflectance. bit rate conversion See Sampling rate conversion. black after white A TV receiver defect in which an bit serial format Format where 10-bit serialized video unnatural black line follows the right-hand contour data are transmitted via BNC type connector or fiber- of any white object on the picture screen. The same optical connector with clock rate: 10 x 4 x 3.579 = defect also causes a white line to follow a sudden 143 MHz (digital composite NTSC and PAL-M), 10 x change from black to a lighter background. It is 4 x 4.433 = 177 MHz (digital composite PAL), 10 x 27 caused by receiver misalignment. = 270 MHz (digital component 4:2:2) or 10 x 36 = black and white signal 1. A signal wave that con- 360 MHz (ITU-R BT.601, digital component). Syn.: trols luminance values in black and white TV. 2. The Serial Digital [Video] Interface. portion of a signal wave that has major control of bit stream A serial sequence of bits. the luminance values in a color TV system, regard- BitBlt Abbreviation for bit boundary block transfer, a less of whether the picture is displayed in color or in data transfer function that moves a rectangular re- black and white. gion of pixels within or between bitmaps. This func- black and white television Television that reproduces tion often is used for displaying pop-up windows, a picture in black and white (b&w) with shades of cursors, and small symbols such as text. BitBlt tradi- gray between black and white. Black and white re- tionally is capable of performing a Boolean (e.g., ceivers use the brightness information transmitted XOR) operation between the source and destina- as part of the color signal—the luminance signal— tion during the transfer. Also called RasterOp. but the image is produced in black and white. BITC Burned-In Time Code. This means the time code black and white transmission Transmission of a sig- information is displayed within a portion of the pic- nal wave that controls the luminance values in a TV ture, and may be viewed on any monitor or TV. picture but not the chromaticity values. The result is bite A short segment, or take, that is repeated on net- a black and white picture. work radio and TV news programs. black body A perfect absorber of all incident radiant bitmap A region of memory or storage that contains energy. It radiates energy solely as a function of its the pixels representing an image arranged in the temperature. sequence in which they are normally scanned to dis- black body radiator See Full radiator. play the image. If a bitmap can be directly displayed black box 1. An electronic device with known perfor- on the screen, it is referred to as a frame buffer. If mance characteristics but unknown constituents. 2. the bitmap cannot be viewed directly, then its data A general term given to a variety of electronic devices must be moved to display memory to be viewed. because of their color and shape. They include image For example, a text font can be stored in an off- enhancers, image stabilizers, video amps and up con- screen bitmap, and each character is moved to the verters that can be connected to a VCR or a TV set. proper place on the screen (using BitBlt) as it is black burst (BB) A video signal that contains the color needed. black. This gives the signal the major reference points bitmap descriptor In the DVI runtime software, a data of color-burst pulse, a black reference, and sync. It is

29 black-burst generator

used as a base “neutral” signal to format tape and to referred to as blacker-than-black. You could say that reference most video hardware. Black burst tells the sync is blacker-than-black. video equipment the vertical sync, horizontal sync, black level clamp Circuit that establishes the signal and the chroma burst timing. Syn.: house sync. level corresponding to black at a finite level. Neces- black-burst generator See black burst. sary after AC coupling to restore the DC compo- black clipper See Black limiter. nent in the TV signal, and to eliminate low-frequency black clipping A video control circuit that regulates distortion and hum. The signal is fed through a ca- and contains the black level of the video signal so pacitor and shorted to a fixed direct voltage during that it does not disturb or appear in the sync por- line blanking intervals. Used also in line clamp am- tion of the signal. plifiers. black compression A reduction in TV picture-signal black level clamping The process of resetting video gain at levels corresponding to dark areas in a pic- signal level offset to zero by using the black level at ture. The effect reduces contrast in the dark areas the video back porch as a reference. Syn.: back porch of the picture as seen on monitors and receivers. clamping; clamping. Also called black saturation. black level control A feature on some TV sets that black crushing Compression of low values of signal controls the extent of black within picture areas. This (i.e., black) resulting in loss of significant detail in may affect the contrast of the image, but it is not the darker picture areas. strictly a contrast control; it does not determine black current stabilizer An adjustment on each CRT which portions of the image should turn black but gun (R, G, B) for setting the leakage current when rather the degree of blackness. The conventional the gun is in the vertical blanking interval. If not contrast control, on the other hand, constricts or adjusted there will be background discoloring. The extends the range of contrast only. On broadcast- leakage is measured via sensing resistors in the CRT studio quality video cameras the black level control cathode circuits. feature is called “pedestal” while the contrast con- Black Entertainment TV A CATV channel targeted trol is known as gain. for a black audience and offering entertainment, black level noise Very similar to a white spot noise sports and films. BET also covers interviews and other spike except it is in the opposite or black level direc- news pertaining chiefly to its black audience. tion. blacker-than-black 1. Excursion of the TV video black level retention The ability of a TV set, VCR or waveform signal downwards below the nominal similar unit to reproduce black areas on a TV screen. black level; e.g., the excursion of the synchroniz- Although no TV receiver produces an absolute black, ing pulses to zero signal. 2. The amplitude area of manufacturers have constantly experimented in this the composite video signal below the reference area to improve the overall image contrast. The range black level in the direction of the synchronizing of color contrasts depends on the span between the pulses (e.g., the luminance signal overshoots after darkest gray and purest white. The wider the range, a white-to-black transition). ITU-R BT.601 quanti- the more noticeable the distinctions between hues. zation scale provides 15 levels of headroom below This variation in shades helps to give the appearance reference black to allow some blacker-than-black of depth or three dimensions to the image on the TV throughput. screen. The contributions over the years of several blacker-than-black region The portion of the stan- companies, including NEC, Proton, Zenith, Sony and dard TV signal in which the electron beam of the , have resulted in subtle improvements in picture tube is cut off and synchronizing signals are black level retention. These enhancements are more transmitted. These synchronizing signals have greater prominent in the higher-priced TV monitor/receivers peak power than those for the blackest portions of than in low-end TV sets. Black level retention is mea- the picture. sured by percentage; e.g., 80% or better is rated sat- black filter A filter, used in devices for direct display of isfactory while 90% is considered good. an image on the of the eye using a scanning black limiter A device preventing a video signal being laser, that attenuates the intensity of the incident lower than some pre-set threshold near black level. laser beam to such a level that laser beam will not be Syn.: black clipper. harmful to an eye into which it is introduced. black matrix Picture tube in which the color phos- black level The bottom level of the picture signal, be- phors are surrounded by black for increased low which are the sync, blanking, and other control contrast. signals that do not appear as picture information. black matrix lenticular screen See Black stripe pro- This level is generally set at 75% of the maximum jection television. signal amplitude of the synchronizing pulses and black matrix/black surround A technique to reduce represents the darkest an image can get. It defines the unexcited field brightness and the light reflected what black is for the particular video system. If for by the phosphors of color . The results some reason the video dips below this level, it is can be seen by observing the of a color

30 bleed through

receiver of recent design when the set is turned off. blank To cut off the electron beam of a CRT. In contrast with older sets in which the kinescope blanked picture signal The signal resulting from was whitish gray, new sets appear black. blanking a TV picture signal. black negative A TV picture signal in which the volt- blanking Suppression. Process of the cutting off of age corresponding to black is negative with respect the electron beam of a TV picture tube, or camera to the voltage corresponding to the white areas of tube, or during retrace by applying a rectangular the picture. pulse voltage to the grid or cathode during each blackout A suppression or stoppage, such as a news retrace interval. On the screen, the scan line moves blackout. In sports TV, the suppression of coverage from the left edge to the right edge, jumps back to in a particular area because of contractual agree- the left edge, and starts out all over again, on down ments with the home team of the league. the screen. When the scan line hits the right-hand black-out A temporary loss of sensitivity of any elec- limit and is about to be brought back to the left- tronic device following the passage of an intense hand edge, the video signal is blanked so that you transient signal. can’t “see” the return path of the scan beam from black-out point Cut-off. the right to the left-hand edge. To blank the video black peak A peak excursion of the TV picture signal signal, the video level is brought down to the blank- in the black direction. ing level, which may or may not be the black level if black positive A TV picture signal in which the volt- a pedestal is used. There are usually two blanking age corresponding to black is positive with respect components to eliminate the horizontal and vertical to the voltage corresponding to the white areas of components of the return trace. Also called beam the picture. blanking. The opposite action is called gating. black saturation Black compression. blanking and muting circuit The VCR is permanently black set [test] [pattern] Same as pluge, but for black video-blanked and audio-muted in all modes, ex- level only. cept play, record, and the mode known as “E-E,” black stretch Nonlinearity applied to the TV signal so that stands for electronics-to-electronics. The E-E that the part toward black is increased in amplitude mode allows the operator to view the picture that is relative to the rest of the signal. The effect is to make to be recorded. detail in the black more visible, and correct the crush- The level that separates picture infor- ing caused by the nonlinear toe of the typical transfer mation from synchronizing information in a com- curve. As in film technique, a slightly higher contrast posite TV picture signal. It coincides with the level than is theoretically desirable often improves the picture. of the base of the synchronizing pulses. This could black stripe The process of prerecording a video tape be the black level if a pedestal is not used or below with no input signal in order to lay down a uniform the black level if a pedestal is used. sync signal over the length of the tape. Black-strip- blanking pulse level The reference level for video ing makes it easier to hide editing glitches because signals. The blanking pulses must be aligned at the blank spots in the video program simply appear black input to the picture tube. rather than full of visual static. Video production stu- blanking signal A wave of recurrent pulses, related dios use a special video signal for this purpose, in time to the scanning process, to effect blanking known as black burst. Studio black burst ensures in TV. The pulses occur at both the line and field that all the video tape produced at the studio is black- frequencies and cut off the electron beam during striped with the same video frequency because ev- retrace at both transmitter and receiver. ery tape is black-striped with a black burst from the Blay, Andre Founder and originator of the home video same source. Amateur videographers can accom- prerecorded videocassette industry. In 1977 he pur- plish this same task by placing a lens cap over a video chased the rights to a package of 20th Century Fox camera and recording an entire tape. films for the purpose of home video sales. Included black stripe projection television Refers to a pro- in the 50 features were such classics as “The Grapes cess designed to increase the contrast of a picture of Wrath.” Blay’s company, Magnetic Video, trans- in a projection TV system. It was introduced by ferred the films to Beta and VHS formats and retailed Sylvania and later incorporated by Magnavox into them for $50 to $60 each, thereby introducing the its large-screen TV sets. The black stripe projection first prerecorded programs for the home market. method, introduced in 1981, is considered a signifi- bleed A small amount of space at the edges of a shot cant advance in projection TV systems since they are to compensate for any loss between the picture as continually compared to standard TVs for sharpness it appears on the studio monitor and on the home and brightness. Also known as black matrix lenticu- TV screen. lar screen. The black stripe refers to a slightly re- bleed through The result of one channel superim- cessed black line that is imprinted onto the screen. posed over another. With a VCR, this may occur if This tends to add sharpness and contrast to the pro- the wrong open channel is employed. A local sta- jected image. tion may be transmitting at that frequency. Switch-

31 bleeding whites

ing from channel 3 to 4 (both known as “open” whole process is then repeated. Fundamentally it is a channels, with a switch located on the back of most special type of squegging oscillator and has applica- VCRs) or vice versa usually eliminates bleed through. tion as a pulse generator and a time-base generator. bleeding whites A condition in which white areas in blocking tape In TV production, tape affixed to places a TV picture appear to flow into black areas, caused on the floor to indicate where a performer should by excessive signal strength at the picture tube. stand. B-level title In home video, a secondary movie that is blonde A medium-size (2000 W) quartz iodine lamp not carried by all retail video outlets. used in TV. blinds [wipe] A periodic wipe pattern consisting of bloom Undesirable video picture caused by excessive repetitive identical stripes, a background image be- light saturation. ing seen through these “venetian blinds.” Changes blooming A fuzziness at the edges of bright objects in the width of the stripes give the appearance of or with subjects wearing white shirts in bright light, the blinds opening and closing. Of course the blinds as seen on a TV screen. This is an effect, sometimes themselves may be either a color matte or different caused when video becomes whiter-than-white, in live video. which a line that is supposed to be thin becomes fat blip 1. A white streak or speck that appears momen- and fuzzy on the screen. Blooming also occurs dur- tarily on a TV screen during playback of a video- ing slide-to-tape transfer when recording slides con- tape. Blips are caused by dropouts. These streaks tinuously. When the camera records a dark, occur occasionally, but if they seem to be excessive underexposed slide followed by a brighter one, the then the video heads need cleaning or the tape brand camera needs time to adjust between the two, caus- should be changed. 2. To remove a portion of the ing an annoying overexposure or blooming effect. recorded sound from a videotape of a TV program, Blooming also occurs when the brightness control such as expletive or other undesired words. is turned too high. This leads to an increase in the blit Short for bit-blit, which is short for bit-boundary size of the scanning spot on a CRT, or an out-of- block transfer. focus image. See also Photoconductive lag. blitter A circuit or device that does blitting. See bit-blt. blower Microphone. block 1. To work out talent and camera positions within blue gain control An adjustment that controls the a scene before taping. 2. Rectangular area of pic- amount of gain of the blue color relative to red and ture, usually 8 x 8 pixels, that is individually sub- green. jected to DCT coding as part of a digital picture blue gun The electron gun whose beam strikes phos- compression process. 3. Artifact of digital compres- phor dots emitting the blue primary color in a sion, usually displaying momentarily as misplaced 3-gun color TV picture tube. rectangular areas of picture. blue restorer The DC restorer for the blue channel of block cipher In video scrambling, a cipher that is pro- a 3-gun color TV picture tube circuit. duced by simultaneously transforming a group of blue video voltage The signal voltage output from message bits into a group of cipher bits. In general, the blue section of a color TV camera, or the signal the groups are the same size. voltage between the receiver matrix and the blue block converter Syn.: Up converter. gun grid of a 3-gun color TV picture tube. block downconversion (BDC) The process of lower- blue/red balance See Red/blue balance control. ing an entire band of frequencies in one step to some blue-beam magnet A small permanent magnet used intermediate range to be processed inside a satellite as a convergence adjustment to change the direc- receiver. Multiple BDC receivers are capable of inde- tion of the electron beam for blue phosphor dots in pendently selecting channels because each can pro- a 3-gun color TV picture tube. cess the entire block of signals. See also blur 1. Artifact in form of reduced dynamic resolution. Down-converter. 2. Generic term for out of focus (blurred). block matching Method of motion estimation based blur pan See Swish pan. on a sequential search for a maximal correlation BMK-multy Software capable of transmitting and re- between pixel blocks from the current video picture ceiving SSTV. Used in computer-based SSTV systems. and shifted blocks from the adjacent video picture. B-mode (of sound transmission). See MUSE-9 system. block out Prior to taping, to draw a sketch of, write BNC Bayonet Normalized Connector; Bayonet Neil- down, or run through the action that a scene or Concelman; Baby N Connector. A weatherproof series of scenes will contain. -lock coax connector standard on commercial block product cipher See Encryption. video equipment and used on some brands of satel- blocking The process of positioning actors, cameras, lite receivers. The most popular type of connector in , props, and other video production equipment. professional TV and video. blocking oscillator A type of oscillator in which block- BNR A noise reduction system introduced by Sony. The ing occurs after completion of (usually) one cycle of Beta Noise Reduction technique is similar to those oscillation and lasts for a predetermined time. The systems already in use but not compatible.

32 box

Bode equalizer An equalizer used to correct the fre- tor—is used to provide 100% positive feedback for quency response of TV sound circuits in which the alternating currents across an amplifier stage of unity amount of equalization can be adjusted, without gain or less. Bootstrapping is used for control of the change in the shape of equalizer characteristic, by output signals by using the positive feedback to con- operation of a single control. trol the conditions in the input circuit in a desired body brace A metal frame worn over the upper torso manner. Bootstrapping is commonly used in circuits to which a camera is attached and which supports that generate a linear time base, particularly in a that camera. sawtooth generator. Boella effect A reduction in the effective resistance of border A thickened edging, similar to a picture frame, fixed composition resistors when operated at VHF placed around a key signal, a digital effect, or along or higher frequencies, because of dielectric losses. the edges of a wipe. The thickness, color and soft- boob tube An unfavorable description of a TV set. A ness of the edge are generally adjustable. Syn.: edge. boob is a stupid or foolish person. border area That part of the display screen (visible boom Can be a microphone boom, light boom, or display) that is outside the defined display area. camera boom; a microphone or light boom is a long boresight The direction along the principal axis of ei- piece of metal piping at the end of which a light or ther a transmitting or a receiving antenna. microphone is attached to allow either microphone boresight point 1. The area of maximum signal or light to be positioned over the heads of subjects strength of a downlink signal. 2. The center of the in a scene while remaining outside the camera angle transponder footprint. of view; a camera boom is a complex piece of heavy- bottles See . duty equipment that allows the camera and opera- bounce 1. A sudden variation in TV picture brightness tor to be raised to selected heights. or size, independent of illumination of the original boom microphone A sensitive, directional microphone scene. 2. In broadcasting, signals bounced off the usually suspended above the camera or over the ac- ionosphere, satellites, or other bounce points. 3. A tion. Its function is to pick up specific sounds or voices. method of testing the very low frequency response boom operator Sound technician, a member of the of video systems (e.g. clamping performance) by TV crew responsible for manipulating the micro- periodic abrupt change of picture content, in par- phone and boom. ticular by the abrupt change of average picture level. boom shot See Crane. Typically, the bounce test is generated by interleav- boost To turn up; to increase in volume; to make the ing the test line with several stuffing lines and by video/audio signal stronger. alternating the stuffing lines between black and booster 1. A generator or transformer inserted in a white. Usually the bounce rate is adjustable through circuit in order to increase (positive booster) or de- a wide range, e.g., from 0.1 Hz to 2 Hz. crease (negative booster) the magnitude or to bounce light A light source or lighting technique used change the phase of the voltage acting in the cir- to soften shadows on a subject’s face, etc. A bounce cuit. 2. A separate RF amplifier connected between light may be the main light source that is aimed at an antenna and a TV set to amplify weak signals. the ceiling or a light-colored wall. The diffused light booster A diode in the line output stage of a will “bounce” off the surface and minimize harsh TV set that recovers much of the energy stored in shadows on the subject. the line deflection coils and makes it available as an bouncing A fault or design condition in which the additional source of supply. This can be added to d.c. level of a TV signal varies suddenly to cause the the normal supply to provide a high-voltage (boost) waveform display to appear to bounce up and down supply for the line output stage and other stages in and brightness of the picture monitor to vary sharply. the receiver. bow-tie antenna A dipole antenna in which the two booster station A low-power repeater of a full-power rods are replaced by triangular metal plates to give TV station that simply amplifies the signal of the a bow-tie appearance. Used chiefly with a reflector parent station and rebroadcasts it on the same chan- for UHF TV reception. nel to an immediate area. Boosters always broad- bow-tie timing test signal Analog component test cast on the same channel as the parent and thus signal in a form of frequency bursts put in Y and Pb, differ from translator stations that convert an incom- Pr channels. The frequencies are intentionally made ing signal from a parent station and rebroadcast it slightly different so that the summation of two sig- on another channel. nals, e.g., Y and Pb, produces a beating waveform booster voltage The additional voltage supplied by called “bow-tie.” The shape of the bow-tie clearly the damper to the horizontal output, hori- shows gain and delay inequalities between chan- zontal oscillator, and vertical output transistors of a nels. TV set to give greater sawtooth sweep output. box 1. Test pattern in the form of a white box on black bootstrapping A technique used in a variety of appli- or gray background. A change of window size pro- cations in which a capacitor—the bootstrap capaci- vides an easy way to control average picture level.

33 boxed mode

2. A mode of test pattern or wipe generation where of the horizontal synchronizing pulse and the start the main signal is gated by a window signal to pro- of the color burst in the standard NTSC color TV vide a background image at the perimeter. 3. Infor- signal. mal: To present on TV. bridge 1. A brief audio or visual passage or sequence boxed mode In teletext, a method of displaying char- intended to connect segments of a program. 2. In acters of one color on a rectangular background of voice and videoconferencing, a device that connects another color and superimposing the whole on a three or more telecommunications channels so that broadcast picture displayed on a TV set. they all communicate together. In video Bozo box Audio equipment linked to a TV camera, so conferencing, bridges are often called MCUs— simple that even Bozo the Clown could operate it. Multipoint Conferencing Units. One feature of some BPP Bits per pixel. video bridges is their ability to figure out who’s speak- BPS Bits per second. ing and turn the camera onto that person and have BPSK Biphase shift keying. BPSK is a digital frequency that person be on everyone’s screen. modulation technique used for sending data over a bridged-T network. A T-network with a fourth branch network. This type of modulation is connected across the two series arms of the T, be- less efficient, but also less susceptible to noise, than tween an input terminal and an output terminal. similar modulation techniques such as QPSK and Used in TV IF-amps as a filter. For example, two QAM. bridged-T filters can be used: one is tuned to 39.75 branch 1. The action of routing a user to a particular MHz and paralleled across the other, which is tuned part of a computer program or videodisc segment to 47.25 MHz. based on the user’s responses. 2. See Bandwidth re- bridging amplifier A device that boosts CATV signals duction (EUREKA-95 HDMAC system). and then feeds branching cables. It has a high-im- branch-switching See bandwidth reduction (EUREKA- pedance input and is used to tap the signal from a 95 HDMAC system). trunk line without disturbing its performance. break An accidental interruption of a broadcast brightness 1. The subjective of the amount of light program. received from a source. The objective measured break point An abrupt change of shape in a gamma brightness is more properly called luminance. The correction circuit. While such a circuit properly re- brightness of a TV set determines the grid bias ap- quires a smooth curve, the gain is more commonly plied to the CRT and hence the light output from varied in three discrete steps. If a smooth signal is the screen. Since the eye is not equally sensitive to passed through such a circuit, and then displayed all colors, brightness cannot be a quantitative term. on a , it is seen to consist of three 2. Former name for luminance. See also Variables of straight lines, each at an angle relative to the oth- perceived color. 3. In projection screens, the bright- ers. The break point is the point at which the change ness of the image in both front and rear projection in gain occurs. screens is determined by the directional characteris- break-out box An accessory designed to permit equip- tic of the screen material. In either type, the bright- ment with multiple-pin jacks to interconnect with sepa- ness for a given projector luminance output (lumens) rate, conventional audio and video plugs. The box varies in proportion to the reciprocal of the square often has two built-in jacks, one for accepting BNC of any linear dimension (width, height, or diagonal) connectors and the second for audio miniplugs. It also of the screen as follows: B = L/A, where B — per- has an extended cable with a multi-pin connector (8- ceived brightness, nit; L — projector light output, or 10-pin). Break-out boxes, mostly used by profes- lumen; A — screen viewing area (HxW), mxm. To sionals, are available in different configurations. improve the apparent brightness, screens can be breakthrough Unwanted signals present at the designed with directional characteristics. This char- output. acteristic, called screen gain, changes the brightness break-up 1. Total picture distortion that lasts for only equation as follows: B = G x L/A. 4. The intensity of a second or two. This usually occurs between scenes the video level. Refers to how much light is emitted when using a video camera or when stopping or by the display. pausing a VCR and starting again. Some portable brightness control A control that varies the bright- and home VCRs contain electronic circuitry that helps ness of the fluorescent screen of a CRT by changing to minimize these break-ups or “glitches,” as they the grid bias of the tube, thereby changing the beam are sometimes called. 2. Disruption of the video sig- current. Used in TV sets. On a video processor, a nal producing a noisy, distorted, or otherwise im- feature designed to adjust the video level. In this perfect video picture. Used to describe various respect, it is used to improve scenes that are either problems that produce an incoherent video picture. too dark or too light, to fade in and out when elimi- 3. Any other video or audio interference, such as nating commercials and to soften the effects of static. glitches and edits. breezeway The time interval between the trailing edge brightness equation See Brightness.

34 broadcasting service brightness ratio An indication, expressed as a ratio sion in which a single medium (wire) can carry sev- of the difference between the whitest and the eral channels at once. Cable TV, e.g., uses broad- blackest object in a scene; the range from brightest band transmission. In contrast, baseband white to darkest black as it occurs in the scene be- transmission allows only one signal at a time. ing recorded. Too wide a range between brightest broadcast To send information to two or more receiv- and darkest can lead to an unacceptable contrast ing devices simultaneously—over a data communi- ratio when the scene is displayed on a TV screen. cations network, a voice mail, electronic mail system, brightness value (luminance) The relative bright- a local TV or radio station or a satellite system. ness of a particular object in a scene; the point on Broadcast FTP Protocol (BFTP) A one-way IP multicast- the gray scale at which the object is between abso- based resource transfer protocol, the unidirectional lute black and absolute white, either of which can Broadcast File Transfer Protocol (BFTP) is a simple, be used as a point of reference to determine the robust resource transfer protocol that is designed to brightness value of the object. Essentially a relative efficiently deliver data in a one-way broadcast-only determination made by the observer. environment. This transfer protocol is appropriate brilliant 1. Full of light. 2. A color with high lightness for IP multicast over television vertical blanking in- and strong saturation. 3. Describing sound that is terval (IPVBI), in IP multicast carried in MPEG-2, as sharp and clear. The relationship between the bass with the DVB multiprotocol encapsulation, or in and treble frequencies can be regulated (brilliance other unidirectional transport systems. It delivers control) to achieve a more brilliant quality. constant bitrate (CBR) services or opportunistic ser- bring up Syn.: Fade in. vices, depending on the characteristics and features broad pulses Field-synchronizing pulses in the stan- of the transport stream multiplexor or VBI insertion dard TV waveform, so called because they are device. broader (i.e., of longer duration) than line-synchro- broadcast message A message from one user sent to nizing pulses. The receiver can distinguish between all users, as with a TV station signal. field- and line-sync pulses. In the NTSC 525-line sys- broadcast quality A level of picture and/or signal qual- tem there are six broad pulses, and in PAL 625-line ity that is assumed to be acceptable for main broad- system five broad pulses after each field. cast contribution, thus taken to mean “being of the broadband Also called wideband. 1. A band covering highest quality.” a wide range of frequencies, usually greater than broadcast station A TV or radio station that transmits those required for voice communications. Contrasts programs to the general public. Also called station. with baseband; synonymous with wideband. 2. De- Broadcast Technology Association See BTA. noting an electronic device or circuit, such as an amp, broadcast television Conventional, common, TV that operates satisfactorily over a large range of in- broadcasting; TV with accompanying sound for put signal frequencies. 3. A transmission facility that public use. has a bandwidth (capacity) greater than a voice grade A transmitter for use in a com- line of 4 kHz. (Some say that to be “broadband” it mercial AM, FM, or TV broadcast channel. should be 20 kHz.) Such a broadband facility—typi- broadcast TV Over-the-air broadcasting of TV pro- cally coaxial cable—may carry numerous voice, video grams, in contrast to cable TV, microwave, etc. The and data channels simultaneously. Each channel will major networks (ABC, CBS and NBC) and many lo- take up a different frequency on the cable. There’ll cal TV stations use broadcast TV for the transmis- be guardbands (empty spaces) between the chan- sion of their programs. nels to make sure each channel doesn’t interfere broadcast TV standard Set of technical specifications with its neighbor. A coaxial CATV cable is the classic defining the method of over-the-air RF-transmission broadband channel. Simultaneously it carries many of a TV picture with accompanying sound. The scan- TV channels. ning standard and color TV system are also included broadband antenna An antenna that will function in the definitions. satisfactorily over a wide range of frequencies, such broadcasting Radio or TV transmission to the public. as for all 12 VHF TV channels. Specific frequency bands are available for public broadband communications system System that broadcasts and are assigned in accordance with in- delivers multiple channels over a wide bandwidth ternational agreements. Broadcasting differs from to users. CATV is the quintessential broadband com- other methods of transmission, such as the two-way munications system. radio, that is aimed at a limited audience. broadband ISDN (B-ISDN) A standard for transmit- broadcasting satellite (BS) An artificial body in earth ting voice, video, and data at the same time over orbit to relay back to the earth radio and TV signals. fiber optic telephone lines. B-ISDN supports data broadcasting service A radio communications ser- rates of 1,500,000 bps. Has not been widely imple- vice in which the transmissions, including sound and mented. TV, are intended for direct reception by the general broadband transmission A type of data transmis- public.

35 broadcast-level video monitor broadcast-level video monitor See Video monitor- YCbCrK and RGBK digital video between pro-video ing equipment. equipment. Two parallel interfaces (8-bit or 10-bit, B-roll Supplementary or backup material. With video 27 MHz) or two serial interfaces (270 Mbps) are used. news releases, the B-roll generally follows the pri- BT.809 This ITU recommendation specifies informa- mary material on the same cassette. In editing, al- tion sent during the vertical blanking interval using ternate scenes are arranged on two reels, an A-roll teletext to control VCRs in Europe. and a B-roll, and then assembled. BT.1119 This ITU recommendation defines the wide- brown goods Electrical goods of a type traditionally screen signaling (WSS) information for NTSC and housed in wooden cabinets—for example, TVs, PAL video signals. For (B, D, G, H, I) PAL systems, , and hi-fis. WSS may be present on line 23, and on lines 22 and browse mode A feature that enables many electronic 285 for (M) NTSC. EIA-J CPX-1204 also specifies a slides or other items to be shown simultaneously on WSS signal on lines 20 and 283 for NTSC a video screen; useful for library browsers, TV edi- systems. tors, and others. BT.1124 This ITU recommendation defines the ghost Bruch blanking [sequence] See Burst blanking cancellation reference (GCR) signal for NTSC and PAL. sequence. BT.1197 This ITU recommendation defines the PALplus BS Broadcasting satellite. standard, allowing the transmission of 16:9 pro- BS.707 This ITU recommendation specifies the multi- grams over normal PAL transmission systems. channel audio specifications for the PAL and SECAM BT.1302 Defines the transmission of 16:9 BT.601 4:2:2 video standards. Covers the Zweiton and NICAM 728 YCbCr digital video between pro-video equipment. standards. It defines a parallel interface (8-bit or 10-bit, 36 MHz) BS antenna A to receive and a serial interface (360 Mbps). from a geostationary satellite. BT.1303 Defines the transmission of 16:9 BT.601 BskyB The broadcaster of the Sky Multichannels Pack- 4:4:4:4 YCbCrK and RGBK digital video between age, that carries three movie channels and a few pro-video equipment. Two parallel interfaces (8-bit general entertainment channels intended for Ireland or 10-bit, 36 MHz) or two serial interfaces (360 and the UK. Mbps) are used. BST-OFDM See Bandwidth Segmented Orthogonal BT.1304 Specifies the checksum for error detection Frequency Division Multiplexing. and status for pro-video digital interfaces. BT British Telecom. BT.1305 Specifies the digital audio format for ancillary BT.470 This ITU recommendation specifies the various data for pro-video digital interfaces. Also see SMPTE NTSC, PAL, and SECAM video standards used around 272M. the world. SMPTE 170M also specifies the (M) NTSC BT.1358 720 x 480 (59.94 Hz) and 720 x 576 (50 Hz) video standard used in the United States. BT.470 has 4:2:2 YCbCr pro-video progressive standards. Also replaced BT.624. see SMPTE 293M. BT.601 This ITU recommendation was developed for BT.1362 Pro-video serial interface for the transmission the of component video signals (YUV of BT.1358 digital video between equipment. Two and RGB). ITU-R BT.601 defines R’G’B’ to Y’CbCr 270 Mbps serial interfaces are used. conversion, digital filtering, sample rates, BT.1364 Specifies the ancillary data packet format for 4:4:4 and 4:2:2 YCbCr formats, and the horizontal pro-video digital interfaces. Also see SMPTE 291M. and vertical resolutions. Both 4:3 and 16:9 aspect BT.1365 Specifies the 24-bit digital audio format for ratios for 525-line and 625-line systems are pro-video HDTV serial interfaces. Also see SMPTE supported. 299M. BT.653 This ITU recommendation defines the various BT.1366 Specifies the transmission of timecode as teletext standards used around the world. Systems ancillary data for pro-video digital interfaces. A, B, C, and D for both 525-line and 625-line TV BT.1381 Specifies a serial digital interface-based (SDI) systems are defined. transport interface for compressed television signals BT.656 This ITU recommendation was developed for in networked television production based on BT.656 the transmission of BT.601 4:2:2 Y’CbCr digital video and BT.1302. between equipment. It defines a parallel interface BTA 1. Broadcast Technology Association. An organi- (8-bit or 10-bit, 27 or 36 MHz clock rate) and a zation of Japanese manufacturers and research, BTA serial interface (270 or 360 Mbps). has proposed the Clearvision system. 2. Broadband BT.709 This ITU recommendation specifies the 1920 x Telecommunications Architecture, an architecture in- 1080 RGB and 4:2:2 YCbCr interlaced and progres- troduced by General Instrument’s Broadband Com- sive 16:9 digital video standards. Frame refresh rates munications Division at the Western TV Show on of 60, 59.94, 50, 30, 29.97, 25, 24, and 23.976 Hz December 1, 1993. General Instrument said the plant are supported. is built to 750 MHz and can support reduced node BT.799 Defines the transmission of 4:3 BT.601 4:4:4:4 size and add services such as video-on-demand, te-

36 burst flag

lephony, interactivity, data services, etc. 3. Best Time burn 1. To destroy the light conversion function of a Available. certain portion of the vidicon target area by expos- BTA Clearvision system See Clearvision system. ing it to a light source that is too intense; also the BTA system See Clearvision system. result, an image permanently impressed on the tar- BTSC This EIA TVSB5 standard defines a technique of get area, that appears as black spots during display. implementing stereo audio for NTSC video. One FM See also Image burn. 2. The light spots or flares on subcarrier transmits a L+R signal, and an AM sub- videotape that result from a damaged pickup tube carrier transmits a L-R signal. (caused by pointing the camera at a or bright BTV Business TV. light source). A particular problem with older cam- Btx Also BTX. Bildschirmtext. eras using Vidicon pickup tubes. bubble A new TV serial developed from an already burn out TV images are said to suffer from burnt-out existing one (typically a ) and incorporat- whites, or bleached whites, when they appear on a ing some of its characters. TV screen to lack tonal gradation in the white and buffer 1. A circuit or component that isolates one elec- near-white portions. The four most common causes trical circuit from another. 2. A digital storage de- of this picture degradation are: (1) Over- of vice used to compensate for a difference in the rate the studio camera tube. (2) Unsuitable film densi- of flow of information or the time of occurrence of ties or gamma, effectively giving overall distortion. events when transmitting information from one de- (3) Amplitude nonlinearity in the vision signal chain, vice to another. 3. In telecommunications, a protec- causing the higher amplitude portions to be com- tive material used in cabling to cover pressed or, in the most severe cases, clipped com- and protect the fiber. The buffer material has no pletely. (4) Incorrect setting of receiver brightness optical function. and contrast controls. build day The day scheduled to erect a set in a TV burned-in image An image that persists in a fixed po- station. Also called set day or setup day. sition in the output signal of a TV camera tube after built-in antenna An antenna located inside the cabi- the camera has been turned to a different scene. net of a radio or TV receiver. Burned-In Time Code (BITC) This means the time code bulk acoustic wave An acoustic wave that travels information is displayed within a portion of the pic- through a piezoelectric material. ture, and may be viewed on any monitor or TV. bulk videotape eraser A device with an electroni- burst 1. A term used in video to refer to the color cally generated neutral magnetic field that can clear burst portion of a video signal. On a color a recording on tape by “scattering” the tape oxide graticule the burst portion of a video particles. Erasers are available in various sizes and camera signal, for example, is seen as a heavy hori- prices. Usually the wider the tape, the stronger the zontal line along the 180 degrees axis. If no line model necessary. Normally, home VCRs effectively appears on this testing unit, it signifies that no erase videotape automatically before re-recording color is being transmitted; hence, only a black- so that a bulk eraser is not required. The bulk video- and-white picture will be produced on a TV screen. tape eraser, also known as a tape eraser or simply 2. A rapid, intense sequence of words, as by a eraser, has several advantages: it works faster and speaker cramming material into a 15 s or other more effectively and assures security by erasing the brief TV sequence. entire tape. VCRs only erase up to the point where burst amp control A function usually found on a color the re-recording ends. processor and designed to manipulate the gain of bull’s eye pattern A zone plate pattern (circular or the control subcarrier in relation to the luminance elliptic) with lowest spatial frequency in the center signal. The burst amp control mainly affects the color and uniform rise of spatial frequency along any ra- mid-range, especially the flesh tones. Normally, the dius, so that the spatial frequency is directly propor- color deviations in the color subcarrier are corrected tional to the distance from the center. Syn.: circular in VCRs and TV sets by the ACC. However, in some zone plate; Fresnel zone plate. components in which the ACC may not be that bump mapping See Relief mapping. effective, the burst control can help. bumping down See Dubbing. burst amplifier In color TV set, an amp stage keyed bumping up See Dubbing; Eng. into conduction and amplification by a horizontal bunching In a velocity-modulated tube the process pulse at the exact of each arrival of the 3.58- or whereby the density of the electron stream is modu- 4.43-MHz color-burst signal. lated by the applied signal so as to gather the elec- burst blanking sequence A rule defining the specific tron into clusters at particular points along the drift line numbers in the vertical blanking interval on space. See Velocity modulation. which the subcarrier burst must be suppressed. In bundle of data In video compression, a group of pix- the PAL system it is often called “Bruch blanking els—usually a two-dimensional array of pixels from [sequence]” (after Dr. ). an image. burst flag A pulse produced by a color sync genera-

37 burst gate

tor; when present, it causes the signaling color cam- two or more buses are required for video signal era to produce a burst signal, or color burst. Syn.: switching. 3. A row of buttons on a video mix/ef- BF; BG; burst key; burst strobe. fects switcher that controls hundred of special ef- burst gate A signal that tells the system where the fects such as wipes, fades, etc. color burst is located within the scan line. Bushnell, Nolan Inventor of the first successful elec- burst gating Process of separating the color burst from tronic video game, Pong; founder of Atari. While the complete color signal. The encoded color TV sig- working at Bally Manufacturing Company, he soon nal, as transmitted, must include a phase reference learned that his employers showed little interest in for the chrominance detector in the receiver. This is his video game technology. He therefore built a coin- done by transmitting a short burst of the color sub- operated version of Pong on his own. Shortly after, carrier during the line-blanking interval that follows he founded Atari. the synchronizing signal. To keep the signal as im- business television (BTV) 1. and TV programs mune as possible from noise, the burst is maintained sponsored by companies, generally about their busi- for the longest possible time. This usually allows ness and transmitted free via closed circuit or other about 10 cycles of the sub-carrier to occur during distribution. 2. Point-to-multipoint video- the burst interval. To avoid phase errors between conferencing. Often refers to the corporate use of the burst and the encoded picture signal, the burst video for the transmission of company meetings, is applied to the video waveform in the encoder or training and other one-to-many broadcasts. Typi- colorplexer. This is done by matrixing the burst gat- cally uses satellite transmission methods and is mi- ing pulse from the studio sync pulse generator, into grating from analog to digital modulation the encoder modulators. The sub-carrier is then pro- techniques. duced by these modulators for the allotted period. Butterworth filter A filter that has essentially flat In a receive-type signal decoder, the burst is gated amplitude response in the passband and an attenu- into the phase reference circuits by a pulse derived ation rate beyond cutoff 6 dB per octave for a single- from the flyback of the horizontal scan. In other types pole filter. Transient response is much better than of decoder, the gating pulse is derived from the sig- for a comparable Chebyshev filter. See also Filter. nal synchronizing waveform. buttonhook feed A rod shaped like a question mark burst keying pulse Pulse for correctly timing the color supporting the feedhorn and LNA. A buttonhook burst in a TV color system, usually by a gating feed for use with commercial grade antennas is of- circuit. ten a hollow that directs signals from a burst phase Phase of subcarrier signal forming the feedhorn to an LNA behind the antenna. color burst with which reference the modulated sub- buzz This is sometimes called intercarrier buzz, a raspy carrier signal is compared. version of AC hum, usually caused by improper burst phase control A feature usually found on a adjustment of some IF circuits in TVs and VCRs. signal processor such as a color processor or pro- BW Bandwidth. cessing amplifier and designed to adjust the tint of BWF Broadcast WAV An audio file format based on the color signal. When the burst phase control is Microsoft’s WAV format. It can carry PCM or MPEG rotated in one direction, red turns toward blue, blue encoded audio and adds the metadata, such as a changes toward green and green shades veer to- description, originator, date and coding history, ward red ones. When the control is rotated in the needed for interchange between broadcasters. opposite direction, the color shifts also reverse their B-Y matrix A circuit to construct color difference roles. The burst phase control differs from the signal B-Y according to the equation B-Y = -0.30R- chrome control that affects color intensity rather than 0.59G+0.89B. tint. B-Y signal A blue-minus-luminance color-difference burst separator The circuit in a color TV receiver that signal used in color TV. It is combined with the lumi- separates the color burst from the composite video nance signal in a receiver to give the blue color- signal. primary signal. burst signal In a color TV transmission, the burst of bypass switch An electronic circuit, found on some high frequency associated with the color informa- image enhancers and processors, designed to per- tion. Syn.: color burst. mit the user to circumvent all video processing for burst-locked oscillator Oscillator, for example in a instant comparison between original and electroni- color receiver, locked to the color burst for subse- cally enhanced signal information. quent application to later circuits. bypassed mixed highs The mixed-highs signal, con- bursts See Explosion. taining frequencies between 2 and 4 MHz, that is bus 1. A channel along which signals travel from one shunted around the chrominance-subcarrier modu- of several sources to one of several destinations. 2. lator or demodulator in a color TV system. One complete channel of an audio or video mixing bypassed monochrome Deprecated term for shunted system, including inputs, gain controls, and output; monochrome.

38 C

C 1. Cyan. 2. Color component of s-video signal. 3. the Cable Reregulation Act of 1992, and by the 1996 CATV midband channel, 132-138 MHz. 4. Clock. Telecommunications Act. 5. TV standard; , Korea. Characteristics: 625 cable compatible A consumer electronics phrase lines/frame, 50 fields/s, interlace—2:1, 25 fr/s, coined in the 1980s to describe TV sets and VCRs 15,625 lines/s, aspect ratio—4:3, video band—5 that are designed to be directly connected to a cable MHz, RF band—7 MHz, visual polarity—positive, drop in a home. The units (sometimes called cable- sound modulation—A3, pre-emphasis—50 µs, ready sets) contain a tuner that can receive all cable gamma of picture signal—0.5. 6. Children through as well as broadcast channels. age 7—see Movie rating systems. 7. Compatible. cable compensation circuits Circuits designed to c/aph Cycles per active picture height, the measure of compensate for losses in TV signal links and not de- the spatial frequency of a periodic pattern in TV pic- signed for a wide frequency range. Some units can ture expressed as a ratio of picture height to the be adjusted over a wide range of gain and frequency period of the pattern. It could be derived from tvl with reasonably constant phase equalization. units: frequency value expressed in c/aph is equal to cable control See Cable television. half of the frequency expressed in tvl; i.e., “288 cable converter Syn.: Up converter. c/aph” is the same as “576 tvl.” cable correction, TV camera Since TV cameras may C1,C2 SC-HDTV chroma difference components. be used with varying amounts of camera cable, a CAA Constant Angular Acceleration. A laser video en- variable amount of cable correction must be pro- hancement designed to eliminate crosstalk, or un- vided. A typical loss figure for coaxial camera cables wanted extraneous signals. CAA, a modification of is 10 dB at 10 MHz for a 1,000 ft. run. It is impor- CLV, is accomplished by making rotational speed tant that the correcting network be properly changes part of a sub-multiple of the horizontal sync matched to the attenuation characteristic of the frequency. As a result, rolling horizontal noise bars cable, the loss being proportional to the square root are kept out of the screen image. of the frequency, as streaking effects will otherwise CAB Cabletelevision Advertising Bureau; Canadian As- occur on the picture. sociation of Broadcasters. cable drop The last connecting element of a cable cabinet The housing for a , TV receiver, system in a tree network configuration. The cable or other piece of electronic equipment. drop consists of a small coaxial cable (about 1/4" in cable Short form of cable TV. diameter) that connects the feeder cable of the dis- Cable Act of 1984 An act passed by the U.S. Congress tribution system to the subscriber’s home and then that deregulated most of the CATV industry includ- to his converter or TV set. Also called house drop. ing subscriber rates, required programming, and fees cable loss See Coaxial. to municipalities. The FCC was left with virtually no cable modem A data modem that uses the band- jurisdiction over cable TV except among the follow- width of a cable system, providing internet access ing areas: (1) registration of each community system over cable TV networks at speeds much faster than prior to the commencement of operations; (2) ensur- modems using telephone lines. ing subscribers had access to an A-B switch to permit cable origination Cablecasting. the receipt of off-the-air broadcasts as well as cable cable penetration The percentage of homes that sub- programs; (3) carriage of TV broadcast programs in scribe to CATV, generally within a specified area. full without alteration or deletion; (4) non-duplica- cable plant The system of wires in a building. For data tion of network programs; (5) fines or imprisonment communications purposes, the cable plant will typi- for carrying obscene material; and (6) licensing for cally be made of coaxial cable, , other receive-only earth stations for satellite-delivered via wire, or now, more commonly, optical fibers. pay cable. The FCC could impose fines on CATV sys- cable puller A person responsible for setting up and tems violating the rules. This act was superseded by handling power, sound, and picture cables. Gener-

39 cable ready

ally one cable puller is allocated to each camera. cessory designed to permit the viewing and taping The cable puller follows the camera during moving of various broadcast, CATV and pay TV channels by shots and makes sure that the cables do not using certain programmable VCRs. Watching one become tangled. program while recording another from pay TV or cable ready Cable compatible. The FCC developed a cable can present problems as well as complex con- series of specifications that a TV set (or VCR ) must nections. The components include a cable converter have to be advertised or sold as “cable ready” or with a decoder for the pay TV channel, a VCR and “cable compatible.” Those include the ability to tune a TV receiver. If the VCR is cable ready, it can be all standard cable channels up to 804 MHz and meet used to tune in various cable channels, but the pay standards on adjacent-channel, image-channel, and TV decoder presents another obstacle. To overcome direct-pickup interference; tuner overload; cable in- this, a CATV adapter can be added as a fourth unit, put conducted emissions; and radiated emissions. providing greater flexibility. For instance, to record a In addition, all cable-ready sets must contain a stan- pay channel while simultaneously viewing a VHF dard back-of-set decoder interface, designed to re- channel, the VCR has to have one of the preset chan- place the set-top box and permit the TV’s features nels tuned to that used by the cable operator. Then to be used with scrambled signals by separating the VCR/TV switch is set at TV, the receiver channel scrambling functions from program functions. at the one to be viewed and the converter box posi- Cable Reregulation Act of 1992 Reregulation Bill tioned at the pay TV channel. The adapter offers 1515 passed the U.S. Congress in October 1992, other possible combinations such as recording a VHF forcing the FCC to reregulate cable television and channel while viewing a pay TV program. Without CATV rates (after the Cable Act of 1984 effectively this device, a viewer must have either two decoder deregulated the cable TV industry). After the act was boxes, a patch box or an RF switcher to perform the passed, the FCC forced the industry to reduce its same functions. The latter two accessories are pref- rates by 10% in 1993 and then again by 7% in 1994. erable if more inputs are required, the patch box cable system See Cable television. being less permanent than the switcher. cable system operator See Cable television. cable television carrier system An arbitrary method Cable Transport System (CTTS) Trans- employed by cable systems in which the transmis- mission system that allows multiplexed telephony sion of broadcast signals is “offset.” This results in traffic to be carried through a single coaxial cable minimal screen interference from neighboring chan- simultaneously with TV channels; Hughes Network nels. Although typical TV broadcast channels start Systems Ltd., Hertfordshire, England. The system and finish with MHz numbers that are even (e.g., converts telephony signals onto an RF carrier for dis- 66-74 MHz for ), different carrier systems tribution through existing fiber and coaxial TV cables. use varying offset frequencies. Two basic types are With a coaxial cable-TV distribution system, TV sig- the HRC (Harmonically Related Carrier) and the ICC nals are modulated onto an RF carrier that runs be- (Incremental Coherent Carrier) systems. With HRC, tween 550 and 600 MHz. Multiplexed telephony the cable operators offset all channel frequencies, channels are then assigned to carrier signals either channels 5 and 6 by 1.25 MHz and the remainder side of the TV signal. The path from a cable by .75 MHz. Cable companies utilizing the ICC sys- company’s headend to subscribers runs at 650 MHz, tem offset the frequencies of channels 5 and 6 by 2 and the return link at between 40 MHz and 50 MHz. MHz. Offsetting, however, can create problems. The cable television (CATV) A TV program distribution cable converter may have to be retained, whereas system in which signals from all local stations and with normal channels it can be eliminated since usually a number of distant stations are picked up cable-ready tuners can lock in on these stations. Fi- by one or more high-gain antennas at elevated lo- nally, another disadvantage of offset frequencies is cations, amplified on individual channels, then fed that these channels become difficult to tune in with directly to individual receivers of subscribers by over- any degree of accuracy. head or underground coaxial cable. The mechanical cable television converter A device used with CATV connections or electrical conductors are operated to carry multiple channels to subscribers who could by cable control. Cable TV systems are generally receive them on an unused channel. Based on the called cable systems; the companies that own and principle that many channels could be carried in ex- operate them are known as cable system operators. actly the same electronic space as one, cable opera- Used to improve reception and to make more sta- tors started to offer 12 channels through their tions available in a given area. The system some- converter box. (The Focus-12 device was first used times includes equipment for originating local in New York’s borough of Manhattan.) The number programs, time and weather reports, news bulle- of channels capable of being carried by the con- tins, and other services. Also called community verter grew and the Gamut-26 was introduced. Be- antenna TV. cause of the shielding of the converter, the channels cable television adapter An automatic switching ac- are transmitted to the box by cable, not over the air.

40 camera chain cable television cooperative A CATV station owned ally indestructible and therefore needs no protec- by subscribers. There are fewer than 3 dozen cable tive caddy. By the mid-1980s the public virtually re- cooperatives of the more than 4,700 cable systems jected both systems, selecting videotape as the in the US. Most of these co-ops are in the Midwest. medium of its choice. However, the laserdisc made Cable co-ops differ from municipally owned cable a comeback by the late 1980s. stations that are owned by the local governments. call In film, TV, theater, the stipulated time to report See Public access TV. for work on any given day. cable television frequency distribution The chan- call letters The name of a radio or TV station. Most nel-numbering plan developed by the EIA/NTCA stations east of the Mississippi River have call letters Joint Committee on Receiver Compatibility and pub- beginning with W; west of the Mississippi, call let- lished by both organizations as an Engineering Stan- ters usually begin with K. Canadian stations begin dard. Standard frequencies refer to cable systems with C; Mexican stations, with X. that transmit on the standard off-air frequencies for call sheet A list of dates and times the cast and channels 2 to 6 and 7 to 13. Supplemental channels crew must report for a TV, film, theatrical, or other are in 6-MHz increments, counting down from chan- production. nel 7 (175.25 MHz) to 91.25 MHz and upward from call-in Referring to a radio or TV program that broad- channel 13 (211.25 MHz). casts telephone conversations with listeners. Cable Television Relay Service (CARS) An inexpen- camcorder A portable video camera that incorporates sive microwave service for transmitting a large num- its own videotape and audio tape recorder. It is ca- ber of CATV program signals from one site to pable of recording full-color videotapes with sound. another, as from head end to head end. The ampli- Many are equipped with telephoto lenses to permit tude-modulated CATV channels from 112 to 300 panning from near to distant objects or scenes. MHz are heterodyned upward to 12,758.5 to Camcorders come in a variety of formats: VHS, S- 12,946.5 MHz and transmitted as microwave chan- VHS, VHS-C, S-VHS-C, 8mm, Hi8. nels. This is called an amplitude-modulated link, or Cameo 1. Macintosh-based personal video-conferencing AML. For relatively short distances, an AML is usu- system, announced by Compression Labs (CLI) in Janu- ally more economic than cable or conventional mi- ary of 1992. Developed jointly with AT&T and de- crowave service. See also Auxiliary radio services. signed to work over ISDN lines the Cameo transmitted Cable Television Relay Station (CARS) A fixed or 15 fps of video and needed an external handset for mobile station used for the transmission of TV and audio. 2. A lighting technique used in TV production related audio signals, signals of standard and FM in which only the foreground is lighted. The back- broadcast stations, signals of instructional TV fixed ground remains intentionally dark or unlit. stations, and cablecasting from the point of recep- camera The eye of the video system; an instrument tion to a terminal point from which the signals are capable of absorbing the light values of a scene and distributed to the public. converting them to a corresponding series of elec- cable up To (cause to) become connected to a cable trical pulses through the use of a pickup TV system. tube such as vidicon; a light-sensitive CRT (and its cablecasting 1. Programming carried on CATV, as op- associated electronic circuitry and lens optics), that posed to over-the-air broadcasting; also called cable translates the light values of any scene it views into origination. 2. The transmission of such programming. a set of voltage variations that can be used to recre- cable-compatible tuner This tuner eliminates the need ate those light values on another CRT such as that for external channel selection and provides direct tun- used for TV display. A solid-state camera has also ing of regular VHF/UHF channels plus additional un- been developed in which the transduction element scrambled cable channels. (A convertor may be is an array of CCDs. This type of camera is very much necessary to view scrambled CATV channels.) smaller and lighter than those containing electron cabletext Teletext transmitted by cable or satellite to tubes and is typically the size of an ordinary hand- CATV systems. held photographic camera. cache Local or temporary storage. camera categories There are two major TV camera caddy A protective plastic jacket, sleeve or holder that categories, live and film. Live cameras generate video stored the now defunct CED videodisc. The caddy signals from the optical images of indoor and out- was inserted into VDP that automatically removed door scenes. Film cameras generate TV signals from the disc and prepared it for play. The CED, devel- film or slide images. oped by RCA, contained delicate microscopic camera chain The configuration of apparatus required grooves that were protected by the caddy. The CED to produce a video signal from an optical image, system, that employed a stylus that physically tracked e.g., a TV camera, associated amps, power supply, a the disc grooves, differed from the LaserVision sys- monitor, and the cable needed to bring the camera tem. The latter uses a laser beam that “reads” the output signal to the control room of large studio information of a grooveless videodisc that is virtu- camera system.

41 camera control unit (CCU) See Studio camera. medical center, prison. There may be several tele- camera cue A red light or buzzer indicating that a TV phone systems. There may be several LANs on a cam- camera is shooting a scene for transmission, live or pus. They will be connected with bridges and/or taped; also called cue light, tally light, or warning routers communicating over telephone, microwave light. or fiber optic cable. camera flow diagram A diagram that traces output Cannon connector A particular brand of audio jack from the cameras to its ultimate destinations. Used that features three leads—two for the signal and in TV studios. one for the overall system grounding; a very secure camera head See Studio camera. type of connecting jack often found on high-quality camera jack An input on VCRs that accepts video cam- microphones, video monitors, and VTRs. era connections. Manufacturers use 10-pin, 14-pin cans Headphones worn by TV and radio production (Type K) or 5-pin DIN jacks. However, two similar personnel. The slang term is also used to refer to jacks may not necessarily be compatible. For ex- the circular metal containers in which a film is stored, ample, a 10-pin jack on a specific camera may fit a leading to the industry use of the phrase, “in the 10-pin VCR , but not all functions assigned to each can,” for a completed motion picture or TV program. pin will operate as intended. Adapters are available cap sheet Caption sheet. for connecting jacks of different pin numbers and electronic disc See CED. configurations. capacitor An that accepts an camera log A detailed listing of the shots each cam- electrical charge that it can dispense at a consistent era is expected to take. and predictable rate. In relation to a VHD videodisc camera mode Mode of vertical-temporal video signal system, a capacitor is formed by the combination of processing that assumes that odd and even fields of the disc and a tiny piece of metal, known as an elec- the TV frame contain information from different time trode, that is part of the stylus. moments, typical of interlaced TV camera output. capstan A rotating shaft on the VCR that is turned by camera mounting head An accessory video camera a motor and which, in turn, governs the speed of support designed for moving and manipulating the the tape as it proceeds from the supply reel to the video camera efficiently. Mounting heads, originally take-up reel. The capstan is supplemented by the simple devices based on friction and gears that were pinch roller. Pressure holds the tape firmly against designed for the film industry, have taken on new the capstan. engineering techniques, resulting in complex (e.g. capstan lock A method of stabilizing videotape play- fluid) heads for use with professional video cameras back that essentially relies on the stability of the and camcorders. power source for a constant base. It is the first de- camera opticals Special effects, such as IRIS IN or IRIS gree of lockup, suitable mainly for home VTRs. Cap- OUT, that are generated using only the camera stan lock is not a very stable state. See Lockup. itself. capstan servo 1. The control of the tape to assure camera rehearsal A full-dress rehearsal, one with cos- accurate and uniform speed during record and play- tumes, at which the movements of the camera are back by passing the tape between a spinning post blocked; more advanced than a reading or script in the tape path, which is an extension of the VCR rehearsal. motor and is called capstan, and a rubber pinch camera search A video camera feature that allows roller. Internal electronic circuitry in the VCR senses the user to review existing scenes while the camera any fluctuations in tape speed and advances or re- remains in Record mode. tards the tape to a predetermined rate as it passes camera signal The video output signal of a TV between the capstan post and the pinch roller. 2. camera. An electronic circuit built into editing VTRs to pro- camera tube An electron-beam tube in a TV camera vide smooth edits. The servo is a speed control sys- that converts an optical image into a corresponding tem that locks into the sync of another recorder to charge-density electric image and scans the result- insure that both video signals are interlocked for ing electric image in a predetermined sequence to glitch-free edits. Without this feature, picture provide an equivalent signal. Examples are the icono- breakup appears between scenes. See Lockup; scope, , image orthicon, and vidicon. Vertical lock. A chip MOS can replace the conventional camera capstan servo editing Head override editing. A tube, though the cameras using this process are more method of electronic editing in which a new video costly. Also called image pickup tube, pickup tube signal replaces an already existing signal without dis- and TV camera tube. rupting the picture (except for a switch from signal camera-to-VCR adapter See Adapter. 1 to signal 2 at the point of addition). The motor campus environment An environment in which us- speed of the capstan—which controls the speed of ers—voice, video and data—are spread out over a the videotape—on VTR B is controlled by the verti- broad geographic area, as in a university, hospital, cal sync pulses on the videotape on VTR A during

42 cartridge lamp

the “editing” of the signal on tape A onto tape B so ent property of both an FM system and the satellite that no disruption of the flow of signal information transponder. occurs during the switch of signals. cardioid One of many possible pickup patterns of a CAPTAIN Character And Pattern Telephone Access directional microphone. As the name suggests—car- Information Network system, Japanese version of dioid means heart-shaped—sound waves coming to Teletext resembling Minitel in . the microphone’s rear and sides are rejected, while caption generator Device used to generate text and those directly in front of it are received. simple graphics for video titles or captions. carrier 1. Short for carrier frequency, carrier wave. A caption key A key signal derived from a title source pure-frequency signal that is modulated to carry such as a character generator. Syn.: title key. information. In the process of modulation it is spread caption sheet Also called cap sheet, dope sheet. In out over a wider band. The carrier frequency is the TV, a list of scenes. unmodulated frequency on any TV channel. 2. A Caption Writer VCR , Inc., Miami. A company that provides communications circuits. VCR that can print instant transcripts of TV pro- Carriers are split into “private” and “common.” A grams through an ordinary computer . The private carrier can refuse service to anyone, but a VCR is intended to be connected directly to a printer, common carrier can’t. Most of the carriers in U.S. using the parallel port, or to a computer, using the industry—local phone company, AT&T, MCI, US serial port. Sprint, etc.—are common carriers. Common carri- captioning The process of superimposing subtitles at ers are regulated. Private carriers are not. 3. The the bottom of a TV screen. mechanism that holds the cassette inside the VCR; capture (of data) The recording of data on a form or part of the cassette-lift mechanism. its entry into a computer. carrier chrominance signal Chrominance signal. capture effect A property of an FM system to receive carrier frequency A certain wavelength of a special only the stronger of two signals, suppressing the frequency on which a signal is registered for trans- weaker of the two. In the case of an AM system (as mission in a clear way to a receiver. The audio or used in conventional TV broadcasting for video, and video signal is then isolated from its carrier frequency, in AM broadcasting and CB radio), a signal that is amplified and reproduced. 20 dB weaker than the desired signal can cause a carrier synchronization In a TV set, the generation noticeable, annoying interference. In an FM system of a reference carrier with a phase closely matching (assuming we are above threshold), the weaker sig- that of a received signal. nal will be suppressed to the point where it is inau- carrier wave Syn.: carrier. The wave that is intended dible. A performance figure given for hi-fi FM to be modulated, or, in a modulated wave, the car- receivers, called the capture ratio, is the numerical rier-frequency spectral component. The process of value that measures this effect. modulation produces spectral components falling capture range Range of the input signal frequencies into frequency bands at either the upper or lower to which a phase locked loop (PLL) is able to lock. side of the carrier frequency. These are sidebands, Once locked, the PLL generally has a greater input denoted upper or lower sideband according to frequency range known as hold range. The term is whether the frequency range is above or below the similarly applicable to genlocking SPGs. carrier frequency. A sideband in which some of the capture ratio 1. The ability of a tuner to restrict or spectral components are greatly attenuated is a ves- reject a second, weaker signal in proximity to the tigial sideband. In general these components corre- main signal. This permits the strong signal to be re- spond to the highest frequency in the modulating ceived without interference from secondary signals signals. A single frequency in a sideband is a side traveling on the same frequency. Capture ratio is frequency. The baseband is the frequency band oc- measured in dB; the lower the number, the more cupied by all the transmitted modulating signals. effective the tuner in terms of “capturing” the strong CARS Community antenna, or cable television, relay signal. Moderate-priced tuners may have a capture service. A fixed or mobile station used for the trans- ratio of approximately 3 dB while more costly units mission of television and related audio signals, sig- approach a figure of 1 dB. The term, that applies nals of standard and FM broadcast stations, signals more to audio than to video, should not be con- of instructional television fixed stations and fused with alternate channel selectivity that refers cablecasting from the point of reception to a termi- to adjacent stations. 2. In FM systems, that ratio of nal point from which the derived signals are distrib- two received signals in which the stronger signal sup- uted to the public. presses the weaker one. Since the systems used for cartridge A plastic container holding a single reel, satellite TV use FM for both video and audio, a sat- closed loop of videotape. In contrast, a videocas- ellite transponder will respond to a (received) pirate sette contains two reels. Cartridges are presently signal only a few dB stronger, completely suppress- found only on industrial machines. ing the legitimate program carrier. This is an inher- cartridge lamp A pilot or dial lamp that has a tubular

43 Cartvision format

glass envelope with metal-ferrule terminals at each the cassette into threading position. The mechanism end. It resembles a TV or radio and is mounted includes the carrier. in the same type of socket clips. castellation [of test pattern] Alternating white Cartvision format A now-defunct 1/2-inch-wide tape and black boxes at the perimeter of a test chart. cassette system capable of two hours of playing time; Useful to test TV picture positioning on the display 1972. Developed by Avco and distributed by Sears. screen, also to observe picture cropping, display This format used a skip field, 3-head system, result- registration, etc. ing in a reduction of tape consumption. Only every CATA Community Antenna Television Association. An third TV video field was recorded. On playback, each association of CATV operators and owners, based of the three heads was played in order on the same in Fairfax, VA. track, producing a proper TV signal. Vertical resolu- cathode-ray tube (CRT) An electronic tube in which tion was one-half of a standard TV signal. Fast mo- a beam of electrons can be controlled and directed tion of the picture content could not be reproduced by an electronic lens so as to produce a visible dis- because of the loss of two out of three TV fields. play of information on the surface of the tube or to cascade voltage multiplier A circuit consisting of store data in the form of an energized portion of some stages of the half-wave doubler stacked to- the tube’s surface. All CRTs have an electron gun to gether. Used in TVs. produce an electron beam, an electrode (cathode cascode amplifier A common-emitter transistor amp or grid) that varies the electron beam intensity and in series with a common-base stage analogous to a hence the brightness, and a luminescent screen to grounded-cathode, grounded-grid amp. Its input re- produce the display. The electron beam is moved sistance and current gain are nominally equal to the across the screen either by deflection plates or mag- corresponding values for a single common-emitter nets. The deflection sensitivity of the tube is the dis- stage, and the output resistance is approximately tance moved by the spot on the screen per unit equal to the high output resistance of the common- change in the deflecting field. Electromagnetic de- base stage. Found in TV receiver-tuned amps where flection is used when high-velocity electron beams the collector load is replaced with a tuned circuit, it are required, as in TV sets, that need a bright dis- is most effective in amplifying signals that are 25 play. Focusing of the beam may also be done elec- MHz and higher. trostatically or electromagnetically or by a Cassegrain feed system In satellite TV, an antenna combination of methods. A greater degree of fo- feed design that includes a primary reflector, the dish cusing is required when the electron beam is de- and a waveguide to a LNA. flected towards the edges of the screen. The point cassette A cartridge for holding and winding mag- at which the electron beam comes to a focus is the netic tape. Also called cassette shell; shell. crossover area and the solid angle of the cone of cassette eject The method used to remove a video- electrons emerging from this area is the beam angle. cassette from the VCR housing. Older machines sim- For convenience the deflection and focusing coils ply allowed the cassette chamber to spring up with are often mounted around the narrow neck of the a loud thud. Today’s more sophisticated methods tube as a single unit, termed a scanning yoke. Such include the use of gears, air-dampened pistons, coil an arrangement reduces the overall physical dimen- springs and pneumatic fan blades—all much qui- sions of the assembly and is particularly important eter and gentler. when the tube contains more than one electron cassette indicator An icon that appears in the display beam, as in the double-beam CRT or some forms of window of some VCRs to indicate whether the ma- color picture tube, and therefore requires more than chine contains a videocassette and the direction of one set of coils. The screen of the CRT may be coated the tape movement. A series of LEDs connects the with aluminum on the inside and this coating held two circles that make up the icon and light up se- at anode potential. Such an aluminized screen pre- quentially to describe in what direction the tape is vents the accumulation of charge on the phosphor moving. The indicator is not illuminated when the and improves its performance by increasing the vis- machine is shut down. ible output and reducing the effects of ion cassette shell The container that holds the videocas- broadment. In the case of a CRT in which the screen sette. The shell usually has several vital parts to help is not aluminized, the maximum potential difference move the tape accurately from the supply to the that can be applied between the anode and cath- take-up reel. These include a flange, hub and clamp, ode is limited to the value at which the secondary leaf spring, tape pad, guide pin, guide roller, tape emission ratio of the screen rises to unity and is guide and tape guide rib. A window is provided on known as the sticking potential. There are three types the top to view the two tape reels. Also called shell. of CRT displays: the familiar TV receiver, the moni- cassette-in switch A small leaf switch used to detect tor and the monitor/receiver. The electronic when a is fully loaded in the VCR. viewfinder of a video camera is actually a miniature cassette-lift mechanism A mechanism that brings monitor. CRT was originally called Braun tube. Also

44 CCIR 601

called kinescope and picture tube when used in TV or most Intranets. Protocols such as RSVP are be- sets. ing developed and deployed to provide bandwidth cathode-ray-tube display 1. The presentation of a guarantees. received signal on the screen of a CRT. 2. That part CBS Columbia Broadcasting Service, one of the major of a system (a TV receiver, monitor or monitor/re- U.S. television networks. ceiver) in which controlled electron beams provide CC 1. Closed Caption. 2. CATV hyperband channel, data in visual form. 312-318 MHz. cathode-voltage-stabilized camera tube Syn.: low- CCD Charge-coupled device. electron-velocity camera tube. See Camera tube; CCD color comb filter Advanced electronic circuitry, Image orthicon; Vidicon. usually found only on a TV monitor/receiver, designed cathodoluminescence The emission of light when to improve image detail and definition without color substances are bombarded by cathode rays (elec- fringing or video noise appearing on screen. The trons). The frequency of light emitted is characteris- color comb filter makes use of a CCD to gain greater tic of the bombarded substance. luminance/chrominance separation. Separating CATV Originally Community Antenna Television. Also these two elements of the signal—while keeping Cable Television (now generally meaning cable TV). the full luminance bandwidth—results in less dis- CATV grew from a select service to small communi- tortion in the final picture. ties who were isolated from the reception of con- CCD telecine Telecine device where the scanning is ventional TV programs. Local companies supplied achieved by the linear passing of film across a single transmission to these remote areas—for a slight fee. TV line CCD sensor array. The complete TV frame is Since the telephone lines could not carry the “broad- built up in a suitable buffer store. Syn.: line array band” TV required, cables were used instead. telecine. CATV adapter See Cable television adapter. CCDC Channel-Compatible DigiCipher, one of the pro- CATVI Cable-TV Interference. posed HDTV simulcast systems. CAV 1. One of the two formats of the laservision (LV) CCF system Chroma crawl free system. Chroma crawl videodisc system. A constant angular velocity (CAV) is an artifact of encoded video, also known as dot disc plays for 30 minutes per side and is capable of crawl or cross-luminance, that occurs in the video many special effects not available to the CLV, one- picture around the edges of highly saturated colors hour-per-side format. The CAV disc turns at a con- as a continuous series of crawling dots. It is a result stant speed of 1800 rpm or 30 revolutions per of color information being confused as luminance second, matching TV’s standard of 30 frames per information by the decoder circuits. A CCF system second. This permits such special effects as freeze eliminates chroma crawl. frame, single frame advance, slow motion, visual CCIR Comite Consultatif International des Radio- scan, etc. 2. Component Analog Video. communications or International Radio (Consultative cavity resonator Type of tuned circuit used at ultra- Committee in International Radio). The international high frequencies (Bands IV and V). Instead of the body to determine standards for telecommunica- more conventional and capacitor, a hole or tions. Used to describe 625-line TV system used cavity inside a piece of metal can be made to reso- primarily in W. Europe. The US system of TV is 525 nate with a . lines. The HDTV system is 1125 lines. The CCIR no Cb Coded color difference signal (digital B-Y). longer exists—it has been absorbed into the parent C-Band The range of frequencies from 3.5 to 6 GHz. body, the ITU. The microwave frequency range of a satellite TV sig- CCIR 1119 See BT.1119. nal. These signals usually fall between 5.9 and 6.4 CCIR 1124 See BT.1124. GHz when transmitted to a satellite and range from CCIR 470 See BT.470. 3.7 to 4.2 GHz when returned to earth. CCIR 601 (BT.601) Now known as ITU-R BT.601-2. An C-Band satellite Relatively low-powered communica- internationally agreed-upon standard for the digital tions satellite that uses the C-band. These satellites encoding of component color TV that was derived cover the entire US. They are used by cable systems from the SMPTE RP125 and the EBU 324E standards. and TV broadcasters to receive the signals on large It uses the 4:2:2 sampling scheme for Y,U and V TVRO dishes. C-Band offers over 250 channels of with luminance sampled at 13.5 MHz and chromi- video and 75 audio services to about 850,000 sub- nance (U and V components) sampled at 6.75 MHz. scribers in the U.S., at the time of this writing (2002). After sampling, 8-bit digitizing is used for each chan- CBC Canadian Broadcasting Corporation. nel. These frequencies are used because they work CBR Constant bit rate. CBR refers to multimedia de- for both 525/60 (NTSC) and 625/50 (SECAM and livery when there is dedicated bandwidth and the PAL) TV systems. The system specifies that 720 pix- data can be delivered at a guaranteed constant bit els be displayed on each line of video. The D1 digi- rate. MPEG-1 and 2 are designed for CBR delivery. tal videotape format conforms to CCIR 601. See CCIR Constant bit rate cannot be assured on the Internet 656, ITU-R BT.601-2.

45 CCIR 653

CCIR 653 See BT.653. they will work with different TV formats, such as CCIR 656 (BT.656) The international standard defining PAL or SECAM. Since the discs are encoded using the electrical and mechanical interfaces for digital the binary system, each system translates this code TV operating under the CCIR 601 standard. It de- to fit its own TV standard before it appears on screen. fines the serial and parallel interfaces in terms of The music portion of the disc, of course, is not connector pinouts as well as synchronization, blank- affected. ing and multiplexing schemes used in these inter- CD-i Compact Disc-Interactive. A compact optical disc faces. A simplified version of this interface is system containing text, graphics, still images and commonly used for transferred digital video between high-quality sound, which can be played back in a IC chips. Now known as ITU-R BT.656. dedicated CD-i player. The CD-i player can be con- CCITT Consultative Committee in International Teleg- nected to a standard TV set and optionally to a raphy and Telephony. The international body that stereo system. CD-i was developed jointly by Sony determines standards for telecommunications. Corp. and Philips Electronics NV, who defined its CCITT V.23 International videotex modem standard basic specifications in what is known as the Green (1200/75 bps or 75/1200 bps). Book, in the 1980s. By 2000, DVD and other plat- C-clamp A metal device shaped like the letter C, used forms largely supplanted CD-i. to connect lighting instruments to a pipe grid above CD-ROM Compact Disc Read Only Memory. An optical a TV studio. A version of the C-clamp is also used to disk capable of storing large amounts of data. A temporarily hold flats together or pieces of scenery CD-ROM player is needed to read a CD-ROM. in place. CD-ROMS are well-suited to large software applica- CCR Central Control Room. tions, graphics, sound and video. CCTV Closed-circuit TV. CD-ROM XA Compact Disc Read Only Memory CCU Camera Control Unit. See Studio camera. eXtended Architecture. Microsoft’s extensions to CCVS Composite Color Video Signal. CD-ROM that allow audio to be interleaved with CCW Counter-clockwise. data. Though it is not a video specification, limited CD 1. Color Difference signals of (R-Y) and (B-Y). The video can be included on disc. Green signals (G-Y) can be extracted from these two CDS Color Difference Signal. signals. 2. Abbreviation for compact disc. CDTV 1. The first computer to incorporate a built-in CD graphics player A CD unit, resembling the con- CD-ROM drive, designed and sold by Commodore. ventional CD player, but equipped to play back still 2. Canadian Digital Television Association. images, in addition to the usual 80 minutes of mu- CD-V Compact video disc. A format for putting 5 min- sic, recorded on CD+G (Graphics) discs. Once the utes of video on a 3-inch disc. This format has come unit is connected to a TV set, the owner can view and gone. song lyrics, biographical data about performers and CDV Compression Labs Compressed Digital Video, a drawings—items usually appearing as liner notes. compression technique used in satellite broadcast Normal CD players do not have the necessary fea- systems. CDV is the compression technique used in tures, such as outputs for video or S-video, to play CLI’s SpectrumSaver system to digitize and com- back these images; neither do they offer a graphics press a full-motion NTSC or PAL analog TV signal so output jack for an add-on decoder that can access that it can be transmitted via satellite in as little as 2 these still images. MHz of bandwidth. (A normal NTSC signal takes 6 CDDI Copper distributed data interface. A high-speed MHz.) data interface, similar to FDDI but using copper in- CED Capacitance Electronic Disc system; the RCA video stead of fiber. disc marketed in the 1980s. System of video record- CD+G A CD disc, similar in appearance to the conven- ing a grooved disc, employing a groove-guided ca- tional disc, that contains visual information in the pacitance pickup. Could be considered the final form of still images or graphics. When a specially chapter in grooved media that began with the Edison equipped CD graphics player is connected to a TV cylinder. set, these discs can provide pictures, musical infor- Ceefax The teletext service of the BBC. Its name is a mation or text. The resolution is similar to that pro- corruption of the phrase “see facts.” Ceefax trans- duced by computer graphics. CD+G discs, which first mits some 100 pages of information such as news, appeared in 1988, can be played on standard CD weather, and entertainment options, that can be players, but the added visual benefits will not be displayed on the TV. The information can be called available. Because of its limited technology, the up at any time by the viewer using a keypad. CD+G disk produces only still images, differing cellular vision Microwave TV transmission system in sharply from the CD-Video disc or CD-I format, that 28-GHz band to send voice and video over the air- turns out “moving pictures.” However, this format waves. The cellular vision system, financed by the allows the disc to retain its full 80 minutes of play- Suite 12 Group (Freehold, NJ), was invented by Ber- ing time. Another advantage of CD+G discs is that nard Bossard. An alternative to CATV, it makes use

46 channel lock

of a band that was once considered to be too high number of channels the band can accommodate; a frequency for effective TV transmission. The TV width varies from country to country. In the US, spec- signals are received by a 4.5-inch-square, flat an- trum space is about 6 MHz wide for each channel. tenna that can be mounted either inside or outside 2. Signal transmission or processing path dedicated a customer’s house. Microwaves at 28 GHz can carry to specific signal or signal component, e.g. “chromi- more information than longer-wave transmissions, nance channel.” 3. Part of digital video effects de- and they can be bounced off buildings. The major vice having its own control parameters and dedicated drawback to is seen as its to manipulation of one TV picture. For example, two- limited range—only a few miles from the transmit- channel DVE is able to rotate one picture and simul- ter. To eliminate mutual interference and ghosting, taneously squeeze another picture. microwave transmissions from adjacent transmitters channel 1 The 44–50-MHz spectrum, which the FCC will be polarized as “vertical” or “horizontal” sig- assigned to land-mobile and two-way radio service nals that can be distinguished by a customer’s an- in 1948. Hence, VHF TV station channels start with tenna. With only slight modification, a cellular vision channel 2. microwave receiving antenna can be converted so it channel capacity Refers to the number of channels a will transmit signals back to the base antenna. This cable TV system can handle simultaneously. would give cellular vision interactive capability. channel coding Data encoding and error correction center frequency blue, SECAM 4,250.000 kHz. techniques to protect the integrity of data being center frequency red, SECAM 4,406.000 kHz. transported through a channel. Typically used in center up An instruction to place an image in the channels with high bit error rates, such as terrestrial middle of an area, such as a TV screen. and satellite broadcast and videotape recording. centered sweep A variant of line sweep with the high- Channel F Video Game System One of the first video est or lowest frequency in the center of TV line (ef- games to introduce programmability with a large fectively a double sweep), hence the small variations selection of game cartridges. Introduced by Fairchild of the frequency response at this central point are in 1976, Channel F had a short-lived career after more visible. selling a few hundred thousand systems. The com- central control room Area in the TV center dedicated pany decided to abandon the game a short time to routing and switching functions. Syn.: CCR; mas- after its inception. Then, in 1982, Zircon took over ter control room; MCR. the Channel F inventory and brought out a revised ceramic microphone See Piezoelectric microphone. version, Channel F II. certificate of compliance The FCC approval that must channel flashback This function makes it possible be obtained before a cable system can carry TV to instantly switch between two selected TV chan- broadcast signals. nels at the touch of a button on the remote con- C-format VTR An industrial machine with 1" tape troller. This button returns to the previously viewed format used by professionals. Introduced in the channel. 1970s, the C-format VTR is aimed to replace the 2" channel index An advanced TV set or VCR feature machines in use since the development of VTRs in that displays every channel in the tuner memory. 1956. The C-format, with its two quality audio chan- Channel index, or channel search as it sometimes is nels and the addition of Dolby noise reduction, called, accomplishes this by showing a consecutive brought forth a potential for improved sound. sequence of images, in the form of freeze frames, CG Character Generator. along the side and bottom of the screen while the CGA . The original low-resolu- main picture appears on screen in a larger format. tion color standard for IBM-compatible microcom- Advances in digital technology have made this fea- puters, introduced in 1981. The CGA is capable of ture, along with others, possible. several character and graphics modes. It can be used channel labeling A TV feature that permits the viewer to turn a TV set into a monitor. CGA was super- to enter the identification letters of an area network ceded by EGA, VGA, XGA, and SVGA. into a channel/time display. For instance, ABC, CNN CGMS-A Copy Generation Management System – or HBO can be listed on screen along with the chan- Analog (CGMS-A). See EIA-608. nel number and time each time that display mode is chain A network of radio, TV, radar, navigation, or pressed. other similar stations connected by special telephone channel lock A feature found on some TV sets that lines, coaxial cables, or radio relay links so all can allows one channel to be locked with access only operate as a group for broadcast or communication via a private code. The channel lock is primarily de- purposes or determination of position. signed to allow parents to prevent the authorized channel 1. Band of frequencies allocated to a specific viewing of certain channels by children. Once locked, use—for example, a single TV transmitter. TV bands even unplugging the set will not restore the access are subdivided into numbered channels, and the without the proper code. Some lock-out techniques standard channel width therefore determines the involve the use of conventional lock and key.

47 channel search channel search See Channel index. controlled manner. The CCD may be used for imag- channel selector A switch or other control that tunes ing, as in the solid-state TV camera, primarily in in the desired channel in a TV set. camcorders and lightweight cameras. Used also in channel strip An amp that has sufficient bandpass still video cameras. for one TV channel. Used in cable TV systems and charge-coupled A CCD in which fringe-area home locations to improve reception of charges are introduced when light from a scene is a single desired station. focused on the surface of the device. The image channel surfing Flipping channels on a TV set. points are accessed sequentially to produce a TV-type Channel-Compatible DigiCipher (CCDC) A proposed output signal. Also called solid-state image sensor. fully digital HDTV system, American TV Alliance charge-injection device (CID) A charge-transfer de- (ATVA). Operated with the same baseband standards vice used as an image sensor in which the image as the DSC system. points are accessed in an XY manner. The major ad- Chaoji VideoCD Another name for Super VideoCD. vantages of the CID over the CCD are its resistance chapter In videodisc terminology, one of several arbi- to blooming an image and its resistance to defects trary portions of a program into which a disc can be in the array. divided electronically. These chapters—e.g., musi- charge-transfer device (CTD) A de- cal numbers or short film subjects—can readily be vice in which discrete packets of charge are trans- located by special features on the videodisc player. ferred from one location to the next. Several different Some VDPs can be programmed to play back a se- types of CTD exist, e.g., CCDs. Applications of CTDs quence or more than a dozen chapters on one side include short-term memory systems, shift registers, of a disc. Each chapter is made up of many frames, and imaging systems. Information is usually only also easily accessible. available for serial access. chapter search See Automatic chapter search. cheater cord A special extension cord used to apply Character And Pattern Telephone Access Informa- AC power to a TV or radio receiver when the back tion Network system (CAPTAIN) A form of video- cover with its protective power interlock is removed text developed in Japan and operated through the for servicing. public switched telephone network. Displays are on Chebyshev filter A constant-k filter that achieves a TV set. It is interactive. sharp frequency cutoff at the expense of amplitude character generator (CG) 1. In TV receiver, a built-in ripple in the passband. See also Filter. device that electronically displays letters, numerals check disc, CD and CDV players See Test disc. and other symbols on the video screen (e.g., in tele- checkerboard [test pattern] Test pattern in a form of text or videotex mode). 2. A professional/industrial several bands with alternating white and black device designed to produce electronic letters and boxes. This pattern is useful to test geometry, regis- numerals by way of a specially designed keyboard. tration, medium and low frequency distortions. It is basically used for titling and graphics as well as checkerboard assembly In video editing, a for special key and fade effects. Broadcast-type units nonsequential method of auto assembly in which offer such advanced features as anti-aliasing, and the computerized editing system records all edits many fonts including italic, drop shadows, outlines, from the videotape playback reels currently in use, autosizing, embossing and bevels. Some home video leaving gaps to be filled later by subsequent reels. cameras and VCRs have built-in character genera- Also called B-mode assembly. tors. See also Video effect titler. checksum An error-detecting scheme that is the sum character sizing Refers to a generally standard fea- of the data values transmitted. The receiver com- ture of an industrial/professional character genera- putes the sum of the received data values and com- tor designed to create electronically or digitally pares it to the transmitted sum. If they are equal, various sizes and types of letters, numbers and the transmission was error-free. symbols. cherry picker Motorized high-angle camera crane po- character space In videotex, the space on a screen sition with an operator bucket. display occupied by a character or graphic symbol. chinese Referring to horizontal flaps on TV, film, or charge image The pattern of electrical charges on other lamps. the target surface of a camera tube that results from chip chart Standard black and white scale test chart the optical-image input and which, when scanned, for video camera alignment. Consists of two sets of gives rise to the picture-signal output from the tube. horizontal gray scales. Also called chipchart, crossed charge-coupled device (CCD) A form of light-sensi- gray scale. tive microprocessor that converts an image into an chopper A device that interrupts a current or beam of electrical flow. This charge-transfer device consists light or IR radiation at regular intervals, to permit of an array of MOS suitably designed so amplification of the associated electrical quantity or that they are coupled and therefore charges can be signal by an AC amplifier. moved through the semiconductor substrate in a chopper power supply A pulse-width-modulated

48 chroma keying

(PWM) chopper regulated power supply working like chroma blanking See Chrominance blanking. the horizontal deflection systems in many modern chroma burst Color burst. TV sets. The chopper power supply may consist of a chroma control 1. The control that adjusts the ampli- low-voltage bridge circuit providing voltage tude of the carrier chrominance signal fed to the to the primary winding of the chopper transformer. chrominance demodulators in a color TV set, to The dc voltage via the chopper transformer is con- change the saturation or vividness of the hues in nected to the chopper transistor. Was first used in the color picture. When in its zero position, the re- Japanese TV chassis. ceived picture becomes black and white. Also called chroma 1. Indication of degree of color saturation. color control and color-saturation control. 2. On Two parameters together define any color in the vis- color processors, process amplifiers, etc., a feature ible spectrum. One of these describes the dominant designed to modulate the color intensity of the video hue. This is the pure spectral color, or wavelength, signal. When the chroma control is tuned up, the which when mixed with white light produces a color intensity of the colors is increased and they become equivalent to the sample color. The second param- more vivid; when the knob is turned down, the in- eter indicates the amount of white light that has to tensity is decreased and the colors develop a pastel- be added to obtain this color match. A color that like quality. The chroma control, which is similar to requires no white to be added is a pure spectral color the chroma control of a TV set, differs from the burst and is said to be saturated. As white light is added phase control (also located on these signal proces- to a spectral color, it becomes paler and desaturated. sors) that adjusts color tint rather than intensity. 2. The dimension of the Munsell system of color that chroma crawl See Cross-luminance. corresponds most closely to saturation, which is the chroma crawl free system See CCF system. degree of vividness of a hue. Chroma is frequently chroma decoder A video processor designed to de- used, particularly in English works, as the equiva- code a composite video signal into its red, green lent of saturation. Also called Munsell chroma. See and blue components. Used chiefly by profession- also Variables of perceived colors. 3. A boxed photo, als, the decoder is a chroma demodulator compat- art, or graphics, relevant to a news item, that ap- ible with RGB monitors, video projectors, chroma pears on a TV screen next to the newscaster. Some- keyers, etc. times the photo or art is shown behind the chroma demodulator After the NTSC or PAL video newscaster, projected by means of a rear projection signal makes its way through the Y/C separator, the or chromakey system. colors must be decoded, which is what a chroma chroma amplitude modulation See Chroma signal- demodulator does. It takes the chroma output of to-noise. the Y/C separator and recovers two color difference chroma bandpass filter In a NTSC or PAL video sig- signals (typically I and Q or U and V). With the nal, the luma (black and white) and the chroma information and color difference signals, the video (color) information are combined together. If you system can figure out what colors to put on the want to decode an NTSC or PAL video signal, the display. luma and chroma must be separated. The chroma chroma key tracking A digital effect that compresses bandpass filter removes the luma from the video sig- the signal from a video source into the available nal, leaving the chroma relatively intact. This works chroma key window. reasonably well except in images where the luma chroma keying Also chromakeying. 1. The electronic information and chroma information overlap, mean- introduction of a color background into a scene; pro- ing that we have luma and chroma information at cess differs from black and white keying because the same frequency. The filter can’t tell the differ- the presence of color makes it possible for the op- ence between the two and passes everything within erator of the keying unit to introduce the background a certain area. If there is luma in that area, it is passed by adjusting the color values. See also Genlock. 2. through too, which can make for a funny-looking The keying in of an object against an established picture. Next time you’re watching TV and some- background—two images fused together electroni- one is wearing a herringbone jacket or a shirt with cally. A blue-green background against an object thin, closely spaced stripes, take a good look. You placed for keying against another scene is called may see a rainbow color effect moving through that chroma key blue. To produce this effect, the subject area. What’s happening is that the chroma demodu- is placed in front of a blue background. The cam- lator thinks the luma is chroma. Since the luma isn’t eras are then connected to a SEG with a chromakeyer chroma, the video decoder can’t figure out what that automatically switches the subject/key camera color it is and it shows up as a rainbow pattern. This to the background camera each time the camera problem can be overcome by using a comb filter. beam “sees” blue. There are different types of chroma bar Test signal in a form of color subcarrier chroma keying, such as upstream and downstream modulated by a bar signal, usually on gray level chroma keying, each using various combinations of pedestal. cameras and backgrounds.

49 chroma matte chroma matte See Linear chroma-key. usually a solid blue or green drape or screen. Broad- chroma noise See Chrominance noise. cast TV studios use chroma-keys to create the illu- chroma oscillator A used in color TV sion of a weather forecaster standing in front of a sets to generate a 3.579545- or 4.433619-MHz wall-sized satellite photo. The forecaster is actually (NTSC, PAL) signal for comparison with the incom- standing in front of a colored screen, while a video ing 3.579545- or 4.433619-Mhz chrominance-sub- engineer, working in a booth out of the camera’s carrier signal being transmitted. Also called view, uses a chroma-key and switcher to replace the chrominance-subcarrier oscillator, color oscillator, video image of the colored screen with the image and color-subcarrier oscillator. of a satellite photo. chroma phase modulation noise See Chroma chroma-key blue See Chroma keying. signal-to-noise. chromatic Relating to color. chroma ramp Test signal in a form of color subcarrier chromatic aberration 1. Defect of a lens appearing modulated by a ramp signal; i.e., the chroma ampli- as colored fringes around the image, resulting from tude rises linearly along the TV line. This signal is the material of the lens having different refractive usually on a gray level pedestal. Syn.: chroma indices for different colors of light, so that the blue sawtooth. rays come to a focus at a different point from the chroma sawtooth See Chroma ramp. red rays. This defect is reduced in achromatic lenses. chroma signal-to-noise The amount of interference 2. An electron-gun defect that causes enlargement influencing either the color saturation or the hue and blurring of the spot on the screen of a CRT be- within the picture. There are two types of chroma cause electrons leave the cathode with different ini- noise. Chroma amplitude modulation applies to color tial velocities and are hence deflected differently by saturation and appears as minor changes in color the electron lenses and deflection coils. strength, especially in large blocks of a particular chromatic color See Variables of perceived colors. color. The effect within the color takes on a mottled chromatic dispersion One of the mechanisms that pattern. The second type, chroma phase modula- limits the bandwidth of optical fibers by producing tion noise, is manifested by traces of different col- pulse spreading because of the various colors of light ors from that of the original. Both types of chroma traveling in the fiber. Different wavelengths of light noise subtract from the fine detail and purity within travel at different speeds. Since most optical sources the color signal that is reproduced on the TV screen. emit light containing a range of wavelengths, each Chroma signal-to-noise is measured in dB; the higher of these wavelengths arrive at different times and the number, the sharper and more detailed the color thereby cause the transmitted pulse to spread as it picture. See also Color response. travels down the fiber. Chromatic dispersion affects chroma trap In a NTSC or PAL video signal, the luma both single-mode and multimode fibers, and it is (black and white) and the chroma (color) informa- the principal bandwidth limitation for single-mode tion are combined together. If you want to decode fibers. the video signal, the luma and chroma must be sepa- chromaticity The color quality of light that can be rated. The chroma trap is a method for separating defined by its chromaticity coordinates. It is an ob- the chroma from the luma, leaving the luma rela- jective term for the definition of the characteristic tively intact. How does this work? The NTSC or PAL of a color in colorimetry, corresponding to the sub- signal is fed to a trap filter. For all practical purposes, jective qualities of hue and saturation. Chromaticity a trap filter allows some types of information (actu- depends only on hue and saturation of a color, not ally certain frequencies) to pass through but not oth- on its luminance (brightness). Chromaticity applies ers. The trap filter is designed with a response to to all colors, including shades of gray, whereas remove the chroma so that the output of the filter chrominance applies only to colors other than grays. only contains the luma. Since this trap stops chroma, chromaticity coefficient Measure of the purity of a it’s called a chroma trap. The sad part about all of color. Often arbitrary scales are quoted for practical this is that not only does the filter remove chroma, work. it removes luma as well if it exists within the region chromaticity coordinate One of the two coordinates where the trap exists. The filter only knows ranges (x or y) that precisely specify the exact identity or and, depending on the image, the luma informa- chromaticity of a color on the CIE chromaticity dia- tion may overlap the chroma information. The filter gram. Also called color coordinate and trichromatic can’t tell the difference between the luma and coefficient. chroma, so it traps both when they are in the same chromaticity diagram System of representing colors range. This means that the picture is degraded some- in problems of colorimetry as points on a two-di- what. Using a comb filter for a Y/C separator is mensional diagram whose coordinates may be em- better than a chroma trap or chroma bandpass. ployed in calculation, generally in the form known chroma-key A device that permits one video image to as the . The most common version is replace another video image of a particular color, the CIE chromaticity diagram used in color TV.

50 chroming

chromaticity flicker Flicker in a color TV set caused ponents remaining after the luminance signal is re- by fluctuation of chromaticity only. moved, from a full-color signal at the transmitter. A single-gun color picture tube that has chrominance reversal See Image reversal. color phosphors deposited on the screen in strips chrominance signal The color component of the com- instead of dots. The R,G, and B color signals are ap- posite baseband video signal assembled from the I plied in sequence to the single grid of the tube as and Q portions (NTSC) or U and V (PAL). Phase angle the beam is deflected to the correct color strip by of the signal represents hue and amplitude color horizontal grid wires adjacent to the screen. Also saturation. called Lawrence tube. chrominance staircase Test signal in a form of color chrominance (In video, the terms chrominance and subcarrier modulated by staircase signal; i.e., the chroma are commonly (and incorrectly) inter- chroma amplitude rises in discrete steps along the changed.) 1. The color portion of the video signal. TV line. This signal is usually on a gray level pedes- Chrominance includes hue and saturation informa- tal. Syn.: multi-level chroma bar. tion but not brightness. Low chroma means the color chrominance subcarrier The 3.579545- (NTSC), picture looks pale or washed out; high chroma 4.433618- (PAL), or 4.406-/4.250-MHz (SECAM, R- means the color is too intense, with a tendency to Y/B-Y) carrier (SECAM — two carriers) whose modu- bleed into surrounding areas. Black, gray and white lation sidebands are added to the black and white have a chrominance value of 0. Brightness is referred signal to convey color information in a color TV set. to as luminance. The chrominance signal is modu- The chrominance subcarrier is transmitted lated onto a 4.43-MHz carrier in the PAL TV system unmodulated in the form of color bursts that are and a 3.58-MHz carrier in the NTSC TV system. 2. used for synchronizing purposes in the receiver. Also The difference between any color and a specified called chrominance carrier, color carrier (deprecated), reference color of equal brightness. In color NSTC color subcarrier (deprecated), and subcarrier. TV, this reference color is white, having coordinates chrominance tube See Color dissector tube. x=0.310 and y=0.316 on the chromaticity diagram. chrominance vector In a color TV signal, the finite chrominance bandwidth Chrominance-channel mathematical vector whose angle represents the hue bandwidth. and whose length represents saturation. The refer- chrominance blanking Blanking of chrominance sig- ence frequency burst gives the necessary phase in- nal. Syn.: chroma blanking. formation. chrominance carrier Chrominance subcarrier. chrominance/luminance delay inequality In video, chrominance channel 1. That part of the frequency an effect caused by the color and black and white spectrum of a color transmission containing chromi- signals being recorded separately on the tape or dif- nance information. 2. Any path that is intended to fering luminance and chrominance filtering charac- carry the chrominance signal in a color TV system. teristics in the system, resulting in colored edging or chrominance demodulator A demodulator in a color fringing around objects. TV receiver for deriving the I and Q components of chrominance-carrier reference A continuous signal the chrominance signal and the chrominance-sub- that has the same frequency as the chrominance carrier frequency. Also called chrominance-subcar- subcarrier in a color TV system and fixed phase with rier demodulator. respect to the color burst. This signal is the refer- chrominance modulator A modulator used in a color ence to which the phase of a chrominance signal is TV transmitter to generate the I and Q components compared for modulation or demodulation. In a of the chrominance signal from the video-frequency color receiver it is generated by a crystal-controlled chrominance components and the chrominance sub- oscillator. Also called chrominance-subcarrier refer- carrier. Also called chrominance-subcarrier ence, color-carrier reference, and color-subcarrier modulator. reference. chrominance noise Refers to a particular kind of video chrominance-channel bandwidth The bandwidth interference that affects color signals in the form of of the path intended to carry the chrominance sig- temporary traces of color aberrations. Visible as ran- nal in a color TV system. Also called chrominance domly colored spots on TV picture. Chrominance bandwidth. noise differs from luminance noise that affects both chrominance-subcarrier demodulator Chrominance black and white and color signals. Also called chroma demodulator. noise; color noise. chrominance-subcarrier modulator Chrominance chrominance phase switching See SECAM chromi- modulator. nance phase switching. chrominance-subcarrier oscillator Chroma chrominance primary The nonphysical color repre- oscillator. sented by either the I and Q chrominance signal com- chrominance-subcarrier reference Chrominance- ponent in a color TV system. These chrominance carrier reference. signals are chosen to be electrically convenient com- chroming A method of producing a special effect on

51 chromium dioxide

a videotape recording. A videotape is recorded nor- circuit The combination of a number of electrical de- mally and then rerecorded onto another tape. The vices and conductors, when connected together to recorded signals from the original tape have neigh- form a conducting path, fulfil a desired function such boring pixels electronically aggregated to artificially as amplification, filtering, or oscillation. A circuit may reduce the resolution of the picture. Chosen sec- consist of discrete components or may be an inte- tions of the picture may also have the color elec- grated circuit (IC). Some circuits, such as CCDs, can tronically altered to give the desired effect. only be produced in integrated form. chromium dioxide One of the coatings available in circuit breaker The breaker that may work in place of the composition of videotape. It is magnetically sen- the line fuse to open when an overload is found in sitive and used mostly on Beta tapes. The VHS for- the TV circuits. Some horizontal output stages have mat generally utilizes ferric oxide. a separate circuit breaker. chromostereoscopy Part of a three-dimensional TV circular polarization Electromagnetic waves whose system employed in Japan but developed in Califor- electric field uniformly rotates along the signal path. nia. Chromostereoscopy uses a technique in which Broadcasts used by INTELSAT and other international red-colored objects appear closer than blue-colored satellites use circular, not horizontally or vertically ones, thereby giving the impression of depth. The polarized, waves as are common in North American process is compatible with 2-D or conventional TV and European transmission. broadcasting. But for a full, 3-D effect, the viewer circular zone plate A zone plate pattern (circular or needs special glasses. elliptic) with lowest spatial frequency in the center CID Charge-injection device. and uniform rise of spatial frequency along any ra- CIE Commission Internationale de I’Eclairage. French dius, so that the spatial frequency is directly propor- acronym for the International Illumination Commis- tional to the distance from the center. Syn.: bull’s sion, an international standardization organization eye pattern; Fresnel zone plate. that issues documents defining the colorimetry of circularly polarized antenna Antenna producing a all TV systems. circularly polarized wave. In one form of circularly CIE chromaticity diagram A chromaticity diagram polarized antenna, used for TV stations, the single established as an international standard by the CIE. horizontally polarized dipole in the panel antenna is In this diagram, used in color TV, the color wave- replaced by crossed dipoles that are fed in quadra- lengths are plotted as coordinates of x and y. ture, producing a circularly polarized wave. CIF Format. A videophone ISDN circularly polarized wave An electromagnetic wave standard that is part of the CCITT’s H.261/Px64 stan- for which the electric and/or magnetic field vectors dard. This video format was developed to easily al- at a point describe a circle. low video phone calls between countries. The CIF city grade service The area closest to a TV transmit- format has a resolution of 352 x 288 active pixels ter, one of three areas of a TV station’s coverage. and a of 29.97 frames per second. It Further away from the transmitter is called A con- produces a color image of 288 noninterlaced lumi- tour, and the peripheral area is called B contour. nance lines, each containing 352 pixels to be sent CIVDL Collaboration for Interactive Visual Distance at a rate of 30 fr/s. The format uses two B channels, Learning, a collaborative effort by ten U.S. universi- with voice taking 32 Kbps and the rest for video. ties that uses dial-up videoconferencing technology Note: CIF now commonly means any 352 x 288 im- for the delivery of engineering programs. age, regardless of refresh rate. cladding 1. When referring to an optical fiber, a layer , Owned by Time Warner. A pay-TV service of material of lower refractive index, in intimate con- offered to subscribers for a monthly fee. Cinemax, tact with a core material of higher refractive index. similar to Home Box Office, offers current Hollywood 2. When referring to a metallic cable, a process of films, classics and foreign features 24 hours per day. covering with a metal (usually achieved by pressure Owned by Time, Inc.; began operation in 1980. rolling, extruding, drawing, or swaging) until a bond Cinepak A high-quality medium bandwidth compres- is achieved. sion that is not real-time but can play back in soft- cladding diameter The diameter of the circle that ware. Its 24-bit format produces high-quality video includes the cladding layer in an optical fiber. at 320 x 240 resolution and 15 frames per second cladding mode In an optical fiber, a transmission mode at a 150 Kbps data rate. A CD-ROM solution devel- supported by the cladding; i.e., a mode in addition oped a number of years ago and not a competitor to the modes supported by the core material. to more current techniques. cladding mode stripping A device for converting op- circle-in An optical effect in which a picture dimin- tical fiber cladding modes to radiation modes; as a ishes and disappears as it is replaced by a second result, the cladding modes are removed from the fi- picture that grows in a circle from the center; the ber. Often a material such as the fiber coating or jacket opposite of a circle-out. See also Iris in, Iris out. having a refractive index equal to or greater than that circle-out See Circle-in. of the fiber cladding will perform this function.

52 clock/calendar

cladding ray In an optical fiber, a ray that is confined (672/768 Kbps). Point-to-point service connects cus- to the core and cladding by virtue of reflection from tomer sites via dedicated T-1 access lines. the outer surface of the cladding. Cladding rays cor- Clearvision system (also BTA Clearvision system, BTA respond to cladding modes in the terminology of system), Broadcast Technology Association, Japan, mode descriptors. 1988. It was a single-channel NTSC-compatible EDTV clamp A circuit for ensuring constancy of the poten- system: 6-MHz channel, 525-line scanning, 59.94 tial of a particular section of a recurrent waveform. fields per second, interlace 2:1. Five changes from This is basically another name for the DC-restora- conventional NTSC practice were proposed: progres- tion circuit. It can also refer to a switch used within sive scan in the receiver display, separate luminance- the DC-restoration circuit. When it means DC res- chrominance processing in the receiver, toration, then it’s usually called “clamping.” When compensation of detail rendition in highly saturated it’s the switch, then it’s just “clamp.” Clamps are color images, adaptive emphasis of the high-fre- used to ensure that the parts of the waveform that quency components at low levels of the luminance represent black in displayed pictures are maintained signal, and higher-resolution signal sources. Aspect at a constant potential. To enable a clamp to oper- ratio: NTSC — 4:3, EDTV — 16:9. ate at the desired instants it is driven by clamping CLI Compression Labs, Inc. One of the foremost pulses synchronized with the waveform to be (compression/decompression) makers and developer clamped. of some of the first “low-bandwidth” codecs in the clamper An electronic circuit that sets the video level US. Their VTS 1.5 codec was one of the first two of a picture signal before the scanning of each line codes (the other was from NEC) to compress full- begins to ensure that no spurious electronic noise is motion video to 1.5 Mbps (T-1 speed). introduced into the picture signal from the electron- Click and drag A computer term for the user opera- ics of the video equipment. Also called DC restorer. tion of clicking on an item on-screen, using a mouse, clamping The action of the electronic clamper circuit; and dragging it to a new location. the process of resetting video signal level offset to click tuner A mechanical TV tuner that clicks into po- zero, e.g., by using the black level at the composite sition for each of the 70 available UHF channels and video back porch as a reference. Syn.: back porch the 12 VHF channels. clamping; black level clamping. cliff effect In digital television, when a receiver can no Clarke belt The circular orbital belt at 22,247 miles longer receive a viable signal. above the equator, named after the writer Arthur clinching See Windowing. C. Clarke, in which satellites travel at the same speed clip To cut off sharply. See also Film clip. as the earth’s rotation. Also called the geostationary clipper Limiter. Both black and white clippers are nor- orbit. mally used in video processing to prevent unwanted Class I time In TV, preemptible time, as opposed to signal excursions above nominal peak-white or Class II. below black. clean editing An electronic edit of a video picture clipping 1. An effect of distortion where the peaks of free of noise, distortion, or other disruption in the driven signals are chopped off. Clipping usually oc- signal when it changes from picture 1 to picture 2. curs in the amp when it is turned up too high, but it In a clean edit, the picture is instantly replaced by a can also occur in maladjusted circuits in a VCR or subsequent picture. Most camcorders provide clean TV set. 2. Any action that cuts off the peaks of a TV edits. signal. This may affect either the positive (white) or cleaner See Video head cleaner. negative (black) picture-signal peaks or the synchro- cleaning solvent The special cleaning fluid used on nizing signal peaks. video and audio heads and other elements along clipping logic A circuit used to prevent illegal conver- the tape path of a VCR . The most popular and rec- sion. Some colors can exist in one color space but ommended liquid solvent is trichlorotrifluoroethane not in another. Right after the conversion from one or Freon. This solvent is more effective than alcohol, color space to another, a color space converter might which evaporates more slowly and may leave a check for illegal colors. If any appear, the clipping residue. logic is used to chop off, or clip, part of the infor- clearline 45 A Sprint name for DS-3 service. This high- mation until a legal color can be represented. capacity point-to-point private line service transmits clip sheet A nonlinear editing term referring to the voice, data, and video at 44.736 Mbps. location of individual audio/video clips (or scenes). clearline fractional 1.5 A Sprint name for all-digital Also called a clip bin. private line service that transmits voice, data, and clock/calendar A video camera feature that per- video at speeds from 112/123 Kbps up to 672/768 mits the user to stamp the time or date, or both, Kbps—a fraction of a T-1, also called a DS-1. The over a video image being shot. The information is service may be ordered in 56/64 Kbps increments superimposed over the recorded image for further from two channels (112/128 Kbps) to 12 channels reference.

53 clock jitter clock jitter Undesirable random changes in clock positional control of quadruplex heads in transverse- phase. scan VTRs. Also called a close shot. clock phase deviation See Clock . closed user group (CUG) A service on a database, clock recovery The reconstruction of timing informa- videotex, or other electronic information system tion from digital data. available only to preassigned users, such as lawyers, clock-setting by TV (VCR, Sony) Sony has introduced physicians, or other professional or affinity groups. VCRs whose clocks are set automatically by TV. The closed-captioned TV A broadcast with captions on recorders use the TV signal’s vertical blanking inter- line 21 of the VBI. val (VBI), especially field 2 of line 21, which is the closed-circuit Distribution system using wires or mi- closed-caption line. PBS stations are transmitting the crowaves to connect receiving sets to transmission clock-setting signal. When the VCR is turned off, it equipment (e.g., CCTV). automatically searches through the channels until it closed-circuit television (CCTV) A TV system, other finds one that is transmitting the clock signal. than broadcast TV, that forms a closed circuit be- clock skew A fixed deviation from proper clock phase tween TV camera and receiver. CCTV has many in- that commonly appears in D1 digital video equip- dustrial and educational applications—for example, ment. Some digital distribution amplifiers handle in security systems. See X-ray television. improperly phased clocks by reclocking the output Closed Subtitles See subtitles. to fall within D1 specifications. close-up A relative determination of a camera angle close shot Closed loop drive system. of view; usually, a shot that shows the subject of a closed caption decoder A device that allows the user picture in great detail. to view conversations, narration and other sounds close-up lens A special video camera adapter lens de- from TV programs or prerecorded videotape as sub- signed for extremely close work, such as recording script on TV screens. Primarily intended for the hard- coins, stamps, insects, etc. Many recent camcorders of-hearing. It decodes an otherwise invisible signal provide macro settings to accomplish this function. and presents captions at the bottom portion of the When using either a supplementary lens or the macro screen, revealing what the performers are saying. feature built into the camera, the operator will no- Captioned subtitles are inserted on one of the lines tice that the depth of field is severely restricted. within the vertical blanking interval. CLUT Color look-up table. A service which decodes text in- CLV Constant Linear Velocity. One of the two formats formation transmitted with the audio and video sig- of the LaserVision (LV) videodisc system. CLV discs nal and displays it at the bottom of the display. See can play for up to 1 h per side but lack the many the EIA-608 specification for (M) NTSC usage of special effects features offered by the CAV format closed captioning. For digital transmissions such as of 30 minutes per side. Since the larger outer tracks HDTV and SDTV, the closed caption (CC) characters of the disc hold more information than the smaller are multiplexed as a separate stream along with the diameter inner tracks, the playing time is extended. video and audio data. It is common practice to ac- However, the 30 revolutions per second of the CAV tually embed this stream in the MPEG video bitstream speed, that matches TV’s 30 frames per second, is itself, rather than at the transport layer. Unfortu- altered, thereby eliminating such features as freeze nately there is no wide-spread standard for this frame, single frame advance and slow motion. How- closed captioning stream—each system (DSS, DVB, ever, some advanced models of laserdisc players in- ATSC, DVD) has its own solution. The practical place corporate digital memory to handle smooth freeze in MPEG to put closed captioning data is in the frames, slow motion and other special effects. user_data field, which can be placed at various fre- c-mount A standard used on many video quencies within the video stream. For DVD, it is the cameras and camcorders to permit compatibility and group_of_pictures header, which usually proceed interchangeability with other lenses by diverse manu- intra pictures (this happens about two times a sec- facturers. A typical use would be temporarily fitting ond). ASTC broadcasts, the EIA-708 data is inserted a wide angle or telephoto lens to the camera in place in the user_data field of individual picture headers of the normal one. Since almost all camcorders come (up to 60 times/sec). equipped with a zoom lens, which offers a wide closed information Videotex information that is in- range of focal lengths, the average home tended for only a restricted user audience and videographer has little need to change lenses. which can be accessed only by the use of a key CMX A trademarked, computer-interfaced video edit- (code) number. It may consist of company confi- ing system, made by Chyron Corporation, of Melville, dential information or text, data, and images sold NY, developed by a joint venture of CBS and to subscribers. The concept makes a closed user Memorex. group possible. CMYK This is a color space primarily used in color print- closed loop drive system Tape drive system that in- ing. CMYK is an acronym for Cyan, Magenta, Yel- cludes a feedback in the loop. Used for accurate low, and blacK. The CMYK color space is subtractive,

54 coded orthogonal frequency division multiplexing

meaning that cyan, magenta, yellow and black pig- foot, a 3-foot length has a total capacitance of 46.5 ments or inks are applied to a white surface to re- pF. The higher the capacitance, the more the signal move color information from the white surface to is degraded. create the final color. The reason black is used is coaxial CATV A multichannel video transmission sys- because even if a printer could put down hues of tem. In coaxial CATV systems, video signals ampli- cyan, magenta, and yellow inks perfectly enough to tude-modulate carriers with frequencies of 70 MHz make black (which it can’t for large areas), it would or higher and are multiplexed on a frequency- be too expensive since colored inks cost more than division basis. black inks. So, when black has to be made, instead coaxial connector See . of putting down a lot of CMY, they just use black. cochannel A channel in which the TV set receives two C/N (also CNR) Carrier-to-noise ratio. TV stations on the same channel. In the US, the FCC C/N threshold The C/N at threshold of visibility (TOV) has meticulously placed TV stations on the same for random noise. channel far apart. Also, the frequency of the TV sta- coarse chrominance primary The least important of tions is displaced ±10 kHz. Therefore, the separa- the two chrominance primaries in a color TV signal, tion in frequency may be as much as 20 kHz (one called the Q signal. Because its bandwidth is typi- +10 kHz, the other –10 kHz). This allows the pri- cally limited to 0.5 MHz, this signal affects only the mary TV station to be received by the TV set even larger, coarser variations in the color picture. The though there is some picture impairment caused by other primary is the fine chrominance primary or I the other station. signal, going up to 1.5 MHz. cochannel interference Interference between two coating The magnetic oxide particles on videotape, signals of the same type in the same channel. which are formed into diagonal fields of informa- Cochannel interference occurs when two TV stations tion by video heads. Beta tapes are generally coated operating on the same frequency are received at the with chromium dioxide (original Sonys were de- same location. The most common effect is “vene- signed for optimum efficiency with chrome tapes) tian blinds,” alternate black and white horizontal while VHS tapes generally are composed of ferric bars across the picture that results from the “beat” oxide. Beta tapes, when combined with cobalt, pro- between the two carriers. vide better resistance to dropout or flaking of par- codec Coder-decoder. A device to convert analog video ticles but are weaker in the area of high frequencies. and audio signals into a digital format for transmis- VHS tapes offer better frequency response, but the sion, and also to convert received digital signals back oxide composition may present a problem with the into analog. Also compression/decompression. excessive snow or distortion, especially with low- codec conversion The back-to-back transfer of an grade tapes. analog signal from one codec into another codec in coaxial A special cable designed to carry one or more order to convert from one proprietary coding scheme TV channel signals with minimum power loss and to one used by another codec manufacturer. The high video frequency transmission. Rated at 75 analog signal, instead of being displayed to a moni- ohms, this cable offers a thicker surrounding of the tor, is delivered to the dissimilar codec where it is center conductor and rejects undesirable interfer- redigitized, compressed and passed to the receiving ence. In video, a few types of coaxial cable are avail- end. This is obviously a bi-directional process. Con- able, but the RG-59 is the most popular. It has a version service is offered by carriers such as AT&T, thick coating around the center conductor for MCI and Sprint. strength and protection from interference. It is de- coded image A representation of an image in a form signed for cameras, monitors, VCRs, etc. RG-6 is suitable for storage and processing. heavier and uses a larger center conductor than RG- coded orthogonal frequency division multiplexing 59 and is considered the all-around better cable Coded orthogonal frequency division multiplexing, when using long cable lengths. The reason is that or COFDM, transmits digital data differently than there is less signal loss per 100 feet of RG-6 than 8-VSB or other single-carrier approaches. with RG-59. However, RG-6 has a higher capacitance Frequency division multiplexing means that the data per foot than RG-59, so when using short lengths to be transmitted is distributed over many carriers. of cable—less than 4 or 5 feet—the better choice is Thus, the data rate on each COFDM carrier is much really RG-59. Most F connectors are made for lower than that required of a single carrier. The RG-59. If using RG-6, the F connectors with the COFDM carriers are orthogonal, or mutually per- larger crimp barrel should be used. Cable loss is pendicular, and forward error correction (“coded”) expressed in dB at different TV broadcasting frequen- is used. COFDM is a multiplexing technique rather cies. Every 3-dB drop doubles the signal loss. Signal than a modulation technique. One of any of the loss increases at higher frequencies. Capacitance is common modulation methods, such as QPSK, 16- expressed in pF and is cumulative for the length of QAM or 64-QAM, is used to modulate the COFDM the cable. That is, if cable capacitance is 15.5 pF per carriers.

55 coder coder 1. In general: Device performing an “encod- colors (red, green and blue) and their ing” function, e.g., an analog-to-digital converter. composites. 2. Specifically: Composite color video coder, e.g., color adjustment circuitry An advanced TV feature “NTSC coder,” ”SECAM coder,” for producing com- that allows the user to modify the color tempera- posite signals from component video sources. ture of white while retaining natural skin tones of coding Representing each video signal level as a the subject. The special circuits adjust for cooler or number, usually in binary form. warmer white color temperature. coercivity Also called magnetic coercivity. In video- coloration See Microphone. tape, the ability of the particles that compose the color background generator An electronic circuit magnetic medium to be magnetized. Therefore, the used in chroma keying to produce a solid color back- higher the coercivity, the better the quality of the ground of any desired hue and saturation. tape. color balance Adjustment of the circuits that feed the COFDM See Coded Orthogonal Frequency Division three electron guns of a color picture tube to com- Multiplexing. pensate for differences in light-emitting efficiencies cogging Break-up of vertical edges caused by a dis- of the three color phosphors on the screen of the placement of the raster from one field to the next. tube. A TV receiver fault. color bar chart See Video test chart. coherent detection Syn.: synchronous detection. See color bar generating signal In video cameras. a sig- Suppressed-carrier transmission. nal produced as a set of vertical color bars. This can cold color Pale, often with a blue or green tint, as be used as a test pattern when compared to a color opposed to warm color. bar chart such as the Munsel color chip chart. By Colecovision A revised video game system introduced using this chart in conjunction with a color in 1982 by Coleco. The system had realistic and vectorscope, it is simple to determine whether the above average color graphics, 8-direction control video camera components are in good working sticks, a pushbutton keyboard and a special con- order. troller for changing the speed as well as the action color-bar generator A signal generator that delivers during the game. An optional adapter permitted to the input of a color TV receiver the signal needed playing the Atari VCS game cartridges. to produce a color-bar test pattern on one or more collaboration A multimedia term. Collaboration in- channels. volves two or more people working together in real- color bars A test pattern of specially colored vertical time, or in a “store-and-forward” mode. Applications bars used as a reference to test the performance of enable a group of people to collaborate in real time a color TV and transmission path. Peak white and over the network using shared screens, shared black level bars are also provided. The R,G and B whiteboards, and video conferencing. Collaboration bars correspond to the system primary colors. The can range from two people reviewing a slide set on other three are yellow (R+G), magenta (R+B) and line to a conference of doctors at different locations cyan (G+B). Colors that are 100% saturated as well sharing patient files and discussing treatment options. as having 100% luminance are very abnormal. To collector Anode which collects the secondary elec- avoid overload conditions at the transmitter, there- trons emitted from the mosaic of an iconoscope or fore, it is normal to transmit the color bars with re- similar device. duced luminance. The test pattern is used to check collimation Process of setting up a lens system to pro- whether a video system is calibrated correctly. A duce a parallel beam from a source emitting rays video system is calibrated correctly if the colors are which diverge or converge. Collimators, which pro- the correct brightness, hue, and saturation. This can duce these parallel beams, play a part in many pieces be checked with a vectorscope. of optical equipment such as relay systems in TV color-bar test pattern A test pattern of different col- color cameras. Collimators are also used for check- ors of vertical bars, used to check the performance ing the calibration and performance of lenses. of a color TV set. collision The result of two devices trying to use a shared color breakup Momentary separation of a color pic- transmission medium simultaneously. The signal ture into its primary components as a result of a interference requires both devices to retransmit the sudden change in the condition of viewing, such as data lost due to the collision. fast movement of the head or blinking of the eyes. color A characteristic of light that can be specified in color burst In a color TV system, that portion of the terms of luminance, dominant wavelength, and pu- video waveform that sits between the breezeway rity. Luminance is the magnitude of brilliance. Wave- and the start of active video. The color burst tells length determines hue and ranges from about 400 the color decoder how to decode the color infor- nm for violet to 700 nm for red. Purity corresponds mation contained in that line of active video. By look- to chroma or saturation and specifies vividness of a ing at the color burst, the decoder can determine hue. In video, color is formed by the three primary what’s blue, orange, or magenta. Essentially, the

56 color encoder

decoder figures out what the correct color is. In correct any defects in videotape. The special circuitry, NTSC, the color burst is a short series of oscillations along with dropout compensators, noise reduction at the chrominance subcarrier frequency of and picture enhancement circuits, helps to compen- 3.579545 MHz, following most transmitted horizon- sate for any imperfections in tape manufacture and tal sync pulses. Also called burst; burst signal. design. In camcorder, an optional accessory designed color-burst pedestal The rectangular pulselike com- to allow the user to adjust white balance, correct ponent that is part of the color burst when the axis for color and add color wipe transitions between of the color-burst oscillations does not coincide with scenes. The unit may have additional features, such the back porch. Also called burst pedestal. as the capability for audio mixing and the transfer color carrier Alternate term for chrominance subcarrier. of film negative to positive video pictures. color-carrier reference Chrominance-carrier color-crawl See Moire. reference. color cycling A special process that permits dramatic colorcast A TV program broadcast in color. color changes of screen images ranging from dia- color cell See Color picture tube. grams to music-video effects. Color cycling is often color constancy In video, the continuity of color performed by professional videographers using such intensity either in a single frame or over a short range highly technical equipment as computers with spe- of time. cial computer-generated animation programs that color contamination 1. Refers to the appearance of allow for color ranges and user-definable timing. small traces of color that spill over to black and white color decoder The circuit in the video decoder that portions of a video image and detected (as unwanted uses the chroma portion of a video signal to derive color) between closely set lines in a video picture; the two color difference signals. The color decoder color contamination can distort the image. The sits right after the Y/C separator. In NTSC, the color amount of color contamination that a video camera decoder needs a reference signal that is accurately produces can be determined by the use of a black phase-locked to the color burst. If it isn’t locked well and white pattern and is measured in IREs. A smaller enough, then the color decoder can’t figure out the numerical reading represents a purer or better pic- right colors. Also called a chroma demodulator. ture. An average rating is 7 IRE. 2. Poor rendition of color decoding In broadcast TV, the transformation color in a color TV set, caused by incomplete sepa- of composite video into primary color signals (or lu- ration of color component paths. minance and color difference signals). color control Chroma control. color demodulator See chroma demodulator. color control unit An accessory connected between The number of bits per pixel. One bit per a video camera and recorder which adjusts or cor- pixel allows two colors (often black and white) to rects color temperature for both indoors and out- be displayed, two bits per pixel allow four colors, doors. The color control unit, used if no filter or three bits allow eight colors, etc. electronic system of correction comes with the cam- color difference signals The video signals (R-Y) and era, offers two advantages. It is a more flexible (B-Y) obtained by subtraction of the luminance value method of adjusting color temperature and, because Y from each of the primary color signals. There are it is a separate unit, the camera remains lighter in many scaled, matrixed and therefore different ver- weight. However, there are also a few inconve- sions of color difference signals such as: I, Q; U, V; niences. The color control unit is another piece of Pr, Pb; Cr, Cb; Dr, Db, which should not be confused equipment that has to be made off camera. with basic color difference signals. color conversion filter A colored glass disc fitted over color difference set, HDTV See SMPTE 240M the front of a lens of a video camera to change the standard. color temperature. Since the camera tube is normally color dissector tube Coloring tube; chrominance balanced for proper exposure with tungsten (indoor) tube. A CRT designed to separate a scene’s hue and light, some type of conversion is required when the saturation values into their R,G,B components for camera is used outdoors. One method is using a electronic encoding as part of the color video special orange-colored filter. However, manufactur- signal. ers have devised more sophisticated ways of cor- color-dot-crawl See CCF system. recting color temperature: built-in, behind-the-lens color edging Spurious color at the boundaries of dif- optical filters, electronic switching, etc. Also known ferently colored areas in a color TV picture; extrane- as color correction filter, conversion filter. ous colors that appear along the edges of objects, color coordinate Chromaticity coordinate. but don’t have a color relationship to those areas. color correction filter Color conversion filter. Color edging includes color fringing and color corrector Equipment for adjustment of the color misregistration. values of a color video signal. Color corrector is usu- color encoder The color encoder does the exact op- ally required for proper reproduction of images from posite of the color decoder. It takes the two color motion picture film. In VCRs, a feature that helps difference signals, such as I and Q or U and V, and

57 color encoding

combines them into the chroma signal. The color color framing TV synchronization providing synchro- encoder, or what may be referred to as the color nization of color frames, usually for post-produc- modulator, uses the color subcarrier to do the en- tion purposes. Modern VTRs do color framing coding. automatically as part of the run-in process. Lack of color encoding The transformation of primary color color framing will result in chroma flashes after in- signals (or luminance and color difference signals) sert or assemble edits on some VCRs. Syn.: color ID; into composite video. color identification; color sync. color enhancement light A special light, found on color fringing 1. Spurious chromaticity at boundaries some camcorders, designed to illuminate an area sev- of objects in a color TV picture. Small objects may eral yards in front of the camera. The small 10 W appear separated into different colors. It can be light, first introduced in 1989 by Panasonic on one of caused by a change in position of the televised ob- its camcorder models, usually provides enough light ject from field to field or by misregistration. Fring- to capture the natural colors of a particular scene. ing is particularly noticeable when a black and white color fidelity The ability of a color TV system to repro- signal is received. It is minimized using a color killer. duce faithfully the colors in an original scene. 2. Artifact of chrominance coding-decoding process color field TV field numbered with reference to the due to the limited bandwidth. It gives the appear- start of color frame. E.g., in NTSC the color frame ance of the color not precisely fitting the object de- starts with color field I and ends with the color fined by the luminance signal. field IV. color graphics The capability of a system to draw pic- color field corrector A device positioned outside a tures, create graphs, highlight text, etc., using color picture tube to produce an electric or mag- colors. netic field that acts on the electron beam after de- Color Graphics Adapter (CGA) A circuit board for flection to produce more uniform color fields. the color monitors of PCs that supplies R,G,B, and color filter A sheet of material that absorbs certain intensified (RGBI) video and composite video signal. wavelengths of light while transmitting others. Used Up to 16 colors can be formed on an RGBI TTL-com- in video cameras to compensate for wide variations patible monitor, and up to 16 shades of gray can be in lighting conditions without excessive adjustment formed on a composite video monitor. of operating controls. The spectral response of color color ID See Color framing. filters is specified by their color temperature. The color identification See Color framing. color temperatures of a typical complement of color colorimeter An instrument that measures color by de- filters are 3200 and 5600 K. These permit the termining the intensities of the three primary colors camera to switch from daylight to artificial illumina- that will give that color. tion without major readjustment of the electronic colorimetry The science of color measurement. In controls. video, the procedure of measuring color and ana- color A color dot rushing across a black and lyzing the results. Colorimetric characteristics include white telecast as seen on a color TV set. These red, such elements as wavelength and primary-color green and blue dots—or color flashes—occur when content. random noise, after being picked up by the decoder coloring tube See Color dissector tube. and matrix, reaches the picture tube. color intensity In video, the saturation of a color. The color flicker Flicker due to fluctuations of both chro- original color signal and the concentration of the maticity and luminance in a color TV receiver. electron beam determine color intensity or satura- color frame Set of several frames that begins and ends tion. If a certain color has high saturation, that color with the same SCH value (NTSC and PAL) or same is usually considered bright; if the color consists of color difference signal type (SECAM). Depending on low saturation, it is said to be dull. More recent TV the color TV system it consists of: NTSC – 2 frames sets have introduced special circuitry to improve satu- (4 fields); PAL – 4 frames (8 fields); SECAM – 2 frames ration. These models prevent the automatic color (4 fields). If chrominance phase switching is taken circuitry from oversaturating individual scenes so that into account then one SECAM color frame consists the color of objects is not emphasized to the detri- of six frames (12 fields). ment of the entire picture. Saturation differs from color frame code A code to identify alternating video hue, which refers to the shade of a color. frames involved in an edit. Color video frames have color intensity control A feature, found on some an alternating nature, which can be indicated by video processors, designed to adjust color level. This designating them as either A or B. Each frame end- increase or decrease in color intensity helps to pro- ing in an even number is defined as having the A duce rich, natural color; boost weak, faded colors; characteristic, and each frame ending in an odd num- and reduce overly bright colors. Especially useful in ber is defined as having the B characteristic. The pres- copying videotapes, color intensity control allows ence of a binary one in bit 11 of the time code word boosting color before the recording process to help indicates the presence of this A-B color frame code. prevent generation loss.

58 color picture tube colorization A process that converts black and white rect color hues. Color phase refers to the color sig- movies to color. The technique involves the use of nal in terms of its timing relationship. computers that assign pre-selected colors to indi- color phase detector The color TV receiver circuit that vidual areas or shapes of the original black and white compares the frequency and phase of the incoming film. These colors are then carried throughout the burst signal with those of the locally generated scene or sequence for the purpose of consistency. 3.579545-MHz chroma oscillator. Those film makers connected with the original work color picture signal The electric signal that represents and other critics of the process have voiced their complete color picture information, excluding all syn- protest against colorization on the grounds that it chronizing signals. In composite form it consists of tampers with the original creative talents that went a monochrome component plus a sub-carrier modu- into the making of the film. lated with chrominance information. colorizer Electronic circuitry used to generate a chromi- color picture tube A type of CRT designed to pro- nance signal in relation to the gray values of a black duce colored images in color TV. The colored image and white video signal. Each gradation of gray from is produced by varying the intensity of excitation of black to white is assigned a color value. The result is three primary colors R,G, and B. The 3-gun color an artificially, and often inaccurately, colored picture. picture tube consists of a configuration of 3 elec- color key This is essentially the same thing as chroma tron guns—the red gun, blue gun, and green gun— key. that are tilted slightly so that the electron beams color killer 1. The circuit in a color TV set to cut off intersect just in front of the screen. Each electron chrominance amplifier during reception of black and beam has an individual electron lens system of fo- white programs. 2. An electronic circuit used in a cusing and is directed towards one of the three sets VTR to suppress the 3.58-MHz color carrier frequency of color phosphors. There are several different types when a black and white tape is being shown; the of color picture tubes, the main differences being in same circuit in a black and white VTR used to sup- the configuration of electron guns and arrangement press the color carrier frequency when a color tape of the phosphors on the screen. is being played back in black and white. Without a One main type is the dot matrix tube, an example color killer, the color signal would appear in the dis- of which is the Colortron. It has a triangular arrange- played black and white picture as random noise. ment of electron guns and has the phosphors ar- color look-up table (CLUT) In digital video, a table of ranged as triangular sets of colored dots. A metal color values with any bits per pixel (bpp) format, shadow mask is placed directly behind the screen, and indexed by a pixel value of smaller value. This in the plane of intersection of the electron beams, allows display of a selected group of colors by a low to ensure that each beam hits the correct phosphor. bpp system, where the group of colors is chosen The mask acts as a physical barrier to the beams as from a much larger range (the palette) of colors rep- they progress from one location to the next and mini- resented by the bpp value used in the CLUT. mizes the generation of spurious colors by excita- color mapping The process of using a CLUT for a tion of the wrong phosphor. color display. The other main type of 3-gun color picture tube A technique for describing a color (e.g., is the slot matrix tube, which has the electron guns RGB). arranged in a horizontal line. The phosphors are ar- color modulator Color encoder. ranged as vertical stripes on the screen and the color noise Random interference in the video. Because shadow mask is replaced by an aperture grille of of reduced color bandwidth or color subsampling, vertical wires. This type has advantages in focusing color noise appears as relatively long streaks of in- the beams but has a smaller field of view than the correct color in the image. triangular arrangement of electron guns. color oscillator Chroma oscillator. The is a type of color picture tube that color phase The proper timing relationship within a has certain advantages over 3-gun tubes. It has a color signal. Color is considered to be in phase when single electron gun with three cathodes aligned hori- the hue is reproduced correctly on the screen. In the zontally, an aperture grille, and vertical striped phos- NTSC and PAL systems, color phase is the difference phors. The cathodes are tilted towards the center so in phase between a chrominance signal (I or Q) and that the electron beams intersect twice, once within the chrominance-carrier reference in a color TV re- the electron lens focusing system and once at the ceiver. Also called tint. See Hue. aperture grille. This allows a single electron lens sys- color phase alternation (CPA) The periodic chang- tem to be used for all three beams, thus requiring ing of the color phase of one or more components fewer components. The system is therefore much of the chrominance subcarrier between two sets of lighter and cheaper than the 3-gun tubes. The ef- assigned values after every field in a color TV fective diameter of the electron lens is greater and system. sharper focusing of the three beams is therefore color phase correction That which produces the cor- possible.

59 colorplexer

Microconvergence of the electron beams as they +/-2% and the hue is +/-2 degrees. On a vectorscope, traverse the screen increases with the distance from if you’re in that range, you’re studio grade. the center of the screen. In the horizontal arrange- color purity magnet A magnet on the neck of a color ment of electron guns, microconvergence only oc- picture tube, to improve color purity by changing curs along the line direction rather than in both line the path of the electron beam. and field directions as occurs in the triangular con- color recording Two methods have been used in the figuration. The 3-cathode arrangement of the recording of color signals onto tapes. One is called Trinitron, however, allows a greater lens aperture the direct method, and the other is called the color- than in the 3-gun arrangement. The diameter of the under method. In the direct method, the NTSC sig- electron tube for a given screen size is also reduced nal is coupled to the FM modulator, just as is done in the Trinitron. CRTs of the Trinitron type can be used with the black and white signal. The color signal for applications where multiple electron beams are consists of an AC, 3.58-MHz signal on a DC level. required; the angle of the tube may be increased to The DC portion of the signal determines, through give a relatively wide-angle color picture tube and the FM modulation action, the carrier frequency for hence a relative reduction in the overall size of color the video and color signal modulation. The AC por- TV sets. The color quality and definition of the pic- tion of the signal produces sidebands of this FM ture on the screen of a picture tube depends greatly carrier. The color signal can be easily demodulated on the dynamic convergence of the beams and the as with the black and white signal. One problem size of the color cell. Scanning of the three electron with this direct method is that the sidebands on de- beams across the screen is effected by a system of modulation can cause interference beats in the pic- deflection coils to which sawtooth waveforms are ap- ture. The color-under method separates the color plied in synchronism with the transmitter, the flyback and luminance signals from the incoming signal. signal being blanked. Extra convergence coils are fre- Each portion of the total signal is processed indi- quently used to ensure the correct convergence of vidually. The color is heterodyned down from 3.58 the beams at the shadow mask or aperture grille. A MHz to a lower carrier frequency and recorded di- system of dynamic focusing is also used in which the rectly onto tape. The FM carrier is used as a bias voltage applied to the convergence coils is varied au- that is amplitude-modulated. During playback in this tomatically according to the relative position of the method, the color carrier is recovered and hetero- spots on the screen; this minimizes microconvergence. dyned back up to 3.58 MHz. The size of the color cell is the smallest area on the color registration The accurate superimposing of the screen that includes a complete set of the three pri- R,G, and B images used to form a complete color mary colors. A smaller color cell is available with hori- picture in a color TV receiver. zontally aligned electron guns or cathodes than is color response 1. The sensitivity of a device to differ- possible in the triangular configuration. ent wavelengths of light. 2. In videotape, the ability colorplexer Encoder; the section of a color TV trans- of the tape to reproduce color signals. Various tapes mitter that accepts the R, G and B separation sig- respond differently to color signals. Those of poorer nals and produces a complete encoded video signal. quality display signs of color smear, also known as Composite sync signals are also added. chroma signal-to-noise. Both terms refer to the ability color primaries The R,G, and B primary colors that of the tape to accurately reproduce color. are mixed in various proportions to form all the other color sampling rate The number of times per second colors on the screen of a color TV receiver. that each primary color is sampled in a digital video color processor A device designed to enhance a pic- system. ture by individually controlling brightness, color tint color saturation The degree to which a color is mixed and intensity, and the skin tones. Among its many with white. High saturation means little or no white, uses, it can color-correct duplicate tapes while re- as in a deep red color. Low saturation means much cording or during playback. It is similar to a proc white, as in light pink. The amplitudes of the I/Q, U/V, amp but without its number of corrective steps or and Cb/Cr signals determine color saturation in a color special effects. TV receiver. Also called saturation. color purity Absence of undesired colors in the spot color saturation control Chroma control. produced on the screen by each beam of a TV color color separation overlay (CSO) A technique used in picture tube. This term is used to describe how close color TV for superimposing part of one scene on a color is to the theoretical. For example, in the Y’UV another. When a particular color, such as blue, oc- color space, color purity is specified as a percentage curs in one scene viewed by a camera, the output of saturation and +/-q, where q is an angle in de- of another camera filming a different scene is auto- grees, and both quantities are referenced to the color matically switched in to replace the areas of the cho- of interest. The smaller the numbers, the closer the sen color in the original picture. All other colors are actual color is to the color that it’s really supposed transmitted normally from the first camera. The tech- to be. For a studio-grade device, the saturation is nique is widely used for achieving special effects.

60 color set, HDTV. See SMPTE 240M standard. color decoder. In the color encoder, a portion of the color shift In video, the extent to which colors hold color subcarrier is used to create the color burst, their hue after being recorded in a particular for- while in the color decoder, the color burst is used to mat. Color shift may occur within a single format. reconstruct a color subcarrier. For example, a top-of-the-line VHS machine often color-subcarrier oscillator Chroma oscillator. displays less color shift than one of the economy color-subcarrier reference Chrominance-carrier models. In addition, the recording speed affects color reference. shifting; SP normally provides better color rendition color subsampling The technique of using reduced than does EP, or 6-hour recording mode. Also, view- resolution for the color difference components of a ers who participated in comparison tests of differ- video signal compared to the luminance component. ent formats (LaserVision, 8mm, Super-Beta, ED-Beta, Typically the color difference resolution is reduced VHS, S-VHS, Hi8), conducted by a leading video by a factor of two or four. magazine, selected LaserVision as having color sync 1. The reference and control signal that is the least color shift. required to record and play back color—designated color sidebands The signals that extend for about by the figure 3.58 MHz. This number becomes the 0.5 MHz above and below the 3.579545-MHz color reference point to which VCRs lock in for color. 2. subcarrier signal, which is broadcast as part of a color See Color framing. TV signal. The color sidebands contain picture color sync burst A “burst” of 8 to 11 cycles in the chrominance information, which is removed from 4.43361875 MHz (PAL) or 3.579545 MHz (NTSC) the color subcarrier by a synchronous detection pro- color subcarrier frequency. This waveform is located cess in receivers. on the back porch of each horizontal blanking pulse color signal Any signal that controls the chromaticity during color transmissions. It serves to synchronize values of a color TV picture, such as the color pic- the color subcarrier’s oscillator with that of the trans- ture signal and the chrominance signal. mitter in order to recreate the raw color signals. Color Slide Theater A TV system developed by color table A table of color values that are displayed Sylvania in 1968 to show slides on the TV screen. A in an indexed color system. color console TV had a built-in Carousel slide color television A TV system that produces a colored projector which projected slides onto the TV screen. image on the screen of a color picture tube. An ad- The console also contained an audio tape recorder ditive color reproduction process is used on the for presenting an accompanying narrative while the screen whereby three primary colors — red, green, slides were advanced by remote control. The model and blue — are combined by eye to produce a wide remained on the market for only one year. variety of colors. The apparent color of the image color space A mathematical representation for a color. depends on the relative intensities of the three pri- No matter what color space is used—RGB, YIQ, YUV, mary colors and a properly adjusted color TV receiver etc.,—orange is still orange. What changes is how approximates the original colors of the transmitted you represent orange in an imaging system. For ex- scene. ample, the RGB color space is based on a Cartesian Three separate video signals are produced by a coordinate system and the HSI color space is based color TV camera. These signals are used to produce on a polar coordinate system. a composite signal that is broadcast and received by Colorstream The name Toshiba uses for the analog a color receiver. The receiver extracts the original YUV video interface on their DVD players and tele- video information from the composite signal and visions. If it also supports progressive (noninterlaced) modulates the intensities of the three electron beams video, it is called Colorstream Pro. of the color picture tube in order to excite the Colorstream Pro See Colorstream. appropriate red, green, or blue phosphors on the color-striping An anti-copying process designed to screen. prevent VCR and DVD users from copying video- The composite signal transmitted in color TV discs or pay-per-view cable broadcasts. This tech- needed to be compatible with the large number of nique is also added to the pressings of videodiscs so black and white receivers in use. It is therefore com- that a videotape which has copied the material will posed of two parts: the luminance signal and chromi- play back an image filled with rotating color bands. nance signal. The luminance signal contains color subcarrier Alternate term for chrominance sub- brightness information. It is obtained by combining carrier. The carrier wave on which the color signal the outputs of the three color channels and is used information is impressed; contains the color burst for amplitude modulation of the main picture car- and alternating phase color information, usually off rier frequency. This produces the black and white to 3.58 MHz. For (M) NTSC the frequency of the image. The color information is contained in the color subcarrier is about 3.58 MHz (3.57954 MHz) chrominance signal, which is transmitted using a and for PAL (B, D, G, H, I) it’s about 4.43 MHz. The subcarrier wave at a frequency chosen to cause the color subcarrier is used to run the color encoder or least interference on a monochrome set. The chromi-

61 color television signal

nance signal is obtained by combining, in a color sophisticated—and costly—cameras may have a coder circuit, fixed specified fractions of the sepa- switch with as many as four settings: incandescent rate video signals into sum and difference signals. indoor lighting (3200 degrees K), fluorescent light- Two quadrature components of the chrominance ing (4500 degrees K), sunlight (5200 degrees K) and signal are produced and used for amplitude modu- cloudy bright (6000 degrees K). Color temperature lation of the chrominance subcarriers. The subcarriers control, which corrects the camera for various kinds are suppressed at transmission. The original infor- of light, is different from white balance control, which mation is extracted from the chrominance signal in helps to set or establish colors, but both may be used the color decoder in the receiver. The frequency over- together to adjust for natural color rendition. lap is the range of transmitted frequencies that are color tint control A function on older TV receivers common to both the luminance and chrominance designed to adjust color when a channel is changed. channels. Different channels transmit colors that are always The composite color signal contains the lumi- consistent. Some of the reasons for this diversity in- nance and chrominance signals; it also contains syn- clude the frequent adjusting of the transmitter for chronizing pulses for line and field scans as well as color balance, the individual channel’s deliberate color burst signal. The color burst establishes a phase decision to enhance its color in the hopes of attract- and amplitude reference signal that is used to de- ing more viewers, and the peculiar whims of station modulate the chrominance signal. In color receivers engineers whose personal visual and esthetic tastes the chrominance circuits are disabled by the color affect the color that is telecast to home TV sets. As killer during weak signal or black-white TV program a result, the TV viewer often has to adjust the color reception. This ensures that only luminance infor- tint control when he or she switches channels. Some mation reaches the tube and prevents color fring- more sophisticated TV receivers provide a memory ing on the image. chip which stores the proper tint adjustment for each color television signal The entire signal used to trans- channel, thereby automatically making corrections mit a full-color picture. It consists of the color pic- as the viewer changes channels. ture signal and all the synchronizing signals. color transient improvement A circuit for color dif- color temperature The temperature of a black-body ference signals with transient detecting, storage and radiator that produces the same chromaticity as the switching stages resulting in faster transients of color light under consideration. Color temperature is mea- difference signals. sured in degrees Kelvin. Measurement of the color color transmission The transmission of a signal wave quality of a light source, being the temperature on for controlling both the luminance and chromaticity the Kelvin scale at which a black body must be op- values in a picture. erated to give a color matching that of the source in color triangle Method of representing colors as points question. In this definition, a black body is a tem- within a triangle to permit the calculation and speci- perature radiator whose radiant flux in all parts of fication of a number of aspects of colorimetry. The the spectrum is the maximum obtainable from any three corners of the triangle represent three color temperature radiator at the same temperature. It is stimuli of R,G, and B lights, whose wavelengths are called a black body because it absorbs all the radi- defined, and any color which can be produced by ant energy that falls upon it. If a TV has a color tem- mixing these three stimuli in different proportions perature of 8,000 degrees Kelvin, that means the can be represented by a point within the triangle. whites have the same shade as a piece of pure car- The position at which a mixture of the three stimuli bon heated to that temperature. Low color tempera- gives the effect of white is known as the white point. tures have a shift towards red; high color Pure spectral colors fall outside the bounds of the temperature have a shift towards blue. The stan- triangle since they cannot be absolutely matched dard for (M) NTSC in the United States is 6,500 de- by mixtures of three stimuli. grees Kelvin. Thus, professional TV monitors use a Colortron See Color picture tube. 6,500-degree color temperature. However, most color-under method A process employed by all home consumer TVs have a color temperature of 8,000 video recorders to record color and black and white degrees Kelvin or higher, resulting in a bluish cast. information separately. The color portion of a video By adjusting the color temperature of the TV, more signal is converted to a lower frequency while the accurate colors are produced, at the expense of pic- black and white part of the video image is left un- ture brightness. In color TV, to avoid color distor- changed. These two signals are rejoined during play- tion, the color temperature of the lighting of the back. But since the union is never exact, fringing, scene must be matched to that of the system which erratic color or video noise may result from what is is to record and reproduce it. known as chrominance/luminance delay inequality. color temperature switch A control on many video See Color recording. See also Down-converted color. cameras which adjusts for different lighting condi- color value The three numbers which specify a color. tions such as bright sun, indoor light, etc. The more See also Pixel value.

62 Common Carrier Bureau

color vectorscope A testing instrument used to mea- combining unit Circuit designed to combine sound sure the color purity, frequency response and so on and vision outputs to enable them to use a com- of video components. It can test RF and video sig- mon aerial array. The requirements of the combin- nals as well as check the time delay between two ing unit are that a minimum loss should occur within signals. When used in the field, the unit can help the unit, that a minimum signal should be fed back with multiple camera setups by providing precise to the other transmitter, and that the impedances phase matching (genlock) adjustments. of the inputs and output should correctly match color video noise meter A professional/industrial in- those of the transmitters and aerial, in order to strument designed to measure luminance noise, achieve a maximum transference of power. chroma AM noise and chroma PM noise for either combi player A general term used by journalists and NTSC or PAL signals. These electronic meters usu- columnists to describe a unit that can play various ally provide other features, such as automatic level sizes of audio and video discs. control, automatic sag compensation, character dis- comet tail Also called comet. A streak, generally caused plays that indicate present operations and warning by an overload camera tube. They can be prevented messages, special circuitry for automatic testing and or minimized by means of an ACT gun in the tube. automatic memory. See Photoconductive lag, Anti-comet tail (ACT) gun, color video printer See Video printer. Sky. color wheel A graphic depiction of the color compo- commercial eliminator A device designed to elimi- nents. The color wheel principle shows how the three nate commercials during unattended recording on primary colors blend into intermediate colors and a VCR. One type works only during black and white white. In the present color TV system, this basic three- programs and films, cutting out color commercials color system is used to produce the color TV by a special color burst signal that activates the VCR. picture. A second type operates with recordings of black and color zero The color in the Amiga’s palette that can white and color programs. This unit disconnects an be replaced by a genlocked video signal from an- internal circuit when the program fades to black and other source, e.g., a video camera. activates another circuit when the audio goes silent. coma 1. Lens defect associated with images away from Because these devices require that the VCR be in the optical axis. A non-axial point object does not Pause, they don’t work on many machines which give rise to a point image even in the absence of cannot operate in Pause mode when the automatic spherical aberration, and the best image that can timer is engaged. Commercial eliminators of either be produced consists of a small patch of light with a type are not 100% accurate; often part of a pro- tail to one side in the shape of a comet. 2. A CRT gram is edited out along with the unwanted com- image defect that makes the spot on the screen mercials. By the late 1980s, they had all but appear comet-shaped when the spot is away from disappeared from the video marketplace. the center of the screen. See also Distortion. commercial killer Commercial eliminator. combat camera A hand-held camera used to film or commercial-killing VCR A VCR with a system that tape warfare or other action. kills commercials; RCA. When the recorder makes a comb filter A filter whose insertion loss causes its spec- tape from a broadcast or cable program, it auto- trum to form a sequence of equispaced narrow pass- matically rewinds it to the beginning and fast for- bands or stop bands centered at multiples of some wards to the start of the first commercial break specified frequency. The frequency response resembles (whose location has been memorized on the VCR’s the teeth of a comb. One major application for comb tape counter based on visual and audio cues). The filters is separating NTSC and PAL color and bright- VCR then encodes commercial-start and -end sig- ness signals. nals on the tape’s control track. It continues to seek combination-tone distortion Syn.: intermodulation out and mark recorded commercials to the end of distortion. See Distortion. the tape, and then rewinds. On playback, the VCR combined head Syn.: read/write head. goes into the forward search mode during the com- combiner In digital picture manipulators, a device that mercials, while a blue field masks the picture. The controls the manner in which two or more channels end signal puts the VCR back in the play mode. Thus, work together. Under software control, it determines instead of a commercial, the viewer sees a blank the priority of the channels (which picture appears blue screen for a maximum of 30 s. in front and which in back) and the types of transi- Commission Internationale de I’eclairage (CIE) An tions that can take place between them. international group that has set most of the basic combiner circuit The circuit that combines the lumi- standards of light and color now used in color TV. nance and chrominance signals with the synchro- Commodore Dynamic Total Vision See CDTV. nizing signals in a color TV camera chain. Common Carrier Bureau A department of the Fed- combining filter Passive device for feeding the out- eral Communications Commission responsible for puts of two transmitters to a common aerial system. recommending and implementing regulatory poli-

63 Common Image Format

cies on interstate and international common carrier Solar cells form the primary power supply for sat- (voice, video, data) activities. ellites with a back-up of batteries for use during the Common Image Format See CIF. brief periods of solar eclipses. The operational life- Common Interface Format See CIF. time of a modern satellite should be at least 5 years. Common Intermediate Format A videophone ISDN A geostationary satellite can be maintained in a standard which is part of the CCIT’s H.261. It pro- stable attitude by spinning about an axis parallel to duces a color image of 352 by 288 pixels. The for- the earth’s axis. In Intelsat IV the high-gain aerials mat uses two B channels, with voice taking 32 Kbps are mounted on a platform that rotates about the and the rest for video. spin axis but in the opposite direction. The aerials comms Informal communications. then appear stationary with respect to the earth, at communications satellite (comsat) An artificial un- their desired orientation. Parabolic reflectors allow manned satellite in earth orbit that provides high-ca- spot-beam transmission to regions of limited size, pacity communication links between widely separated such as W. Europe, which have high communica- locations on earth. International telephone services tion traffic densities. and the exchange of live TV programs and news are The earth stations must be situated some dis- achieved by transmitting microwave signals, suitably tance from terrestrial microwave relay systems to modulated, from an earth station to an orbiting sat- avoid radio interference. The aerials of the stations ellite and back to another earth location. in the Intelsat system, such as at Goonhilly in The first satellites, including the large metallized Cornwall, have apertures of 25 to 30 meters. The balloons ECHO-1 and ECHO-2, were passive systems; aerials should be steerable to compensate for per- they simply reflected or scattered the microwave turbations of the orbits caused by gravitational ef- beam back to another earth station. Present-day fects of moon and sun. Present-day systems provide systems use active satellites, in which the signal is simultaneous multiple access to one satellite from a amplified and its frequency changed by a transpon- large number of earth stations within one coverage der before it is retransmitted to earth. The first suc- zone. This is achieved by time-division multiplexing cessful active satellites included the Telstar and Relay or frequency-division multiplexing. In the former case satellites (1962-64). They were in relatively low or- a station does not share the transponder power with bits and were only in line of sight of any two earth other stations and can operate at close to satura- stations for a short period each day and then had to tion where the transponder is most efficient. be tracked as they moved across the sky. community antenna relay service (CARS) See Mi- A satellite in a geosynchronous orbit revolves from crowave relay. west to east in an orbital period equal to that of the community antenna television (CATV) Another earth’s rotation (about 23 hours 56 minutes). It traces name for cable TV. Signals from distant TV stations a figure-of-eight pattern in the sky with equatorial are picked up by a large antenna, typically located plane. A geostationary orbit is a circular synchro- on a hill, then amplified and piped all over the com- nous orbit lying in the equatorial plane at an alti- munity below on coaxial cable. tude of 35,790 km. A geostationary satellite will compact disc (CD) The 12 cm. (4.75 in.) optical read- appear to be stationary to an observer on stationary only disc used for digital audio, data, or video in orbits. One such satellite can cover an extensive sur- different systems. face area, excluding polar regions. For global cover- Compact Disc-Interactive (CD-i) An interactive au- age at least three geostationary satellites are needed, dio/video/computer system developed by Sony and situated over the equatorial Atlantic, Indian, and Philips for the consumer market. Provides audio, digi- Pacific Oceans. For long east-west links at high north- tal data, still graphics and limited motion video. erly latitudes the Russians have used satellites in Geared toward home entertainment. Unlike conven- highly elliptical 12-hour orbit. tional CD-ROMs, CD-i drives have a built-in micro- The International Telecommunications Satellite processor to handle many of the computing Consortium (Intelsat), established in 1964, is respon- functions. CD-i also has commercial and industrial sible for international nonmilitary satellite commu- applications. CD-i has been superseded by DVD and nications. Early Bird, later renamed Intelsat 1, was other platforms. launched in 1965. The much heavier Intelsat IVa, compact disc, read-only memory (CD-ROM) A com- launched in 1975, have up to 6000 circuits and a pact disc adapted for home entertainment that is much longer life. capable of storing video and audio data in digital The radio window covers the frequency range format for playback through a computer. Data bits from 15 MHz to 50 GHz, with the optimum trans- are stored as microscopic pits on the disc and are mission in the range 1 to 10 GHz. The frequency read by a laser beam. bands used by Intelsat systems are from 5.925-6.425 Compact Disc Video (CDV) A compact laser disc, in- GHz for the earth-to-satellite path and from 3.7-4.2 troduced by Philips, which plays both pictures and GHz for the satellite-to-earth path. sound. Compared with video cassettes, they have

64 component television

better sound, last longer, give easier and faster ac- bers of HDTV and conventional receivers, both types cess to the section you want, and have better freeze- of compatibility are highly desirable. frame. You can’t, however, record onto or from compatible color television system A color TV sys- them. The basic technology of the CDV is similar to tem that permits the substantially normal black and that of the audio or sound CD (called CD-DA to dis- white reception of the transmitted color picture sig- tinguish it). They look the same, but CDVs are usu- nal on a typical unaltered black and white receiver. ally colored gold, whereas CD-DAs are silver. Initially This is accomplished in the NTSC and PAL systems they were made in three sizes, which contain re- by dividing the color video information into a lumi- spectively 6, 20, and 60 minutes of audio-visual nance signal and two chrominance signals. The lu- material on each side. Superseded by DVD. minance signal is the equivalent of a black and white compact source iodide (CSI) An iodide gas-discharge TV picture signal and is used alone by a black and mercury arc lamp that is small-size and produces white receiver. near-daylight illumination, used in film and TV. complementary colors Colors which result from sub- See CVC. tracting in turn the three primary colors from the Compact Video Compressor One of several software visible spectrum: minus-green (magenta), minus-red algorithms for compressing video into QuickTime (blue-green or cyan) and minus-blue (yellow). movies. It is very asymmetrical, in some cases taking component digital A digital representation of a com- as much as 1 hour to compress 1 minute of video, ponent analog signal set, most often Y, B-Y, R-Y. which can later be quickly decompressed. The ad- The encoding parameters are specified by ITU-R vantage here is that a movie with Compact Video BT.601-2 (CCIR 601). The pro-video parallel inter- Compression looks better and runs faster than the face is specified by ITU-R BT.656 (CCIR 656) and Apple Video-compressed movie. The Compact Video SMPTE 125M. Compressor was also optimized to create movies that component digital editing A sophisticated editing can be smoothly played back from a CD-ROM disc. process used in relation with professional/industrial comparator A circuit that is a basic component of equipment such as digital or production switchers. flash ADCs. Has two inputs, X and Y, along with This advanced editing technique usually employs one output we call Z. The comparator implements other features, such as compositing in real time and the following mathematical function: if A – B greater color correction functions. than 0, then Z = 1; if A – B less than 0, then Z = 0. If component switcher A video switcher that deals with A = B, Z may be undefined and oscillate between 1 the individual color components (R,G,B or YPbPr) of and 0 wildly until that condition is removed, it may the picture instead of the encoded composite video be a “1,” or it may be “0,” depending on how the signal. It’s almost like having three separate switch- comparator was designed. ers combined into one package. The three color com- compatibility, HDTV/conventional TV In 1988 Rob- ponents travel through the switcher in parallel. This ert Hopkins suggested five levels of compatibility: generally produces a much sharper picture and Level 0 — Incompatible. The conventional re- crisper special effects. ceiver cannot display the HDTV image, and the HDTV component television The use of individual units such receiver cannot display the conventional image. as a TV monitor, tuner, speakers and so on which Level 1 — The HDTV signal can be converted by make up a TV system otherwise combined in one an expensive adapter to provide a display on the box, the TV set or receiver. Proponents of compo- conventional receiver. nent TV speak of advantages such as better video Level 2 — Same as level 1, except that the adapter and improved sound as well as flexibility in compo- is inexpensive. nent selections. The center of such a system is the Level 3 — The HDTV image is received and dis- monitor which, although it lacks a tuner, has direct played by the conventional receiver, but at a loss of audio and video inputs, higher resolution, more cir- quality relative to the receiver’s optimum performance. cuitry, etc. The component tuner is capable of bet- Level 4 — The same as level 3, except that the ter electronic isolation, thereby eliminating more quality of the image is the highest of which the noise, distortion and signal loss than its counterpart receiver is capable. built into the conventional TV set. Component tun- Level 5 — The image displayed by the conven- ers also feature frequency-synthesized tuning, vari- tional receiver has all the quality of the HDTV image. ous audio/video inputs/outputs, remote Other terms applicable to compatible systems are control, etc. Sony introduced the first component “forward” versus “backward.” In a forward system, TV in 1980 in Japan and later to the US. It provided the conventional receiver obtains service from the a choice of two monitors with dual channel 10-watt advanced or HDTV signal at levels 1 through 4. In amplifiers and external speakers as well as other op- the backward version, the HDTV or advanced re- tional accessories. Discriminating American ceiver obtains service from the conventional signal. videophiles have opted for TV monitor/receivers When the audience is served by substantial num- instead of component TV.

65 component tuner component tuner An individual unit which, along with dustrial device designed to produce shadows, trans- a TV monitor, audio amp, speakers and other parts, parencies, reflections, blue foreground objects and make up a TV system or component video. The tuner other effects. Used chiefly in post-production, the portion of this system provides a video signal with less compositing system can correct corner darkening loss, noise and distortion than is usually present in con- and unnatural shadows in a multi-layered image. ventional TV sets. This is the result of quality compo- Some models provide a built-in time-code reader, nents within the tuner, better isolation of the parts capabilities for hundreds of events to be pro- and generally higher manufacturing standards. Com- grammed for real-time on-line compositing and a ponent tuners offer several features, including, among menu-driven remote control. others, wireless remote control, frequency-synthesis compressed serial digital interface (CSDI) A way of tuning and direct inputs and outputs for connections compressing digital video for use on SDI-based to monitors, VCRs, cameras and speakers. equipment proposed by Panasonic. Now incorpo- component video 1. Three color video signals that rated into Serial Digital Transport Interface. describe a color image. Typical component systems compressed video TV signals transmitted with much are R,G,B; Y,I,Q; or Y,U,V. 2. Transmission and re- less than the usual bit rate. Full standard coding of cording of color TV with luminance and chrominance broadcast quality SDTV typically requires 45 to 90 treated as separate signals. megabits per second. Compressed video includes composite color signal The color picture signal plus signals from 2 Mb/s down to 56 Kb/s. The lower bit all blanking and synchronizing signals. The compos- rates typically involve some compromise in picture ite color signal thus includes the luminance signal, quality, particularly when there’s rapid motion on the two chrominance signals, vertical and horizon- the screen. tal sync pulses, vertical and horizontal blanking compression 1. A digital process that allows data to pulses, and the color-burst signal. be stored or transmitted using less than the normal composite color sync The signal comprising all the number of bits. Video compression refers to tech- sync signals necessary for proper operation of a color niques that reduce the number of bits required to receiver. This includes the horizontal and vertical sync store or transmit images. 2. Audio term similar to and blanking pulses, and the color-burst signal. video clipping is the automatic adjustment of vol- composite digital A digitally encoded video signal, ume variations to produce a nearly consistent level such as NTSC or PAL video, that includes horizontal of sound. Elimination of audio overmodulations pro- and vertical synchronizing information. duces a sound track lacking in dynamics—it is never composite master An original program produced by soft or loud, but always at the same level. 3. Digital editing various portions of other recordings onto a effect where the size and/or aspect of the picture is new reel of tape; in electronic editing the resulting changed on the TV screen; zoom effect with objects tape is one generation from the master materials decreased in size. from which it was recorded. compression artifacts Compacting of a digital sig- composite picture signal The complete picture sig- nal, particularly when a high compression ratio is nal as it leaves the TV transmitter. The picture con- used, may result in small errors when the signal is sists of picture data, blanking pulses, synchronizing decompressed. These errors are known as artifacts, pulses for monochrome, and the color subcarrier, or unwanted defects. The artifacts may resemble color burst, and other information needed for trans- noise or may cause parts of the picture, particularly mission of color pictures. Also called composite sig- fast moving portions, to be displayed with the move- nal and composite video signal. ment distorted or missing. composite signal Composite picture signal. compression/expansion noise reduction See Noise composite sync The total sync system containing both reduction system. vertical and horizontal scan controls. compression ratio A number used to tell how much composite triple beats See Triple beats. information is squeezed out of an image when it composite video signal Composite picture signal. has been compressed. For example, suppose we start (CVS/CVBS) A signal that carries video picture infor- with a 1-Mbyte image and compress it down to 128 mation for color, brightness and synchronizing sig- Kbytes. The compression ratio is 8:1; 1/8 of the origi- nals for both horizontal and vertical scans. nal amount of storage is now required. For a given Sometimes referred to as “Baseband Video.” Typi- compression technique—MPEG, for example—the cal composite TV standard signals are NTSC, PAL, higher the compression ratio, the worse the image and SECAM. RGB is not an example of composite looks. This has nothing to do with which compres- video, even though each red, green, and blue sig- sion method is better, for example JPEG vs. MPEG. nals may each contain sync and blank information, Rather, it depends on the application. A video stream because all three signals are required to display the that is compressed using MPEG at 100:1 may look picture with the right colors. better than the same video stream compressed to compositing system A sophisticated professional/in- 100:1 using JPEG.

66 continuous motion compunications A recent creation meaning the com- signals which transmit both audio and video signals. bination of , computers, TV and data All the above connectors use coaxial cable. The twin systems. lead cable usually doesn’t need connectors. Gener- computerized editing A system of editing that per- ally, VHS machines use the RCA phono type while mits the numbering of each frame of video as it is Beta VCRs employ mini-plugs for audio and RCA being shot on location with a video camera. This phono jacks for video. Another type is the multi-pin reference then makes it possible to edit the tape connector used between a video camera and a VCR. immediately. Computerized editing is available only console 1. A large cabinet for a radio or TV receiver with industrial VCRs. Also called computer-assisted that stands on the floor rather than on a table. 2. A editing. main control desk for TV station. computerized TV See Telecomputer. constant angular velocity See CAV. COMSAT COMmunications SATellite. constant bit rate Constant bit rate (CBR) means that concave A lens configuration in which the lens a bitstream (compressed or uncompressed) has the element has an inward curve. same number of bits each second. condenser Describes a type of microphone element constant linear velocity See CLV. that uses two condenser plates to convert sound constant luminance system A color TV system in waves to voltage variations. which the brightness of the reproduced picture de- condenser lens A lens to concentrate the image so pends solely on the transmitted luminance signal and that it will all enter the video camera lens. is unaffected by the chrominance signal transmit- condenser microphone A wide-range mic usually ted with it. This is an ideal which is not perfectly built into video camera or camcorder. It is designed achieved in the NTSC, PAL and SECAM color basically to pick up all the sound in the shooting systems. area and is characterized by wide frequency range Constant-Minimum Wavelength-Constant Angular and low distortion. The mic contains circuitry that Velocity (CWL-CAV) Method for high-density mag- uses a condenser and requires batteries. neto-optical disc recording; NEC Corp., Tokyo. The conditional access This is a technology by which ser- technique allows up to 23 Gbytes of multimedia data vice providers enable subscribers to decode and view to be written to a single 30-cm disc. 32 minutes of content. It consists of key decryption (using a key NTSC composite digital signals can be recorded with- obtained from changing coded keys periodically sent out compression. Using MPEG-2 compression at 8 with the content) and descrambling. The decryption Mbits/s, up to 5 h of full-motion video can be may be proprietary (such as Canal+, DigiCipher, recorded on a disc. Irdeto Access, , NDS, Viaccess, etc.) or Consumer Electronics Show (CES) A seasonal event standardized, such as the DVB common scrambling originating in the consisting of independent algorithm and OpenCable. Conditional access may dealers, buying groups, domestic and foreign manu- be thought of as a simple form of digital rights facturers, government officials, importers, chain and management. department store buyers, trade guests and mem- Two common DVB conditional access (CA) tech- bers of the press. New products and innovations in niques are SimulCrypt and MultiCrypt. With consumer electronics are highlighted and displayed. SimulCrypt, a single transport stream can contain consumer-level monitoring equipment See Video several CA systems. This enables receivers with dif- monitoring equipment. ferent CA systems to receive and correctly decode continuous film scanner A TV film scanner in which the same video and audio streams. With MultiCrypt, the motion-picture film moves continuously while a receiver permits the user to manually switch be- being scanned by a flying-spot kinescope. tween CA systems. Thus, when the viewer is pre- continuously variable slope delta (CVSD) modulation sented with a CA system which is not installed in his A technique for converting an analog signal (such receiver, he simply switches CA cards. as audio or video) into a serial bit stream. Modula- connector The metal fitting or connection at the end tor/demodulator circuits that encode and decode of a wire or cable. A connector can be male or fe- functions on the same chip with a digital input for male, thread-type or slip-on. The barrel-shaped fe- selection. male connector has external threads and is usually continuous motion In video, a smooth, moving im- located at the rear of the component, while the male age such as that which is produced on videotape, part is on the cable. There are various types of con- DVD or some videodisc formats such as CD-I or CD-V. nectors. The BNC is most often utilized for profes- Other disc formats, such as CD+G, produce graph- sional hook-ups. The PL-259 is double the size of its ics, with some new images displayed on screen in look-alike, the F-fitting, and is sometimes used with less than 1 s. However, the total effect resembles video cameras and some industrial equipment as well strobe display—a sequence of images—rather than as for transmitting video-only signals. The F-connec- the more familiar continuous motion that viewers tor, the most popular, is designed basically for RF know from TV and films.

67 continuous presence continuous presence In teleconferencing, the simul- and the other section controlling the chrominance taneous presence of two or more video images. The signals; this permits adjustment of contrast without images may appear on a single monitor in a split changing color. screen mode or on two separate monitors. contrast gradient See Gamma. contour control Refers to the capabilities of a projec- contrast range See Contrast ratio. tion TV system or similar unit to adjust the sharp- contrast ratio Contrast range. The ratio of the maxi- ness at the edges of a screen image in relation to its mum to minimum luminance values on a CRT, liq- contrast. See also Horizontal image delineation. uid-crystal display or active display for a TV set, a contouring In digital systems, the appearance of pat- , or a video terminal. A contrast terns in a digitized image because the quantization ratio of at least 10:1 is needed for the best readabil- did not have enough levels. This is an image artifact ity. In (2+3)D-image display systems with parallax caused by not having enough bits to represent the barrier stripes, at least 6:1 or more is needed as a image. The reason the effect is called “contouring” contrast ratio of the barrier and the opening por- is because the image develops vertical lines. tion (portion without any barrier). When the con- contours-out-of-green In TV cameras, a technique trast ratio is less than 6:1, a crosstalk occurs. for increasing picture sharpness. Pulses are gener- contrast resolution The number of gray levels at each ated from the green signal at each edge in the im- pixel in a digital image, determined by raising two age by separating its high-frequency components. to the power of the number of bits at each pixel. The green channel is used to generate these pulses contrast transfer function (CTF) See Aperture because it has the best signal-to-noise level. The response. “white” contours—changes from dark to light—are contribution In B-ISDN applications, the use of broad- added at the aperture correction circuit, while the band transmission of audio or video information “black” contours are added after gamma to the user for post-production processing and correction. distribution. contrast The degree of difference in tone between contribution quality The level of quality of a televi- the lightest and darkest areas in a TV picture; a video sion signal from the network to its affiliates. For digi- term referring to how far the whitest whites are from tal television this is approximately 45 Mbps. the blackest blacks in a video waveform. If the peak control desk Console. white is far away from the peak black, the image is An electrode situated between the cath- said to have high contrast. With high contrast, the ode and the other electrodes of an electron tube, image is very stark and very “contrasty,” like a black- the potential of which determines the magnitude and-white tile floor. If the two are very close to each of the electron current flowing from the cathode to other, the image is said to have poor, or low, con- the other electrodes. The control grid is usually situ- trast. With poor contrast, an image may be referred ated very close to the cathode and is constructed in to as being “washed out”—you can’t tell the differ- the form of a wire spiral, the pitch of which can be ence between white and black, and the image looks adjusted during manufacture to give the required gray. Contrast is measured in terms of gamma, a degree of control over the density of the electron numerical indication of the degree of contrast. Pic- stream. Thus, the pitch of the grid determines the tures with high contrast have deep blacks and bril- mutual conductance of the tube. In a CRT, the con- liant whites, and pictures with low contrast have an trol grid (sometimes known as the modulator) is of- overall gray appearance. ten in the form of a disk containing a small aperture contrast compensation switch On some video cam- through which the electron beam passes. eras with automatic iris control, a feature designed control room A room from which engineers and pro- to provide more or less light by opening or closing duction personnel control and direct a TV or radio the lens approximately one f-stop. In scenes with program. It is adjacent to the main studios and sepa- lighter or darker backgrounds than the subject, the rated from them by large, soundproof, double-glass automatic iris may not give the desired lighting, windows. thereby resulting in over- or underexposure. The con- control signal A special signal recorded onto the vid- trast compensation switch corrects for this by either eotape at the same time a video signal is being re- opening or closing the lens. This feature is different corded. Using during playback as a reference of the from and more flexible than the backlight switch servo circuits. which can only open the lens. control track The lower portion along the length of a contrast control A manual control that adjusts the videotape on which sync control information is range of brightness between highlights and shad- placed and used to control the recording or playing ows on the reproduced image in a TV set. Usually, back of the video signal on a VCR. Editing a tape the contrast control varies the gain of a video am- that has only control track instead of time code is plifier. In a color TV set a dual control can be used, very difficult. Master tapes (edited) have control track with one section controlling the luminance signal information instead of time code. Time code must

68 copy block

be added to master tapes in order to have editing the lens element has an outward curve on one side flexibility in combining master elements. and an inward curve on the other. control track counter editing controller A device conversion factor (CF) In digital video, the ratio to control videotape editing by counting the control between the digital and the normalized represen- track pulses on the tapes. tation of the signal. Normalization is done to control track pulse An electronic control signal placed R = G = B = 1 at peak white and the digital sig- on the bottom portion of the videotape during re- nals are represented on a scale of 256 (8 bits). cording. When the tape is played back, the control conversion filter See Color conversion filter. track pulses guide the video heads in reproducing converted chrominance signal See Converted sub- accurately the original information. The pulses, which carrier direct recording method. make up the control track, usually govern the speed converted subcarrier The process of frequency shift- of the VCR and designate the start of every second ing the color 3.58-MHz subcarrier and its sidebands video field recorded on the tape. down to 629 kHz. See also Converted subcarrier CONUS Continental U.S. Also, a TV news company direct recording method. that provides global news coverage to local TV converted subcarrier direct recording method In stations that are members on an exclusive market order to avoid visible beats in the picture caused by basis. the interaction of the color (chrominance) and bright- conventional systems 525-line NTSC system and 625- ness (luminance) signals, the first step in the con- line PAL and SECAM. See also System terminology. verted subcarrier method is to separate the convergence 1. A condition in which the electron chrominance and luminance portions of the video beams of a multibeam CRT intersect at a specified signal to be recorded. The luminance signal, con- point, such as at an opening in the shadow mask of taining frequencies from dc to about 4 MHz, is then a three-gun color TV picture tube. Both static and FM recorded. The chrominance portion, containing dynamic convergence are required. 2. A measure of frequencies in the area of 3.58 MHz, is down-con- the clarity of a color monitor. A measure of how verted in frequency in the area of 629 kHz. This con- closely the R,G and B guns in a color monitor track verted chrominance signal can be recorded directly each other when drawing a color image. 3. See Mul- on the tape. The frequencies in the area of 629 kHz timedia. are still high enough to allow equalized playback. In convergence alignment A process which lines up or practice, the converted chrominance signal and the overlaps the three primary colors of TV (red, green, FM signals are mixed and then simultaneously ap- blue) and brings them into registration to form a plied to the tape. Upon playback, the FM and con- perfect image. verted chrominance signal are separated. The FM is convergence coil One of the coils used to obtain con- demodulated into a luminance signal again. The con- vergence of electron beams in a three-gun color TV verted chrominance signal is reconverted back up in picture tube. frequency to the area of 3.58 MHz. The chrominance convergence control An adjustment or set of adjust- and luminance signals are combined, which repro- ments that brings together the three primary colors duces the original video signal. (red, green, blue) into one focal point. In projection converter See Cable television converter, Single con- TV using a three-tube system, alignment is needed version block converter, Up converter. to merge the three separate images into registra- convex A lens configuration in which the lens ele- tion without color fringing. Controls for two colors ment has an outward curve. are adjusted both horizontally and vertically while cookie A cutout screen placed before a light source to the third primary color (usually green) serves as cast random wall shadows. Light source should be reference for the other two. a focused source through a lens (an ellipsoidal lamp convergence electrode An electrode whose electric is ideal, or a can be used). field converges two or more electron beams. coordinate data In (2+3)D-image display systems, in- convergence magnet A magnet assembly whose formation to indicate the position and size of the magnetic field converges two or more electron window. beams. Used in three-gun color picture tubes. Also Coppola, Francis Ford Film director; early proponent called beam magnet. of previsualization, a videotaping of artists’ views convergence plane A plane that contains the points and scenes of a film to help form a rough version of at which the electron beams of a multibeam CRT the finished work; and the first director to utilize appear to experience a deflection applied for the electronic cinema during the making of One from purpose of obtaining convergence. the Heart (1982). Although more popularly known convergence surface The surface generated by the for his films (The Godfather and Apocalypse Now), point of intersection of two or more electron beams Coppola remains in the forefront of video and elec- in a multibeam CRT during the scanning process. tronic experimentation as they relate to filmmaking. converging meniscus A lens configuration in which copy block In radio and TV broadcasting, the portion

69 copy guard

of the script to be read. In TV broadcasting, this is The filter permits the passage of overtones which it written on the right half or two thirds of the page, “reads” based on the original tone. When no tone with cues and technical details written on the left. is present, the filter blocks the passage of any extra- copy guard See Anti-piracy signal. neous sound (noise) from getting through. The re- copying In video, the term refers to making a dupli- sults of the correlator filter are similar to those of cate copy of the audio and video material of a tape. the dynamic noise filter, but the methods of achiev- The process can include dubbing, as it is often called, ing them are different. from a 1/2-inch machine to an industrial 3/4-inch, 1- co-siting Relates to component digital video, in which inch or 2-inch VTR. Or it can involve a Beta format the luminance component (Y) and the two chromi- and a VHS machine or vice versa. There are two basic nance components (Cb and Cr) are sampled at the methods employed, RF copying and direct copying. same time. In the first, the open channel output is connected to couch potato A person who stays at home (sits on a the VHF input of the machine doing the recording. In couch) and vegetates (is sedentary, like a potato), the second method, cables are connected from the especially by watching TV for long periods. audio and video outputs of the first machine to the coupler An accessory which accepts two sources or audio and video inputs of the recording VCR. This units and permits them to be fed through one out- method is much preferred since its direct connections put. In other words, a two-way splitter can be used produce a better copy. However, special cable con- in reverse to form a coupler. The splitter/coupler nections may be needed since Beta and VHS use dif- should be the signal splitter type, not the VHF/UHF ferent phono plugs, especially in the audio input and version. See Signal splitter. output. If your original tape is a master, the new copy coverage (CVG) 1. The geographic area in which a TV is called a first generation tape; if your tape is a prere- station is received by viewers, as indicated on a cov- corded one, then the copy you have just made is called erage map. See Service area. 2. In film, TV, the shoot- a second generation tape. Each generation removed ing of a scene from various views and using various from the original or master adds to the degradation exposures. of the picture quality. Duplicating copyrighted coverage map See Coverage. material is not legal. covering power In film and TV, the capacity of a cam- copy-protection signal A signal to prevent home era lens to pick up (cover) a clear image over the copying of prerecorded videotapes. Located in the entire frame. VBI, that signal includes pulses that affect the AGC cover shot In TV, a wide or long-distance view, gener- of the VCR that is recording the copy-protected tape. ally begins a sequence to establish the location. The nature of the signal in the VBI distorts the video cover story An article featured on the cover of a maga- of the unauthorized recording. zine or other publication, generally the major article core The light-transmitting material at the center of a in the issue. With the development of magazine- fiber optic cable. style TV programs, many print terms have come into corner antenna Corner-reflector antenna. use by broadcasters; thus, cover story also denotes corner insert A second video picture signal added to a major feature or sequence on a TV program. an area of the first video picture signal. Corner in- CPA Color Phase Alternation. serts are achieved by halting the horizontal and ver- C-Phone (short for computer phone) A Twincom’s per- tical scanning of the first picture in a predetermined sonal videoconferencing kit that includes the - area and inserting the second picture’s scanning essary software and a single piece of hardware— portions into that area. See PIP. housing the camera, mic, and speaker. It sits atop corner-reflector antenna An antenna that consists the computer monitor. In addition to full-motion of two conducting surfaces intersecting at an angle, color video at 30 fr/s, the C-Phone system bounces which is usually 90 degrees, with a dipole or other the incoming audio off the PC’s screen to create the antenna located on the bisector of the angle. The impression that the caller’s voice is coming from the surfaces are often made of wire mesh to reduce wind display. resistance. Maximum pickup is along the bisector of CPS emitron tube Syn.: Orthicon. the reflector angle. Used as a UHF TV and radio Cr Coded color difference signal (digital R-Y). receiving antenna. Also called corner antenna. crab A method of moving a TV or film camera on a corona Similar to an electric arc, except that this is a pedestal, on which all wheels are steered simulta- characteristic of much higher voltages (thousands). neously; mobile unit used in crabbing. The method Corona occurs as a continuous, fine electrical path is used for lateral movements (crab shots), particu- through air between two points, sometimes accom- larly in small areas. The instructions are crab left (or panied by a faint violet glow, usually near the truck left) and crab right (or truck right). picture tube. crane A vehicle with a movable arm or boom (gener- correlator filter Used in certain noise reduction sys- ally hydraulic) that moves a platform on which are a tems to separate and cut out noise from overtones. camera and a crew; sometimes called whirly. A crane

70 cross-hatch signal

typically has three seats, for the director, camera op- frequency at which the TV picture does not flicker is erator, and camera assistant or focus puller. The base about 60 Hz. of the vehicle is called a trolley. A crane shot or boom critical focus Precision-sharp clarity of image; an in- shot is a shot taken from a crane. struction to a camera operator of this requirement crane shot See Crane. for a specific scene. Areas in front of and behind crash editing A simple, basic editing technique of the subject may be blurred or imperfect. adding one segment after another of recorded pro- critical fusion frequency The lowest repetition rate gramming from one tape onto another. The method at which a continuous image is perceived. Both TV utilizes the Pause control (instead of Stop), then and motion pictures depend on the retentivity of Record, to help minimize picture breakup between the eye to merge a rapid sequence of images into a scenes. Most recent video equipment compensates single continuous one. If the repetition rate of the for pausing and recording, thereby virtually elimi- images is too low, the eye will fail to merge them, nating the annoying breakup that used to show up and flicker results. between scenes edited on older VCRs. As in all edit- critical section In the DVI RTX software, a critical sec- ing, two home video recorders, audio and video in- tion is a segment of code in one RTX task which put and output connections and a TV set used as a must not be interrupted by another RTX task. monitor provide the bare essentials. Also called as- crop Camera framing; or framing of an object to ex- semble or assembly editing. clude some picture information. crawl Lettering that moves across all or part of a TV cross A movement of a performer across a stage or screen (often the bottom). The crawl can refer to set. Types include direct cross (movement in a straight news of national importance, local election results, line) and curved cross (one or more curves in mov- dramatic changes in local weather conditions, etc. ing from one place to another). The starting and Also called crawl roll. The effect is produced by ending points of the movement are sometimes mounting the text on a drum like mechanism, also shown on the stage or stage plan with an X (cross). known as the crawl roll. The crawl can be horizon- cross backlight Kicker. tal (across the top or bottom of the screen) or verti- cross-channel fade See Cross-fade. cal (from the bottom, moving up). It is positioned in cross-color In NTSC or PAL, a signal intermodulation the crawl space. arising in the bands occupied by the chrominance crawling dot pattern See Moire. subcarrier signal. It causes a display of false colors crawl roll See Crawl. to be superimposed on repetitive patterns in the lu- crawl space See Crawl. minance image. This occurs when the video decoder CRC Cyclic redundant check. Used in data transfer to incorrectly interprets high-frequency luma informa- determine if the data has been corrupted. It is a tion (brightness) to be chroma information (color), check value calculated for a data stream by feed- resulting in color being displayed where it shouldn’t. ing it through a shifter with feedback terms EXORed cross-color interference Interference produced in the back in. chrominance channel of a color TV set by crosstalk creepy-crawlies A specific image artifact that is a re- from the monochrome signal. sult of the NTSC system. When the nightly news is cross-fade To fade out one video signal and fade in on, and a little box containing a picture appears over another as a simultaneous movement; can be writ- the anchorperson’s shoulder, or when some com- ten as X on taping scripts. May be applied to vision, puter-generated text shows up on top of the video sound or lighting. Also known as cross-channel fade clip being shown, along the edges of the box, or or fader. along the edges of the text, you’ll notice some crosshatch generator A signal generator that gener- jaggies “rolling” up (could be down) the picture. ates a crosshatch pattern for adjusting color TV set That’s the creepy-crawlies. Some people refer to this circuits. as zipper. crosshatching In projection TV, the converging of col- creepy peepy A portable TV camera, or minicam; also ored lines on a screen to bring the three color tubes spelled creepy-peepy, creepie peepie, or creepie- into alignment. In three-tube systems (each tube or peepie. “gun” representing a primary color) it is essential crispening Process of electrically sharpening the edges that all three converge exactly. Projection TV systems, of a TV image. therefore, provide each color tube with a test pat- crimping A mechanical method of attaching a jack to tern of intersecting lines to facilitate crosshatching. the end of a cable. The sleeve of the jack is squeezed cross-hatch signal A grid-like pattern produced on a around the cable so that it will stay on; most often TV screen designed to check horizontal and vertical used in coaxial cable installation. linearity as well as align convergence. The cross- critical flicker frequency The frequency at which a hatch signal pattern consists of 14 by 17 lines (NTSC flickering light source is perceived by the eye to be standard) or 14 horizontal by 19 vertical lines to changing from pulsating to continuous. The lowest match the PAL 625-line standard. Some units, such

71 cross-luma

as the TV signal generator, produce a cross-hatch detected on another. 2. The sound heard in a re- signal which can be internally switched to a dot ceiver along with a desired program because of cross- pattern, the dots appearing at the crossing points modulation or other undesired coupling to another of the lines. . 3. Interaction of audio and cross-luma See Cross-luminance. video signals in a TV system, causing video modula- cross-luminance Signal intermodulation arising in the tion of the audio carrier or audio modulation of the bands occupied by the chrominance subcarrier sig- video signal at some point. 4. Interaction of chromi- nal; artifact in the luminance channel due to defi- nance and luminance signals in a color TV receiver. ciency of Y/C separation in the decoder. This occurs 5. An effect created by crowding together the di- when the video decoder incorrectly interprets agonal tracks on a tape, thereby confusing the heads chroma information (color) to be high-frequency during playback. Packing the signals may get more luma information (brightness). It causes a crawling information into a given space on the videotape, dot pattern, primarily visible around colored edges but it eliminates the guard bands or spaces between and looks like parasitic dots at the sharp or moving tracks. To correct XT, the azimuth technique was edges of saturated colored objects. Syn.: chroma introduced by Sony in 1975. In videodisc playback, crawl; cross luma ; moving dots. XT refers to the rolling horizontal noise bars and cross modulation A condition occurring when one other extraneous signals that “spill over” from ad- signal erroneously modulates another signal. jacent pits to affect the main picture area. More crossover area See Cathode-ray tube. advanced solid-state laser pickups have virtually crossover distortion See Distortion. eliminated this problem. crossover voltage In CRTs, the secondary-emitting crossview Reception of an unwanted picture on a vi- surface voltage (SESV) at which the secondary - sion circuit analogous to cross talk on sound. De- sion ratio (SER) is unity. There are generally two pending on the system, crossview becomes visible such voltages, V1 and V2. It is possible to predict at about 30 dB difference in level between the the voltage at which the target of a TV camera tube wanted and unwanted signals. or the screen of a CRT will stabilize. For example, if CRT Cathode ray tube. The glass found the initial target potential is below V1 the second- in TV sets and video computer terminals. See Cath- ary emission ratio is less than unity and the num- ode ray tube. ber of electrons striking the target exceeds those CRTC Canadian Radio TV and Telecommunications lost from it. Thus the target potential is driven nega- Commission. ’s federal telecom regulator. tive until it stabilizes at a potential near that of the CRT coating A method designed to increase the electron-gun cathode. This is the type of target sta- brightness and contrast of a TV picture image. The bilization used in all low-velocity camera tubes. If, technique, called internal angular reflection coat- however, the initial target potential is between V1 ing, accomplishes these gains by improving the and V2 and if the final anode potential of the elec- focus of the path of light from the CRT to the tron gun is also between these two voltages then projection lens. the ratio is greater than one crush Tendency to reduce excessively the tonal range and the target releases more electrons than it gains of some part of the picture signal, e.g., white crush, from the electron beam. If the target potential is black crush. initially below that of the final anode all the sec- crystal Generic term for devices based on piezo-elec- ondary electrons released are collected by the final tricity. Each crystal is cut to vibrate at the desired anode and the target potential rises until it is ap- frequency. proximately equal to that of the final anode. If the crystal control Technique of generating various elec- target potential is initially above that of the final trical frequencies from one stable piezo-electric crys- anode the retarding field between target and an- tal source. The timing of the scanning functions in a ode returns the secondary electrons to the target TV system may be derived from a crystal timing os- and the target potential falls until again it is ap- cillator, whose inherent stability results in very stable proximately equal to the final anode potential. This scanning. This is vital if the TV signal is recorded on is the type of stabilization that occurs in high-ve- tape recorders with poor servo stability, or if it is a locity TV camera tubes and in CRTs. color signal which has to be encoded with a subcar- cross-pulse generator An electronic circuit, available rier that is frequency-related to the line scan rate. A as a separate component or built into high-priced disadvantage of crystal control is that the picture TV studio monitors, which shifts the video picture frequency is no longer locked to the a.c. power line. on a TV screen so that the horizontal and vertical Display devices with poor power supply filtering may pulses are visible on the screen, making it possible then exhibit a moving hum bar. Improvement in to adjust tracking and screw and thereby achieve as receiver design, however, is such that crystal control stable a picture as possible. has become general practice. crosstalk (XT) 1. Interference from one signal that is crystal lock Operation of a TV synchronizing pulse

72 CVP-M3

system from a stable crystal frequency reference cue track An area that runs longitudinally along the rather than from mains frequency reference. videotape and carries audio and editing information crystal microphone See Piezoelectric microphone. in the form of reference pulses or time codes. CSA Canadian Standards Association. curved cross See Cross. CSDI See Compressed serial digital interface. cut 1. An abrupt transition between two scenes. Also CTD Charge-transfer device. describes video editing. 2. To instantly replace one CTF Contrast Transfer Function. See Aperture response. picture with a second picture. CTL coding A VCR feature that magnetically marks cut-away Videotape shot of an interviewer that may the beginning of individual recordings for future ref- be interspersed during the editing process to avoid erence. CTL coding differs in some ways from con- a jump-cut editing of the interviewee. Any shots ventional indexing. The unique digital coding (close-ups, reactions, etc.) that can be used to break function, very similar to address search, permits the up long scenes or allow transitions to other parts of user to add or erase codes at any point on the tape. the program. In addition, by specifying a particular code, the user cut in blanking Interfield cut. can locate in any direction a particular program or cut-off 1. Syn.: black-out point. The point at which segment. The user simply enters a number on the the current flowing through an electronic device is remote control and activates the shuttle search cut off by the control electrode. In a CRT the cut-off mode. When the marked number is located, the VCR bias is the bias voltage that just reduces the elec- will automatically play back the selected segment. tron-beam current to zero. 2. Syn.: TV-cutoff. Sec- CTTS Cable Telephony Transport System. tion of the transmitted image that is hidden from CTV Color TV. viewers by the receiver’s mask. All final video shots, cucaloris A small sheet, usually of metal, with a pat- edits must be viewed in the TV-cutoff mode—swit- tern stamped out of it. When placed in front of a chable on most editing monitors to show what in- light source, it casts its pattern onto a background. formation will be in the final viewed product. cue To scan the playback picture at a faster-than-nor- cut-off voltage (of a camera tube) See Target mal speed in the forward direction. Syn.: search- voltage. forward. cutting on the action A production or editing tech- cue and review A very general term describing differ- nique in which two events are set in contrast to each ent features on different machines. Sony uses it for other; as event A is taking place on the screen, the its visual scan; on its SL 3000 portable, Sony applies camera switches to event B before event A has Cue and Fast Forward without a picture. According ended; often used to develop plot, create tension, to Akai, Cue means high-speed search with a pic- or produce contrast. ture. JVC uses the term Cue with its program index- cutting on the reaction A production or editing tech- ing feature. Finally, there is Cue/Review, another nique in which one event is followed by a scene concept when applied to video cameras. that displays the results of that event; after event A cue card A large card containing lines to be spoken by has taken place, the camera cuts to event B to show a performer, often used off-camera on TV; also called the impact of event A on the plot or characters. flip card, idiot card, or idiot sheet. cutting to tighten An editing procedure used to cueing Presetting a record, transcription or a tape on shorten a series of shots. Used to eliminate excess the first playback machine for immediate starting. footage and to produce a coherent whole. cue light (in British usage) Tally light. CVBS Abbreviation for Composite Video Baseband Sig- cue mark A signal or code placed on a video tape or nal or Composite Video, Blanking, Synchronization. film to warn the VCR or the movie operator where CVC Compact Video Cassette. A 1/4" VCR format in- a section begins or when to change reels. In video, compatible with other video formats. No longer be- cue marks are placed on tape electronically when a ing produced, the format was introduced by special control is activated. Each time the VCR goes Technicolor in 1980. The CVC recorder used 1/4" into Record, an electronic signal is encoded on the videotape in a cassette approximately the size of an tape. The machine can then quickly locate those sec- audio cassette. The maximum record/play time was tions in either Fast Forward or Rewind. Also known about 1 h. CVC was unlike UCM, another 1/4" sys- as index mark. tem which featured a one-unit combination of cam- cue/review A feature on virtually all video cameras era/recorder. These two systems were also with an electronic viewfinder which permits replay- incompatible. ing almost instantly a portion of recorded tape. Cue/ cvg Coverage. review may go under different names, depending CVP-M3 Color video printer; Sony. Connects to a VCR, on the manufacturer. The term is also used with VCRs camcorder, or laser disc player and creates color and is synonymous with “search” or the individual prints from video footage in about 1 minute. Prints speed of the search in each mode, such as 6x in SP, may be dated and titled, and multiple images can etc. be merged for PIP effects.

73 CX

CX Introduced by CBS Records, a noise reduction sys- cylinder servo The cylinder motor drives the video tem which compresses and expands a program, heads at the proper speed and position with respect thereby extending the dynamic range. However, like to the tape. Except for the hi-fi machines that use its competitors DBX and Dolby, it must be played spinning audio heads, cylinder servo problems af- back through a decoder to benefit from the exten- fect only the picture. One frame consists of two fields sion. The advantage that CX offers is that a pro- of video information, or 525 lines. These frames of gram played back without the decoder will still be information are repeated 30 times each second. The intelligible. Although CX also operates on the com- VCR upper cylinder contains two video head tabs pression/expansion principle, it compresses and ex- mounted 180 degrees apart. Each head tab records pands only loud signals. CX was used with the first one field of video information each revolution of opera videodiscs, produced in stereo by Pioneer the cylinder to form a complete frame. The cylinder Artists in 1982. motor speed is about 1800 rpm or 30 rps. This speed cyan Color obtained by mixing equal intensities of must be maintained even during periods when the green and blue light. It is also the correct name for tape is not moving around the cylinder. This is the the subtractive primary color usually called “blue.” job of the cylinder servo signal.

74 D

D 1. CATV midband channel, 138-144 MHz. 2. PAL that uses 1035 active lines. It does not accept the TV standard; ex-USSR, , , Czechoslo- new HDTV standard format of 1080 active lines. ANSI/ vakia, , . Characteristics: 625 lines/ SMPTE 277M and 278M are D-6 standards. frame, 50 fields/s, interlace—2:1, 25 frames/s, D-7 DVCPRO, Panasonic’s development of native DV 15,625 lines/s, aspect ratio—4:3, video band—6 component format which records an 18-micron MHz, RF band—8 MHz, visual polarity—negative, (18x10-6m, eighteen thousandths of a millimeter) sound modulation—F3, pre-emphasis—50 µs, track on 6.35 mm (0.25-inch) metal particle tape. gamma of picture signal—0.5, used band—VHF. DVCPRO uses native DCT-based DV compression at D-1 A professional/industrial noncompressed compo- 5:1 from a 4:1:1 8-bit sampled source. It uses 10 nent digital video tape format (19-mm tape) for very tracks per frame for 525/60 sources and 12 tracks high-end digital video tape decks that is capable of per frame for 625/50 sources; both use 4:1:1 sam- producing sophisticated visual effects. D-1 VTRs of- pling. Tape speed is 33.813mm/s. It includes two fer a separate black and white image from color 16-bit digital audio channels sampled at 48 kHz and image, a feature that allows the professional to ex- an analog cue track. Both Linear (LTC) and Vertical periment with color difference matting, color cor- Interval Time Code (VITC) are supported. There is a rection and perspective moves. In addition, D-1 can 4:2:2 (DVCPRO50) and progressive scan 4:2:0 handle simple and 3-D graphics and accurate scene (DVCPRO P) version of the format, as well as a high- matches. This flexibility in picture manipulation has definition version (DVCPROHD). made the D-1 format a popular tool in turning out D-9 (Formerly Digital-S) A 1/2-inch digital tape for- visual effects for broadcast TV. mat, developed by JVC, which uses a high-density D-2 A professional/industrial recording noncompressed metal particle tape running at 57.8mm/s to record a composite video tape format (19-mm tape) for me- video data rate of 50 Mbps. Video sampled at 4:2:2 dium- to high-end digital video tape decks. On a pro- is compressed at 3.3:1 using DCT-based intra-frame fessional/industrial level, there are two major digital compression (DV). Two or four audio channels are formats—D-1, the component digital standard, and recorded at 16-bit, 48 kHz sampling; each is indi- D-2, the composite digital standard. The former vidually editable. The format also includes two cue records the luminance and two color-difference chan- tracks. Some machines can play back analog S-VHS. nels digitally, while the latter, D-2, records such basic D-9 HD is the high-definition version recording at standard signals as NTSC and PAL. D-2 VTRs, which 100 Mbps. serve as playback and postproduction machines, of- D-9 HD A high-definition digital component format fer several state-of-the-art advances as well as com- based on D-9. Records on 1/2-inch tape with 100 pactness and higher quality than their rival units. Mbps video. D-3 A noncompressed composite video tape format D-16 A recording format for digital film images mak- (0.5" tape) for medium- to high-end digital video ing use of standard D-1 recorders. The scheme was tape decks. developed specifically to handle Quantel’s Domino D-5 A noncompressed component digital video tape (Digital Opticals for Movies) pictures and record them format (0.5" tape) for very high-end digital video over the space that sixteen 625 line digital pictures tape decks. would occupy. This way three film frames can be D-6 A digital tape format using a 19-mm helical-scan recorded or played every two seconds. Playing the cassette tape to record uncompressed high-definition recorder allows the film images to be viewed on a television material at 1.88 GBps (1.2 Gbps). D-6 is standard monitor; running at 16x speed shows full initially the only high-definition recording format de- motion direct from the tape. fined by a recognized standard. D-6 accepts both the DA Distribution amplifier. A piece of equipment that European 1250/50 interlaced format and the Japa- produces multiple outputs identical to its input nese 260M version of the 1125/60 interlaced format signal.

75 DA-88

DA-88 A Tascam-brand 8-track digital audio tape ma- DATV channel See Bandwidth reduction (EUREKA-95 chine using the 8mm video format of Sony. It has HDMAC system). become the de facto standard for audio post-pro- DATV signal Digitally assisted TV signal. duction, although numerous other formats exist, DAVIC Abbreviation for Digital Audio Visual Council. ranging from swappable hard drives to analog tape It’s goal was to create an industry standard for the formats. end-to-end interoperability of broadcast and inter- DA-C, D/A Digital-to-analog. active digital audio-visual information, and of mul- daisy chain Refers to a single playback VCR, used as timedia communication. The specification is now “master” in a duplicating process, feeding more than ISO/IEC 16500 (normative part) and ITR 16501 one machine. The recording units are called “slave” (informative part). units. Many home VCR owners have gotten together day/event Refers to a VCR’s programming capabili- in this manner to duplicate videotapes. However, ties. “Day” pertains to the length of time a machine signal loss is bound to occur if too many machines can record in advance; e.g., 14 days, 1 year, etc. are connected. A video distribution amp may be “Event” points out the number of programs the VCR employed to increase the signal level. can record in that time period; e.g., four events over damper A diode in the horizontal deflection circuit of 21 days. a TV receiver that makes the sawtooth deflection day modulation A means of doubling the use of a current decrease smoothly to zero instead of oscil- radio channel by transmitting two carrier waves in lating at zero. The diode conducts each time the quadrature, each separately modulated with differ- polarity is reversed by a current swing below zero. It ent signals. incidentally provides B+ boost voltage. day picture A photo of a scene depicting the weather, dark clip After emphasis, the negative-going spikes used by newspaper and TV assignment editors. (undershoot) of a video signal might be too large in dB Decibel, a standard unit for expressing relative amplitude for safe FM modulation. A dark clip cir- power, voltage, or current. cuit is used to cut off these spikes at an adjustable D.B. Delayed broadcast.

level. See White clip. D’B Transmitted blue color difference signal (SECAM); dark current Current in a photoelectric or photocon- D’B = +1.5(B-Y). ductive device when the device is supplied with its dBm Measure of power in communications. 0 dBm = normal operating voltages and there is no light on 1 mW, with a logarithmic relationship as the values the target. increase or decrease. In a 50-ohm system, 0 dBm = dark field brightness Unexcited field brightness. 0.223 V. DAT Digital audiotape. Dbrn Decibels with reference to noise. datacasting See Teletext datacasting. DBS Direct broadcast by satellite. Also direct broad- A technique that provides for the cast satellite, direct broadcast service, digital broad- transmission or storage, without noticeable infor- cast system. mation loss, of fewer data bits than were originally DBS HDTV The DBS service for HDTV occupies fre- used when the data was created. quencies in the 12- and 22-GHz bands, and the data recorders Machines designed to record and re- bandwidths of each channel have been set at 24 play data. They usually include a high degree of er- MHz (in the Americas) and 27 MHz (in Europe and ror correction to ensure that the output data is ). FM is used with approximately a 3-to-1 ratio absolutely correct and, due to their recording for- between the baseband modulation and the chan- mat, the data is not easily editable. This compares nel width. The maximum video bandwidth thus falls with video recorders that can conceal missing or in- between 8 and 9 MHz. The Japanese MUSE HDTV correct data by repeating adjacent areas of the pic- system operates with an 8.1-MHz video band, the ture and that are designed to allow direct access to European MAC system with 8.5 MHz. These band- every frame for editing. Where data recorders are widths are barely sufficient for a multichannel HDTV used for recording video there must be an atten- system, e.g., one using the 6-MHz NTSC channels dant “workstation” to see the pictures or hear the plus an auxiliary channel of 2-3 MHz. If the full chan- sound, whereas VTRs produce the signals directly. nel requirement for the NHK Hi-Vision system (up Typically VTRs are more efficient for pictures and to 30 MHz) is to be accommodated, the signal must sound while data recorders are most appropriate for be compressed in frequency. data. dBV Decibels above/below 1 V (in video, relative to 1 data slicing The process of extracting digital data from V p-p). an incoming analog signal. dBW Decibels referenced to 1 watt. Datavision Videotex system, Sweden. dbx A noise reduction system designed to eliminate Datex-J Videotex service, Germany. It is the former unwanted sound from a program while still main- Bildschirmtext (BTX). Services: online-shopping, taining that program’s full audio range. By compress- home-banking, travel reservations and the like. ing a program before it is recorded and expanding

76 decibel

it during playback, dbx restores or recaptures the tion is essentially putting back a DC component that original dynamic range. A linear compression/expan- was removed to make an AC-coupled signal. We sion system similar to Dolby, CX and others, dbx don’t have to put back the original DC value—it covers the entire frequency range, yielding approxi- could be a different one. In decoding video, the DC mately 30 dB improvement in signal/noise over the level for DC restoration is such that the sync tip is whole band at mid-frequencies. It also provides bet- set to the ADCs REF- level. Therefore, when sync tip ter than 40 dB of noise reduction. is digitized it will be assigned the number 0. DC 1. Direct current. 2. Downconverter, satellite TV. DC restorer A clamping circuit used in video to re- DC-1 Digital pocket camera that captures motion and store the DC component of the video signal after sound; Ricoh Co. Ltd., Tokyo. DC-1 can record up to AC amplification. The resulting DC voltage also 492 still images, 100 minutes of sound, and, while serves as the bias voltage for the grid of the TV pic- not a video camera, can record short motion se- ture tube, to make average reproduced brightness quences (four video scenes of 5 s each). The effec- correspond to the average brightness of the scene tive resolution of the DC-1 is 380,000 pixels, being transmitted. Also called clamper, reinserter, comparable to S-VHS quality. and restorer. DC component The average value of a signal. In video DCSC Digital Color Space Converter; converts the it represents the average luminance of the picture. YCbCr signal to RGB. DC/DC converter An electrical circuit that accepts a DCT Discrete Cosine Transform. Used in the MPEG, direct-current input at one voltage level and con- H.261, and H.263 video compression algorithms. verts it to direct-current output at a higher or lower DC transmission TV transmission in which the DC voltage. This is typically accomplished by “chopping” component of the picture signal is still present. The the input DC, converting it to a coarse alternating true level of background illumination is thus main- current, then amplifying and rectifying the AC. For tained at all times. example, there is a DC/DC converter that steps up DCV Digital Compressed Video. 1.5-VDC of power cell to 12 VDC for operating por- DD CATV hyperband channel, 318-324 MHz. table TV sets. Circuit also permits operation from DD2 Using D-2 tape, data recorders have been devel- AC line. oped offering (by computer standards) vast storage DC inserter A TV transmitter stage that adds to the of data (which may be images). A choice of data video signal a DC component known as the pedestal transfer rates is available to suit computer interfaces. level. Like other computer storage media, images are not DC light A video camera feature that draws power directly viewable, and editing is difficult. from the internal battery of the unit for the pur- DDC Direct Drive Cylinder. poses of improving image detail. In addition, the DDR Digital disk recorder. feature is used to enhance color. Only a small num- DDS 1. Dynamic Drum System. 2. Direct Digital ber of cameras offer DC light. Synthesis. 3. Digital Data Service. DC picture transmission TV transmission in which dead 1. (of a conductor or circuit). At earth potential. the signal contains a DC component that represents A conductor or circuit not at earth potential is termed the average illumination of the entire scene. live or alive. 2. Exact or precise, as in dead sync. DC restoration 1. The capability of the TV monitor, dead roll A technique of starting a taped program or receiver or camera to respond to alterations in bright- a film at its scheduled time on a station but not ness as viewed by a video camera. The better the broadcasting it, so that the preceding program, spe- DC restoration, the greater the picture detail in night cifically a live sports or news event, is continued. scenes or low-lit shots. DC restoration makes use of When the live program ends, the dead rolling tape a special circuit that returns the direct current signal or film is telecast at the point it has rolled to, usually to the TV or camera outputs. 2. DC restoration is with the announcement, “We now join the program what you have to do to a video waveform after it already in progress.” has been AC coupled and has to be digitized. Since dead sync Exact synchronization of audio and video. the video waveform has been AC coupled, we no deaf aid A small earpiece used by TV reporters, an- longer know absolutely where it is. For example, is chors, and others. the bottom of the sync tip at –5 V or at 100 V? Is decay characteristic Persistence characteristic. the back porch at 3.56 v or at 0 v? In fact, not only decelerating electrode An electrode in a CRT biased don’t we know where it is, it also changes over time, so as to slow down the electron beam. It is usually since the voltage level of the active video changes in the form of a mesh or a short cylinder. Such an over time. Since the resistor ladder on the flash ADC electrode is used in low-velocity TV camera tubes is tied to a pair of voltage references, such as REF- such as the image orthicon in which the electron to 0 V and REF+ to 1.3 V, the video waveform needs beam is required to approach the target at a very to be referenced to some known DC level; other- low velocity. Syn.: decelerator. wise, we couldn’t digitize it correctly. DC restora- decibel (dB) One-tenth of a bel, used to define the

77 decibels with reference to noise

ratio of two powers, voltages, or currents, in terms of a particular thread design, a supplementary lens of gains or losses. It is 10x the log of the power ratio of one manufacturer may only fit that company’s and 20x the voltage or current ratio. The logarith- camera-equipped standard lens. The problem is mic ratio of power levels (usually satellite TV) or volt- even more prevalent with multi-pin connectors and age levels (usually conventional TV) is used to indicate adapters. gains or losses of signals. Decibels relative to 1 watt, de-emphasis Inverse of pre-emphasis, a reduction of milliwatt and millivolt are abbreviated as dBW, dBm the higher frequency portions of an FM signal (res- and dBmV, respectively. Zero dBmV is used as the toration of flat base-band frequency response after standard reference for all SMATV calculations. demodulation) used to neutralize the effects of pre- decibels with reference to noise A measure in dB of emphasis. Deemphasis performs a frequency-re- the signal-to-noise ratio on a communications line. sponse characteristic that is complementary to that decimation When a video waveform is digitized so introduced by pre-emphasis. When combined with that 100 pixels are produced, but only every other the correct level of pre-emphasis, it reduces overall one is stored or used, the video waveform is deci- noise levels and therefore increases the signal-to- mated by a factor of 2:1. The image is now 1/4 of noise ratio. Syn.: post-emphasis; post-equalization. its original size, since 3/4 of the data is missing. Deci- deemphasis network A circuit used to restore the mation is a quick-and-easy method for image scal- pre-emphasized frequency response to its original ing and is in fact the method used by low-cost form. systems that scale video into a window. deep Dark and rich (a deep red). In 3D TV camera decimation filter A filter designed to provide deci- systems with laser projectors, now it is preferred that mation without the artifacts associated with throw- the radiant energy of laser beam be out of the vis- ing data away. ible range of light that the video camera senses, decipher To remove the effects of a secret encryption therefore IR or deep red may be utilized. code or scrambling from data, restoring the code to defeat Turn off. an intelligible form. defeat filter In electronics, a filter which cuts any fre- deck A magnetic-tape transport mechanism. See VCR quencies in the band it rejects. Defeat filters, as well deck. as others such as bandpass filters, permit the boost- declination offset angle, satellite TV The adjust- ing and suppressing of selected material at a choice ment angle of a polar mount between the polar axis of frequencies. These filters are used in signal pro- and the plane of a satellite antenna used to aim at cessors to affect color and definition. the geosynchronous arc. Declination increases from defined display area The rectangular position of the zero with latitude away from the equator. display in which all text and pictorial images may be decode Decipher. presented. decoder A device used to alter data from one coded definition The degree or extent of detail or sharpness form to another. Contrasted with encoder. in a TV image. Definition depends on various fac- decoder box A device supplied by a pay TV system tors. With a camera, sharpness is affected by the designed to unscramble signals so that subscribers, quality of the lens, the lighting, etc. With a VCR, it who usually pay a monthly fee, can receive a clear is affected by the quality of the tape, the speed mode picture of a particular channel. Pay TV companies selected, the condition of the heads, etc. scramble their signals so that their channels appear deflection The orderly movement of the electron beam on screen as unintelligible to nonsubscribers. in a picture tube. Horizontal deflection pertains to decoding In general, the recovery of the original sig- the left-right movement, vertical deflection the up- nal from a coded form of the signal. In particular, in down movement of the beam. stereophonic radio reception, the recovery of the left deflection coils Coils (in a deflection yoke) external and right signals from the received signal to the CRT in TV systems with electro-magnetic scan- and in color TV reception the recovery of the three ning. Wound in two distinct sections, one each for primary color signals from the color video signal. line and frame, often on a single former, they de- decor The decorative scheme of an area, such as a flect the electron beam to scan the screen of the stage, or film or . CRT. Also called Deflector coils. dedicated chip A small piece of silicon imprinted with deflection defocusing Defocusing that becomes logic circuits. Used in early video games such as Pong, greater as deflection is increased in a CRT because these chips permitted the games to provide such the beam hits the screen at an increasingly greater basic activities as paddle movement. The games, slant, and its spot becomes increasingly more ellip- however, were non-programmable since the chip tical as it approaches the edges of the screen. was an inherent part of the game console. deflection electrode An electrode whose potential dedicated design A term applied to an accessory or provides an electric field that deflects an electron software which attaches to or fits equipment only beam. Also called deflection plate. of the same manufacturer. For example, because deflection factor The reciprocal of the deflection sen-

78 delta-array picture tube

sitivity in a CRT. Deflection factor is usually expressed sionals have isolated five other basic types of deg- in amperes per inch for electromagnetic deflection radation that affect NTSC picture quality—noise, and volts per inch for electrostatic deflection. intermodulation, microreflections, envelope delay deflection IC In TV sets, the deflection circuits usually and phase noise. have both the vertical and horizontal oscillator and Also progressive scan conversion. Inter- amplifier circuits in one IC component. You now find laced-to-noninterlaced conversion. the deflection circuits in one large IC with many dif- delay distortion Phase distortion in which the rate of ferent circuits. change of phase shift with frequency of a circuit or deflection plane A plane perpendicular to the CRT system is not constant over the frequency range re- axis containing the deflection center. quired for transmission. Also called envelope delay deflection plate Deflection electrode. distortion. It occurs on communication lines because deflection sensitivity The displacement of the elec- of differences in signal propagation speeds at dif- tron beam at the target or screen of a CRT per unit ferent frequencies. It can seriously impair data trans- of change in the deflection field. Usually expressed mission. See Distortion. in inches per ampere in a deflection coil. Deflection delayed automatic gain control An AGC system that sensitivity is the reciprocal of deflection factor. does not operate until the signal exceeds a prede- deflection voltage The voltage applied between a termined magnitude. Weaker signals thus receive pair of deflection electrodes to produce an electric maximum amplification. Also called biased auto- field. matic gain control. deflection yoke Complete assembly of horizontal and delayed broadcast (DB) The broadcast of a radio or vertical deflection coils in their special mounting. De- TV program at a time later than its original trans- flection yoke for TV picture tube contains four sepa- mission. rate coils. Syn.: scanning yoke. Also called yoke. delayed recall An interviewing technique to deter- defocus To make a beam of electrons, light, or other mine what an individual remembers. For example, radiation deviate from an accurate focus at the in- TV viewers are called the day after they have watched tended viewing or working surface. TV for at least half an hour and questioned about defocusing dissolve A TV technique in which one the programs and commercials regarding their opin- camera slowly goes out of focus while another cam- ions and the degree of idea communication and era slowly brings its image into focus. name registration. degausser Device to demagnetize color picture tube delay line (DL) Any circuit, device, or for color purity. that introduces a known delay in a transmission of degaussing Demagnetizing. In color TV sets, an inter- a signal. Coaxial cable or suitable L-C networks may nal or external circuit device that prevents or cor- be used to provide short delay times but the attenu- rects any stray magnetization of the iron in the ation is usually too great when longer delay times picture tube faceplate structure. Magnetization re- are required. Acoustic DLs are often employed (in sults in color distortion. TVs, VCRs, etc.) when a longer delay is needed. The degaussing coil A plastic-encased coil, about 12" (30 signals are converted to acoustic waves, usually by cm) in diameter, that can be plugged into a 120- means of the piezoelectric effect. They are then de- VAC wall outlet and moved slowly toward and away layed by circulation through a liquid or solid me- from a color TV picture tube to demagnetize adja- dium before being reconverted into electrical signals. cent parts. Fully electronic analog DLs are now being provided degradation The deterioration of the video infor- by CCDs. Shift registers and CCDs may be used for mation on a second tape that has been copied from digital DLs. another, or master, tape. Each generation removed delay line aperture control An electronic method of from the original or master adds to the degrada- improving contrast by artificially increasing the tion of the picture quality. Other factors besides strength of the original video signal. Similar to an- duplicating tapes can cause degradation. Some other technique known as horizontal image delin- methods of signal scrambling or encoding, for ex- eation, delay line aperture control strengthens the ample, may result in degradation of the original beginning and end of the signal as it repeatedly video information when it is decoded. On the other passes from black to white. hand, digital VCRs, as opposed to conventional delay-line cable A special cable in the black and white analog machines, maintain the integrity of the origi- channel of a color TV set that provided a time delay nal information. Using this process, signals con- just long enough to make the monochrome and verted into numbers not only are safe from chrominance signals arrive together at the CRT. Now distortion and noise, but can produce unlimited done digitally. copies without degradation. Since the digital sig- Del Rey HD-NTSC system HD-NTSC system. nal remains permanent, there is no loss in detail delta-array picture tube A shadow-mask color pic- with successive generations of recordings. Profes- ture tube the screen of which is composed of a very

79 delta factor

large number of color cells, each consisting of a dot machines only for playing back prerecorded tapes. of red, green and blue phosphor arranged in a delta Manufacturers, realizing this, have come up with (triangular) formation. several methods for making recording easier. These delta factor A term used in VCRs to indicate that a include OTR (one-touch recording for taping a show playback signal has some jitter or wow and flutter. presently being telecast), on-screen programming Delta factor or a change in frequency, means that (which guides the viewer step by step) and, finally, the color signal off the tape is not a stable frequency demonstration mode. of 629 kHz, but rather a signal whose frequency at demultiplexing Separating elementary streams or in- any instant is some small amount above or below dividual channels of data from a single multi-chan- 629 kHz. nel stream. For example, video and audio streams delta modulation A pulse-modulation technique in must be demultiplexed before they are decoded. This which a continuous analog signal is converted into is also true for multiplexed digital television trans- a serial bit stream which corresponds to changes in missions. analog input levels. depth default signal In 3D TV camera systems with demagnetization Removal of residual magnetism. laser projector, a signal to indicate that either (or demagnetizer A device for removing undesired both) sensors does (do) not receive sufficient re- magnetism. flected laser energy (for example, if the scene is very demagnetizing Removing magnetism from a ferrous distant) to output an electrical signal. In that case, it material. Also called degaussing. is necessary to set the depth video output to a “de- demagnetizing force A magnetizing force applied in fault” voltage, thus communicating that condition the direction that reduces the residual induction in to the receiver. Presence of a default value of depth a magnetized object. video would signal to the receiver monitor that it demand priority Access method providing support should treat those scene points as if they were at for time-sensitive applications such as video and “infinite” distance. multimedia as part of the proposed 100BaseVG stan- depth information In apparatus for direct display of dard offering 100 Mbit/s over voice-grade UTP an image on the retina of the eye using a scanning (Unshielded Twisted Pair) cable. By managing and laser, a perspective information that is provided by allocating access to the network centrally, at a hub the variable focus optical system to a laser beam at rather than from individual workstations, sufficient a suitable stage after optical modulation by the op- bandwidth for the particular application is guaran- tical modulating means, and the laser beam after teed on demand. Users, say its proponents, can be scanning in response to a scanning signal by the assured of reliable, continuous transmission of in- scanning means is focused to form an image on the formation. retina of an eye. demassified media Channels of communications, or depth matrix In 3D TV receiver systems, a circuitry to media, that reach small or selective audiences, as combine the depth video signal and the horizontal opposed to . sweep signal H in accordance with the equation: demodulation The reverse of modulation. The pro- H’ = cD + H; “c” is a constant between +1 and -1, cess of recovering an original signal from a modu- “D” is the instantaneous depth position with D = 0 lated carrier, for example the process of converting corresponding to the position of a reference frontal a modulated RF carrier signal to a form that can be place or “window,” H’ is the modified horizontal heard or displayed. sweep signal. The horizontal sweep signal H’ will demodulator A circuit that separates or extracts the thus be a nonlinear sweep signal. desired signal, such as sound energy or picture in- depth-multiplex recording The process of recording formation, from its carrier. In video, demodulation hi-fi audio on VHS hi-fi VCRs. The system uses sepa- is the technique used to recover the color difference rate rotating heads to record the audio portion. signals in NTSC, SECAM or PAL systems. Chroma depth of field Refers to the range of focus of a cam- Demodulator and Color Decoder are two other era lens, or, in other words, that which is in focus names for a demodulator used in a video applica- behind and in front of a subject. Depth of field tion. For SSTV, a device that extracts image and sync changes with the lens opening (the smaller the open- information from an audio signal. ing, the greater the depth of field), the distance be- demonstration mode A feature on some VCRs de- tween subject and camera (the closer the subject, signed to help the user understand the various pro- the shorter the depth of field) and the type of lens gramming functions. The demonstration mode leads (wide angle lenses provide greater depth of field than the user through these functions and the contents telephotos). of the several on-screen menus. Time shifting, or depth of focus The allowable latitude of lens image setting up the VCR to record one or more programs plane to vidicon target area that ensures that a given at a later time or day, has been a difficult operation picture remains in focus. Depth of focus is adjusted for many VCR owners who simply end up using their by moving the vidicon closer to or farther away from

80 Deutshe Industrie Normenausschus

the end of the lens. Not normally used in video as a ing—an image in software to compensate for a focusing adjustment. crooked scan. depth of modulation chart A method of measur- desktop video 1. The combination of computers and ing the sharpness of a video camera. The chart con- video; the creation and editing of video images on a sists of a predetermined pattern of short vertical computer. Desktop video refers to three basic appli- lines spaced according to “bursts” that are cali- cations: Videotape editing; Special effects and graph- brated in MHz. The bursts range from 0.5 to 4 MHz. ics; Digital video editing. There are two other Depth of modulation, or modulation transfer func- applications that incorporate elements of desktop tion, refers to determining the “quantity” of reso- video, but can’t really be considered desktop video lution or sharpness of an image. Normally, the per se: interactive multimedia (like CD-ROM) and degree of sharpness is highly subjective. Depth of TV tuners for computers. 2. Communications that modulation charts seek to remove this aspect, re- rely either on videophones or PCs offering a video placing subjectivity with mathematical calibrations window. See Desktop videoconferencing. that result in percentages. For example, a pattern desktop videoconferencing Delivery system for pro- can now be considered properly registered if the viding two-way voice and full-motion color pictures. depth of modulation totals 80%. Depth of modu- Since video calling takes place on a PC, you can share lation problems, such as dark objects appearing information—computer companies call this data or light or light objects becoming darkened, may be document conferencing. Desktop videoconferencing the result of a faulty camera or lens. products must be connected to either a PC network depth perception A subjective evaluation of the dis- or ISDN phone lines. The system offers convenience, tance between objects viewed with regard to their privacy, and the useful combination of video calling size and the planes they describe. and data sharing. Also called personal depth video signal In 3D TV systems, a signal con- videoconferencing. taining 3D-image information. detail enhancement circuitry An image processing derivative equalizer An equalizer that operates by technique designed to add contrast and produce adding to the signal to be equalized controllable sharper outlines to images. An electronic circuit splits amounts of the time derivates of the signal. Such the incoming video signal and sends it along two equalizers are used in TV transmission for correct- paths, one ignoring the split signal and the other ing waveform distortion in video circuits and nor- modifying the black-to-white transitions so that cer- mally only the first and second derivatives are used. tain objects appear sharper. The two signals are then desaturation Reduction of color saturation often as joined to produce a better image. result of distortion or defect in the TV transmission detail enhancer Refers to electronic circuitry built into system. a VCR to help deliver a clear screen image during descrambler A device which corrects a signal (often playback. This electronic feature is usually part of video) that has been intentionally distorted to pre- the HQ circuitry of many VCRs. Sometimes described vent unauthorized viewing. Used with satellite TV as a “detail switch,” this feature may have two set- systems. tings—one for use with conventional videocassettes Descriptive Video Service (DVS) Video for the blind. and another for HG (High Grade) tapes for produc- In 1990, Boston PBS station WGBH launched the ing sharper images. Emmy-winning DBS. Via the SAP channel available detailer Image enhancer. on stereo TVs and VCRs, DVS soundtracks describe detail set A part of a set used for closeups in film and visual elements—facial expressions and body lan- TV; also called insert set. guage, costumes, sets, scene changes—during detector 1. Syn.: demodulator. A circuit that was used pauses in dialog. The descriptions are written in a in older TVs to demodulate the received signal— prose-like style to help bring listeners more fully into i.e., to extract the signal from a carrier with mini- the program. mum distortion. 2. In an optical communications descryption A process of decoding or unscrambling receiver, a device that converts the received optical TV signals, as with pay-TV services. signal to another form. Currently, this conversion is deserializer A device that converts serial digital infor- from optical to electrical power; however, optical- mation to parallel digital. to-optical techniques are under development. Designated Market Area (DMA) An A.C. Nielsen Co. detent A part that stops or releases a movement. term for a group of counties in which a TV station detent tuner “Click” type of TV tuner. obtains the greatest portion of its audience. Each detent tuning 1. Tuning into a satellite channel by US county is part of only one such DMA. The DMA selecting a preset resistance. 2. A TV receiver tuning rating is the percentage of TV homes within the area control in which a detent mechanism determines viewing an individual station during a particular the correct position of the tuning shaft for receiving period. a desired station. deskewing An imaging term. Adjusting—straighten- Deutshe Industrie Normenausschus (DIN) A Ger-

81 deviation

man institute that sets industrial standards. In the audio track along with the diagonal video track for audio field, plugs and sockets having DIN geometry better quality. In contrast to linear stereo, or linear are used throughout the world. track stereo as it is sometimes called, the superior deviation The level of modulation of an FM signal— Beta or VHS Hi-Fi technique uses diagonal audio the extent by which the base-band of subcarrier sig- recording. nal shifts the main carrier frequency. In VHS the upper dial A panel on a radio or TV set on which the fre- limit is 4.4 MHz. quencies are indicated. device control A multimedia definition. Device con- diamond display See Synthetic diamond display. trol enables you to control different media devices diaphragm 1. A thin flexible sheet that can be moved over the network through software. The media de- by sound waves, as in a microphone, or can pro- vices include VCRs, laser disc players, video cam- duce sound waves when moved, as in a loud- eras, CD players, and so on. Control capabilities are speaker. 2. An adjustable opening used in TV available on the workstation through a graphical user cameras to reduce the effective area of a lens to interface. They are similar to the controls on the increase the depth of focus. Also called iris. 3. A device itself, such as play, record, reverse, eject, and conducting plate mounted across a waveguide to fast forward. Device control is important because it introduce impedance. enables you to control video and audio remotely— diascope A built-in test pattern that allows the TV without requiring physical access. camera to generate test signals for registration and dew detector A passive device, found in some VCRs, other setup adjustments without the use of an ex- whose resistance value depends upon ambient hu- ternal test pattern. It is a useful feature of many midity; the resistance drops when moisture is lenses. present. Also called dew sensor. diathermy interference TV interference caused by dew indicator A warning light that goes on when there diathermy equipment. It produces a herringbone is too much moisture in the atmosphere. This feature pattern in a dark horizontal band across the picture. appears on many VHS machines but on few Beta dichroic Having two colors. VCRs. Simple remedies consist of shutting off the dichroic conversion filter A camera lens filter that machine for a while, using a hair blower near the balances the color values of objects in direct sun- VCR to minimize the moisture, putting on the air con- light so they will match the value of scenes shot ditioner, etc. Some machines have a dew control that under artificial light. shuts off the VCR when moisture is excessive. dichroic daylight conversion filter A lens filter that dew sensor Dew detector. balances the color values of objects in direct sun- DFM SSTV bandpass filter A bandpass filter espe- light so that they will match the values of scenes cially designed for SSTV. taped in artificial light. DG . Change of the chrominance am- dichroic filter An optical filter designed to transmit plitude (i.e., chrominance gain) as function of lumi- light selectively according to wavelength (most of- nance level. In a color video channel, the voltage ten, a high-pass or low-pass filter). gain for a small chrominance subcarrier signal at a dichroic mirror A glass surface coated with a special given luminance signal level expressed as a percent- metal film that reflects certain colors of light while age difference relative to the gain at blanking or allowing other colors to pass through. Used in some some other specified level. Can cause changes of color TV cameras to reflect one designated visible hue with changes of level. frequency band and transmit all others. DG/DP Differential gain/phase. dichroic reflector (mirror) Selectively reflecting sur- D/I Drop and insert. A point in the transmission where face from which light of certain wavelengths is re- portions of the digital signal can be dropped out flected and other incident wavelengths transmitted. and/or inserted. For example, a dichroic surface may be made which DIA/DCA Document Interchange Architecture/Docu- reflects only the longer wavelengths correspond- ment Content Architecture. IBM-promulgated archi- ing to the red region of the spectrum and trans- tectures, part of SNA, for transmission and storage mits the remainder, so that the light transmitted is of documents over networks, whether text, data, blue-green in color. Dichroic reflectors have par- voice or video. Becoming industry standards by de- ticular application in color processes involving fault. beam-splitting systems since they permit very effi- Diagnostics Tests to check the correct operation of cient subdivision of the available light into the re- hardware and software. As digital systems continue quired spectral regions. In the TV camera, dichroic to become more complex, built-in diagnostics be- filters may be used to analyze the subject in terms come an essential part of the equipment. of the separate primary colors. Red and blue re- diagonal audio recording Another method of re- flecting dichroics, in conjunction with plain front- cording sound on videotape, as opposed to linear surfaced mirrors, direct the red and green audio and stereo. Diagonal recording places the components to their respective pick-up tubes. The

82 digital effects

green tube takes the remaining image after its pas- because the signal is component digital. This means sage through both dichroics. the video signal is broken into its two pieces, or com- differential gain (DG) How much the color satura- ponents: luminance (black and white information) tion changes when the luma level changes (it isn’t and chrominance (color information). The informa- supposed to). The result on the display will be incor- tion is converted into a digital data stream, which is rect color saturation. For a video system, the better then recorded on the tape. This format also has four the differential gain—that is, the smaller the num- independently editable CD quality audio channels. ber specified—the better the system is at figuring digital clock The component of a VCR or a tuner/ out the correct color. timer serving a dual function: time-keeping and time- differential gain/phase Video (color) nonlinear dis- setting for unattended recording. Usually different tortion parameters. controls set the clock or the timer. differential nonlinearity (DNL) A measure of the digital color art A VCR feature that permits the viewer maximum amount by which the distance between to place a tint over the video image. Provided the the midpoints of adjacent steps on the ADC trans- VCR is equipped with the necessary digital circuitry, fer function (quantized output level) differs from the this digital playback function offers the viewer a width of one LSB. choice of several colors from which to choose. (DP) Change of the chrominance digital color space converter (DCSC) A circuitry that phase as function of luminance level. The result on converts the YCbCr signal to RGB. the display will be incorrect colors. For a video sys- Digital video using sepa- tem, the better the differential phase—that is, the rate color components, such as YCrCb or RGB. See smaller the number specified—the better the sys- CCIR 601. Sometimes incorrectly referred to as D-1. tem is at figuring out the correct color. digital composite video Digital video that is essen- differential pulse code modulation (DPCM) Refers tially the digitized waveform of composite NTSC or to a digital system in which the data transmitted or PAL video signals, with specific digital values assigned stored represents the difference between data ele- to the sync, blank, and white levels. Sometimes in- ments (for images it is pixels), rather than the data correctly referred to as D-2 or D-3. elements themselves. See also Prediction. digital compression A process designed to permit DigiCipher Proposed fully digital HDTV system, Ameri- full-motion video to be sampled, stored in a com- can TV Alliance (ATVA). Operated with a 1050-line puter, and played back in real time. MPEG compres- analog RGB input. The scan was interlaced 2:1, and sion is the current standard. the field rate was 59.94. The line rate, twice that of digital delay line See Delay line. NTSC, was chosen to allow easy conversion of sig- digital disk recorder (DDR) A video recording device nals between the two systems. using a hard disk drive or optical disk drive. DDRs digital Of or referring to a quantity that is expressive afford nearly instantaneous access to recorded numerically. See also Digitization. material. Digital 8 Digital 8 compresses video using standard digital effects A series of special image enhance- DV compression, but records it in a manner that al- ments resulting from digital circuitry built into some lows it to use standard Hi-8 tape. The result is a DV VCRs, TV sets and video cameras. For example, a “box” that can also play standard Hi-8 and 8 mm VCR equipped with this circuitry can produce steady tapes. On playback, analog tapes are converted to a still pictures without the usual streaks and other vi- 25 Mbps compressed signal available via the i-Link sual interferences that often accompany this func- digital output interface. Playback from analog tapes tion. These stills can be obtained from a live has limited video quality. New recordings are digital broadcast as well as from a videotape. In addition, and identical in performance to DV; audio specs and the audio portion of the program continues while other data also are the same. the still remains on screen. Other features of digital digital advanced television An alternate term for circuits include noise reduction, PIP, slow motion high-definition television (HDTV). (without video interferences) and a quick succession digital audio processor A device that is used in con- of still pictures known as strobe display. Strobe dis- junction with any standard VCR to record digital play, which differs from the conventional continu- audio tracks on videotape. ous slow motion function, produces images without digital audiotape (DAT) An audiotape designed for interference and offers a wider range of slow mo- use in systems that employ digital, rather than ana- tion. Digital circuitry also allows the viewer to watch log, recording technology. DAT cassettes are more two pictures at the same time. Some VCRs apply compact than conventional audio cassettes and are digital techniques to improve the overall image qual- used for data and image storage as well as audio. ity of poorly recorded tapes. Advanced circuitry ac- Digital Betacam A VCR format introduced by Sony in complishes these feats by digitally “capturing” video 1993. It is a high-quality digital format that can frames from the moving videotape and parading record 100 generations without signal degradation them on the TV screen. Unlike conventional VCRs,

83 digital encryption

which use analog signal processing, machines with acteristic of DLP-based display offers a unique capa- digital circuitry also reduce the graininess of multi- bility to simultaneously display video, graphics and generation tapes. text that provides optimum performance for multi- digital encryption An electronically advanced method media applications. of encoding or scrambling video information for digital light switch See Digital Micromirror Device. security purposes. Digital encryption, which re- Digital Micromirror Device (DMD) All-digital display phrases original video information line by line, is system, completely compatible with digital broad- generally a more costly procedure than its counter- casting, requiring no D/A conversion; Instru- part, analog encryption, but results in a higher quality ments (TI). TI calls DMD a digital light switch. DMD video image after the information is restored or de- has an array of hundreds of thousands of aluminum coded. The digital system requires a larger band- mirrors fabricated on a silicon chip. Each tiny mirror width than does the analog technique, which uses represents one pixel. When a voltage is applied to a the standard 4.5-MHz bandwidth. mirror, it pivots slightly, reflecting light from an ex- digital field comb filter A feature, usually found in ternal light source through a projection lens onto a advanced TV sets, that greatly reduces the NTSC in- screen. When in the “off” state, light reflected from terference effects often accompanying conventional the mirror doesn’t enter the lens. TV sets. These special comb filters surpass the per- digital monitor Computer monitor that accepts digi- formance of standard line filters by delivering as tal in addition to analog signals. DVI is the standard many as 480 lines of horizontal resolution from wide digital video interface. band sources such as DVD and S-VHS tapes. digital multi-audio A feature built into a few VCRs digital gain-up A feature, found on some video cam- that assigns auxiliary audio tracks to the videotape eras, that enhances image contrast through the use in lieu of video information. With Hi8 VCRs, e.g., of special electronic circuitry. Digital gain-up is par- digital multi-audio permits up to 24 hours of audio ticularly important in improving pictures shot under recording. extremely low light conditions. Some camcorders digital multi-effects system A professional/industrial advertise a digital gain-up circuitry response of 1 lux. system designed chiefly for TV stations that is ca- digital image superimposer A video camera feature pable of manipulating flat video images into 3-D designed to electronically store high contrast images. images in real time. In addition, the system can pro- These images are usually used for a variety of pur- duce such effects as sparkle, degrade (image poses, such as superimposing titles, graphics or cap- breakup) and centipede (elongation of an object or tions. When the user activates the button of this subject). feature, the digital superimposer memorizes an im- digital noise reduction See Digital video noise age. Some cameras provide a built-in superimposer reduction. with a 4-page, 8-color memory. The digital image digital oversampling See Oversampling. superimposer, also known as a digital superimposer digital paint art A feature, found only on digital VCRs, or word register, is more sophisticated than a char- that produces a rough gradation to a screen image acter generator. The latter also creates titles but more to simulate the effect of an oil painting. Digital paint slowly and with limited typefaces. art usually offers several levels of contrast. digital intro scan This function scans the videotape See Still video camera. and plays about 10 seconds of the beginning of each digital picture memory An advanced electronic fea- program (the part immediately following each en- ture, found on some VDPs and VCRs, which permits coded index signal) then freezes still images onto the audio portion of a program to continue while a the three subscreens. picture “freezes” on the screen. digital leased-line service (DLS) A system with a 634- digital remote control A remote control in which the km fiber-optic network, handling 48 TV channels or user selects or adjusts a desired function by punch- carrying 2.5 billion bits information per second; ing out one or more digits on a calculator-like key- Dacom, Seoul, . board. Applications include direct selection of TV digitally assisted television signal (DATV signal) A programs by channel number. In one version used signal of the HDMAC system. It is transmitted dur- for remote control of color TV, an ultrasonic receiver ing the vertical field interval of 1/50 second = 2000 converts the 14 possible ultrasonic frequencies into microseconds. This time permits a maximum bit rate digital codes that control the desired ON/OFF, chan- of 1 Mb/s, but after allowance for error correction, nel-select, color, tint, and volume functions. a maximum bit rate of 960 Kb/s is available. A prin- digital rights management (DRM) Digital rights cipal function of the DATV signal bit stream is to management is a generic term for a number of ca- keep the branch-switching in precise synchronism pabilities that allow a content producer or distribu- at the transmitter and receiver. tor to determine under what conditions their product digital light processing (DLP) A completely digital can be acquired, stored, viewed, copied, loaned, etc. approach to projection display. The all-digital char- Popular proprietary solutions include InterTrust, etc.

84 digital television standards converter digital satellite system (DSS) A digital system, offer- still-frame, eliminates these interferences. In addi- ing 400 to 500 lines of resolution and CD-quality tion, still-frames can be acquired from live broad- audio. Compared to the 330 lines of resolution cur- casts as well as videotape. rently available on TV, or the 260 lines of resolution digital stereo In VCRs, the enhancement of audio by on VHS tapes, this is a major step up. In your home, means of special digital and error-correction circuitry the system consists of a small 18" satellite dish that virtually eliminates interference. Discrete right mounted outside your home and an integrated re- and left digital audio signal processing helps to pro- ceiver/decoder (IRD), about the size of a VCR, which duce a dynamic range of over 90 dB. Digital stereo sits near your TV. A telephone line plugs into the has proven effective with video cameras as well. This back of the receiver, either directly or through an is especially true with digital audio dubbing, which optional wireless transceiver, so that you can order adds hi-fi sound to special effects and music. programming and other services directly through the Digital Storage Media Command Control (DSM-CC) telephone line. DSS uses both MPEG-1 and MPEG- See Multi- and Hyper-media coding Experts group. 2 digital compression and decompression. Some digital superimposer See Digital image superimposer. systems are switching to MPEG-4. See also RCA DSS, digital S-VHS An experimental audio enhancement SAS-AD1. process that records audio signals in a lower level of digital scan A feature on specially equipped VCRs de- a videotape than conventional video signals. The signed to allow the viewer to see a picture in FF or digital system is compatible with existing S-VHS re- REW mode. Only some VCRs with digital effects in- corders and S-VHS-C camcorders. Developed by JVC, clude this function. which calls the process D-MPX (depth-multiplexed digital servo transport circuitry A VCR system that signal AC bias recording system), digital S-VHS prom- controls both the capstan and head-drum motors ises benefits for both consumer and professional ap- to provide better track positioning. Some motors may plications. The system provides a sampling frequency produce phase and frequency errors. These defects of 48 kHz in 2-channel mode and 32 kHz in 4-chan- in destabilization are sensed and corrected by a crys- nel mode. tal oscillator. Image quality depends upon accurate digital switcher A professional/industrial unit that tracking, which, in turn, relies upon the precision speeds up component digital editing by providing and rigidity of the motors. Imprecise tracking may additional sophisticated capabilities to the produc- result in audio wow-and-flutter or picture jitter or tion switcher, including multi-layer compositing in both. real time and color correction functions. In addition, digital signal processor (DSP) A specialized digital digital switchers can accommodate several chroma microprocessor that performs calculations on digi- keyers simultaneously to isolate different areas dur- tized signals that were originally analog (e.g., video) ing the composite procedure. See Switcher. and then sends the results on. The big advantage of digital sync A TV feature that eliminates the need for a DSP lies in the programmability of digital micro- a manual vertical hold control. Digital sync automati- processors. cally produces vertical hold modifications by sens- digital signal sound processor An accessory designed ing variations in video sync and locking into the to offer a simplified version of surround sound au- correct reference for vertical adjustment. dio effects. Usually composed of dual speakers, an digital television (DTV) repre- amp and digital delay circuits, the sound processor sents a more efficient means of transmitting a broad- comes equipped with jacks for hooking it up to VCRs cast signal than the analog delivery system. Up to or TV receivers. The unit can be used without the 12 SDTV programs can fit into the spectrum space complex wiring often necessary for surround sound. occupied by one analog program. In the U.S., the Digital Spectrum Compatible (DSC) A proposed fully FCC has mandated a transition to DTV for broad- digital HDTV system, Zenith/AT&T. Operated with casters. See HDTV. progressively scanned baseband video at 787.5 lines digital television converter A converter used to con- per frame and 59.94 frames/s. The line-scan rate vert TV programs from one system to another, such was 47,203 Hz, three times that of the NTSC sys- as for converting 525-line 60-field US broadcasts to tem to permit easy conversion between the two sys- 625-line 50-field European PAL or SECAM standards. tems. DSC used the discrete cosine transform coding The video signal is digitized before conversion. Also as a basis for its spatial compression. called digital television standards converter. digital still-frame memory An electronic feature, digital television standards converter A professional found on some VCRs and video cameras, that can electronic accessory which uses digital technology to play back single frames with perfect steadiness. VCRs convert different broadcasting and recording stan- and cameras with digital circuitry usually provide dards of other countries. Ordinarily incompatible stan- unstable freeze frames containing electronic inter- dards such as SECAM, PAL and PAL M are connected ference or video noise in the form of lines, streaks to the TV converter, which processes the signal for or snow. Digitally produced special effects, such as line and field conversion. A memory output compen-

85 digital tracking

sates for distortion usually caused by such conver- replaces the conventional dial readout, does away sion. The converter also operates with satellite broad- with the need for a manual tuner. casts of foreign programs. Other functions of the digital TV receiver A TV set designed to produce su- device include its use as an editor, mixer and frame perior audio and video through the use of digital synchronizer to integrate local shows into network encoding of the broadcast signal. Instead of the programs. Also called digital television converter. conventional method of analog signal processing, digital tracking A VCR feature, most notably on some the digital system uses large-scale integrated circuitry. S-VHS models, that automatically compensates for Some of these chips digitally decode the video sig- disparities in viedotapes recorded on different ma- nal and process it while another handles the audio chines. Occasionally, a tape recorded on one ma- in a similar manner. Meanwhile, another special cir- chine may not play correctly on another VCR because cuit in the TV receiver controls the tuning, power the video heads or video head drums of the two supply and other components. Digital TV recon- machines may not be positioned at the same exact structs the signal more accurately than its counter- height. This difference causes video noise or bars to part, the analog process, which tends to lose much appear on the TV screen. The viewer may eliminate of the original quality. However, the relatively higher this interference by manually adjusting the tracking cost of this technique has affected its general ac- or skewing control dial. Digital tracking (sometimes ceptance in the marketplace. called twin digital tracking), when activated, will cor- digital VCR A VCR that uses special electronic circuitry rect the video signal automatically and optimize play- to store and process information using electrical back in any of the speed modes. Another advantage pulses to represent numbers. Video signals, which of digital tracking is that the user does not have to are waveforms, are normally recorded in analog form return the tracking control to its default position. along with inherent video noise, or electronic inter- This adjustment is necessary on VCRs without digi- ference. Digital machines, on the other hand, con- tal tracking to prevent future tapes from being re- vert video signals into a predetermined code, or set corded incorrectly. of binary numbers. This method virtually eliminates digital traffic Traffic consisting of digital data that video noise to produce an improved screen image may or may not be combined with voice, video, or and clearer special effects such as freeze frame, slow other forms of analog information which has been motion, PIP, strobe display, mosaics and converted to a format suitable for pulse-code posterization. Digital VCRs, first introduced to the modulation. general public in 1986, offer other benefits. For in- digital transcoder An accessory designed to convert stance, viewers can call up two different programs digital signal formats from D-1 to D-2 VTRs and vice simultaneously on their TV screens. In addition, sig- versa. The transcoder is used chiefly with industrial nals converted into numbers not only are safe from tape machines. distortion and noise, but can produce unlimited cop- digital transfer A technique that uses digital circuitry ies without degradation. Since the digital signal re- to transfer wide-screen theatrical films to video. Digi- mains permanent, there is no loss in detail with tal transfer, which is superior to other, older meth- successive generations of recordings. ods, produces better image quality while providing Digital Versatile Disc (DVD) Compact discs that hold special sophisticated effects such as enlarging im- over two hours of digital audio, video, data, and ages, zooming in and out and simulating the origi- graphics. The video is compressed and stored us- nal movements of the . ing MPEG-2. Beginning to replace VHS as the stan- Digital Transmission Content Protection (DTCP) An dard for in-home video viewing. See also Digital encryption method (also known as “5C”) developed videodisc. by Sony, Hitachi, Intel, Matsushita and Toshiba for Digital Vertical Interval Timecode DVITC digitizes IEEE 1394 interfaces. the analog VITC waveform to generate 8-bit values. Digital Transmission of Increased Capacity (DTIC) This allows the VITC to be used with digital video Parallel transmission of data across the channel; Digi- systems. For 525-line video systems, it is defined by tal Compression Technology () and SMPTE 266M. BT.1366 defines how to transfer VITC Stevens Institute of Technology (Hoboken, N.J.). Used and LTC as ancillary data in digital component in digital signal compression technique that permits interfaces. existing communication systems to transmit the digital video 1. A system where all of the information same volumes of advanced voice, video and data as that represents images is in some kind of computer state-of-the-art optical fiber. The patented technol- data form, which can be displayed or manipulated ogy is based on a breakthrough algorithm that com- by a computer. Digital video specifically excludes presses signals, at a ratio 16:1 in channel, rather analog video, where images are represented by con- than at the source as with MPEG. tinuous-scale electrical signals. 2. A video signal rep- digital tuning The use of quartz crystals that are tuned resented by machine-readable binary numbers that to each FM and AM frequency. Digital tuning, which describe a finite set of colors and luminance levels.

86 digital video stabilizer

3. A process of videotape recording with a potential access function. The last frame seen on screen is for more accurate color renditions and pictures of then stored in the buffer and appears until the new higher resolution. Conventional recordings use the material is located. analog system of placing information on tape. On a Digital Video Interactive (DVI) technology (David professional/industrial level, there are two major digi- Sarnoff Research Center) A technology with the ob- tal formats—D-1, the component digital standard, jective of putting TV-style video and audio on a per- and D-2, the composite digital standard. The former sonal computer. Digital video interactive technology records the luminance and two color-difference made possible the first systems which truly merged channels digitally, while the latter, D-2, records such PCs and TV. The technology was first shown pub- basic standard signals as NTSC and PAL. MII is an- licly on March 1, 1987. The audiovisual material for other format competing for recognition. Digital com- this presentation was done entirely with the DVI sys- pression, another technique, is still in the tem, displayed on a large screen projector, showing experimental stage. slides from hard disk, motion video and audio from digital video camera A professional video camera CD-ROM, and application demonstrations. that has fewer moving parts and is generally lighter Digital video interactive technology consists of and smaller than its counterpart, the analog cam- four unique elements: era. First introduced by Panasonic in 1989, digital • A custom VLSI chip set, which is the heart of the video cameras can filter out video cross-color and video system can make any necessary adjustments automatically. • A specification for a runtime software interface The company also introduced the first digital • Some audio/video data formats camcorder, which has 1/2" format. • Compression and decompression algorithms. digital video cassette See DVC. digital video noise reduction Special electronic tech- digital video compression Reducing the amount of nology that improves signal-to-noise ratios by com- information necessary to reconstruct video frames bining two video fields. First introduced into S-VHS at the receiving end of a transmission. The electronic VCRs, this electronic video noise reduction system signals are squeezed and thus signal capacity can differs greatly from other attempts to reduce image be increased by factors of 8,10, or more. The pro- interference from video signals. Using special comb cess can expand the number of channels per satel- and notch filters, this new system, also known as lite transponder and create sufficient channel field correlation, adds a complete field of informa- capacity to make DBS systems practical, and is used tion to each succeeding field. Since both fields are in HDTV. Cable operations are able to transmit hun- almost identical, the signal power is therefore dreds of channels over a single fiber optic cable. doubled. Although distortion and video noise is in- Digital Video Disc (DVD) Refers to standards for herent in all video signals, the interference does not the higher density CD. DVD also stands for Digital double along with the enhanced dual-field video Versatile Disc. image. This results in a clearer screen image with- digital video effects system A professional/indus- out the usual additional video noise and wavy lines. trial workstation designed to produce numerous Several sophisticated VCRs with this digital feature, special video effects during the editing process. These sometimes listed as DVNR, offer several settings. units can be used for transitional or non-transitional They include one for use with prerecorded tapes, functions. Some transitional uses (dissolving from another to compensate for poor reception caused one scene to another) include warp, prism, curvilin- by a weak signal, and the usual on/off switch. The ear, montage, mirror, mosaic, sparkle, trailing, de- digital system, introduced by NEC in 1986, works cay, drop shadow, multi-freeze and rotation effects. with both broadcast signals and prerecorded tapes. In addition, a DVE system can be utilized to perform (DVR) DVRs can be thought non-transitional tasks, such as correcting errors in a of a digital version of the VCR, with several enhance- source tape. An intrusive shadow, window glare or ments. Instead of a tape, the DVR uses an internal overhead microphone can be removed by simply hard disk to store compressed audio/video, and has enlarging the picture and trimming it until the un- the ability to record and playback at the same time. wanted image does not appear. DVE units generally The main advantage that DVRs have over VCRs is cost thousands of dollars. their ability to time shift viewing the program as it is digital video frame storage A laser VDP feature de- being recorded. This is accomplished by continuing signed to retain one frame in memory, or in a buffer. to record the incoming live program, while retriev- This single frame appears on the TV screen until ran- ing the earlier part of the program that was just re- dom access search for a new segment is completed. corded. The DVR also offers pause, rewind, slow Before the introduction of this feature, VDPs would motion, and fast forward control, just as with a VCR. go to a black screen whenever random access was digital video stabilizer A device to eliminate video activated. Digital video frame storage operates au- copy guards. While watching rental movies, you may tomatically whenever the viewer presses the random notice annoying periodic color darkening, color shift,

87 digital video transmission

unwanted lines, flashing or jagged edges. This is sample. 2. A device that converts the position of a caused by the copy protection jamming signals em- point on a surface into digital coordinate data. bedded in the videotape, such as Macrovision copy digitizing The process of converting an analog signal protection. The digital video stabilizer eliminates copy into a digital signal. With images, it refers to the protections and jamming signals and brings you clear processes of scanning and A/D conversion. pictures. dihedral A term used to describe the relative position digital video transmission An experimental method between the two video heads as they are mounted that permits specially equipped VCRs to receive in the head cylinder. Perfect dihedral means that the rented or purchased movies by way of satellite. By tips of the heads are exactly 180 degrees apart. calling on the telephone, the consumer can order a diheptal base A tube base having 14 pins or possible movie to be transmitted to his or her VCR. Because pin positions. Used chiefly on TV CRTs. of the digital process, the rented film can usually be dilution Reducing the intensity of a color by adding recorded in about 10 minutes and can be played white. back two times. If the film is purchased by this DIN Deutsche Industrie-Norm. German standard for method, it can be played countless times. The only electronic connections. DIN plugs can be 3-, 4-, 5-, limitation, albeit a major one, is that at the present or 6-pin plugs, depending on their use, although time a satellite dish is required. Developers hope that they all have the same outer diameters and appear- in the future they can build receiving capabilities ance. DIN connectors were used in earlier Sony pro- directly into the VCR. fessional equipment. Today DIN plugs and digital zoom 1. A VCR feature that employs special connectors are still available in 3-pin and 6-pin con- electronic circuitry to produce various effects such figurations. as enlarging one portion of a screen image to full diode gun A small aperture, high-resolution gun found screen size. Some viewers may find this a useful in camera tubes for HDTV. method of examining an image more closely. The diopter A unit of measurement of a lens, equal to the digital zoom feature, which appears only on digital- power of a lens with a focal distance of 1 m, com- type VCRs, can be used on any segment of the monly used in eyeglasses. A lens with a plus (+) num- screen. For example, some digital VCRs can divide a ber of diopters is converging; a minus (-) number of screen picture into four parts with a fifth image ap- diopters is diverging. A plus diopter is used in TV for pearing in the center. This last image can be en- close-ups. See also diopter lens. larged four times its original size. 2. A camcorder diopter lens A feature found on the electronic feature that achieves a close-up effect not through viewfinder of some video cameras that permits mag- the optics of the lens, but via manipulation of the nification and adjustment for users who wear eye electronic signal. These digital telephoto shots gen- glasses. erally suffer from decreased resolution. DIP Dual in-line package; refers to integrated circuits. digitization The process of changing an electronic Specialized piece of equipment for joining analog signal such as a TV signal into a discrete nu- power radio feeds. A diplexer sometimes denotes a merical form. Digitization is subdivided into the pro- unit for combining two feeds of the same frequency cesses of sampling the analog signal at a moment (joining of parallel transmitters), sometimes for split- in time, quantizing the sample (assigning it a nu- ting a feed to two separate feeders (to feed two merical level), and coding the number in binary form. aerial arrays). A diplexer is also used in TV receiver The advantages of digitization include improved aerial systems, either for joining two aerials together transmission and repeatable quality; the disadvan- to a common feeder (e.g., Band I and Band III) or for tages include the need for more storage space than splitting the output of an aerial into separate bands the analog signal. Data compression works to re- for separate receiver inputs. duce that disadvantage. diplexing 1. The simultaneous transmission or recep- digitize To convert an analog or continuous signal into tion of two signals while using a common antenna, a series of ones and zeros—that is, into a digital made possible by using a device called a diplexer. format. Used in TV broadcasting to transmit visual and aural digitized video Today’s analog TV systems contain a carriers by means of a single antenna. 2. A process large number of digital subsystems. The signals used in which video circuits carry two full frequency au- by these are digitized representations of the com- dio channels, thereby making stereo TV possible. The posite NTSC, PAL, or SECAM TV signals and are re- two audio channels are transmitted above the video ferred to as digitized video. signal, the main one at 5.8 MHz and the other at digitizer 1. A device that converts an analog signal 6.4 MHz. Diplexing is capable of operating on tele- into a digital representation of that signal. Usually phone and microwave transmissions. implemented by sampling the analog signal at a direct broadcast by satellite (DBS) A method of regular rate and encoding each sample into a nu- broadcasting that uses a communications satellite meric representation of the amplitude value of the in geostationary orbit as the main transmitter. The

88

signal to be broadcast is transmitted from its point of the subject is viewed at a time by the TV camera. of origin on the earth to the satellite where it is re- Used in live TV broadcasting, whereas indirect or ceived, amplified, and retransmitted to cover a wide flying-spot scanning is sometimes used in industrial area. It is detected directly by individual receivers TV systems. using a suitable dish antenna tuned to the DBS direct-to-home (DTH) Satellite signals. systems providing television service direct to homes. Direct Broadcast Satellite (DBS) 1. A term commonly At present in the U.S., there are three commercially used to describe Ku-band broadcasts via satellite available systems: C-Band, DirecTV, and Dish Net- directly to individual end-users. 2. A satellite trans- work. See C-Band, DBS, and high power satellite mitting TV programs which can be received by small TV. fixed dish antennas often installed in backyards or DirecTV One of two DBS satellite companies in the on the roofs of houses. DBS services carry a large U.S. The other is Dish Network, owned by EchoStar. number of channels and directly compete with cable direct video/stereo audio inputs A TV monitor/re- TV. In the U.S., at present two companies offer DBS ceiver feature that permits the connection of a ste- service, DirecTV and EchoStar. reo VCR directly into the TV’s A/V inputs. This direct channel access Electronic channel selection. technique improves picture quality. In addition, the direct chapter search A videodisc feature, usually hookup provides stereo sound by way of the built- found on the wireless remote control component, in speakers of the monitor/receiver. that allows the user to access different programs on direct view A CRT or projected image that is watched the disc. directly, as opposed to a hard-copy print. direct copying See Copying. direct view TV Refers to conventional TV as opposed direct cross See Cross. to rear or front projection TV. Some large-screen di- direct-current restorer (DCR) A device that restores rect view monitors/receivers feature screens rang- the DC component or low-frequency component to ing from 27 to 40 inches, measured diagonally. a signal that has had its low-frequency components disconnect In CATV, telephone, and other fields, a removed by a circuit element with high impedance subscriber whose service has been terminated, to direct current. The device may also be used to usually for nonpayment. add DC or low frequency to a signal lacking these discrete cosine transform (DCT) A pixel-block based components. DCR is used in TV sets to reconstruct process of formatting video data where it is con- the original video signal. It is required either to re- verted from a three-dimensional form to a two-di- store the DC component to the received signal as in mensional form suitable for further compression. In AC transmission or to correct for the presence of an the process the average luminance of each block or unwanted spurious DC component. tile is evaluated using the DC coefficient. Used in direct-current transmission A method of transmis- the CCITT’s Px64 videoconferencing compression sion used in TV in which the DC component of the standard and in the ISO/IEC’s MPEG and JPEG im- luminance signal is directly represented in the trans- age compression recommendations. A DCT is a way mitted signal. See AC transmission. to represent an image. Instead of looking at it in the direct-drive capstan servo motor See VTR. time domain—which, by the way, is how we nor- direct drive cylinder As used in VHS, this means that mally do it—it is viewed in the frequency domain. the video heads are driven by a self-contained It’s analogous to color spaces, where the color is still brushless DC motor using no belts or gears. DDCs the color but is represented differently. In the same produce pictures with better stability. way that the YCbCr color space is more efficient directional microphone A microphone which is more than RGB in representing an image, the DCT is more sensitive to the sound in front of it, blocking any efficient at image representation. sound coming from its rear. It is preferred for re- discrete multi-tone See DMT. cording from a distance. discrete time oscillator (DTO) A digital version of the direct method See Color recording. voltage-controlled oscillator. direct pickup The transmission of TV images without discriminator A circuit that converts a frequency- intermediate photographic or magnetic recording. modulated or phase-modulated signal into an am- direct recording Recording that produces a record plitude-modulated signal. An audio detector in an immediately without subsequent processing, in re- FM receiver or TV sound circuit. Also, a detector per- sponse to received signals. forming a similar function in other frequency con- direct reflection Reflection of light, sound, or radio trol circuits, such as horizontal frequency control. waves in accordance with the laws of optical reflec- dish Jargon for a parabolic microwave antenna, used tion, as by a mirror. Also called mirror reflection, regu- for receiving line-of-sight terrestrial signals or sig- lar reflection, and specular reflection. nals from satellites. direct scanning A scanning method that illuminates Dish Network One of two DBS satellite companies the subject at all times and only one elemental area operating in the U.S. The other is DirecTV.

89 display display The visual presentation of information, usu- market other than the one in which the cable sys- ally on a TV-like screen or an array of illuminated tem is located. digits. The display may take the form of a CRT, LCD distortion 1. Any undesired change in the waveform or beam indexing. Hand-held or pocket TVs may use of a signal. 2. Any undesired deviation of an im- any one of these three types of displays. age from proportionality with the original scene. display list A list of commands placed in memory by Distortion is a significant problem in telecommuni- the host CPU. A display processor then interprets cation systems. There are several different types of and executes the display list commands indepen- distortion. dently from the activity of the host CPU. This is how Amplitude distortion occurs when the ratio of the two processors communicate while running in the root-mean-square value of the output to the parallel. r.m.s. value of the input varies with the amplitude display primaries Primary colors that, when mixed in of the input, both waveforms being sinusoidal. If proper proportions, produce other desired colors. harmonics are present in the output waveform only The three primaries usually used are red, green, and the fundamental frequency is considered. blue. Also called receiver primaries. Aperture distortion of an image occurs in a scan- display screen Refers to the presentation of various ning system when the scanning spot has finite di- kinds of information on the TV screen other than mensions rather than infinitely small dimensions. prerecorded or over-the-air broadcast programs. VCR Attenuation distortion occurs when the gain or displays may take the form of menus that permit loss of the system depends on frequency. Also called the viewer to program the unit to record events for frequency distortion. later viewing. Displays of some TV receivers provide Barrel and pincushion distortion are seen when on-screen menus for adjusting the color or audio the lateral magnification is not constant but depends portions of a picture, switching from one antenna on image size. Barrel distortion occurs when the source to another or confirming a channel selection. magnification decreases with object size, pincush- Many VDPs display, often by means of superimposed ion distortion when it increases with object size. images, such functions as chapter, track, frame, Coma is a plumlike distortion of the spot occur- speed, playback or scan direction. ring when the focusing elements of the electron gun display window That part of a VCR, located on the are misaligned. face of the unit, that provides the user with a vari- Crossover distortion occurs in push-pull opera- ety of information, such as tape counter, current tion when the transistors are not operating in the time, etc. If the VCR is programmed, the window correct phase with each other. will display the time, day, channel and number of Delay distortion is a change in the waveform shows to be recorded as well as the recording speed. because of the variation of the delay with frequency. Also, the display window shows Play, FF, Reverse and Harmonic distortion is due to harmonics not Rew modes when these have been activated. Dif- present in the original waveform. ferent models, depending on sophistication, offer Intermodulation distortion results from spurious other features, such as auto-rewind when tape has combination-frequency components in the output reached its end and an indicator light when a cas- of a nonlinear transmission system when two or sette is inserted. more sinusoidal voltages, applied simultaneously, dissector tube Image dissector. form the input. Intermodulation distortion of a com- dissolve 1. Fading between scenes without going to plex waveform arises from intermodulation (see black. 2. The merging of two TV camera signals in Modulation) within the waveform. such a way that as one scene disappears, another Keystone distortion is due to the length of the slowly appears. horizontal scan line varying with the vertical displace- distance change command In some autostereoscopic ment of the line. It is most pronounced when the 3D-image display systems, a command to provide electron beam is at an acute angle to the screen the image can be stereoscopically observed from a and results in a trapezoidal image instead of a rect- position of the designated distance. angular one. It can be removed using suitable trans- distance learning 1. Video and audio technologies mitter circuits. used in education so students can attend classes in Nonlinear distortion is produced in a system when a location distant from where the course is being the instantaneous transmission properties depend presented. 2. A Pacific Bell term for students sitting on the magnitude of the input. Amplitude, har- in front of TVs and phones and participating in monic, and intermodulation distortion are all results classes that are being held and delivered elsewhere. of nonlinear distortion. In one of PacBell’s trials, they used a T-1 signal, so Phase distortion of an image is seen in electronic the distant lecturer could see and hear his distant systems, such as CRTs, TV picture tubes, etc. It is students using full-color video. due to errors in the electron-lens focusing systems. distant signal In CATV, a station “imported” from a Trapezium distortion is a trapezoidal pattern on

90 DOC

the screen of a CRT instead of a square one and D-MPX See Digital S-VHS. occurs when the deflecting voltage applied to the DMD See Digital Micromirror Display. plates is unbalanced with respect to the anode. DMT Discrete Multi-Tone. A technology using digital See also Envelope delay; Field tilt; Foldover; Glitch; signal processors to pump more than 6 megabits/s Hook; Line tilt; Meshbeat; Shading signals; Smear. of video, data, image and voice signals over today’s distribution amplifier (DA) A piece of equipment that existing one-pair copper wiring. DMT technology is takes an input and gives multiple outputs of that actually a form of frequency division multiplexing same input. An RF power amp used to feed TV or (FDM). It provides the following: radio signals to a number of receivers, as in an apart- • Four “A” channels at 1.5 Mbps. Each “A” chan- ment house or hotel. nel may carry a “VCR”-quality video signal, or distribution control Linearity control. two channels may be merged to carry a “sports”- distribution system A communication system con- quality real-time video signal. In the future, all 4 sisting of coax but occasionally of line-of-sight mi- channels operating together will be able to trans- crowave links that carries signals from the headend port an Extended Definition TV signal with sig- to end-users. nificantly improved quality over anything available distribution systems See System terminology. today. (“A” channels are asymmetric, carrying in- distribution quality The level of quality of a televi- formation only from the telephone company to sion signal from the station to its viewers. For digital the subscriber’s residence. All other channels television this is approximately 19.39 Mbps. within ADSL are symmetric or bi-directional.) distribution-quality television TV conforming to the • One ISDN “H zero” channel at 384 Kbps (kilobits NTSC standard, the SECAM standard, the PAL stan- per second). This channel is compatible with dard, or the PAL-M standard. Syn.: (in CCITT usage) Nortel’s multirate ISDN Dialable Wideband Ser- existing-quality TV. See also Enhanced-quality tele- vice or equivalent services. This channel could also vision, High-definition television. be used for fast, efficient access to corporate LANs disturbance 1. An undesired interference or noise sig- for work-at-home applications, using Nortel’s nal affecting radio, TV, or facsimile reception. 2. An DataSPAN or other frame-relay services. undesired command signal in a control system. • One ISDN Basic Rate channel, containing two “B” dithering 1. The process of spreading the energy of a channels (64 Kbps) and one “D” channel (16 signal. The 6-MHz satellite signal is shifted up and Kbps). Basic Rate access allows the home user to down the 36-MHz satellite transponder spectrum access the wide range of emerging ISDN services to distribute the energy of the video signal. The pur- without requiring a dedicated copper pair or the pose is to reduce the interference that any terres- expense of a dedicated NT1 unit at the home. It trial microwave transmitter could cause to the also permits the extension of Nortel’s VISIT per- satellite transmission. 2. A method for making digi- sonal video conferencing to the home at frac- tized images appear smoother using alternating tional-T1 rates (Px64). colors in a pattern to produce a new, perceived color. • One signaling/control channel, operating at 16 For example, displaying an alternating pattern of Kbps giving the home user VCR-type controls over black and white pixels produces gray. Also, a tech- movies and other services provided on the “A” nique of adding random noise to pixel values be- channel including fast-forward, reverse, search, fore quantization. and pause. divcon Device for displaying printed messages on a • Embedded operations channels for internal sys- TV screen from information received from its com- tem maintenance, audits, and telephone com- puter-type store, a tape reader, or a keyboard pro- pany administration. vided. Developed in the US by RCA. • Finally, the home user can place or receive tele- divergence The spreading of a cathode-ray stream phone calls over the same copper pair without due to repulsion of like charges (electrons). affecting the digital transmission channels listed diverging meniscus A thicker version of the converg- above. And since ADSL is passively coupled to ing meniscus lens configuration. One side curves the POTS line, the subscriber’s POTS capability is inward and the other side curves outward, but the unimpaired in the event of a system failure. edges of the curves do not meet at the rim as they DNG Digital news gathering. Electronic news gath- do in converging meniscus lens. ering (ENG) using digital equipment and/or trans- dk Dark; Deck. mission. DL Delay Line. DNL Differential nonlinearity. DLP Digital Light Processing. DNR See Dolby Noise Reduction System. DM Delta Modulation. DOC A professional term or abbreviation that refers to DMA Designated Market Area. dropout compensation. Several industrial products, D2-MAC One of two European formats for analog such as the time base corrector, provide this feature HDTV. in addition to their major functions.

91 dock dock Loading slot in VCRs. mizing background noise. DNR provides an inexpen- dockable video camera A professional/industrial video sive method of adding quality stereo to videotape camera designed to connect to a specially designed in both professional machines and home VCRs. unit so that the camera can be operated in several Variations of the system include Dolby A, B and C. formats. Cameras so equipped usually have a multi- Dolby B provides an increase in noise reduction to standard switchable encoder that offers special out- 10 dB above 7,000 Hz, while Dolby C is said to offer lets for Beta, S-VHS and other formats. an increase of 20 dB over a wider range than B. docudrama A combination of documentary and A circuitry to recreate the sound of a drama, such as Roots and other TV shows that are theater in home A/V systems. Dolby semifictionalized versions of history. Pro Logic decodes movies, TV shows and musical docu-fantasy A TV presentation that uses factual ele- recordings that have been encoded with Dolby Sur- ments as the basis of a far-fetched dramatic recon- round, directing sound to the proper, realistic loca- struction or projection of events. The overt tion in a 5-speaker system while creating expanded encroachment of speculation and dramatization into listening area. Unlike the old 3-channel Dolby Sur- documentary programs, and of documentary tech- round Systems that used a phantom center channel niques into drama, began with the docudrama, but derived from the left and right speakers, Dolby Pro with the advent of the docu-fantasy seems to leave Logic is a 4-channel system: left, right, center and the tiresome world of facts behind altogether. rear. Center-channel information is derived from the document camera A specialized camera on a long left and right channels and fed to a separate amp neck that is used for taking pictures of still images— for separation and accurate positioning. Dialogue is pictures, graphics, pages of text and objects which anchored to the center-channel speaker, which can then be sent stand alone or as part of a video should be positioned directly above or below the conference. TV. The rear-channel information is derived by ex- Dolby, Ray Engineer; co-developer (with Charles tracting the differences between the front channels Ginsburg) of the first video recorder, demonstrated and then delaying and processing them using a in 1956; inventor of the famous Dolby Noise Reduc- modified, Dolby B-type noise reduction. tion System used in almost all quality audio record- Dolby Surround (Dolby Stereo and Dolby 4:2:4) ers and many VTR and VCR machines. Matrix Analog coding of four audio channels—Left, Dolby Digital An audio compression technique de- Center, Right, Surround (LCRS)—into two channels veloped by Dolby. It is a multi-channel surround referred to as Right-total and Left-total (Rt, Lt). On sound format used in DVD and HDTV. First used in playback, a Dolby Surround Pro Logic decoder con- movie theaters in 1992, it is the result of verts the two channels to LCRS and, optionally, a spent by developing signal-pro- subwoofer channel. The Pro Logic circuits are used cessing systems that exploit the characteristics of to steer the audio and increase channel separation. human hearing. (Formerly Dolby AC-3.) The Dolby Surround system, originally developed for An audio coding system designed specifically the cinema, is a method of getting more audio chan- for use with video, available from Dolby Laborato- nels but suffers from poor channel separation, a ries. The audio framing is matched to the video fram- mono limited bandwidth surround channel and ing, which allows synchronous and seamless other limitations. A Dolby Surround track can be switching or editing of audio and video without the carried by analog audio or linear PCM, Dolby Digital introduction of gaps or A/V sync slips. All of the com- and MPEG compression systems. mon video frame rates, including 30/29.97, 25, and dolly 1. Wheeled mounting device for TV cameras. It 24/23.976, can be supported with matched Dolby allows the camera to be tracked forward and back E audio frame sizes. The Dolby E coding technology by an operator other than the cameraman, while is intended to provide approximately 4:1 reduction the cameraman controls the height of himself and in bit rate. The reduction ratio is intentionally lim- the camera. The cameraman can also pan and tilt ited so that the quality of the audio may be kept the camera in the usual way. 2. Wheels on the feet very high even after a number of encode-decode of a tripod. 3. The action of moving a camera to- generations. The fact that operations such as edit- ward or away from a scene, as to dolly in or dolly ing and switching can be performed seamlessly in out. the coded domain allows many coding generations dollying See Tracking. to be avoided, further increasing quality. dolly shot See Tracking. Dolby Noise Reduction System (DNR) A technique domain In magnetic substances, such as tapes, a re- invented by Ray Dolby designed to increase hi-fi sig- gion of molecules that is the smallest known per- nals during recording and condense them in repro- manent magnet. On an unmagnetized tape, these duction. This results in weak segments of the signal domains are oriented in a random fashion over the being boosted during recording and decreased to entire surface of the tape. The result of this random normal when they are played back, thereby mini- magnetization is that N and S magnetic poles effec-

92 double-sideband transmission

tively cancel one another. When a signal is recorded in sequence so rapidly that each signal persists for onto tape, the magnetization from the recording only the duration of scanning one picture element. head orients the individual domains into specific di- Thus neighboring elements are reproduced in dif- rections, so their combined magnetism produces an ferent primary colors but the elements are so small average magnetic flux force at the surface of the and so closely spaced that at normal viewing dis- tape. The video recording process takes place in a tances the eye cannot resolve them and sees the bandwidth of much higher frequency than does the color formed by the addition of the primary compo- audio recording process. Therefore, the basic tape nents. formulation for video recording must be highly re- double amplitude Syn.: peak-to-peak amplitude. fined, in order to increase the domain particle den- double azimuth A Sony innovation in the videohead sity and to reduce the dropouts. drum that practically eradicates interference (i.e., domestic satellite See Satellite focus. “noise”) during still frame, slow motion, and pic- DOMSAT DOMestic communication SATellite. ture search modes. Donald Duck effect An unintelligible sound track double-azimuth 4-head system. See Azimuth. caused by speeding up videotape playback without double-beam CRT See Cathode-ray tube. modifying the audio pitch. Some VCRs have double- double buffering As the name implies, you need two or triple-speed play, in which the unmuted audio buffers—for video, this means two frame buffers. track emerges sounding like the Walt Disney char- While one of the buffers is being displayed, the other acter. Some machines, on the other hand, disen- buffer is operated on by a filter, for example. When gage the sound track in this mode, while others use the filter is finished, the buffer that was just oper- special digital processing which makes the sound ated on is displayed while the first buffer is now track intelligible. operated on. This goes back and forth, back and dope sheet Caption sheet. forth. Since the buffer that contains the correct im- doppler shift A general phenomenon, of importance age (already operated on) is always displayed, the in satellite communications. Denotes an apparent viewer does not see the operation being performed change of frequency of a wave train caused by rela- and sees a perfect image all the time. tive motion between the wave source and an ob- double chain In TV, the simultaneous running of two server. If a source emitting waves approaches the projectors, each with different film or tape, in order observer, the waves are crowded together and their to intercut from one to the other, such as for cut- frequency thereby increased. Similarly, if the source away or reaction shots in an interview. recedes, the waves are stretched out and their fre- double-eye system A 3D-image system based on a quency is decreased. An example of the doppler shift single observer. See multi-eye system. is in the change of note of a train whistle as the double image A TV picture consisting of two overlap- locomotive approaches and passes an observer. ping images, due to reception of the signal over two dot Picture element. paths that differ in length so signals arrive at slightly dot crawl See Cross-luminance. different times. The longer path generally involves dot generator A signal generator that produces a dot reflection of the signal by a hill, building, or large pattern on the screen of a 3-gun color TV picture metal structure. The later-arriving reflected signal is tube, for use in convergence adjustments. When often called a ghost because it is usually weaker than convergence is out of adjustment, the dots occur in the direct signal and produces a phantomlike image groups of three, one for each of the receiver pri- to the right of the regular image. mary colors. When convergence is correct, the three double mirror A digital video effect where the dis- dots of each group converge to form a single white played picture appears as though split by an imagi- dot. nary line, one side having the original image and on dot matrix tube See Color picture tube. the other side of the split is a complementary mirror dot pattern Tiny dots of light made by the signal of a image. Syn.: symmetry. dot generator and appearing on the screen of a color double sided page turn See Page turn. picture tube. The three color-dot patterns (R,G,B) double-side videodisc player A relatively high-priced merge into one white-dot pattern once the beam unit that permits both sides of a CLV or CAV 12" convergence is attained. videodisc to play continuously without the viewer’s dot pitch The distance between screen pixels mea- having to change or turn over the disc. These play- sured in millimeters. The shorter the distance, the ers usually provide a quick transition from one side better the resolution. It is a measure of the clarity of to the other with little interruption. a RGB color monitor. Dot pitch is the major determi- double-sideband transmission The transmission of nant in the clarity of an image on screen. a modulated carrier wave accompanied by both of dot-sequential color television A system in which the sidebands resulting from modulation. The up- signals from the primary color sources (for instance, per sideband corresponds to the sum of the carrier the three tubes of a color camera) are transmitted and modulation frequencies, whereas the lower side-

93 double-sided mosaic

band corresponds to the difference between the is one of the machine’s strongest selling points. Home carrier and modulation frequencies. Low-power UHF View Network, the now-defunct brainchild of ABC, TV stations with less than 1 kW radiated power are introduced broadcast downloading—for a monthly allowed to use double-sideband transmission, ex- fee—as an alternate pay TV service. Today, the term cept that the lower subcarrier sideband must be at- downloading is more often used with computers, tenuated by at least 42 dB. particularly with users who have modems and can double-sided mosaic An array of photosensitive ele- download data from other sources. See Time shift. ments insulated one from the other and mounted downstream In interactive or 2-way TV, the program- in a TV camera tube in such a way that an image ming to the subscribers. can be projected optically on one side of the mo- downstream channel The frequency multiplexed saic. The corresponding electric signal is obtained band in a CATV channel that distributes signals from by electronically scanning the other side of the the headend to the users. mosaic. downstream keyer A special-effects generator that double speed play A technique that permits viewing enables the technical director (TD) to insert or key a program at two times the normal speed and lis- over composite video signal just before the video tening to an intelligible sound track without the signal leaves the switcher to go over the air. Donald Duck effect which usually accompanies au- downward modulation (US) Negative modulation. dio tracks that are speeded up. This feature was first downwards conversion Standards conversion to a used on a VCR manufactured by JVC. lower (for example, 625 to 405) line standard. down-converted color The color information in a DP Differential phase. Change of the chrominance VCR is converted down to about 600 kHz, placing it phase as function of luminance level. In a color video below the luminance frequency (thus the term “color channel, the phase shift of a small chrominance sub- under”). This signal is still amplitude- and phase- carrier signal at a given luminance signal level, rela- modulated for color saturation and tint. The down- tive to the phase shift at blanking level. Can cause converted color signal is recorded directly onto the changes of hue with changes of level. using the same heads that record the DPCM Differential pulse code modulation. FM luminance signal. As with the FM luminance, DQPSK Differential quadrature phase shift keying, a the color signal is converted back to the standard digital modulation technique commonly used with video signal during playback. As the tape moves cellular systems.

through a VCR, variations in tape speed occur that D’R Transmitted red color difference signal (SECAM);

cause severe problems for the critically phased color D’R = -1.9(R-Y). signal. During the playback process of converting DRAM Dynamic RAM (Random Access Memory). High the 600 kHz signal back to 3.58 MHz, these errors density, cost-effective memory chips (integrated cir- are easily corrected. cuits) used extensively in computers and generally down-converter A circuit that lowers the high-fre- in digital circuit design, but also for building quency signal to a lower, intermediate range. It is framestores and animation stores. Being solid state, used in conjunction with single pay TV systems that there are no moving parts and they offer the dens- send their signals via multipoint distribution service est available method for accessing or storing data. (MDS) microwave. The down-converter lowers the Each bit is stored on a single transistor, and the chip frequency of the signal so that it can be received by must be powered and clocked to retain data. the TV set. In satellite TV, there are three distinct drama-com Syn.: dramedy. types of downconversion used in satellite receivers: dramedy A TV comedy-drama. single downconversion; dual downconversion; and drape To cover, hang, or decorate; cloth hanging, per- block downconversion. haps in folds, as in drapery or drapes, often used as downlink The radio or optical transmission path down- a backdrop on a TV set. ward from a communication satellite to the earth. Dr/Db switch Sync pulse with period of two lines, the The upward path is the uplink. rising edge of which marks the start of a line with downlink antenna 1. The antenna on-board satellite positive polarity of V component in PAL chrominance which relays signals back to earth. 2. The spherical signal or the start of a Dr line in Dr/Db sequence in dish, which receives the return signal from a satel- SECAM chrominance signal. Syn.: 2H; 7.8 kHz; PAL lite. The original signal is sent from an earth station switch; PAL switching signal; SECAM switch. called the uplink to the satellite 22,300 miles above drive control Horizontal drive control. the equator, where the signal is then transmitted to drive pulses Signals from the sync generator that con- various (downlink) receiving stations. The downlink trol the scanning of the electron beams. TV signal usually ranges from 3.7 to 4.2 GHz. driver A software entity that provides a software in- downloading Recording an off-the-air program for terface to a specific piece of hardware. For example, viewing at a more convenient time. Downloading, the DVI video driver provides software access to the or using the time-shift capacity of the VCR or PVR, video board hardware.

94 DTV drive unit The unit that drives the large output stages DS- A hierarchy of digital signal speeds used to classify in a high-powered TV transmitter, normally of 5 kW capacities of lines and trunks. The fundamental upwards and operating in the VHF and UHF bands speed level is DS-0 (64-kilobits/s) and the highest is of 40 MHz to 850 MHz. DS-4 (about 274 million bits per second. Here are DRM See Digital rights management. definitions: DS-1, DS-1C, DS-2, DS-3, DS-4. They drop 1. A wire or cable from a pole or cable terminal correspond to 1.544, 3.152, 6.312, 44.736, and to a building; the hookup between a CATV system 274.176 Mbps. DS-1 also called T-1. and the subscriber’s set. 2. Syn. insert. Sound effect DS-0 Digital Service, level 0. It is 64,000 bps, the world- inserted on an audio- or videotape after the initial wide standard speed for digitizing one voice con- recording. versation using pulse code modulation (PCM). drop field scrambling This method is identical to the DS-1 Digital Service, level 1. It is 1.544 Mbps in North sync suppression technique, except there is no sup- America, 2.048 Mbps elsewhere. The 1.544 stan- pression of the horizontal blanking intervals. Sync dard is an old Bell System standard. The 2.048 stan- pulse suppression only takes place during the verti- dard is a CCITT standard. cal blanking interval. The descrambling pulses still DS-1c Digital Service, level 1C. It is 3.152 Mbps in North go out for the horizontal blanking intervals (to fool America and is carried on T-1. unauthorized descrambling devices). If a DSC See Digital Spectrum Compatible. descrambling device is triggering on descrambling DS-2 Digital Service, level 2. It is 6.312 Mbps in North pulses only, and does not know that the America and is carried on T-2. is using the drop field scrambling technique, it will DS-3 Digital Service, level 3. Equivalent of 28 T-1 chan- try to reinsert the horizontal intervals (which were nels, and operating at 44.736 Mbps. Used for deliv- never suppressed). This is known as double reinser- ery of broadcast TV signals. Also called T-3. tion, which causes compression of the active video DS-4 Digital Service, level 4. 274,176,000 bits per signal. An unauthorized descrambling device cre- second. ates a washed-out picture and loss of neutral sync DSL Digital subscriber line. The ability to use a stan- during drop field scrambling. dard telephone line to transport data. xDSL is the drop frame SMPTE time code format to reconcile the generic term for each of two varieties: ADSL (asyn- difference between the for black and chronous), where the upstream and downstream white TV (30 fr/s) and color TV (29.97 fr/s). data rates are different, and SDSL (synchronous), drop-in A TV channel that can be added to existing where the upstream and downstream data rates are allocations without causing interference to stations the same. located elsewhere but on the same channel. DSM-CC Digital Storage Media Command Control. See dropout Loss of a portion of the video picture signal Multi- and Hyper-media Coding Experts Group. caused by lack of iron oxide on that portion of the DSP Digital signal processor. A specialized computer video tape or by dirt or grease covering that portion chip designed to perform speedy and complex op- of the tape. erations on digitized waveforms. Useful in process- dropout compensator Circuitry that senses signal loss ing sound and video. produced by dropout and substitutes for missing DSS Digital Satellite System. No longer used. information the signal from the preceding line—if DTCP Digital Transmission Content Protection. Tech- one line drops out of a picture, it is filled in with the nology to safeguard copy-protected material trans- preceding line, resulting in no visible dropout on the mitted via IEEE 1394 digital interface connections. screen. Dropout compensators are built into VTRs DTCP was developed by Matsushita along with other and time base correctors. consumer electronics manufacturers. dropout count The number of dropouts detected in a DTIC Digital Transmission of Increased Capacity. given length of magnetic tape. DTO Discrete time oscillator. A digital version of the dropout measurement Refers to the length of time voltage-controlled oscillator. the signal does not appear on the TV screen and the DTS® DTS stands for Digital Theater Systems. It is a loss of signal strength caused by the dropout. The multi-channel surround sound format, similar to time-length of dropouts, measured in microseconds, Dolby Digital. For that use DTS audio, the DVD varies. The dropout may last for as short a time as a - Video specification requires that PCM or Dolby fraction of one line scan or continue for the length Digital audio still be present. In this situation, only of a few lines. If this dropout time is relatively short, two channels of Dolby Digital audio may be present built-in dropout compensator circuitry in later-model (due to bandwidth limitations). VCRs corrects the problem automatically; otherwise, DTT Digital . A term used in Eu- streaks appear across the screen. Signal strength loss rope to describe the broadcast of digital television resulting from dropouts is measured in dB. services using terrestrial frequencies. dry block In film, TV, a rehearsal without cameras. DTV Short for digital television, including SDTV, EDTV, dry edit See Paper edit. and HDTV.

95 DTV Team

DTV Team, The Originally Compaq, Microsoft and In- dual digital/analog converter A videodisc player fea- tel, later joined by Lucent Technologies. The DTV ture designed to improve the stereo output. These Team promotes the computer industry’s views on converters usually come in pairs for left and right digital television—namely, that DTV should not have channels and permit concurrent decoding, result- interlaced scanning formats but progressive scan- ing in enhanced stereo that simulates a live concert ning formats only. (Intel, however, now supports all hall. the ATSC formats, including those that are interlaced, dual electromagnetic focus A feature used with some such as 1080i.) projection-TV systems to produce a very small beam dual-band feedhorn In satellite TV, a feedhorn which for better horizontal resolution. In conventional TV, can simultaneously receive two different bands, typi- electromagnetic focusing is accomplished by a single cally the C and Ku-band. coil attached to the neck of the CRT. As direct cur- dual-band LNB A type of low noise block rent passes through the coil, magnetic field lines are downconverter (LNB) that incorporates two switch- produced parallel to the axis of the tube. able local oscillators to receive two distinct bands. dual feedhorn A waveguide feed system designed With a single-band LNB, receiving both Europeans for both vertically and horizontally polarized signals. DBS (11.7 - 12.5 GHz) and ECS (10.95 - 11.7 GHz) dual field auto exposure system The ability of the broadcasts, for example, would require one or two CCD image sensor of a camcorder to simultaneously parabolic antennas, two feedhorns and two single- measure the light levels of an entire image and the band LNBs. With a dual-band LNB, on the other central zone, calculate these and adjust the expo- hand, a single system (one parabolic antenna, one sure with emphasis upon the central zone. Some feedhorn, and one dual-band LNB) is sufficient to cameras allot about 35% of the image to the cen- receive broadcasts from both satellite broadcasting tral area. systems by simply switching the local oscillators. The dual image effect A video camera feature that per- dual-band LNB thus offers great savings in space and mits the user to mix a still image with live images expense. recorded by the camera. Several types of effects are dual camera recording system A video camera fea- possible with this feature, such as creating a split- ture that permits the integration of two different screen with a still frame on one side of the screen; pictures from two cameras. First introduced by inserting a still image in the center of an action scene; Panasonic in 1989, the dual camera recording sys- or putting an active image in the middle of a full- tem allows the user to record one video image with screen still picture. These effects can be accomplished one camera and superimpose another picture with only with a digital-type camera. a second camera mounted on top and connected dual-in-line package (DIP) A flat rectangular, leaded with a multipin attachment. Video from the mounted package for circuit board mounting of ICs, relays, camera can be blended into the main image as an resistor networks, and other miniature components. inset, as a dissolve or as a superimposed picture. dual-loading system A method of loading tape, dual-channel sound A technique used in TV receiv- employed by some VCRs, that combines the stan- ers to separate the sound and video signals after dard full-loading procedure with half-loading. the common first detector stage. Separate IF stages Dual-loading is designed to speed up the FF and are employed for each signal. REW modes. The high-speed tape transport also dual-channel system An approach to HDTV system results in accelerated searches in all three play- design. See HDTV. back modes. dual deck VCR A VCR with two slots designed for dual orthomode coupler A dish-mounted device that editing or duplicating tapes. Companies experiment- allows reception of both vertically and horizontally ing with these units boast that tapes copied on these polarized signals. machines cannot be distinguished from the origi- dual-side play See Double-side videodisc player. nal. Dual deck VCRs offer several advantages. They dual standard receiver Receiver capable of receiving can record one program while playing a second cas- TV pictures on more than one line standard, e.g., sette, record two different programs simultaneously 405/625 lines in Britain. and edit from one tape to another. As expected, dubbed soundtrack See Dubbing. manufacturers who have announced production of dubbing 1. The combining of two sound signals into dual deck VCRs have come under heavy fire from a composite recording. At least one source of sound several sources, including the Motion Picture Asso- will have been prerecorded. 2. Duplicating an audio ciation of America. The unit, critics charge, promotes and/or video signal, such as composite master tape, piracy of copyright material and could cost the soft- to make additional tape copies. Dubbing puts the ware industry a loss of millions of dollars. Although resulting copy or dub one generation away from the several Japanese firms have dismissed the dual deck tape from which it was recorded. Dubbing can be VCR as an unprofitable product, several American accomplished from one videotape format to an- companies have demonstrated such units. other—e.g., from a larger format to a smaller one

96 DVD

(2" to 1") or from smaller to larger (3/4" to 1"). DVC Digital Video Cassette. DVC format. In the 1990s, Those processes are called bumping up or bumping 55 member companies formed the DVC consortium down. 3. Can also refer to erasing an audio track to finalize the interface format for connection to and recording a new track in its place. Lip synchro- PCs. The interface is based on the IEEE-1394 format nization is often used in TV and film production to proposed by Apple Computer. The DVC format is replace one person’s voice with another’s. The new an industry standard for videotape recording agreed version is said to have a dubbed soundtrack. See upon by all 55 member companies. The digital also Audio dub. 4. Refers to re-recording a new sec- camcorder is the core equipment in the multimedia tion of video over existing footage without affect- era. DVC was ultimately shortened to DV. ing the audio track. Some camcorders provide a DVCAM Sony’s proprietary professional DV format in- flying erase head, a few of which are designed to troduced in 1996, directly competing with DVCPRO. produce this video dubbing feature. Dubbing also See DV, DVC, DVCPRO. refers to copying a tape. DVCPRO A proprietary digital videotape format de- dub in/dub out connectors Used by Sony on its pro- veloped by Panasonic Broadcast. It is based on the fessional VCRs to provide high-quality duplicated consumer DV format and uses much of its hard- tapes. Other manufacturers also use special connec- ware and electronics. Using 1/4-inch tape, the cas- tors for this purpose. The technique should not be settes are the same size as the larger cassettes of confused with the audio/video inputs/outputs used the DV format. The recording system uses efficient with home VCRs for copying. error correction to reduce the need for mechanical DuMont, Allen B. Inventor who in 1939 marketed accuracy but, otherwise, it is a conventional heli- the first all-electronic TV receivers. cal-scan system with a control track. The video sig- duobinary signal A pseudobinary-coded signal in nals are compressed using DCT algorithms and which a “0” (zero) bit is represented by a zero-level chip-sets developed for the DV format. The signal electric current or voltage, a “1” (one) bit is repre- coding is 4:1:1. Each frame is coded individually sented by a positive-level current or voltage if the (intraframe-only) at a video data-rate of about 20 quantity of “0” bits since the last “1” bit is odd. Mbits/s. Two studio-quality (48 kHz, 16 bit) PCM Duobinary signals require less bandwidth than NRZ. audio channels are provided. The format has a lon- Duobinary signaling also permits addition of error- gitudinal control track and a longitudinal audio cue checking bits. track. duplexer A device that combines audio and video sig- DVCPRO50 This variant of DV uses a video data rate nals, or separates signals on a single-transmission of 50 Mbps—double that of other DV systems— path. and is aimed at the higher quality end of the mar- duplicating of tapes See Copying. ket. Sampling is 4:2:2 to give enhanced chroma DV Digital consumer video cassette format, formerly resolution, useful in post production processes (such DVC. as chromakeying). Four 16-bit audio tracks are pro- DVB Digital video broadcasting. The group, with over vided. The format is similar to Digital-S (D-9). 200 members in 25 countries, that developed the DVCPRO HD This variant of DV uses a video data rate preferred scheme for digital broadcasting in Europe. of 100 Mbps, four times that of other DV systems, The DVB Group has put together a satellite system— and is aimed at the high-definition EFP end of the DVB-S—that can be used with any transponder, cur- market. Eight audio channels are supported. The rent or planned, a matching cable system called format is similar to D-9 HD. DVB-C, and a digital terrestrial system called DVB-T. DVCPRO P This variant of DV uses a video data rate of See DVB-T. 50 Mbps, double that of other DV systems, to pro- DVB-T A transmission scheme for terrestrial digital tele- duce a 480 progressive picture. Sampling is 4:2:0. vision. Its specification was approved by ETSI in Feb- DVD Digital Video Disc or Digital Versatile Disc. A faster ruary 1997 and DVB-T services began in 1998. As CD that can hold cinema-like video, better-than-CD with the other DVB standards, MPEG-2 picture cod- audio, and computer data. DVD has received wide- ing forms the basis of DVB-T. Sound may be either spread support from major electronics companies, MPEG or Dolby Digital. It uses a transmission scheme computer companies, and movie/music studios, and based on Coded Orthogonal Frequency Division Mul- has rapidly become a popular home video device. tiplexing (COFDM), which spreads the signals over a The main features include: large number of carriers to enable it to operate ef- • Over 2 hours of high-quality digital video fectively in very strong multipath environments. The • up to 8 tracks of digital audio, each with as many multipath immunity of this approach means that as 8 channels DVB-T can operate an overlapping network of trans- • up to 32 subtitle/karaoke tracks mitting stations with a single frequency. In the areas • automatic seamless branching of video of overlap, the weaker of the two received signals is • menus and simple interactive features rejected. See COFDM, DVB. • instant rewind and fast forward

97 DVD-Audio

• instant search to title, chapter, music track, and DVI technology An all-digital audio, video, and com- timecode puter system. Owned by Intel Corporation. See Digi- • digital audio output (PCM stereo and Dolby Digital) tal Video Interactive. • compatible with audio CDs DVNR Digital Video Noise Reduction. • low cost. DVR See Digital video recorder. The capacities currently available are: DVTR Digital videotape recorder. • DVD-5: 4.7 GB (1 side, 1 layer) DVTS Pronounced “Divitz.” Stands for Desktop Video • DVD-9: 8.5 GB (1 side, 2 layers) conferencing Telecommunications System. • DVD-10: 9.4 GB (2 sides, 1 layer each) dynamic convergence The process whereby the lo- • DVD-18: 17.0 GB (2 sides, 2 layers) cus of the point of convergence of electron beams • DVD-R: 4.7 GB (1 side, 1 layer) (write once) in a color TV tube is made to fall on a specified sur- • DVD-RAM: 2.6 GB (per side, 1 layer) (rewritable) face during scanning. Without dynamic convergence and 4.7 GB (per side, 1 layer) (rewritable) that varies with beam angle, the locus would be a In 2002, DVD players are available in the U.S. for spherical surface at a constant radius from the cen- under $100. ter of deflection of the beam. DVD-Audio DVDs that contain linear PCM audio data dynamic demonstrator A large schematic circuit dia- in any combination of 44.1, 48.0, 88.2, 96.0, 176.4, gram that has been cemented to a board, with all or 192 kHz sample rates, 16, 20, or 24 bits per components mounted near or on their symbols and sample, and 1 to 6 channels, subject to a maximum connected together to give a working circuit of a bit rate of 9.6 Mbps. With a 176.4 or 192 kHz sample radio, TV receiver, or other electronic apparatus. rate, only two channels are allowed. Used for training purposes in classrooms and Meridian Lossless Packing (MLP) is a lossless com- laboratories. pression method that has an approximate 2:1 com- Dynamic Drum System (DDS) JVC’s VHS technology pression ratio. The use of MLP is optional, but the that makes possible virtually noiseless special effects, decoding capability is mandatory on all DVD-Audio longer playing tapes, and “endless recordings” (due players. to its ability to play in both directions, reversing the Dolby Digital compressed audio is required for tape at the end). DDS can also accomplish smooth any video portion of a DVD-Audio disc. slow-motion (without the frame-by-frame jerkiness) DVD-Interactive DVD-Interactive is under develop- and noiseless FF or reverse, accompanied by intelli- ment (due summer 2002), and is intended to pro- gible sound for high-speed viewing. In addition, it vide additional capability for users to do interactive permits still-frame recording while the recorder is in operation with content on DVDs or at Web sites on the pause mode. the Internet. It will probably be based on one of dynamic focusing The process of varying the focus- three technologies: MPEG-4, Java/HTML, or software ing electrode voltage for a color picture tube auto- from InterActual. matically so the electron-beam spots remain in focus DVD-R DVD-ROM. The base physical format of a DVD as they sweep over the flat surface of the screen. that holds data. Without dynamic focusing, part of the image would DVD-Video Often simply DVD. The application for- be out of focus at all times. mat that defines how video programs, such as mov- dynamic mike A type of very sound-sensitive uni- or ies, are stored and played in a DVD player. omni-directional microphone, which can stand rough DVE See Digital Video Effects system. handling. DVI, DVI-D, DVI-I, DVI-CE Abbreviation for Digital Vi- dynamic picture control Horizontal image de- sual Interface. This is a digital video interface to a lineation. display, designed to replace the analog Y’PbPr or dynamic range The weakest to the strongest signal a R’G’B’ interface. For analog displays, the D/A con- circuit will accept as input or generate as an output. version resides in the display. The EIA-861 standard dynamic resolution Resolution when there is a move- specifies how to include data such as aspect ratio ment in the TV picture, for example when the cam- and format information. The VESA EEDID and DI- era is zooming or panning. Syn.: motion resolution. EXT standards document data structures and mecha- dynamic rounding The intelligent truncation of digi- nisms to communicate data across DVI. tal signals. Some image processing requires that two DVI-D is a digital-only interface. DVI-I handles signals be multiplied, for example in digital mixing, both analog and digital. producing a 16-bit result from two original 8-bit DVI-CE (now known as HDMI) is a proposed numbers. This has to be truncated, or rounded, back modified version of DVI that is targeted for consumer to 8 bits. Simply dropping the lower bits can result equipment. It proposes to use YCbCr instead of RGB in visible contouring artifacts, particularly when han- data, includes audio capability and uses a smaller dling pure computer generated pictures. Dynamic connector. rounding is a mathematical technique for truncat- DVITC See digital vertical interval timecode. ing the word length of pixels, usually to their nor-

98 effect

mal 8 bits. This effectively removes the visible arti- free pictures in slow motion and freeze frame modes facts and is non-cumulative on any number of without the use of additional or oversized heads as passes. Dynamic rounding is a licensable technique, found in some Beta and VHS machines. Digital video available from Quantel, and is used in a growing equipment has overcome the problem in its own number of digital products both from Quantel and unique way. other manufacturers. dynamic tracking head A videotape head that auto- dynamic track following A feature first used on matically aligns itself with the center of the video Grundig V-2000 VCRs which eliminated white noise track on the tape for slow motion or freeze frames. bars during slow motion, freeze frame and visual dynode effect A form of distortion produced by im- scan. On conventional Beta and VHS machines orthicon tubes. In an image orthicon, the beam, video heads in Fast Scan cannot accurately retrace after scanning the target, is amplified in an electron the diagonal tracks laid down during recording; in- multiplier section. The multiplier often consists of stead, the heads cross over to adjacent tracks or sig- five dynode sections and a collector, and the return nals, causing interference of white bars. Grundig beam is directed on the first dynode under the in- solved this problem by having the two video heads fluence of the persuader voltage. Occasionally im- move up or down to avoid inaccurate retracing and perfections in the dynode surface cause a small by keeping them on the full width of the recorded ghostly highlight with a spreading tail to appear on track. Dynamic track following also assures noise- the picture.

99 E

E 1. CATV midband channel, 144-150 MHz. 2. TV unwanted signals caused by echoes from the main standard; France, . Characteristics: 819 lines/ transmitted signal. frame, 50 fields/s, interlace—2:1, 25 fr/s, 20,475 echo equalizer See Ghost. lines/s, aspect ratio 4:3, video band—10 MHz, RF EchoStar Communications Corporation A leader in band—14 MHz, visual polarity—positive, sound the satellite TV industry. The parent company of its modulation—A3, gamma of picture signal—0.6. small dish direct broadcast satellite (DBS) service, Dish 3. Effects. Network, one of the two DBS companies serving early bird See Communications satellite. the U.S. early fringe A time period in TV broadcasting, pre- echo waveform corrector Corrector for linear phase ceding prime time, usually 5 to 8 P.M. on weekdays. and amplitude distortions on a TV signal, resulting earth station A station equipped with transmitting from multi-path signals or echoes. Operates by mix- equipment for the production of uplink signals, and ing with the input signal other samples of the sig- also a complete receiving system for picking up nal, advanced or delayed in time relative to the main downlink signals. Known as a ground station. Some- signal and variable in amplitude and polarity. times used synonymously, but incorrectly, with TVRO. E-Cinema (also D-Cinema) Electronic cinema. Typi- There are more than 5,000 earth stations in the US, cally the process of using video at 1080/ in- most owned by private citizens. See Satellite TV. stead of film for production, post-production and EAV End of active video in component digital systems. presentation. EBICON Electron Bombardment Induced Conductivity. eclipse-protected Refers to a transponder that can A TV camera tube that differs from orthicon and vidi- remain powered during the period of an eclipse. con tubes chiefly in the construction of its target. ECU Extreme close-up. EBU European Broadcasting Union. ED-Beta A professional-quality format for VCRs or EBU code European standard for encoding time onto camcorders that can deliver over 500 lines of reso- magnetic tape for broadcast and production use. It lution through the use of an extended bandwidth. uses an 80-bit time code word, as does the Ameri- Introduced in 1987, ED-Beta (Extended Definition) can standard. The only major difference is that the generates superior resolution and offers digital spe- EBU code operates at a rate of 25 fr/s. Since both cial effects, specially designed video heads for high- black and white and color video signals in EBU run density metal particle tape, flying erase head, at exactly 25 fr/s, there is no necessity for drop frame 8-segment assemble editing, automatic audio and code or for any indication of its absence or pres- video insert editing, linear time and frame counter, ence within bit 10 of the time code word. With EBU jog/shuttle variable speed search and various on- code, a binary one in bit 11 denotes the presence of screen displays. The format records at a very high the PAL 8-field frame sequence. bandwidth (up to 9.3 MHz), compared to 5.6 MHz EC Electronic Cinematography. for many of its conventional counterparts, and re- ECC Error Check and Correct. A block of check data, quires special metal videotape. ED-Beta can record usually appended to a data packet in a communica- and play back regular Beta tapes. tions channel or to a data block on a disk, which edge A boundary in an image. The apparent sharp- allows the receiving or reading system both to de- ness of edges can be increased without increasing tect small errors in the data stream (caused by line resolution. noise or disk defects) and, provided they are not too edge noise Refers to the grain or fuzz that appears long, to correct them. on the edge of objects. Edge noise reduces the ECG Electronic Character Generator. sharply defined look of objects in a screen image. echo Ghost signal. Some VCRs offer a built-in digital time-base correc- echo-1, -2 See Communications satellite. tor to compensate for edge noise. The color version echo cancellation An isolation and filtering of of edge noise is referred to as edging.

100 editing methods edge track recording The placement of the audio edit fader A device used in editing to fade a video track in a linear position on videotape. Edge track, signal to black. It is utilized mostly by professionals or linear, recording differs from diagonal recording. and in conjunction with industrial video recorders. edging Refers to unwanted edge noise in the form of edit-in The point at which, or the process whereby, color that appears around objects of different col- one video signal replaces another during the edit- ors. Similar to edge noise in B&W TV, edging affects ing process. See also Edit points. the otherwise sharply defined color of objects on editing 1. In video, an electronic process of transfer- screen. ring or duplicating selected recorded segments of EDH Error detection and handling, for recognizing in- tape onto another tape. A second VCR is required, accuracies in the serial digital signal. It may be in- one functioning as a “player” and the other as the corporated into serial digital equipment and employ “recorder.” For best results they are connected a simple LED error indicator. through their audio and video inputs and outputs. edit Any point on a videotape where the audio or video The recording machine is also hooked up to a TV information has been added to, replaced, or other- receiver, which acts as a monitor. Industrial machines wise altered from its original form. in either 1/2-inch or 3/4-inch format are best suited edit code Time code; videotape retrieval code added for this purpose. They provide more accuracy in elimi- to the original recording and using a time structure nating unwanted video frames and guarantee glitch- of hours, minutes, seconds and frames to locate a free edits. However, some top-of-the-line Beta and particular frame in the tape. Can be read off the VHS machines can produce very satisfactory editing screen through the use of a window burn-in over results. Some VCRs come equipped with built-in edit the screen. controllers, a computerized system complete with edit control jack A special VCR receptacle that per- memory, that can perform accurate and professional- mits two units to be connected for synchronized looking assemble edits. In addition, edit controllers, operation during editing. and editing consoles, complete with readout pan- edit controller 1. The main device that controls and els, can be added as an external accessory for even synchronizes all video decks in an editing system. 2. more fancy editing. Also called electronic editing. A VCR feature, either built into or added externally See Editing methods. 2. See Strobe. to the machine, designed to operate the controls of editing console An accessory, used in conjunction two VCRs during the editing process. Chiefly made with a video camera and a VCR, that automatically up of miniature computers capable of storing synchronizes and controls both units during the ed- memory, the edit controller allows the user to as- iting and copying processes. These more costly com- sign to it several edits at one time. Once the con- ponents offer several advantages. They provide a troller has stored the information in its memory, it variety of special-effects transitions, including wipes, automatically performs assemble edits. Beta and fades and dissolves, which can be inserted between 8mm units have incorporated the concept of the edited scenes. In addition, these consoles allow dif- edit controller into their systems for several years. ferent titles and fonts to be added, in an array of Sony, which offers the controller as an accessory and colors. Editing is usually accomplished by first pre- calls the unit a remote editing control, allows the viewing tapes, then entering into a keyboard the user to assemble eight video sections before it au- selected editing points. The computerized console, tomatically executes the editing sequence. To be which contains its own memory bank, stores the in- effective, an edit controller or similar device should formation and predetermined sequence in its multi- be able to find and return to edit points. Some units scene memory and then automatically carries out use the VCR counter, others rely on a vertical inter- the transfers with precise edits. Some consoles, also val time code recorded between video fields, and known as editing controllers, operate between cam- still others depend on coded track different from era and VCR by IR beam, while others must be con- the video. A more sophisticated version of the con- nected using the appropriate cables and jacks. Some troller is the editing console. models include a digital effects generator, an audio edit decision list (EDL) A listing of scenes with which processor, a video distribution amp, a color proces- a video editor assembles a video program from indi- sor and enhancer. vidual shots; takes the form of a printed copy, paper editing controller See Editing console. tape, or and is used to automatically as- editing deck A specially constructed VTR which has, semble the program. Also called edit list. in addition to play and record circuitry, circuitry and edited master (EM) In post production for audio or controls for assembly and/or insert editing; an edit- video, the first copy produced by the process of ed- ing deck is used in conjunction with a second VTR iting together the original material. Edited master is to record a master program tape (on the editing deck the final edited videotape with continuous program from various tape-recorded segments being played material and time code from beginning to end. Also back on the second VTR. called edit master, production master. editing methods There are three basic methods of

101 editing terminal

controlling and editing videotape: manual, control educational television (ETV) TV used primarily for track and SMPTE time code. See Types of edit. educational purposes, such as for broadcasting lec- editing terminal In videotex, a terminal designed for tures from a master studio to receivers in satellite use in projecting, preparing, or modifying videotex classrooms or to receivers in homes of those unable pages. It is distinguished by its facilities for encod- to attend schools. ing alphanumeric, color, and graphics information. edutainment The answer to the question “What do Online editing terminals operate directly to the view you get when you cross educational material with database computer. Offline (or local) editing termi- interactive video?” A term coined by “someone who nals permit the preparation, viewing, and modifica- obviously knows nothing about either education or tion of videotex pages (both routing and information) entertainment,” says Laura Buddine, president of on a local basis. multimedia games maker Tiger Media. But it is be- edit list Edit decision list. coming popular in residences and it’s typically played edit master Edited master; production master. on PCs with CD-ROM players. editor An electronic device used by professionals to EDV In (2+3)D-image display systems, data indicative control synchronization of at least two devices for of the display of a digital signal from an external the purpose of switching video and audio material apparatus through interface. to a specific point in a program. The editor permits EE CATV hyperband channel, 324-330 MHz. merging pictures and sound from two VCRs or one e-e Electronics-to-electronics. The picture viewed on video camera and one VCR into one master tape. the TV screen when a recording is being made. This Most of these devices have various controls for dif- picture goes through some but not all of the ferent functions such as Play, Forward, Reverse, Pre- recorder’s circuits and is used to test the operation view, etc. Some less costly models are available for of said circuits. the nonprofessional. EEPROM Electrically Erasable Programmable ROM. A edit-out The point at which, or the process whereby, an special type of EEPROM, referred to as flash memory, inserted video signal stops and the signal it replaced can be rewritten while it is in the device. for a predetermined length of time resumes. The other effect A multisource transition, such as colorizing, end of an edit-in when insert editing is being done. chroma-keying, etc. With currently available editing decks, edit-ins are more effective isotropic radiated power (or equivalent electronically stable than edit-outs (except in the case isotropically radiated power) (EIRP) Combined re- of computer-controlled Quad machines). sult of transmitter (or transponder) RF power, and edit points The beginning (edit-in) and ending (edit- transmitting antenna gain. Refers to the satellite sig- out) points of a selected event within a program nal level strength that reaches earth. EIRP is described being assembled on magnetic tape. in dB per watt (dBW). Satellites transmit relatively edit search In camcorders, a function used to view narrow beams that widen as they approach earth. the recorded picture for a moment during record- The pattern or surface area that they cover is called ing. Using edit search, you can review the last re- the footprint. It is this footprint shape that deter- corded scene or check the recorded picture in the mines the EIRP. viewfinder. (ERP). The power of a edit/start See Automatic transition editing. station’s visual signal. In the US, TV stations are au- edit/start control See Automatic transition editing. thorized by the FCC to operate at a certain power. edit switch In VCRs, a feature designed to switch a In order to avoid interfering with other electronic low-pass filter out of the video output circuitry as a communications, stations are limited in the amount means of cutting back on video noise. However, the of power that can be emitted from their transmit- function presents one major drawback. Since the ters and antennas. A station may have 149 kW vi- process simultaneously lessens , it sual power and 29.5 aural power, but its ERP is also accelerates generation loss during editing. An expressed as 149 kW. edit switch on a video camera is designed to change effects Property, impression. Special effects are optics the video signal that the camera transmits to com- (optical effects) or visual effects to produce illusions, pensate for any degradation that may occur during or sound, for simulation of a specific sound. The the editing or copying process. Relatively few cam- abbreviation is FX or sometimes, as with video eras offer this feature. effects, E. EDL Edit Decision List. effects buttons The push-button controls on a spe- EDTV Enhanced Definition Television, which is a sub- cial effects generator that indicate the special ef- set of the DVB’s and ATSC’s Digital Television (or Digi- fects (inserts, wipes, keying, etc.) available on that tal TV) specifications. The EDTV format is essentially SEG and which are engaged when an effect is 480 or 576 scan lines with progressive scanning, or desired. / (the “p” stands for progressive scanning). effects channel That bus in a 3-bus switcher set aside Also see HDTV, SDTV. to produce special effects.

102 EIA Linearity Chart

effects switcher An electronic switcher that activates consumer digital audio/video sources, including the generation control and coordination of special settop boxes and DVRs or VCRs. effects. EIA-775.1 adds mechanisms to allow a source of EFP Electronic Field Production. MPEG service to utilize the MPEG decoding and dis- EGA Enhanced Graphics Adapter. A video display play capabilities in a DTV. adapter, introduced by IBM in 1984. The video dis- EIA-775.2 adds information on how a digital stor- play standard for IBM-compatible microcomputers age device, such as a D-VHS or hard disk digital re- featuring 640-by-350-pixel resolution. EGA can dis- corder, may be used by the DTV or by another source play no more than 16 colors at once. It was super- device such as a cable set-top box to record or time- seded by VGA. shift digital television signals. This standard supports EHT Extra-High Tension. the use of such storage devices by defining Service EIA Electronics Industries Alliance; Electronic Industries Selection Information (SSI), methods for managing Association. The people who determine audio and discontinuities that occur during recording and play- video standards in the US. back, and rules for management of partial trans- EIA-516 United States teletext standard, also called port streams. NABTS. EIA-849 specifies profiles for various applications EIA-608 United States closed captioning and extended of the EIA-775 standard, including digital streams data services (XDS) standard. Revision B adds Copy compliant with ATSC terrestrial broadcast, direct- Generation Management System - Analog (CGMS-A), broadcast satellite (DBS), OpenCable™, and stan- content advisory (v-chip), Internet Uniform Resource dard definition Digital Video (DV) camcorders. Locators (URLs) using Text-2 (T-2) service, 16-bit EIA-805 This standard specifies how VBI data are car- Transmission Signal Identifier, and transmission of ried on component video interfaces, as described in DTV PSIP data. EIA-770.1 (for 480p signals only), EIA-770.2 (for 480p EIA/IS-702 NTSC Copy Generation Management Sys- signals only) and EIA-770.3. This standard does not tem - Analog (CGMS-A). This standard added copy apply to signals which originate in , as defined in protection capabilities to NTSC video by extending EIA-770.1 and EIA-770.2. The first VBI service defined the EIA-608 standard to control the Macrovision anti- is Copy Generation Management System (CGMS) in- copy process. It is now included in the latest EIA- formation, including signal format and data structure 608 standard, and has been withdrawn. when carried by the VBI of standard definition pro- EIA-708 United States DTV closed captioning standard. gressive and high definition YPbPr type component EIA CEB-8 also provides guidance on the use and video signals. It is also intended to be usable when processing of EIA-608 data streams embedded the YPbPr signal is converted into other component within the ATSC MPEG-2 video elementary trans- video interfaces including RGB and VGA. port stream, and augments EIA-708. EIA-861 The EIA-861 standard specifies how to in- EIA-744 NTSC “v-chip” operation. This standard added clude data, such as aspect ratio and format infor- content advisory filtering capabilities to NTSC video mation, on DVI. by extending the EIA-608 standard. It is now in- EIAJ Electronic Industry Association of Japan. cluded in the latest EIA-608 standard, and has been EIA-J CPX-1204 This EIA-J recommendation specifies withdrawn. another signaling (WSS) standard for EIA-761 Specifies how to convert QAM to 8-VSB, with NTSC video signals. WSS may be present on 20 and support for OSD (on screen displays). 283. EIA-762 Specifies how to convert QAM to 8-VSB, with EIAJ Type #1 Recommended Color Standard The no support for OSD (on screen displays). color standard established by the EIAJ to be com- EIA-766 United States HDTV content advisory patible with the EIAJ Type #1 Standard; color tapes standard. can be played back in b&w on EIAJ Type #1 b&w EIA-770 This specification consists of three parts (EIA- VTRs, and b&w tapes can be played back in b&w on 770.1, EIA-770.2, and EIA-770.3). EIA-770.1 and EIAJ Type #1 color VTRs. EIA-770.2 define the analog YPbPr video interface EIAJ Type #1 Standard That standard established by for 525-line interlaced and progressive SDTV systems. the EIAJ for 1/2-inch VTRs. EIA-770.3 defines the analog YPbPr video interface EIA Linearity Chart A test chart available from the for interlaced and progressive HDTV systems. EIA- Electronic Industries Association with configurations 805 defines how transfer VBI data over these YPbPr to equal the bar and dot patterns from a sync gen- video interfaces. erator in the average broadcast studio. The func- EIA-775 EIA-775 defines a specification for a base- tion of the chart is to test and measure the scan band digital interface to a DTV using IEEE 1394 and linearity of professional, broadcast-type equipment. provides a level of functionality that is similar to the It is designed to duplicate the normal broadcast con- analog system. It is designed to enable figurations of 14 horizontal and 17 vertical bars. Also interoperability between a DTV and various types of known as a ball chart.

103 EIA sync

EIA sync Also called EIA RS-170 sync. The standard duced by sending an adjustable value of direct cur- waveform for broadcast equipment in the US as es- rent through a focusing coil mounted on the neck tablished by the EIA. of the tube. EIA/TIA STANDARD—ELECTRICAL PERFORMANCE electromagnetic frequency spectrum In TV, the FOR TV TRANSMISSION SYSTEMS, EIA/TIA-250-C A broadcasting frequency which holds the various TV joint publication of the EIA and the TIA. This docu- signals transmitted from broadcast stations. A cer- ment contains a comprehensive listing of the crite- tain part or band of this spectrum is allotted to each ria for evaluating the quality of TV images, together signal. The FCC apportions each slot to a channel, with performance standards for both color and B&W. thereby permitting many signals while avoiding in- E-I-C Engineer-In-Charge, as of a TV production. terference. For instance, a TV channel is given a band A projection system developed in Switzer- 6MHz wide and must carry its video, audio and color land for theater TV and other applications requiring information within these parameters. New forms of a large and bright display. Unlike conventional pro- TV transmission may require a wider slot than the jection systems, in which the total light available is standard 6 MHz. High definition broadcasting, for limited by the output of a CRT, the primary source example, whose signal transmits much more infor- for the Eidophor is an arc light or equally bright mation and therefore requires an area five times source. The image is formed by a Schlieren optical greater than the above standard, will have to utilize system, a complex electrooptical system. either cable systems or the 12-GHz portion of the EIRP Effective Isotropic Radiated Power. spectrum via satellite broadcast. Electra A broadcast teletext operation consisting of a electromagnetic interference (EMI). An electromag- one-way information service. It contains pages of netic disturbance caused by such radiating and trans- digital information from a central computer data mitting sources as electrostatic discharge, lighting, base, emanating from TV station WKRC-TV in Cin- radio and TV signals, and power lines. It can induce cinnati. Electra information is also fed to and trans- unwanted voltages in electronic circuits, damage mitted by WTBS to cable systems, and components, and cause malfunction. Shields, filters, some TV stations pick up and retransmit the infor- and transient suppressors protect electronics from mation from the WTBS signal. The Electra operation EMI. is based on the World Standard Teletext (WST) electromagnetic lens Syn.: magnetic lens. An elec- system. tron lens consisting of an arrangement of coils that Electret condenser A type of very sensitive micro- focuses an electron beam electromagnetically. There phone requiring dc power (usually supplied by a are two basic types; in one type, used with TV cam- battery built into the mike). era tubes, the entire tube is included within a coil electric image An array of electric charges, either carrying DC which produces a magnetic field paral- stationary or moving, in which the density of charge lel to the tube axis. This field has no effect on elec- is proportional at each point to the light values at trons travelling along the tube axis but those moving corresponding points in an optical image to be re- at angles to the axis rotated about the axis and re- produced. turn to it at regular intervals along the axis. Thus, electroluminescense The direct conversion of elec- there are a number of points at which the electron trical energy into light. beam is in focus and by adjustment of the acceler- Electroluminescent TV screen A system of flat screen ating electric field or of the magnetic field one of TV utilizing numerous microscopic elements. Elec- these focus points can be made to coincide with troluminescent TV, or EL, is one of a few systems the target. considered as a replacement for the CRT in produc- The second type of magnetic lens employs a very ing large-screen TV. EL can be compared in effect to short magnetic field which can be produced by a a large array of light bulbs. permanent magnet. The field from such a magnet electromagnet A device comprising a ferromagnetic has pronounced radial components and the inter- core within a winding which displays magnetic prop- action of these with the electron beam causes the erties only when a current flows in the winding. beam to rotate about the tube axis. The axial com- electromagnetic deflection Syn.: magnetic deflec- ponent of the field causes the beam to be deflected tion. Deflection of an electron stream by means of a towards the tube axis so that an image, usually ro- magnetic field. In a TV picture tube, the magnetic tated, can be produced on the target. See electro- fields for horizontal and vertical deflection of the static lens. electron beam are produced by sending sawtooth electron beam A beam of electrons that is usually currents through coils in a deflection yoke that goes emitted from a single source, such as a thermionic around the neck of the picture tube. cathode. In TV camera tubes and picture tubes such electromagnetic focusing Syn.: magnetic focusing. a beam originates in an electron gun and is focused Focusing the electron beam in a TV picture tube by by an electron lens on the target or screen. See also means of a magnetic field parallel to the beam, pro- Electron gun.

104 electronic frequency synthesizing tuner electron beam recording A technique employed in electronic cinematography (EC) The use of video video-to-film processes in which movie film images cameras to produce the picture quality of 35mm film are created by electronic impulses. The electronic cameras. beam replaces the light, which normally exposes electronic classroom A supplemental system of edu- motion picture film. cation using interactive video so that teachers and electron gun Also called gun. A device that produces students can listen to and interact with one another. an electron beam and forms an essential part of Although the video portion is restricted to one-way many instruments, such as CRTs, etc. It consists of a (the students can see the instructor), the electronic series of electrodes usually producing a narrow beam classroom offers several benefits. Federal and state of high-velocity electrons. Electrons are released from governments, universities and public and commer- the indirectly heated thermionic cathode, the inten- cial TV networks can provide a vast array of courses. sity being controlled by variation of the negative Small, budget-tight schools and systems can avail potential of the cylindrical control grid surrounding themselves of sophisticated subject matter and les- the cathode. The control grid has a hole in front to sons while retaining the all-important communica- allow passage of the electron beam. The electrons tion between instructor and students. The system are accelerated by a positively charged accelerating usually involves a satellite dish, electronic keypads anode before being focused by the focusing elec- and cordless telephones. The initial outlay for the trode and then further accelerated by the second basic equipment comes to much less than the an- anode. nual salary for one teacher. Electronicam System of program production using electronic darkroom In still video photography, a facil- combined film and TV cameras, first employed in ity capable of using a laser beam to scan photographs the US in 1955, and later developed in Germany or art work and converting the images into digital under the name Electronic-Cam. signals that are then transmitted to a computer. The electronic blackboard This is a teleconferencing tool. electronic darkroom, usually part of a newspaper, At one end there’s a large “whiteboard.” Write on periodical or other publishing enterprise, permits the this board and electronics behind the board pick up image to be edited for proper color, size and detail. your writing and transmit it over phone lines to a The picture is then sent to another unit that converts remote TV set. The idea is that remote viewers can it into a film image ready for the printed page. Since hear your voice on the phone and see the presenta- images can be manipulated quite easily, profession- tion on the electronic blackboard. The product has als in various fields have found the technique effec- not done well because it is expensive—typically sev- tive in removing distracting materials such as blurred eral hundred dollars a month just for rent, plus ex- objects, poles or overhead wires. But some capabili- tra hundreds for transmission costs. In Japan, there ties, such as inserting one image into another exist- are similar boards called OABoards, for Office Auto- ing one to form a completely different picture, has mation Boards. They do one thing differently: they caused critics to voice concern about the ethics of will print a copy on normal letter-size paper of what’s reconstructing electronic images. Another related written on the board. This takes about 20 seconds. consideration is that no original negative will exist to Some of these Japanese OABoards will also trans- confirm the authenticity of a picture under question. mit their contents over phone lines. electronic editing Repositioning video signal segments electronic camera The combination of video cameras on a reel of videotape without physically cutting the recording simultaneously with film cameras. The tape; a rerecording of the video signal segments in electronic images are delivered to a central control different order. Electronic editing implies that the board for a director’s perusal and editing. Electronic edited version of the program will be one genera- cinema was first used successfully by Francis Ford tion removed from the recordings from which it was Coppola during the production of his 1982 film One assembled. From the Heart. electronic field production (EFP) Refers to profes- electronic channel selection A feature on a VCR sional video equipment which usually features more permitting remote control, faster electronic bypass- sophisticated capabilities and a more rugged hous- ing of channels and multiple channel recording. The ing than equivalent home video units. For example, mechanical rotary-type tuner allowed only one-chan- EFP cameras operate more efficiently in low light nel recording with the timer. Electronic channel se- levels, hold registration better, contain special prism lection combines the benefits of the versatile optics, provide superior electronic stability and offer microprocessor chip with those of the Varactor tuner. more durability. Some companies, which sell home Also called direct channel access. video equipment, have a professional products divi- electronic character generator (ECG) A typewriter- sion, which specializes in EFP components. Other like machine that produces reports, sports scores, companies produce only professional equipment. identifications, and other lettering as part of a TV electronic frequency synthesizing tuner Frequency- picture. synthesis tuner.

105 electronic game electronic game A self-contained version of a video each recording. When the machine is switched to game, with its own microprocessor-controlled screen FF or REW and the index control is turned on, the or other type of display. Miniature, pocket-sized ver- tape stops automatically at each point that a pro- sions that are battery-powered and can display ani- gram was recorded. With the switch off, the tape mated figures and symbols for game playing on a continues to rewind or move forward. On some VCRs liquid-crystal panel. the signal is not automatically encoded on the tape electronic image mail The transmission of slow scan unless so desired. There are other techniques for TV or facsimile via “.” Not a com- locating segments of tape. One system designates mon term. numbers to the portions of tape. In the LV videodisc electronic image stabilization In a camcorder, a func- system, electronic encoding permits the viewer rapid tion that helps eliminate the shakiness inherent in access to marked sections. Each chapter or frame hand-held shooting. on the disc can be recalled. More prerecorded pro- electronic indexing See Electronic program indexing. grams, including sports discs and music-oriented Electronic Industries Association (EIA) A trade as- shows, are using this feature. The indexing feature sociation made up chiefly of electronic component is also known as electronic indexing, picture index- and equipment manufacturers. Its functions include ing, program indexing, etc. standardization of sizes, specifications, and termi- electronic publishing The production of text (and nology for electronic products in the US. Known as illustrations, if used) on media other than paper, in- Radio Manufacturers Association (RMA) 1924-1950, cluding CATV, computer, teletext, videocassette, vid- Radio-Television Manufacturers Association (RTMA) eodisc, and videotex. 1950-1953, and Radio-Electronics-Television Manu- electronic redlining A term for disenfranchising facturers Association (RETMA) 1953-1957. people and institutions because of their lack of tele- Electronic Industries Association of Japan (EIAJ) The communications services and apparatus. Japanese committee that sets electronic standards electronic scanning Scanning a TV image with an for 1/2-inch helical scan video recorders, etc. electron beam in a cathode-ray TV camera tube, as electronic matte The process of combining images distinguished from mechanical scanning. from two cameras. See also Matte. electronic shopping An interactive Videotex system electronic media Radio and TV. that enables a consumer to obtain information and electronic news gathering (ENG) 1. A term used to to purchase and pay for items ordered. describe the process of a TV crew covering news electronic setup (ESU) The prebroadcast time during events at the scene of the event. Production teams which equipment is set up and tested. that shoot at remote locations typically use a electronic still camera An appliance using a memory Betacam, a professional camcorder developed by the card in place of traditional film. By integrating opti- Sony Corporation. (Sony has also licensed several cal and electronic technology with precision mechan- other manufacturers, such as Ampex, to produce ics, images from the memory card can be instantly Betacam equipment.) Betacams use specialized displayed on a TV or a computer monitor, or trans- 1/2-inch tape that permits the integration of a pro- mitted over telephone lines. fessional quality VTR with a professional quality cam- Electronic Still Camera Standardization Commit- era into a single shoulder-mount unit. Most TV tee (ESCSC) An organization composed of more studios that use Betacams dub the material to than 40 manufacturers of still video cameras dedi- 1-inch videotape (a process known as bumping up) cated to promoting the relatively new cameras and in order to take advantage of the superior quality accessories and to setting universal standards for the and editing features available with that level of stu- products. The ESCSC, founded in 1983, focused on dio equipment. Another professional 1/2-inch tape the still disc (VF) as the standard me- format, although not as widely used as Betacam, is dium for the emerging system of electronic still pho- MII. 2. A recording system used in TV in which scenes tography (ESP). outside the TV studio are recorded directly on to electronic still video See Still video camera. videotape rather than onto film. A portable TV cam- electronic switching In video, a process used with era and VTR are used, often in conjunction with a certain accessories such as switchers to avoid prob- mobile transmitter that relays the recording directly lems of noise usually associated with electrical sig- to the main control center. nals and mechanical switching. Electronic switching electronic photography See Kodak still-picture pro- is performed by and ICs built into these ac- cess, Still video camera, Still video printer. cessories. The use of electronics in signal switching (EPG) A schedule of forth- provides another major advantage—no deteriora- coming programs, shown on the TV screen for the tion of parts. viewer. electronic text generation Refers to the electronic electronic program indexing In a VCR, a feature production of characters for TV and broadcast pur- designed to place an electronic signal at the start of poses. The first successful TV character generator

106 embedded audio

appeared during the early years of TV. The charac- cus electron beams. By applying suitable potentials ters were relatively crude, and the technique was to a system of electrodes it is possible to produce an unable to produce proportionally spaced letters and electric field with equipotential surfaces shaped like numbers. During the 1960s CBS Laboratories experi- convex or concave lenses. The behavior of an elec- mented with an electronic character generator that tron beam entering such a system is similar to that turned out Helvetica Medium typeface in 18- and of a light beam entering an optical lens system and 28-line sizes and proportional characters of graphic- this analogy has prompted the adoption of the term arts quality. In 1964 RCA had the capability to pro- electron optics. See Electron lens. duce by way of a twin-channel generator upper-case electron scanning See Scanning. characters in two sizes. With the advent of PCs, char- electro-optical effect See Kerr effects. acter generators combined with software to offer electro-optical shutter Syn.: Kerr cell. scores of print styles by the early 1980s. Today, a electro-optics The study of the interactions between host of manufacturers offer compact, sophisticated, the refractive indices of some transparent dielectrics less expensive character generators with such fea- and the electric fields in which they are placed. tures as italics, drop shadows, anti-aliasing, charac- Changes in the optical properties of dielectrics are ter sizing, graphic symbols, and animated characters. produced. See Kerr effects. electronic tuner A feature which allows the tuning of electrostatic discharge element An element on top TV channels electronically via a keyboard-type panel of the head drum to neutralize the static that can instead of the rotary knobs. By employing a micro- build up in the head as the tape rubs past it. Most processor, the electronic tuner can adjust itself to VCRs made since the early 1980s use this element. receive local channels in numerical order, can be electrostatic focusing A method of focusing an elec- programmed with various instructions and can of- tron beam by the action of an electric field, as in the fer cable-ready TV sets and VCRs. Another advan- TV picture tube. tage of electronic tuning is the remote control electrostatic lens An electron lens consisting of an accessory for changing channels, a feature not pos- arrangement of electrodes that focuses an electron sible with the mechanical knobs. In addition, since beam electrostatically. hundreds of mechanical parts are eliminated, tuner electrostatic An instrument for measur- reliability has vastly improved. ing high direct voltages that relies for its action on electronic viewfinder A TV camera viewfinder that the attraction between the opposite charges on the has a small cathode-ray picture tube to show the plates of a capacitor. One form of the instrument image being televised. resembles a multi-plate , one set electron image 1. An image formed in a stream of of plates being fixed and the other free to move electrons. The electron density in a cross section of against the pull of a spring. The extent of the move- the stream is at each point proportional to the bright- ment is an indication of the magnitude of the ap- ness of the corresponding point in an optical im- plied voltage. The instrument, being capacitive, takes age. 2. A pattern of electric charges on an insulating no current from the source of voltage after the ini- plate, with the magnitude of the charge at each tial charging current and is therefore useful for mea- point being proportional to the brightness of the suring voltages with a very high source resistance, corresponding point in an optical image. such as the EHT supply in TV receivers. electron lens An assembly of electrodes or of perma- elemental area Picture element. nent electromagnets that can be used to focus an elephant doors Large doors to a TV studio or other electron beam at a given point, for example on the place. target of a camera tube or on the screen of a CRT. elevation angle The vertical angle measured from An electron-tube structure that the horizon up to a targeted satellite. produces secondary electron emission from solid elevator Cassette lift mechanism in front-loading reflecting electrodes () to produce current VCRs. amplification. The electron beam containing the Emergency Broadcast System (EBS) A system that is desired signal current is reflected from each dynode composed of AM, FM, and TV broadcast stations; surface in turn. At each reflection, an impinging elec- low-power TV stations; and non-government indus- tron releases two or more secondary electrons, so try entities operating on a voluntary, organized ba- the beam builds up in strength. A typical arrange- sis during emergencies at national, state, or ment of nine dynodes can give an amplification of operational (local) area levels. several million. Used in multiplier phototubes and EM 1. Edited Master. 2. Extremely Mature—see Movie TV camera tubes. It is also called a multiplier or a rating systems. secondary-electron multiplier. embedded audio Digital audio that is multiplexed electron optics The study of the behavior of electron and carried within an SDI connection, thus simplify- beams subjected to electric and magnetic fields, ing cabling and routing. The standard (ANSI/SMPTE particularly the use of such fields to deflect and fo- 272M-1994) allows up to four groups each of four

107 EMI

mono audio channels. Generally VTRs only support chines automatically begin to rewind if in the Record Group 1 but other equipment may use more, for or Play mode. The marker may take several forms, example Quantel’s Clipbox server connection to an including among others a photoreflective strip or a edit seat uses groups 1-3 (12 channels). 48 kHz syn- transparent segment of tape. chronous audio sampling is close to universal in TV energy dispersal In satellite TV, the modulation of an but the standard also includes 44.1 and 32 kHz syn- uplink carrier with a triangular waveform. This tech- chronous and asynchronous sampling. nique disperses the carrier energy over a wider band- EMI Electromagnetic interference. width than otherwise would be the case in order to Emitron A TV camera tube similar to an iconoscope, limit the maximum energy compared to that trans- made in Great Britain and named after the manu- mitted by an unclamped carrier. By spreading the facturers, Electrical and Musical Industries. Also called spectrum, there is less chance of interfering with a super iconoscope. Now obsolete. other users of the same frequencies. This triangular emphasis Also called preemphasis. In FM transmis- waveform is removed by a clamp circuit in a satellite sion, the intentional alteration of the amplitude-ver- receiver. sus-frequency characteristics of the signal to reduce ENG Electronic News Gathering. adverse effects of noise in a communication system. engineering setup (ESU) A TV technique to freeze an The higher frequency signals are emphasized to pro- image on the screen. It is most frequently used, by duce a more equal modulation index for the trans- an ESU operator, to project an image over the shoul- mitted frequency spectrum, and therefore a better der of the anchor, or news broadcaster, during the signal-to-noise ratio for the entire frequency range. lead-in of a news item. In TV, the process of boosting the level of the high- enhance control A function on an image enhancer frequency portions of the video signal. (or mini-enhancer) designed to increase the sharp- emphasizer Preemphasis network. ness of high-frequency information. The control Emshwiller, Ed Video artist who uses digital cameras, adjusts the amount of “boost” applied to the high- minicomputers, video synthesizers, chromakeyers frequency signal. Enhancers are signal processors and and character generators to create new concepts in are used to increase the detail in a video picture. art. Therefore they exaggerate the high frequency in- encipher To scramble or otherwise alter data so that formation in the video signal. Rotating the enhance they are not readily usable unless the changes are control helps to improve sharpness. The control of- first undone. ten has a range capable of increasing 2 MHz from 0 encode In general, to encipher. to about 3 times. For maximum effectiveness, the encoder A device which converts an information into enhance (sharpness) control usually operates in con- a coded form. Colorplexer is an example. Syn.: coder. junction with a response (noise reduction) control. encoder adjustment A necessary function if multiple enhanced definition systems Same as IDTV. camera setups are to operate accurately. Precise enhanced definition television See EDTV. phase matching, or genlock, adjustments or realign- enhanced NTSC systems Types of proposed Advanced ments can be made in the field by experienced tech- Television (ATV) systems that used an approach that nicians with a special portable instrument known as modified the existing TV technical standards in a a vectorscope. modest manner. The enhanced systems sought to im- encryption The transformation of data from its origi- prove (or “enhance”) the current NTSC system with nal intelligible form to an unintelligible cipher form, better picture quality, but the method did not increase as in the scrambling of TV signals. Pay-TV transmis- the number of scanning lines. The systems did, how- sion often is encrypted, and subscribers have de- ever, improve the aspect ratio and worked within the vices that decrypt, or unscramble. Two basic current 6-MHz channel. They were described as NTSC- transformations may be used: permutation and sub- compatible in that the basic signal could be received stitution. Permutation changes the order of the in- on current TV sets, but in order for the picture im- dividual symbols comprising the data. In a provements to be seen, a new TV set was required. substitution transformation, the symbols themselves This approach is sometimes called enhanced defini- are replaced by other symbols. During permutation, tion TV (EDTV). Three variations of such a system were the symbols retain their identities but lose their po- proposed. They are viewed as an evolutionary step sitions. During substitution, the symbols retain their toward HDTV using digital technology. positions but lose their original identities. Combin- enhanced-quality television Syn.: (in CCITT usage) ing the basic transformations of permutation and improved-definition TV. substitution produces a complex transformation enhanced services Services offered over transmission termed a product cipher. facilities which may be provided without filing a tar- end-of-tape marker An indication placed on a video- iff. These services usually involve some computer- tape to specify that the tape is reaching its physical related feature such as formatting data or end. When the marker is reached, most VCR ma- restructuring the information. Most Bell operating

108 error concealment

companies (BOCs) are prohibited from offering en- equalization (EQ) The normalization of an electronic hanced services at present. But the restrictions are signal, either audio or video; adding EQ in audio or disappearing. The FCC defines enhanced services as video means reshaping the frequency response to “services offered over common carrier transmission emphasize certain frequency ranges and eliminate facilities used in interstate communications, which others. employ computer processing applications that act equalization pulses These are two groups of pulses, on the format, content, code, protocol or similar as- one that occurs before the serrated vertical sync pects of the subscriber’s transmitted information; and another group that occurs after. These pulses provide the subscriber additional, different or restruc- happen at twice the normal . tured information.” In other words, an enhanced They exist to ensure correct 2:1 interlacing in early service is a computer processing application that televisions. changes in some way the information transmitted equalizer In audio, a unit designed to selectively in- over the phone lines. Value-added Networks, Trans- crease or decrease portions of the frequency range, action Services, Videotex, Alarm Monitoring and thereby customizing the sound to personal taste or Telemetry, Voice Mail Services and E-Mail are ex- to accommodate the ambience of a specific room. amples of enhanced services. The equalizer, a feature on many audio/video receiv- enhanced TV (ETV) A general term for several experi- ers, may be positioned between the output of a mental systems intended as an alternative to HDTV. microphone mixer and the input of a VCR. It is also The more formal term for ETV is IDTV, or improved known as graphic equalizer. In video, it acts as a definition TV. The search for an enhanced system multi-function video processor which provides (1) grew out of the need for a compatible process that color and definition control during dubbing, (2) its would not make the millions of current TV receivers own modulator to direct viewing, (3) a distribution obsolete. The topic, however, has become academic amp to permit making more than one copy simulta- since the FCC early in 1990 decided to opt for a neously, and (4) a stabilized image for copying. In true HDTV system as a national standard before con- general, a video equalizer is used to control video sidering any ETV system. Manufacturers of HDTV signal loss. An equalizer provides equalization either have developed simulcast systems in which TV sta- automatically (usually in the case of video) or manu- tions would use one channel for standard NTSC ally (often available in audio mixers). See also Line broadcasts while part of an empty adjacent channel amplifier. would transmit information required for HDTV’s equalizing amp A video circuit preset to provide a wide-screen image. See High Definition TV, IDTV. selected equalization to the video signal. enhancement hardware In video, accessory equip- equalizing pulse One of the pulses occurring just ment designed to electronically improve the video before and just after the vertical synchronizing pulses or audio signal of a recording. Image stabilizers, in a TV signal and serving to minimize the effect of image detailers, line doublers and noise reduction line-frequency pulses on interlace. The equalizing systems are examples of enhancement hardware. pulses occur at twice the line frequency and make enhancement light See Color enhancement light. each vertical deflection start at the correct instant enhancer A video signal processing device that allows for proper interlace. the user to improve picture sharpness and increase equatorial mount Polar mount. color contrast. See also Image enhancer. Equivalent Isotropically Radiated Power See EIRP. envelope delay A type of distortion that takes place equivalent line number (Ne) The line number that during transmission when a phase shift fails to main- defines a rectangle having the same area as the area tain its constancy over the frequency range. Enve- under the aperture response squared curve. Al- lope delay is one of several types of degradation though Ne is not widely used as a criterion of pic- that affects NTSC picture quality. ture quality, it is very useful for TV-system analysis. EOL End Of Life (of a transponder or satellite). erase In video, to clear program material or informa- E’pb Blue color difference, HDTV. E’pb = (E’b — tion electronically each time new material is re- E’y):1.826. See also SMPTE 240M standard. corded. Tape may also be erased by using a bulk E’pr Red color difference, HDTV. E’pr = (E’r — videotape eraser. E’y):1.576. See also SMPTE 240M standard. erase (or erasing) head The device on a tape trans- EP Extended Play. port which erases information before new informa- EPG Electronic Program Guide. tion is recorded to the tape. Flying erase (or erasing) EP speed See Extended play. heads, found on 8mm camcorders and some VCRs, EQ Equalization. provide seamless edits between scenes. In addition, equal energy white Light composed of equal energy they save space by eliminating the larger erase (or of red, green and blue of the correct wavelengths. erasing) heads. White light may still appear white over a fairly wide ERP Effective Radiated Power. mixture of its components. error concealment The ability to hide transmission

109 error correction

errors that corrupt the content beyond the ability of tion sent during the vertical blanking interval using the receiver to properly display it. Techniques for PAL teletext (ETSI ETS 300 706) to control VCRs in video include replacing the corrupt region with ei- Europe (PDC). ther earlier video data, interpolated video data from ETSI ETS 300 706 This is the enhanced PAL teletext previous and next frames, or interpolated data from specification. neighboring areas within the current frame. Decoded ETSI ETS 300 707 This specification covers Electronic MPEG video may also be processed using deblocking Program Guides (EPG) sent using PAL teletext (ETSI filters to reduce blocking artifacts. Techniques for ETS 300 706). audio include replacing the corrupt region with in- ETSI ETS 300 708 This specification defines data trans- terpolated audio data. mission using PAL teletext (ETSI ETS 300 706). error correction In digital video recording systems, a ETSI ETS 300 731 Defines the PALplus standard, al- technique that adds overhead to the data to permit lowing the transmission of 16:9 programs over nor- a certain level of errors to be detected and corrected. mal PAL transmission systems. error detection Checking for errors in data transmis- ETSI ETS 300 732 Defines the ghost cancellation ref- sion. A calculation is made on the data being sent erence (GCR) signal for PAL. and the results are sent along with it. The receiver ETSI ETS 300 743 This is the DVB subtitling specification. then performs the same calculation and compares ETV Educational TV. its results with those sent. If an error is detected the EU-95 One of the projects of EUREKA. A central ob- affected data can be deleted and retransmitted, the jective of this project is to establish standards for a error can be corrected or concealed, or it can simply European HDTV system compatible with the con- be reported. ventional D-MAC and D2-MAC packet DBS systems error detection and handling See EDH. in use there. The organizations principally involved error resilience The ability to handle transmission er- in the project are Philips (Netherlands), Thomson rors without corrupting the content beyond the abil- (France), and Siemens (Germany). Since the project ity of the receiver to properly display it. MPEG-4 is one of the MAC family of DBS systems, it is gener- supports error resilience through the use of ally known as HDMAC (high-definition MAC). See resynchronization markers, extended header code, also Bandwidth reduction (EUREKA-95 HDMAC data partitioning, and reversible VLCs. system). ESCSC Electronic Still Camera Standardization EUREKA A research and development organization Committee. established by the nations of the European Economic ESPN Entertainment and Sport Programming Network. Community. establishment shot A long shot used to set the scene EuroCrypt-M Encryption system in European satellite by showing the environment in which the action to TV, used by Canal Plus, TV3, , TV1000, and follow takes place; e.g., a long shot of a burning a few other programmers. house preceding a medium shot of firemen with europium (Eu) A rare-earth element. Atomic number hoses. Also called establishing shot. is 63. Used as the red phosphor in color TV picture ESU 1. Electronic setup. 2. Engineering setup. tubes and does not change at higher beam currents. E-to-E Also E-E. Electronics-to-electronics. Monitoring This permits operating all three guns at higher lev- the output signal of a VTR while it is recording is an els, giving brighter color pictures. E-to-E process. The signal monitored has not yet been EUTELSAT EUropean TELecommunications SATellite recorded on tape; rather, a sample of the signal is organization. Intergovernmental organization that being fed from the VTR directly to the monitor. With aims to provide and operate a space segment for E-to-E it is not possible to be certain that the signal public intra-European international telecommunica- is being recorded on the tape. tions services. The segment is also used to meet do- ETSI EN 300 163 This specification defines NICAM mestic needs by offering leased capacity, primarily 728 digital audio for PAL. for TV. UK and France are the largest shareholders, ETSI EN 300 294 Defines the (WSS) with about 25 member countries in total. information for PAL video signals. For (B, D, G, H, I) Eu:YSO Europium-doped yttrium silicate. A crystal PAL systems, WSS may be present on line 23. material which, when used together with a preci- ETSI EN 300 421 This is the DVB-S specification. sion-control dye laser, can theoretically record holo- ETSI EN 300 429 This is the DVB-C specification. graphic motion pictures at the rate of 1 frame per ETSI EN 300 744 This is the DVB-T specification. nanosecond. It is theoretically possible to record up ETSI EN 301 775 This is the specification for the car- to 10 million frames. For video recorded at 30 fr/s, riage of Vertical Blanking Information (VBI) data in that would up to 100 hours of recording time. DVB bitstreams. EV European Videotelephony. ETSI ETR 154 This specification defines the basic MPEG even field Field with even number in the interlaced audio and video parameters for DVB applications. field sequence. ETSI ETS 300 231 This specification defines informa- event In video, refers to a timed, recorded, single-

110 extender lens

continuous program. The first VCRs permitted only cording to the reciprocity law, exposure is determined a single event to be programmed for recording per by the product of time and intensity of illumination. 24 h period. Today’s VCRs with their programmable In TV, exposure produces an electronic image, which timers and electronic tuners allow multiple program- is scanned and removed as a signal. ming of several events over a period of as many exposure control Manual iris control. weeks. The greater the programmability, the more exposure level lock A video camera feature that per- expensive the machine. mits the operator to “lock in” the proper exposure event flags In DVI technology, the data elements used setting for a predetermined scene before shooting. by RTX to indicate that something has happened. This helps to compensate for sudden lighting event number A number assigned by the editor to changes, such as the camera panning or the subject each edit that is recorded in the EDL. moving to where backlight would otherwise affect EVR An obsolete electronic video recording device that the exposure. was a miniaturized cassette system played through exposure meter Device for determining the light flux a TV set. Introduced in 1970 by CBS, the unit played incident upon or reflected from a scene to be re- a 7" diameter cartridge of 8.75 mm film containing corded by TV cameras, the corresponding instru- 1 h of programming, through a TV set. The cartridge ments being known as incident-light meters and was produced by exposing film to a beam of elec- reflected-light meters. trons using an electron beam recorder. extended-definition television (EDTV) TV that in- excessive AMTEC error Refers to the improper dupli- cludes improvements to the standard NTSC TV sys- cation of master tapes. Faulty equipment at the copy- tem, which improvements are receiver-compatible ing plant can cause a pattern of dark horizontal with the NTSC standard, but modify the NTSC emis- streaks on prerecorded tapes. The term is often used sion standards. Such improvements may include (a) in conjunction with the recording of professional 2- a wider aspect ratio, (b) higher picture definition than inch tape. distribution-quality definition but lower than HDTV, excitation purity Purity. and/or (c) any of the improvements used in im- exciter modulator The heart of a TV transmitter. Its proved-definition TV. When EDTV is transmitted in outputs are the modulated visual and aural carriers the 4:3 aspect ratio, it is referred to simply as “EDTV.” at low power levels. Exciter modulator includes the When transmitted in a wider aspect ratio, it is re- following components: ferred to as “EDTV-Wide.” 1. Aural preemphasis circuitry to preemphasize the extended play (EP) The slowest speed on a VHS VCR: high-frequency components in accordance with the 6-hour tape speed with T-120 VHS cassettes or FCC requirements. the 8-hour speed with a T-160 cassette. On earlier 2. Processing amps to correct deficiencies, for ex- models, EP was called SLP, probably for Super Long ample, improper sync level, in the input visual sig- Play. The other speeds are Standard Play (SP) and nal and to provide DC restoration. Long Play (LP). 3. Visual and aural carrier generators with the fre- extended resolution format Refers to such video- quency tolerances specified by the FCC. cassette or camcorder recording systems as Hi8, S- 4. Visual and aural modulators. VHS and ED Beta that employ special techniques to 5. Filters to remove the lower sidebands of the modu- enhance the picture quality, thereby producing a lated visual carriers and to remove spurious fre- video image with 400 lines of resolution. One popu- quency components from both carriers. lar method, for example, uses an advanced form of 6. Linearity correction devices in the visual chain to comb filtering to separate signals into groups, which compensate for incidental phase modulation and are then placed into predetermined spaces to pre- differential gain. Ideally, these corrections should vent crosstalk. In addition, some Hi8 camcorders use be made in both the video and RF domains. a CCD image sensor capable of generating more existing-quality television Syn.: distribution-quality than 400,000 pixels. These extended resolution for- television. mats usually require more costly, specially prepared expand Expansion of the picture details within the tapes to capture the additional video information. zoomed picture area. Syn.: zoom in. extended studio PAL A 625-line video standard that exponential antenna A TV receiving antenna that allows processing of component video quality digi- has a series of active elements mounted parallel to tal signals by composite PAL equipment. The signal each other, with element lengths adjusted so their can be distributed and recorded in a composite digi- ends form two natural logarithmic curves. The an- tal form using D-2 or D-3 VTRs. tenna gives good gain over the VHF and UHF TV extended VGA See SVGA. bands. extender A lens accessory that lengthens the barrel exposure Process of subjecting a photosensitive sur- and in so doing reduces the minimum focusing dis- face to light. In photography, exposure results in a tance of the lens and increases the effective f-stop. latent image on a photographic emulsion, and ac- extender lens An accessory lens placed between the

111 external keying

video camera lens mount and the standard lens to voltage applied to the second anode in a CRT, rang- change the latter’s viewing range. Extender lenses ing from about 4 to 50 kV in various sizes of tubes. can be used in conjunction with telephotos and wide Extravision The first national Videotex service in the angles to increase their ranges. Other extenders US, started in 1983 by the Columbia Broadcasting permit 35-mm lenses normally used with film cam- System. It was an over-the-air electronic informa- eras to operate with video cameras. Extender lenses tion service requiring decoders attached to or built can only work with cameras that accept interchange- into TV sets. See also Prodigy. able lenses. extreme closeup (ECU) See BCU. external keying A keying effect accomplished when eye-controlled camcorder See Hi8 Movieboy E1. a particular camera is assigned to supply the key eye-light A small pencil-beam spotlight which, when signal through an SEG. Cf. internal keying, in which directed at subject’s eyes, produces a glitter that any of the cameras can supply the key signal. appears natural on the screen. external sync input A jack, chiefly found on indus- “eyes of a fly” lens Also fly’s eye lens. Lenticular array, trial video recorder decks, designed to allow the unit lenticular raster. Used in 3D-image display systems to to follow the commands of a time base corrector. see an object that is moved in the vertical direction. The inputs help to synchronize signals so that they eye-strain Also eyestrain. A tired or strained condi- can be controlled and mixed with other signals from tion of the eye muscles, caused by too much use or different units. an incorrect use of the eyes. In 3D viewing systems, extra In video production, a player who appears in a methods where both images are printed interleaved, program but has no lines of dialogue except where and the viewer is required to focus his eyes beyond mob voices or voices in unison are required. them in order for them to be perceived as a single extra high tension (EHT) British term for the high DC 3D image, can cause eye-strain.

112 F

F 1. CATV midband channel, 150-156 MHz. 2. TV fade in/fade out A video camera editing feature that standard; Luxembourg. Characteristics: 819 lines/ allows for smooth transitions between scenes. Fade frame, 50 fields/s, interlace—2:1, 25 frames/s, in usually refers to going from dark to light while 20,475 lines/s, aspect ratio—4:3, video band—5 fade out implies going to dark or black. See Fade MHz, RF band—7 MHz, visual polarity—positive, through black. sound modulation—A3, pre-emphasis—50 µs, fade margin The depth of fade, expressed in dB, that gamma of picture signal—0.5. 3. Family—see Movie a microwave receiver can tolerate while still main- rating systems. taining acceptable circuit quality. f Focal length: the relative aperture of a lens, written fade out Syn.: attenuate. To reduce the strength of a as f/ followed by a number. signal, be it audio or video. face Faceplate. fadeout A gradual and temporary loss of a received faceplate Front part of a camera tube on which light radio or TV signal caused by magnetic storms, at- is focused to form the image. In a receiver CRT (ki- mospheric disturbances, or other conditions along nescope), the front of the tube on which the picture the transmission path. A blackout is a fadeout that is formed. Also called face. can last several hours or more at a particular face time The amount of time that the head of a TV frequency. newscaster or other person is shown on the screen. fader 1. A signal processing device that permits fad- face tone Mean light level of a human face properly ing to black or from black to full video. It usually lit for TV. operates with color as well as with black and white facilities An imprecisely defined word that usually re- video. In home video the fader is generally employed fers to the equipment and services which make up a during editing from one VCR to another or from a telecom system. It can mean offices, factories, and/or video camera to a VCR for smoother transitional buildings. In TV, facilities are the physical aspects of a scenes. Many video cameras have a built-in auto- TV station or production company. The term is ap- matic fade-in and fade-out feature, making a fader plied more specifically to technical and production accessory unnecessary with these models. 2. A slid- gear, including distribution amplifiers, camcorders, ing pot control with which an audio or video signal character generators, videotape formats, and all other is faded. production and engineering equipment, and is often fader bar A video switch-control device to dissolve expanded to include the station’s transmitter and earth and fade the picture. station installations. The equivalent of facilities in the fade through black A technique used in video in CATV industry is plant. which a picture or image is made to fade to black fade 1. Optical effect in which a TV scene gradually before a second picture appears. Fade through black disappears into darkness (fade-out) or appears out provides smoother transitions between scenes. Some of darkness (fade-in). One way to do a fade is to use video cameras offer this as a built-in feature; in fact, an alpha mixer. 2. Also, decrease in strength of a not only do they permit fade to black, but they can received radio signal caused by increased attenua- also go from black to full video. Special effects gen- tion, refraction of a beam or cancellation due to in- erators, signal processors and other devices also pro- terference between direct and reflected signals. See vide fade through black. also Fading. fading Variations in signal strength at a receiver due fade duration control A feature designed to adjust to variations in the transmission medium. Destruc- the length of a specific fade. Found chiefly on im- tive interference between two waves traveling by age enhancers/processors, the fade duration con- two different paths to the receiver is the most com- trol operates with both audio and video signals. mon cause of fading; this is termed interference fad- fade in Syn.: bring up. To increase the strength of a ing. Amplitude fading occurs when all transmitted signal, be it audio or video. frequencies are attenuated approximately equally,

113 fan dipole

resulting in a smaller received signal. Selective fad- conventional multiplexing techniques and circuit ing occurs when some frequencies are more attenu- switching techniques because of the way it oper- ated than others, resulting in a distorted received ates. It is one of the transmission technologies be- signal. ing developed for use with B-ISDN (Broadband ISDN). fan dipole A dipole antenna built with triangular sheets The switch used to route packets in a fast packet of metal instead of rods for the reception of all sig- network is termed a fast packet switch. Also, fast nals in the UHF TV band. Input impedance is about packet technology can carry data transmissions that 300 ohms. The figure-eight can enter the network using frame relay. For particularly be changed to a single directional lobe by placing a high speed networking, an implementation of fast wire-screen reflector behind the dipole. packet switching known as ATM has been devel- “fantasy” decoder A type of descrambler used for oped. See ATM and Fast packet multiplexing. satellite descrambling. It uses a 94-kHz sine-wave fast scan See Visual scan. scrambling plus video inversion. Audio is encoded fast-scan Fast-scan TV, also re- on a 15.7-kHz carrier that is 1/6 that of the scram- ferred to simply as amateur TV (ATV), uses a trans- bling sine wave. The 94-kHz sine wave is not an mission format fully compatible with video exact multiple of the scan rate, in general. equipment designed for the home consumer mar- Faroudja, Yves -based French engineer and ket. ATV offers a major advantage over broadcast experimenter in improved, large-screen video; inven- TV, though, and that is rooted in our ability to com- tor who contributed to the development of Super- municate interactively or two ways. ATV people have VHS video recording and the 8mm camcorder. He been communicating in round table nets for many developed a system of enhancing the present TV years—long before industry discovered the benefits picture that, unlike the proposed HDTV, does not of interactive video or, as it’s called, “teleconferenc- make current home TV sets obsolete or alter current ing.” To transmit FSTV, all you need is a home-video broadcasting standards. His method involved dou- type camera, microphone, ATV transmitter and an- bling the number of lines per picture for more im- tenna. Depending on your application, a personal age detail, resulting in a theater-size video image computer terminal or VTR can be used instead of a that almost matched the quality of 35mm film pro- camera. To receive, all you need is an antenna, RF jection. Although his system required the use of ad- converter (also called a downconverter, it shifts the ditional image processors—at relatively little received signal to a standard VHF TV channel) and cost—present TV sets could still derive some ben- an unmodified home TV set. Most ATV is performed efits from the system without upgrading. in the 420- to 440-MHz and 1240- to 1294-MHz Faroudja superNTSC system See SuperNTSC system. segments of the 70- and 23-cm bands. Some ATV fast forward/cue A button to fast-forward wind the activity can be found in the 902-928 MHz band. videotape. When this button is pressed during play- fast-scan television See FSTV. See also Fast-scan back, the picture can be scanned at five times amateur television.

normal speed. +fB See Maximum frequency blue. fast packet multiplexing Multiplexing is putting -fB See Minimum frequency blue.

more than one “conversation” onto one circuit. f0B See Center frequency blue, SECAM. You can do this in either of two ways: by splitting fast search See Visual scan. the channels sideways into subchannels of narrower favor An instruction to a TV camera operator to focus frequency, called frequency division multiplexing, on a specific person or object, as in “favor (name of or by splitting it by time. Fast packet multiplexing performer).” is a combination of three techniques—multiplex- FC 1. Fiber optic connector (developed by NTT). 2. ing, packetizing of analog signals, and computer Footcandle. intelligence. FCC The Federal Communications Commission, the fast packet switching A recent wide-area-network- regulatory board which sets standards for commu- ing technology capable of transmitting data, digi- nication within the US. tized voice and digitized image information. It makes FCC zones Zones with rules that govern the separa- use of short, fixed length packets (or cells) that are tion of broadcasting stations within each zone. There all the same size. The underlying switching technol- are three geographic zones. In Zone 1, the minimum ogy is based on the statistical multiplexing of data co-channel separation is 170 miles for VHF chan- and voice in fixed length cells. Any of these packets nels and 155 miles for UHF. In Zone 2, 190/175. In could carry digital voice, data or digital image infor- Zone 3, 220/205. mation. All the packets travel at Level Two of the F connector A threaded barrel-type metal fitting used OSI model, and routing is performed on the basis of by the TV industry to connect coaxial cable to equip- the Level Two addressing. Fast packet is claimed to ment. The F connector is designed basically for RF be a very effective way of make best use of avail- signals which transmit both audio and video signals. able bandwidth. It is claimed to offer the benefits of An F-barrel connector, with a female thread on both

114 fiber optics

ends, is used to join together two coaxial cables. sions (frequencies). 2. Establishing owner eligibility Also known as coaxial connector, F type connector. for commercial radio and TV stations and their li- FDDI Fiber Distributed Digital Interface. Also Fiber Dis- censing. 3. The qualification and licensing of ama- tributed Data Interface. A set of ANSI protocols for teur and professional radio and radar operators and sending digital data over fiber optic cable. FDDI sup- electronic technicians. ports data rates of up to 100 megabits per second. feed Broadcasts sent by radio and TV networks to lo- FDDI-2 A second generation of FDDI networks that cal stations or by a local station or medium to the support isochronous channels to enable voice and headquarters office or other media. video to be transmitted. feedback The return of a portion of the output of a FDS Frequency Division Switching. Seldom used for circuit or device to its input. See Video feedback. voice switching. Primarily used for radio and TV feeder cables An element of a tree network cable broadcasting. operation consisting of the coaxial cables that con- “feather touch” operation Just a light touch of the nect the cable trunk lines to the cable drop lines. machine buttons or remote control unit keys sup- This intermediate portion of the distribution system plies mode command signals to the various circuits, carries the electronic signals from large trunk-cable motors, switches, and solenoids to set up the se- lines to a specific area or neighborhood of homes. lected mode. Sometimes called feeder lines, they are installed un- FEC Forward error correction, technique used in video derground or strung between telephone poles. compression. feedline A transmission line, such as a coaxial cable. FED Field emission display. A new way of making TV feeder lines Feeder cables. and computer screen displays. FED screens are flat feed horn The component of a satellite TV system and potentially cheap. A typical FED screen packs that is attached to the low noise amplifier and faces millions of tiny individual emitters between two ul- the center of the antenna. The feed horn, usually tra-thin glass layers. Each emitter fires electrons si- rectangular or circular in shape, performs various multaneously across a vacuum gap onto a phosphor functions: (1) it captures the signals reflected from coating very much like a CRT’s. the parabolic or spherical antenna; (2) it shuts out Federal Communications Act: Section 605 The sec- other, interfering signals; (3) it eliminates noise from tion quoted in reference to receiving Pay TV signals land sources; and (4) it directs the received signal without permission or without paying for the into the LNA. Also known as feeder horn, feedhorn. service: feevee Pay TV, pay cable, subscription TV, or any other “No person not being authorized by the sender fee-for-viewing service. shall intercept any radio communication and divulge FEQ Frequency EQualization. Frequency correction. or publish the existence, contents, substance, pur- ferric oxide tape A magnetic audio- or videotape with a port, effect, or meaning of such intercepted com- coating of ferric oxide, a reddish-brown oxide of iron. munication to any person. No person not being Since this chemical occurs naturally as rust (oxidized entitled thereto shall receive or assist in receiving iron), tapes and heads must be cleaned regularly. any interstate or foreign communication by radio ferrite A ceramic-structured, magnetic substance and use such communication (or any information formed by combining iron oxide and other metallic therein contained) for his own benefit or for the oxides under high temperatures. The quality of a benefit of another not entitled thereto. No person videotape depends upon the density of its ferrite having received any intercepted radio communica- particles. Ferrite was developed in the 1930s by the tion or having become acquainted with the contents, Japanese. substance, purport, effect, or meaning of such com- FET Field Effect Transistor. Very thin and small devices munication (or any part thereof) knowing that such used to control pixels in a TFT (Thin Film Transistor) communication was intercepted, shall divulge or display. publish the existence, contents, substance, purport, FF 1. Fast Forward. 2. CATV hyperband channel, 330- effect, or meaning of such communication (or any 336 MHz. part thereof) or use which communication (or any FFTD Frame/Field Transfer Device. information therein contained) for his own benefit FG A frequency generator used in VCR servo circuits or for the benefit of another not entitled thereto. to create FG pulses that related to the speed of the This section shall not apply to the receiving, divulg- capstan rotation. See also Capstan servo, Hall-ef- ing, publishing, or utilizing the contents of any ra- fect IC. dio communication which is broadcast or transmitted fiber Dielectric waveguide that guides light. by amateurs or others for the use of the general Fiber Distributed Data Interface See FDDI. public, or which relates to ships in distress.” Fiber Distributed Digital Interface See FDDI. Federal Communications Commission (FCC) A US fiber optics A technology for transmitting informa- government agency responsible for the following: tion (voice, video, data) via light waves through hair- 1. The policy governing allocation of radiated emis- thin strands of flexible glass. Signals are encoded by

115 fibre

varying some characteristic of the light waves gen- in the waveform to ensure that the R-Y signal does erated by a low-power laser, whose output is sent not reach the B-Y output, and vice versa. through a light-conducting fiber to a receiving de- field interlacing In TV, a process of creating a com- vice that decodes the signals. Fiber optics is one of plete video frame by dividing the picture into two the several new technologies that are revolutioniz- halves with one containing the odd lines and the ing the TV industry. other containing the even lines. This is done to elimi- fibre The European, Australian, Canadian and British nate flicker. spelling. See Fiber. field-neutralizing coil A coil that is placed around A highly reliable, gigabit-per-second the faceplate of a color TV picture tube. Direct cur- interconnect technology, which allows concurrent rent is sent through this coil to produce a constant communications among computers and peripherals. magnetic field that offsets the effect of the earth’s field 1. One half (every other line) of an interlaced TV magnetic field on the electron beams. picture frame. There are 60 fields per second in field-neutralizing magnet A permanent magnet American TV. In twin-interlaced scanning, as used mounted near the edge of the faceplate of a color in most TV systems, two vertical sweeps are needed picture tube to serve the same function as a field- to cover all the lines of the picture and each field is neutralizing coil. Also called rim magnet. thus a half-picture. If the lines are numbered in se- field of view Also field of vision. A scene seen by quence from the top to the bottom of the picture, camera. The video camera scans the field of view in the scanning agent first covers lines 1,3,5, etc. (this its conventional way, first starting at a point, such being known as the odd field) and then returns to as in the upper left-hand corner of the field of view, the top of the picture to cover lines 2,4,6, etc. (this and then scanning horizontally. As it scans horizon- being known as the even field). The field was for- tally it also moves down slowly, then snaps back and merly known as a frame. 2. The area covered by a makes another horizontal scan. This pattern is re- lens. 3. A region containing electric or magnetic peated until the full field of view has been encom- lines of force, or both. 4. An operating location for passed with nearly horizontal lines (in the equipment. conventional manner). Once the camera has com- field blanking In TV, the suppression of the picture pletely scanned the field of view, the scan is then signal during the interval between successive fields. repeated. In most American and Japanese conven- The field-blanking period occupies 13-21 lines in the tional video cameras, the field of view is scanned 60 American 525-line system, and 18-22 lines in the Hz in two interlaced fields, giving a frame rate of 30 CCIR 625-line system. It contains a group of field- Hz, two fields constituting one frame. sync pulses (broad pulses) flanked by groups of field period The time required to transmit one TV field, equalizing pulses, and the line-sync pulses continue equal to 1/60 s in the US. throughout the field-blanking period. field phasing Action of setting the phase of a picture field camera A camera that has the camera head and frame with respect to a synchronizing source so that, the camera control unit (CCU) combined into one on genlocking, a frame or picture roll does not unit. Any adjustments needed must be made be- occur. fore shooting begins. See studio camera. field pickup See Remote. field drive signal Signal used to establish field sync in field producer A person who works outside the head- studio systems—for example, in non-composite quarters TV studio—in the field—to supervise the working. production of programs or segments, as of a news field emission display (FED) Thin, flat, light-weight program. display. In FEDs a tiny CRT sits behind each of the field rate Field frequency. many pixels in the screen. field repetition rate Field frequency. field emitter display technology See Synthetic dia- field sawtooth Waveform which rises at a constant mond display. rate and then falls rapidly, at the frequency of field field frequency In TV, the number of vertical sweeps deflection. made by the scanning beam in 1 s. For interlaced field scanning A process designed to obtain noiseless scanning it is equal to the product of the picture special effects with a VCR. When certain effects such frequency and the number of fields per picture. In as slow motion or freeze frame appear on the screen, most TV systems the field frequency is approximately they are usually accompanied by video noise in the equal to the frequency of the supply mains. In Eu- form of horizontal noise bars, etc. To minimize or rope this is 50 Hz, in the US, 60 Hz. Also called field eliminate this type of interference, some VCR manu- repetition rate; field rate; Fv. facturers have found that by reproducing two fields field identification signal Often called ident signal. instead of one complete picture or frame of a video In the SECAM system, different components of the signal, the final TV picture is cleaner and steadier. A chrominance information are transmitted on suc- picture is composed of one frame of 525 lines or ceeding lines, so that ident signals must be inserted two fields of 262.5 lines each, one containing the

116 film island

odd-number lines, the other the even. Although the ming placed down on moving videotape by one field, therefore, contains only half the information, videohead during recording. Since two fields make it is easier to produce an interference-free picture up one frame, 60 field tracks comprise the 30 fr/s by using this procedure of field scanning. required for the NTSC standard. field-sequential color television A color TV system fifth estate Radio broadcasting and, by extension, TV. whose individual red, green and blue primary colors In ancient times, there were four traditional “estates” are associated with successive fields. It was the first in society. The first was the clergy, the second the broadcast color TV system, approved by the FCC in nobility, the third the commons, and the fourth, the 1950. It was later changed to the NTSC standard public press. To distinguish the new, powerful radio for color broadcasting. medium from the printed page, the term fifth es- An instrument used in the field tate was coined in the 1930s. by CATV service technicians to test the signal fifty-fifty In film and TV, a shot of two people, each strength in various locations where subscribers com- occupying half of the field of view; more commonly plain of weak reception. called a two-shot. field suppression Period between successive fields figure of merit A quality factor used to compare dish which is blanked or suppressed to allow the scan- gain to system noise and written as G/S, where S is ning spot to return to the start of the picture. Also the system noise in Kelvins and G is the gain of the called field blanking. dish in dB. Also, a figure used in electronics that com- field sync signal In TV, the signal transmitted at the pares specific quantities to that of a reference value, end of each field to initiate vertical flyback of the or is used as a comparison between various circuits. scanning beam in receivers so keeping field scan- file footage from the library or file of a TV ning at the receiver in step with that at the trans- station or other source. When used as background mitter. In most TV systems the field sync signal material in a TV newscast, file film generally is iden- consists of one or more pulses (each longer than tified by a line at the top or bottom of the screen the line sync pulse) and so arranged that the conti- with the date on which it was originally taken. nuity of the line sync pulses is not interrupted. filler Fill light. field tilt A form of TV picture distortion, also known fill-in light Fill light. as frame tilt. Normally, reference points on the syncs fill light The addition of lighting in shadowy areas of the correct TV waveform bear a constant rela- within a scene to help balance the proper bright- tion to earth potential, but this relationship may ness and contrast. In studio lighting, light directed be destroyed, e.g., by hum or when the signal is into the shadows to prevent excessive contrast. Also passed through an AC coupling. After the sync sig- called filler and fill-in light. See Lighting. nals are removed from the waveform in a sync sepa- fill signal That signal, or portion of a signal, used in rator stage, the distortion of the video signal keying, , or inserting to replace portions of remains as a gradual brightness increase or decrease the primary signal; any video signal used to replace over the frame period, and the result on the wave- another video signal in a special effects application. form is similar to the addition of a frame-shading film A motion picture; the action recorded on film. A signal. The introduction of a line-by-line clamping motion picture or TV program that is taped often is circuit removes such effects from the signal, pro- incorrectly called a film. vided that the signal has not been modulated by film camera See Camera categories. them. Usually the response of an amplifier is A special motion picture projector com- checked for field tilt by applying a 50-Hz square bined with a video camera to transfer movies to wave to the input. When measured at the output, video. a typical response is residual tilt less than 5% of film clip A bit of film footage, known familiarly as a the output level. Field tilt is sometimes deliberately clip, that is often used as an insert in a TV produc- introduced in the form of frame shading to remove tion. The brief film can be introduced into a live stu- spurious shading signals from the output of a camera dio program to take the viewer outside the studio. tube. In the early days of TV, all such footage was shot on field time base 1. The circuits responsible for gener- 16-mm film or sections were physically clipped out ating the signals causing vertical deflection of the of longer films. Scenes were also cut from theatrical scanning beam. 2. The pattern of and points at which films. Today, such segments are usually shot on vid- a field changes; 60 Hz is the field time base of the eotape rather than film, and the clips from motion American TV system; the field time base must be pictures are also transferred to tape, before they are kept as steady and regular as possible to ensure the used. Although the videos are not cut from the origi- best possible picture. A time base corrector main- nal, the term clip is still used, but without the prefix tains this stability and is part of most professional “film.” editing and recording systems. film island A slide and film projector group, as in a TV field track A diagonal line of information or program- studio.

117 film pickup film pickup Transmission of film to a TV station; now give the desired output curve. For example, commonly replaced by videotape. Chebyshev and Butterworth filters have a flat re- film rundown A list of films, such as a log of films sponse in the pass band whereas Chebyshev filters shown on a TV news program. have some variation of the residual response in the film scanner Telecine. pass band but have a more rapid increase of attenu- film-to-tape transfer A technique of placing films or ation giving a sharper cutoff profile. slides onto videotape. The image from a standard filter factor Numerical factor by which the length of (or slide projector) is protected onto an exposure must be increased to compensate for a telecine adapter and recorded with a video cam- the light absorption of an optical filter through which era. Sound can be added later with the Audio Dub the exposure is made. mode or the VCR. Another method employs a spe- filter kit A package containing various filters to be cial sheeting called Polacoat, which is mounted on used with a video camera. Video filter kits can range a homemade wooden frame and used as a projec- from 5 to 75 filters. Some special effects filters in- tion screen. As the movie or slide projector image is clude a fog filter; a multiple image filter; a prism projected on the screen, a video camera placed be- filter which distorts the light for surrealistic effects; hind the screen records the projected image. One a star filter to turn conventional lights into “starry” disadvantage of this procedure is that titles and print- images; a sepia filter for an old-fashioned look. There ing come out reversed. Professional film-to-tape are also color correction filters. Besides balancing transfer—converting theatrical releases to the home light sources, these can be used to create particular video rental market—presents certain problems that moods: an orange filter can add a feeling of warmth render only a fairly reasonable facsimile of the origi- to a scene while a blue filter can create a cool nal film rather than the more desirable true replica. effect. First, the aspect ratio of the TV screen differs from filter mike A microphone modified to produce sound that of the theatrical wide-screen, resulting either effects, such as an echo or the simulated sound of a in part of the image not appearing on the TV screen voice on a telephone. or a further-reduced image if is used. filterplexer Device incorporating vestigial sideband Second, producers of videocassettes may not always filter and vision and sound combining unit. All TV be fortunate enough to obtain the master positive transmissions use vestigial sideband transmission for of the film. Second or third-generation film prints the vision transmission in order to reduce the large often suffer in contrast, detail and sharpness. Film bandwidth required. To achieve a vestigial sideband enthusiasts and those who work with film-to-tape signal, a filter is necessary to remove the unwanted transfer hope that HDTV will solve these problems. portions of the lower sideband. This can be done in film transfer High-quality motion picture film made the earlier stages of a transmitter, but more usually from an original, usually digital, videotape. Also after the final output stages. called tape-to-film transfer. filter wheel A built-in device, found in most cameras, film transmission In TV, the transmission of a motion that allows you to place one of several filters be- picture. tween the lens of the camera and the beam splitter. filter (color) Transparent material having the charac- Most cameras are set up to operate with TV studio teristic of absorbing certain wavelengths of light in lights, which have a color temperature of 3,200 K. the visible spectrum and transmitting others more If you go outdoors to shoot, you would change the or less undiminished. A narrow-cut filter transmits a filter wheel to compensate for the change of color limited group of wavelengths only, absorbing all oth- temperature. ers, and thus gives a pure or saturated color of light, final character In videotex, the last character of a man- while a wide-cut filter transmits a much more ex- agement command of presentation protocol con- tensive spectral band and the resultant color of light trol information. is less saturated. Sometimes needed for color and final cut See Keeper. black and white recording. final mile In satellite communications, the electronic filter (electrical) An electrical network that will trans- equipment that connects the downlink to the re- mit signals with frequencies within certain desig- ceiving site. Also called last mile. nated ranges (pass band) and suppress signals of finder An optical or electronic device that shows the other frequencies (attenuation bands). The frequen- field of action covered by a TV camera. cies that separate the pass and attenuation bands fine chrominance primary The chrominance primary are the cut-off frequencies, which have the symbols that is associated with the greater transmission band-

fc if there is only one cut-off frequency or f1 and f2 if width in the two-primary US system of color TV. The more than one. Filters are classified according to the fine chrominance primary is the I signal, and has ranges of their pass or attenuation bands as low- frequency components up to 1.5 MHz. The coarse pass, high-pass, bandpass and bandstop filters. The chrominance primary is the Q signal, and has a typi- components of a practical filter may be arranged to cal bandwidth of only 0.5 MHz.

118 flash A/D fine tuning control A control that makes small fixed focal length, usually listed in mm, such as 16- changes in the frequency of the RF oscillator in a TV mm. The fixed focus lens is often called the “nor- tuner, usually with an adjustable capacitor, after mal” lens if it is in the 16-mm range. Other basic switching to a desired channel. types of fixed lenses are the wide angle and tele- finished art Material ready to be produced. photo. The shorter the local length, the wider the finite impulse response filter Also FIR filter. A type area the lens encompasses. Most video cameras of digital filter. Can be any type, such as lowpass, come equipped with a zoom lens for more versatil- highpass or bandpass. ity rather than with a fixed focus type that has a Firewire The original name of IEEE 1394, developed limited angle of view. by Apple Computer. fixed satellite service (FSS) A radiocommunication FIR filter Finite impulse response filter, a type of digi- service between earth stations as specified fixed tal filter. Digital filters in general are much better points when one or more satellites are used; in some than analog filters. Sometimes the only way to de- cases this service includes satellite-to-satellite links, sign a very high-quality filter is with an FIR—it would which may also be effected in the inter-satellite ser- be impossible to design using analog components. vice; the FSS may also include feeder links for other first generation The original recording of a tape seg- space radiocommunication services. ment. The first time the signal is recorded on tape, FL Filter. that tape is called first generation. Every subsequent flag Small rectangle of wood or card mounted on a recording of the already recorded segment will be a stand in the studio to keep direct light off the cam- generation removed. era lens or shade some part of the set. Also called first mile In satellite communications, the electronic French flag. equipment that connects the point of origin to the flagging A defective image characterized by a bent, uplink. pulled or slanted picture at the top of the TV screen. First National Kidisc An LV interactive videodisc re- It is usually a result of too little or too much tape leased in 1981 offering multiple games, activities, tension, a problem known as skew error; an old puzzles and educational programs in which a child model TV set; or a tracking control problem result- from 6 to 12 can participate. It was one of the first ing from tape that has been stretched. Also caused to venture into nonlinear programming (NFL’s “How by copy protection on commercial videocassette to Watch Pro Football” was the first interactive vid- tapes. eodisc). Produced by Optical Programming Associ- flagwaving This is the term used to describe a TV ates, the Kidisc contains 24 chapters, each a set’s ability to accept unstable playback pictures from complete unit that can be located quickly on a vid- a VCR. All home VCRs have some degree of play- eodisc player. The disc is designed to make use of back instability before the active picture is scanned. the many special effects of the VDP. This can cause a bending or flapping from side to fishbowl A booth in a TV studio for observers, such as side of the top inch or so of the screen. This move- sponsors and VIPs. ment is called flagwaving. fishpole Light pole resembling a fishing rod on which flare In an optical or TV image, spurious areas caused a microphone is slung, the whole being projected by scattering of light in the camera or picture tube. out over a scene when dialogue is being recorded. Also undesired light arriving at the image plane in Fishpoles are often used in confined spaces where a an optical system. This light may be uniformly dis- boom would be inconvenient. tributed over the image, resulting in a reduction of fitting An adjustment. A TV fitting is a type of re- image contrast, or it may be concentrated in spe- hearsal, generally of a forthcoming live news event cific areas of the image. Usually the result of reflec- such as a political convention, in which stand-ins tions from surfaces within the optical system. In a are used to test camera angles and other technical TV tube, flare is light produced by excitation of the details. phosphor outside the area in nominal use and fall- five and under A TV role in which a performer has a ing on that area. maximum of five lines. A larger number requires a flash 1. In film and TV, a brief disruption of the pic- higher payment. ture. 2. In videotex, to vary in color at regular inter- Five-Channel System Early CATV system that used vals. In normal flash the characters are displayed TV channels 2 through 6. TV stations received on alternately in the prevailing foreground color and in UHF or on channels 7 to 13 were converted to chan- the prevailing background color. In inverted flash the nels in the band 2 to 6 at the head-end site. At that colors are changed on the inverted phase of the time, the early 1950s, five channels were a lot and flashing clock. In reduced intensity flash the charac- subscribers were more tolerant of system outages ters are displayed alternately in the prevailing fore- and technical problems than they are today. ground color and the equivalent color of the next fix To determine audio or video. A fix is a correction. color table: table A colors adopt table B colors. fixed focus lens In video, a lens of one size, called a flash A/D A fast method for digitizing something. The

119 flashback

signal to be digitized is provided as the source for mits a high field frequency (minimizing flicker) while one input of a whole bank of comparators. The other allowing a low picture frequency (minimizing band- input is tied to a tap of a resistor ladder, with each width). Two types of flicker are encountered in TV comparator tied to its own tap. This way, when the systems that employ interlaced scanning. Large-area input voltage is somewhere between the top and flicker occurs at the field rate, 60 fields/s in the NTSC bottom voltages connected to the ladder, the com- system and 50 fields/s for PAL. Small-area flicker af- parators output a thermometer code: a “” up to fects only vertical detail. It occurs at the frame rate, the input voltage and a “no” above that. The ADC 30 per second for NTSC and 25 for PAL. Large-area then takes this string of Yes’s and No’s and converts flicker involves the entire image area and is the most them into a binary number which tells where the troublesome. The magnitude of the flicker effect Yes’s turned into No’s. depends on two parameters, the field repetition rate flashback See Channel flashback. and the illumination of the retina by the image. flash cutting In film and TV, the use of a series of very Flicker can be reduced and ultimately made unno- brief shots. ticeable by increasing the field repetition or reduc- flashing The blinking on and off of characters, used ing the retinal illumination. to call attention to something on the screen. flickering An effect resulting from copying a projected flash memory A special type of EEPROM that can be movie image with a video camera. Flickering is erased and reprogrammed inside a device. Can be caused by the difference in frames-per-second. Si- used as consumer-camcorder medium instead of lent films travel through the projector at approxi- moving tape. In 1994 Hitachi demonstrated an early mately 18 fps, sound movies at 24 fps—both prototype, which played back full-motion color and different from video, which is synchronized at 30 stereo sound. The camcorder provides 30 minutes fps. The discrepancy between the two systems causes of color recording using as the storage device a 400- flickering. Professional equipment has variable speed megabit multilayered flash memory about the size controls, which can remove this problem. of a sugar cube, uses a single-chip MPEG-1 encoder/ flick pan See Swish pan. decoder and has an electronic zoom system, further flip In video, digital special effect. There are several eliminating moving parts. types of flips. In a page flip the picture rotates around flashover Discharge caused by an excessively high one edge of the screen as if you were turning the voltage breaking down air or surface insulation. page of a book. Other flips can rotate around a cen- flash pan See Swish pan. tral vertical or horizontal axis. See Flipover. flat Large flat mobile piece of plywood or other mate- flip ability Feature found on some laser disc players. rial usually of a standard size in a studio complex. These will play both sides of a videodisc without Basic unit of TV studio set building. A unit of scen- having to turn the disc over. This is convenient, es- ery, essentially the same as used in a stage setting. pecially for CAV discs, which are limited to only 30 A movable wall. minutes per side. flat light Lighting a scene or setting with overall bright- flip card A board or card with a title, name, or mes- ness without noticeable modeling or highlights. sage, used on TV or in a show or presentation; also flat-square Refers to CRTs that are both full-square called cue card. and have relatively flat screen surfaces. flip frame Flipover. flat television receiver A TV receiver whose picture- flipover Also Flip-over. In film, TV, a transitional opti- forming device is thin enough so the entire receiver cal effect, akin to turning over a page; also called can be hung on the wall like a picture. Experimental flip, flip frame, flip wipe, flipover wipe, flopover, CRTs, and experimental flat panels that use thin-film optical flop, or turnaround. integrated-circuit technology based on electrolumi- flipover wipe Flipover. nescence, ferroelectric ceramics, liquid crystals, or flippers Flaps or binders on a spotlight; commonly other optoelectronic techniques have been tried in called barn doors. an effort to obtain a commercial product. See also flip time A videodisc player (with the flip ability) speci- Wall-ready display. fication that indicates how long the machine takes flesh tone corrector Device that restores the original to change from side 1 to side 2. colors of an image; the human eye is most sensitive flip wipe Flipover. to the color accuracy of skin tones. floor 1. The sales-display area of a store. 2. The per- flesh tone reference chart See Video test chart. formance area of a studio. flicker In TV, unwanted regular variation in the bright- floor manager (FM) The production coordinator in ness of the reproduced picture. Flicker can be an- charge of all floor operations not involving engineer- noying when the field frequency is low and, in fact, ing. He or she supervises the erection of sets, place- this consideration sets a lower limit to the field fre- ment of props, live sound effects, talent, cueing and quency that can be used. It was for this reason that the like. The floor manager is the director’s repre- interlaced scanning was adopted because this per- sentative in the TV studio or on the floor.

120 focal length floor plan Plan of TV studio with set or sets indicated riod analogous to the effect of a rotating flywheel on it for use by the director in planning camera posi- in a machine. tions and actions. It shows the position of set pieces, FM 1. Frequency modulation, frequency modulated; objects, talent, cameras, and other production side-band FM. Descriptive of a signal that has been gear. impressed onto a radio carrier wave in such a man- flopover Flipover. ner that the carrier frequency changes as the origi- fluid head tripod A tripod whose camera mount con- nal signal does. 2. Floor manager. sists of two metal plates. The upper, rotating plate FMATV Frequency-modulated amateur TV. rests on a bed of fluid, and the movement provided FM improvement The potential noise reduction in a is very smooth. Necessary for professional pans, tilts FM signal due to the demodulation process. In a and other camera moves. satellite TV receiver this figure is at most 38.6 dB, flutter 1. In video, an effect with VCRs that is caused and is attained above the FM threshold. Below this by very brief and rapid tape speed variations. 2. Dis- point, it rapidly drops from 38.6 dB. Above thresh- tortion that occurs in sound reproduction as a result old: S/N = CN + 38.6 dB. of undesired speed variations during the recording, FM luminance signal The luminance portion of the duplicating, or reproducing process. The variations video signal used to control the frequency of an in speed and hence pitch occur at a much higher astable multivibrator in a VCR. The output of this rate than for wow. multivibrator is a FM signal, shifting from 3.4 to 4.4 flyback In CRTs, the rapid return of the electron beam MHz (VHS) and from 3.5 to 4.8 MHz (Beta). In this to its starting point at the end of each trace. In TV FM conversion, the sync tips are the “at rest fre- there is a horizontal flyback at the end of each scan- quency” of the 4-MHz carrier and the peak white ning line and a vertical flyback at the end of each video signals are maximum deviation. This FM sig- field. Also called retrace. nal is recorded directly onto the magnetic tape. flyback power supply A high-voltage power supply Though slightly different FM frequencies are used in that produces the DC voltage of about 10 to 25 kV VHS and Beta, frequencies around 4 MHz were se- required for the second anode of a CRT in a TV re- lected as the best compromise between head gap ceiver or . The sudden reversal of hori- size, writing speed, and bandwidth. During playback, zontal deflection-coil current in the horizontal output the FM signal is converted back to a standard video transformer during each flyback induces a voltage signal. pulse that is increased to the required higher value FM microphone A wireless microphone designed to by autotransformer action, then rectified and filtered. transmit its signal through the air and extend the Also called kickback power supply. range between the subject and the video camera. flyback transformer Another name for horizontal The signal of an FM mike is picked up by an FM output transformer. The flyback transformer takes radio or receiver which is connected to the audio of the sweep signal from the horizontal output tran- a VCR. Because it is wireless, the microphone al- sistor and builds up the high voltage to be rectified lows the subject to wander within telephoto range for the HV of CRT. The flyback provides horizontal of the camera and still be recorded. sweep for the yoke circuits. FM receiver A radio or TV receiver that detects FM flying head A device that erases—a flying erase signals. head—or reproduces—a flying reproduce head— FM signal, VCR See FM luminance signal. only one track of a tape instead of the entire tape. FM threshold An input signal level which is just flying-spot scanner An imager that produces a video enough to enable the demodulator circuits to ex- signal from an object, such as a film, by scanning tract a good picture from the carrier. With test equip- the object with a spot of light, which is then fo- ment, the static threshold is the point at which S/N cused on a photocell to produce corresponding elec- drops more than 1 dB from the straight graph line; trical signals. The moving (or “flying”) spot of light S/N = CN + 38.6 dB. Typically, the FM threshold is 8 is normally produced on the screen of a high-inten- dB in a satellite TV. sity CRT used as a light source. Mechanical scan- FMV Full-motion video. ning of the object has also been employed, using a f number A lens rating obtained by dividing the focal single point source of light, with a suitably perfo- length of the lens by the effective maximum diam- rated rotating disc between it and the object. eter of the lens. The lower the f number, the shorter fly’s eye lens See “Eyes of a fly” lens. the exposure required, or the lower the illumination flyway A very small satellite newsgathering (SNG) earth needed for satisfactory results with a TV or ordinary station. The extremely portable unit can enable a camera. An f number of 3.5, e.g., is usually expressed live satellite feed from previously inaccessible places as f/3.5. within hours. FO Fiber optics. flywheel circuit Tuned circuit of high Q (figure of merit) focal length 1. Distance between the optical center which maintains oscillations for a relatively long pe- of a lens and the image plane, which, in the case of

121 focal point

the video camera, is the pickup tube’s target area. to 70 ohms for a single-wire dipole. It is popular The distance is measured in mm and determines the with TV and FM receivers. angle of view of the lens. The smaller the focal Folding, Interpolating A/Ds This term describes the length, the more area that can be viewed at any unique technology used in Philips’s family of high- given distance. The larger the focal length, the speed analog-to-digital converters. Designers are smaller the field that can be viewed by the lens at usually forced to choose between the high perfor- that distance. 2. Distance from the center of the dish mance and high power consumption of bipolar flash to its focal point. A/Ds or the low performance and low power con- focal point The point at which all the signals reflected sumption of CMOS A/Ds. By folding comparator in- by a dish join or cross. puts and interpolating the outputs, Philips is able to focal range A measurement in mm that describes the realize an A/D with one quarter the circuitry of a parameters of a zoom lens. For example, the aver- conventional flash converter. That means high per- age video camera has a zoom lens with a focal range formance A/Ds with power consumption as low as of from 12.5 to 75 mm. This lens is also referred to 250 mW. In addition to video, these parts are en- as having a 6:1 zoom ratio. abling new test and medical imaging applications. focus 1. The point of convergence for rays of light or foldover Picture distortion seen as a white line on electrons of a beam that converge to form a mini- either side, top, or bottom of a TV picture. Gener- mum-diameter spot. Some picture tubes are con- ally caused by nonlinear operation in either the hori- structed internally with self-focusing elements, while zontal or vertical deflection circuits of a receiver. in other TV sets, a focus control varies the voltage follow focus The continual adjustment of the lens to applied to the picture tube focus element. This volt- keep an object in focus while either object, camera, age may vary from 4 to 5.3 kV. 2. To move a lens or or both are moving. adjust a voltage or current to obtain a focus. follow shot See Moving shot. focus control A control that adjusts spot size at the footcandle Ft-c, fc. A unit which measures the amount screen of a CRT to give the sharpest possible image. of light on an object emitted from one candle at a focusing 1. The process of controlling convergence or distance of one foot. 100 fc, therefore, would equal divergence of the electron paths within one or more the amount of light 100 candles would cast on an beams to obtain a desired image or current density object from a distance of 1 foot. In video, usually 10 distribution in the beam. 2. The process of moving fc are required for a clear black and white picture an optical lens toward or away from a screen or film and 20 for color. However, black and white cameras to obtain the sharpest possible image of a desired can operate with as little as 1/2 fc. It is the former object. unit of illumination, now replaced by lumens per focusing anode An anode in a CRT that changes the square foot. The SI (International System of Units) size of the electron beam at the screen. Varying the unit of illumination, the lux, is preferred. voltage on this anode alters the paths of electrons footlambert fL. A unit of luminance. A measurement in the beam and changes the position at which they of reflected brightness; used to describe light out- cross or focus. put of projection TV screens. 70 and above is con- focus-mask tube Lawrence tube. sidered very good for these screens. A movie theater focus modulation Variation of the focusing of a cath- screen has a rating of approximately 15 fL. The SI ode ray beam as it is deflected, to compensate for (International System of Units) unit of luminance, the difference in distance from the scanning posi- the candela per square meter, is preferred. tion to the point where the beam strikes the screen footprint A signal pattern by a satellite or the area of of the CRT or the target of a camera tube. the earth that a signal from a satellite can be re- focus puller Member of a video/film crew who is re- ceived from. Each satellite has its own footprint. If a sponsible for controlling focus of the lens while the satellite TV system owner expects good reception camera or talent is moving. from a particular satellite, he/she has to be in its focus servo system System for remote adjustment of footprint. the focus of a TV camera. A small handgrip controls forced oscillations Oscillations produced in a circuit a feed to the motor, which adjusts the focus move- (for example, in vertical or horizontal oscillators of ment of the lens mount. TV sets) that is acted upon by an external driving fog filter A lens filter that lends the effect of fog to a force, such as sync pulses. scene in increments of density from .05 to 3. foreground color In videotex, the color of the graph- foldback A type of small loudspeaker commonly used ics shape that is being displayed in a character cell. in a TV studio or on a stage so that performers can It may be any color from the available color tables hear music or other sound; also called playback. or be transparent. In the latter case the full screen folded-dipole antenna A dipole antenna whose outer background color, the cumulative result of all pic- ends are folded back and joined together at the cen- ture elements previously set, or the video picture is ter. The impedance is about 300 ohms, as compared seen.

122 frame-by-frame recording

format As in video recording formats, which are many fractional T-1 Refers to any data transmission rate be- and varied. 3/4" U-Matic and 1/2" VHS are two for- tween 56 Kbps (DSO rate) and 1.544 Mbps (mega- mats commonly used. Some formats are used in bit/s), which is a full T-1. Fractional T-1 is simply a digital production and broadcasting while others are for line that’s not as fast as a T-1. Fractional T-1 is popular home video use. because it’s typically provided by a phone company format effectors In videotex, control functions that (local or long distance) at less money than a full T-1. influence the positioning of text and pictorial im- Fractional T-1 is typically used for LAN interconnec- ages within the defined display area on a presenta- tion, video conferencing, high-speed mainframe con- tion device. Characters may be positioned within the nection and computer imaging. Fractional T-1 is defined display area by means of format effectors typically provided on 4-wire (2-pair) copper circuits. controls, which move the active position, usually in frame 1. The result of a complete scanning of one units of one character position. image. In motion video, the image is scanned re- form-wound coil A coil that is formed or bent into an peatedly, making a series of frames. In NTSC TV irregular shape, as in a CRT deflection yoke. transmission, a frame consists of two fields, each forward automatic gain control An AGC system in consisting of 262.5 lines, one made up of the odd- which the gain of transistors is reduced by use of number, the other of the even-number lines. 2. A forward control bias. The transistors used for this single complete picture on motion-picture film. For application are so designed that their collector char- 35-mm film the standard rate of projection is 24 acteristics become more crowded at low collector fps. This means that a special projector is required voltages, thus decreasing gain. Used in TV tuners. to convert this to 30 fps for US TV. 3. A group of forward compatibility See Compatibility. data bits in a specific format, with a flag at each forward error correction In DTV and DBS, a correc- end to indicate the beginning and the end of the tion used to minimize the effects of transmission- frame. The defined format enables network equip- channel errors on the integrity of the received signal. ment to recognize the meaning and purpose of spe- This helps to eliminate car-ignition and other im- cific bits. The groups of bits are sent serially (one pulse noise pulses with up to three microseconds after another). Generally a frame is a logical trans- duration. mission unit. A frame usually contains its own con- forward prediction A technique used in video com- trol information for addressing and error checking. pression, specifically compression techniques based A frame is the basic data transmission unit employed on motion compensation, where a compressed in bit-oriented protocols. In this way, a frame is similar frame of video is reconstructed by working with the to a block. 4. In videotex, the basic unit of informa- differences between successive video frames. tion storage and display, a discrete amount of ma- fourth utility The non-vendor specific communica- terial that can be accommodated at one time within tions premise wiring system used for integrated in- the viewing area of a user terminal—generally 24 formation distribution (voice, data, video, etc.). lines of 40 characters each; also called a page or Leviton in Bothel, Washington has trademarked the screen. term fourth utility. They make a broad range of frame accurate This refers to the level of accuracy in premise wiring products. video- or audio tape editing. An edit is considered four-tube color camera An early color camera sys- frame accurate if you can record audio or video ma- tem using one tube to sense each of the primary terial at the exact frame that you specified in your colors (R,G,B) and a fourth to sense black and white edit. values (luminance). Required more exact adjustment frame buffer A section of memory used to store an because four signals had to be coordinated to pro- image to be displayed on-screen as well as parts of duce one picture, and was a larger unit than the the image that lie outside the limits of the display. later 3-, 2-, and 1-tube color cameras. Let’s assume a horizontal resolution of 640 pixels fps Also f.p.s. 1. Feet per second. 2. Frames per and 480 scan lines, and we’ll use the RGB color second. space. This works out to be: 640 x 480 x 3 = 921,600 fr Frame. bytes or 900 KB. So, 900 KB are needed to store

+fR See Maximum frequency red. one frame of video at that resolution. Some systems

-fR See Minimum frequency red. have frame buffers that will hold several frames. f0R See Center frequency red, SECAM. frame-by-frame recording An editing feature, found fractal compression A developing technology for chiefly on more advanced VCRs, that permits the based on principles of fractal ge- user to record specific frames in a range of incre- ometry. It promises high-resolution and impressive ments. These may vary from as few as three to as compression ratios—i.e., substantially reduced stor- many as 33 frames at any one time. This feature age of images. introduces animation, frame-by-frame editing and fractal geometry The underlying mathematics behind other sophisticated editing techniques to the home fractal image compression. enthusiast.

123 frame creation frame creation In videotex, the process of assembling trying to match just one vertical sync pulse from the the elements of a single frame. control track for each vertical sync pulse coming in frame datum A reference time moment given by the from the sync generator. There was no attempt to line datum coincident with the beginning of the first match an even field pulse with an even field pulse equalizing pulse (525 lines standard) or with the be- or an odd field pulse with an odd field pulse. That’s ginning of the first broad pulse in the vertical sync what the frame lock circuitry does. It determines group (625 lines standard). Commonly accepted as whether the vertical sync pulse coming from the sync a timing reference point for color framing and SCH generator is for an odd or an even field. Then it determination in 625 lines standard. Syn.: 0v. speeds up or slows down the tape machine until frame/field transfer device (FFTD) One of the three the pulses off the control track match: odd for odd basic architectures for obtaining the video signal in and even for even. This makes the tape playback solid state cameras. In FFTD a set of charge-transfer just a little more precise. We now have the fields devices—the integrated array—is arranged in the matched, but each field has 262.5 lines, and each vertical (field) direction and exposed to the optical line has a horizontal sync pulse. This leads to the image. During the vertical retrace interval of the TV next level of lock up, horizontal lock. The horizontal display system, the charge pattern that has accu- lock circuitry compares the number of incoming hori- mulated is clocked at high speed into the storage zontal sync pulses with the number of played back area. During the normal horizontal (line) blanking horizontal sync pulses. The VTR then speeds up or periods the pattern of charges in the storage area is slows down the tape in an attempt to match the moved downwards by one line into the bottom hori- two horizontal pulses. See Lockup. zontal register and clocked horizontally to the out- frame period A time interval equal to the reciprocal put to form the video signal. Frame transfer of the frame frequency. In US TV the frame period is architecture suffers from an inherent problem of 1/30 s. overload of the pixel’s storage units in excessively frame rate The rate at which entire pictures are trans- bright sections of the image. This results in vertical mitted. The frame rate of a video source is how fast smear and blooming, which can be reduced by the the source repaints the screen with a new frame. use of frame interline transfer. For example, with the NTSC system, the screen is frame frequency The number of times per second repainted about once every 30th of a second for a that the frame is completely scanned in TV; usually frame rate of about 30 frames per second. For PAL, 30 (25) frames per second, or one half the field fre- the frame rate is 25 frames per second. For com- quency of 60 (50) Hz. Also called picture frequency. puter displays, the frame rate is usually 72-100 frame grab To capture a video frame and temporarily frames per second. store it for later manipulation by a graphics input frame rate conversion The act of converting one device. frame rate to another. One real example that poses frame grabber 1. A device (e.g., PC board) for cap- a difficult problem is that the frame rate of NTSC, turing a single frame of full-motion video and stor- 30 fr/s, is different from a typical computer’s display, ing the image in memory. Used to capture and which may be anywhere from 70 to 75 fr/s. digitize a single frame of video and store it on a frame scanning A process used in a VCR to produce hard disk. See Video capture board. 2. A device on special effects such as slow motion and freeze frame. a TV set to select still pictures—frames—or blocks For example, a freeze frame is created by stopping of text from a bank of such materials for cable-TV the tape while the video heads continue to repro- subscribers. duce the same frame of a video signal. This tech- frame identification (SECAM) V-identification. nique, however, often produces video noise in the frame interline transfer device (FITD) One of the form of horizontal noise bars along with the pic- three basic architectures for obtaining the video sig- ture. To eliminate this type of interference, VCR nal in solid state cameras. FITD was developed to manufacturers have come up with various innova- provide the advantages of frame transfer, but with tions. Some Beta-format machines, for example, resistance to smearing and blooming from exces- utilize four video heads, one pair for producing spe- sive highlights. The unique feature of FITD is a row cial effects, the other set for the tape speeds. Some of selection gates between the image and storage VHS machines, on the other hand, use field scan- areas. The gates are biased so that charges in excess ning to produce noiseless special effects. of a predetermined level are drained from the sys- frame sequential A method of color SSTV transmis- tem before being tranferred to the storage area. sion which sent complete, sequential frames of red, frame lock A method of stabilizing videotape play- then green and blue. Now obsolete. back that tries to match an even field to an even frame set In videotex, a group of frames in sequential field and an odd field to an odd field of the play- order identified by a number. back signal to that of the signal coming from the frame-stopping terminal A device that isolates a sync generator. With vertical lock, the system was single photo or frame of a film for viewing as a still

124 frequency-modulated amateur television

picture on a TV screen; also called frame grabber erized memory bank in the form of digital numbers, and single-frame terminal. which are not affected by video noise. Digital freeze framestore A digital process designed to hold a video frame can also work with images from a live broad- image in memory. For instance, professionally de- cast or CATV. Keeping the VCR in the Freeze Frame signed videowalls use semiconductor memory to mode for long periods of time may damage the video store digital video signals. Each TV monitor in a heads or the tape since the tape is stationary and videowall contains its own framestore, which can pressing against the rotating heads. be a separate image or part of a larger image. freeze frame television The transmission of discrete frame store Electronic memory used to store an en- video picture frames at a data rate which is too slow tire picture (called frame). to provide the perception of natural motion, referred frame store synchronizer (FSS) A device used to lock to as “full-motion.” The transmission of the image up nonsynchronous video signals to the main is typically performed every 30 s from a processing system. unit’s memory where the image is fixed prior to its frame/time search A VDP feature that permits the transmission. An uncompressed, digitized full-mo- viewer to shift to any point on a laser videodisc. The tion video signal is typically transmitted at a rate of feature is often accompanied by an on-screen dis- 90 Mbps. Freeze frame can be carried on anything play that reveals the exact location on the disc and from a simple voice grade phone line operating at length of time it took to reach that point. Some 9.6 Kbps or a DDS (Digital Data System) channel at frame/time search modes offer frame counts with 64 Kbps. the CAV format while others provide real-time dis- frequency band A specified and continuous range of play with the CLV format. frequencies. Different types of transmission require frame tilt Field tilt. different frequency bands. framing 1. Adjusting a TV picture to a desired posi- frequency control See Automatic frequency control. tion on the screen of the picture tube. 2. In video frequency discriminator A discriminator that selects reception, the process of adjusting the timing of the input signals of constant amplitude and produces receiver to coincide with the received video sync an output voltage proportional to the amount that pulse. the input frequency differs from a fixed frequency. framing control A control that adjusts the centering, Frequency discriminators are used in FM systems to width, or height of the image on a TV receiver screen. convert the FM signals to AM signals. The design of free oscillations Oscillations arising in a circuit (for frequency discriminators is such that noise due to example, in vertical or horizontal oscillators in TV amplitude variations in the received signal is almost sets) under the influence of internal force, such as a completely eliminated. capacitor discharging through a resistor. frequency distortion Syn.: attenuation distortion. See freeze 1. The technique often used at the end of a TV Distortion. film as a final scene that remains motionless for a frequency-division multiplexing 1. The transmis- short period. 2. The period of time (1948 to 1952) sion of a single signal, with different information during which no new TV stations were licensed. sent at different frequencies. 2. A form of multiplex freeze field A special effect, similar to that of freeze operation in which each user of the system is as- frame, found on some VCRs. A TV picture consists signed a different frequency band. of 525 line scans, composing one frame. Each frame frequency interlace Interlace of interfering signal fre- is made up of two fields. Many machines in the quencies with the spectrum of harmonics of scan- “freeze” position provide a “still” of two fields or ning frequencies in TV, to minimize the effect of one frame, each video head of a pair recording one interfering signals by altering the appearance of their frame. This is known as a freeze frame. Some VCRs, pattern on successive scans. however, freeze only one field; this tends to present frequency interleaving In the composite TV systems, a clearer, steadier picture with fewer noise bars. The the technique of choosing the color subcarrier fre- freeze field is also known as still field. quency so that the chrominance frequency compo- freeze frame Also still frame. A special effect, found nents of the signal fall between the luminance on VCRs, that locks one frame onto the TV screen. frequency components of the signal. If the Pause mode (sometimes called Still) is pressed frequency-modulated amateur television (FMATV) while the VCR is in Play, the tape “freezes” or be- Fast-scan TV. In the US, used above 420 MHz, with comes motionless and a frame or field appears on majority of activity found in the 1240-1260 MHz the screen. Because some VCRs do not scan an en- segment of the 24-cm band. There are two basic tire frame, noise bars and jitter often accompany techniques for generating a 24-cm FMATV signal. the frozen image. Digital technology, introduced into One method is to use a varactor to triple the ampli- VCRs in 1986, offers noise-free freeze frames. The fied signal from a voltage-controlled 416-433 MHz technique operates by storing a single frame from oscillator that has been video modulated. The other the otherwise moving tape sequence in a comput- approach is to simply amplify the output from a

125 frequency modulation

video-modulated 24-cm VCO. The operation of the sources. When FSK is used for code transmission, FMATV receiver is almost identical to that used for operation of the keyer shifts the carrier frequency home satellite TV reception except for the lower mi- back and forth between two distinct frequencies to crowave carrier frequency and lower FM deviation designate mark and space. Used in digital TV trans- levels typically used by amateurs operating in the mission; transmission speed: 0.8 bits/Hz. 24-cm band. frequency-synthesis tuner A special feature built into frequency modulation (FM) A type of modulation many cable-ready TV sets designed to receive as in which the frequency of the carrier wave is var- many channels as CATV carries. Unlike the analog ied above and below its unmodulated value by an tuning system, the TV receiver with frequency syn- amount proportional to the amplitude of the sig- thesis is pretuned to all the anticipated channels, nal wave and at the frequency of the modulating disregarding the frequencies without channels. With signal, the amplitude of the carrier wave remain- the frequency-synthesis tuner, fine tuning is unnec- ing constant. FM has several advantages over AM, essary but, like many other automatic features which the most important being the improved signal-to- allow no leeway, the tuner presents difficulties with noise ratio. Commercial TV and FM radio use this channels of minimally different frequencies. Also technique, which is much less sensitive to noise and known as electronic frequency synthesizing tuner. interference. frequency translation In re-radiating or distributing frequency modulator An electronic circuit that pro- a radio signal (e.g., by a relay station), it is usually duces a carrier wave signal on which the audio or convenient to change frequency in the device so that video signal is impressed. the amplified signal from the transmitter does not frequency overlap The portion of a 6-MHz TV chan- feed back into the receiver and so cause instability. nel that is common to both the black and white and Such devices are often called translators or frequency chrominance signals in a color TV system. Frequency translators. overlap is a form of bandsharing. See also Color tele- frequency translator See Frequency translation. vision. Fresnel lens Fresnel spot. A specially constructed lens frequency range The useful range of frequencies over that produces a softedged concentration of light; which a transmission system or device may operate used as a lens in a spotlight lamp housing. In some when combined with different circuits under a vari- 3D-image display systems, the Fresnel lens of a fixed ety of operating conditions. In contrast, bandwidth magnification is used in place of the enlarging sec- is a measure of useful frequency range with fixed tion, driver, and controller. The Fresnel lens has a circuits and fixed operating conditions. See also TV function of a flat convex lens to slightly enlarge the channels assignments. size of a stereoscopic image. Other devices utilize a frequency response In video, a term which describes Fresnel lens in front of a CRT display as the substan- the capacity of a system to produce detail or resolu- tial part of 3D viewing. Utilizing a Fresnel lens or tion in its picture. Technically, video frequency re- lenticular lens between the CRT display and the sponse refers to the number of times electron beams viewer is a popular scheme in attempting to present can turn on and off during one full scan from left to 3D viewing of a TV CRT. right on a TV screen. These beams scan the raster, Fresnel zone plate A zone plate pattern (circular or or face, of the picture tube in an exact amount of elliptic) with lowest spatial frequency in the center time, shut off and return to the left side of the screen. and uniform rise of spatial frequency along any ra- This procedure recurs until a complete image ap- dius, so that the spatial frequency is directly propor- pears on screen from top to bottom. The greater tional to the distance from the center. Syn.: bull’s the frequency response, the better the detail in the eye pattern; circular zone plate. picture. Frequency response is expressed as a range; friction head tripod A tripod whose camera mount e.g., 50-9,000 Hz. VCR manufacturers claim a fre- consists of two metal plates, the lower stationary, quency response of up to 12 kHz. the upper rotating; generally does not provide frequency reuse A method that allows two different smooth camera movement: more expensive models TV channels to be broadcast simultaneously on the utilize ball bearings to offset this problem. same transponder by vertically polarizing one chan- fringe area The region just beyond the limits reached nel and horizontally polarizing the other. Another by a TV transmitter. Reception in fringe areas usu- method of frequency reuse is to space satellites about ally results in weak and unreliable signals that need 4 degrees apart. A TVRO pointed at one satellite additional boosting from such devices as a high-gain will not detect any signal from the other satellite, directional antenna or more sensitive receivers. even if it is operating at the same frequency. fringe time A transitional period of a broadcast sched- frequency-shift keying (FSK) A form of frequency ule, immediately before or after the peak period— modulation in which the modulating wave shifts the prime time. output frequency between predetermined values fringing In a color display, the effect caused by incor- corresponding to the frequencies of correlated rect superimposition of the R, G, and B images. In-

126 full field test signal

correct colors appear at the edges of objects in the jector be stationed on the floor in the middle of the image. In a TV set, the convergence alignment would room while the projection screen reclined near an op- need adjusting; in projection TV, it would be the con- posite wall. Some manufacturers, however, disguise vergence controls which require resetting. In video, the projector within a coffee table and the obtrusive excessive chrominance/luminance delay inequality screen is concealed behind curtains. Front projection would cause color fringing. LCD TV systems, which use LCD panels instead of front end Tuner. conventional tubes, are more compact, easier to front loading A VCR system to allow loading the vid- handle and lighter in weight than those models us- eocassette from the front, thus minimizing the space ing image tubes. The rear projection TV system has required for the placement. To load a tape, insert it virtually captured the entire market for projection TV into the loading slot (also called dock). When the systems. Both front and rear systems have certain cassette has been inserted about midway, it triggers drawbacks. Aside from generally costing more than a leaf switch, telling the VCR that a tape is inserted. conventional TV systems, they project an image that The VCR then latches onto the tape and pulls it all lacks the subtle details and contrast/sharpness, quali- the way into the cassette lift mechanism (also called ties that have become standard in direct TV. the elevator or basket). After the cartridge is in the fr/s Frames per second. VCR, the cassette-lift mechanism drops down. When FS Frequency synthesis. The frequency synthesis tun- loaded, the reels of the cassette rest over the supply ing system for a TV set includes a PLL for synthesiz- and take-up spindles inside the VCR. As with the ing local VHF/UHF oscillator signals. When the RF top-loading units, front-load Beta decks automati- input receives standard TV frequency carriers, the cally thread the tape immediately after loading. The mixer combines them with local oscillator signals to tape remains threaded until the cassette is ejected. form IF signals having a picture carrier equal to the Also, a number of front-loading VHS decks use a nominal IF picture carrier frequency. half-loading tape system where the tape is threaded FSK Frequency-shift keying. partially around the inside of the deck. This mini- FSS Frame store synchronizer. mizes tape warping. FST Flat square tube. front porch In a TV signal, the area of the video wave- f-stop Also stop. A calibrated control that indicates form that sits between the start of horizontal blank the amount of light passing through a lens to the and the leading edge of (start of) horizontal sync. target area. The “f” stands for fixed. All lenses used Its purpose is to provide time for a high video signal on video cameras have f-stops such as f/1.4, f/1.8, amplitude (i.e., a white object) at the right-hand side f/2, etc. Numbers are etched on the iris ring on the of the picture to drop down to black level and thence front of the lens, denoting the extent to which the to blanking level before the start of the line-sync iris is closed or opened. F-stop numbers are the prod- pulse. The duration of the front porch is 1.27 µs in uct of a mathematical formula where f is equal to the standard US TV NTSC-signal. the focal length of the lens divided by the diameter front projection LCD TV A technology applied to front of the lens. The f-stop can be changed, depending projection TV which uses crystal display panels in- on the lighting conditions. The smaller the f num- stead of conventional image tubes for projecting a ber, the greater the amount of light entering the large screen image. This system offers several ad- camera. Most low-light video cameras feature an vantages over conventional front projection TV. First, f/1.4 lens. F-stop is a linear, theoretical index, not re- it is more compact and portable. Second, a screen lated to the actual amount of light transmitted by or TV monitor is not essential since the picture can the lens. Actual transmission is measured in “T-stops,” be projected onto any wall. Finally, the LCD system which are determined on an optical bench. can accommodate special anamorphic lenses that FSTV Fast-scan TV. Same as common, full-color, mo- can convert images into wide-screen pictures simi- tion commercial broadcast TV. lar to those seen on theatrical screens. Some mod- FT-C Footcandle. els provide a zoom lens that allows the user to adjust F-type connector Also F connector. A low-cost con- the size of the image to fit a given wall space or nector used by the TV industry to connect coaxial special screen. cable to equipment. See also Connector. front projection TV A projection TV system in which full-color transform Refers to a special visual effect light is projected onto a high gain, silver-like screen that produces a combination of 2-D animation and and reflected back to the audience. The system con- 3-D space. Full color transform is usually one of many tains a TV set/projector, a 1- or 3-lens format and a sophisticated features of a professional/industrial special screen which reflects light much like a mir- character generator unit. ror. The process is similar to that which is used in a Full Field Teletext In this mode, teletext information movie theater. Early front projection TV systems were is transmitted over, virtually, all available TV lines. often cumbersome and difficult to operate. Two- full field test signal Test signal in active parts of all piece systems, for example, required that the pro- active lines of the TV frame (as opposite to VITS).

127 full function wireless remote control full function wireless remote control See Remote tion of the video heads in other machines. Some control. video technicians attribute the inability of a tape to full load A VCR videotape transport system that wraps play accurately on other units to such additional the tape against the video head drum and places causes as variations in the tape transport and width the medium tautly around the appropriate rollers of the video heads of both units. and capstans. The full-load technique allows for functional integrated circuit Electronic circuitry that quicker playing and recording since the tape is in compensates for discrepancies between otherwise proper position for either function. In addition, full similar components. Functional integrated circuit, in- load permits the use of Real-Time Counter, a fea- troduced into such video equipment as portable ture that accurately measures tape usage in hours, VCRs, eliminates the need for the conventional ad- minutes and seconds. Full load differs from the half- justable resistors normally employed for this task. load method, which slows down the initial playing fuzzy Audio or video that is unclear or indistinct. and recording procedures. The original Beta ma- fuzzy logic 1. A new wrinkle in the ancient science of chines utilized full load whereas VHS units used M- controlling processes that involve constantly chang- load, a system that drew tape from the cassette only ing variables. Contrary to its name, fuzzy logic is a in play and record modes. very precise subdiscipline in mathematics. It was in- full-motion video 1. TV transmission where images vented in the 1960s by University of California at are sent and displayed in real-time and motion is Berkeley’s Russian-born Iranian computer science continuous. Cf. Freeze frame. 2. Video reproduc- professor Lotfi Zadeh. It enables mathematicians and tion at 30 frames per second for NTSC-original sig- engineers to simulate human thinking by quantify- nals or 25 frames per second for PAL- or ing concepts such as hot, cold, very far, pretty close, SECAM-original signals. quite true, most usually, almost impossible, etc. It full radiator An ideal radiator and absorber of radia- does this by recognizing that measurements are tion. Its radiation in any part of the spectrum is the much more useful when they are characterized in maximum obtainable from any radiator at the same linguistic terms than when taken to the fourth deci- temperature. The nearest practical form of full ra- mal place. Fuzzy logic reduces a spectrum of num- diator is a cavity with opaque walls maintained at a bers into a few categories called membership groups. constant temperature and with a small opening for Now many consumer goods come with fuzzy logic; observation. It was formerly known as a black body for example, it is used inside camcorders to reduce radiator. the motion of the camera. Fuzzy logic chips are made full scan NEC’s term for . by companies such as InfraLogic Inc. of Irvine, CA. full-square This refers to sharply rectangular CRTs; they 2. In video, a term applied to a camcorder feature come in sizes of 14, 20, 26, and 27 inches. designed to provide better automatic lighting con- full tape interchange The capability of a tape re- trol, especially under difficult conditions. Fuzzy logic corded on one machine to play back properly on uses a special IC to “read” the light intensity of more another unit. Videotapes, especially those recorded than one area of a scene to be recorded and calcu- at the slowest speed, occasionally encounter prob- late the average light value. The technique, intro- lems when they are played back on other VCRs. The duced early in 1990, is said to offer more accuracy picture breaks up, rolls, or contains line or noise bars. and adjust the lens aperture more quickly. Adjusting the tracking control frequently corrects the Fv Frame frequency. anomaly. Tapes recorded at slow speeds tend to be FX 1. Extraneous effects. 2. Film and video special more sensitive to the slight differences in the posi- effects.

128 G

G 1. Green. 2. CATV midband channel, 156-162 MHz. as well. Therefore, if the luminance gain control is 3. TV standard: Austria, , Germany, Italy, set at gain unity, there is neither gain nor attenua- Monaco, Netherlands, Portugal, Spain, Sweden, tion in the brightness level of the signal. Switzerland, Yugoslavia. Characteristics: 625 lines/ gain-up A camcorder feature using digital circuitry to frame, 50 fields/s, interlace-2:1, 25 fr/s, 15,625 lines/ increase sensitivity to light so that the camera can s, aspect ratio-4:3, video band-5 MHz, RF band-8 be used in low-light surroundings measuring only 1 MHz, visual polarity-negative, sound modulation-F3, lux. However, gain-up also has its drawbacks: it is pre-emphasis-50 µs, deviation-50 kHz, gamma of accompanied by an increase in video noise and, of- picture signal-0.5, used band-UHF. 4. General audi- ten, lag or image retention. Gain-up, which is some- ence—see Movie rating systems. times used deliberately to create special visual effects, gaffer The foreman of a stage crew. In film or TV, the such as streaking, is accomplished by digitally boost- gaffer is the head electrician. ing the brightness of the picture. gaffer’s tape A unique and ubiquitous tape used in gallery In the UK, the production control room over- TV and film production. It is 2" wide and made of looking a TV studio. vinyl-coated cotton cloth with an adhesive backing gallium arsenide Symbol: GaAs. High-mobility semi- of synthetic rubber-based resin. It is available in 12 conductor material used in low-noise microwave de- colors and has a tensile strength of 50 pounds per vices—e.g., in satellite TV. inch. Because of its stubborn strength and versatil- galvanometric mirror (GM) In 3D image display ap- ity, it is used for everything in a TV studio. paratus, a device which serves as the vertical scan- gain Video contrast, audio volume. The term used ning system. for contrast in video and volume in audio. Also, game show A radio or TV program in which contes- the whiteness or luminance level of an image. Also, tants are asked questions or participate in contests the degree to which a signal is amplified. RF sig- to win prizes. nals are increased by RF amplifiers while video sig- games on demand In-store recording and delivery of nals are augmented by video distribution amplifiers. video games. A data storage server of the system The gain of an antenna or of a low noise amplifier contains the games and an encoder that burns them is usually a manufacturer specification, and is re- into a blank cartridge. The prospective renter chooses ferred to a reference antenna (usually a dipole or his or her game, and it is instantly recorded on the isotropic radiator). In projection TV screens, gain blank cartridge. The system eliminates the necessity refers to the measured quantity of light reflected of storing hundreds or thousands of titles. by a screen compared to that reflected by a white gamma 1. Measure of the contrast of an image re- matte surface. Therefore, a gain of five translates production process. The characteristics of most dis- generally to a screen five times as bright as a flat plays are nonlinear. A small change in amplitude white surface. when the signal level is small produces a change in gain control See Automatic gain control. the display brightness level, but the same change gain insurance The idea of having a little more signal in amplitude at a high level will not produce the than the minimal acceptable level. In satellite TV, a same magnitude of brightness change. This effect, slightly larger antenna or a lower-noise LNA gives or actually the difference between what you should some gain insurance. have and what you actually measured, is known as gain unity A control on some process amplifiers and gamma. High gamma indicates high contrast; low refers to a neutral position. For example, if the gamma indicates low contrast. In TV, this charac- chroma gain control knob or dial is positioned at teristic is given by the relation between the lumi- gain unity, then there is no increase or decrease in nance increment on the receiver screen and the the intensity of the color signal. Gain unity applies luminance increment in the original scene. In gen- not only to chroma control, but to luminance level eral, this relationship is not uniform over the whole

129

tonal scale and the gamma value or contrast gra- put. But a very narrow gap restricts the output at dient at a given point is of importance. For camera the low frequencies. tubes and similar transmission devices, point gas panel See Plasma panel. gamma is defined as the instantaneous slope of a gas tube See Plasma panel. curve relating the logarithms of the incident light gated sync A scrambling method that operates by and the resultant output voltage, while for receiv- upsetting the sync-pulse amplitude in relation to the ers and display devices, it is the instantaneous slope video signal. It has the effect of making the picture of a curve relating the logarithms of the input volt- tear and roll. age and of the intensity of the resultant light out- gating Operation of an electronic device acting as a put. 2. The third in a series, such as a gamma gate to select a portion of a current signal for ex- generation. See Genealogy. amination or storage, or to activate another circuit. gamma correction Process of modifying the linearity gating pulse Pulse designed to operate a system for a of the amplitude of a video signal in such a way specified period to enable some other action to take that deficiencies in the gamma law of an associated place during the interval. Employed in color TV trans- light-sensitive or picture-display device are corrected. mitters and receivers. Unless the overall gamma of a system approaches Gaussian filter A low-pass filter used for bandwidth unity, the gray scale suffers distortion. In black and limitation and pulse shaping as well as to remove white TV the eye is relatively tolerant of errors, but unwanted distortions such as noise, preshoot, over- in color TV the greatest care is necessary to match shoot and ringing. Its name derives from the ap- gamma laws in the color channels and produce an proximation of its amplitude/frequency response to overall gamma close to unity. Before being displayed, Gaussian distribution or shape. One application of linear RGB data must be processed (gamma cor- the filter concerns the extraction of “spikes” or ring- rected) to compensate for the nonlinearity of the ing in video line sync pulses that may be caused by display. high frequency components. Another use of the gamma corrector, TV camera A typical receiver dis- Gaussian filter is in the field blanking period of TV play tube has a power law relating the light output signals. The filter usually comes in modular form to the signal input of between gamma=2 and for relatively simple insertion into electronic gamma=3. It is therefore necessary to provide equipment. complementary gamma correction to the transmit- GCR Ghost cancellation reference signal. A reference ted signal. In practice, an adequate degree of per- signal on (M) NTSC scan lines 19 and 282 and (B, D, formance can be obtained using a characteristic G, H, I) PAL scan line 318 that allows the removal of with three linear portions each of different gain, ghosting from TVs. Filtering is employed to process both the gain of each section and the level of the the transmitted GCR signal and determine how to change-over or break points being adjustable. The filter the entire video signal to remove the ghosting. sense of the correction is to stretch the black parts ITU-R BT.1124 defines the standard each country of the picture, and the degree of correction which uses. can be tolerated is often governed by the exag- GDI-11 CD-I player; Goldstar. Has two ports: one for a geration of the noise in the dark areas. It is normal mic, and one for a pointing device that lets on-screen to provide for a gain in the lowest portion of the images be manipulated. Like other CD-I machines, characteristic of up to 16 dB above that of the it hooks up to a TV and uses interactive educational average slope. and entertainment CD-I discs. Not available in the gamma generation See Genealogy. US. gap 1. The tiny space in an audio or video head across gel Short form of “gelatin,” a translucent filter mate- which the magnetic field is produced during record- rial used with lighting instruments to change the ing and activated during playback. The head is a U- color, the quality, or the amount of light on a scene shaped electromagnet and it is that opening which in the theater or in TV or film production. Some- the videotape must pass and make contact with for times called a media, this fade-resistant, cellophane- quality recording and playback. Video head gap size like material comes in various colors and is mounted depends on the speed mode of the VCR. Some VHS in a frame that is attached to the front of the light- machines have four heads, two with a specific mi- ing instrument. cron size for standard speed and the other pair de- gel cell A gelled lead acid battery (used for powering signed for the slowest speed (EP or SLP). 2. An portable video equipment). interruption in continuity, such as a blank area on a Gemini A type of combined film and TV camera dis- recorded tape. tinguished from most others of its kind by the fact gap effect, video heads The most important limita- that the primary unit is the TV camera. tion on the range of video frequencies that can be genealogy In film and TV, a numerical history of du- recorded and played back. The narrower the gap is, plicates made from the master film or original vid- the higher the frequency will be for maximum out- eotape, the first generation. The first print of

130 glitch

duplicate tape is the second in the genealogy; the the reflection of signals from tall buildings and other next set of copies is the gamma generation or third objects can present a serious problem at a receiver. generation. This is due to the time difference between the ar- General Purpose Interface Bus (GPIB) A special fea- rival at a receiver aerial of the direct signal and the ture, usually built into some industrial/professional arrival of a reflection or echo. Assuming that the instruments such as color video noise meters, de- direct signal is appreciably the stronger of the two, signed to test various signals automatically. the synchronizing circuits of the receiver lock on to generating element The component that enables the it and disregard the weaker signal. But the video sound waves entering the head of a microphone to section of the receiver is unable to ignore the pic- be used to produce an electronic signal composed ture information contained in the reflected signal, of voltage variations corresponding to the sound with the result that it appears on the screen as a wave; some of the most common generating ele- ghost image. This is displaced to the right of the ments are ribbon, condenser, crystal, and dynamic primary image by an amount corresponding to the elements. difference in time taken by the direct and reflected generation In videotaping, one copy or duplicate re- signals in travelling from transmitter to receiver and moved from another tape. The original or master may be anything up to the full picture width. Ghost program is known as a first generation. A duplicate images resulting from reflections may be reduced from this master is called a second generation tape, or even eliminated by using either a more directional etc. In video production and postproduction, many and properly orientated aerial at the receiver or a generations may be required, causing concern for device known as an echo equalizer. accumulated distortions because of the repeated re- ghost canceling A reference signal to allow specially cording and replay steps. equipped TV sets to get rid of picture ghosts that generation loss The loss of detail or resolution in a result from poor reception of local stations. Devel- video tape that is duplicated. The master tape is oped by Philips Electronics. called a first generation tape. A copy from the mas- ghost cancellation reference (GCR) A reference sig- ter is called the second generation tape. Each gen- nal on (M) NTSC scan lines 19 and 282 and (B, D, G, eration away from the original or master produces H, I) PAL scan line 318 that allows the removal of increased degradation in the image quality. ghosting from TVs. Filtering is employed to process genlock GENerator LOCKing device. A device (e.g., the transmitted GCR signal and determine how to special effects generator) that enables a composite filter the entire video signal to remove the ghosting. video machine, such as a TV, to simultaneously ac- ITU-R BT.1124 and ETSI ETS 300 732 define the stan- cept two signals. A genlock locks one set of signals dard each country uses. ATSC A/49 also defines the while it processes the second set. This enables you standard for NTSC. See Ghost canceling. to combine graphics from a computer with video GIF Graphics interchange format, a computer graph- signals from a second source such as a video cam- ics file format developed by CompuServe for use in era. Genlock determines the exact moment at which compressing graphic images, now commonly used a video frame begins and allows multiple devices on the Internet. GIF compression is lossless, supports (video recorders, cameras, etc.) to be used together transparency, but allows a maximum of only 256 with precise timing so that they capture a scene in colors. unison. Ginsburg, Charles Engineer who, with Ray Dolby, de- genny An electricity generator, particularly a portable veloped the first prototype for the video recorder. generator on a film or television set. Ampex demonstrated the model in 1956. geostationary orbit A circular satellite orbit that is glass delay line One of the two kinds of comb filter 35,000 km (22,300 mi) above the equator. The sat- systems (the other uses a CCD). The glass delay line ellite revolves around the earth in exactly the same technique is less sophisticated, more economical and time it takes the earth to rotate on its axis; thus the more popular. Both types perform the same func- satellite appears stationary over one location near tions. They improve detail and resolution in the TV the equator. The satellite moves from west to east, picture by separating the black and white from the and makes one rotation every 24 h in synchronism color information and thereby preventing video with the earth’s rotation. It is also known as geosyn- moire or a rainbow effect. However, it is generally chronous orbit and as Clarke belt. agreed that the CCD filter is more efficient. geosynchronous orbit Geostationary orbit. glitch 1. An undesired transient voltage spike, occur- GG CATV hyperband channel, 336-342 MHz. ring on a signal being processed. In a digital-to-ana- ghost Vision signal received with a delay, as compared log converter, a glitch can occur at a major carry, to the direct signal, usually caused by reflection from such as when switching from 0111111111 to aircraft or prominent objects. The result is a fainter 1000000000 because there is an interim condition signal (ghost) displaced from the main signal. In the in which all bits are 0. 2. The term given to any type VHF and UHF wavebands used for TV transmission, of video distortion such as picture break-up, etc.

131 glitch-free editing

Also, variations of video noise, etc. Glitch usually designed to connect the measuring instrument to a occurs each time a VCR stops and starts to record. It pin of an IC, socket, transistor, and so forth. is less prevalent when going from the Pause mode gradation Accuracy with which a process in a TV chain to record. Some VCRs provide practically glitch-free renders a series of incremental steps of gray scale. editing. In professional video editing, glitch is an un- graduated matte Variant of background with a stable, broken picture in the final product. The best gradual change from one color to another across way to avoid glitches in the videotape is to pre-black the picture. Syn.: wash. all of the videotape stock with a blank video screen. Grand Alliance 1. Digital HDTV Grand Alliance, a Professional video studios use a black-burst genera- group that represents the merger of three formerly tor for this purpose. 3. A minor technical problem competing groups—AT&T and Zenith, General In- arising in electronic equipment. struments and MIT, and a group consisting of glitch-free editing In video, any method or proce- Thomson Consumer Electronics, Philips Consumer dure that transfers or duplicates selected recorded Electronics, and the David Sarnoff Research Center— segments of tape onto another tape without pic- to collaborate on designing a prototype all-digital ture breakup or the familiar “rainbow” effect that advanced television system. 2. The US Digital HDTV appears where two images are joined. Unlike movie system. The selected digital video-compression tech- film, videotape is difficult to edit because each frame nology is based on international standard MPEG-2. or segment is a diagonal magnetic signal that can- It includes the use of B-frames, a bi-directional frame- not be seen by the human eye. Precise physical splic- motion compensation technique that improves pic- ing is virtually impossible. Therefore, other methods ture quality. A packetized data-transport system have had to be devised to accomplish exact editing. permits most combinations of video, audio, and data At first, home VCRs performed the task rather clum- to be transmitted in packets similar to those formed sily, adding picture breakup, a rainbow effect, or for advanced telecommunications networks. Known more, wherever edits began. Later, some VCR manu- as the ATSC format. facturers introduced improved editing techniques by granularity The density with which a viewing surface backing up the tape a few frames each time the is divided into physical sensors, such as pixels in an Pause and Record modes were pressed. This elimi- image or grains of emulsion in film. nated much of the visual interference. The flying graphic equalizer See Equalizer. erase head was another innovation that helped to graphics In video, a technique involving a computer, a produce glitch-free edits. Another, known as syn- monitor and certain software to create designs, chro edit, synchronizes the start/pause modes of drawing and other graphics on a TV screen. Through both the recording and playback machines during the use of computer keyboards and video terminals, the editing process, thereby eliminating glitches. the electron beam is guided around the screen to Other technological advances for glitch-free edit- produce drawings that can be videotaped. Graph- ing include the use of electronics, digital memory ics programs are available for different systems. They and computers. can create elaborate graphic designs, abstract art, G-matrix In CCD still video cameras, a circuit to form random patterns; they can change screen color, form the high-resolution green signal from the weighted block letters, create a figure and move it anywhere differences of the wideband luminance and low reso- on the screen. lution R and B signals. graphics decoder An electronic accessory, usually built GOP See Group of pictures. into certain CD players, that adds graphics displays Gorizont The Russian geostationary telecommunica- to music. Such machines are known as CD+G (for tions satellite. graphics) players. The visuals produced by the graph- go-to A VCR feature that, when activated, can auto- ics decoder are still pictures; the system is not ca- matically locate any point on a videotape. Go-To pable of producing continuous motion images. See usually operates with either digital tape counters, CD+G. which require entering a specific 4-digit number, or graticule The pattern imprinted on the face of the real-time function in which the hours, minutes and CRT of a color vectorscope for measurement pur- seconds are entered. The latter usually can be acti- poses. The graticule consists of a 360-degree circle, vated by using the remote control. a B-Y horizontal axis line, an R-Y vertical axis line, go to black To let the image fade out entirely. two other lines labeled “I” and “Q” axis and little GPIB See General Purpose Interface Bus. boxes representing the six colors (blue, red, magenta, grabber 1. A device for capturing data—for example, green, cyan and yellow). On some graticules, the a video digitizer. 2. A computer program that takes circle is divided into 5-degree segments. Signals from a “snapshot” of the currently displayed screen im- cameras, VCRs and other pieces of electronic equip- age by transferring a portion of video memory to a ment are superimposed over the graticule to help file on disc. 3. The fixture on the end of a test equip- determine the quality of the color signal and where ment lead wire with a spring-actuated hook and claw any problems may lie. For example, if no “I” signal

132 gyroscopic time base error

appears, then no red will be visible in the TV image; ences in the grounding of house currents from that if there is no “Q” signal, then no green will show of the broadcasting station or TV cable system. up on the TV screen. Ground-loop hum is sometimes referred to simply gray scale A series of achromatic tones with varying as hum. proportions of white and black, to give a full range ground station Earth station. of grays between white and black. A gray scale is group Several stations or other media, generally un- usually divided into 10 steps. der common ownership, such as by Group W, the gray-scale chart See Video test chart. Westinghouse radio and TV stations, or affiliated for gray-scale transfer function A plot of image bright- shared programming or to provide quantity of group ness as a function of scene brightness. It is the TV discounts. equivalent of the H&D (Hurter and Driffield) curves group of pictures In an MPEG bitstream, the GOP is a that specify film density as a function of exposure group of frames between successive I frames, the for photographic negatives. Because the eye per- others being P and/or B frames. In the widest used ceives brightness differences in terms of ratios rather application, television transmission, the GOP is typi- than numerical differences, a logarithmic scale is cally 12 frames but this can vary; a new sequence used for both scene and image brightness. starting with an I frame may be generated if there is grazing A term used by advertisers, producers and oth- a big change at the input, such as a cut. If desired, ers in the TV industry to refer to the practice by view- SMPTE time code data can be added to this layer ers of randomly searching through the channels for for the first picture in a GOP. an interesting program. This practice has alerted the GSR Ghost-Cancellation Reference. networks, TV producers and programmers to seek G/T A figure of merit that describes the capability of a new ways to hold the attention of their viewers. TVRO system to receive a signal from a satellite. The Great Time Machine Quasar’s first (now defunct) VCR, ratio (in dB) of the gain of a receiving system to the model VR-1000, which was incompatible with its noise temperature of the system. two contemporary formats, VHS and Beta. The GTM guard band A space between video tracks on the video was introduced in 1976 and used a cassette format tape when in the SP mode to eliminate “crosstalk” called VX200. The machine was eventually replaced between tracks. Guard band contains no informa- in 1978 by Quasar’s second VCR, model VH-5000, a tion. The introduction of the azimuth process of elec- more conventional VHS machine. The original re- tronically printing video tracks diagonally, each with corder had one unique feature for its day—its clock/ a different pattern, has largely discontinued the need timer could be set to record more than one event or for guard bands. 2. A frequency band left empty program during a 24-hour period. between two channels to protect against interfer- Green Book The formal standards document for ence from either channel. See also Broadband. CD-i. guard circuit In TV receivers, a device in integrated green gain control An adjustment used in the matrix vertical deflection circuit with flyback generator. of a 3-gun color TV receiver to adjust the intensity When there is no deflection current and the flyback of the green primary signal. generator is not activated, the guard circuit produces green gun The electron gun whose beams strikes phos- a DC voltage to blank the picture tube and thus pre- phor dots emitting the green primary color in a vent screen damage. 3-gun color TV picture. gun killer An adapter that can be inserted between green restorer The DC restorer for the green channel the socket and base of a color picture tube, to per- of a 3-gun color TV picture tube. mit turning off independently any one or all of the green video voltage The signal voltage output from three guns (red, green, and blue) in the tube during the green section of a color TV camera, or the signal repair or adjustment procedures. voltage between the receiver matrix and the green- guy A rope, cable, or wire—guy wire—to hold or steady gun grid of a 3-gun color TV picture tube. something, such as to support a TV antenna tower. grid card A tabulated rate card of a radio or TV sta- G-Y matrix A circuit to construct color difference signal tion with rates for various time periods. G-Y according to the equation G-Y = -0.51(R-Y) - grid log A schedule, as of TV programs, printed in a 0.19(B-Y) by means of an addition/subtraction pro- set format, such as the charts now used by many cess using color difference signals R-Y and B-Y newspapers instead of or in addition to a running (SECAM). The G-Y is composed of -0.27(R-Y) – 0.22 log, or sequential list of programs. In a grid log, the (B-Y) (NTSC). TV channels appear vertically in the first column, gyrator delay cell See Luminance delay line in gyra- while their programs are listed horizontally in the tor technique. time-period columns. gyroscopic time base error Time base error that is ground-loop hum Refers to the large horizontal bars created when a VTR is moved perpendicular to the that occasionally roll up or down on the screen im- plane of the head drum’s rotation. It is a very com- age. This video hum appears as a result of differ- mon occurrence given today’s highly portable video

133 G-Y signal

equipment. Gyroscopic error occurs because the depends on all of these factors. It could be less than spinning head drum in the VTR acts like a gyroscope. a line in a studio machine, or could add up to 20 or As the VTR is moved against the plane of rotation of 30 lines or more on a field recorder. the head drum, the spinning drum resists and slows G-Y signal The green-minus-luminance color-differ- down a little. When it slows down, the information ence signal used in color TV. It is combined with the will not be recorded at the proper speed. How much luminance signal in a receiver to give the green color- time base error you might expect on tape playback primary signal.

134 H

H 1. CATV midband channel, 162-168 MHz. 2. TV H.26L Emerging video coding standard for next-gen- standard; Belgium. Characteristics: 625 lines/frame, eration compression technology. (To be part 10 of 50 fields/s, interlace—2:1, 25 fr/s, 15,625 lines/s, MPEG-4.) aspect ratio—4:3, video band—5 MHz, RF band—8 H.320 International standard for video conferencing. MHz, visual polarity—negative, sound modulation— H.324 Videoconferencing standard for public switched F3, pre-emphasis—50 µs, deviation—50 kHz, telephone networks. gamma of picture signal—0.5. hacker A slang term for a computer enthusiast. De- h Hour. Also hr. The plural is hrs. pending on how it is used, the term can be either H0 See H-channel. complimentary or derogatory. The pejorative sense H11 See H-channel. of “hacker” is becoming more prominent largely H12 See H-channel. because the popular press has coopted the term to H.221 A framing recommendation that is part of the refer to individuals who gain unauthorized access ITU’s H.320 family of video interoperability Recom- to systems for the purpose of stealing and corrupt- mendations. The Recommendation specifies syn- ing data. The term is sometimes used in other fields chronous operation where the coder and decoder as well, such as a video hacker. handshake and agree upon timing. Synchronization Hadamard transform A video compression technique. is arranged for individual B channels or bonded 384 HAD (Hole Accumulated Diode) sensor A component Kbps (HO) connections. of some top-of-the-line professional/industrial video H.230 A multiplexing recommendation that is part of cameras that increases horizontal resolution and en- the ITU’s H.320 family of video interoperability rec- hances color quality. The special sensor can produce ommendations. The recommendation specifies how 700 lines of horizontal resolution. individual frames of audiovisual information are to hair-pin Connector encased in a small block of plas- be multiplexed onto a digital channel. tic. Used in patch panels. H.231 A recommendation, formally added to the ITU’s halation In a CRT, degradation of the image caused H.320 family of recommendations in March, 1993, by an area of light surrounding the spot where the which specifies the multipoint control unit used to electron beam strikes the screen. This unwanted area bridge three or more H.320-compliant codecs to- is caused by light from the spot reaching the screen gether in a multipoint conference. by reflection at the front and rear surface of the face- H.233 A recommendation, part of the ITU’s H.320 fam- plate of the tube. Also called halo. ily, which specifies the encryption method to be used half-inch format Refers to the most commonly used for protecting the confidentiality of video data in tape size for home video. VHS machines use 1/2" H.320-compliant exchanges. Also called H. key. videotape while profession/industrial/institutional H.242 Part of the ITU’s H.320 family of video equipment uses other widths such as 3/4" and 1" interoperability recommendations. This recommen- tape. Newer, smaller VCRs for home use have intro- dation specifies the protocol for establishing an au- duced 1/4" videotape, particularly with camcorders. dio session and taking it down after the half-lap In film and TV, a split screen in which two communication has terminated. images appear simultaneously on the screen—a side- H.261, H.263 The ITU-T H.261 and H.263 video com- by-side shot. pression standards were developed to implement half loading system In the FF and REW modes of a video conferencing over ISDN, LANs, regular phone VTR the system keeps the tape half-loaded to allow lines, etc. H.261 supports video resolutions of 352 x a sensor to detect tape movement by reading the 288 and 176 x 144 at up to 29.97 frames per sec- tape’s control track and display the lap time in hours, ond. H.263 supports video resolutions of 1408 x minutes and seconds. Also see Front loading. 1152, 704 x 576, 352 x 288, 176 x 144, and 128 x half-transponder A method of transmitting two TV 96 at up to 29.97 frames per second. signals through a single transponder, by reducing

135 Hall effect

the deviation and power allocated to each. Half-tran- clear, sharp image. Sony’s compact Video Walkman sponder TV carriers each operate typically 4 dB be- combines an 8mm video recorder with a 3" LCD low single-carrier saturation power. color TV. Hall effect An audio technique that is not affected by handshaking An exchange of predetermined signals tape speed in the playback mode. Since tape speed for the purpose of control when a connection is es- influences the quality of audio reproduction, the slow tablished between two data sets. speeds of videotape produce far from good sound. Handycam The camcorder that integrated the cam- But videotape must use these relatively slow speeds era and recorder. to accommodate the video signals and to offer rea- hangers Lighting accessories formally known as “an- sonable maximum playing time. If a process, such tigravity hangers.” They are used to hang lights on as the Hall effect, can be developed to be used with a pipe grid above a TV studio. The devices are accor- recording as well as playback, audio quality will dion-like mechanisms that are counterbalanced with greatly improve. springs and thus allow the easy raising and lower- Hall-effect sensor A set of Hall-effect ICs to provide ing of a light to any height. precise timing of head switching. It is accomplished happy talk A format of TV news programs, featuring by a feedback mechanism provided by the set of light banter among an ensemble of newscasters. Hall-effect ICs, which are the electronic equivalent hard copy Output onto permanent media such as pa- of reed switches. In older Beta and VHS models, coils per or film as opposed to a CRT screen. and magnets were used instead of Hall-effect hard-edge wipe In film and TV, a wipe (an optical sensors. effect between two succeeding shots) in which the Hall-effect IC A magnetically sensitive integrated cir- border between the two images is sharply defined; cuit that can detect the presence or absence of a the opposite of soft-edge wipe. magnetic field. In VCRs, Hall-effect ICs generate two hardline A low-loss coaxial cable that has a continu- types of pulses: PG and FG. PG stands for pulse gen- ous hard metal shield instead of a conductive braid erator; FG stands for frequency generator. The PG around the outer perimeter. This type of cable was signal, typically at 30 Hz, identifies the position of used in the pioneer days of satellite TV. Syn.: Heliax. the drum as it spins. The rate of the FG signal, most hard scrambling An encryption method that uses pro- often 180 Hz, indicates the speed of the video-head prietary, highly secure technology (digital). drum. hardware In video, equipment such as VCRs, VDPs, halo 1. An undesirable bright or dark ring surround- video games, video cameras, portable VCRs, TV sets, ing a spot on the fluorescent screen of a TV CRT. etc. Videotapes, discs and game cartridges are con- Generally due to overloading or maladjustment of sidered software. the camera tube. 2. The black area around a very harmonic distortion See Distortion. intense source of light, as seen by the camera and harmonic related carrier (HRC) Refers to cable-TV monitor. When a match is struck and held in front systems having a coherent head end and visual car- of the camera, a halo is visible around the flame; a riers located at multiples of 6 MHz starting at 54 halo visible through the viewfinder of a vidicon cam- MHz. All visual carriers in the system are phase locked era may mean that the light source is bright enough to a 6-MHz master oscillator. This ensures that all to burn the target area. the carriers are harmonically related to 6 MHz and Hamming code In digital transmission, a code so de- no matter what shift occurs to the master oscillator, signed that errors in signals can be detected and all carriers maintain the same relative frequency sepa- corrected. The code has four information bits and ration. The second- and third-order intermodulation three check bits per character. See Parity check. products resulting from any two carriers, therefore, Named after R. W. Hamming of . always fall exactly on the visual carrier frequencies, hammocking The practice of scheduling a weak TV and their undesirable effects on TV pictures will be program between two strong ones—suspended the reduced or eliminated. When compared with the way a canvas hammock hangs between two sup- broadcast or standard plan, HRC channels are fre- ports. The popular programs are in the tent-pole po- quency displaced by –1.25 MHz on all standard and sitions and the weak one is settled in the saddle cable supplementary channels (midband, etc.) ex- position. cept channels 5 and 6, where the displacement is handbasher In film and TV, a hand-held lamp, usually +0.75 MHz. about 800 watts. harry system In film and TV, a digital animating ma- hand-held television A small, light-weight, portable chine that stacks computerized graphics and other TV unit, usually applying LCD technology and other images on top of each other to create the illusion of electronic refinements to the video portion. Some three-dimensionality. manufacturers concentrate on increasing the num- H-channel The packet-switched channel on an ISDN ber of pixels per square inch to ensure accurate color BRI (Basic Rate Interface) which is designed to carry separation. Others focus on resolution to produce a user information streams at varying rates, depend-

136 HD-SIF

ing on type: HO—384 Kbps; H11—1,536 Kbps; and Four uncompressed audio channels sampled at 48 H12—1920 Kbps. kHz, 20 bits per sample, are also supported. HD-0 A set of formats based partially on the ATSC HD-CIF See CIF. Table 3, suggested by The DTV Team as the initial HD D5 A compressed recording system developed by stage of the digital television rollout. Pixel values Panasonic that uses compression at about 4:1 to represent full aperture for ITU-R 601. record HD material on standard D5 cassettes. HD HD-1 A set of formats partially based on the ATSC D5 supports the 1080 and the 1035 interlaced line Table 3, suggested by The DTV Team as the second standards at both 60 Hz and 59.94 Hz field rates, all stage of the digital television rollout. Pixel values rep- 720 progressive line standards and the 1080 pro- resent full aperture for ITU-R 601. gressive line standard at 24, 25 and 30 frame rates. HD-2 A set of formats partially based on the ATSC Four uncompressed audio channels sampled at 40 Table 3, suggested by The DTV Team as the third kHz, 20 bits per sample, are also supported. stage of the digital television rollout contingent on HD Digital VCR Conference A group of major manu- some extreme advances in video compression over facturers dedicated to setting standards for HDTV the next five years. Pixel values represent full aper- VCRs. The Conference defined the specs for stan- ture for ITU-R 601. dard definition (SD) and high definition (HD) VCRs. HDB-MAC (High-Definition B-MAC) system (also Sci- The SD VCR records at a data rate of 25 megabits entific Atlanta HDB-MAC System) It was a per second. It is used for of NTSC, noncompatible service intended for direct-broadcast PAL, SECAM and the Grand Alliance HDTV format. and fixed satellite use. It was based on the B-MAC The HD VCR records at 50 megabits per second. It is service now standardized in Australia and widely intended for recording Japan’s MUSE HDTV satellite used for business applications of TV. It was closely broadcasts, which have a much higher bandwidth related to the D2-MAC system used for DBS service than the Grand Alliance format. Unlike SD decks, in Europe. The HDB-MAC signal was transmitted at HD decks may use four heads. Although the MUSE 525 lines interlaced, permitting simple conversion signal is analog, HD decks record it digitally. They to the NTSC service. In the HDTV receiver a field- are compatible, so that HD decks will play SD tapes. store was used to convert to 525/59.94/1:1/16:9 pro- HDMAC (High-Definition MAC) A European DBS HDTV gressive scan. When so converted the vertical system. It was spawned by Britain’s Independent resolution was 480 lines per picture height for static Broadcasting Authority. Unlike Japan’s HiVision, areas of the image, 320 lines for moving areas. The HDMAC has the attraction of being compatible with horizontal resolutions were stated to be 950 lines existing TV sets—i.e., those in Europe. Employs twice per picture width for static areas, 320 lines for mov- the line rate of the 625-line MAC system at an as- ing areas. The total number of picture elements for pect ratio of 16:9, interlaced, i.e., 1250/50/2:1/16:9. static images was 950 x 480 = 456.000 per frame. The luminance and chrominance basebands are, re- When the 16:9 aspect ratio was used at the source, spectively, 21 MHz and 10.5 MHz. By 3:2 and 3:1 the portion intended for 4:3 displays was under pan- compressions, respectively, a common sampling fre- and-scan control. The line signal frequency modu- quency of 20.5 MHz is achieved and this imposes a lated the up-link signal on the 24- or 27-MHz maximum modulation bandwidth of 10.125 MHz. transponder channel. This signal permitted display This is the up-link frequency modulation of the sat- at 525 lines sequentially scanned at 16:9 aspect ra- ellite signal, using the 27-MHz bandwidth available tio, with a luminance baseband of 18 MHz. Although in Europe. Additional information (sound/data/DATV) not designed for cable service, it was pointed out is carried by multiplex in the vertical and horizontal that the up-link signal could be accommodated on blanking intervals. two contiguous cable channels. The source base- HD-NTSC system (also Del Rey HD-NTSC system), Del band was reduced to 10.7 MHz by the spectrum Rey Group. It was a single-channel NTSC-compat- folding. The source baseband was recovered at the ible HDTV system, operating on the 6-MHz channel HDTV receiver by a field-store line doubler that pro- at 59.94 fields per second. This system differed from vided 18 MHz of luminance bandwidth and 5 MHz conventional practice in two major respects: an as- for chrominance. pect ratio of 14:9 and double-trace scanning at the HDCAM Sometimes called HD Betacam, this is a means camera and the HD-NTSC receiver, which spread the of recording compressed high-definition video on a scanning sequence over three frames. The number tape format (1/2-inch) that uses the same cassette of active lines was reduced from the NTSC value of shell as Digital Betacam, although with a different 484 to 414, and the 70 additional blank lines were tape formulation. The technology is aimed specifi- disposed above (35 lines) and below (35 lines) the cally at the USA and Japanese 1125/60 markets and display. The additional vertical blanking time pro- supports both 1080 and 1035 active line standards. vided a channel for digital transmission of stereo Quantization from 10 bits to 8 bits and DCT intra- sound. frame compression are used to reduce the data rate. HD-SIF High Definition—Common Image Format.

137 HDS-NA

HDTV system. This system has a set of parameter develop international standards to make HDTV a values which use 1080 active lines, whether the field reality. In 2002, HDTV equipment is on the market rate is 50 Hz or 60 Hz. The same sampling frequen- and some broadcasting has begun. See ATSC, high- cies for interlace (74.25 MHz) and progressive (148.5 definition television. MHz) scanning are used in the 50-Hz and 60-Hz ver- HDTV-ready set A 16:9 TV receiver with RGB YPbPr sions of the format. input, which can accommodate an HDTV decoder. HDS-NA High-Definition System—North America; N. HD VCR See HD Digital VCR Conference. A. Philips Corporation. A wide-channel 525/59.94/ HD VTR See High definition VTR. 1:1(NTSC) 1050/59.94/ 2:1(HDTV) system. Aspect HE Head End. ratios were 4:3 (NTSC), 16:9(HDTV). The HDS-NA head 1. A device which records information on a stor- system employed two principal signals. The first, HD- age medium, reproduces the information or erases MAC, was a satellite-transmitted multiplexed ana- it. The storage medium may be tape, film or disc and log component signal from the program origination the information may be in digital form as in data- point to other transmission media, i.e., terrestrial processing equipment or may be in analog form as in broadcast and cable systems. It could also serve in audio and TV (conventional) recording. 2. The top the direct-broadcast service. The second signal, portion of the tripod to which the camera is attached. named ND-NTSC by Philips, was intended for the Allows for camera motion. Also called pan head. terrestrial and cable services. It comprised the NTSC- head amplifier An audio or video amp incorporated compatible 6-MHz channel and an augmentation in a microphone, TV camera or motion picture pro- channel. The augmentation information was pro- jector to raise the level of the output signal before it posed for transmission either in digital or analog is sent along a cable. This technique is used as a form. Also called Philips HDS-NA. means of improving the signal-to-noise ratio. HDS-NA “6+3” A “6+3” version of the HD-NTSC, head crossover See Search-forward (cue), Search-re- which consisted of an NTSC-compatible 6-MHz verse (review). channel and a 3-MHz augmentation channel. The head cylinder Syn.: head drum. HD-MAC output contained the following compo- head drum In VCRs, polished metal cylinder with video nents, which had to be accommodated in the HD- heads. Also called scanner; head cylinder; head wheel. NTSC encoder: (1) the line-difference signals for the The video-head drum spins under propulsion from a central and sidepanel areas of the 16:9 image; (2) direct-drive motor (in some early VCRs, the drum was the standard 4.2-MHz luminance signal; (3) the operated by an ac or dc servo-controlled motor). This higher-frequency portion, Y, of the luminance con- direct-drive motor contains no brushes, just coils and tent as separated from the low-frequency portion magnets. The coils in the motor (usually three) are in the HD-MAC encoder; (4) the sidepanel I and Q switched on and off via a servo circuit. chrominance signals; (5) the right and left sidepanel head drum rotation detector, VCR When any of the luminance contents of the 16:9 display; and (6) the function buttons are pressed, the system control cir- digital data and audio signals decoded from the HD- cuit detects the head drum rotation by detecting MAC transmission. In one version of the “6+3” sys- the 30 PG pulses. If for any reason the head drum tem, these components were accommodated in the rotation should stop, the auto-stop circuit is ener- 6-MHz and 3-MHz channels. gized. HDS-NA “6+4” This high-definition system developed head drum servo One method, now largely obso- by Philips Corp. was never introduced commercially. lete, of controlling the video tape during playback A more advanced “6+3” by the same company so that the video heads contact the tape with the made it obsolete. proper timing (sync) to retrieve the information on HD-SDTI High Data-Rate Serial Data Transport Inter- the tape. The control track pulses are used to con- face, defined by SMPTE 348M. trol the rotation of the video heads. See Capstan HDTV High-Definition TV. The 1,080-line interlace and servo, which is the far more common tape control 720 and 1,080-line progressive formats in a 16:9 setup. aspect ratio. HDTV thus means a completely new head drum servo editing An editing method that is TV system with substantially high resolution, a wider an inferior variation on capstan servo editing. In- aspect ratio, and improved sound. The U.S. FCC has stead of the tape being slowed down or speeded adopted (1996) the major elements of the ATSC up to maintain sync, the speed of the video heads is Digital Television (DTV) Standard, mandating its use varied by the use of the head drum servo controls. for digital terrestrial television broadcasts in the U.S. head end (HE) The portion of an SMATV system where The specific HDTV and SDTV video formats contained all desired signals are received and processed for in the ATSC standard were not mandated, but many subsequent distribution; the originated point of a of these have been uniformly adopted on a volun- signal in cable TV systems. At the head end, you’ll tary basis by broadcasters and receiver manufactur- often find large, tall TV and dish satellite receiving ers. HDTV is a subset of DTV and work is ongoing to antennae.

138 color process

head override editing Capstan servo editing. helical Describes a general type of VCR in which the headphone An electroacoustic transducer designed tape wraps around the video head cylinder in the to be held against an ear by a clamp passing over shape of a 3-dimensional spiral, or helix. The video the head, for private listening to the audio output tracks are recorded as a series of slanted lines. of a communication, radio, or TV receiver or other helical antenna The radiating elements are two he- source of AF signals. Usually used in pairs, one for lixes, one above the other, wrapped around but sepa- each ear, with the clamping strap holding both in rated from a supporting pole. The two are wrapped position. Also called headset and phone. in opposite directions, with the result that the verti- head position detecting unit In autostereoscopic 3D- cal components of the radiation from the two halves image display systems, a device to detect the head cancel each other while the horizontal components position of the viewer: it generates a display control are reinforced. Used in TV transmitting systems. command to the computer when the head position helical scan Storage method that increases media ca- of the viewer has moved by only the distance be- pacity by laying data out in diagonal strips. Used in tween the right and left eyes. VCRs. headroom In film, TV, the field of vision between the helical scan processor See . top of a performer in a film or TV program and the helical spiral The standard method of scanning vid- top of the motion picture or TV screen. In a close- eotape (helical scanning), in which the tape moves up, the headroom is diminished. from the supply reel in a helical, or spiral, path around headset Headphone. one or more recording or replay heads. In helical head shot A close-up view of a subject, encom- videotape recording systems, the heads are angled passing the subject from top of head to top of and the tape has a slanting path, so helical scan- shoulders. ning also is called slant-track scanning. heads out A reel of tape wound so that the begin- helical wind The screwlike configuration of the tape ning of the program is at the beginning of the tape; across the video heads, from the plane of the sup- a rewound tape. See Tails out. ply reel, through the plane on which the heads are head-switching interval A sometimes-visible line on rotating, to the plane of the take-up reel. the TV screen indicating the completed function of helium-neon (H-N) laser A component for the optics one video head and the start of the second head. If of many early-model CDV players instead of the the line appears on the screen, it can be removed in solid-state laser diodes now in common use. one of two ways. The head switch can be set lower helper signal See ACTV-1. or the vertical size control can be adjusted until the hemispheric satellite See Satellite focus. line disappears from the bottom of the image. Head- herringbone See Moire. switching interval is inherent in home video units. herringbone pattern An interference pattern some- head-switching noise A line of interference that oc- times seen on TV receiver screens, consisting of a hori- casionally appears at the bottom of a picture as a zontal band of closely spaced V- or S-shaped lines. result of video heads being switched on and off. A heterodyne The process of combining two signals of peculiarity chiefly inherent with helical scan VTRs, different frequencies so as to produce an output at such as U-Matic units, head-switching noise occurs the sum or difference frequency. The process is thus as a result of the different positions that each for- equivalent to nonlinear additive mixing or multipli- mat records information on tape. Since the problem cative mixing. The process is extensively used in is one of recording, not playback, these industrial sound and TV receivers where the received signal is recorders can be adjusted to produce invisible head- combined with the output of the local oscillator to switching. produce a difference term at the IF. Because the dif- head-to-tape contact In video, the extent to which ference frequency is above audibility this type of re- the magnetic coating surface of the videotape comes ceiver is known as a supersonic heterodyne, near the surface of the video heads during normal abbreviated to superheterodyne or superhet. operations of the VCR. High resolution and minimal heterodyne color process A technique that reduces separation loss occur with proper head-to-tape the color frequency from its normally high require- contact. ment of 3.58 MHz to the kHz range. Larger format head unit In microwave transmission, the collection video recorders have no problems processing the of apparatus housed in the head or unit fixed to the high color subcarrier that the color signal needs. The receiving or transmitting parabola or aerial. heterodyne process allows smaller format VCRs, such headwheel The rotating disc on which the video heads as the 1/2-inch type, to accept the reduced color are mounted. frequency which is boosted during playback to its height control The TV receiver control that adjusts original 3.58 MHz. Larger formats process the full picture height. color signal directly, which is required to meet the heliax A thick low-loss cable used at high frequencies; broadcast standards of the FCC, whereas smaller re- also known as hardline. corders process the color indirectly.

139 HF

HF High Frequency, 3-30 MHz. high band The TV band extending from 174 to 216 HFC Hybrid fiber coax. A type of network that con- MHz, which includes channels 7 to 13. tains both fiber-optic cables and copper coaxial high-band A description used for some camera pickup cables. The fiber-optic cables carry TV signals from tubes that denotes a very high frequency response. the head-end office to the neighborhood. The sig- high-band tape Videotape with superior resolution, nals are then converted to electrical signals and then or pictorial clarity, and of better quality than go to coaxial cables to the homes. low-band tape. HG A term given to high grade or premium quality high definition The TV equivalent of hi-fi, in which videotape. High grade actually refers to the quality the reproduced image contains such a large num- of a ferric-oxide particle used in the production of ber of accurately reproduced elements that the pic- this upgraded tape. According to some manufac- ture details approximate those of the original scene. turers, HG tape provides an improved signal-to-noise high-definition broadcasting The transmission of a ratio, which translates into a picture with less video broadcast signal that has much higher resolution noise, especially at slower tape speeds. In technical than the standard NTSC and PAL pictures. MPEG-2 jargon, the gain comes to about 3 dB. HG tapes is used to transmit the high-definition signal in the offer fewer overall dropouts. same bandwidth as a standard NTSC or PAL signal. HH CATV hyperband channel, 342-348 MHz. high-definition system—North America (HDS-NA). Hi8 A high-band 8mm video recording format that A DBS HDTV system. Uses a bandwidth compres- generates 400 lines of horizontal resolution, im- sion. In the US this system offers a 1080-line, 59.94- proves signal-to-noise ratio and permits up to 2 hours field interlaced DBS service in which no time-delay of broadcast-quality recording on one compact cas- of the detailed information is involved, so no dete- sette. The format of these VCRs and camcorders rioration of the display of moving objects occurs. raises the luminance carrier from 5 to 7 MHz and high-definition television (HDTV) A TV format hav- expands the frequency deviation from 1.2 to 2 MHz. ing approximately twice the number of scan lines as Hi8, equivalent in many areas to Super-VHS, fea- do 525-line NTSC system and 625-line PAL and tures separate S-video luminance and chrominance SECAM systems (the “conventional systems”) to im- inputs and outputs for excellent video quality with prove picture resolution and viewing quality. The total compatible components. The format also offers less number of luminance picture elements (pixels) in the generation loss when making duplicate tapes, im- image is therefore four times as great, and the wider proved color accuracy, flying erase heads for glitch- screen adds one quarter more. The increased verti- free edits and light-weight compact camcorders. cal definition is achieved by employing 720 or 1080 However, Hi8 tapes cost more, and the format is lines in the scanning pattern. In 1987, the U.S. FCC incompatible with most existing VCRs. established the Advisory Committee on Advanced Hi8 MovieBoy E1 Eye-controlled camcorder, having a Television Service to advise them on technical and tiny diode that shines IR light on an eye peeping public policy issues regarding advanced television. into the viewfinder; Canon. The pattern of reflec- After rounds of intense competitive testing and tions is caught by a sensor and analyzed to deter- evaluation of different systems proposed, the FCC mine where the eye is focused. The technology first in 1996 adopted the major elements of the ATSC controlled the in Canon’s EOS 5 still Digital Television (DTV) standard. The HDTV video camera. formats contained in that standard have been uni- Hi-band A standard recording format for still video formly adopted voluntarily by broadcasters and re- that allows resolutions of up to 500 horizontal TV ceiver manufacturers. HDTV equipment is currently lines from the original format of 360 lines. Special on the market and some HDTV broadcasts have com- recording heads and processing circuits are used to menced. See HDTV, ATSC. improve the luminance frequency response. high-definition VTR A professional/industrial VTR that H-identification Using the burst signal at the back makes use of a wideband 30-MHz luminance and porch of the line sync to recognize SECAM signals. 15-MHz chrominance recording system. HD VTRs can With H-identification, only the normal carrier signal record 1080 horizontal lines as produced by HDTV during the back porch is available for identification. color video cameras. In addition, the HD tape re- hi-fi A general term used to denote the capability of corders usually allow multi-generation recordings reasonably audio playback; an electronic with a 56-dB signal-to-noise ratio, provide internal system for reproducing sound with high fidelity. Hi- editing features and a built-in time code reader/ fi VCRs are equipped with separate rotating audio generator. heads (VHS), or they mix sound and picture in one high-density videotape Tape that packs a higher signal and record both simultaneously on tape (Beta). number of magnetic particles per square inch onto hi-fi tracking meter A VCR feature designed to maxi- the coating. Some high density tapes claim 230 mil- mize the tracking of tapes encoded with hi-fi lion particles per square mm. The greater the par- signals. ticle density, the better the video image.

140 high-speed search mode

high electron mobility transistor (HEMT) A type of plishes this by allowing passage of frequency com- gallium arsenide field-effect transistor. It is a low ponents above a predetermined limited frequency noise for satellite broadcast while rejecting components below that parameter. receiving amplifier. high-peaker In a TV camera, a circuit that equalizes high-electron-velocity camera tube Syn.: anode- the high-frequency response of a pickup device or voltage-stabilized camera tube. See Camera tube; sensor. Iconoscope. high power amplifier (HPA), satellite TV An amp high end The highest frequency portion of a video or used to amplify the uplink signal. audio signal; in audible audio signals, the high end high power satellite Satellite with transponder RF is the treble portion of the signal. power in excess of about 100 watts. high-end noise Any spurious noise occurring in the high power satellite TV Refers to DBS, which trans- high frequencies of a signal. mits its signals at 12.2 to 12.7 GHz within the Ku- high fidelity Fidelity of audio reproduction of such Band of the electromagnetic spectrum and uses high quality that listeners hear almost exactly what 18-inch antennas. High power satellite TV differs they would have heard if they had been present at from conventional satellite TV, which utilizes C-band, the original performance. Also called hi-fi. a 3.7–4.2 GHz low-power bandwidth and uses the high-fidelity video component An electronic unit large antenna dishes that range from 10 to 15 feet or part of a video system which is designed to re- in a diameter. Channels broadcast by DBS cannot produce a wider range of picture detail than ordi- be received by these large antenna systems. In 2002, nary video equipment. A major determinant in there are two Ku-Band DBS providers, DirecTV and producing hi-fi video is the frequency range—or Dish Network. Both offer more than 200 channels bandwidth—of the component. The wider the band- of digital quality picture and sound. width, the greater the image detail. A better-than- high priority See Advanced Digital Television. average broadcast signal extends over a bandwidth high-quality film-to-video transfer A very expen- of 4 million cycles per second, or 4 MHz. Since all sive transfer device that produces an outstanding TV receivers reproduce this range of frequencies, image. These devices are generally found in the picture resolution often suffers. Indeed, some me- major production centers, such as New York and diocre TV sets can barely cover a bandwidth of 2 . They will almost never be found in lo- MHz while hi-fi video units come very close to reach- cal TV stations. The most common of these high- ing the entire 4 MHz, producing excellent picture quality devices use a flying spot scanner. That means detail. that, rather than using a projector, they use a CRT high frequency boost Top boost. to illuminate the film. The only lens in the system is high gain In front projection TV systems, a specially between the CRT and the film. The electron beam designed screen that increases perceived brightness. scanning the blank CRT provides the illumination High gain helps to alleviate one of the drawbacks of that is first picked up by the beam splitter and is front projection TV, illumination loss. then divided into its component colors. This is a much high gamma See Gamma. more efficient way to transfer film to tape and gives high-gamma tube 1. A TV camera tube whose volt- excellent results. age output increases uniformly with the intensity of high resolution The display of a larger-than-usual the light on the image. 2. A TV picture tube whose number of scanning lines, perhaps 1,000 or more. light intensity on the screen is directly proportional In HDTV, the number of lines is typically 720 or 1080. to the control-grid voltage. Video cameras for home use often have an average high grade videotape See HG. of 240 horizontal lines. The higher the number, the high key Style of tonal rendering of a scene which better the detail, sharpness and definition. emphasizes the middle and lighter tones at the ex- High Resolution Sciences CCF System See CCF pense of the darker ones. Best suited to subjects system. that convey a light and cheerful impression. High high resolution TV TV with over 720 lines per screen, key lighting avoids strong shadows and makes use about double the resolution of present systems. Also of plentiful front light. called HDTV. See HDTV, high-definition television. highlight 1. An area of great brightness on a TV dis- high-speed picture search See Visual scan. play; a very bright portion of a picture. 2. Area of high-speed search mode A VCR feature that pre- excessive brilliance in a scene, which exceeds the sents the picture on screen while the tape moves permissible range of lighting contrast. rapidly to a desired point. This is made possible by high-pass filter 1. A filter that transmits all frequen- keeping the tape in contact with the video heads cies above a given cutoff frequency and substan- during the fast search. Conventional FF mode dis- tially attenuates all others. 2. In video, an electronic engages the tape from its contact with the video circuit that reduces interference on all channels. The heads. One shortcoming of this high-speed search filter, sometimes written as hi-pass filter, accom- mode is that the fast-moving tape, as it passes over

141 high-speed shutter

the heads, builds up friction and heat, both of which provider’s distribution facilities pass by in a given may be harmful to the tape and heads. The high- cable service area, and an expression of the market speed function can usually be adjusted from about potential of the area. 5 to 20 times on some machines and from 10 to 30 home theater The electronic buzz word of the 1990s. times on others in the standard playing speed. By linking a large-screen TV to video sources and a high-speed shutter A video camera feature that uses surround-sound system, a cinematic experience can electronics in the lens shutter to produce slow mo- be created in homes. Other essential components tion or freeze frame of action scenes without the in the home-theater setup include a VCR, a DVD usual blurring effect that accompanies subject mo- player, speakers, amps to power the speakers and a tion during playback of the tape. The high-speed surround-sound audio/video receiver. electronic shutter allows exposures as fast as 1/ home video A concept of home entertainment in 10,000 of a second to “stop” or freeze action. Most which a TV set is only one of the components and camcorders, however, provide shutter speeds of 1/ over which the viewer has some control. Home video 1000 or 1/2000 of a second, which should be suffi- provides the viewer with (1) controlled viewing (he cient for users to capture major sports activities. or she can slow down, speed up or stop the pro- high tension High voltage measured in thousands of gram with the functions on a VCR or VDP); (2) al- volts. tered programs (the viewer can edit, dub in a new high-velocity scanning See Scanning. audio track, etc.); (3) the capability of storing and high voltage Generally refers to the multithousand collecting material; and (4) the freedom to watch a picture tube voltage, but it can be used to mean program at any time other than the regularly sched- any potential of a few hundred volts or more. uled one. high-voltage probe A test instrument that will check home videotex The use of videotex in the home en- the anode and focus high voltage at the CRT. vironment. It can be helped by home computers. hi-pass filter High-pass filter. Early examples include such applications as TV games HIPPI High-performance parallel interface. A parallel and chess. data channel used in mainframe computers that hook A recognizable distortion at the top of the TV supports data transfer rates of 100 Mbps. picture which bends vertical lines sideways, causing hiss The continuous audio noise which emanates from them to look rather like a hook. Hooking can also tape playback on the upper end of the frequency occur at the originating source of the signal owing band. to a similar fault, or from phase modulation of the histogram An imaging term. A display plotting the TV signal. density of the various colors and/or values in an hook routine In DVI runtime software, a routine in- image. tended to be run at specific times during the execu- HiVision Analog HDTV system; Japan. The system tion of AVSS. broadcasts an analog signal, but uses digital hopping patch In a telecine (film scanner), to pro- technology everywhere else. duce an interlaced picture, the raster on the face of Hi-Z See Impedance. a flying spot tube can be displaced between alter- hold control In a TV receiver, the controls which de- nate fields, so that the film frame may be scanned termine the free-running frequency of the line and twice. Since the patch of light on the face of the field time bases. The controls are adjusted to bring tube changes position, it is called a hopping patch. the time-base frequencies into the range at which horizontal blanking During the horizontal blanking the time bases will lock at the frequencies of the interval, the video signal is at the blank level so as line and field synchronizing signals. Hence, the re- not to display the electron beam when it sweeps ceiver has two hold controls: line or horizontal hold, back from the right to the left side of the CRT screen. field or vertical hold. horizontal blanking interval The period of time when hold-down capacitor The hold-down or tuning ca- a scanning process is moving from the end of one pacitor is found from collector terminal of horizon- horizontal line to the start of the next line. tal output transistor to common ground. When this horizontal blanking pulse The rectangular pulse that capacitor opens or dries up, the high voltage will forms the pedestal of the composite TV signal be- increase, causing HV shut-down in TV chassis. tween active horizontal lines. This pulse causes the hold frame A single frame of a moving shot arrested beam current of the picture tube to be cut off dur- for as long as required. After the hold frame, the ing retrace. It is also called line-frequency blanking action is resumed. Also called freeze frame or stop pulse. frame. horizontal centering control The centering control holdover audience See Inherited audience. provided in a TV receiver to shift the position of the holography system One of the 3D-image display sys- entire image horizontally in either direction on the tems that doesn’t need the use of special glasses. screen. homes passed The number of dwellings that a CATV horizontal convergence control The control that

142 hot spot

adjusts the amplitude of the horizontal dynamic con- can also include a part of the second-anode power vergence voltage in a color TV receiver. supply for the picture tube. horizontal definition Horizontal resolution. horizontal output transformer (H.O.T.) A trans- horizontal deflection oscillator The oscillator that former in a TV receiver that provides the horizontal produces, under control of the horizontal synchro- deflection voltage, the high voltage for the second- nizing signals, the sawtooth voltage waveform that anode power supply of the picture tube, and the is amplified to feed the horizontal deflection coils filament voltage for the high-voltage rectifier. It is on the picture tube of a TV receiver. It is also called also called a flyback transformer and horizontal horizontal oscillator. sweep transformer. horizontal drive control The control in a TV receiver, horizontal polarization Property of electromagnetic sometimes at the rear of the set, which adjusts the wave in which the plane of polarization of the elec- output of the horizontal oscillator. Also called drive tric field is horizontal and the magnetic field is verti- control. cal. With this polarization, transmitting and receiving horizontal flyback Flyback of the electron beam of a dipole antennas are placed in a horizontal plane. TV picture tube that returns from the end of one The US TV system favors horizontal polarization, scanning line to the beginning of the next line. It is whereas the British TV system favors vertical also called horizontal retrace and line flyback. polarization. horizontal frequency Line frequency. horizontal resolution The number of individual pic- horizontal hold control The hold control that changes ture elements or dots that can be distinguished in the free-running period of the horizontal deflection a horizontal scanning line of a TV image. They are oscillator in a TV receiver so that the picture remains determined by observing the wedge of fine verti- steady in the horizontal direction. cal lines on a test pattern. Also called horizontal horizontal hum bar A wide stationary or moving strip, definition. usually occurring in a series, that appears on the TV horizontal retrace Horizontal flyback. screen. These alternating light and dark bars usually horizontal scan rate This is how fast the scanning are the result of interference at about 60 Hz or a beam in a display or a camera is swept from side to harmonic (multiple wave) of 60 Hz. side. In the NTSC system this rate is 15.734 kHz horizontal image delineation An electronic process (63.556 ms). designed to increase picture contrast and detail at horizontal sweep The sweep of the electron beam the edges of a TV screen. Horizontal image delinea- from left to right across the screen of a CRT. tion accomplishes this during the electron beam’s horizontal sweep transformer Horizontal output horizontal scanning across the screen. The signal level transformer. is immediately shortened prior to its reaching a dark- horizontal sync This is the portion of the video signal to-light boundary and instantaneously increased that tells the display where to place the image in before it reaches a light-to-dark border. Horizontal the left-to-right dimension. The horizontal sync pulse image delineation, sometimes listed as dynamic pic- tells the receiving system where the beginning of ture control or contour control, is similar in some the new scan line is. respects to delay line aperture control. horizontal synchronizing pulse The 5.08 (4.7 in the horizontal linearity control A linearity control that PAL system) microsecond rectangular pulse trans- permits narrowing or expanding the width of the mitted at the end of each line in a TV system to left-hand half of a TV receiver image to give linear- keep the receiver in line-by-line synchronism with ity in the horizontal direction so circular objects ap- the transmitter. It is called a line synchronizing pulse. pear as true circles. horizontal time base In a CRT, the circuits generat- horizontal line frequency Line frequency. ing the signals which give horizontal deflection of horizontal lines The TV lines that make up the pic- the beam. In TV, this is usually termed the line time ture height. The greater the number of lines, the base. See also Time base corrector, Time base insta- better the vertical resolution or sharpness and de- bility, Time base stability. tail. For NTSC, 480-486 lines of active video are al- H.O.T. Horizontal Output Transformer. ways present; for PAL, 576 lines are used. HDTV uses hot-pressed ferrite A video head (core) material: per- 720 or 1080 active lines. meability 300-500; resistivity 100,000 ohm/cm. The horizontal lock A method of stabilizing videotape play- use of this material in the VHS recorder helps im- back that tries to match a horizontal sync pulse of prove the characteristics of the heads. the playback signal to each horizontal sync pulse hot spot An area of intense heat or light, which pro- coming from the sync generator. See also Frame lock. duces a washed-out area on the camera pickup tube. horizontal oscillator Horizontal deflection oscillator. Some lights (such as common incandescent bulbs) horizontal output stage The TV receiver stage that produce uneven floods of light with some areas feeds the horizontal deflection coils of the picture brighter (hotter) than others; this results in hot spots tube through the horizontal output transformer. It appearing in the TV picture.

143 house drop house drop Cable drop. nipulate colors as opposed to the RGB space. For house sync This is another name for black burst. example, in the HSI space, if you want to change howl Positive feedback; in video, the wild swirling ef- red to pink, you simply decrease the saturation. If fect that results when a camera is pointed into a you want to change the color from purple to green, monitor displaying the picture that camera is pro- you adjust the hue. The key thing to remember, as ducing; in audio, any high-frequency feedback with all color spaces, is that it is simply a way to caused by a microphone being too near the speaker represent a color—nothing more, nothing less. reproducing the sound picked up by the mike. HSL A computer imaging term. A color model based howl round Natural frequency output or howl caused on hue, saturation, and luminance. Hue is the at- by a connection leading to a loop with greater than tribute that gives a color its name (e.g., red, blue, unity gain—i.e., positive feedback. Term originally yellow, or green). In this model, saturation refers to applied to sound and also called acoustic feedback, the strength, or purity, of the color. If you mix wa- but used for video also. When a camera sees its own tercolors, saturation would specify how much pig- picture in a monitor, part of the picture is likely to ment you added to a given amount of water. go above peak white and out of control, by the ef- Luminance identifies the brightness of a color. For fect of positive feedback. example, full luminance yields white, while no lumi- HP 89400 . The first commercial unit to nance yields black. See also HSV. characterize advanced-digital-TV signals; Hewlett- HSV A computer imaging term. A color model based Packard Co. The analyzer down-converts and digi- on hue, saturation, and value. Hue specifies the color, tizes input signals to 2.65 GHz. Built-in routines as in the HSL model. In this model, saturation speci- automatically extract carrier and symbol clock fre- fies the amount of black pigment added to or sub- quencies, synthesize user-specified baseband filter- tracted from the hue. Value identifies the addition ing and display the recovered data and waveforms. or subtraction of white pigment from the hue. The demodulator can be key-stroke-configured for HSYNC See horizontal sync. the 16-, 32-, 64-, 256-QAM formats employed in HT High Tension. US and European cable systems. Also handled are hub The hole in the middle of a reel of magnetic tape, the 8VSB (broadcast) and 16VSB (cable) formats pro- which fits over the capstan when the reel is mounted posed by the Grand Alliance. Part of the HP 89400 on a tape deck. vector-signal-analyzer family, the AYH option allows hue The “color” of a colored point, as red, green, the analyzer to characterize digital RF modulation. yellow, violet. In technical terms, hue refers to the The tool verifies that the high-speed data streams wavelength of the color. The term is used for the containing the digital video have been transferred base color—red, green, yellow, etc. Hue is completely accurately onto the RF transport carriers. separate from the intensity or the saturation of the HPA High Power Amplifier. color. For example, a red hue could look brown at HQ High Quality. A technology developed by JVC for low saturation, bright red at a higher level of satu- VHS VCRs. It is a collection of video signal-enhance- ration, or pink at a high brightness level. All three ment circuits that operate separately on various parts “colors” have the same hue. Also called color phase of the signal. The HQ circuits are designed to re- or tint. duce luminance- and chrominance-signal noise (and hue control (for NTSC decoder) An adjustment that thereby reduce “snow” or graininess), and color is obtained by changing the phase of the input sig- patching and streaking, respectively. White-clip level nal of the burst phase detector with respect to the inadequacies are also reduced with a consequent chrominance signal applied to the demodulators. improvement in image-edge sharpness. Because dif- Also called tint control. Sometimes confusingly called ferent HQ circuits operate during recording and play- color control. back, some of the improved quality of HQ-recorded Huffman coding A popular lossless data compres- tapes will show up during playback on non-HQ sion algorithm that replaces frequently occurring machine will also be improved, but to a lesser data strings with shorter codes. Some implementa- degree. tions include tables that predetermine what codes hr Hour. Also h. will be generated for a particular string. Other ver- HRC Harmonic Related Carrier. sions of the algorithm build the code table from the hrs Hours. data stream during processing. Huffman coding is HSI Hue, Saturation, Intensity. A color space used to often used in image compression. In general, it represent images. HSI is based on polar coordinates, doesn’t matter what the data is—it could be image while the RGB color space is based on a 3D Carte- data, audio data, etc. It just so happens that Huffman sian coordinate system. The intensity, analogous to coding is one of the techniques used in JPEG, MPEG, luminance, is the vertical axis of the polar system. H.261, and H.263 to help with the compression. This The hue is the angle and the saturation is the dis- is how it works. First, take a look at the data that tance out from the axis. HSI is more intuitive to ma- needs to be compressed and create a table that lists

144 hypertext

how many times each piece of unique data occurs. cial signals in each field blanking period to recog- Now assign a very small code word to the piece of nize SECAM signals. data that occurs most frequently. The next largest HVQ Hierarchical Vector Quantization. A method of code word is assigned to the piece of data that oc- video compression introduced by PictureTel in curs next most frequently. This continues until all of 1988 which reduced the bandwidth necessary to the unique pieces of data are assigned unique code transmit acceptable color video picture quality to words of varying lengths. The idea is that data that 112 Kbps. occurs most frequently is assigned a small code word, hyperband Those frequencies located immediately and data that rarely occurs is assigned a long code above the superband channels. At 300 to 402 MHz, word, resulting in space savings. the hyperband range covers channels W+1 to W+17 hum Audio noise in the low frequency range. Hum and is reserved for such special services as aero navi- can result from the AGC of a VCR or TV. It is simply gation, the Coast Guard, etc. Other ranges include picking up and amplifying extraneous sound. Hum subband, midband and superband CATV. can also stem from faulty “ground” connections, hypermedia 1. A way of delivering information that from defective internal mics on a camera, etc. provides multiple connected pathways through a hum bar A form of interference seen as dark or light body of information. Hypermedia allows the user to lines on the screen of a TV receiver due to compo- jump easily from one topic to related or supplemen- nents at mains frequency (50 or 60 Hz) in the DC tary material found in various forms, such as text, supply circuits. Usually produced by poor smooth- graphics, audio, or video. 2. Nonlinear media, of ing of the high-tension supply and is 50 (60) Hz in which multimedia can be a form. Just as hypertext the case of half-wave rectification and 100 (120) Hz is a non-sequential, random-access arrangement of for full wave rectification. Also called video hum. text, hypermedia is a non-sequential, random-ac- hum displacement Cyclic positional shift in a CRT cess arrangement of multiple media such as video, picture display, normally at mains frequency. When sound, and computer data. 3. Hypermedia is a type mains-locked, the picture suffers distortion of verti- of authoring and playback software through which cal lines; when unlocked, it acquires a disturbing you can access multiple layers of multimedia infor- wobble. mation related to a specific topic. The information humidity eliminator unit A built-in feature found can be in the form of text, graphics, images, audio, on some VCRs and videocassette players designed or video. For example, suppose you received a to keep metal surfaces dry when humidity is high. hypermedia document about the Sun file system. Problems arise when the location of a machine is You could click on a hotspot (such as the words “file changed from a cold environment to a warm one. system”) and then read a description. You could then In this situation, the dew indicator will light and click an icon to see an illustration of a file structure, the machine will not function as a safety precau- and then click the file icon to see and hear informa- tion. The user must wait for the dew light to go off tion in a video explaining the file system. before playing or recording. This type of device hypertext Also called hypermedia; software that al- helps to prevent damage to the videotape. See Dew lows users to explore and create their own paths indicator. through written, visual, and audio information. Ca- H.V. Home Video. pabilities include being able to jump from topic to (H+V)-identification Using the burst signal during the topic at any time and follow cross-reference easily. back porch of the line blanking period and the spe- Hypertext is often used for Help files.

145 I

I 1. CATV midband channel, 168-174 MHz. 2. TV stan- charge image is discharged by the scanning beam dard; Hong Kong, , UK. Characteristics: and the resulting voltage change is transferred to 625 lines/frame, 50 fields/s, interlace-2:1, 25 fr/s, the signal plate via the capacitive coupling to the 15,625 lines/s, aspect ratio-4:3, video band-5.5 MHz, mosaic. In spite of the charge storage thus achieved, RF band-8 MHz, visual polarity-negative, sound the tube is not very sensitive and requires high scene modulation-F3, pre-emphasis-50 µs, deviation- illumination for a satisfactory signal-to-noise ratio. 50 kHz, gamma of picture signal-0.5. Moreover, secondary emission from the target as a I2C bus A two-line, multi-master bus developed by result of bombardment by the high-velocity scan- Philips to provide cost-effective control of analog and ning beam results in spurious signals in the tube digital functions among ICs. I2C can simplify the output that produce undesirable shading effects in manufacturing process by enabling complete cali- reproduced images. These effects are minimized by bration and test under computer control. Many com- mixing with the tube output, sawtooth and parabolic panies offer a large family of I2C-capable ICs, waveforms at line and field frequencies. One example including microcontrollers, microprocessors, and au- of an iconoscope is the standard emitron tube. dio, video, and telephony Ics. ideal bunching A theoretical condition in the bunch- IARC Internal Anti-Reflective Coating. ing of electrons in a velocity-modulation tube. All IAV In (2+3)D-image display systems, data indicative electrons in a bunch would have the same velocity of an analog image signal from a TV camera unit. and phase, corresponding to an infinitely large IBO Integrated Broadcast Operation. current peak. IBM Power Visualization System (PVS) A computer I demodulator The demodulator whose chrominance that merges high-resolution color displays and ani- signal and the color-burst oscillator signal are com- mation with supercomputer-based simulation. The bined to recover the I signal in a color TV set.

parallelized, multiuser visualization supercomputer identification frequency blue fId-B = 3,900.000 kHz, permits scientists to gain insights into complex prob- vertical identification (SECAM). It is also the mini- lems by presenting them in 2- or 3-dimensional mum frequency of the color signals.

visual formats. identification frequency red fId-R = 4,756.000 kHz, I channel The 1.5-MHz-wide channel used in the vertical identification (SECAM). It is also the maxi- American (NTSC) color TV system for transmitting mum frequency of the color signals. cyan-orange color information. The signals in this identification hole In Super-VHS cassette, a hole at channel are known as I signals. the bottom that functions to place the recorder in icon In desktop computing and editing, a graphic sym- the S-VHS mode. In this manner, it will record and bol that represents a file, a tool, or a function. play S-VHS tapes and will also accept standard VHS iconoscope The earliest (1923; no longer used) form tapes for record or playback. of TV camera tube in which the optical image of the identification signal Field identification signal. scene to be televised is focused on a photoemissive idiot box Derogatory slang for TV. target mosaic that is obliquely scanned by a high- idiot card Cue card. velocity electron beam. The mosaic is deposited on idiot sheet Cue card. the face of a mica sheet that is backed by a conduc- idler A wheel most often used to drive the supply and tive signal plate from which the output of the tube take-up tape reel spindles. The idler is powered by a is taken. When the optical image is focused on the separate motor (rarely) or driven by a belt connected mosaic, photo-electrons are released from each ele- to the capstan motor. ment in proportion to the light falling on it. Thus, a IDTV Improved-Definition TV. positive charge image is built up on the mosaic sur- IDV In (2+3)D-image display systems, data indicative face and this grows with time as the capacitance of the display of a digital signal from the storage between element and signal plate is charged. The unit.

146 image compression

IEC 461 Defines the longitudinal (LTC) and vertical in- IHVT The integrated horizontal or high-voltage out- terval (VITC) timecode for NTSC and PAL video sys- put transformer that has HV diodes and capacitors tems. LTC requires an entire field time to store molded inside the flyback winding area. IHVT trans- timecode information, using a separate track. VITC formers may also provide several different voltage uses one scan line each field during the vertical blank- sources for the TV circuits. ing interval. II CATV hyperband channel, 348-354 MHz. IEC 60461 Defines the longitudinal (LTC) and vertical iLink Sony’s name for their IEEE 1394 interface. interval (VITC) timecode for NTSC and PAL video sys- illegal color Any color that is too saturated for the tems. LTC requires an entire field time to transfer limited color range of video. Computer monitors timecode information, using a separate track. VITC versus video monitors are capable of showing more uses one scan line each field during the vertical blank- colors at one time. To fit within the required band- ing interval. Also see SMPTE 12M. width for broadcasting, RGB signals that are encoded IEC 60958 Defines a serial digital audio interface for into the video signal have a limited range of colors. consumer (SPDIF) and professional applications. For example, highly saturated colors on a computer IEC 61834 Defines the DV (originally the “Blue Book”) screen, such as bright red or green, are considered standard. Also see SMPTE 314M. illegal colors in video. IEC 61880 Defines the widescreen signaling (WSS) in- illegal video Some colors that exist in the RGB color formation for NTSC video signals. WSS may be space can’t be represented in the video domain. present on lines 20 and 283. For example, 100% saturated red in RGB space IEC 61883 Defines the methods for transferring data, (which is the red color on full strength and the blue audio, DV and MPEG-2 data over IEEE 1394. and green colors turned off) can’t exist in the NTSC IEC 62107 Defines the Super VideoCD standard. video signal, due to color bandwidth limitations. IEEE Institute of Electrical and Electronic Engineers. The NTSC encoder must be able to determine that IEEE 1394 (FireWire) A low-cost digital interface origi- an illegal color is being generated and stop that nated by Apple Computer as a desktop LAN and from occurring, since it may cause over-saturation developed by the IEEE 1394 working group. Can and blooming. transport data at up to 1.6 Gps. One of the solu- illuminance A measure of the illumination of a scene— tions to connect digital television devices together e.g., a TV studio set—by external light source. Care at 400 Mbps. In addition to an architecture that should be exercised to avoid confusing luminance scales with silicon technology, IEEE 1394 features a and illuminance. Luminance is a measure of the unique isochronous data channel interface. Isoch- brightness of an area of an image. ronous data channels provide guaranteed bandwidth illuminant C The reference white of color TV. It closely for data transport at a pre-determined rate. This is matches average daylight. especially important for time-critical multimedia data image 1. The scene reproduced by a TV receiver. 2. A where just-in-time delivery eliminates the need for still picture, or one frame of a motion sequence. costly buffering. image archiving Refers to electronically storing video IEEE scale A waveform monitor scale in keeping with images, frames or stills for future reference or use. other IEEE standards and recommendations of video image buffer Electronic circuitry capable of modify- broadcasters and manufacturers. ing a 625-line 50-Hz video signal to the 525-line IF . Most TV receivers have the 60-Hz standard (or the reverse). following IFs: 38 MHz (SECAM), 38.9 MHz (PAL), image burn A temporary loss of picture in an isolated 47.75 MHz (NTSC), 70 MHz (satellite TV)—for a TV area of the TV image caused by bright lights or re- receiver picture channel; 6.5 (SECAM), 5.5 (PAL), 4.5 flection; also, possible permanent damage to the MHz (NTSC)—for a TV receiver sound channel. as a result of excessive exposure IF amplifier That component of a TV receiver that to bright lights such as the sun or studio lighting strengthens the RF carrier signal fed to it. The signal units. All cameras using vacuum-type tubes are sus- is a combination of the audio and video signals that ceptible to image burn. the IF amplifier increases before it is sent to a video image compression Image compression is used to detector for separation. reduce the amount of memory required to store an IF harmonic interference Interference due to accep- image. For example, an image that has a resolution tance of harmonics of an IF signal by RF circuits in a of 640 x 480 and is in the RGB color space at 8 bits superheterodyne receiver. per color, requiring 900 KB of storage. If this image I frames One of the three types of frames used in can be compressed at a compression ratio of 20:1, MPEG coded signals. These contain data to construct then the amount of storage required is only 45 KB. a whole picture as they are composed of informa- There are several methods of image compression, tion from only one frame (intraframe). The original but the most popular are JPEG and MPEG. H.261 information is compressed using DCT. See also B and H.263 are the video compression standards used frames, P frames, MPEG. for video conferencing.

147 image detail image detail The amount of information and sharp- image. However, the final results of most enhancers ness displayed on a TV screen. With VCRs, image are often subjective. Some VCRs feature a built-in detail can be measured by its response to a 2-MHz enhancer, a control dial or knob simply called signal. Some machines may lose as much as 4 dB of Picture. the video signal while other models give up as little image file A file of data that represents an image. as 0.13 dB at the 2-MHz frequency. Often, image image frequency In superheterodyne reception, a fre- detail is subjective, although manufacturers keep quency as much above (or below) the oscillator fre- coming up with various techniques and electronic quency as the wanted signal frequency is below (or circuitry, including filters and digital video noise re- above) it and that is therefore accepted with the duction systems, to improve it. wanted signal by the IF amp so causing interference. image detailer See Image enhancer. image iconoscope An early form of TV camera tube image diagonal Measurement taken across opposite consisting of an iconoscope with an image section. corners of the optical image formed on the face- image interference In superheterodyne reception, in- plate of a camera or receiver tube. terference from signals on the image frequency. The image dissector An early (invented in 1927 by Philo frequency of such interfering signals differs from that Farnsworth, no longer used) TV camera tube that of the wanted signal by twice the intermediate fre- focuses the scene to be transmitted on a light-sen- quency and, to minimize image interference, the sig- sitive surface; each point emits electrons in propor- nal-frequency circuits of a superheterodyne receiver tion to incident light. The resulting broad beam of are designed to give great attenuation at the image electrons is drawn down the tube by a positive an- frequency. ode. Magnetic fields produced by coils keep the elec- image isocon A camera tube similar to an image or- tron image in focus as they sweep it in a scanning thicon but responsive to much lower light levels, in- motion past an aperture opening into an electron cluding near darkness. multiplier. The output voltage of the electron multi- image jitter See Jitter. plier is proportional at each instant to the bright- image lag See Image retention. ness of an elemental area of the scene being scanned image mix A digital camcorder function that creates in orderly sequence. It is also called a dissector tube. a variety of effects by joining live recorded images image enhancement 1. Any improvement of detail, with a stored still picture. The combinations made sharpness, color accuracy or reduction of video noise by the image mix feature produce a series of special in a TV screen picture. Several techniques have been effects, such as simulated dissolves, split-screens or developed to enhance the screen image, or defini- PIP. tion, including HQ circuitry, digital effects, special image orientation For special effects purposes, the comb filters, line-doubling and non-interlaced dis- TV image can be rotated about its center. play. Some processes involve increasing the number image orthicon A low-electron velocity orthicon TV of horizontal lines. Others use special electronic cir- camera tube with an image section and in which cuitry to reduce video noise. 2. A method of im- the output signal is obtained from an electron mul- proving color TV pictures by comparing each video tiplier into which the return scanning beam is di- line, element by element, with the preceding and rected. An optical image of the scene to be televised following lines. Any differences between vertically is focused on the photo-cathode, and photo-elec- aligned elements are added to the middle-line ele- trons so released are focused by a combination of ment in the proper phase to enhance picture out- electrostatic and magnetic electron lenses on the lines and contrast. image-section face of the target where they give image enhancer 1. A device that improves the sharp- rise to secondary emission that is collected by the ness of a video image by adding dark lines around nearby positively charged mesh. Thus, a positive the edges of objects and figures in the scene. 2. A charge image is established on the face of the tar- signal processing device designed to restore some get. If the tube is directed at a very bright light, caus- of the detail that is lost when duplicating a video ing the target potential to exceed that of the mesh, image. An enhancer operates by increasing or cut- the excess secondary electrons are returned to the ting the highest video frequencies. Since this can target; in this way the mesh keeps the tube stable also increase noise, the unit often has a Response for all light inputs. The target is very thin and the control to restrict this interference. Like most pro- charge image is rapidly transferred to the opposite cessors, the enhancer works only with a video sig- face that is scanned by the low-velocity beam. The nal, not with RF signals such as those broadcast beam lands on the target to neutralize the positive directly to the TV receiver. The unit can be connected charge image and thus the return scanning beam is between two VCRs as when making a copy of a amplitude modulated by the required picture sig- tape or between a video camera and a VCR. Some nal. The return beam is directed into the input of a enhancers have a selector dial that permits a com- multi-stage electron multiplier that surrounds the parison between the enhanced and unenhanced electron gun. The tube is extremely sensitive and is

148 image smear

capable of high-quality pictures. It is, however, com- taining to color requires both luminance and chromi- plex and too bulky (typically 15" long and 3" or nance reversal. Some high-priced video cameras are 4.5" in diameter) to be used in color cameras where capable of performing both of these reversal pro- three or four tubes are necessary. Image orthicon cesses by way of a negative/positive image switch. developed prior to the vidicon, the first really reli- A device, supplied with some VCRs, able and sensitive camera pickup tube. See Orthi- designed to “read” text or a drawing and then su- con, Persuader. perimpose it over a video image. The scanned im- image pickup device Image sensor. age can be copied in different colors and sizes. image pickup tube Camera tube. image section An electron-optical stage included in image plane 1. In digital video, display hardware that some TV camera tubes to increase sensitivity. The has more than one video memory array contribut- optical image is focused on the photo-cathode in ing to the displayed image in real time, each memory the image stage and the liberated photo-electrons array is called an image plane. See also Bit plane. 2. are focused on the target to form a charge image The point behind the lens on which the image col- by secondary emission from the target. The use of lected by the lens is cast. 3. The surface of the video an image section thus separates the functions of tube target area. photo-emission (now carried out by the photo-cath- image processing 1. Techniques that manipulate the ode) and secondary emission (carried out by the tar- pixel values of an image for some particular pur- get). In the iconoscope the target is required to carry pose. Examples are: brightness or contrast correc- out both functions. tion, color correction, changing shape of the image image sensor The image pickup device used in a video (warping). 2. The use of computers and mathemati- camera to capture the picture. The design may be a cal algorithms to analyze, enhance, and interpret CCD or MOS, both of which have virtually replaced digitized TV images. the conventional image pickup tube. The MOS chip image processor Special circuitry, usually found in is a 3/4" square solid-state sensor containing nu- higher-priced TV sets or TV monitor/receivers, de- merous rows of light-sensing cells upon which the signed to retain natural colors while continuously camera lens projects its image. The black and white adjusting the light and dark values of each scene. and color patterns of the image activate electrical The image-processing circuits constantly modify the impulses within each cell that are then generated dynamic range of the CRT to correspond to the light- into a video signal. Although more costly than stan- to-dark values of consecutive scenes. The image pro- dard camera tubes, image sensors are not only cessor is also a general term for one of the many smaller and lighter, but they minimize image burn “black boxes” or devices available that can be con- and image retention. Some professional camcorder nected to a VCR, such as an image stabilizer, image image sensors are composed of two CCDs—one for enhancer and fader. Some of the more recent im- brightness and the other for color. The two signals age or video processors can accommodate both S- are processed separately to produce better resolu- VHS and Hi8 video signals, offer several audio fade tion and color. Still other, more costly professional/ controls and provide a power distribution amp that industrial components feature an image sensor that permits the user to duplicate several copies of a vid- utilizes three CCDs, one for each of the primary eotape simultaneously with little or no loss of signal colors. strength. image sharpness In video, a subjective measurement imager A device that converts an optical image into of the amount of detail in a TV screen image. Image an electrical signal. Imagers were originally vacuum sharpness depends upon such factors as resolution tubes—image orthicons, vidicons, and plumbicons— (picture detail as measured by the number of hori- but more recently tubes are being supplanted by zontal lines), contrast (the relationship between the solid-state sensors such as charge-coupled devices white and dark portions of an image) and the (CCDs). amount of video noise (unwanted signal interfer- image retention Unwanted lagging or trailing of pre- ence) present in the screen image. Many TV sets, vious images or pictures. This effect is usually caused VCRs, monitors and monitor/receivers have a sharp- by rapid movements of the subject, quick panning ness control feature designed to reduce noise and of the video camera or the quality of the camera minimize contrast. The control, however, does not tube. The anomaly often occurs more frequently basically alter the resolution or number of horizon- during low lighting sequences. The term is often con- tal lines in the image. fused with burn or image burn. Also known as im- image shift A digital TV or VCR feature that allows age lag or cometing. the viewer to exchange the main image and the in- image reversal A process of reversing black and white set image of the PIP function. Part of the digital ef- images (dark-to-light, light-to-dark) and inverting fects process, shift permits swapping pictures while color images. The conversion of black and white retaining the audio with the main screen image. images is called luminance reversal while that per- image smear Image burn.

149 image stabilization image stabilization The elimination of jitter and ver- the cathode into a beam. Because these electrons tical rolling of the screen picture. Some Super-VHS have very low velocities the lens is situated very close camcorders have developed techniques to improve to the cathode, so close in fact that the cathode image stabilization. They include electronic and me- may be regarded as immersed in the lens. The lens chanical improvements. Additional electronic correc- usually consists of two plates containing apertures tion circuitry ensures stable pictures at all camera and that may have cylindrical extensions. speeds while changes in the way tape is transported impedance The resistance characteristics of any elec- across the video head drum rectify some types of tronic circuit. The connection of one electronic com- instability. ponent to another requires matching their image stabilizer A device designed to override some impedances. Video games, VCRs and other units anti-piracy signals of prerecorded tapes and restore must have the same impedance level as the TV set. the stability of the signal to the TV image. The elec- Impedance is measured in ohms—a standard unit tronic coding, deliberately placed on tapes to pre- of electronic resistance. Video involves only two rat- vent their being copied, changes and weakens the ings—75 and 300 ohms. An impedance adapter, vertical sync signal so that when it is fed into a VCR, such as a balun or small transformer, is used to con- the machine cannot usually lock onto it. The stabi- vert 300 ohms to 75. Audio units such as speakers, lizer, therefore, either re-forms the vertical sync pulses when working as a set, should have matched im- or corrects any altered horizontal sync pulses. Some pedances, usually 4 or 8 ohms. High and low im- models completely strip the vertical blanking signal pedances are expressed as hi-Z and low-Z. (which contains the anti-copying white pulses) and impedance adapter A device that matches up the then proceed to re-build the sync signals to broad- output of one unit with the input of another. For cast standards. Without a stabilizer, the picture of- example, to connect the audio from a TV set (one ten rolls and breaks up. However, most late model that has an earphone jack, for instance) to the “aux” VCRs have advanced circuitry that defeats this sig- input of a stereo system, one should purchase the nal without the use of this device. Some image sta- appropriate impedance adapter. This will depend bilizers have different features, such as loop-through upon the input of the stereo amplifier. Although the outputs, lock control signal lights and switchable connection will work without the adapter, the sound inputs. Other models, such as the copy-protection will appear distorted. Also known as matching removers, or digital video stabilizers, use digital fil- transformer. ters in their process. impedance matching Back matching. image swap A feature, found on TV receivers equipped impedance roller Metal or plastic rollers used in most with PIP and split screen capability, that allows the VCRs to provide an even and steady flow of tape viewer to exchange left and right pictures or main through the transport mechanism. and inset images. implosion The inward collapse of an evacuated con- image transceiver An accessory unit, used in con- tainer, such as the glass envelope of a CRT. junction with still video cameras, that permits color improved-definition systems See System photos to be transmitted by way of ordinary tele- terminology. phone lines. Some image transceivers accept a still improved-definition TV (IDTV) TV that includes im- video floppy disk (VF), that is used in still cameras. provements to the standard NTSC TV system, which However, the loss of image quality produced by this improvements remain within the general parameters procedure limits its usefulness for professional/in- of NTSC TV emission standards. These improvements dustrial purposes despite its several conveniences. may be made at the transmitter and/or receiver and image transfer converter Picture standards converter may include enhancements in parameters such as that displays a picture image at one standard on a encoding, digital filtering, scan interpolation, inter- suitable monitor and re-photographs it at another laced scan lines, and ghost cancellation. Such im- standard with a TV camera. provements must permit the signal to be transmitted image transform Proprietary computerized HQ vid- and received in the historical 4:3 aspect ratio. Syn.: eotape-to-film transfer system. (in CCITT usage) enhanced-quality TV. See Advanced image translator A conversion kit or VCR designed television, System terminology. to modify some VHS recorders, using the standard impulse pay-per-view (IPPV) It is a feature of a de- NTSC, to accept European PAL-recorded 625-line coder that allows an authorized subscriber to pur- color tapes. Developed by Instant Replay, the VCR chase a one-time scrambled program at will. plays back the North American conventional 525- impulsive noise Undesired signal on a video system line color tapes as well as PAL and SECAM tapes. that consists of a series of pulses Instant Replay claims that their VHS VCR can play in-betweens Jargon term to designate frames com- and record in 16 world standards. puted by a computer animation workstation or DVE immersion lens In a CRT, an electrostatic electron lens to fill the time intervals between actual defined or designed to concentrate the electrons liberated from selected keyframes. In the case of a DVE, trajectory

150 information superhighway

settings are used to enable the calculation of in- recording whereas VASS (VHS Address Search Sys- betweens. Syn.: tweens. tem) permits marking scenes during playback. See in-camera recording system A unit in which the video also Program start locator. camera houses the recording components so that a indirect scanning Scanning in which a narrow beam separate VCR/VTR becomes unnecessary. See of light is moved across the area being televised. Camcorder. Indirect scanning was employed in early TV, which incandescence The emission of visible light from a sub- was heavily dependent on mechanics. It is currently stance at a high temperature. The term is also used used in flying-spot scanning of films where the light to describe the radiation itself. Syn.: luminescence. transmitted by each illuminated elemental area is increment A small change in the value of a variable. picked up in turn by one or more phototubes. incremental tuner A TV tuner with its antenna, RF industrial VCR A video cassette recorder (VCR) that is amp, and RF oscillator tuning coils continuous or in externally similar to a home VCR, but is different in small sections connected in series. Rotary switches many ways. An industrial machine, whether a 3/4" make connections to the required portions of the U-Matic model or a 1/2" Beta or VHS deck, usually total inductance necessary for a given channel, or has a rectangular multi-pin jack for use with a TV short-circuit all of an inductance except that required monitor. The machine often plays at only one speed for a given channel. (the fastest) to retain high image resolution. It has Indeo® video Originally called DVI (Digital Video In- special features such as random access and auto- teractive), this is a digital video recording and play- matic transition editing. Many of these features, with ing format created by Intel, using a lossy modifications, eventually find their way into home compression/decompression algorithm. It turns a PC VCRs. The costlier industrial machines are more stur- into a video recorder and player. It uses a card or dily built for heavier duty and are used more in busi- special electronics inside a PC to turn the incoming ness and institutional environments than in homes. NTSC analog video into digital signals, which it then infill In TV, to change tone or color, a common proce- compresses in real time and stores on the computer’s dure done electronically. hard disc. A one-minute small-screen video file is infinity An indefinitely large number or an unbounded typically 50 megabytes. But Indeo video reduces this space. In photography, objects at a few hundred feet 50 megabytes to a much smaller size. Indeo is simi- are considered to be at infinity; in TV, the camera lar to motion JPEG. The Indeo algorithm was used setting for infinity may be at 74 feet. by Microsoft in its Video for Windows, IBM in their infomercial A video segment or program purporting OS/2 and Apple in their QuickTime. to be informational/newsy and educational, but, in index counter A VCR feature with three or four digits fact, the segment is a commercial paid for by the that rotate with the motion of the tape. The odom- company whose products and/or services are fea- eter-type mechanical counter, now all but defunct, tured. helped to locate different portions of tape once the information provider An organization that provides numbers were noted down. The numbers are arbi- information for storage on a view database. Typi- trary, representing neither inches nor time, simply cally, information providers are companies that rent registering rotation. A counter on one machine, in space on the public utility system that can be called fact, may not match that of another. VCR owners up by videotex subscribers and for which a charge is whose machines had mechanical index counters made by the organization running the videotex ser- often had to compose their own reference charts, vice. After deduction of operating costs, the result- with a list of numbers and matching times; i.e., ev- ing revenue is passed on to the information providers ery five digits equaled 15 or 30 minutes. Today, vir- concerned. tually all VCRs have electronic counters or read-outs, information superhighway A vague concept that many of which measure real time. Senator Al Gore may have created in the early 1990s, index mark Cue mark. that gained great popularity when he became vice index search A VCR feature that helps the viewer president, and the Clinton/Gore administration find the beginning of a program automatically and started pushing the term. It can refer to a gigantic quickly. With the index search method, also known Internet reaching everybody in North America or the as VISS or VHS Index Search System, an electronic entire world. It can just as easily mean a combina- mark is automatically placed on the videotape each tion 500-channel interactive cable TV system with time the Record mode is activated. Later, the viewer full to every household in North engages the index search to find the beginning of America. Somewhere in all this is the idea that easy each program until the right one is found. Some access to large amounts of information will enrich machines can mark up to 19 indexes. Index search, our lives immeasurably. Who’s going to get first ac- which differs from the more sophisticated intro cess to it all, what the precise technical details will search, can be performed manually as well. How- be, and who’s going to pay for it are, naturally, mi- ever, the VISS system performs indexing only during nor details to be worked out.

151 infotainment infotainment A combination of information and en- gun produces three similarly positioned electron tertainment, such as that provided by some of the beams. videotex and CATV services. in-line switching The special circuitry in VCRs that See IR. automatically disconnects the tuner signal during the infrared remote control On video cameras, a feature copying process. This entails duplicating by means that starts and stops the camera recording and con- of audio/video cables hooked up to the VCR. trols the zoom lens. This allows the camera user to INMARSAT INternational MARitime SATellite organi- set up his equipment and operate it from a limited zation. Uses Marisat, MARECS, and Intelsat V MCS distance without his direct presence affecting the satellites. subject. This is a useful feature in capturing shots of in-phase In NTSC video, refers to being at 0 degrees animals in the field or children at home or in a stu- with respect to the color subcarrier. dio, subjects that sometimes appear shy before a input level For ADCs, the input level is the voltage camera. Also used on most other consumer devices, range required of the input for proper operation of such as TVs, DVD players, etc., to allow remote con- the part. For example, if the required input level for trol of their operation. an 8-bit ADC is 0 to 10 V, then an input voltage infrared sensor An element on TV receivers and VCRs level of 0 V is assigned the code 0 and an input and other equipment that permits wireless remote voltage level of 10 V is assigned the code 255. control to operate various functions from a limited in-room video A TV service in hotel guest rooms, in- distance. This feature is sometimes called remote cluding pay-per-view movies and free programming. control receiver. insert A general term used in special effects in which infrared transmitter See Remote control, Remote a secondary signal is introduced into an already ex- control panel. isting, primary image. The insert can be made to inherited audience The segment of the audience of appear in any portion of the TV screen. Accomplished a radio or TV program that stays tuned and is car- by keying, wiping or crossfeeding. ried over to the next program; also called holdover insert edit The insertion of a segment into an already audience. The inheriting program thus benefits from recorded series of segments on a videotape; the in- the preceding program. serted segment replaces one that must be the same in-house system A videotex system operated by a length. Insert edits demand that the segment be cut single information provider (IP) on which to display in precisely, since already recorded information ex- his own text, data, and images. (Nothing prevents ists following the insert edit on the original tape. the IP from also renting space on his in-house sys- insertion loss Signal loss caused by such items as tem.) An in-house system can be supported in one cables, connectors, baluns and splitters that connect location or, in long haul, by leased or public tele- to or pass through the RF switcher. Insertion loss is phone lines. expressed in dB. The lower the dB number, the bet- injection laser Another name for a semiconductor or ter the signal. Insertion loss is usually corrected by diode laser. adding an amplifier. injection locking Low-cost technique for phase-lock- insertion signal In TV, a signal inserted into one of ing a cavity or resonator oscillator to a crystal source, the line periods during the field blanking period. The to improve its frequency stability. signal is not seen on the screens of viewers’ receiv- INL Integral nonlinearity. ers and is used by the transmitting authority to trans- inlay 1. Mortise-keyed insert; static matte insert. An mit information such as the source of program or insertion effect in which the fill signal is static and control data. The signal is also used for test pur- of a predetermined shape. Cf. overlay. 2. Keying poses to give information on the performance of mode when a key signal of the mixer (e.g., a dia- the TV links. mond-shaped wipe pattern) comes from a source insert set Detail set. other than the video that will eventually fill the hole. insert stage Small studio for minor tabletop or closeup The key source, in this case, may be either internal videotaping. or external. Syn.: zonal mixing. instant-on switch A switch that applies a reduced in-line coaxial amplifier An amp to boost the signal filament voltage to all tubes in a TV set continu- when it must pass long distance to a remote TV or ously, so the picture appears almost instantaneously VCR. It can be placed anywhere in the system and is after the set is turned on. The switch inserts a volt- powered in a similar fashion to mast-mount amps. age-reducing choke in series with the primary of the in-line color picture tube Precision-in-line color pic- power transformer and opens the high-voltage sec- ture tube. ondary winding, to reduce filament voltage to about in-line electron guns An arrangement of three elec- half the normal value. tron guns in a horizontal line. Used in color picture instant record One-touch recording. tubes that have a slot mask in front of vertical color instant replay A repetition of the action in a televised phosphor stripes. In the Sony Trinitron tube, a single football game or other type of program, achieved

152 intensity modulation

with a slow-motion video disk recorder or ordinary integrated receiver/descrambler (IRD) An enhanced video recorder. The replay can show the action pre- satellite receiver that applies advanced technology viously picked up or action from one or more other to improve video and audio quality as well as to cameras. decode scrambled channels. IRDs, with built-in instant review A feature found on some video cam- II circuitry, are capable of unscrambling eras that permits the operator to inspect a portion a high percentage of the coded channels that TV of the previously recorded material. For example, satellite system owners receive. About 57 of the more some cameras with instant review automatically re- than 200 available satellite channels are scrambled. wind the tape 3" while others have a review button Subscribers who want to receive these channels can on the handgrip. In the latter case, the last few register for those they prefer. The IRD then auto- moments of the recording are played back in the matically opens the signals that have been pur- viewfinder, first in reverse, then in forward; finally, chased. Some of these IRD units include additional the VCR is returned to Record/Pause position. Many features, such as menu-based on-screen controls, cameras without this feature permit reviewing what digital sound, programmable tuners and video noise has been shot, but these models use different ap- reduction. proaches. In some, the Camera/VCR switch must first integrating array See Solid-state camera. be set. This shifts the recorder from Record to Play intelligence Data, information, or messages that are mode. The Search function is then utilized (in re- to be transmitted. verse) to rewind the tape. The Play/Pause control is intelligence signal Any signal that conveys informa- then pressed to activate tape playback through the tion, such as code, facsimile diagrams and photo- electronic viewfinder. graphs, music, TV scenes, and spoken words. instant viewing The ability to produce on a TV screen intelligent agent Software that has been taught any “frame” of a videodisc by using the random something of the user’s desires or preferences and access feature of an LV VDP. Since the LaserVision acts on their behalf to do things. It might, for ex- system provides a contactless or laser beam stylus, ample, search through incoming material on net- one frame or revolution can be played continuously, works (e-mail and news) and find material of interest. offering a steady freeze frame. A typical disc con- It might also monitor TV viewing habits, accept gen- tains as many as 54,000 pictures on each side, with eral instructions about preferences and then, on its each image having its own designated number. By own, browse through huge databases of available pressing the numbered keypad, the viewer can lo- videos and make recommendations about programs cate any one of these frames or pictures. Instant of possible interest. viewing is possible, however, only in the standard intelligent interface A sophisticated microprocessor- play mode (CAV) or 30-minutes-per-side and not in based controller of VTRs and ATRs and switchers. long-play (CLV) or 60-minutes-per-side. intelligent phone A “vision of the future” for phone Institute of Electrical and Engineers (IEEE) A non- networks, including: Selecting entertainment on de- profit, technical professional association tasked with mand (movies, music, video); recording customized overseeing consensus standards development in the news and sports programming; enrolling and par- areas of electrical equipment, electronics, telecom- ticipating in education programs from the conve- munications and other areas. nience of subscribers’ living rooms; finding insurance In TV, the technique of framing a scene up-to-the-minute medical, legal and encyclopedic wider than needed, to allow for movement. information. integral nonlinearity (INL) A measure of the devia- INTELSAT INternational TELecommunications SATellite. tion of the analog-to-digital converter transfer func- A satellite network under international control for tion from the ideal. global communication by more than 80 countries. integral photography system One of the 3D-image The system requires stationary satellites over the At- display systems that doesn’t require special glasses. lantic, Pacific, and Indian Oceans and highly direc- integrated broadcast operation Refers to a fully au- tional antennas at earth stations. tomated, digital TV station. As a result of rapid ad- intensify To increase the brilliance of an image on the vances in digital technology and electronics in screen of a CRT. general, major manufacturers of professional/indus- intensity This is the same thing as brightness. trial audio and video equipment, including Sony and intensity control Brightness control. Chyron, have developed an array of sophisticated intensity modulation Variation of the density of an units. These include graphics and effects devices, electron beam in accordance with the instantaneous editors and complete digital multi-effects systems. value of the modulating signal. An obvious example integrated messaging Also called unified messag- of intensity modulation occurs in the reproduction ing. It is one of many benefits of running telephony of TV images by a picture tube in which the elec- via a . Voice, fax, electronic mail, tron-beam density is controlled by the video signal image and video are all on one screen. so as to produce the variations of light intensity on

153 intensity signal

the screen necessary to make up the picture. Also intercarrier interference Refers to the buzzing noise called Z-axis modulation. that is sometimes heard when white titles appear intensity signal Luminance signal. on the TV screen. Intercarrier interference results interactive CATV A two-way cable system from which when TV cable company amplifiers are incorrectly subscribers can receive and send signals, probably adjusted. Channels 2 to 13 (the low band channels) by punching buttons on their cable TV’s remote con- tend to be affected more than others. trol, which may look more like a computer keyboard intercarrier reception In a TV receiver, a method of than a traditional CATV handheld remote signaling sound reception in which the FM sound signal is device. derived from the vision detector or a post-detector interactive multimedia An electronic system through stage as an FM signal on a carrier frequency equal which an individual can retrieve data from various to the difference between the vision and sound car- media. It is also referred to as interactive video. rier frequencies. The method has the advantage that interactive television A combination of television the center frequency of the sound signal is unaf- with interactive content and enhancements. Inter- fected by drift of the local oscillator. active television blends traditional TV-watching with intercarrier sound system A TV receiver arrangement the interactivity of a personal computer. Program- in which the TV picture carrier and the associated ming can include richer graphics, one-click access sound carrier are amplified together by the video IF to Web sites through TV Crossover Links, electronic amp and passed through the second detector, to mail and chats, and online commerce through a give the conventional video signal plus a FM sound back channel. signal whose center frequency is 4.5-MHz difference interactive video A video system, typically computer- between the two carrier frequencies. The new 4.5- based, that permits the user to communicate with MHz sound signal is then separated from the video the video system to select material to be viewed and signal for further amplification before going to the the method of viewing. FM detector stage. interactive videodisc (IV) A prerecorded LaserVision Intercast A method developed by Intel for transmit- disc divided into chapters and/or frames for easy ref- ting web pages during the vertical blanking interval erence. The disc uses two audio channels and per- of a video signal. It is based on NABTS for (M) NTSC mits viewer participation in basic games. The player systems. can locate chapters (segments of a program such as interchangeability A term used to describe how well musical numbers) for perusal. IVs allow the user to a particular VCR can play back a tape recorded on rapidly locate a single frame (one picture such as a another VCR of the same type. page of a book or catalogue or a painting or photo- intercom line Usually the audio connection between graph). The two audio channels can present differ- the video director and the members of the crew. ent sound tracks, such as a foreign language and a intercutting A production technique in which a cut is translation for home study or alternate narration. made from a scene (long shot) to a detail of that “How to Watch Pro Football,” produced by NFL scene (close-up) to clarify or emphasize a point. Films, was the first IV presented for home viewing. interface 1. A device that allows devices to communi- It contained 15 chapters, individual frame material, cate with each other. For example, an interactive diagrams and a fast-paced football game. IVs have interface translates the language of a computer into not become widely used due to the advent of mul- signals a videodisc player can interpret. 2. To con- timedia CDROMs used with personal computers, nect two or more components to each other so that which do a similar job. the signal from one is supplied to the other(s). Feed- interactivity Control by the user, but in a much more ing a signal between units that run on different stan- significant sense than control of a TV set, that con- dards is the most frequent form of interfacing, as in sists primarily of selection from a limited number of connecting a 1/2" helical scan VTR to a 2" predetermined choices (channels). This is a satisfac- Quadraplex machine. tory mode for entertainment, but it becomes seri- interference 1. In radio or TV reception, any unwanted ously limiting if trying to use the TV for other signal, natural or manmade, that adversely affects purposes such as teaching, training, or selling. reception of the wanted signal. Natural interference Interactivity is the ability of a user (or a computer) to signals can arise from flashes, and control the presentation by a multimedia system, not manmade interference from signals on nearby fre- only for material selection, but for the way in which quency channels or image channels, from electrical material is presented. equipment and from car ignition systems (TV sig- intercarrier beat An interference pattern that appears nals frequently suffer serious interference from mo- on TV pictures when 4.5-MHz beat frequency of an tor-vehicle ignition systems). Interference signals can intercarrier sound system gets through the video amp be picked up on the receiving antenna or can reach to the video input circuit of the picture tube. the receiver via the supply mains. Some reduction in intercarrier buzz See Buzz. interference may be possible by using a directive an-

154 internal anti-reflective coating

tenna, by siting the antenna in an “electrically-quiet” good ones refresh at higher rates. Progressive HDTV spot, or by the use of RF filters in the receiver mains refreshes at 50 or 60 times a second. Generally, any- supply. The best method is to prevent the radiation thing over 70 Hz is considered to be flicker-free and of interfering signals by fitting suppressors to the therefore preferred, when affordable. offending equipment. 2. In optics, the effects ob- interleaved projection optical system A 4-million- served when two sources of light of the same fre- pixel, 110" projection display system that creates quency are superimposed. Areas where the two “virtual presence” effects in applications such as waves are in phase are illuminated more brightly than videoconferencing; NTT, Japan. The resolution those where the waves are in phase opposition and achieved by the system, according to company offi- thus one of the most familiar effects is the forma- cials, is four times that of current high-definition TV tion of interference bands or rings. standards. The high resolution is attained by an in- interference fading See Fading. terleaved projection technique that places four pix- interference suppressor A device designed to reduce els in the same area that would normally be occupied or eliminate distortion of a TV picture usually caused by one. The four pixels are shifted slightly in posi- by household appliances. A suppressor is installed tion with respect to one another and then interleaved into the wall socket and has apertures for 3-prong to deliver a fourfold improvement in both resolu- or 2-prong plugs. tion and brightness over conventional HDTV displays. interfield cut Cutting or switching from one source interleaved projection See Interleaved projection to another during the vertical or field sync period. optical system. With random switching a good deal of picture dis- interleaving A term used to indicate that the har- turbance is obtained, but in an interfield cut, the monics of the chrominance signal lie between the signal to cut is stored and a switch is made electri- harmonics of the luminance portion of the video cally or by relay only during the blanking interval. signal as it is viewed on a . This This gives no video disturbance, but if the syncs are indicates that the color information of a video sig- too badly damaged and are not properly restored in nal does not interfere with, although it is broadcast the interfield cut, frame roll may be obtained on a at the same time as, the luminance information. Sig- flywheel sync receiver. Also called cut in blanking. nals that have this interleaving property are not inter-frame coding Coding over a sequence of frames. readily seen on a TV screen because of their virtual Used in MPEG systems. The quality of a compres- cancellation characteristics. sion system doesn’t just depend on the compres- interline transfer device (ITD) One of the three basic sion ratio but on the type of compression used. architectures for obtaining the video signal in solid- Inter-frame coding allows higher compression fac- state cameras. In ITD the storage arrays are arranged tors by virtue of the fact that movement between alternately with the photosensitive arrays and are successive images is normally relatively small and connected to them by a transfer gate. During the hence coding efficiency increases. vertical retrace period the information is transferred inter-frame encoding A way of video compression horizontally from the photosensitive electrodes to that transmits only changed information between the storage electrodes by means of the transfer gates successive frames. This saves bandwidth. and then read out line by line in a similar manner to interlace In scanning, the technique of using more the FFTD. than one vertical scan to reproduce a complete im- interlock To run sound and picture together in perfect age. In TV, 2:1 interlace is used, giving two vertical sync from separate film and/or tape transports. scans (fields) per frame; one field scans odd lines, interlock wire See AC interlock. and one field scans the even lines of the frame. intermediate character In videotex, a character used interlacing Regular TV signals are interlaced. In the preceding a final character to increase the number US there are 525 scanning lines on the regular TV of possible management commands. screen, the NTSC standard. Interlaced means the sig- intermediate frequency (IF) A middle range frequency nal refreshes every second line 60 times a second generated after downconversion in any electronic and then jumps to the top and refreshes the other circuitry including a TV set. The majority of all signal set of lines also 60 times a second. Non-interlaced amplification, processing and filtering in a receiver signals, used in the computer industry and HDTV, occurs in the IF range. means each line on the entire screen is refreshed X intermodulation Distortion and unwanted signal en- times, depending on what the is output- ergy caused by signals being transmitted in other ting to the color monitor. The more the monitor is channels. Intermodulation is one of several forms refreshed, the better and more stable it looks—the of degradation that affect NTSC picture quality. less perceived flicker. For example, text on an NTSC intermodulation distortion Syn.: combination-tone US TV set tends to flicker. It doesn’t on a non-inter- distortion. See Distortion. laced monitor. Typical non-interlaced computer internal anti-reflective coating (IARC) A process de- monitors refresh at 60 to 72 times a second, but veloped for use with projection TV systems, designed

155 internal keying

to increase brightness, resolution and contrast, three she is looking for. This feature, sometimes referred acknowledged problem areas inherent to conven- to as Intro Scan, differs from index search, which tional projection TV. simply locates the beginning of programs that have internal keying A method of keying in which the key been automatically marked electronically each time signal can be sent through the SEG from any one of the Record button is pressed. the cameras already in use. See External keying. inverse transform See Transformation. International Radio Consultative Committee (CCIR) inverted image A condition occurring when a small An international organization concerned with the TV set is employed in a budget projection TV sys- establishment of radio and TV broadcasting stan- tem and no mirror is used. The special lens that dards throughout the world. projects the image onto the screen also creates an International Tape Association See International inverted image. This can be corrected in one of two Tape/Disc Association. ways: A service person can reverse the vertical con- International Telecommunications Union (ITU) An nection wires on the yoke of the TV picture tube, organization that designates locations for satellites. or he or she can add a picture tube inversion switch With the increase of communications satellites, some that permits either a normal or inverted picture for order was required to prevent them from interfering projection use. with each other or, worse, colliding. The positions inverter Circuitry to convert DC to AC; see DC-to-AC extend from 150 degrees to 70 degrees west longi- inverter. tude. It also sets many standards for transmission. invert operation In videotex, a display of characters interocular separation Distance between the right such that foreground and background colors appear and left eyes (between the pupils). to have been exchanged. If flash is applied, the po- interpolation A video technique used in motion com- larity of the flashing clock also is inverted. pensation where a current frame of video is recon- ion burn An area of reduced luminosity on the screen structed by using the differences between it and past of a CRT caused by partial destruction of the phos- and future frames. This technique is also known as phor by bombardment by heavy negative ions that forward and backward prediction. Interpolation is are liberated from the cathode or are formed by ion- also used to correct errors in video and audio by ization of the residual gas. The area is usually at the using the nearby “good” data. center of the screen because the heavy ions are not intervalometer A special timing device attached to a deflected to the same extent as electrons by the de- camera for automatic single-frame exposure in ani- flecting fields. mation (time-lapse) photography. It releases the cam- ion trap Method of avoiding ion burn of the screen of era shutter at predetermined intervals to condense a CRT. In one method the electron gun is aimed at large portions of time into smaller ones. For example, the neck of the tube and an external permanent hours of cloud movements can be recorded to play magnet is used to deflect the electron beam to the back with a running time of a few seconds, thus axis of the tube. Heavy negative ions liberated from dramatically speeding up the motion. With limita- the cathode or by ionization of the residual gas that tions, the accessory can be used in time-lapse video are responsible for ion burn are deflected to a smaller when connected to a home video camera. Keeping extent than the electrons and continue to bombard a portable VCR in Pause mode for an extended the tube neck. The use of an aluminized screen has length of time may cause damage to the tape or now rendered the use of ion traps unnecessary. video heads. When this function is built into a cam- IP Internet Protocol. See TCP/IP. era, it is usually referred to as an interval timer. IPPV Impulse Pay-Per-View. interval related carrier (IRC) Refers to cable-TV chan- ips Inches per second; the customary unit of measure- nels on frequencies starting at 55.25 MHz with in- ment of tape speed on an audio or video tape crements of 6 MHz (6N + 1.25 MHz). These channels recorder. are the same as standard frequencies except for IR Infrared. The band of electromagnetic wavelengths channels between 67.25 and 91.25 MHz. between the extreme of the visible part of the spec- interval timer A built-in video camera feature trum (about 0.75 µm) and the shortest microwaves designed for time-lapse or animation effects. See (about 100 µm). This portion of the electromagnetic Intervalometer. spectrum is used for fiber-optical transmission and intra-field coding Coding contained within one field. also for short-haul through-the-air data transmission. intra-frame encoding Coding contained within one IRC Interval Related Carrier. frame. IRD, satellite TV Integrated Receiver/Decoder. A de- intro search A VCR feature that automatically locates vice (set-top box) that not only receives the signals, all indexed material on a prerecorded videotape and but also deciphers them into a viewable picture. plays back the opening portion of each section for a IRE Institute of Radio Engineers. A system of measure- few seconds in fast motion. Intro search helps a ment used in audio and video. Besides representing viewer quickly find a selection on a tape that he or the professional organization, IRE is a term used for

156 IsoENET

measuring such items as frequencies and video lines. ISDN Integrated Services Digital Network. An interna- For example, white balance (the amount of color tional communications standard for sending voice, that can be viewed on a neutral object) is measured video, and data over telephone lines. ISDN requires in IRE. The lower the IRE number, the better the white special metal wires and supports data transfer rates balance. The figure of 0 IRE indicates perfect white of 64,000 bps. The original version of ISDN employs balance, a goal all TV manufacturers aim at but sel- baseband transmission. B-ISDN uses broadband dom attain. IRE plays an important role in waveform transmission and can support transmission rates of monitors, or , professional instruments 1,500,000 bps. B-ISDN requires fiber optic cables that feature switchable on/off IRE filters. (has not been widely implemented). IRE units A relative scale for measurement of analog I signal In NTSC video, I is one of the two color differ- video signal levels where blanking level is 0 IRE units ence signals, I and Q. The letter I stands for in-phase. and peak white level is 100 IRE units. (IRE is an acro- I signal consists of +0.74(R-Y) and -0.27(B-Y), where nym for Institute of Radio Engineers, one of the fore- Y is the luminance signal, R is the red camera signal, runners of today’s worldwide electrical engineer’s and B is the blue camera signal. I signal has a band- professional society, the Institute of Electrical and width of 0 to 1.5 MHz. It represents the colors rang- Electronics Engineers.) See Measuring the video. ing from reddish orange to cyan. Modern systems iris Means of controlling the amount of light that is use U and V instead of I and Q. allowed to pass through an optical system. It is an ISMA Abbreviation for the Internet adjustable set of metal leaves over the aperture of a Alliance. ISMA is a group of industry leaders in con- lens, used to control the amount of light passing tent management, distribution infrastructure and through the lens. Iris openings are measured in f- media streaming working together to promote open stops. Also called Iris diaphragm; diaphragm. standards for developing end-to-end media stream- iris control button A feature that closes down the ing solutions. The ISMA specification defines the iris or aperture of the lens to protect the sensitive exact features of the MPEG-4 standard that have to video camera tube when the camera is not in op- be implemented on the server, client and intermedi- eration. Camera tubes that are exposed to overly ate components to ensure interoperability between bright light or sun develop a “burn” that may be- the entire streaming workflow. Similarly, it also de- come permanent. fines the exact features and the selected formats of iris diaphragm Iris. the RTP, RTSP, and SDP standards that have to be iris in To begin a scene in a TV program by opening implemented. the camera from a completely closed position, so The ISMA v1.0 specification defines two hierar- that the scene appears within an expanding circle. chical profiles. Profile 0 is aimed to stream audio/ The opposite is iris out. See also Circle in and Circle video content on wireless and narrowband networks out. to low-complexity devices, such as cell phones or iris out See Iris in. PDAs, that have limited viewing and audio capabili- iris wipe Printing effect providing a transition from ties. Profile 1 is aimed to stream content over broad- one scene to another at the boundary of an enlarg- band-quality networks to provide the end user with ing or diminishing circle. When using a TV flying a richer viewing experience. Profile 1 is targeted to spot system, the generation of a circular wipe can more powerful devices, such as set-top boxes and be accomplished by means of a simple mechanical personal computers. iris similar to that used in a camera lens. Electronic ISO 1. International Standards Organization. An inter- generation is usually by a combined line and field national agency responsible for developing standards parabolic waveform switching signal. for information exchange. Has a function similar to iron oxide A particle combined with other metallic that of ANSI in the US. 2. Slang for isolated. For ex- oxides and ferrite to form a coating on magnetic ample, a TV camera may be isolated (iso’d) from oth- tape. ers being used in a production (an ISO camera) so ISDB Integrated Services Digital Broadcasting. Japan’s that its tape can be used as a backup or replacement. transmission specification for digital broadcasting. ISO camera See ISO. ISDB uses a transmission scheme called BST-OFDM isochronous Data transmission where timing is de- that ensures the flexible use of transmission capac- rived from the signal carrying the data. No timing or ity and service expandability in addition to the ben- clock lead is provided at the customer interface. In efits of OFDM. Since OFDM uses a large number of isochronous data transmission, data has no embed- carriers that are digitally modulated, it provides suf- ded timing—send it slower and it is still valid, just ficient transmission quality under multipath inter- late. Voice and video are intimately tied to timing. ference. The basic approach of BST-OFDM is that a Send voice slower and it sounds very different. transmitting signal consists of the required number IsoENET Networking standard for multimedia appli- of narrow-band OFDM blocks called BST-segments, cations from Santa Clara, Calif.-based National Semi- each with a bandwidth of 100 kHz. conductor Corp. IsoEnet is an interface between local

157 isolation

and wide area networks and has one 10-Mbit isolator A device designed to prevent electrical inter- channel for digital data, plus 96 ISDN-B ference between units in a video system. The isola- channels for voice and video. The normal Ethernet tor accomplishes this by filtering the line current. data channel is not impacted by the added service. The isolator eliminates such problems as hum, The system dedicates an additional 6 Mbits to iso- crosstalk and voltage differences. Some units per- chronous services, enabling it to handle high-quality mit hooking up any three components to its AC out- video traffic. The isochronous channels are divided lets. More sophisticated models, called isolation into 64-Kb/s segments to match ISDN WAN standards. , offer additional features and uses, such isolation The absence of interference in video com- as ensuring signal transmission with more than 120 ponents. Isolation is measured in dB. The higher the dB attenuation of interference and applying it to ul- number, the better the isolation. For example, a video tra-wide bandwidths and broadcast or remote TV switcher should provide approximately 40 dB of iso- lines. lation. If the number falls lower than this, interfer- iso reels Multiple reels of tape on which the same ence as well as image degradation are likely to occur. subject has been recorded simultaneously by differ- In devices like switchers, isolation refers to the abil- ent VTRs through different cameras (iso for equal). ity of the unit to block signal leakage and interfer- ISO standards Standards published by the Interna- ence from disturbing the different signals. Again, tional Standards Organization, the body co- the higher the dB number, the better the isolation. ordinating the work of various national associations. isolation transformer A transformer inserted into a They include a number of standards in the field of circuit to separate one section of the circuit from motion pictures and TV. undesired influences of other sections. It is usually isotropic The property possessed by a hypothetical made with a 1:1 ratio of primary turns to secondary omni-directional point-source antenna, the reference turns to eliminate a direct connection without chang- for antenna gain measurement. ing voltages. The isolation transformer is used to ITCA International Teleconferencing Association, a pro- prevent blowing fuses and chassis damage when fessional association organized to promote the use connecting test equipment to the AC TV chassis. of teleconferencing (audio and videoconferencing). The TV chassis that works directly from the power Located in Washington, DC. line, without power transformer, may have a hot ITFS Instructional Television Fixed Service. Group of TV chassis and should be protected with the isolation channels in the UHF frequency range set aside for transformer. Besides isolation of the power line, the educational use. transformer may have adjustable taps to raise or ITU International Telecommunications Union, a broad- lower the power line. Raising and lowering the cast standards committee that replaced the CCIR. power line in the AC TV chassis may be required to ITV Industrial TV service chassis or high-voltage shut-down. Slowly -IWQ A waveform used in NTSC color-bar pattern: black raising the power line may prevent damaging an- with 40 IEEE units chroma at -I phase, 100% W other horizontal output transistor. See also Isolator. (white), black with 40 IEEE units chroma at Q phase.

158 J

J CATV superband channel, 216-222 MHz. term for sudden irregular departures from the ideal jack 1. The opening or receptacle on a VCR, TV moni- value of a parameter such as the phase, amplitude tor or other component that accepts a male plug. or pulse duration of a signal. In TV signals jitter can Features like audio-in and video-out on VCRs and cause errors in synchronizing and these can lead to other equipment are also referred to as audio and erratic movements in the displayed picture. video jacks while the cables with matching connec- JJ CATV hyperband channel, 354-360 MHz. tors are called audio and video plugs. The terms jog/shuttle control A wheel-and-dial combination, “jacks” and “plugs” are often used interchange- usually found on the front of more costly VCRs, de- ably. 2. Male cable connector, or plug, as in phono, signed to move the video picture one frame at a mini, phone plug. time and assist in a manual bi-directional search for jacket The protective and insulating housing of a cable. a particular segment. Used chiefly for editing, the jaggies Professional jargon for spatial aliasing on near- jog/shuttle control, or jog dial shuttle ring as it is horizontal lines in a TV picture. Caused by lack of sometimes called, allows the user to turn the outer pre-filtering. Syn.: stair-stepping. ring for moving the tape from slow motion to search jam See Salad. speeds. The inner jog wheel or dial moves the tape jam sync The ability of a SMPTE time code generator frame by frame, helping the user to choose the ex- to feed or “jam” a particular time code address from act edit point. Some VCR models provide a single the time code generator to a master VTR. Jam sync control to accomplish both tasks. The feature on is used when editing material from more than one these machines does not work as fast or accurately video tape into a single master, so that the master as that of the two-part design. Some VDPs have a tape will have continuous, unbroken time code. similar jog dial shuttle ring. Located on the remote Java A general-purpose programming language de- control, the ring allows the user to view a program veloped by Sun Microsystems and best known for on the disc forward or backward and at a variety of its widespread use on the World Wide Web. Unlike speeds, from one frame at a time to 10 times stan- other software, programs written in Java can run on dard play speed. any platform type (including set-top boxes), as long Joint Photographic Experts Group standard (JPEG) as they contain a Java Virtual Machine. A standard adopted by the International Standards JBIG Joint Bi-level Image Experts Group. Losslessly com- Organization (ISO) for compressing still images with presses binary (one bit per pixel) images. The intent little or no data loss. It can be used for moving im- of JBIG is to replace the group 3 and 4 fax algorithms. ages only if it treats each field or frame as a sepa- JBIG can be used on grey-scale or color images by rate entity. applying the algorithm one bit-plane at a time. joy stick In video games, a lever which controls the jeep To convert a TV receiver into a TV monitor or movements of the game action on the TV screen. In monitor/receiver by rewiring the internal circuitry and relation to a VTR, a joy stick regulates a special effect adding input and output jacks for video and audio. on the screen or tape movement during editing. jenny A portable electric generator, as used in film JPEG Joint Photographic Experts Group. A still image and TV. compression system that reduces the size of a digi- jerkiness Term to describe temporal aliasing. An arti- tal image file by using an intraframe compression fact due to deficiency of temporal filtering, for ex- scheme, where redundant information (that is, most ample in the process of linear standards conversion of the blue colors in a blue sky) is thrown away. When (as opposed to motion compensated standards con- used in conjunction with hardware, JPEG can com- version). It is for this reason that 4-field converters press and decompress images fast enough to dis- have less judder than 2-field converters. Syn.: judder. play 30-frames-per-second video. This is why JPEG jitter Short-term variations in the characteristics (such is used as the main compression algorithm on most as frequency, amplitude, etc.) of a signal. General nonlinear editing systems.

159 JPEG++

JPEG++ Storm Technology’s proprietary extension of buildings in New York’s Times Square and in Tokyo the JPEG algorithm. It lets users determine the de- and other cities. gree of compression that the foreground and back- jump cut An undesirable cut in TV and film produc- ground of an image receive; for example, in a tion that occurs when a director or editor makes an portrait, you could compress the face in the fore- abrupt transition from one camera angle or scene ground only slightly, while you could compress it in to another. The effect is to make it look like the pic- the background to a much higher degree. ture has “jumped” from one shot to another. judder See Jerkiness. jumping out The process of removing individual frames jukebox A piece of hardware that holds storage me- from a film or a video tape. dia, such as optical discs or cartridge tapes. Juke- junction box A connector accessory with two wired boxes are typically designed to hold as few as five female connectors and designed so that two male and as many as 120 devices. Like old-fashioned plugs can be joined together. The junction box is most record playing jukeboxes, media is moved by a ro- often used by professionals. See also Spider box. bot-like device from the storage slot to the drive Jungle Multipin, multifunction chip, e.g., Y/C Jungle reading it. This lets the user share one drive among CX20193 IC in Sony 19" TV. several cartridges or discs. Video jukebox can con- JVC A Japanese electronics firm (Victor Company of tain everything broadcast on TV, etc. See Oracle Japan) that introduced the first VHS system portable . VCR in 1978. The HR 4100 was a one-speed VCR, Jumbotron A giant presentation TV unit that mea- which could record for up to three hours on a bat- sures 23.5 x 32 feet and is used for outdoor dis- tery charge as well as on house current. With its play. Developed by the Sony Corporation, the built-in RF adapter it could also record and play back jumbotron is used to screen travelogues, commer- through a conventional TV receiver. Including bat- cials, public service announcements (PCAs), videos, tery pack, it weighed 21 pounds. See also and headline news to thousands of passersby from Matsushita.

160 K

K 1. Short for kilo or kilobyte. In decimal systems, kilo to be square—equivalent to regarding horizontal stands for 1,000, but in binary systems, a kilo is 1,024 definition as equal to vertical definition—then there (2 to the 10th power). Technically, therefore, a kilo- are 4n/3 elements in each line, the aspect ratio be- byte is 1,024 bytes, but it is often used loosely as a ing 4:3. The lowest video frequency that will enable synonym for 1,000 bytes. For example, a computer such a row of elements to be resolved is one in which that has 256K main memory can store approximately one half-cycle represents a white element and the 256,000 bytes (or characters) in memory at one time. other half-cycle a black element. This is the upper To distinguish between a decimal K (1,000) and a video-frequency limit for the system and it gives val- binary K (1,024), the IEEE has suggested following ues appreciably higher than are used in practice. The the convention of using a small k for a decimal kilo lower practical values are justified by the assump- and a capital K for a binary kilo, but this convention tion that the horizontal definition need only be, say, is by no means strictly followed. 2. When used to 0.7 times the vertical definition: in other words they describe memory chips, K stands for kilobit (1,024 are based on a Kell factor of 0.7. bits). This is equivalent to 128 bytes. Most memory Kelvin A term used in video lighting to measure color chips come in increments of either 256 kilobits (64K temperature of a given light source, usually with a bytes) or 1 megabit (256K bytes). 3. Abbreviation degree symbol. For example, an ordinary household for kelvin (plural kelvins); here K is used without the light bulb of 100 W is rated 2900 degrees K, stage degree sign and is separated by a space from the lighting is based around 3200, sunlight is approxi- temperature value, as in 273.16 K. 4. Unofficial ab- mately 5800, while high-overcast, bright days are breviation for kilohm; here the k follows the value, close to 6000 degrees K. If Kelvin temperatures are with no space between, as in 10k. 5. CATV changed in a scene, the whites must be re-balanced superband channel, 222-228 MHz. 6. TV standard. (camera’s white balance control button) for accu- Characteristics: see D, except used band—K uses rate rendition of color. The lower the Kelvin, the UHF. 6. Abbreviation for black. 7. Frequency band warmer the light color. 18-27 GHz. Kerr cell A light modulator consisting of a liquid cell Ka-band 27-40 GHz. containing two parallel plane electrodes and situ- karaoke A multimedia entertainment and educational ated between crossed polaroids. Normally no light system invented in Japan for night club entertain- emerges because the polaroids are crossed. Signals ment. The basic system consists of a microphone applied between the electrodes cause the plane of and audio system, source of background music (typi- polarization of the light to rotate (Kerr effect) so al- cally CDs or CD-ROMs), and closed-circuit TV. Pa- lowing light to pass. Used in projection-type TV re- trons can sing or perform to recorded music, and ceivers to modulate a beam of light or serve as a the composite performance can be recorded on vid- high-speed camera shutter. Also called electro-opti- eotape. It is also used for educational and training cal shutter. purposes. Kerr effects Two effects in which the optical proper- K-band The range of frequencies from 11 to 36 ties of transparent material are affected by electric GHz used by radio and TV stations for satellite or magnetic fields. The electro-optical effect is the transmission. effect whereby the direction of polarization of plane- keeper In film and TV, a segment of film or tape that is polarized light through a refractive medium is ro- to be retained and is likely to be used, or kept, in tated by an electric field applied perpendicularly to the final cut (edited version). the direction of propagation of the light. The Kerr Kell factor In TV, a factor expressing the ratio of hori- cell utilizes this effect. Pockel’s effect is the Kerr ef- zontal to vertical definition. Suppose each of the n fect when it occurs in a piezoelectric material. lines of a TV picture is made up of alternate black Pockel’s effect can be used for measurement of dis- and white elements. If these elements are assumed tance by a mekometer. Such an instrument can

161 key

measure distance to an accuracy of 0.05 mm in 50 one or a few buttons or keys, used, for example, to m. The magneto-optical effect occurs when plane- make selections from a videotex system. polarized light is reflected from a highly polished keystone distortion 1. In TV, geometric distortion of pole face of a strong electromagnet. Slight elliptical the image causing a rectangle to be reproduced as polarization of the light beam is produced. a trapezium or keystone. The effect can be caused key A special effect whereby the signal from one video by interaction between line-scanning and field-scan- source cuts a hole into another video source. A fea- ning circuits but occurred in the early days of TV as ture on some video switchers, which permits creat- a result of oblique scanning of the target by the elec- ing electronically the illusion of placing one image tron beam in iconoscope tubes. It was necessary to over another without getting rid of the second im- introduce correction to obtain an accurately rectan- age. There are four basic types of keys: external key, gular image. 2. Camera-tube distortion evident chroma key, matte key, and self key, each capable because the length of a horizontal scan line is lin- of providing a different special effect. For example, early related to its vertical displacement. It occurs a chroma key substitutes a particular color with an when the electron beam in the camera tube scans image from a different source. A matte key, on the the image plate at an acute angle. A system that other hand, consists of only one color for keying. has keystone distortion distorts a rectangular pat- keyed automatic frequency control An AFC method tern into a trapezoidal pattern. The distortion is nor- employed in the frequency modulator for MUSE sig- mally corrected by special transmitter circuits. nals. This method is as follows: The input MUSE sig- keystoning An effect which results in a narrower or nal takes the specified mid-level every 1/60 second. wider projected image at the top of the screen than At that time, the frequency of the modulated out- at the bottom. This is caused when the slide or movie put signal takes the center frequency (140 MHz). projector is not properly aligned with the screen. In keyed rainbow generator A rainbow generator that those movie houses where keystoning occurs, the has facilities for generating 3.58-MHz sides of the screen are usually darkened to conceal pulses, for making crossover adjustments and for the effect. Keystoning is also a problem in projec- general color TV receiver troubleshooting. tion TV systems using mirrors. keyed insert Keying. kickback power supply Flyback power supply. keyframe A set of parameters defining a point in a kicker 1. On a TV or broadcast, an inconsequential, transition, such as a DVE effect. For example, a humorous, or even zany final item; also called zip- keyframe may define a picture size, position and per. 2. A light to the side or rear of a subject; also rotation. Any digital effect must have a minimum of called kicker light, kick light, stringer light, cross back- two keyframes, start and finish, although more com- light, or side backlight. plex moves will use more, even as many as 100. In- kideo Home video for children. creasingly, more parameters are becoming kidvid Refers to TV and video aimed at children. “keyframeable,” meaning they can be programmed kilroy The defective framing of a TV picture in which to transition between two or more states. the lower portion of the heads of performers or oth- keying 1. Keyed insert, inlay insert. In a video system, ers is cut off. The origin is a cartoon character in the the process of inserting one picture into another World War II made famous by the motto scribbled picture under spatial control of another signal, called on thousands of walls, “Kilroy was here.” keying signal. 2. In digital TV transmission, the form- kinescope 1. Picture tube in a TV receiver (US). 2. An ing of the signal by modulating a carrier between early and imperfect video storage and reproduction discrete values of some characteristic. See FSK, QAM, technique (before the introduction of videotape) in QPSK. which a film of a TV program is made by placing a keying signal Signal that actuates an electronic switch movie camera in front of a TV screen displaying that in the production of special effects. It can be gener- program. In Britain, called a telerecording. ated electronically, or obtained from a video signal kinnie A name often applied to the picture tube. by passing the signal through a special effects kk CATV hyperband channel, 360-366. See TV amplifier. channel assignments. key light In video, the main light source of a scene, klieg light A powerful, wide-angle carbon arc lamp used which emphasizes the important objects in that in motion-picture, theatrical, and TV production; pro- scene. The key light is usually located near the video nounced “kleeg” and sometimes misspelled Kleig. camera and above the subject to minimize shad- klystrode A hybrid tube that employs both a con- ows. This light works best in conjunction with fill trol grid and velocity modulation. This has ex- lights, etc. The key light can work with available light, tended the use of the klystron principle into VHF the latter acting as the fill. See Lighting. TV transmitters. keypad 1. That portion of a remote control designed klystron An electron tube in which the electron beam to operate specific functions of a VCR, TV set or is velocity modulated to generate or amplify micro- VDP. See Numeric keypad. 2. A limited keyboard with waves. The electron beam from the cathode passes

162 Ku-track

between the grids of a cavity resonator known as a k rating Method of stating the subjective effect of buncher. The input signal is applied to this resona- linear amplitude and phase distortions on a TV sig- tor and the resulting potentials between the grids nal. Sine-squared pulse and bar signals and field- cause velocity modulation of the beam. Bunching frequency square wave signals are passed through occurs in the drift space, and the bunches, in pass- the system. The output waveforms are compared ing through the catcher grids, induce an amplified with special oscilloscope graticules marked with lim- output signal in the catcher resonator. The beam is its for various k ratings, and the k rating of the sys- finally collected at the anode (or collector). Used in tem is stated as the largest value found—i.e., the TV transmitters. See Applegate diagram. worst rating. knee In the graphical representation of a tonal repro- kroma glass Colored mirrored glass that reflects and duction process, such as photography or TV, a point transmits light. It is used in video and photography or region of inflection on the characteristic curve, for special effects. where the slope representing the rate of change al- ktp/shg blue laser A laser that reads a high-density ters, usually from a higher to a lower value. optical disc at room temperature; Pioneer Electronic koch resistance The resistance of a photocell when Corp., Tokyo. Previous attempts have only been suc- light is incident on the active surface of the tube. cessful at low temperatures. Development of a Kodak still-picture process A hybrid technique of room-temperature, solid-state, blue laser was a key traditional and electronic photography. It uses the to optical disc systems capable of recording mul- traditional photographic method but also permits tiple hours of high-resolution video on a CD-sized pictures to be manipulated and viewed electroni- disc. cally. The system is called Photo CD; developed by Ku-band Frequencies in the 12-18 GHz range. It is used Kodak and Philips. A consumer receives 35-mm by radio and TV stations for satellite transmission. negatives and prints from the photo finisher in the Ku-band satellite Communication satellite that con- traditional manner. However, the images can also tains transponders on frequencies in the Ku-band be converted to digital data and recorded on a CD from 11.7 to 12.2 GHz. Signals of these frequencies and then played back on a TV screen by using a can be received by relatively small TVRO dishes, thus special player. Each disc can contain as many as 100 making DBS services possible. Ku-band transmission pictures from either slides or negatives. Photo CD is is sensitive to atmospheric changes, however, and now targeted towards professionals, and the Pic- satellites using that band cover only a small portion ture CD is targeted towards consumers. of the US, in contrast to C-band satellites, which KoyCrypt A scrambling system by Hi Tech Xtravision. cover most of the country. A VideoCrypt clone, it is claimed to be harder to Ku-track TV news truck, a mobile unit for satellite trans- hack than the original. Not used by broadcasters mission. The vehicle is sometimes called a 12-14 because of copyright issues. truck or 12-14 unit, after the GHz range.

163 L

L 1. CATV superband channel, 228-234 MHz. 2. TV lies for its action on the radiation emitted by certain standard; France, Korea. Characteristics: 625 lines/ atoms when transitions occur between discrete en- frame, 50 fields/s, interlace—2:1, 25 fr/s, 15,625 ergy levels. In practice, positive feedback is usually lines/s, aspect ratio—4:3, video band—6 MHz, RF applied to the amplifiers (by use of mirrors at the band—8 MHz, visual polarity—positive, sound input and the output) to make them oscillate. They modulation—F3, gamma of picture signal—0.5. then become generators of coherent light in the form LAC Live Action Camera. of a narrow and sharply defined beam of good spec- LADT Local Area Data Transport. tral purity and frequency stability. The four basic types lag 1. In photocells and camera tubes, the time that of laser are gas, liquid, semiconductor, and solid. elapses between a change in light input and the cor- Laser technology has been successfully applied to responding change in electrical output. Lag in cam- such video equipment as VDPs and projection sys- era tubes tends to produce blurred images of objects tems. Lasers are also used in CATV in combination that move rapidly across the field of view. Keeping with fiber optics technology. lag to an acceptable level is one of the difficulties laser-based projection system An experimental pro- in the design of photoconductive targets. 2. The jection TV system that features a low dispersion of temporary retaining of the electrically charged im- the beam so that focus is not greatly affected by the age of a TV camera tube. See also Image reten- angle of the screen. First demonstrated in 1988 at a tion. 3. Time constant of many phosphors and National Association of Broadcasters convention, the targets in TV sufficient to cause smear and persis- laser-based system, despite some interesting advan- tence on a moving object. 4. In photoconductive tages over conventional systems, has suffered sev- tubes, the rate of decay of the video signal when eral setbacks—chiefly financial. illumination is changed abruptly or cut off. See also laser beam That part of an optical disc player or sys- Photoconductive lag. tem that carries the video signal without making lambert (L) A CGS unit of luminance or brightness, physical contact with the disc. Using only a beam of defined as brightness of a perfectly diffusing sur- light, the laser beam stores more video information face, when the total flux radiated is 1 lumen per on the disc than can be packed onto videotape. This square cm. The SI unit of luminance, the candela results in a clear, more detailed screen image. Since per square meter, is preferred. the laser beam head or arm never touches the LAN Local Area Network. laserdisc, the disc is virtually free from deterioration. lands In optical recording, refers to the areas of the In addition, the sound from VDP equals that pro- data tracks which are between the pits. These are duced by a CD system. typically the areas not touched by the recording la- laser communication based ser beam during mastering. on a laser beam that is modulated for voice, video, lap dissolve A film and video transition and special or over information bandwidths effect in which one scene is faded out while the up to 1 GHz. next scene is faded in, both occurring simultaneously. laserdisc In video, prerecorded software that resembles lapel mike A small microphone clipped to a lapel, a long-playing record and is used in conjunction with necktie, shirt, or elsewhere, or worn hanging around a videodisc player. Unlike videocassettes that can the neck; also called lavaliere, lavaliere microphone. both record and play back, can only play large-area flicker See Flicker. back prerecorded programs. Laserdiscs are read by large screen TV Images bigger than those that can be a laser beam that never makes physical contact with formed on a directly viewed CRT. See also Projec- the disc, thereby preserving the disc from wear and tion television. tear almost indefinitely. CAV laserdiscs, which offer laser Light Amplification by Stimulated Emission of special effects, have a maximum playing time of 30 Radiation. A device for light amplification which re- minutes while CLV discs contain 60 minutes of pro-

164 LCD

gramming. LV discs come in two sizes, 8 and 12 age stored in the charged capacitance in an icono- inches, both using analog video and analog/digital scope. In photography, the latent image remains on audio. the exposed film, invisible to the naked eye, until it laserdisc player See CLV, Double-side videodisc player, is processed or developed. Laserdisc, LV videodisc system, Videodisc player. laugh track The audio component of a TV situation laser-lock With an LV videodisc player, a malfunction comedy or other program on which audience laugh- in which the laser arbitrarily locks into a single frame. ter is inserted, from tape cassettes with various types This may sometimes be caused by fingerprints on of actual or artificial laughter. the disc. lav Lavaliere microphone. laser optical media Any hard plastic disc of informa- lavaliere microphone (LAV) A miniature condenser- tion that has been recorded and can be read by a type microphone which is designed to pin or clip on laser light beam. Discs include a variety of types: the the clothing of the subject being interviewed and 3- and 5-inch CD, CD-I, 5-inch CD-ROM, 5-inch CD-V, videotaped. The lavaliere microphone is omnidirec- DVD, 5-inch CD-Write Once, 5-inch DVI and 8- and tional. This unobstructed mic is inexpensive, provides 12-inch LV (laser videodisc). good fidelity and rejects echoes and other inciden- laser projector Source of a laser beam. Used in 3D TV tal surrounding noises. It is very popular for talk camera systems; it emits a very narrow beam of light shows and interviews and is named after Madame or other radiant energy along a path in accordance de La Valliere, a onetime mistress of Louis XIV, who with information received from a always wore a jewel suspended on a chain above generator. her bosom. Also called lapel mike. laser TV image A TV image displayed by laser beam. Lawrence tube Color display tube, named after the The system, developed by Schneider Rundfunkwerke American physicist who first suggested the prin- AG (Germany), uses a giant rear-screen projector ciple of operation; also known as chromatron, fo- containing a laser. The laser beam is deflected by a cus-mask and post-deflection focus tubes. It is an scanner that separates picture information into R, attempt to reduce the complexity of color TV receiv- G, B constituents, with no need for a CRT. Due to ers, by removing the need for static and dynamic the highly focused laser light, the resulting picture convergence. is bright and comparable to images viewed on con- layered embedded encoding The process of com- ventional TVs, yet the screen requires no depth, just pressing data in layers so successive layers provide surface. more information and thus higher quality reconstruc- Laser VideoDisc (LV) An optical videodisc, made by tion of the original. That is, a single stream of data Philips of Holland. can supply a range of compression and, thus, in the LaserVision (LV) Electronic optical machine introduced case of video, a scalable range of video resolution in 1978 and containing a low-power laser that re- and picture quality. This is particularly useful for a flects off the surface of the videodisc and creates multicast where a single stream is sent out and electronic signals that can be seen on a TV screen. people are connecting over varying bandwidths. The See also CAV, CLV. low bandwidth connection can take just the lower last channel function Last memory function. layers while the high-bandwidth connection can take last memory function A feature, sometimes found all of the layers for the highest quality. on videodisc or CD video players, that resumes play- layering In music or sound production, the technique ing a disc at the same point at which the machine of combining many sound generators to create a was shut off. This function is sometimes listed as richer sound. last channel memory. LCD Liquid Crystal Display. An alphanumeric display last telecast (LTC) A term used at a TV station to indi- using liquid crystal sealed between two pieces of cate the last program of the broadcast day. glass. The display is divided into hundreds or thou- latency The factor of data access time due to disk sands of individual dots, which are charged or not rotation. The faster a disk spins the quicker it will be charged, reflecting or not reflecting external light at the position where the required data can begin to form characters, letters and numbers. LCD dis- to be read. As disk diameters have decreased, rota- plays have certain advantages. They use little elec- tional speeds have tended to increase, but there is tricity and react reasonably quickly, though not nearly still much variation. Modern 3-1/2-inch drives typi- as quickly as a glass CRT. They are reasonably leg- cally have spindle speeds of between 3,600 and ible. They require external light to reflect their infor- 7,200 revolutions per minute, so one revolution is mation to the user. The so-called “supertwist” LCDs completed in 16 or 8 milliseconds (ms) respectively. are more readable. In active matrix displays, the cir- This is represented in the disk specification as aver- cuit board contains individual transistors for each age latency of 8 or 4 ms. pixel, or dot on the screen: the crystals can shift latent image A stored image, as in the form of charges quickly, resulting in a higher quality image and abil- on a mosaic of small . In video, an im- ity to display full-motion video.

165 LCD counter

LCD counter In video, a feature employing liquid crys- vision relay service (CARS) station used within a cable tal display for digital readouts on more recent VCR television system or systems for the transmission of timers. LCD provides dark digits against a light back- television signals and related audio signals, signals ground, in contrast to LED, which features red or of standard and FM broadcast station, signals of in- green digits against a dark background. structional television fixed stations, and cablecasting LCD digital scanner programming system A device from a local transmission point to one or more re- of some VCRs for simple and accurate timer record- ceiving points, from which the communications are ing. The basic elements of the system are LCD digi- distributed to the public. tal scanner and programming sheet. LCD digital LDTV Low Definition TV (e.g., VHS). scanner programming procedure: lead-acid battery A less expensive battery than the 1. Trace the digital scanner across the bar codes. nickel cadmium type. The lead-acid battery has to 2. Confirm the scanned programming information charge overnight whereas the NiCad can be charged on the built-in LCD. in less than 2 hours. Found in portable video 3. Transmit the programming information. systems. 4. Double-check programming information on the leader 1. The blank segment found at the beginning multi-function display. of a videotape. A leader is used to feed the mag- LCD panel A VCR remote control panel using an LCD netic tape through the tape mechanism and secure to program in recording information, which is then it onto the roll. 2. A short piece of film or videotape transmitted to the VCR. Normally, with recent VCR that is placed on the front of a videotape recording models, such information as program number, day or film used in TV. The practice was originally devel- of week, start time, stop time, channel and record- oped and encouraged by the SMPTE for film and ing speed has to be programmed on screen using today both film and videotape leaders are known the TV set. Remote controls with LCD displays by- more formally as society leader or SMPTE leader. The pass this step; programming can be done away from film leader consists of some 30 s of film that con- the TV set without the set having to be turned on, tains 15 or 20 s of black blank film (for threading and the data sent to the recorder by way of a trans- the projector) and 10 s of timing numerals. In addi- mit button on the remote panel. tion to the timing function, an SMPTE leader on a LCD projection TV A large-screen TV system that uses videotape provides electronic test signals to allow liquid display panels from 1 to 3" thick. The LCD technicians to adjust the settings on the VTR before projection TV is much lighter than conventional CRT- a full playback or dubbing operation. It is 45 s in based projection systems—thus more portable. In length. addition, it offers screen sizes from 35 to 120" with lead-in Refers to the antenna cable that is connected about 350 lines of horizontal resolution. The light to the TV receiver. Also called down-lead. source of the LCD projector is projected through a leading ghost A ghost displaced to the left of the matrix of tiny, semiconductor shutters, whose posi- image on a TV receiver screen. tions determine the light value of that pixel. Some leading/lagging chrominance effect A technical ab- advanced models feature a single beam unit, a rela- erration in a TV picture. This effect occurs when the tively light 30-pound projector, exceptionally bright chrominance portion of the video signal leads or lags picture quality and improved definition. LCD video behind the luminance signal. The result is an undes- projectors usually do not provide any audio circuitry ired effect in which the colors appear to the left (lead- or tuner; these components must be supplied by ing) or to the right (lagging) of the image. the user. lead-in insulator A tubular insulator inserted into a LCD status panel A video camera feature that is de- hole drilled through a wall, through which the lead- signed to inform the user about the position of vari- in wire can be brought into a building. ous camera operations. The LCD status panel is leakage current test, VCR A test to determine if any usually built into the camera body. part of the AC line has come in contact with metal LCD television The use of LCD panels instead of con- cabinet or base. It is a safety check to prevent a po- ventional image tubes in TV sets. LCD TV, although tential shock hazard. A volt- is needed to not presently available in all its varieties, promises perform the test. With the VCR unplugged, short certain advantages over the ordinary CRT in every the two flat prongs on the end of the AC cord with TV set—it is lighter, thinner and uses less power. a jumper wire. Connect one test lead from the meter However, LCDs need their own light source. LCDs, to the jumper on the AC cord. Connect the other essential for the much-touted flat-panel wall TV, are test lead to any and all bare (not painted) metal parts also currently employed in front and rear projection of the deck. For a typical VCR, the meter should TV systems. The first LCD TV appeared early in 1981 read about 50 kohm to 100 kohm—if you get any in an experimental model by Toshiba and featured a reading at all. Not all exposed metal parts of the 2" black and white image. See LCD projection TV. VCR will return a high value. Touching the center LDS Local distribution service station, a fixed cable tele- conductor of one of the audio output connectors

166 lift

could yield a very low resistance, say from 1 kohm to which the lens is attached. See also C-mount, to 50 kohm. Universal lens mount. leapfrogging The technique of bringing in distant sig- lens paper A paper specially made for cleaning lenses. nals on a CATV system. lens speed Parameter defining the ability of a par- leddicon A camera tube with a photoconductive tar- ticular lens to collect light and work at different get of lead oxide. light levels; usually expressed by its lowest f-stop legend Titles or information keyed, or superimposed, number. on a TV picture. lens stabilization A unique video camera feature that leko See Lekolite. produces a relatively stable picture by physically ad- lekolite An ellipsoidal spotlight with individual push- justing the lens assembly to compensate for camera shutters for focusing the light, used in TV to create movement. This is accomplished by the use of sens- background effects and also used in film and the- ing devices that scan horizontal and vertical move- ater. Commonly called leko, it is made by Strand ment. A tiny computer receives these signals and Lighting, Compton, California. sends them to two miniaturized motors that control lens 1. (a) A piece of glass, or other transparent sub- the horizontal and vertical motion of the lens, stance, with two curved surfaces, or one plane and thereby correcting much of the camera movement. one curved, regularly bringing together or spread- Not all cameras offer this feature that provides a ing rays of light passing through it: a lens or combi- steadier image than that usually produced by the nation of lenses is used in optical instruments to form conventional video camera. Also known as auto an image. (b) A combination of two or more such image stabilization. pieces. 2. Any of various devices used to focus mi- lens turret Sometimes called rack. See Lens. crowaves, electrons, or sound waves. 3. An arrange- lenticular lens See Fresnel lens. ment of CRT-electrodes that produces an electric field lenticular system One of the 3D-image display sys- that focuses electrons into a beam. 4. A series of tems which doesn’t need to use special glasses. optical elements, contained within a video camera, letter box See MIT-CC system. which collect and focus light. Several lenses may be letterboxing Refers to the wide aspect ratio or di- attached to a lens turret, or revolving mount. There mensions of theatrical films and their presentation are two major types of lenses found on video cam- on conventional TV screens. Some telecasts, deter- eras: the fixed focal length and the zoom. The latter mined not to cut parts of the original film, present is the more popular and more expensive. It has vari- the entire wide-screen view, resulting in black bor- able focal lengths. For example, it can be used as a ders on the top and bottom of the TV screen. Some- wide angle, normal or telephoto lens with a simple times TV stations add a decorative bezel to these adjustment or can zoom in or out during the re- unattractive black borders. The term stems from the cording of a subject or scene. The zoom lens often shape of the slot in mailboxes. has a macro feature, which allows the lens to focus level 1. In video, a specified position on an amplitude on objects as close as an inch or two from the lens scale applied to a signal waveform, such as refer- barrel. Another feature of a lens is its maximum ence white level and reference black level in a stan- opening or aperture. The larger the opening, the dard TV signal. 2. The strength of the audio signal, more light it admits; also, the more expensive the usually designated in dB. MIC level designates a low- lens. Lens openings are calibrated in f-stops, such impedance line on VCR, suited for a mike input. LINE as f/11, f/16, etc. Earlier camera models had a fixed level, AUX, and AUDIO IN designate a high-imped- or stationary lens. Many of today’s cameras have ance line suited for audio mixers, tape recorders, or lenses that are interchangeable through the use of other VCRs. a standard C-mount. However, the zoom lens has level-dependent gain Variation of gain of an amp eliminated the need for changing lenses, at least for with variation of input signal level. most home video users. Sometimes “lenses” may level-dependent phase Variation of phase shift consist of simply an open optical aperture, e.g. in through an amp with variation of input signal level. some 3D TV camera systems, using laser projectors lhc Left-hand circular (polarization). and laser sensors. 5. Anat. A transparent, biconvex lift 1. In a TV, a pedestal of adjustable height. 2. Con- body situated between the iris and the vitreous hu- trol associated with each picture-generated appara- mor of the eye: it focuses upon the retina light rays tus such as a camera, telecine machine, etc., whereby entering the pupil. the operator can lift the picture signal bodily up or lens clearing brush A very fine brush specially made down in potential with respect to blanking level and for cleaning a lens. so set the darker tones of the picture for optimum lens line A teleprompting system that shows one line contrast in relation to black. This is achieved by al- at a time at the center of the TV camera lens, visible tering the DC level of that portion of the generated to the performance but not televised. video waveform containing the picture signal with- lens mount The assembly on the front of the camera out affecting the blanking level, and is most conve-

167 light

niently carried out by modifying the DC conditions ject, provides general illumination to the scene area, associated with the blanking pulse insertion circuit. assuring that the scene is bright enough not to cause Because the lift control operates equally on all sig- any video noise. The key light is the brightest and is nal levels comprising the picture information, any aimed at the subject. It may be a spotlight or a flood- adjustment of this control usually needs to be ac- light. It accentuates the subject, casting a definite companied by an adjustment of picture amplitude shadow. It is usually positioned 45 degrees from the to establish the highlights of the picture in relation camera and higher than the subject. The fill light, to peak white level. 3. The process of increasing the often the same as the base light, is soft and lights number of subscribers at a CATV system. 4. A por- up the dark areas of the scene. It is not as bright as tion of a radio or TV commercial for use as a shorter, the key light. The back light, usually a rear spot- separate commercial. For example, to save on pro- light, provides definition when aimed at the sub- duction costs, a 30-second commercial can be pro- ject. It separates the subject from the background. duced with a 10-second lift within it, for use as a The eye light is a tiny spotlight which, when aimed separate 10-second identification. at the subject’s eyes, causes highlights in them, light Technically, light is electromagnetic radiation vis- making them appear more lifelike. ible to the human eye. The term is also applied to lighting arrester (LA) A commercial protective device electromagnetic radiation with properties similar to designed to reduce the danger of damage to TV visible light, including the invisible near-infrared and related units caused by lighting. The accessory “light” (or more technically correct, radiation) that provides a bypass directly to the ground for lighting carries signals in most fiber optic communication discharges that reach the antenna. LAs are usually systems. Light consists of electromagnetic waves installed in conjunction with outdoor antennas ordinarily applied to those having a wave length of mounted on the roofs of homes. from .000075 cm (the red ray) to .000038 cm (the lighting plot A diagram showing the position of all violet ray). lighting instruments in the TV production. light application bar During its TV transmission, a lighting ratio The brightness level of the fill-light com- film frame may be illuminated for only a part of each pared to the brightness level of the key-light, or the field scanning interval; whether or not this matters shadowy areas compared to the brightly lit areas; depends on the amount of storage, or memory, in measured as a ratio determined by the f-stop of the the telecine pick-up tube. The ratio of illuminated lens; a 1:2 ratio means that key is 1 f-stop brighter to unilluminated time is called the light application than fill; 1:3, a stop and a half; and 1:4, 2 stops. ratio or time, and is often expressed in angular de- lighting supervisor Controls and adjusts the lighting grees, 360 degrees representing lit frame. If the film in a TV studio. He/she assists the designers in draw- projection rate is not synchronized to the TV picture ing up the lighting plan for a production (i.e., a plan frequency, and if there is insufficient storage in the showing the type and position of the lamps) and telecine, it is possible for a horizontal black bar to oversees their setting by the studio electricians. He float up or down the TV picture. This light applica- sets the brightness to an approximately correct value tion bar is caused by the film frame not being illu- using a lightmeter and his monitor. The final adjust- minated during part of the active TV field scanning ments of brightness are done during rehearsal. intervals. light level meter An indicator on some video cam- light application time Time during which light is al- eras that indicates whether the subject has too little lowed to fall on a frame of film in a vidicon type of or too much light. film scanner. lightness of the color See Variables of perceived color. light biasing A technique employed in some video light spot scanner Flying spot scanner. cameras using a saticon tube to compensate for light-transfer characteristics Relationship between image retention. The saticon, claiming improved pic- light input and voltage output. ture resolution over the vidicon tube, tends to suf- light valve projection system A projection TV sys- fer from lag when the camera pans. Light biasing tem that operates by scanning a beam of electrons attempts to correct this by directing a light at the across reflectors or mirrors coated with an oil film. back of the sensitive faceplate. The electrons distort the surface of the oil, thereby Lightgate® Service A BellSouth optical fiber-based altering how the light reacts when it reflects off the private line service that allows high-volume custom- mirrors. The result of this action determines whether ers integrated voice, data and video transmission. the light reaches the screen directly or is transmit- Lightgate Service is the equivalent of 672 voice or ted through a diffraction grating. data, private line or dial up circuits. limited-play videocassette A type of videocassette lighting In video, any available, natural or artificial that can be rented and watched for a limited num- illumination. Standard indoor lighting includes a base ber of times before automatically erasing itself. It light, a key light, a fill light, a back light and an eye has a built-in counter that notes how many times it light. The base light, usually located over the sub- has been viewed and an internal magnet that erases

168 linear scan

the tape after 25 screenings. The consumer must linearity 1. In TV, usually refers to the geometric accu- pay for each viewing in a PPV type of strategy for racy of scanning. However, linearity is also some- home video. When the tape is returned, the counter times used to refer to the accuracy of gray scale shows if the tape has been played more than once, reproduction (linearity of the amplitude transfer char- and thus if any further charge is due. acteristic), but it is less confusing to use the word limiter Clipper, peak limiter. A circuit that limits the “gamma” for the gray scale characteristic. 2. A test- amplitude of its output signal to some predetermined ing procedure that measures the ability of a video threshold level. It can act on positive or negative source to reproduce a series of gray in a uniform swings or on both. (linear) pattern. The more linear the pattern of limiting resolution In video, the measurement of the shades, which range from black to white, the better resolution as determined by the maximum number the source’s ability to reproduce the original picture. of lines per picture height as registered on a test 3. Linearity refers to the horizontal and vertical con- chart. The limiting resolution of a TV picture is one trols that affect the “size” of TV image. For example, of its fundamental properties. the picture is enlarged so that it fills the screen with- line 1. The path covered by the electron beam of a TV out exhibiting lines above or below the image. 4. In picture tube in one sweep from left to right across A/D (Analog to Digital) or D/A (Digital to Analog), the screen. 2. Transmission line. 3. Trace. 4. See linearity measures the precision with which the digi- Time base error. 5. In film and TV, the area on a set tal output/input tracks the analog input/output. Lin- within which action occurs; also called action line, earity is typically measured by making the ADC or imaginary line, or axis of action. The camera gener- DAC attempt to generate a linearly increasing sig- ally is supposed to focus on the action and not cross nal. The actual output is compared to the ideal the the line. To down the line is to transmit a radio or TV output. The difference is a measure of the linearity. program to a station for internal use prior to broad- The smaller the number, the better. Linearity is typi- cast. cally specified as a range or percentage of LSBs (Least line amplifier In CATV, refers to amps inserted in the Significant Bits). cable at intervals to compensate for its attenuation. linearity chart See Video test chart. Their specifications are a key element in determin- linearity control A TV receiver control that varies the ing the performance of the system. Each amp in- amount of correction applied to the sawtooth scan- cludes an equalizer that compensates for the increase ning wave to provide the desired linear scanning of in cable attenuation with frequency. lines; lines appear straight, and round objects ap- linear actuator A TVRO antenna positioner. It con- pear as true circles. Separate linearity controls, sists of a motor, a set of reduction gears and a slid- known as the horizontal linearity and the vertical ing jack driven by either a reciprocating ball or an linearity controls, are usually provided for the hori- acme screw. The motor is generally mounted onto zontal and vertical sweep oscillators. It is also called the polar mount and one end of the jackscrew is distribution control. secured to the dish. The jackscrew can be mounted linear matrix transformation The process of trans- on either side of the antenna. This is determined by formation of a group of n signals by combining the the geographic location of the satellite system. When signals through addition or subtraction. It can be most satellites are in the western portion of the sky, used, for example, to convert RGB into YUV. See the jack is attached to the right rear of the antenna also Luminance/chrominance principle. as viewed from behind and vice versa. linear play Playback of a recorded sequence from start linear audio A method of placing the sound track on to finish without interactivity. videotape. Linear audio may be mono or stereo. linear program Program material on tape or disc that Another method of recording sound on videotape the viewer plays through from beginning to end. is diagonal recording—placing the audio track along Linear programming, such as films, plays, etc., is with the diagonal video track for better quality. See usually contrasted with interactive TV or interactive Linear stereo. videodisc in which segments of a program are en- linear editing Refers to a restrictive process of editing coded with a signal for easy access. tape by recording predetermined scenes in sequence linear quantization Audio sampling format used in on another tape. This meant that after the second digital audio processors. Usually 14 or 16 bits. tape was completed, any additional editing required linear recording Magnetic recording that uses bias- a third tape, and another generation loss of detail. ing to restrict operation to the linear portion of the This method has been replaced by nonlinear editing, demagnetization curve. It is required for recording in which information about different sequences is analog data, sound signals, and video signals. stored in memory until the final tape is made. If addi- linear scan A sweep of the electron beam in a CRT in tional changes are required, another tape can be pro- which the beam scans the screen with constant ve- duced without any generation loss by referring to the locity, usually by application of a sawtooth wave- stored memory rather than the edited tape. form to the deflection plates or coils.

169 linear stereo linear stereo The use of conventional, low-quality ers obsolete, whereas the latter does. The line dou- mono audio tracks, located near the edge of the bling process, which doubles the number of active tape, for the stereo audio signal. Linear stereo splits line scans on the screen, results in an image of higher the audio track into two, separating the pair with a density and greater stability. narrow guard band. In contrast to linear stereo, or line drive pulse The signal generated to control the linear track stereo as it is sometimes called, the su- horizontal blanking circuits. perior Beta or VHS Hi-Fi technique records the au- line filter In video, an electronic component, con- dio signal along with the diagonal video signal tracks taining one or more and capacitors, that for better sound reproduction. is placed between a transmitter or receiver and linear time-base oscillator A relaxation oscillator that the power line to prevent noise signals and other is used to generate a sawtooth waveform for use as interferences. a time base. line flyback Horizontal flyback. linear time counter A device to calculate tape run line frequency In TV, the number of horizontal sweeps time in VTRs. Since the counter works by detecting made by the scanning beam in 1 s. It is equal to the a control signal, accurate time display is maintained product of the number of lines per picture and the even through FF or REW operations. See Real-time picture frequency. In a twin-interlaced system such counter. as used by most TV services the picture frequency is linear time readout (LTR) Real-time counter. one half the field frequency. For example, in the PAL line-balanced converter Balun. 625-line system there are 50 fields per second and linebeat See Meshbeat. thus the line frequency is 625 x 50/2 = 15.625 kHz; line blanking Refers to the period of time that the in the NTSC 525-line system there are 59.94 fields scanning dot or spot takes to return from the end per second and thus the line frequency is 525 x of one line scan to the beginning of the next. The 59.94/2 = 15.734 kHz. dot moves from left to right as it scans each of 525 line-frequency blanking pulse Horizontal blanking lines, which form the NTSC standard. As it moves pulse. from right to left, the video camera emits no signal. line input terminals The audio/video input and out- This line blanking, or horizontal blanking as it is of- put jacks, usually found on the rear of VCRs, that ten called (since the scanning dot moves in a hori- are used for copying and editing. The direct line in- zontal direction), permits only the left-to-right put terminals are preferred for these operations over scanned information to be traced for a clear video the antenna connections, which may produce grain image. The line-blanking period in the NTSC 525- and color changes to the copied or edited video- line system is 10.8 µs, and in the PAL 625-line sys- tape. tem 12 µs. line interlace Interlaced scanning. line count The number of active scanning lines actu- line level impedance A low impedance signal of 600 ally used to carry the video picture signal; always ohms. Line matching transformers are used for less than total number of lines. matching the impedances of various components, line datum A reference time moment at the mid- such as a microphone to the input of a mixer. level crossing point of the leading edge of the line line-locked clock A design that ensures that there is sync pulse. This is the default timing reference in always a constant number of video samples per scan the TV environment (as opposed to the active line line, even if the timing of the line changes. start which is commonly used in computing envi- line microphone A directional mic with an acoustical ronments). Syn.: 0 h; line start [moment]; time transmission line in front of the transducer, often datum. with a pole at least 2 feet long. Commonly used in line dicing A scrambling technique, whereby lines are film and TV studios, it sometimes is called a shot- broken into pieces and sent to TV sets in random gun microphone. sequence. line pairs A measure of resolution often used in film line diffuser An oscillator within a TV monitor or re- and print media. In TV, lines are used instead, creat- ceiver that produces small vertical oscillations of the ing confusion when comparing film and video. spot on the screen to make the line structure of the line scan The rapid movement of the electron beam image less noticeable at short viewing distances. across the TV screen of the CRT. Different TV broad- line doubling An image enhancement technique, used casting systems have different numbers of line scans in video recording and applied to broadcasting, that per picture frame. The NTSC (American) standard improves picture quality. When projected, the im- requires one frame of 525 lines (actually two fields age almost equals that of 35mm film projection. of 262.5 lines each). These line scans are not to be Developed by French engineer Yves Faroudja, who confused with the lines of horizontal resolution. calls this technique Super-NTSC, the line doubling line-scan pickup device A type of solid-state video system was intended to be a strong competitor of pickup device which electronically scans only in one HDTV. The former does not make present TV receiv- direction. Scanning in the other direction is accom-

170 load

plished mechanically by relative motion between the the scanning spot so that it starts to scan each new pickup device and the image. line at exactly the right moment. line-sequential color television A color TV system lining In videotex, a display of alphanumeric charac- in which each of the video signals (R,G, and B) is ters with an underline that is considered to be part transmitted in turn for the duration of one entire of the shape of the characters. Mosaic characters scanning line. Used in SSTV. and line drawing characters are displayed in sepa- line shuffling 1. A TV scrambling technique in which rated fonts. individual lines are sent in random order. 2. See lip sync Lip synchronization. Bandwidth reduction (EUREKA-95 HDMAC system). lip synchronization A technique used in TV and film line start [moment] A reference time moment at the production, that matches the voices of performers mid-level crossing point of the leading edge of the speaking or singing with their lip movements. Also line sync pulse. This is the default timing reference called lip sync. See also Mime. in the TV environment (as opposed to the active line liquid crystal An organic compound that has a liquid start which is commonly used in computing envi- phase and a molecular structure similar to that of a ronments). Syn.: 0 h; line datum; time datum. solid crystal. The liquid is normally transparent, but line store A memory buffer used to hold one line of it becomes translucent (almost opaque) in localized video. If the horizontal resolution of the screen is areas in which the alignment of the molecules is 640 pixels and RGB is used as the color space, the distributed by applying an electric field with shaped line store would have to be 640 locations long by 3 electrodes. Liquid crystals have three phases: nem- bytes wide. This amounts to one location for each atic, smectic, and cholesteric; the nematic phase, in pixel and each color plane. Line stores are typically which the elongated molecules are lined up in one used in filtering algorithms. For example, a comb direction but are not in layers, is most commonly filter is made up of two or more line stores. The used in LCDs. DCT used in the JPEG and MPEG compression algo- liquid crystal display See LCD. rithms could use eight line stores since processing is live 1. Broadcast directly at the time of production, done on blocks of 8x8 pixels. instead of from recorded or filmed program mate- line sync signal In TV, the signal transmitted at the rial. 2. Syn.: alive. See Dead. end of each scanning line to initiate horizontal live camera See Camera categories. flyback of the scanning beam in receivers, so keep- live chassis A radio, TV, or other chassis that has a ing the scanning at the receiver in step with that at direct chassis connection to one side of the AC line. the transmitter. In most TV systems the signal con- For safety, a live chassis must be completely enclosed sists of a single pulse from blanking level to sync by an insulating cabinet. level, the leading edge of which locks the receiver live-streaming Streaming media that is broadcast real- line time base. Also called horizontal synchronizing time to many people at a set time. pulse. LL CATV hyperband channel, 366-372 MHz. See TV line tilt A TV picture distortion. Comparable with field channel assignments. tilt, line tilt is a gradual increase or decrease in the LNA Low Noise Amplifier. In satellite TV, a device that DC component over the course of the line wave- receives and amplifies the weak satellite signal re- form, owing to AC coupling or the addition of hum flected by an antenna via a feedhorn. C-band LNAs or other spurious low-frequency signals. Usually the typically have their noise characteristics quoted as amplitude is less than that caused by frame tilt, as noise temperatures rated in degrees Kelvin. K-band there is less time for the line waveform to take up LNA noise characteristics are usually expressed as a the new potential. The effect can be reduced by noise figure in dB. passing the signal through a keyed, or line-by-line LNB Low Noise Block downconverter. In satellite TV, a clamping circuit, thus restoring the beginning of each low noise microwave amp and converter which line to the same potential with respect to earth. The downconverts a block or range of frequencies at visual effect is that of a gradual increase or decrease once to an IF range, typically 950 to 1450 MHz or in brightness from left to right of the viewed TV 950 to 1750 MHz. image. LNC Low Noise Converter. In satellite TV, an LNA and a line time base 1. The circuits responsible for generat- conventional downconverter housed in one weath- ing the signals causing horizontal deflection of the erproof box. This device converts one channel at a scanning beam. In modern TV receivers the line out- time. Channel selection is controlled by the satellite put stage generates, in addition to the line scan- receiver. The typical IF for LNCs is 70 MHz. ning current, a direct voltage to boost the supply to LO 1. Local Oscillator. 2. Local Origination. the output stage, the heater supply for the picture load 1. To place a reel, disc, cartridge, or some other tube, the EHT supply for the picture tube and possi- type of recording media into a machine that extracts bly a low-voltage supply for early stages in the re- the stored data or the audio or video content. 2. To ceiver. 2. The control of the horizontal deflection of place a termination across a video or audio line.

171 local area data transport local area data transport (LADT) An electronic net- quadrature-grid detector for strong signals and as a work for data delivery among videotex systems. locked-oscillator detector for relatively weak signals. local area network (LAN) A network designed to pro- Some TV sets include it. vide facilities for inter-user communication within a locking The process by which an oscillator can be syn- single geographical location. Contrasted with wide chronized at the frequency of a signal applied to it. area network (WAN). locking up The brief period when a videocassette local color The normal or true color of an object, in wobbles as it starts to play, before it is stabilized ordinary daylight. and runs smoothly. local origination (LO) One of the main attractions of lockup The more precise we can make the VTR’s play- CATV systems is locally originated programming. back speed, the less time base error will be created. These channels can only be obtained by cable sub- When the machine gets up to full speed and every- scribers and not from any system satellite or other- thing is as stable as it is going to get, we say the wise. Earlier cable systems usually designated one machine is “locked up.” There are several degrees channel containing programming from a cable of lockup (capstan lock, vertical lock or capstan servo, operator’s own studio facility. That was simply known frame lock, horizontal lock) and each additional step as local origination and programs consisted of local adds a little more stability. interest subjects. Later cable operators added alpha- log A written record of radio and TV station operating numeric channels containing printed messages of data, required by law. community interest and/or classified ads. logarithmic amplifier Used in 3D TV systems to form local oscillator (LO) The oscillator in a superhetero- the depth video signal. dyne receiver; its output is mixed with the incoming logging The initial stage in video editing in which all modulated RF carrier signal in the mixer to give the raw footage is listed by time code location, shot lower frequency needed to produce the IF duration, and the quality of the scene. signal. long form A TV station with a format of mostly movies local pickup A condition in a TV receiver or a VCR in and other long programs. which the internal tuner substitutes as an antenna, Longitudinal Videotape Recording (LVR) A pioneer producing ghosts on the TV screen. Good shielding reel-to-reel videotape format; Enter- of the tuner minimizes local pickup. VCRs are usu- prises, 1951. It operated on the principle of record- ally free from this anomaly. ing electrical signals on narrow magnetic tape, which location An actual setting, as distinct from a studio, moved rapidly over stationary recording heads. The used for a film or TV show. The location manager is tape had to move 100 ips over the heads, however, the person who finds sites for shooting outside the and the resulting black and white image had poor studio, with the assistance of location scouts, and resolution and produced jitter. The LVR-type of re- who then makes arrangements for the use of these cording/playback was bypassed for professional use sites. by the quadruplex (quad) videotape recording location manager A member of a film or TV produc- system in 1956. tion staff in charge of the logistics of a shooting Longitudinal Time Code (LTC) SMPTE/ANSI time code outside the studio. The location manager sometimes format that is recorded into an audio track or sepa- also serves as a location scout. rate track (such as the cue or address track) on a location scout In film and TV, a member of the pro- videotape. Time codes are digital addresses that dis- duction staff who finds off-studio sites and arranges tinguish each frame, thus permitting access to it. for accommodations, permits, and other arrange- LTCs are written longitudinally, as opposed to video ments prior to the shooting. information and some audio information, which are lockbox A device that allows cable subscribers to block recorded diagonally. See SMPTE/ANSI frame coding. out reception of a particular channel at any given longitudinal video recording See LVR video record- time. It is installed at the back of a TV set and con- ing system. tains a trap that can be activated by a key. Such a long lens A high focal length lens with a long barrel; box protects those who do not want to receive what performs function similar to the telephoto lens with- they consider to be objectionable, obscene, or in- out the advantage of that lens’ shorter barrel. decent programming. long shot A camera angle of view taken at a distance locked When a phase lock loop (PLL) is accurately pro- and including a great deal of the scene area. ducing horizontal syncs that are precisely lined up long take A film or TV camera shot maintained for an with the horizontal syncs of the incoming video extended period. source, the PLL is said to be “locked.” When a PLL is look-up table (LUT) Same as color table. locked, the PLL is stable and there is minimum jitter loop A closed path or circuit over which a signal can in the generated sample clock. circulate, as in a feedback control system. See PLL. locked-oscillator quadrature-grid FM detector An See also Processor loop. FM detector that functions as a directly driven loop filter A filter used in a PLL design to smooth out

172 low power television

tiny bumps in the output of the phase comparator which identifications and other captions generally that might drive the loop out of lock. The loop filter are displayed. helps to determine how well the loop locks, how lower-third Ids Names, titles, and station logos, used long it takes to lock and how easy it is to knock the on TV news programs and talk shows to identify loop out of lock. on-air personalities, their guests, programs, and sta- loop-through connection, satellite TV A connec- tions. tion to enable a satellite receiver to accept a video lower-third super Refers to text superimposed on the source other than the output of its own demodula- lower third of the video screen, the most common tor. The alternative video source is then routed to place for titles. the satellite TV receiver’s demodulator. It is also pos- low gamma See Gamma. sible to route the audio in this fashion. The source low-level lighting A scene illuminated with under 50 selection is determined by pin 8 on the SCART con- ft-c of light; often results in a poor signature-to-noise nector. The voltage on this connector is high, 12 ratio and/or poor constant ratio in the Vdc, when the descrambler is in operation. When it recorded picture. is low, the receiver selects internal video. For Sakura low light lag A blurring, image-retention effect, which receiver, the reverse of the normal situation applies. occurs when a vidicon tube is operating in insuffi- For decoder video to be selected, pin 8 must be low. cient light. Many of the recent descramblers have provisions for low light sensitivity A video camera feature that helps such receivers. In cases where there is no provision to produce clear, detailed images. The lux rating af- for such reverse switching, a separate lead must be fects the low light sensitivity of a camera. The lower connected. the number, the less light that is needed. Advanced loop-through jack A feature found in TV monitors video cameras with high-speed shutters require low that permits several monitors and VCRs to be hooked lux numbers or low light sensitivity to ensure good up to the same signal source. A panel switch on the screen pictures. rear of the monitor selects either high input imped- low noise amplifier (LNA) The component of a satel- ance or 75-ohm impedance. The first is used when lite TV system that is mounted inside the feeder horn the set transmits its signal to other units while the assembly of an antenna and is designed to amplify 75-ohm setting is used when the monitor is the fi- the signal it receives from the dish before it reaches nal set in the series. Some more expensive indus- the satellite receiver. The effectiveness of an LNA is trial-model character generators offer this feature. measured by how much gain it gives to the incom- lo-pass filter Low-pass filter. ing signal and by its noise-temperature rating. Al- lossless A term used with image compression. Lossless though the antenna itself increases the signal sent image compression means the decompressed im- to it, the LNA should boost it more by 50 dB of gain. age is exactly the same as the original image. A lower noise-temperature rating means less noise; lossy A method of image compression, such as JPEG, some amplifiers provide a number of 120 degrees, in which some image information is lost each time which is considered good. the file is compressed. low noise block (downconverter) A device to amplify louma A crane, with a camera mounted on it, that and downconvert microwaves from the parabolic can be controlled from a distance (with a TV camera antenna to the UHF band (in satellite receivers). and a monitor to enable the camera operator to see low-pass filter 1. A filter that transmits alternating what the mounted camera is filming); also called currents below a given cutoff frequency and sub- Loume crane. The device was developed in France stantially attenuates all other currents. 2. A device in the 1970s by Jean-Marie Lavalou and Alain often employed on two-way cable systems to re- Masseron; the name comes from syllables in their strict the flow of high frequency information while last names, lou and ma. permitting the passage of low frequency informa- low-angle shot A shot in which the camera points tion. Also written as lo-pass filter. See Filter. upward toward the subject. low power satellite Satellite with transponder RF low band The band that includes TV channels 2 to 6, power below about 30 W. extending from 54 to 88 MHz. low power satellite TV Refers to satellite TV systems low-band tape Videotape with inferior resolution to which broadcast within the 4-6 GHz C-band. To re- that of high-band tape. ceive this low power signal, the earth station, or re- low-electron-velocity camera tube Syn.: cathode- ceiving base, requires a large dish (a parabolic or voltage-stabilized camera tube. See Camera tube; spherical antenna) usually 10 to 15 feet in diameter. Image orthicon; Vidicon. low power television (LPTV) A system of broadcast- Lowell light A small, lightweight, portable lighting ing that permits thousands of local stations to broad- unit made by the Lowell Company. cast within a radius of 10 to 20 miles. LPTV is lower sideband See Carrier wave. accomplished by limiting VHF stations to 10 W of lower third The bottom third of the TV screen, on power output and UHF stations to 1,000 W. These

173 lows

channels are subject to fewer regulations than con- oring information for the image. However, because ventional ones and in part serve local communities, a tri-stimulus color system requires three indepen- minority groups, colleges, etc. Basically a line-of-sight dent signals for complete representation of all col- medium (the flatter the terrain, the larger the radius ors, the chrominance signal is actually two signals of the low power signal), LPTV was given a boost in — called color differences. Luminance and chromi- March of 1982 when the FCC approved a set of final nance are just one of the many possible combina- rules governing the 4,000 anticipated new stations. tions of three signals which could be used to transmit lows The deeper sound tones, such as bass, or the less color information. They are obtained by a linear assertive colors, such as whitish-gray. matrix transformation of the RGB signals created in low-velocity scanning See Scanning. the camera. The matrix transformation simply means low-z See Impedance. that each of the luminance and chrominance sig- loyalty index A measure of the frequency of nals is an additive (sometimes with negative coeffi- listenership or viewing of a radio or TV station. cients) combination of the original RGB signals. In a LP-speed The middle speed (Long Play) of a three-speed linear transmission system there are an infinity of VHS format VCR. With a standard T-120 videocas- possible matrix transformations that might be used; sette, LP records and plays back for four hours. The the correct inverse transformation must be used other two speeds are SP (Standard Play), which records when RGB signals are recovered to display on a color for 2 hours and EP (Extended Play) or SLP (Super Long monitor. Play), which provides up to six hours of recording time. luminance delay line in gyrator technique An IC Some machines no longer record in the LP mode but which substitutes the conventional Y-delay line in do offer it in playback only. These VCRs, usually con- older color TV receivers. It is consists of gyrator de- taining four heads, optimize two for SP speed and lay cells. Some cells are switchable to vary delay the remaining two heads for EP mode. times. LPTV Low power television. luminance flicker Flicker that results from fluctuation L-R signal See Multichannel television sound. of luminance only. L+R signal See Multichannel television sound. luminance key A key whereby the hole being cut is LSB Least significant bit. The bit that has the least value determined by brightness of the video source. in a binary number or data byte. In written form, luminance noise Refers to a type of video interfer- this is typically the right-most bit. ence which influences both black and white and LTC Longitudinal Time Code. color signals. Luminance noise is listed as a number LTR Linear Time Readout. in specification sheets of components and in test luma The brightness signal in a video transmission. reports. It differs from chrominance noise, which lumen (lm) Unit of luminous flux. Quantity of light affects only color. emitted per second in unit solid angle, by a uniform luminance noise reduction A special electronic cir- point source of light of 1 candle intensity. Used cuit designed to reduce unwanted noise or interfer- chiefly in reference to the light output of front pro- ence in the brightness signals, thereby producing jection TV systems. For instance, front projection TVs brighter whites and more intense blacks. Luminance whose light output measures 300 lm or better are noise reduction usually is part of the circuitry of many considered excellent. Rear projection TV uses the video processing chips. term “peak brightness level” instead of “light out- luminance reversal See Image reversal. put” and it is measured in footlamberts, the num- luminance signal The color TV signal that has exclu- ber based on a surface that emits one lm per square sive control of the luminance of the picture. For SDTV, foot. it is made up of 0.299 red, 0.587 green, and 0.114 luminaire A floodlight fixture, including the lamp, re- blue and is capable of producing a complete black flector, support, housing, and cable. and white picture. It is also called the Y signal. luminance In an image, refers to the brightness val- luminant A light source. ues of all the points in the image. A luminance-only luminary A lighting source or instrument, including reproduction is a black-and-white representation of the bulb and other parts. the image. Luminance is important in judging pro- luminescence The emission of electromagnetic radia- jection TV systems, TV receivers, etc. tion from a substance due to a nonthermal process. luminance carrier Picture carrier. luminescent panel Display device. A flat luminescent luminance channel A path intended primarily for the surface is divided into a multitude of individual cells, luminance signal in a color TV system. which become the pixels. Each cell emits light as luminance/chrominance principle This principle says the result of electrical or optical excitation. that any color signal may be broken into two parts— luminophore Syn.: phosphor. luminance, which is a monochrome video signal that luminocity of the color See Variables of perceived controls only brightness or (luminance) of the im- color. age, and chrominance, which contains only the col- LUT Look-up table.

174 lx lux (x) A measurement of light used in relation to the costly. It accommodated 1/2-inch tape in a special sensitivity of video cameras. 1 footcandle (fc) equals cartridge. The LVR system, the first attempt at video 10 lux. Thus the sensitivity (the minimum amount recording, was simply an accelerated version of an of light needed to produce a usable image) of a cam- audio recorder. era may be rated at 50 lux (5 fc). The lower the lux LV videodisc system (LaserVision) One of two major number, the lower the lighting conditions the cam- types of machines that play back records containing era can handle. Lux is the measurement recom- pictures as well as sound on a standard TV receiver. mended by the International System of Standards. The LaserVision player uses a highly reflective LV 1. Laser-optical disc system. The Magnavox video grooveless disc which is “read” by a small laser beam. disc. 2. LaserVision. An optical videodisc, made by In its standard speed (30 minutes per side) the player Philips, of Holland. provides such various sophisticated functions as ran- LVR Longitudinal Video Recording. dom access to chapters and frames, freeze frame, LVR video recording system A now-defunct video visual scan, etc. Because the system employs a laser, recording system which passed tape at a high speed the disc is virtually indestructable. The laser tracks over a fixed recording/playback head. Introduced in from the inside of the disc to the outside, but never 1979 by Toshiba and BASF, the Longitudinal Video makes contact with the surface of the disc. The LV Recording (LVR) process played 220 parallel tracks player has two speed modes: CAV, which is its stan- of audio and video signals on tape that was magne- dard speed (30 minutes), and CLV with an extended tized along its length, hence its name. Because of play of one hour. its stationary head design, the machine was less lx Abbreviation for lux.

175 M

M 1. Magenta (also m). 2. CATV superband channel, macro focus Extremely close focus—e.g., 4 mm from 234-240 MHz. 3. TV standard; Brazil, Canada, Chile, the front lens of a video camera. Columbia, Cuba, Japan, , Netherlands macro lens A magnifying lens designed to focus very Antilles, Panama, Peru, , US. Characteris- close to the subject. Macro lenses are particularly help- tics: 525 lines/frame, 60 fields/s, interlace—2:1, 30 ful in nature work and hobbies involving stamps, coins, fr/s, 15,750 lines/s, aspect ratio—4:3, video band— models, etc. The lens for close-up focusing is found 4.2 MHz, RF band—6 MHz, visual polarity—nega- on most video cameras. Most macro lenses also serve tive, sound modulation—F3, pre-emphasis—75 µs, as a normal lens when not in the macro mode. deviation—25 kHz, gamma of picture signal—0.45. macro mode An alternate function of a dual-purpose 4. Recording method—see M format. 5. Mature— lens that can take extreme close-ups of different tiny see Movie rating systems. objects. MII component system A professional/industrial macro video The use of extreme close-ups with the 1/2" tape-recording format that provides full NTSC macro part of a video camera’s zoom lens. Standard bandwidth. Features include 90-minute recording on most new quality video cameras, the macro fea- time, field color playback, a built-in digital time base ture permits focusing as close as an inch or two from corrector, time-code reader/generators, four audio the subject which fills the TV screen. Macro shoot- channels, composite and component video inputs ing provides a very narrow depth of field (that which and outputs, and several advanced editing capabili- is in focus in front of and behind the subject) so that ties. The MII VTR can be integrated with other for- focusing becomes extremely critical. Also, any slight mats, including S-VHS, 1", U-Matic, Beta and movement becomes highly visible on the screen. Beta-SP. Working in conjunction with a professional Therefore, a good tripod is recommended. If a cam- digital video camera, the MII system permits the era is not equipped with a macro lens or the zoom 1/2" cassette recorded in the field to be loaded di- feature (which disengages in the macro position) is rectly into a studio recorder for studio-level results desired, the video camera user may add a special that compete favorably with the 1" C format. series of close-up lenses. These are measured in di- MAC (A-, B-, C-, D-, E-, F-) Multiplexed Analog Com- opters, such as +1, +2, etc. Kits are available with ponents color system, where the video signal is di- various diopter lenses. vided into three components: luminance signal, R-Y Macrovision A system designed to prevent casual signal and B-Y signal, which are compressed for se- copying of prerecorded tapes and DVDs in the home. quential relay over one TV scan line. The concept of the Macrovision anticopy process is MacBeth color checker A color rendition chart used relatively simple. Electrical pulses of specific strength by film and broadcast engineers to help determine and duration are added during selected portions of the color accuracy of film and video images. It has the video signal. The Macrovision pulses are placed become the industry standard for checking color in the vertical blanking interval (VBI) and designed accuracy in film, video, and graphics. to upset the AGC in a recording VCR. macroblock In the typical picture representation used made-for Referring to a production created for a spe- by MPEG, a macroblock consists of four 8 x 8 blocks cific medium, such as a made-for-TV movie or a of luminance data (arranged in a 16 x 16 sample made-for-home-video movie. array) and two 8 x 8 blocks of color difference data mag Short for magnetic, referring specially to cards, (assuming 4:2:0 format), which correspond to the tapes, disks, or any recording and storage medium— area covered by the 16 x 16 section luminance com- e.g., mag card or mag track. ponent of the picture. The macroblock is the basic magenta (M or m) A red-blue color obtained by mix- unit used for motion-compensated prediction. ing equal intensities of R and B light. It is also the macro close-up A mode that is used for close-up shots correct name for the subtractive primary color usu- of small objects or photos. ally called “red.”

176 masking magic hour A time of day, particularly dawn or dusk, management command In videotex, a parameter that is the ideal period to photograph a scene on a value P followed by a command identifier C that TV remote or on a film location. There is little need represent a presentation level management action, to adjust the lighting or camera f-stops at that time such as a change from one data syntax to another. because the color temperature is nearly perfect for manual editing Editing that is completely done by a the conditions of the shoot. It is the brief period person without using an electronic editing when sunlight produces a special quality—magical, controller. surrealistic, poetic. manual focus A video camera function that allows magnetic coercivity Coercivity. the user to override the autofocus feature. Manual magnetic deflection Deflection of an electron beam focus provides several uses. Camera owners may by a magnetic field, as in a TV picture tube. prefer this mode as a means of extending battery magnetic focusing Focusing an electron beam life, which is affected by continuous use of autofocus through the action of a magnetic field. and other automated features. In addition, manual magnetic head The electromagnet for reading, re- focus permits the user to add individual creativity to cording, or erasing signals on a magnetic disc or his or her work by producing special effects, such as tape. out-of-focus fades or scene transitions. magnetic lens A lens that has an arrangement of elec- manual interval time lapse mode A video camera tromagnets or permanent magnets to produce mag- feature that permits the camera user to add anima- netic fields that focus a beam of charged particles. tion effects. The operator accomplishes this by press- magnetic recording Capturing audio and video fre- ing the pause mode, then slightly moving the object quencies by magnetizing areas of tape that can be that is being recorded, and finally pressing the record played back by moving them past a head where the button. The process is repeated until the entire cycle magnetized areas are reconverted into electrical of desired movement has been completed. Many energy. video cameras provide an automatic time lapse magnetic tape The medium used for recording and feature. playback on tape recorders. The most popular width manual iris control A video camera function that of consumer tape is 1/4" while industrial tape may permits the user to manually control the amount of be 1/2", 3/4", 1" or 2". light that enters the camera lens. Manual iris con- magnetic tape developer A special chemical solu- trol is sometimes described as exposure control. tion applied to the control track edge of video tape manual white balance A video camera function that to make control pulses visible to the eye and thereby permits the user to control the way the camera views allow precise cutting of the tape between pulses; different colors. This is important in maintaining necessary for physical tape editing. correct color when various light sources produce magneto-optical effect See Kerr effects. changes in the color mix, or color temperature. magnification change command In 3D-image dis- marker generator An RF generator that injects one play systems, an instruction that provides for con- or more frequency-identifying pips on the pattern trol of a special driver so that the image can be produced by a sweep generator on a cathode-ray stereoscopically observed from a position of the des- oscilloscope screen. It is used for adjusting response ignated distance. curves of tuned circuits, as when aligning FM and main title Title which gives the name of a TV program. TV receivers. makeup The command “makeup!” on a television marker pip An identifying mark on a CRT display. set is a request to apply cosmetics, generally a markers In videotex, flags in a memory to show where touchup of powder by the makeup department attribute controls have been set. They are associ- (headed by the makeup artist). ated with the leading edge of the character MAMA The Media Asset Management Association. position. MAMA serves as an advanced user group and inde- Martin A family of amateur SSTV transmission modes pendent international industry consortium, created developed by Martin Emmerson, G3OQD, in by and for media producers, content publishers, tech- England. nology providers, and value-chain partners to develop mash See Multi-stage noise shaping. open content and metadata exchange protocols for mask In video, refers to the device mounted in front creation and asset management. of a TV picture tube to limit the viewing area of the MAN Metropolitan Area Network. High speed intra- screen. The mask is sometimes referred to as a frame. city data network. Typically extends as far as 50 km, masking A term employed in the Dynamic Noise Re- operates at speeds from 1 Mbit/s to 200 Mbps and duction system referring to the capability of a pro- provides an integrated set of services for real-time gram to conceal its background noise. DNR utilizes data, voice and image transmission. Two standards a special dynamic filter which eliminates high fre- are involved with MANs: IEEE 802.3 and ANSI quencies (mostly in the form of hiss or noise) when- X3T9.5. ever the signal is not strong enough to cover the

177 mass media

hiss. But when the signal does “mask” or cover this master volume control An audio term, most often noise, the filter permits the high frequencies to pass used with mixers and amps to denote the final over- through. all volume control of signal level. mass media Forms of communication that reach large match cut A quick transition, or cut, from one film or audiences, such as newspapers, magazines, radio, TV camera to another, or a smooth transition from and TV, in contrast to newsletters or other media one shot to another, with the action appearing to that are more specialized. Media is the plural of continue seamlessly. medium. match dissolve (MD) A film and TV technique in which master 1. In video, an original recording on disc or tape a shot fades, or dissolves, into another of similar from which copies may be made. See also Slave. 2. form or action, often to suggest the passage of time. In I2C-bus system, the device which initiates a trans- matching transformer A transformer used between fer, generates clock signals and terminates a transfer. unequal impedances for matching purposes, to give master-antenna television (MATV) An antenna sys- maximum transfer of energy. In video, a circuit that tem that consists of an antenna array capable of changes the impedance of a TV signal, often from receiving available broadcast signals and amplifying 75 ohms to 300 ohms and vice versa. See also Im- them as required for distribution over coaxial cables pedance adapter, Balun. to a number of individual TV receivers that are nor- matrix 1. The section of a color video encoder that mally within a single home, apartment, hotel, mo- transforms the R,G, and B camera signals into color- tel, or other other building. difference signals and combines them with the master brightness control A variable resistor that chrominance subcarrier. It is also called a color coder, simultaneously adjusts the grid bias on all guns of a color encoder, or encoder. 2. The section of a color 3-gun color picture tube. video decoder that joins the color-difference (NTSC master control operator (MCO) Operator of the con- — I,Q; PAL — V,U; SECAM — R-Y,B-Y) and Y signals trols that switch inputs from studios, videotape re- and converts them into R,G, and B signals needed producers, , etc., to one or more outputs. to drive the color picture tube. It is also called a color He/she not only has to switch the signals correctly, decoder or decoder. but must maintain levels of picture and sound, and matrixing 1. The process of performing a code con- also the quality of sync pulses, black/peak-white version with a matrix, as in converting color video level, etc. In some set-ups, the switching function is signal components from one form to another. 2. The taken away to a separate presentation control or is conversion of a master videotape into a glass laser automated, leaving the MCOs with a supervisory videodisc master. A heavy-duty laser beam etches function. These operators have roughly the same microscopic pits into the surface of the disc, which knowledge and skills as camera control operators, is then used as a master to produce the videodisc who do a very similar job. stamper. master gain control 1. A variable resistor or potenti- matrix surround A surround-sound system similar to, ometer on a stereo amp that controls the gain of but not as sophisticated as, Dolby Surround. both audio channels simultaneously. 2. A control in matrix transformation In analog color video, the a radio, TV, or recording studio that changes the process of converting the color signals from one tri- overall audio output level without affecting the mixer stimulus format to another, as, for example, RGB to controls that determine the balance of the micro- YUV. phones and other sound sources. It can fade out or matrix wipe A special effect designed to tessellate a fade in the sound volume. video image. A mix/effects switcher is used to pro- mastering In optical recording, the original optical duce this effect as well as to change the picture in recording process. each square in a seemingly random pattern. master monitor High-quality monitor equipped with Matsushita A Japanese company that is one of the such facilities as picture focus, internal and external world’s largest manufacturers of industrial and con- sync, and horizontal and vertical scanning controls. sumer electric and electronic products. It produces master picture monitor A precision monitor placed some of the most familiar audio and video gear un- at a key point in the control system and providing der the brand names Technics, Quasar, Panasonic, the operator with his main source of information. and JVC. Generally the monitor can be switched to several matte A film term sometimes used in video produc- points in the circuit to check the functioning of the tion work to denote a keyed effect, an insert of video apparatus. Both picture and waveform monitors are signal information keyed from one source into a used in this role. second video signal. master VCR The VCR deck or machine which plays matte key A luminance key where the hole created the tape during the duplicating process onto one or by the key is filled with artificially created color from more slave machines (or VCRs doing the the switcher. For example, using a matte key, the recording). hole in camera 1 could be filled with blue, even if

178 medium power satellite TV

the original key source was black and white. The ing, and 100 units of picture information above the hole can also be filled with a third source — video horizontal blanking level. In a properly setup NTSC from a third camera, for example. receiver, the video output should look as follows: mature audience In film and TV, an audience for which The horizontal sync extends from -40 IRE to 0 IRE. sexual, violent, or other adult material is considered The color burst extends equally above and below appropriate. the 0 reference blanking line +20 and -20 IRE. The MATV Master-Antenna Television, or private cable. See white level is at 100 IRE. This signal level equals 1- also SMATV. Vpp into a 75-ohm load. In PAL and SECAM sys-

maximum frequency blue +fB = 4 480.000 kHz tems, the corresponding levels are 0.3 V sync and (SECAM). 0.7 V white level. maximum frequency red +fR = 4 686.000 kHz mechanical laser projector A projector using vibrat- (SECAM). ing or rotating mirror assemblies. Used in 3D TV sys- maximum usable luminance This measures, in tems; to synchronize the rotational rate of each of footlamberts, the amount of brightness a TV moni- the mirrors, the horizontal scan voltage and the ver- tor can produce before picture distortion, or “bloom- tical scan voltage from the raster scan generator of ing,” appears. Direct-view sets typically measure the TV camera are input to the laser projector. between 75 and 100 footlamberts. Because of their The primary technique used size, projection sets usually need to exceed 100 in TV experimentation until the 1930s. It was first footlamberts for a good picture. developed in the 1800s. Based on the principle used Mbone Multicast backbone, a virtual network made in the Nipkow disc. The images produced by me- up of portions of the Internet in which multicasting chanical television systems usually only contained has been enabled. The Mbone originated from IEFT, 30 to 60 scanning lines and were therefore dim and in which live audio and video were transmitted blurred. In the 1930s, a hybrid mechanical-electronic around the world. The Mbone is a network of hosts system and later an all-electronic system replaced connected to the Internet communicating through mechanical television. IP multicast protocols, multicast-enabled routers, and mecomete See Kerr effects. the point-to-point tunnels that interconnect them. media It is the plural of medium, though increasingly MCA/Disney vs. Sony lawsuit The famous case in the popular usage is only of the collective noun. 1. which Universal City and Walt Disney filed suit in In the context of telecommunications, media is most 1976, charging that Sony and others, by selling often the conduit or link that carries transmissions. VCRs, damaged the studios financially and infringed Cable and home video are often referred to as the upon copyright laws. The first major decision con- “electronic media.” Transport media include cop- cerning this case occurred on October 1, 1979, rul- per wire, radio waves and fiber. Media such as broad- ing in favor of Sony. Then, in October of 1981, an cast TV that are designed to reach the maximum appellate court reversed the decision in favor of the number of people are called mass media. When plaintiffs. The Supreme Court heard the case and in more than one medium is used to simultaneously 1984 overruled the reversal and ruled in favor of reach an audience, the term multimedia is used. Sony. The suit has many ramifications for studios, 2. Gel. equipment and tape manufacturers as well as the media engine The CPU or DSP processor that coordi- general public. nates all of the video and audio activities in a multi- MCT algorithm A compression algorithm introduced media platform. The media engine is used to in 1986 by PictureTel. MCT reduced the bandwidth coordinate the audio with the video, control mul- necessary to transmit acceptable picture quality from tiple inputs, and control the compression and de- 768 to 224 Kbps making two-way video- compression hardware. The media engine is most conferencing convenient and economical at relatively likely not the host CPU—for example, not the 80486 low data rates (for those times). processor on the PC motherboard. MCU Multipoint Control Unit. A PBX-like device for media server A new term for a file server on a local switching and conferencing video calls, announced area network that contains files with voice, images, by AT&T on 22 March, 1993. pictures, video, etc. In short, a media server is a re- MD Match Dissolve. pository for media of all types. MDS Multipoint Distribution Service. medium See Media. mean picture level The mean (d.c.) level of the video medium-close shot (MCS) A picture or scene with signal. the camera between a position close to the subject measuring the video NTSC video is commonly mea- (close shot) and a middle position (medium shot). sured by a system designed by the IRE (Institute of medium power satellite Satellite with transponder Radio Engineers). In this system, a 1-Vpp video sig- RF power in the region of 30 to 100 W. nal is divided into 140 IRE units. The 140 IRE units medium power satellite TV Refers to a bandwidth are broken down into 40 units of horizontal blank- of 11.7-12.2 GHz and requires a 4-foot wide an-

179 medium shot

tenna. Although this system is less costly than low- signed to store dozens of complete set-ups. In addi- power satellite TV, it is severely limited as to the num- tion, the memory controlled effects remembers tran- ber of channels it can handle (currently, about four). sitions previously put into production. Medium power satellite TV is similar to direct broad- memory pause Refers to a videodisc player that has cast satellite that uses a different bandwidth and a the capability of stopping a program at an exact point smaller-diameter antenna. and then continuing to play the disc from that same medium shot Camera angle of view between close- point. This feature is helpful to those viewers who up and long shot; a view of the head and shoulders are often interrupted by telephone calls and other of a subject, as opposed to head only (close-up) or similar disturbances. full body (long shot). memory rewind A feature on some older-model VCRs, megabyte (Mbyte) One million bytes (actually which, when pressed, stops the tape during Rewind 1,048,576); one thousand kilobytes. or FF when the index counter reaches 000 (or 0000 membrane keyboard A keyboard constructed of two on some machines). Memory rewind works in con- thin plastic sheets (called membranes) that are junction with the tape counter and is useful in lo- coated with a circuit made of electrically conductive cating a pre-selected portion of the tape for replay. ink. The keyboard is sensitive to touch. It is an eco- This feature is different from electronic program in- nomical, flat type used in several early microcom- dexing. puters. Today, such keyboards are also used on TVs menu A feature, usually found on consumer equip- and VCRs. ment, that displays on screen a vast choice of oper- memory In video, a digital VCR feature that permits ating options that the viewer activates by way of the viewer to lock in a still picture from a TV broad- the remote control. There are programming menus cast. In addition, the picture, which usually appears to make it easier for the user to set the time, day in a corner of the TV screen, can be stored in memory and channel of programs to be recorded. Setup until the VCR power is turned off. This feature is menus help the new owner of a TV set make the sometimes listed as TV memory or TV memo. proper wire and cable connections. Other menus memory backup Refers to the capability of a VCR, include audio functions, such as adjusting bass and TV, or other equipment, to retain its programmed treble, and video functions, such as controlling sharp- instructions and other timer functions in the event ness, contrast and color. of a power failure. The first technique manufactur- MESECAM A technique of recording SECAM video. ers employed for this purpose was a built-in nickel Instead of dividing the FM color subcarrier by four cadmium battery that lasted a relatively long time and then multiplying back up on playback, MESECAM (several hours), covering the length of most electri- uses the same heterodyne conversion as PAL. cal outages. The battery has been replaced by a meshbeat A TV distortion of wavy lines; also called smaller and less costly super capacitor, a device that linebeat or moire. can store an electrical charge powerful enough to metadata (side information) Informational data keep a VCR timer active long enough to cover some about the data itself. Typically information about the power failures. However, the average capacitor has audio and video data included in the signal’s data only enough storage to last from about 5 s to ap- stream. proximately 30 minutes. For those users who intend metal-backed screen Aluminized screen. to be away from home for long periods of time and metal evaporative tape See Vapor deposition. want a stronger assurance that their machine will metallized screen Aluminized screen. record an important program, an external accessory, metal oxide semiconductor chip See MOS. known as an uninterruptible power supply (UPS) unit, metal-particle tape A high-grade videotape com- is available. This item comes in several models, de- posed of needle-like metal particles and a roughly pending upon the number of watts. Many DVD play- textured base to hold the particles. The tape, which ers and TVs now use flash memory to retain settings, differs from standard tape that uses metal oxide in- eliminating the need for UPS devices. stead of metal particles, reportedly is free of drop- memory bank A VCR feature designed to permanently outs while producing a higher frequency response store such programming information as day, time, than other high-grade tapes. By replacing the oxide channel and an identifying code, all of which can with metal, manufacturers have more than doubled be recalled later for future scheduling without re- the strength of the magnetic field. entering each item separately. The short code may metamorphosing animation A special effect that consist of a few recognizable letters, such as “six” creates changing shapes and color for specific needs. for Sixty Minutes. This will help the user to recall the The technique is particularly useful for TV meteo- data when he or she wants to repeat the recording rologists who preprogram much of their weather process at a future date. animation. By incorporating metamorphosing ani- memory controlled effects A special feature usually mation, they can show the movements both of num- built into a professional production switcher and de- bers and storm fronts across the TV screen.

180 microphone mixing

metering system Refers to the technique used by a The micro-monitor also permits the viewing of a tape video camera or camcorder to measure the light while recording. necessary for the proper exposure of a scene or sub- microphone (mic) Also called mike (slang). A device ject. One simple system produces a simple value, used with video cameras, portable VCRs and home with the emphasis placed on the center portion of a models to record sound onto videotape. A micro- given scene. Another, sometimes referred to as the phone converts sound to electrical energy. Micro- two-field metering system, takes one reading of the phones have different response patterns. Some basic entire field and another reading of the central zone, types are the omnidirectional, bidirectional, direc- thereby assuring a correct exposure. tional and cardioid. There are also microphones for metropolitan area network (MAN) A loosely defined different purposes such as the lavalier, boom, etc. term generally understood to describe a broadband Other types are the condenser and dynamic micro- network covering an area larger than a local area phones. All microphones have some degree of col- network (LAN). It typically interconnects two or more oration, which alters its flat response. Basically, the LANs, may operate at a higher speed, may cross ad- less the coloration, the better the microphone. ministrative boundaries, and may use multiple ac- microphone boom An overhead extension arm that cess methods. It may carry data, voice, video and supports a microphone within range of the sound to image. be picked up but outside the range of a TV camera. mezzanine compression Contribution level quality microphone combiner Microphone mixer. encoded high-definition television signals. Typically microphone frequency response The measurement split into two levels: High Level at approximately 140 of the amount of coloration in a microphone. Since Mbps and Low Level at approximately 39 Mbps (for virtually all VCRs have a response that is less than high definition within the studio, 270Mbps is being that of hi-fi quality, it is easier to match a micro- considered). These levels of compression are neces- phone to the machine. Many recorders register an sary for signal routing and are easily re-encoded audio frequency response of up to 9 through 12,000 without additional compression artifacts (concatena- Hz. Therefore, a microphone with a range of 80 to tion) to allow for picture manipulation after decod- 12,000 Hz will provide a smooth response. ing. DS3 at 44.736 will be used in both terrestrial microphone impedance The resistance a microphone and satellite program distribution. offers to the sound signal it is picking up. Each mi- M format A recording method that is now considered crophone has its own impedance, which must be obsolete. It was used for professional ENG and EFP matched to the input impedance of the VCR or other production. Like the Betacam format, the two M similar unit. This is a relatively simple task involving format types could record for 20 minutes in the field. a matching transformer, available at most electronic The units used regular VHS videocassettes but nor- stores. The addition of this accessory will assure that mally required separate playback/editing devices in the microphone will operate at its peak frequency the studio. The videocassettes could not be played response. back on regular VHS format units. microphone jack A receptacle or opening that per- MH Modified Huffman data compression method. mits the connection of a microphone plug to the MHEG Multi- and Hypermedia coding Experts Group. video camera or VCR. There are only three kinds of A standardized language for the description of in- basic microphone jacks: the RCA phono jack, the teractive multimedia applications. It is currently ap- 1/4" jack and the most frequently used with home plied to multimedia presentations and as a kind of video components, the 1/8" mini-jack. Appropriate multimedia successor to teletext in Digital Video adapters are readily available for connecting any Broadcasting. Since MHEG is already supported in microphone jack with any other unit. these applications, it can be expected that a large microphone mixer An accessory that accepts several number of such broadcast services will become avail- microphones and controls the volume of each mi- able. MHEG standardizes a multimedia information crophone separately. They are usually limited to four interchange format called “Coded Representation inputs and offer some degree of portability. The of Multimedia and Hypermedia Information Objects” microphone mixer permits the use of only one mi- (ISO/IEC 13522). crophone when required, even while three other MHP See Multimedia Home Platform. microphones are connected to the console. The other mic Microphone. major purpose of the mixer is to blend the sounds microchannel plate A plate that consists of extremely of several microphones into one signal while bal- small cylinder-shaped electron multipliers mounted ancing the output of each in relation to the others. side by side, to provide high image intensification There are active and passive mixers. factors. Applications include night-viewing binocu- microphone mixing A video camera feature that can lars, telescopes, and TV camera tubes. combine the sound track of the tape with an exter- micro-monitor A small TV monitor with a 1.5" screen nal source. The process can occur either during re- and 1" speaker designed to be used in the field. cording or editing.

181 microphone pickup response microphone pickup response Polar response. in the 12-GHz range of the microwave band. Micro- microphone shadow In film, TV, a shadow of a mi- wave signals only travel in straight lines. In terrestrial crophone visible to the camera; also called mike microwave systems, they’re typically good for 30 miles, shadow. at which point you need another repeater tower. microphone splitter An accessory designed to split a microwave interference In satellite TV, interference single microphone line into multiple outputs. The from generators, transformers and other like devices, microphone splitter allows the divided microphone usually installed by utility companies in the vicinity level signals to feed various microphone inputs on of a parabolic antenna. If these objects fall in the such components as VCRs (both VCR/VTR formats), line of view between the antenna and the transmit- audio recorders, monitors, speakers, etc. This de- ting satellite, they can adversely affect reception. The vice provides proper isolation between outputs. The owner of a satellite TV system can obtain an FCC number of outputs depends on the particular split- license that will assure him or her of interference- ter. There are basic units described as 1x3 micro- free reception. phone splitters, which split one line into three microwave relay An electronic system of point-to- outputs, while more complex models can divide each point communication. The technology allows for the of four microphone lines into three outputs. There interconnection of radio, TV, and cable systems. Be- are also more sophisticated types such as the micro- cause they operate through the air at high frequen- phone splitter/combiner which splits and/or mixes cies, all microwave systems are licensed by the FCC. microphone signals in a variety of combinations. A signal, focused into a narrow beam, can travel Microphone splitters and splitter/combiners can be some 30 miles without a great deal of attenuation. either passive or active. Active units provide a gain In a point-to-point relay system, towers with amps of +/-6dB maximum and are designed for use with and small receiving and retransmitting antennas are equipment which does not have its own output set up and the signal passes from tower to tower. transformer. Passive splitters are usually of low im- This type of relay system made transcontinental TV pedance to match that of the microphone inputs possible in 1951. Microwave relay systems are now while active ones are of line level. used to transmit signals from a news site back to Interference in the form of a series of the studio or from a studio to a transmitting tower horizontal lines on a TV screen caused by extreme and antenna for rebroadcast. When a microwave surges from loudspeakers, applause or certain mu- relay system is used to connect the studio to the sical instruments. These loud bursts affect the pic- transmitter site, it is called a studio-transmitter link ture tube in the video camera but cause no (STL). A microwave relay system used by cable sys- permanent damage to the equipment. This effect tems to pick up stations that are too far away for can be avoided or minimized by keeping the video off-the-air reception is licensed by the FCC as a Com- camera out of direct range of these instruments and munity Antenna Relay Service (CARS). not standing too close to the loudspeakers. microwave transmission A method used by some microreflection In video, one of several forms of deg- pay TV systems to transmit over-the-air, point-to- radation that affects NTSC picture quality. point video signals. The encoded programs are Microreflections are caused by waves that strike a beamed to subscribers who are equipped with de- medium of different characteristics and are then re- coders. Besides microwave, pay TV can also trans- turned to the original medium. mit programs by way of telephone wires and cable. microsegmenting The process of configuring Ethernet midband cable tv Channels that occupy frequencies and other LANs with a single workstation per seg- not used for TV broadcasting. Midband channels, ment. The objective is to remove contention from like superband CATV channels, are channels A Ethernet segments. With each segment having ac- through I. Channels A-I are called midband because cess to a full 10 Mbps of Ethernet bandwidth, users they fall between channels 6 and 7 (which is the can do things involving significant bandwidth, such lower end of what is known as the high band). There as imaging, video and multimedia. are also subband channels which fall below chan- microwave A very high frequency range (1-100 GHz) nel 2: these are used for special transmissions. See in which the transmitted wave lengths are extremely also TV channel assignments. small (30-0.3 cm). Some people say microwave re- middle break A station identification in the middle of fers to frequencies between 890 MHz and 20 GHz. a radio or TV program. Microwave is a common form of transmitting tele- mid-range switcher A video switching device, falling phone, fax, video and data conversations used by somewhere between a low-cost consumer switcher common carriers as well as by private networks. Its and an expensive professional/industrial digital or lower portion, between 3.7 and 4.2 GHz, contains production switcher. Mid-range switchers may pro- the band of satellite channels. Other segments of the vide up to eight primary inputs, black and color back- band are allocated to amateur radio operators, police grounds, all-linear keying, and a variety of wipe radar, telephone companies, etc. DBS systems operate effects.

182 MIT-CC system

mid-side principle A technique employed in stereo minimum frequency blue -fB 4,020.000 kHz microphones (especially single-point stereo micro- (SECAM).

phones) in which a single internal component “lis- minimum frequency red -fR 4,126.250 kHz (SECAM). tens” to both its right and left while another element minimum illumination The least amount of light picks up information from a forward position. Many necessary to produce a viewable (not necessary vivid) recording patterns are possible by electronically mix- picture with a camcorder. Minimum illumination is ing the various combinations of outputs of the two expressed in lux—the lower, the better. Very sensi- components. This technique is also known as the tive camcorders measure 3 lux or below, though the MS principle. average is still about 7 lux. mike Slang for microphone. minimum sampling frequency See Pulse modulation. mike shadow See Microphone shadow. mini plug Similar to a phone plug in design but much mil 1/1,000 inch. The mil is used in measuring the smaller; a plug introduced by Japanese electronic thickness of a videotape. firms for use on miniaturized pieces of equipment. Miller integrator An integrator that contains an ac- Minitel French name for videotex. Commonly called tive device, such as a transistor, in order to improve Teletel. the linearity of the output from a pulse generator. mini-VCR Refers to 1/4"-size videotape in a compact Miller integrators are used particularly with sawtooth cassette which operates inside a smaller than usual pulse generators, such as those used to generate a portable VCR. The first such mini-VCR was time base. Technicolor’s model 212 which weighed 7 pounds, Miller sweep generator See Time base. measured 10" square and 3" deep and used a cas- mime The representation of an action without using sette just slightly larger than an audiocassette. The words, as by a mimic, mime, or pantomimist. In film mini-VCR format is incompatible with others such and TV post-production, miming is the synchroniza- as Beta and VHS in terms of videocassettes. But the tion of sound and action, as in lip-sync. machine can be connected to any model for dupli- miming See Mime. cating tapes and can be hooked up with any cam- minicable system A small CATV system, such as era and other components as long as the proper SMATV, a system within a building that receives its cables are obtained. signal from a satellite; also spelled mini-cable. mini video An alternate VCR format using 1/4" tape. minicam A small, self-contained portable TV camera, The 8-mm video system is designed mainly for a one- for videotaping on-site news events. When linked to piece video camera/recorder with 1- or 2-hour maxi- a mobile transmission unit (minicam van), the minicam mum recording time. The advantages of mini video can provide live coverage at relatively low cost. It has include lighter equipment, smaller components and tremendously changed TV news programs at all types relatively less expensive tape. of stations. See also Creepy peepy, Shaky cam. mips Million instructions per second. mini-enhancer A device designed to improve the video mired MIcro-Reciprocal-Degree. Unit used for the signal of portable VCRs, video cameras, etc. The measurement of color temperature, corresponding mini-enhancer attaches between camera and re- to the value in the degrees Kelvin divided into corder and is meant to be used in the field. It is also 1 million. useful when camera extension cables are used. The mirror-backed screen Aluminized screen. accessory usually contains a bypass switch that al- mirror reflection Direct reflection. lows a comparison of enhanced and unenhanced misalignment A condition in which one of the pri- image. mary colors in video (R,G,B) appears on the side of a mini-jack A phone jack or plug used in the audio in- subject, as if that particular color is “bleeding” or puts and outputs of Beta VCR. The 1/8" jack is not registering properly. Misalignment, sometimes smaller than the more popular RCA jack generally referred to as misregistration, is the result of improper used in the VHS format. Sony uses the RCA-type in convergence—the inability of electron beams to its video input and output together with the mini- strike the face of the picture tube precisely. With a jack in its audio lines. The size of the jacks becomes video camera, the problem stems from a faulty important when copying tapes from one machine camera pickup tube. to another and using the audio/video rather than miscellaneous common carrier A communications the RF connections. common carrier (typically one using microwave) minimicrowave In TV, referring to the transmission which is not offering switched service to the public of a video signal from a nonstudio site—such as a or to companies. A miscellaneous common carrier news event—to a mobile unit or a transmitter on a usually provides video and radio leased line trans- nearby roof. The transmitter then sends the signal mission services to TV and radio networks. directly to the station or possibly to one or more misregistration See Misalignment. intermediate points, such as atop a tall building or mistracking See Tracking, Tracking control. other high point. MIT-CC (Channel-Compatible) system A proposed

183 MIT channel-compatible system

single-channel noncompatible simulcast HDTV sys- one source can increase or decrease on the screen tem. It employed double-sideband quadrature- by the movement of a simple control. A mix differs modulation of a carrier in the center of the 6-MHz from an effect that keeps the entire image even channel. This signal was not intended for NTSC re- during superimposition. ceivers, i.e., the system is noncompatible. The pre- mixed highs The high-frequency signal components ferred originating signal was produced by a camera that are intended to be reproduced achromatically operating at 16:9 aspect ratio and 1200 lines, pro- (without color) in a color TV picture. gressively scanned. The preferred frame rates were mixed mode An imprecise term that suggests that either 60 or 72 fr/s, these being multiples of a basic one digital bit stream can carry voice, data, fax and picture repetition rate of 12 per second. This signal video signals. source, feeding the NTSC-compatible simulcast mixed syncs A synchronizing signal consisting of line channel, would produce a display of the letter-box sync pulses and field sync pulses but containing no type, with blank bars above and below the 16:9 area other information. displayed on the 4:3 conventional display. The RGB mix/effects switcher A multi-buttoned, box-like elec- output of the camera was scanned at resolutions of tronic console used by professionals to create a vari- 240 pixels per picture height, 400 pixels per picture ety of special video effects. The instrument can width, scanned progressively at 12 fr/s. The lumi- produce a number of preset patterns, including nance resolution for stationary portions of the im- wipes, keys and digital effects. Each row of buttons ages was 762 x 1200 at 12 frames per second and is called a “bus.” 508 x 800 at 36 fr/s. The chrominance resolutions mixer 1. A device that has two or more inputs, usually for static portions were 400 pixels per picture width, adjustable, and a common output. It combines sepa- 254 elements for portions in motion. The analog rate audio or video signals linearly in desired pro- output of the camera was digitized in a transmitter portions, to produce an output signal. 2. The stage converter operating at 8.4 or 12 Mbytes/s. The MIT- in a superheterodyne receiver where the incoming CC receiver had a display of 1200 lines, 16:9 aspect modulated RF signal is combined with the signal of ratio. The MIT-CC system was initially designed for a local RF oscillator to produce a modulated IF sig- distribution over 6-MHz cable channels, but it could nal. The mixer and oscillator together form the con- be transmitted on the DBS service, and on terres- verter. See also Microphone mixer. trial 6-MHz channels. M-JPEG Motion JPEG. MIT channel-compatible system See MIT-CC system. M-load The loading system used by VHS VCRs and MIT-RC (Receiver-Compatible) system, Schreiber A first invented by Sony. The machine wraps the tape single-channel NTSC-compatible proposed advanced around the head drum in an “M” design, hence the TV system, occupying the standard 6-MHz channel, name. To do this, 13" of tape are removed from the with a transmitted signal of 525 lines, 59.94-Hz field cassette, in contrast to the Beta system in which rate, interlaced 2:1 with 16:9 aspect ratio. The dis- 24" are taken out. Two twist pins angle the tape to play on a conventional receiver had 60 blank lines its path around the video head drum. Each time the above and below the 16:9 outline, minus those hid- VCR enters the Stop mode, the tape is loaded back den by overscan. The chrominance information was into the cassette. transmitted at 14.985 fr/s, half the NTSC rate. The M-loop The shape in which videotape is laced around extra time of the blank lines and the frames free of the heads in a VHS VCR. chrominance were used to carry ancillary informa- MM CATV hyperband channel, 372-378 MHz. tion sufficient to produce a 1050-line luminance dis- MMCD Multimedia CD. play with a resolution of 535 lines horizontally and MMCD-R/E A recordable version of MMCD (R/E for 600 lines vertically for a stationary image. This was record/erase) using phase-change recording technol- reduced to 315 and 360 lines, respectively, for ob- ogy, with magneto-optical recording as an optional jects in motion. The chrominance resolutions were method. 180 (I), 130 (Q), lines (stationary), and 180 (I), 65 MMDS Multichannel Multipoint Distribution Service. (Q), lines (in motion), respectively. The RC system mobile unit A truck or other vehicle equipped with was designed to be used cooperatively with a si- TV studio equipment for TV pickups at remote loca- mulcast channel-compatible (CC) system (MIT-CC). tions. Picture and sound signals are usually sent back MIT receiver-compatible system See MIT-RC system. to the main transmitter by microwave transmitter MITV Microsoft Interactive TV. Blends TV with elements on the truck. of the Internet for a more interactive viewing expe- mode A type of ham radio communications; examples rience. Microsoft TV is an open software platform are FM, SSTV and packet radio (a computer-to-com- technology sold to other network operators and puter communications mode in which information broadcasters globally. is broken into short bursts). mix The superimposition of one image over another. modem Modulator/demodulator, a device that trans- With the use of a mixer/fader device, the image of forms a typical two-level computer signal into a form

184 monitor

suitable for transmission over a telephone line. Also effect occurs when converging lines in the picture does the reverse—it transforms an encoded signal are nearly parallel to the scanning lines. Video moire, on a telephone line into a two-level computer sometimes called a rainbow effect, occurs also when signal. the VCR is in Record mode and Pause is pressed. mode switch A feature on some VCRs for selecting Recent machines have introduced special circuitry Mono, Stereo or SAP broadcast mode. Some TV re- that all but eliminates moire caused by the record/ ceivers have these modes on the remote control unit. pause functions. modified horizontal sweep signal Nonlinear saw- Mole technology A seamless MPEG-2 concatenation tooth signal (H’) as is usual horizontal scan signal technology developed by the ATLANTIC project (BBC (H). See Depth matrix. [U.K.], Centro Studi e Laboratori telecomunicazione modified NTSC See CCF system. [Italy], Ecole Nationale Superieure des Telecommu- modular chassis A TV chassis that is made up entirely nications [France], Ecole Polytechnique Fédérale de of separate modules for each circuit in the TV set. Lausanne [Switzerland], Electrocraft [U.K.], modulation 1. In general, the alteration or modifica- Fraunhofer-Institut für Integrierte Schaltungen [Ger- tion of any electronic parameter by another. The re- many], Instituto de Engenharia de Sistemas e verse process is demodulation, by which an output Computadores [Portugal], Snell & Wilcox [U.K.]) in wave is obtained having the characteristics of the which an MPEG-2 bit stream enters a Mole-equipped original modulating wave or signal. Intermodulation decoder, and the decoder not only decodes the is the modulation of the components of a complex video, but the information on how that video was wave by each other in a nonlinear system, produc- first encoded (motion vectors and coding mode de- ing waves having frequencies, among others, equal cisions). This “side information” or “metadata” in to the sums and differences of those of the compo- an information bus is synchronized to the video and nents of the original wave. In NTSC and PAL TV, the sent to the Mole-equipped encoder. The encoder picture portion of the program is AM, and the sound looks at the metadata and knows exactly how to portion is FM. 2. A technique that adds audio or encode the video. The video is encoded in exactly video signals to a preselected carrier signal. the same way (so theoretically it has only been en- modulation index The ratio of the frequency devia- coded once) and maintains quality. tion to the frequency of the modulating wave in a mom-and-pop store A small, family-operated shop. FM system when a sinusoidal modulating wave is In CATV and other fields, a small, single-ownership applied. local system. modulation transfer function (MTF) The curve that monaural Monophonic. expresses the luminance contrast between black and monitor 1. A TV set minus receiving circuitry. Moni- white lines on a graphic-alphanumeric display screen tors have no VHF/UHF tuners, IF amps or video de- as the number of lines increases. See Depth of modu- tectors. Some monitors do not have any audio lation chart. See also Aperture response. system. A monitor is used basically to directly dis- modulator A miniature transmitter whose circuitry car- play the composite video signal from a camera, VTR, ries the raw audio and video signals from micro- or SEG. Often more costly than a TV receiver, the phones and video cameras and puts them in a monitor, with its more advanced and sophisticated designated bandwidth channel or range of frequen- circuitry, produces a superior picture. It also contains cies. TV modulators register the video and audio sig- audio/video input jacks as well as other features such nals into separate carriers. A demodulator, or tuner, as picture focus, internal and external sync and hori- then strips the video signal from its carrier to repro- zontal and vertical scanning. The major advantage duce the original video signal. of the monitor over the TV set is that the composite moire 1. In TV, a wavelike distortion, an effect caused video signal travels directly to the audio amps. These by the combination of excessively high frequency direct processes retain the original quality of the sig- signals. Mixing of these signals causes a visible low nals. A monitor differs from a monitor/receiver. One frequency that looks a bit like French watered silk, of the more recent developments in monitors is the after which it is named. For example, a moire effect auto-setup monitor that can line itself up automati- can be caused by beats between a pattern in the cally. 2. An instrument that measures continuously original scene (say a checked suit) and the line struc- or at intervals a condition which must be kept within ture of the reproduced picture. Moire or “color- prescribed limits, such as the image picked up by a crawl” can occur if the color-burst signal is present microphone at a radio or TV studio, a variable quan- during a black and white transmission. Also called tity in an automatic process control system, the trans- meshbeat, linebeat, herringbone, or crawling dot mission in a communication channel or band, or the pattern. 2. A tremulous spectrum of color caused position of an aircraft in flight. 3. A person who during editing when a VCR is backspaced and the watches a monitor. 4. A high-quality CRT used to beginning of a new scene is superimposed over the display video signals (requires an outboard tuner in end of another scene. The wavy, satin-like optical order to receive TV signals). 5. To record, verify, or

185 monitor analyzer

check a radio or TV program, or to supervise, verify, camera. It is a temporary or limited alternative to a or check any operation, such as an event, sales cam- video tripod. Although monopods are less costly, paign, or computer program. lighter in weight and easier to carry than tripods, monitor analyzer A device, introduced in 1978 to they require continuous handling to maintain the home video field, which helped adjust the bright- steadiness. ness and color of a TV set. The plastic monitor ana- An electron tube containing a target on lyzer, which came with a ready-reference chart, sold which a pattern or photograph is printed and which, for about $25 and worked only with color bar test by scanning the target by an electron beam, gener- patterns on the TV screen. ates a picture signal corresponding to the printed monitor camcorder, Sharp Combination of image. The tube is generally a high-velocity type and camcorder with video monitor for quick viewing of the pattern is printed in a pigment that modifies the “rushes,” prerecorded cassettes, or even TV (with secondary-emission ratio of the target. Such tubes an optional tuner). Sharp’s success inspired some- are useful in TV services because they can replace a what similar models by Sony, Fuji Photo, JVC, and complete camera channel when a stationary pat- RCA. tern is to be transmitted. monitoring Using a monitor. In broadcasting, check- monotonic A term that is used to describe ADCs and ing a sound or TV program for technical quality. High DACs. An ADC or DAC is said to be monotonic if grade equipment is used for reproducing sound pro- for every increase in input signal, the output increases grams and for displaying TV pictures while they are also. The output should not decrease. being recorded or transmitted so that any technical Montreux International Television Symposium & faults are detected and can be put right at the earli- Technical Exhibition (TV Montreux) A bi-annual est opportunity. international conference for the television broadcast monitor/receiver A monitor with a built-in TV tuner; industry. a component that looks like a conventional TV set Moore’s Law A prediction for the rate of develop- but has direct audio and video inputs as well as ad- ment of modern electronics. It has been expressed ditional features usually not found on TV receivers. in a number of ways but in general states that the Like all monitors, these sets accept direct hook-ups density of information storable in silicon roughly of VCRs, VDPs, video games, etc. By avoiding RF doubles every year. Or, the performance of silicon inputs, the monitor/receiver can retain the original will double every eighteen months. For more than signal strength. More expensive than ordinary TV two decades this prediction has held true. Named receivers, monitor/receivers are often sold by audio/ after Gordon E. Moore, physicist, co-founder and video dealers rather than conventional retail stores. chairman emeritus of Intel Corporation. monitor/receiver reference tape A specially prepared mopic Military word for motion picture. videocassette of the tape containing miscellaneous MOPS Millions of operations per second. Refers to a video test patterns for the proper adjustment of processor’s performance. In the case of DVI tech- monitor/receivers. Often as short as 10 minutes, the nology, more MOPS translates to better video tape features tests for convergence, flesh tones, color quality. bars, gray scale, etc. The reference tape permits ad- MOS A metal oxide semiconductor chip that replaces justing equipment for color purity, alignment, tint, the conventional saticon and vidicon camera tube. brightness, contrast, chrominance, etc. Also known While the horizontal resolution of the MOS chip as setup tape. doesn’t match other HQ cameras, the advantages monitor speaker Refers to a small built-in video cam- of this technology include a lighter and smaller cam- era speaker that permits the user to check the sound- era, no waiting for tube warmup, less power con- track. The monitor speaker eliminates the need for sumption and no image burn or drag. Hitachi, with headphones. its model VK-CIOOO, was the first company to fea- monochromatic Consisting of one color or wave- ture a camera using the MOS image sensor. length. Although light in practice is never perfectly mosaic 1. Short for photomosaic. In a camera tube, monochromatic, it can have a narrow region of the an electrode consisting of a very large number of spectrum. individually insulated, photo-emissive globules on monochrome In TV, a system in which the transmit- which the optical image is focused. Photo electrons ted information is confined to the luminance of the released from the globules in accordance with the scene. No color information is transmitted. A mono- amount of light falling on them leave a charge im- chrome system is therefore a black and white sys- age on the mosaic surface. See Iconoscope. 2. A tem. The term is unfortunate because monochrome special-effects feature that breaks up a video image means literally light of a single wavelength whereas into hundreds of little squares or rectangles. The ef- white light contains a range of wavelengths. The fect is often used in to hide term “black-and-white” is correct. the face of witnesses during interviews and hear- monopod In video, a one-legged support for a video ings or to prevent nudity from appearing on TV

186 moving shot

screens. This feature is usually found on certain digi- motion portrayal Ability of TV system or device to tally equipped units such as editing consoles. reproduce the moving objects in a TV picture with- mosaic electrode The light-sensitive electrode of a out visible artifacts. TV camera tube on which the image is formed. motion processor, HDMAC. See Bandwidth reduction, MOS image sensor Solid-state device used in place EU-95. of a video tube. motion recognition See Motion detection. motion adaptive A design that senses motion in or- motion resolution Resolution when there is a move- der to alter the way it functions, for the purpose of ment in the TV picture, for example, when the cam- avoiding or reducing some motion-related artifacts. era is zooming or panning. Syn.: dynamic resolution. motion adaptive interpolation circuit An advanced motion vector A two-component signal showing the electronic technique used in large-screen Improved magnitude and direction of moving object displace- Definition TV to improve deinterlacing quality or ment over a given time interval—for example, be- comb filtering. Motion adaptive comb filters, first tween two TV fields. Usually represented in Cartesian utilize inter-line and inter-field information and then coordinates, but could equally well be represented process it by applying two separate types of digital in polar notation. memory buffers. motion video Video which displays real motion. It is motion analysis camera A professional/industrial video accomplished by displaying a sequence of images camera designed for stop-motion videotaping. Used (frames) rapidly enough that the eye sees the image for industrial, medical, laboratory and military appli- as a continuously moving picture. cations, the cameras usually contain a variable speed mousey See Mousy. shutter with speeds capable of from 1/500 to 1/ mousy Also mousey. Pale in color, weak. 10,000 of a second. Motion analysis cameras per- MOV The file extension used by MooV format video form such highly technical tasks as color spectral analy- files on Windows. These MOV files are generated sis, spray-flow study, high-speed microscopy, with Apple Computer’s QuickTime and played on speeding-bullet analysis, etc. Many models are com- Windows systems via QuickTime for Windows. patible with Beta, VHS, 3/4" and 1" formats. movie A film, a moving picture, shown in a movie motion blur 1. Generally, motion blur is an effect theater, on TV, or elsewhere. caused by integration. Put more simply, it is normally movie of the week (MOW) A theatrical film or a caused by the image being composed from a sum made-for-TV film shown weekly on TV. of the latest image plus a smaller portion of the pre- movieola See Moviola. vious sum and so on. The result of this is that mov- movie rating systems Organized procedures for clas- ing objects leave a trail behind them, giving rise to a sifying motion pictures according to content. The blurred appearance. Such an artifact is normally as- ratings (according to the MPAA — Motion Picture sociated with two-field standards conversion or tube Association of America) are: G (General audience— cameras. 2. As a digital video effect, the above arti- all are admitted); PG (Parental Guidance suggested— fact may be generated deliberately. some material may not be suitable for children); motion compensation 1. A video compression tech- PG-13 (Parental Guidance suggested—no one un- nique that makes use of the redundancy between der 13 admitted); R (Restricted—youth under 17 adjacent frames of motion video. 2. Scheme of video must be accompanied by a parent or adult guard- signal processing (e.g., standards conversion), involv- ian); and X—no one under 17 admitted. The ratings ing the use of motion vectors to skew the filtering are often published in TV and cable program guides axis (e.g., the interpolation axis) by correspondingly and are usually placed on videocassette boxes and shifting parts of the source TV fields. on advertising and POP (point of purchase) displays. motion detection Operation of video signal process- Another rating system has been developed by the ing aimed to produce an output indicating the pix- Film Advisory Board (FAB), a Los-Angeles-based els or groups of pixels which belong to moving group of producers and interested citizens. Its sys- objects as opposed to static portions of the picture. tem has been adopted by those who believe the Syn.: motion recognition. MPAA ratings do not go far enough in describing a motion detector See MUSE-6 system. film. The FAB has six major designations: C—Chil- motion estimation A calculation to figure out where dren through age 7; F—Family; M—Mature; VM— an object has moved to from one video field or frame Very Mature; EM—Extremely Mature; and to the other; operation of video signal processing AO—Adults 18 and Older. In addition the FAB- designed to produce a motion vector signal. Mo- printed labels on cassettes boxes add descriptions tion estimation is an integral part of MPEG. such as “frontal nudity,” “extreme language,” “sub- Motion JPEG JPEG compression or decompression is stance abuse,” “violence,” and “erotica.” applied real-time to video at up to 50 or 60 fields moving dots See Cross-luminance. per second. Each field or frame of video is individu- moving matte insert Overlay. ally processed. moving shot A filming or videotaping technique in

187 Moviola

which the camera follows the action; also called MPEG-21 The Motion Picture Experts Group’s attempt action shot, follow shot, or running shot. to get a handle on the overall topic of content deliv- Moviola The trade name for an upright film-editing ery. By defining a Multimedia Framework from the machine that reproduces film in miniature. The ge- viewpoint of the consumer, they hope to understand neric spelling for this type of machine—which also how various components relate to each other and reproduces sound—is movieola. Though once ubiq- where gaps in the infrastructure might benefit from uitous in film-editing rooms, the Moviola has been new standards. replaced by flatbed editing machines, or horizontal MPEG IMX Sony’s trademark for a family of devices, tables, and also by videotape editing processes. such as DVTRs, that are I frame-only 50 Mbps MPEG- mozaic Alternate spelling of mosaic. 2 streams using Betacam style cassettes. Plays Digi- MPEG Motion Picture Experts Group. A moving image tal Betacam, Betacam SX, Betacam SP, Betacam, and, compression standard that can compress video bet- MPEG IMX, outputting 50 Mbps MPEG I-frame on ter than JPEG and still maintain a high image qual- SDTI-CP regardless of the tape being played. It can ity. MPEG uses an interframe compression scheme, also handle other (lower) input and output data where only one frame every half second is fully re- rates, but the recordings are 50 Mbps I-frame in any corded; only the changes between frames are then case. noted. MPEG is designed to be a distribution for- MPEG splicing The ability to cut into an MPEG bit mat and is not designed for use in video editing stream for switching and editing, regardless of type systems. of frames (I, B, P). MPEG++ See Advanced digital television. MPX 1. Multiplex. 2. Jacks on TVs and VCRs that al- MPEG-1 Standard for compressing TV pictures into low connection of an optional MTS adapter. digital code which runs at up to 1.5 megabits/s. Used MRFA Broadband RF amp for TV applications in the in video CD players. MPEG-1 was a transitional speci- 470- to 860-MHz range; , Phoenix, Arizona. fication to be replaced by MPEG-2. The amp module is specified at 26.5 V with an out- MPEG-2 Digital video compression standard using simi- put power of 25 W minimum at 1-dB compression lar coding techniques (as MPEG-1) to handle data and a 10.5-dB minimum small signal gain. However, rates of between 4 and 8 megabits/s. MPEG-2 ex- it can operate at 28 V. tends the MPEG-1 standard to cover a wider range MSB Most significant bit, or the bit that has the most of applications. This standard, established by the value in a binary number or data byte. In written ISO’s Motion Picture Experts Group, is currently fa- form, this is the bit on the left. vored for international use in pay-TV, domestic digi- MSD Multistandard color decoder. tal video recording, video mail, digital video editing MSDL MPEG-4 Syntactic Descriptive Language. The and computer-based video. Used in VCRs and, since language of the MPEG-4 standard. A set of tools 1994, in DVD players, digital cable, satellite, and used in the MSDL includes not just motion compen- over-the-air (OTA) standards. sation but contour representation and other tech- MPEG-3 MPEG-3 was originally targeted for HDTV ap- niques that allow scalable bit rates and hierarchical plications. This was incorporated into MPEG-2. decoding and display of objects. MPEG-4 Object-based audiovisual coding. This stan- MSO The abbreviation for Multiple System Operator dard is expected to serve as an enabling technology (also Multi-Station Operator) or CATV owner. Larger for the convergence of broadcast and interactivity. cable companies like Teleprompter, Warner Amex Previous MPEG standards had an obvious applica- and ATC actually own and control many cable sys- tion; MPEG-1 was for video CDs and MPEG-2 for tems. Cf. SSO. digital TVs. There is interest in using MPEG-4 for MS Principle Mid-Side Principle. digital cable and satellite applications since it uses MSPS Megasample per second. about one-half the bit rate of MPEG-2 for similar MTF Modulation transfer function. video quality. See MSDL. MTS Multichannel Television Sound. Implemented EIA MPEG 4:2:2 Also referred to as Studio MPEG, Profes- standard for stereo TV reception in the US comprised sional MPEG and 442P@ML. Sony’s Betacam SX is of a decoding system developed by Zenith and DBX based on MPEG 4:2:2. See MPEG-2. noise reduction. MTS-equipped TVs and VCRs re- MPEG-7 MPEG-7 standardizes the description of mul- ceive both stereo TV broadcasts and second audio timedia material (referred to as metadata), such as programs (SAP), which feature an additional audio still pictures, audio, and video, regardless if locally track for simultaneous second-language translations. stored, in a remote database, or broadcast. Examples MTS decoder That part of a VCR or stereo TV receiver are finding a scene in a movie, finding a song in a that produces stereo separation, measured in dB. In database, or selecting a broadcast channel. The addition, the quality of a decoder depends on its searcher for an image can use a sketch or a general S/N ratio and frequency response. Because they are description. Music can be found using a “query by difficult to align at the factory, many MTS decoders humming” format. leave something to be desired in stereo separation.

188 multimedia

Separate units, sometimes called MTS/SAP decod- nel of the MTS signal is identical to the current mono ers, are available for TV sets and monitor/receivers signal. The L+R signal has 75 ms pre-emphasis and not equipped to receive stereo broadcasts. deviates the aural carrier 25 kHz. The next compo- mult box An electrical device that combines and regu- nent of the MTS signal is the 15.734-kHz stereo pi- lates the flow of electricity and distributes a regu- lot carrier. The pilot carrier deviates the aural carrier lated or consistent audio feed. It is used by radio 5 kHz and is used in the receiver to detect the L-R and TV crews, particularly at events with consider- stereo sub-channel. The L-R sub-channel is an AM able equipment tapping into the speaker’s lectern modulated double side band suppressed carrier sig- or other site. nal and deviates the aural carrier 50 kHz. The SAP Multi- and Hypermedia Coding Experts Group subcarrier is an FM-modulated, 10-kHz deviated sig- (MHEG) A standardized language for the descrip- nal centered at 78.670 kHz. The SAP subcarrier de- tion of interactive multimedia applications. As for viates the aural carrier 15 kHz. Both the L-R and SAP WWW services, a protocol is needed for embedding audio signals are DBX-encoded to reduce buzz and the MHEG applications into a DVB or DAB noise. datastream. For DVB, the Digital Storage Media multidimensional autofocus A camcorder feature Command Control (DSM-CC) protocol is used. that provides uninterrupted focus from lens surface multi-brand remote control Multi-purpose remote to infinity. This does away with the necessity for the control. conventional macro setting for extreme close-ups. multiburst A test pattern for testing horizontal reso- multi-eye system An autostereoscopic 3D-image sys- lution of a video system. It consists of sets of vertical tem based on the number of observers. See double- lines with closer and closer spacing. eye system. multi-burst chart See Video test chart. multiformat In video, a VCR that can play back video- multiburst waveform—NTSC VITS This portion of tapes recorded in foreign countries that have differ- the VITS, usually transmitted on line 17, field 1 in ent broadcast signals from those in the US. Usually, the vertical blanking interval, is composed of a se- such machines, which compensate for American and ries of six equal amplitude bursts covering a range foreign differences in the number of scan lines and of frequencies at typically 0.5, 1.5, 2.0, 3.0, 3.58 house-current cycles, can process signals from PAL and 4.2 MHz. If signal amplitude varies across the or SECAM tapes. frequency spectrum, this will be seen in the height multiframe edit viewer A method of showing a se- of the bursts. A burst of peak white, known as the ries of frames in sequence. The unit displays fixed “white flag,” is also transmitted as a white refer- multiple images, which can then be considered as ence level. edit points according to their sequence. The major multicam 1. The use of two or more cameras simulta- benefit of multi-frame edit viewing is its doing away neously to shoot a scene from more than one angle. with the need to continually move the tape. 2. An early method of recording TV shows. Three multifunction display Whenever an operation but- film cameras were positioned in the studio and shot ton is pressed, the activated function is immediately the show from different angles. They could be turned indicated on this easy-to-see display. It shows at a off or on at will but in many cases were simply kept glance in what operation mode the VTR is running for the entire show. The resulting films were functioning. then edited, using three moviola machines. The qual- multigrab A very common budget digital video effect ity of the finished film was vastly superior to the where the image is merely frozen for a determined kinescope process. period and then instantly updated at the beginning Multicast 1. Data flow from single source to multiple of the next period. Live images may sometimes be destinations; a multicast may be distinguished from used in-between freezes. Syn.: skip-field; strobe; stro- a broadcast in that the number of destinations may boscope. be limited. 2. A term often used incorrectly to de- multigun tube A CRT containing more than one elec- scribe digital television program multiplexing. tron gun. Color TV receivers use M-GTs, as do mul- multichannel multipoint distribution service tiple-presentation oscilloscopes. (MMDS), CATV See Auxiliary Radio Services. MMDS multilevel chroma bar Test signal in a form of color is allocated 48 MHz (eight amplitude-modulated TV subcarrier modulated by staircase signal—i.e., the channels), from 2596 to 2644 MHz, to transmit TV chroma amplitude rises in discrete steps along the programs and data to customer-selected locations. It TV line. This signal is usually on a gray level pedes- is used for the distribution of TV programs in sparsely tal. Syn.: chrominance staircase. populated areas where cable is uneconomical. multimaster In I2C-bus systems, more than one mas- multichannel television sound (MTS) A system to ter can attempt to control the bus at the same time transmit stereo, bilingual, and voice/data signals. The without corrupting the message. MTS system is compatible with current transmissions multimedia The combination of multiple forms of and mono receivers. The L+R portion or main chan- media in the communication of information. Multi-

189 Multimedia CD

media enables people to communicate using inte- a 10-pin connector but soon switched to and pres- grated media: audio, video, text, graphics, fax, and ently use a 14-pin system while VHS adopted the telephony. Multimedia communication formats vary, 10-pin configuration. Akai, although a VHS system, but they usually include voice communications developed its own 7-pin connector. Not only are (vocoding, speech recognition, speaker verification these systems incompatible, but all the pin functions and text-to-speech), audio processing (music syn- of one 10-pin VHS camera connector do not neces- thesis, CD-ROMs), data communications, image pro- sarily match a VHS recorder. (Beta 14-pin connec- cessing and telecommunications using LANs, MANs tors are standardized.) Some VCR manufacturers and and WANs in ISDN and POTS networks. Two hot independent companies sell adapters that permit multimedia buzzwords are convergence, which tells attaching 14-pin connectors of Beta cameras to VHS you that TV sets, cable services, and telephones are recorders, which of course accept only 10-pin getting more like PCs and vice versa, and nonlinear connectors. editing, which means that you’ll no longer have to multiple-effects generator An editing unit for post- edit materials in their traditional a/b roll order. production work that provides an array of profes- Multimedia CD (MMCD) DVD system; Sony/Philips. sional functions. The machine features a multimedia computer A product that combines PC special-effects generator for fades and wipes in doz- with digital video and audio. ens of patterns, a colorizer, an audio/video proces- multimedia kit A collection of items, such as film- sor, a color processor and a genlock/power supply. strips, posters, and videotapes, in one package, used The last item permits the user to dissolve from one in schools and elsewhere. video source to another. multipass encoding True multipass encoding is cur- multiple-player video game system A process us- rently available only for WM8 and MPEG-2. An en- ing telephone lines or CATV systems to permit 2 to coder supporting multipass will, in a first pass, 10 players to participate in one video game. analyze the video stream to be encoded and write multiplex To transmit two or more signals simulta- down a log about everything it encounters. Let’s neously on a single wire, bus, or channel. See also assume we have a short clip that starts out in a dia- Stereo adaptable. log scene where we have few cuts and the camera Multiplexed Analog Component (MAC) European remains static. Then it leads over to a karate fight analog standard for HDTV. with lots of fast cuts and a lot of action (people fly- multiplexed TV signal In 3D-image display systems, ing through the air, kicking, punching, etc.). In regu- picture/sound information + identification data. The lar CBR, encoding every second gets more or less multiplexed TV signal received by antenna is sepa- bitrate (it’s hard to stay 100% CBR but that’s a de- rated into an analog picture/sound signal and a data tail) whereas in multipass VBR mode the encoder signal by a separating circuit. will use the bitrate according to his knowledge about multiplexer (MUX, MXR) 1. Electronic equipment that the video stream, i.e. the dialog part gets the avail- allows two or more signals to pass over one commu- able bitrate and the fighting scene gets allotted more nications circuit. That “circuit” may be a phone line, bitrate. The more passes, the more refined the bitrate a microwave circuit, or a through-the-air TV signal. distribution will be. In single pass VBR, the encoder That circuit may be analog or digital. There are many has to base his decisions on where to use how much multiplexing techniques to accommodate both. 2. A bitrate solely on the knowledge of the stuff it previ- multimedia device which permits dissolving or cut- ously has encoded. ting from films to slides or any combination of these. multipath Multipath transmission. Utilizing various lenses, prisms, beam splitters and multipath reception Reception in which the trans- mirrors, the multiplexer can handle many input mitter signals arrive at a receiving antenna over two sources simultaneously. 3. An optical system allow- or more paths, one direct and the others reflected ing a number of film and slide projectors to feed video from buildings or other obstacles. One result is ghosts information into the same TV camera. in the TV picture. multiplexing The combining of two or more inde- multipath transmission The propagation phenom- pendent signals into one transmission channel. enon that results in signals reaching a receiving an- multiplex output A TV or monitor/receiver connec- tenna by two or more paths, causing distortion in tor that permits adding a special audio adapter unit radio and ghost images in TV. At least one of the for receiving stereo TV programs. paths involves reflection from some object. It is also multiplier Electron multiplier. called multipath. Also multipath interference. multiplier focus See Persuader. multi-pin connector A component with a predeter- multipoint distribution service (MDS), CATV The mined number of metal pins attached between a utilization of a microwave system of over-the-air, line- video camera and a VCR. Each pin is assigned a spe- of-sight broadcasting of video programs over a single cial function—e.g., audio output, video ground, channel. MDS is allocated 10 MHz of spectrum video signal input, etc. Early Beta recorders first used space, from 2150 to 2160 MHz. It is a point-to-

190 MUSE

multipoint service authorized to transmit single- multistrobe A digital VCR feature that continually and channel video and data signals to customer-selected successively updates a series of strobes or still pic- locations within a metropolitan area. Subscribers use tures generated on the TV screen by the strobe func- specially equipped receivers to pick up MDS pro- tion. grams. This system differs from that of CATV or sub- multitap A device used in cable systems to select por- scription TV. CATV uses coaxial cable while STV tions of the signal from the feeder cables to serve makes use of conventional VHF and UHF channels. more than one subscriber from a single location. This MDS also differs from other microwave systems in electronic component is usually mounted at a tele- that it transmits weaker signals in all different direc- phone pole location and can provide service to two, tions. The service is regulated by the FCC. See four, or eight subscribers. It taps signals from the Auxiliary Radio Services. feeder cable that are then sent to each subscriber’s multipurpose remote control A preprogrammed home by cable drop lines. remote control pad that can “communicate” with a multivision A system designed to feature simulta- large variety of VCRs, DVD players, cable converter neously more than one image on the TV screen. Early boxes and TV sets. Unlike other advanced remote experiments in the 1960s with multivision TV made controls, such as universal remotes, these multi- no impact on the public. Sony offered a model with brand units, as they are sometimes called, cannot three black and white 9" picture tubes placed side be “taught” the codes of other machines. Instead, by side; RCA followed with a 25" color set and three they have been preprogrammed to work with many 10" black and white tubes in one cabinet. The con- devices. cept was dropped until 1979, when Sharp intro- multipurpose zoom lens A video camera lens that duced dualvision, a TV set which presented a second, offers several sophisticated features along with the smaller black and white image within its regular pic- conventional zoom function. Multi-purpose zoom ture. In 1980 Sharp introduced a model in which lens provides automation for previously manual func- nine different color channels could be viewed simul- tions. For example, focus memory maintains the taneously, rotated or placed into Freeze Frame. sharpness of the subject as it moves toward or away See PIP. from the camera. Other features may include zoom municipal cable TV A CATV station owned by a local memory, autofocus macro and auto framing. government. Fewer than three dozen exist of the multiscreen digital freeze A digital VCR feature that more than 4,000 cable systems in the US. MCATV allows the viewer to fill the TV screen with several differs from CATV cooperatives, which are sub- stationary images simultaneously. Bringing up this scriber-owned. feature on the TV set does not affect the audio por- Munsell (also Munsel) chroma See Chroma. tion of the broadcast. Munsell color chip chart A video test chart used to multistage LNA Three or more transistor amp stages check the color-producing ability of a video camera. placed end to end (cascaded) so that the gain con- Used more frequently by professionals, the Munsell tribution of each will add up to total gain of ap- chart contains specially prepared strips of color simi- proximately 50 dB. In most LNAs, the first stage lar to the familiar color bar signal that is generated (closest to the probe) has the best noise electronically. The chart can be used in conjunction characteristics needed to minimize the noise propa- with a color vectorscope. The user first points the gated along through the remaining stages. camera at the vectorscope, then aims it at the chart, multistage noise shaping An enhancement built into noting any differences. some audio clips that transfers unwanted noise into Munsell color scale A set of charts used in color TV inaudible portions of the frequency spectrum. This to verify hue, brilliance, and chroma. is accomplished by a digital-to-analog conversion Munsell value The dimension, in the Munsell system process, sometimes referred to by its acronym, of object-color specification, that indicates the ap- MASH. parent luminous transmittance or reflectance of the multistandard color decoder A circuit to automati- object on a scale which has approximately equal cally select the standard of the received signal and perceptual steps under the usual conditions of decode it. observation. multistandard switchable encoder A feature gen- MUSE Multiple Sub-Nyquist Sampling Encoding. The erally found on a high-priced professional video cam- Japanese bandwidth compression system to accom- era designed with special outputs to accommodate modate HDTV transmission within an existing satel- other formats, such as Beta, S-VHS and MII. lite channel. This system was an adaptation of the multistandard TV A digitally equipped TV receiver NHK HDTV system for the DBS service in the 12- capable of handling any video standard. Some of GHz band. It is known that the wide base band- the lower-end NTSC/PAL TV sets have reduced all of width of the 1125-line NHK system (more than 20 the complex, sophisticated electronic circuitry to one MHz) cannot be accommodated by the satellite tran- chip. sponders unless the signal is compressed. The MUSE

191 MUSE-6

system reduced the total video baseband require- ing. The omission of the frame was then not evi- ment to 8.15 MHz, suitable for the DBS service. This dent to the viewer. The MUSE-6 system was designed conversion retained the full detail of the 1125-line to operate as a part of the MUSE-9 system. image, but only when the scene was stationary. MUSE-9 Also NHK MUSE-9. A wide-channel NTSC- When motion occurred, the definition was reduced compatible system. Two channel arrangements were by about 50%. If a moving object appeared against proposed, the first with the 6-MHz and 3-MHz con- a stationary background, this loss was often not too tiguous, the second with the two channels sepa- evident. But if the whole scene was in motion, as rate. In common with all the MUSE systems, the when the camera moves (“pans”) to follow action, MUSE-9 system signal originated in the 1125/60/ the whole image suffered a 50% loss of detail. 2:1 format (SMPTE 240M standard). In the MUSE-6 MUSE-6 Also NHK MUSE-6. A single-channel NTSC- system, two audio channels of baseband 15 kHz compatible EDTV system (6-MHz band). The MUSE- were digitized at 32 Kb/s in 15-bit words that were 6 signal originated at the NHK standard of 1125 compressed to an 8-bit pulse train. This is the lines, interlaced 2:1 at 60 fields. For NTSC compat- A-MODE of sound transmission. The MUSE-9 aug- ibility, the 60-Hz rate was transcoded to 59.94 Hz, mentation channel provided two additional sound and this rate was maintained throughout the remain- channels at a wider baseband of 20 kHz, sampled der of the MUSE-6 system to the display. The parent at 48 Kb/s into 16-bit words. This is the B-MODE. MUSE system used time compression over three The augmentation channel transmitted the higher fields to reduce the baseband to 8.15 MHz. Since frequencies, so that two channels of B-MODE qual- this exceeded the bandwidth available in the NTSC ity were available in the MUSE-9 receiver, or four channel, an intermediate change of scanning from channels of A-MODE quality. The MUSE-9 receiver the total 1125 lines to 750 lines was encoded at the display operated at the same rates as the MUSE-6 transmitter and reverse decoded at the receiver. The receiver (1125/59.94/2:1), with the additional mov- display on conventional receivers offered a 16:9 as- ing-area horizontal resolution. pect ratio centered on the 4:3 frame, with 345 ac- music cues Directions that indicate the volume, level, tive lines. As in the parent system, the time starting and stopping time, and other changes for compression used in MUSE-6 introduced a 2:1 loss music used in films or TV. Music down is an instruc- in the horizontal resolution of moving objects. To tion to reduce the volume; music fade, to reduce it control the transcoding when motion was present, slowly until inaudible; music in, to start; music in a motion detector based on comparison of three and under, to start and then reduce (also called music successive fields generated a signal that disabled the up and under); music out, to stop; and music up high-frequency processing of moving objects. The and out, to increase and then stop. motion detector was also used to control the 1125- music/voice switch A tone control feature on some to 750-line converter and the 60- to 59.94-Hz field TV monitor/receivers. The music/voice switch is de- converter. The sound signal was digitized at 32 Kb/ signed to provide the full frequency range of the s in 15-bit words, with redundant bits to bring the audio system in the Music mode. When the switch data rate to 585 Kb/s. After compression, the digi- is placed in the Voice or Speech position, the bass tal audio was inserted in the video waveform after and treble responses are modified to minimize hiss the color burst. Overscan in conventional receivers and sharpen voices. was assumed to hide any evidence of the sound burst muting circuit An electronic feature built into virtu- during active scanning. One stereo-pair sound chan- ally all VCRs to minimize instability or noise in the nel was offered at 15 kHz upper limit. The receiver video signal. Some older model machines go to a decoding was the inverse of the transmitter encod- blank screen rather than display signal deterioration ing, with the exception of the field-rate conversion, such as picture break-up. However, in newer VCRs, which was omitted since the MUSE-6 display oper- this muting lasts for a fraction of a second. ated at 59.94 fields. The display therefore offered mux Multiplexer. only 999 frames for each 1000 frames scanned by M VTS Marconi Video Telephone Standard sends color the camera, and one frame in 1000 was discarded pictures over regular phone lines at up to 10 frames in the transmitter processing. This “frame-cut” op- per second at 14.4 Kbps. The MCI Video Phone, eration took place under the control of the motion which conforms to this standard, has a resolution of detector when there was a switch between cam- 128 by 96 pixels. eras or when the scene was stationary or slowly mov- MXR Multiplexer.

192 N

N 1. CATV superband channel, 240-246 MHz. 2. TV that meets the requirements of the compatible ser- standard; Argentina, Uruguay. Characteristics: 625 vice. The Narrow-Muse system, being a simulcast lines/frame, 50 fields/s, interlace-2:1, video band- noncompatible proposal, uses more fully the re- 4.2 MHz, RF band-MHz. sources of the 6-MHz HDTV channel. It was designed NABTS North American Basic Teletext Specification; primarily for the terrestrial service, simulcast with a North American Broadcast Teletext Specification (EIA- standard NTSC signal. Scanning (lines/field rate/fields 516). This is also ITU-R BT.653 525-line system C per frame)-1125/60/2:1; aspect ratio-16:9. Dropped teletext; however, the NABTS specification goes into from consideration in the U.S. in 1993. much more detail. This document specifies both the National Electrical Code (NEC) A comprehensive acquisition protocol and the display format. The dis- document detailing safety requirements for all types play format is NAPLS. of electrical installations. In addition to setting safety Nagra Syster Encryption system in European satellite standards for building wiring and associated ground- TV, the only one that is still relatively secure from ing, the Code also contains a section on Radio and signal hackers. TV equipment—Article 810. NAM Non-additive mix. A type of mix where the out- National Television Standards Committee (NTSC) put at any point in the picture consists exclusively of The group originally responsible for setting standards which input signal had the greater amplitude. This for commercial TV broadcasting in the U.S., Canada, is in contrast to a normal mix, which produces a and Japan. Organized in the US in 1940, the NTSC linear sum of the inputs. in 1941 conceived the black and white TV standards NAPLS ANSI X3.110-1983 Videotex/Teletext Presen- and by 1953 the color TV standards. It decided upon tation Level protocol syntax. This is not a display stan- 525 line scans made up of two fields of 262.5 lines dard. It applies to both TT and Videotex services. each and at the rate of one frame (two fields) every narration microphone A second microphone built 1/30 per second or 30 frames/s. into a video camera. This auxiliary mic allows the navigation The movement within a videotex system, videographer to record narration while shooting on such as from frame to frame, subject to subject, or location. database to database, based on menu choices. narrow-band axis The direction of the phasor that N connector A device to connect coaxial cable that is represents the coarse chrominance primary (the Q commonly used in the TV industry, including a large signal) in NTSC color TV; it has a bandwidth extend- screw-in N connector and a smaller twist-lock type— ing from 0 to 0.5 MHz. a baby N connector or BNC. narrow bandwidth optical filter A filter to pass only NCTA National Cable Television Association. A trade reflected light signals having the wavelength of the organization representing US cable-television laser energy. Used in 3D TV systems with laser carriers. projectors. NEC National Electrical Code. narrowcasting A term applied to special- or limited- neck The narrow cylindrical section of the CRT used in interest programming targeted at a small portion of TV sets and monitor/receivers. The neck extends from viewers. For example, the Christian Network and the funnel part of the tube to its base and contains other religious channels engage in narrowcasting, the electron gun. as opposed to broadcasting as carried by the major negative booster See Booster. networks, ABC, CBS and NBC. negative image An image in which white areas are Narrow-Muse system Also NHK Narrow-Muse sys- reproduced as black and black areas as white as in tem. A single-channel noncompatible simulcast negative . The effect can occur in HDTV system. The NHK Muse family of systems con- TV images when, for example, the picture tube has tains two proposals intended for 6-MHz channels. low emission. The Muse-6 system is an NTSC-compatible system negative match back A phrase used in TV produc-

193 negative modulation

tion editing, when the original footage was shot on of the video camera. For instance, without an NDF, film. The edge numbers on the film are transferred the sensitivity range may be from 5 to 6500 fc; with to the video time code on the videotape. Rough the filter in place, the range may drop to 40-50,000 editing is completed on film. The matching num- fc. A NDF is sometimes built into a camera, in which bers make the process easy. case it is activated by a switch. It is used in very bright negative modulation (US: downward modulation) In light such as snow scenes to give more flexibility to TV, transmission amplitude modulation in which in- the iris, which otherwise would be almost closed. creased picture brightness results in decreased car- Another use of the filter is to shorten the depth of rier amplitude. This technique is employed to field. Since the iris must be opened wider when the attenuate the energy transmission or bright images. filter is in place, only the subject focused upon will Overly bright scenes, otherwise, tend to cause buzz- be sharp while objects in the foreground and back- ing. Negative modulation is the system of modula- ground will be deliberately thrown out of focus. NDFs tion used in the American 525-line, in the British are sold in a variety of ranges that require the lens 625-line and in most of the world’s TV systems. Also to increase its F-stop one or more openings. See also called negative transmission. Neutral-density faceplate. negative picture phase The video signal phase in neutral gray Any level of gray with no color or hue. which the signal voltage swings in a negative direc- New Chroma Set See SMPTE [color] bars. tion for an increase in brilliance. new edge An all-encompassing term describing the negative/positive image switch See Image reversal. new technology and movement that promises to negative transmission Negative modulation. revolutionize communications and entertainment in nematic liquid crystal A liquid-crystal material whose the 21st century. elongated molecules are parallel to each other but Newvicon An image pickup tube designed by RCA are not in layers. Used in pocket TV sets. See also and manufactured by Matsushita known for its low- Smectic Crystal, Supertwisted nematic and Twisted- light capabilities and its resistance to burn. It helps nematic liquid-crystal display. to reduce smear, blooming and image retention. In Nesmith, Michael Creator of the first prerecorded ste- home camcorders, camera tubes are replaced with reo videocassette. Produced by Pacific Art, it was CCDs. released in 1981. next function A feature, found on some VCRs, that network 1. A group of radio and TV stations that are allows the user to switch directly from Rewind to interconnected by cable or microwave link so that another mode. When Rewind is pressed, followed they can broadcast the same program simulta- by another selected mode such as Eject or Play, the neously. 2. A group of devices such as radio trans- “next memory function,” as it is sometimes called, ceivers that are organized to form a large system. 3. will activate the unit to rewind the tape and then A group of computers or terminals coupled together proceed to automatically execute the second to form a system such as a local area network (LAN) function. or (WAN). NexTView An electronic program guide (EPG) based network identification The name of identification on ETSI ETS 300 707. of a radio or TV network, made at the beginning of NF Noise Figure. each hour and/or the beginning and end of network NHK Nippon Hoso Kyokai. Japan Broadcasting programs. Company. neutral angle A camera angle with the action directly NHK Muse-6 System See MUSE-6 system. in front of the camera at about eye level. NHK Muse-9 System See MUSE-9 system. neutral color A color without hue, matching other NHK Narrow-Muse System See Narrow-Muse colors well, as gray does. A neutral-density filter is a system. gray filter that reduces exposure. NICAM 728 A technique of implementing digital ste- neutral-density faceplate A TV picture-tube face- reo audio for PAL video using another audio subcar- plate into which a neutral-density filter has been in- rier. The bit rate is 728 kbps. It is discussed in BS.707 corporated to increase picture contrast by and ETSI EN 300 163. NICAM 728 is also used to attenuating external light reflected from the screen. transmit non-audio digital data in China. Reflected light must pass through the filter twice nickel-cadmium battery A battery used with portable and be doubly attenuated, whereas the desired light VCRs and most camcorders that can be charged in from the screen passes through only once. less than two hours. The NiCad battery is more ex- neutral-density filter (NDF) An optical filter that re- pensive than the alternative battery, the lead acid duces the intensity of light without appreciably type, also found in portable systems. changing its color. Also called a gray filter. 2. A trans- nicol prism A prism made by cementing together two parent piece of smoked glass (or similar substance) pieces of transparent crystalline spar with placed on the front of the lens to restrict the amount Canada balsam. It produces plane-polarized light of light entering it, thus affecting the sensitivity range from ordinary unpolarized light by eliminating the

194 non-additive mix

ordinary component of the original light by total re- program in one of the normal tape speeds and the flection at the cementing layer. Only the extraordi- other two heads for playing back special effects. nary component passes. Other VCRs have adopted digital recording, as op- Nipkow disc Mechanical scanning device used in early posed to , to eliminate the annoy- experiments in TV. It consists of a disc containing a ing noise bars and produce a better image generally. number of apertures arranged on a spiral path. The noise figure Measurement of noise contribution of scene to be televised is illuminated by light which an amplifier relative to a noise-free amp at a refer- passes through these apertures so that, as the disc ence temperature; dB. revolves, the scene is scanned. Light reflected from noise limiter In a radio or TV receiver, a circuit used to the scene is picked up by photocells, the output of reduce the effect of impulsive noise signals on the which is the required picture signal. The system was sound or picture output. Typically the circuit includes used in the BBC 30-line TV experiments in the late a series diode situated at the output of the detector . and is so biased that it remains conductive for all NN CATV hyperband channel, 378-384 MHz. normal amplitudes os sound or video signal but be- Noctovision A TV system that views an infrared (IR) comes nonconductive so interrupting the wanted image rather than a visible light image and is some- signal for the duration of any noise pulse exceeding times used at night. A specially designed IR-sensi- a pre-determined amplitude. The resulting interrup- tive camera tube produces a video signal that can tions are normally so brief that their subjective ef- be detected by a standard receiver. fect is negligible. noise In general any unwanted signals within the use- noise reduction system (NRS) A system designed to ful frequency band of a communications system that improve the sound quality of an audio or video unit tend to obscure the wanted signal. This is a wide by cutting down on the amount of hiss, thereby re- definition and embraces a variety of man-made moving most of the noise without affecting high noises such as mains hum, signals from other chan- frequency response. There are various kinds of au- nels arising from inadequate selectivity or poor im- dio NRSs: Dolby, CX, dbx, Dynamic Noise Filter (DNF), age rejection, cross modulation, etc.; it also includes Dynamic Noise Reduction (DNR), etc. Most NRSs naturally generated signals arising from lightning operate on a compression/expansion principle. Each flashes. Signals from such causes are better termed system, however, goes about this in a different way. interference so that the term noise is reserved for DNR and DNF are unlike the others listed above, signals which arise in components and active de- which mainly expand audio signals during record- vices and are known as random noise. Such signals ing and condense them during playback. Instead, are termed noise because they are heard as undes- these two systems employ a dynamic filter which ired sound when reproduced by an acoustic trans- eliminates high frequencies (mostly noise or hiss) ducer but the term is retained for signals which cause whenever the signal is not strong enough to cover spurious detail on the screen of a CRT. Random noise this noise; but when the signal does cover the hiss, from components is known as thermal noise or the filter lets the high frequencies through. Another Johnson noise and from active devices is known as way in which DNR and DNF differ is that they func- shot noise or partition noise. Even if all sources of tion only in playback to minimize existing noise while man-made noise can be eliminated there still remains Dolby and most of the other cannot reduce noise random noise and the level of this noise determines already in the signal. They have to be utilized during the amplitude of the weakest signal which can be recording and playback, encoding and decoding the successfully transmitted through a communications signal. system. Wanted signals must exceed the noise level noise temperature Noise measurement of a system, by a margin that ensures that the noise does not as the absolute temperature of a resistive source de- impair the intelligibility of the signal unduly or the livering equal noise power; degrees K. enjoyment of the program. Thus the noise level and nominal viewing distance Distance between viewer the signal-to-noise ratio are two important proper- and TV picture at which the TV raster line structure ties of a communications system. In TV, noise usu- becomes invisible. E.g., for 625-line systems the rec- ally means random or thermal noise of a type that ommended viewing distance is from five to seven produces “snow” in a TV image. See Video noise. times screen height. noise bar A horizontal line across the TV screen, usu- nominal white level Level of video signal correspond- ally caused by misalignment of video heads and tape. ing to the white areas of a TV picture with nominal Noise bars often occur in special effects mode such brightness. It depends on the color TV system and as fast search or freeze frame. Some VCRs are rela- usually serves as a 100% reference level to calibrate tively free from these noise bars, also known as in- the gains and settings of measurement devices. Syn.: terference, noise or video noise. These machines reference white level; white level. accomplish this in one of two ways. Some have four non-additive mix (NAM) A type of mix where the video heads, two for recording and playing back a output at any point in the picture consists exclu-

195 noncomposite color-picture signal

sively of whichever input signal had the greater am- until the final sequence is ready. The editing con- plitude. This is in contrast to a normal mix which, sole then reproduces the selected sequence from produces a linear sum of the inputs. the original material onto a different tape on an- noncomposite color-picture signal (US) In TV, the other deck. An early nonlinear editing system used signal that comprises full color-picture information, a computer disc that stored the scenes to be edited. including the color burst and blanking information The disk provided almost instant access to any point. but excluding the synchronizing signals. When TV These systems are both time-savers and creative de- pictures are generated and processed within the vices. Some nonlinear editing systems, sometimes technical area of a studio, it is not always necessary referred to as tape-free editing systems, use a stor- for the picture signal to be accompanied by syn- age system of several laserdiscs. Selected dialogue, chronizing signals. Where a number of picture effects and music can be recorded directly onto the sources have to be handled within a studio area, an discs from videotape without external facilities. economy can be made by providing comp sync sig- Each video frame and sound bite is then instantly nals only at the final processing point. This non-com- available to the editor by way of a keyboard and a posite mode of operation has the advantage that control wheel. sync distribution requirements are reduced to a mini- non-return-to-zero (NRZ) A binary encoding scheme mum, with resultant installation economy. Also, in which ones and zeroes are represented by oppo- when the comp sync is finally added to the picture site and alternating high and low voltages and where waveform, no stripping of existing sync is required. there is no return to a zero (reference) voltage be- This process of sync stripping always gives rise to tween encoded bits. some degree of picture distortion, and the fewer non-return-to-zero-inverted (NRZI) A binary encod- times it is performed, the better is the resultant pic- ing scheme that inverts the signal on a “one” and ture quality. On the other hand, preview monitoring leaves the signal unchanged for a “zero,” where a of the various picture sources within the studio com- change in the voltage signals a “one” bit, and the plex demands either comp sync feeds to the moni- absence of a change denotes a “zero” bit value. tors, or comp video signals from the picture sources. Also called transition coding. Owing to the number of monitors involved, the com- nonstorage camera tube A TV camera tube whose posite video mode of operation is usually adopted. picture signal is at each instant proportional to the nondrop SMPTE time code format for black and white intensity of the illumination on the corresponding video signal (30 fr/s). See also Drop frame. elemental area of the scene at that instant. noninterlaced 1. Refers to displays and video stan- nontransitional digital video effects Refers to cor- dards that do not use interlacing techniques to im- recting visual errors that appear on original video- prove resolution. This is the standard system used in tape by using special equipment such as a digital computer monitor displays. 2. An enhanced scan- video effects system during post-production editing. ning system utilized by some manufacturers of IDTV. A video camera operator may inadvertently pick up This system doubles the number of scan lines (from on tape an unwanted shadow, window glare or part 262.5 to 525 every 1/60 s for NTSC). The result re- of an overhead microphone. The DVE system allows portedly improves vertical resolution by eliminating the editor to eliminate these intrusions by enlarging the visible spaces between scan lines. Viewers of the picture until the intrusive image is no longer in conventional TV images are often distracted by the view. This type of function differs from transitional horizontal lines that make up a screen image, par- digital video effects. ticularly on larger sets. Instead of presenting two normal lens A subjective evaluation of the angle of separate groups of lines (each composed of 262.5 view of a lens; a normal lens is one that is neither lines for NTSC), one following the other, wide angle nor telephoto. See Fixed focus lens. noninterlaced display produces both sets of lines at North American Basic Teletext Specification one time. This creates a picture of greater density. (NABTS) A standard that specifies the coding sys- See Progressive scanning. tem for services. It is based on the videotex stan- nonlinear A term used to refer to both editing and dard developed by the ANSI and CSA. storage of video, audio, and data. Information (foot- notch filter 1. A band-rejection filter that produces a age, data, etc.) is available anywhere on the media sharp notch in its frequency response curve of a sys- immediately, with no waiting to locate the desired tem. In TV transmitters it provides attenuation at information as in a time linear format. the low-frequency end of the channel to prevent nonlinear distortion See Distortion. possible interference with the sound carrier of the nonlinear electronic editing A process that does not next lower channel. 2. A TV monitor/receiver circuit limit the editor to follow a particular order or length that helps to eliminate horizontal interference of of events in assembling a finished tape. Advanced video noise that occasionally shows up on the edge editing techniques and digital editing consoles al- of the screen. The notch filter suppresses an annoy- low designated sequences to be stored in memory ing frequency segment of the chrominance signal

196 Nyquist limit

that often affects color contrast. Since these filters ters a chroma demodulator that separates the dif- may also affect the sharpness of the screen image, ference signals into the three basic color signal com- some manufacturers add a manual notch filter switch ponents. These RGB signals drive the TV tube to the monitor. See also Op amp active notch filter. electron beams and display the picture. A sample NRZ Non-return to zero. A coding scheme that is po- of this video signal is also fed to the synchronizing larity sensitive; usually a low signal level means logi- circuits. The timing pulses, which are an integral cal “0” and high level means logical “1.” This coding part of the signal, are stripped away in the sync scheme suffers the disadvantage that it contains fre- separator. These send correct voltages to the de- quency components from D.C. and is thus unsuit- flection circuitry to produce the organized picture able for many applications. An example of NRZ is a scanning. simple RS232 serial data link. NTSC, color TV signal The three raw color signals NRZI Non-return to zero inverse. A scrambling scheme (RGB) from a TV camera are combined to create the that is polarity insensitive; usually a low signal level luminance signal (Y) and two difference signals (I means no change in logical values and high level and Q or U and V). The luminance information is means transition from one logical value to another, sufficient to recreate a black and white picture. The for example, from “0” to ”1” or from ”1” to ”0.” difference signals are modulated onto two 3.58-MHz This coding scheme has the advantage that it con- carriers having phases differing by 90 degrees and tains no D.C. component, which makes it more suit- then are combined to form the color signal (C). The able for the majority of applications. Y and C signals are mixed together into the base- NTC-7 combination Vertical interval test signal speci- band composite video signal for modulation onto fied by NTC (a US body) for the NTSC system. It com- an RF subcarrier. The 3.58 MHz subcarrier must be bines the feature of VITS test lines CCIR-18 and relayed along with the composite signal so that the CCIR-331. Syn.: NTC combination. raw color signals can be properly extracted from the NTC-7 composite Vertical interval test signal speci- difference signals. fied by NTC (a US body) for the NTSC system. Simi- NTSC compatible Any HDTV system that will operate lar to VITS test line CCIR-330. Syn.: NTC composite. with NTSC signals. NTC combination See NTC-7 combination. numeric keypad That pad of a remote control con- NTC composite See NTC-7 composite. taining the 10 numeric keys designed to operate NTSC National Television Systems Committee, the stan- various functions. With a VCR or TV set, for example, dardizing body that in 1953 created the color TV the chief function of the numeric keypad is to change standards for the USA. This system is called the NTSC channels. With a VDP, on the other hand, the key- color TV system. pad serves to control direct chapter and track search. NTSC-4.43 Nonbroadcast color TV system primarily nut The total cost of a radio or TV program, produc- used when certain PAL equipment is used for play- tion, or sponsorship. ing back consumer NTSC tapes with the color-un- NVOD Near video on demand. Rapid access to pro- der subcarrier heterodyning to 4.43 MHz instead of gram material on demand handled by providing the 3.58 MHz. same program material on several channels with NTSC-7 See VITS. staggered start times. NTSC, basic TV receiver A signal enters via either Nx384 N-by 384. The CCITT’s approach to creating a the VHF or UHF terminals and is connected to the standard algorithm for interoperability. appropriate tuner. This circuit component is respon- It is based on the CCITT’s HO switched digital net- sible for selecting one channel or frequency band. work standard, which was expanded into the Px64 An NTSC VHF tuner must be capable of spanning or H.261 standard, approved in 1990. the range from 54 to 216 MHz or from 54 to 456 NYIT New York Institute of Technology. MHz for cable-ready receivers. A UHF tuner accepts NYIT/Glenn vista system See Vista system. frequencies ranging from 470 to 806 MHz. The out- Nyquist frequency The minimum sampling frequency put of either the VHF or UHF tuner is a common IF for correct digital reproduction of a given signal of 45.75 MHz centered on any selected 6 MHz (twice the signal bandwidth). Also Nyquist rate. channel. This IF is bandpass filtered to remove any Nyquist limit In sampling, the highest frequency of unwanted signals from adjacent channels. The sig- input signal that can be correctly sampled. The nal is fed to a detector which extracts the compos- Nyquist limit is less than one-half of the sampling ite baseband signal. The signal is then filtered to frequency. A definite rule must be observed in sam- remove the 4.5 MHz audio subcarrier. Prior to fil- pling an analog signal if it is to be reproduced with- tering, a portion of this video signal is tapped off out spurious effects, known as aliasing. That rule is and sent to the audio detection circuitry. Once the that the time between samples must be short com- 4.5 MHz subcarrier is isolated and demodulated, it pared to the rates of change of the analog wave- is filtered and amplified and fed to a speaker. The form. Nyquist first stated this rule in 1924. In video “clean” composite video baseband signal then en- terms, the sampling rate in megasamples/s must be

197 Nyquist theorem

at least twice the maximum frequency in MHz of higher-frequency copies of the input spectrum that the analog signal. Thus, the 4.2 MHz maximum in have been moved down so that they overlap the the luminance spectrum of the NTSC baseband re- desired output spectrum. When this output analog quires that the NTSC signal be sampled at least at signal is displayed, the spurious information shows 8.4 megasamples/s. Conversely, the 13.5 up in a variety of forms, depending on the subject megasamples/s rate specified in the CCIR studio digi- matter and its motions. Moire patterns are typical, tal standard can be applied to a signal having no as are distorted and randomly moving diagonal higher frequency component than 6.75 MHz. If stu- edges of objects. These aliasing effects often cover dio equipment does exceed this limit, and many cam- large areas and are visible at normal viewing dis- eras and associated amps can do so, a low-pass filter tances, so care must be taken to meet or exceed the must be inserted in the signal path before the con- Nyquist limit in all analog-to-digital conversions. version from analog to digital form takes place. A Nyquist theorem In communication theory, a formula similar band limit must be met at 3.375 MHz in the stating that two samples per cycle is sufficient to chrominance channels before they are digitized. If characterize an analog signal. In other words, the the sampling occurs at a rate lower than the Nyquist sampling rate must be twice the highest frequency limit, the spectrum of the output analog signal con- component of the signal. See Nyquist limit. tains spurious components, which are actually Nyquist volume See Spatiotemporal analysis.

198 O

O CATV superband channel, 246-252 MHz. oersteds of coercivity Refers to the density of par- OAB Office Automation Board. ticles of a videotape; thus it is a method of measur- objective lens The first lens through which rays pass ing the ability of tape to store information. in an optical or electronic lens system. off air A program received via conventional radio or O.C. Also OC. On Camera. Action in front of a TV TV and not via cable. “Off the air” refers to the end- camera, visible to the audience. In a TV script, a ing of the transmission of a program or the termi- direction indicating on which person or scene the nation of a program. camera is focused. off-air video recording The practice and the right of OC3 Optical Carrier Level 3, a 155-Mbps ATM SONET the public to record TV programs off the air from signal stream that can carry three DS3 signals. broadcast stations for later viewing in the home. OCS Osborne Compression System. office automation board (OAB) See Electronic black- octal code A base-8 number system, which uses just board. eight unique symbols: 0,1,2,3,4,5,6,7. In the octal off-line editing Refers to the reorganizing of material system, the binary numbers are defined in groups on a videotape in preparation for editing but with- of three and assigned decimal numbers in sequence out actually recording the new arrangement. This (8 and 9 are omitted). Most digital TV systems use may be done by electronically marking different seg- 8-bit words that can identify 256 values. This is usu- ments of the tape or by composing a list of them. ally adequate for the video signal itself, but it is some- Usually a rough cut is produced which can be re- times desirable to go to 10-bit words for the ferred to in a high-quality on-line suite, reducing transmission of data or auxiliary functions, as 10-bit decision-making time in the more expensive on-line words can identify 1024 values. environment. See On-line editing. octave A doubling of the frequency; for example, the offset binary code A code that can express negative audio frequency range is about 10 octaves (20 Hz numbers in a digital format. This is achieved by add- to 20 kHz), and the approximate range of video fre- ing a fixed amount to the analog signal before it is quencies to be recorded and played back for TV video sampled and quantized so that the sum is always is 30 Hz to 4.5 MHz, or 18 octaves. positive. In the CCIR-601 standard, for example, the octopus cable Any cable with a number of different blanking level for the analog color difference sig- jacks at one or both ends; a cable that allows two nals is set at the quantum level 128, and signal ex- pieces of video equipment with dissimilar jacks to cursion is from 16 to 240. The corresponding binary be interfaced. numbers are 00010000 and 11110000 in the offset odd field Field with odd number in the interlaced field binary code. The offset binary code is also used for sequence. composite signals and to avoid clipping. odd-line interlace Interlace in which each field con- offset-fed antenna An antenna with a reflector that tains an extra half-line. Thus, in the standard 525- forms only part of a paraboloid of revolution, usu- line TV picture, each field contains 262.5 lines. ally excluding the pole or apex, such that a front oe See Oersted. feed causes no aperture blockage. Used in satellite o/e Optic-to-electric conversion. TV. OEM Original equipment manufacturer. A company offset signal Signal sometimes encountered with that produces units for other companies. For ex- CATV converters, MATV systems, home video games, ample, Hitachi supplies Pioneer with its VCRs, and video recorders that falls in a range +/–2 MHz whereas Matsushita makes VCRs for General Elec- around the FCC assigned VHF broadcast channel tric, Magnavox, Panasonic and other companies. frequencies. oersted (Oe) The unit of magnetic field strength H in off-tape monitoring A technique used in some pro- the CGS system until 1930, when it was replaced fessional video machines that permits viewing the by ampere/m as the SI unit. videotape as it is being recorded. This is accomplished

199 off the air

by employing two additional video heads utilized video cameras offer this unit as optional, in which expressly for playing back the information as it is case it is usually connected to the bottom of the recorded. In copying tapes on home VCRs using two camera or to a removable shoulder pod. monitors, the picture played back from the set con- on-deck In TV, to be ready. nected to the recording VCR is not the one being on-deck camera A TV camera whose picture is cur- recorded, but the signals the VCR is receiving and rently not being transmitted despite its readiness to transmitting to the TV set. Conventional home video become an on-air camera. recorders have two or four heads that either record on-demand streaming Streaming media content or play back; they cannot do both simultaneously. transmitted to a client upon request. off the air 1. Refers to broadcasting through the air- one-and-one-half heads principle A system with a waves and is used in radio and TV. TV viewers may separate head that records the vertical information pick up signals off the air instead of by coaxial cable near the lower edge of the tape, used in teletext through a cable system. 2. See Off air. and systems with special signals inserted outside the off timer A built-in clocktimer which may be set to regular picture area. The 1.5-heads system thus re- turn off the TV after a preset time interval has tains such special signals as VIR signals and VITSs. elapsed. one-inch A helical scan VTR format that uses 1"-wide OIRT French acronym for International Radio and Tele- tape in an open-reel configuration and is close to vision Organization, headquartered in Prague. This 2" Quadraplex in broadcast quality. was the Eastern Europe regional broadcasters’ union. one-inch vidicon A vidicon tube with a target area In 1993 it merged with EBU. 1" in diameter. omni Short form for omnidirectional microphone. one-touch recording (OTR) A convenience feature omnidirectional microphone A microphone designed on many VCRs designed to provide a simple proce- to respond to sound from all directions. It is particu- dure for instant recording without the normal pro- larly effective when recording more than one per- gramming steps. With either the ordinary power or son in a scene. Used by most video cameras, the the timer on and the proper channel tuned in, each omnidirectional microphone is recommended for touch of the OTR button activates the Record mode close recording. for either 15 or 30 minutes. With some VCRs, the OMT Orthogonal-Mode Transducer or ortho-coupler: first touch of the OTR button activates the Record waveguide component that separates or combines mode while each successive touch gives 30 minutes two orthogonally polarized signals. Used in satellite of recording time up to a total of 4 or 5 hours. These TV. times vary, depending on the VCR. When OTR is on-air An indication that a particular device is “on- pressed, all other functions cease to operate, as in line”—that is, its signal is being transmitted, it is the typical timer position of other machines. monitoring an active signal, etc. This indication, usu- one-tube color camera A color-capable video cam- ally a lamp or LED, can be on the switcher itself, or era, which produces a color signal through the use on a remote piece of equipment, such as a monitor of only one pickup tube. or a camera. A source’s tally is activated automati- one up/many down A TV or teleconference format cally when the source is selected via the mixer’s pro- with a single origination site and many receiving sites. gram bus. Syn.: on-line. on-lay Keying mode when the mixer creates a key on-air switcher The switcher used to determine what signal from the video that will itself eventually fill goes to the transmitter. It generally coordinates the hole. A common example is simple insertion of sources of finished production and sends output di- captions (generated with a black background) over rectly to the transmitter. The on-air switcher switches the desired program output. In this case any lumi- between various videotape machines, film chains, nance value above black can be easily detected to network feeds, satellite feeds, and the studio. These make a key signal for the captions. Syn.: self key. switchers are almost always audio-follows-video on-line An indication that a particular device is active. switchers. That means that when the technical di- This indication, usually a lamp or LED, can be on the rector pushes a button on the switcher, it changes switcher itself, or on a remote piece of equipment, both the picture and the sound. On-air switchers such as a monitor or a camera. A source’s tally is usually have limited special effects capabilities; any- activated automatically when the source is selected thing going to the transmitter is usually a finished via the mixer’s program bus. Syn.: on-air. product—there’s little need for special effects at this on-line editing The final recording onto a videotape stage. at full program quality based on rearranged mate- on-camera remote control A feature on or added to rial from an original tape. See Off-line editing. a video camera for starting or stopping the VCR, on-off keying (OOK) A form of ASK, modulation mode switching between Record and Playback modes, used in digital TV transmission. Transmission speed: using Forward and Reverse Visual Scan and operat- 0.8 bits/Hz. ing Freeze Frame and Single-Frame Advance. Some on-screen clock A feature, found on some TV sets

200 optical amplifier

and virtually all TV monitor/receivers, that presents opaque projector A projector that telecasts an en- the time and day in large figures, usually operated larged image of flat material, such as printed pages by a remote control button. of an open book, by using a light source that shines on-screen display A menu or set of menus of a TV directly on the object; also called a balopticon. It is or other component that appears on the screen not the same as an overhead projector, which shines and is designed to help perform certain operations. light through a transparency rather than an opaque A TV monitor/receiver, for example, may include object. menus for current time set, on/off timer; video ad- opaque screen A nontransparent—opaque—mate- justments of hue, color, brightness and sharpness; rial on which an image is produced by reflected light or audio adjustments of treble, bass and balance— from a projector in front of the screen (not rear all tuned by remote control. A VCR display may projection screen). include prompts for programming the timer or op-com Optical communication. checking the day and time functions. These items open architecture receiver See MIT-RC system. and more are usually found on the remote control. open architecture television A concept designed to Some of these menus have submenus for even do away with or limit TV obsolescence by allowing more subtle adjustments. new circuit modules to replace old ones. The idea is on-screen graphics A picture-in-picture (PIP) display to make the TV receiver so accessible that further menu for the adjustment of the inset picture in ad- advances in technology and equipment can be as- dition to other on-screens displays. signed to plug-in boards. These accessories, when on-screen programming A VCR feature that per- inserted into TV sets, provide the receivers with the mits the machine to be set up for recording by menu necessary improvements so that they do not have displays on the TV screen. Usually operated by re- to be discarded. mote control, on-screen programming provides ei- OpenCable A project to make available a new gen- ther summary-style menus or individual program eration of set-top boxes that are interoperable and menus. Other special features include flashing enable a new range of interactive services to be pro- prompts that ask for the next item to be entered or vided to cable customers. a changing line that lists the possible options. Once open channel A channel on a TV receiver or a VCR a feature only of the more costly VCRs, the on-screen that is not occupied by a local broadcaster. In most programming function has trickled down to less ex- communities channel 3 or 4 is considered an open pensive models. channel and can be used for transmitting a signal on-screen prompt A flashing or blinking sign or word from a VCR without interference or bleed through. that appears on the TV screen and is designed to Virtually all VCRs have a switch in the rear for se- cue the viewer to enter information. Usually part of lecting either of the two open channels. a VCR’s on-screen programming feature, the prompt open information Text, data, and images accessible shows up in conjunction with certain menus that to all videotex subscribers; hence, public informa- make programming easier and virtually error-proof. tion is open information. Examples are train and air- Information may be entered from the remote line timetables, restaurant guides, and general news. control buttons. open subtitles See subtitles. on the line A term used in video production with a OpenTV™ Digital interactive TV “operating environ- special effects generator (SEG) to identify the signal ment” jointly developed by Sun Microsystems and that is leaving the SEG for broadcast or recording; Thomson Consumer Electronics. It provides “open the camera signal being fed out of the SEG to VTR interfaces” based on industry standards and proto- is said to be on the line. cols. OO CATV hyperband channel, 384-390 MHz. See TV open up See Stop down. channel assignments. (OS) The underlying program that O&O Initials for a TV station that is “Owned and Oper- manages a computer or set-top box and designates ated” by one of the networks. control of the various functions for general-purpose OOK On-off keying. use. Common examples of operating systems are Win- op amp Operational amplifier; a differential amplifier dows, Mac OS, Unix, and . with very high gain, used in many circuits such as Optest A computer-operated test and measurement amplifiers, filters, etc. system for devices such as video cameras and moni- op amp active notch filter A circuit that rejects all tors; Genop, Ramat Gan, Israel. Optest reduces op- signals in a very narrow range, while passing all oth- tical hardware use, operating via Windows. ers, resulting in a sharp “notch” in the frequency optic 1. Pertaining to the eye. 2. Pertaining to the response curve. This type of filter is found in TV cir- lenses, prisms, and mirrors of a camera, microscope, cuitry, where it is used to sharply attenuate levels at or other conventional optical instrument. one end of a channel’s signal to prevent interfer- optical A reference to visible or near-visible light. ence with the next channel. optical amplifier An optoelectronic amp whose elec-

201 optical animation

tric input signal is converted to light, amplified as compared to an electronic viewfinder). Similar to the light, then converted back to an electric signal for viewfinder on less costly still cameras, it is usually the output. found on the more inexpensive cameras. It provides optical animation A professional video technique no data about focusing or lighting. It can be supple- using image processing and computer-generated mented by a TV monitor connected to the camera; programs to create animated screen images. The however, this procedure limits mobility. Rarely used process usually provides sophisticated swooping and now. Other types of finders include the through- spinning enhancements along complex motion paths the-lens and electronic viewfinder, the latter being that provide professional results. the most prevalent. optical axis 1. The straight line that passes through optics 1. The branch of science concerned with the the centers of curvature of the surfaces of a lens. phenomena of light and vision, involving the por- Light rays passing along this direction are neither tion of the electromagnetic spectrum between mi- refracted nor reflected. 2. In a quartz crystal, the Z crowaves and X-rays. This range includes ultraviolet, axis is the optical axis that runs lengthwise through visible, and IR. 2. In film, TV, visual techniques to the mother crystal from apex to apex. produce optical illusions; also called effects. optical center The point in a lens at which the image opt out The moment during a network news trans- is collected to be focused on the image plane. The mission or other live feed when a local radio or TV distance between the optical center of a lens and station has the option of discontinuing and return- the image plane is described as the focal length. ing to its own programming. optical communication (op-com) Communication Oracle Optical Reception and Announcements by over short distances with beams of visible, IR, or ul- Coded Line Electronics, the teletext service of the traviolet radiation, or over much longer distances Independent Broadcasting Authority in UK, replaced with laser beams modulated by the information sig- by Teletext Ltd. nals (speech, pictures, data pulses, etc.). Oracle Media Net™ Software that distributes inter- optical disc or disk A digital medium, also called an active multimedia services over the different wiring optical memory disc or optical storage disc, in which connecting to users, including twisted pair wires lasers are used to record and replay the datatext, using asymmetrical digital subscriber line compres- graphics, images, or sound. sion; coaxial and fiber-optic cable using ATM; and optical flop Flopover. wireless connections. optical illusion A visually perceived image that is de- orbital arc See Orbital slot. ceptive or misleading. orbital slot A fixed position of a satellite on the geo- optical memory disc See Optical disc. synchronous orbit identified by its longitude. By in- optical recording Refers to a device in which audio ternational agreement, each country is allocated an and video information is encoded by a laser beam arc of the geosynchronous orbit for its satellites, and onto a rotating disk and whose signal is read by a the slots within this arc are assigned to individual beam of laser light. Information is recorded on the licensees by the country’s regulatory authority, the media as a change in the material characteristics. FCC for the US. The US is allocated the arcs 62-103 The compact disk (CD) format and digital video disk and 120-146 degrees west longitude for C-band sat- (DVD) format are two examples. ellites and 62-105 and 120-136 degrees west longi- optical scanner In video, a pen-like device used in tude for the Ku band. The slots allocated to Canada conjunction with a programming card to transmit are in the gaps in the US arcs. information to a VCR. Part of the bar code program- ordinary component The component of light that is ming process, the optical scanner is used by the VCR totally reflected at the cementing layer of a Nicol owner to mark the day, time and channel to be re- prism. Only the extraordinary component, which is corded. The information is then sent by IR beam to plane-polarized, passes through the prism. the VCR and can be confirmed on the TV screen. orthicon A camera tube whose low-velocity electron optical stabilization, camcorder. Compensates for the beam scans a photoemissive mosaic that is capable shake that is inevitable in hand-held shooting. Uses of storing a pattern of electric charges. It is an early vari-angle prism and motion sensors. Unlike elec- camera tube of the 1930s. The orthicon improved tronic image stabilizers, optical stabilization does not upon the primitive iconoscope and image dissector require a higher grade of image sensor to deliver tubes, both of which required extremely bright the same resolution as nonstabilized cameras, and scenes to reproduce an image. The orthicon was re- the image does not have the jittery pixel-movement placed by the image orthicon tube in 1945 and was artifacts often seen with electronic systems. considered the first dependable and sensitive pickup optical storage disc See Optical disc. tube. By 1952 it, too, succumbed to an improved optical viewfinder A mechanical device on a video version, the vidicon, a smaller and less bulky tube. camera that gives an approximation of what the lens ortho-coupler See OMT. sees without any playback or review capabilities (as orthogonal-mode transducer See OMT.

202 overshoot

orthogonal sampling Sampling with orthogonal ing apparatus. A live outside broadcast uses a por- structure—i.e., in such a way that corresponding table transmitter to relay the broadcast signal to the samples in each TV line align vertically. main control center where it is broadcast from the orthogonal scanning Scanning in which the electron main transmitters. If the broadcast is not live it is beam always approaches the target at normal inci- usually recorded on film; VTRs are now also used. dence. This is necessary in low-velocity camera tubes See also Electronic news gathering, Remote. such as orthicons to achieve cathode-potential sta- outtake Also out-take, out take, outs. Unused video- bilization of the whole area of the scanned face of tape; a section or scene that is taped but not used the target. in the final version for editing or other reasons. OS-9 Real-time operating system that directs opera- overenhancement A result of rotating the enhance tion of some home TV set-top boxes; Microwave control of an image enhancer too far. Systems Corp., now owned by Radisys. Used to make Overenhancement causes thin outlines to appear online interactive entertainment available via TV around the edges of the TV picture. The ideal ad- set-top boxes. justment involves moving the control to a point oscillator 1. A circuit that generates AC at a frequency where the picture appears sharp but slightly grainy. determined by the values of its components. For Then the response control takes over, reducing the stable frequency characteristics, the circuit can in- noise as much as possible without affecting the clude a crystal: PAL-, NTSC-decoders in TVs, VCRs, sharpness or detail in the picture. etc. 2. The stage of a superheterodyne receiver that overlap The running of two VTRs in synchronization generates an RF signal of the correct frequency to so that a changeover can be made from one to the mix with the incoming signal and produce the IF other; a segment of a dissolve in which the images value of the receiver: TV/VCR tuners. 3. The stage of are superimposed and the shooting of scenes longer a transmitter that generates the carrier frequency than necessary to provide leeway in editing. of the station or some fraction of the carrier fre- overlay Self-keyed insert; moving matte insert. An in- quency: TV transmitters. sertion effect in which the fill signal is a moving ob- oscillator radiation The field strength produced at a ject, which determines its own parameters as it moves. distance by the local oscillator of a TV or radio Oversampled VBI Data See Raw VBI Data. receiver. oversampling A digital video feature that uses a fre- oscilloscope A testing instrument that measures elec- quency several times higher than the standard rate tronic signals. It is used to align video components. for filtering purposes. Oversampling transfers the The oscilloscope, also known as a waveform moni- noise band to a higher frequency, allowing a sim- tor by video professionals, may be a portable field pler analog output filter to eliminate much of the model that offers limited features such as vertical higher frequency distortion. The standard centering for adjusting blanking to zero IRE, rota- oversampling rate is 44.1 kHz. The higher the tion, sweep rate, IRE filter and gain boost. The fully oversampling number, the more desirable the result. featured studio waveform monitor is designed to Some CD players include an 8x oversampling digital provide more sophisticated signal analysis. filter, which places these units far above other mod- OTR One touch recording. els, generally rated at 4x oversampling. outband system Scrambling system, used on CATV, overscan A term used in reference to a video camera’s in which the premium video channel is sent with optical viewfinder that usually views more than the either suppressed or missing sync pulses. Another lens captures on the tape. Also the scanning of a channel is used on the cable as the “carrier.” This greater area of the camera target than is normally (sync) channel is placed usually somewhere around used, effected by increasing the scanning currents, 50 MHz (below Ch 2), or in the 90- to 110-MHz and hence the magnetic fields. In TV, overscan re- range (in FM broadcasting). fers to a larger image, of approximately 10-15%, out-of-band signaling Signaling that is separated projected by the electron gun than the one seen on from the channel and carrying primary information— the face of the TV tube. Manufacturers of TV receiv- the voice, data, video, etc. Typically the separation ers deliberately employ overscan, since a TV image is accomplished by a separate tuner and filter. The shrinks as the set ages and varies with tolerances signaling includes dialing and other supervisory and power supply. NEC’s term for overscan is “full signals. scan.” Some professional devices, such as standards out of phase When cameras show different colors converters, perform the overscan and crop (re-blank- during a transition because their color bursts are not ing) operations to avoid the visibility of unstable matched. blanking edges, head switch effects, etc. outs See Outtake. overshoot Artifact caused by imperfection of system outside broadcast A TV broadcast that originates from frequency response. Looks like excursions beyond a source other than a TV studio. An outside broad- the steady state either before (pre-shoot) or after cast uses mobile cameras and transmitting or record- (after-shoot, post-shoot) of the signal edge. Usually

203 oxidation

expressed as a percentage of step signal amplitude One unfortunate characteristic of oxidation is its above the steady state level. In the process of aper- rapid acceleration, resulting in the eventual loss of a ture correction pre- and post-shoots may be delib- large part of the video signal. erately added to improve the apparent picture oxide A general term used to describe the accumula- sharpness. tion of magnetic particles that form the coating of oxidation A defect, chiefly associated with videodiscs, videotape. Audio and video signals are electonically that shows up on a screen image as colored drop- printed on the oxide coating. The term “oxide” also outs. Oxidation, sometimes called color flash, has applies to the flaking particles which eventually fall been attributed to various factors, including a chemi- from the tape and clog the video heads, causing cal reaction between the glue that binds the two white specks to flash on the screen during playback. sides of a videodisc and the reflective aluminum layer. This problem is known as dropout.

204 P

P CATV superband channel, 252-258 MHz. paint time In videotex, the number of seconds re- P7 monitor SSTV display using a CRT having a very- quired to display a frame with graphics, measured long-persistence phosphor. from when the frame begins to appear until it is P frames One of the three types of frames used in the completed. coded MPEG signal. They contain only predictive in- pairing A fault occurring in TV picture tubes that em- formation and are therefore much smaller than I ploy interlaced scanning. Lines of alternate fields frames, helping to achieve the low data rates asso- tend to coincide instead of interlacing with each ciated with MPEG. other and the vertical resolution is halved. Pacman Originally a successful arcade video game con- PAL 1. PAL stands for Phase Alternation (or Alter- sisting of a disc-eating creature that travels through nate) Line, Picture Always Lousy, or Perfect At Last, a maze. Atari adapted its coin-operated game for depending on your viewpoint. It is a system of TV its VCS home system in 1982 but with some modi- broadcasting used in the UK and many other coun- fications. Some of the graphics were missing, as was tries in Europe. Developed in Germany, 1961. Not the original sound track. compatible with the North American NTSC system, padding In AVSS files, an additional stream of dummy PAL has a 625-line scan picture delivered at 25 bits interleaved with the others to control the aver- frames/s. Besides providing a better image gener- age byte rate. ally, PAL has improved color transmission over page In videotex, the basic unit of information stor- NTSC. This discrepancy is due to America’s entry age and display, a discrete amount of material that into commercial TV in 1948 while Europe’s PAL sys- can be accommodated at one time within the view- tem, having the advantage of technological ad- ing area of a user terminal—generally 24 lines of 40 vancements, entered TV broadcasting in the 1950s. characters each; also called a frame or screen. Syn.: SECAM, another system used in Europe, is incom- frame. patible with either PAL or NTSC. 2. Programmable Page Burn A proprietary Snell & Wilcox digital video Array Logic. effect combining a pseudo-random wipe shape with PAL 60 This is a NTSC video signal that uses the PAL a pseudo-random color edge. color subcarrier frequency (about 4.43 MHz) and page creation In videotex, the process of assembling PAL-type color modulation. It is a further adapta- the elements of a single page. tion of NTSC 4.43, modifying the color modulation page set In videotex, a group of pages in sequential in addition to changing the color subcarrier fre- order identified by a number. quency. It was developed by JVC in the 1980s for page split A digital video effect where the displayed use with their video disc players, hence the early picture appears as though it is put on the surface of name of “Disk-PAL.” a page that is then split into several rectangular sec- There is a little-used variation, also called PAL 60, tions and made to fly apart. which is a PAL video signal that uses the NTSC color page turn A 2- or 3-D digital video effect where the subcarrier frequency (about 3.58 MHz), and PAL-type displayed picture appears to be put on the surface color modulation. of a page, the corner of which is slowly pulled up PAL-B/G A version of PAL used in Australia and other and back to reveal the other side. If the other side countries. contains a different live picture it is known as a PAL-D TV color system. Used in China. double-sided page turn. PAL flip-flop A bistable circuit that produces H/2-pulses paint In digital TV, a special effect that is similar to an in PAL decoders. oil painting and is also called posterization. PAL-M A version of PAL, used in Brazil. painting An adjustment of the TV camera controls by PAL-N TV color system; Argentina, Paraguay, Uruguay. the appearance of the picture rather than by objec- PAL-NTSC encoder A device to encode two color dif- tive test procedures. ference signals R-Y and B-Y onto one subcarrier.

205 PALplus

Quadrature modulation allows the coding to be in 4:3 TV ratio, while panning the original image to accordance with either the PAL or NTSC system. follow the on-screen action. PALplus A compatible wide-screen version of the ex- paper cut A detailed plan for editing a video tape, isting PAL system, Germany. It was an intermediate keyed to time codes or cues, prepared prior to the step to digital TV. In normal PAL 625-line transmis- actual editing. sions, 576 lines are visible in the picture (the remain- paper edit Preliminary editing of a videotape in which ing lines in the vertical blanking area between notations are made—on paper—but the actual ed- pictures). However, when a letterboxed widescreen iting is not done; also called dry edit. picture is transmitted, there are only 432 lines of parabola A shape that can focus a microwave signal vertical resolution because the picture doesn’t fill the into one narrow beam. All satellite and microwave entire screen vertically. In PALplus, the vertical infor- antennae are parabolic, not spherical. mation normally lost is filtered from the picture be- parabolic antenna A dish antenna at whose focal fore transmission and then transmitted invisibly in point is a permanently attached feed horn. The an- the black area above and below the wide-screen tenna, usually made of aluminum or fiberglass, is image. A separate signal is transmitted during the mounted on a swivel base so that it can be realigned vertical blanking interval to tell the receiver PALplus for each satellite. The antenna receives the micro- is being transmitted. A wide-screen PALplus receiver wave signals from the satellite and changes them to displays the wide-screen picture in full fidelity, occu- electrical impulses. Next, it increases the signals so pying the full screen, while a conventional 4:3 ratio that they can operate a TV set. Finally, it transmits set shows the standard letterbox image with black these modified signals through an RF converter that bands above and below. uses any open channel on the TV receiver. palette In 8-bit displays or images, only 256 colors The technical name for a dish can be displayed at a time. This collection of 256 antenna shaped like a perfect parabola. colors is called the palette. parade A convenient mode for displaying component PAL switch Sync pulse with period of two lines, the video signals on a waveform monitor. The three sig- rising edge of which marks the start of a line with nals (R, G, B or Y, Pr, Pb) are shown multiplexed with positive polarity of V component in PAL chromi- the horizontal deflection rate being one third of line nance signal or the start of a Dr line in Dr/Db se- rate (or field rate). The disadvantage of parade mode quence in SECAM chrominance signal. Syn.: 2H; is that each of R, G, B (Y, Pr, Pb) are from successive 7.8 kHz; Dr/Db switch; PAL switching signal; SECAM lines and thus only one line in three is shown for switch. any single component. pan 1. Pivotal movement of the camera in a horizontal parallax The apparent difference in direction to an plane. Sometimes the term is used generally to de- object seen from two different points, as in a TV scribe movements of the camera in any plane. 2. In camera’s viewfinder and the lens of the camera. The computer graphics, to move (while viewing) to a dif- slight angle of divergence between the two can cre- ferent part of an image. ate framing problems in closeups as well as keystone pan and scan A technique for changing the aspect distortions. ratio of the frame of a wide-screen film so that it parallax barrier system See Parallel Stereogram. can be transmitted for TV. parallax panoramagram A method of displaying a Panasonic See Matsushita. 3D-image. In parallax panoramagram, an aperture panel antenna An antenna with the dipole mounted ratio of the aperture slit is reduced to a value within, in front of a reflector and a dipole/reflector assem- for example, a range from about 1/6 to 1/10 and bly on each face of a tower that can be either 4- or images that have been photographed from many 3-sided. Panel antennas are used for both high- and different directions are sequentially arranged like ver- low-band VHF TV stations. tical stripes onto the stereogram display surface in pan head See Head. units of elements of the images. At this time, a 3D- panic freeze A momentary repeat of one TV frame or image of the directional resolution within a range field from the live video sequence, usually caused from 6 to 10 is obtained. by temporary loss of synchronization. parallax stereogram A technique used in 3-D TV in panning 1. Moving a TV camera across a field of view. which vertical slats are employed to enhance the 3- 2. The movement of displayed graphic data across a D effect. An amount of information recorded in the visual display screen; moving a graphic image inside parallax stereogram is merely equal to the amount a frame to see its various sections. that corresponds to the right and left eyes—in other panning and scanning Panning is the act of moving words, the amount that is twice as much as the in- a camera slowly from one side of a scene toward formation of a plane image. Although no special the other; scanning captures the scene electronically, glasses are required by the viewer, the process is not after panning towards the subject. This technique is compatible with 2-D (conventional TV). used to crop a widescreen picture to conventional parallel attribute A videotex and teletext standard

206 pause/still

whereby an attribute defining the characteristics of patchboard A board or panel that has many jacks at a particular character cell is encoded as part of the which circuits are terminated. Short cables called character code and does not occupy a separate cell. patch cords are plugged into the jacks to connect Cf. serial attribute. various circuits temporarily as required in broadcast, parallel cable A multiconductor cable carrying simul- communication, and computers. taneous transmission of digital data bits. patch box (PB) An accessory unit designed to accept parallel digital A professional digital video interface different video components into its inputs, simplify- using twisted-pair wiring and 25-pin D connectors ing the selection of these sources to be played on to carry the bits of a digital video signal in parallel. the TV receiver. A PB is a relatively inexpensive parallel recording Technology that permits hundreds method of interconnecting antenna, cable, pay TV of hours of video recording to be compressed on and VCR inputs and directing them through TV sets, one videotape; Thomson CSF, Paris. Key to the tech- a VCR, etc. It is not as permanent a connection as nology are components that allow hundreds of tracks that of a switcher, but it is not as costly. Also known to be recorded and played simultaneously. The tech- as a patch panel. nology replaces traditional rotating writing and read- patch cable A wire (usually in pairs) with the proper ing heads with static heads. This allows video connections used to hook up one VCR to another recorder size and cost to be cut to those of a for copying or editing purposes. One cable connects Walkman®. Flat, thin magnetic heads are used to from the video output of the machine to the video record. Multiplexing enables an almost unlimited input of the other, while the second cable plugs into number of TV programs to be recorded concurrently the audio output of one VCR to the input of the as a prerecorded program is played. second machine. VCRs of different formats may re- parental lock A VCR or TV set feature that allows the quire special connections such as RCA phono plugs owner to prohibit one or more channels from ap- or mini-plugs. pearing on screen. A boon for parents who want to patch cord A cord terminated with plugs at each end, prevent their children from seeing certain objection- to connect two jacks on a patchboard. Any cable able programs or channels, the parental lock is some- with a jack at each end used to connect audio or times known as lock down or parental channel video components to each other; in audio, from lockout. which the term originates, the traditional patch cord parity check In digital transmission, a technique for is a cable with a phone plug at each end. detecting that an error has occurred in code groups patching The act of connecting two components to by use of a parity bit. The binary digits in each code each other with a patch cord and/or patch panel. group (including the parity bit) are added to check if patch panel See Patch box. the sum is odd or even. pattern generator A signal generator that produces Pasokon TV Commercial slowscan TV (SSTV) product. on the screen of a TV receiver a regular geometric Interface to send and receive SSTV fits inside expan- pattern that can be used to facilitate the adjustment sion slot of computer. Software supports all popular of linearity and convergence, or to trigger electronic modes, automatic receive mode selection from VIS special effects. code, up to 32K simultaneous colors on screen, and pause A feature on all VCRs that stops the move- graphical user interface with mouse support. Used ment of videotape for a short time during the re- in computer-based SSTV systems. cording process while holding the tape against the passive mixer An accessory used with audio to com- video heads. The Pause mode is used instead of bine and control the level of various signals, with- Stop to produce less picture breakup when the out the addition of electronic circuitry or machine finally returns to Record. Virtually all VCRs components. Since signals entering this mixer are warn against extended use of Pause. As a safety not amplified, they undergo some loss in strength. precaution, machines provide an automatic shut- Passive mixers do not affect the nature or quality of off if the Pause mode is activated for more than 5 the signal other than its level of attenuation or boost. or 6 minutes. Pause circuits differ from one VCR to In addition, they do not need any electrical power. another. Some machines use a high/low sensor passive phase direction autofocus An alternative while others employ a pulse on/pulse off circuit. In focusing system found on some camcorders. The the Pause mode the pressure roller that normally system, which operates through the lens, does not holds the tape firmly against the capstan becomes use any conventional IR transmitter, thereby elimi- disengaged so that the tape stops and remains nating possible focusing problems if an object passes pressed against the video heads. Pause differs from between the lens and the subject being shot. Still or Freeze Frame, a mode that operates by freez- passive satellite See Communications satellite. ing a picture on screen during playback, but not passive switcher See Switcher. during record. patch A temporary connection between jacks or other pause/still A VTR button to temporarily stop the tape terminations on a patchboard. during recording in order to avoid recording un-

207 PAV

wanted material, or to view a paused picture during PDI Picture Description Instruction. playback. PDM Pulse-duration modulation. PAV Public Access Videotex. An interactive electronic peak In video, a signal strength’s highest point. Peaks service for information and transactions at user-con- can be measured with video level or VU meters. trolled terminals in public locations, such as shop- peak brightness Brightness of a small portion of a ping malls and airline terminals. CRT phosphor when excited by a peak white signal. pay-cable Cable TV with one or more pay channels peak brightness level A light output measurement that show new movies and sometimes special pro- used with rear projection TV systems. Peak bright- grams not available on ordinary TV. It is provided for ness, or relative brilliance, is measured in an additional monthly fee beyond the basic cable footlamberts. Many rear projection TVs produce service fee. enough brightness to compete with conventional, pay-per-view (PPV) A cable TV/pay TV service that direct-view TV sets. Peak brightness level differs from allows viewers to pay for special programs of their light output, the latter used in reference to front choice. A special box, called an addressable decoder, projection TV systems and measured in lumens. supplied by a local cable company is attached to the peaking Increasing the response of a circuit at a de- TV set and releases access to paying customers. The sired frequency or band of frequencies. viewer is then billed for the service, along with the peaking circuit A circuit that improves the high-fre- regular monthly cable TV fee. PPV programs are quency response of a signal. In shunt peaking, a small transmitted to cable companies by way of satellite coil is placed in series with the collector load. In se- on scrambled channels. ries peaking, the coil is placed in series with the base A TV system in which special programs of the following stage. It is present in video amps, are provided only to subscribers who make regular often with both types of peaking in the same stage. payments for the service. The programs can be The circuit converts an input signal to a more peaked broadcast in coded or scrambled form requiring a waveform. Also done digitally in video processing decoding or unscrambling device at the receiver. The chips. service can be carried by microwave, as part of a peaking coil A small coil placed in a circuit to reso- cable TV system or by telephone wire. It can be sup- nate with the distributed capacitance of the circuit plied independently or as part of a larger system, in at a frequency for which peak response is desired. A which case the service is called a tier. video amp near the cutoff frequency is an example. Pb Blue color-difference signal, (B-Y). peak level meter A feature found on some VCRs de- PBS Service. signed to indicate the peak volume level of the re- PCM Pulse code modulation. cording and playback. Similar in function to a VU PCS Personal Communications Services. meter, the level meter displays a string of horizontal PC SSTV 5 Commercial slowscan TV (SSTV) product. lights instead of the conventional dial and indicator. Compact separate send and receive interfaces plug peak limiter Syn.: clipper. See Limiter. into a serial port. Software supports the most popu- peak white (US: white peak) 1. A peak excursion of lar modes, reads/writes popular image file formats, the picture signal in the white direction. 2. Potential built-in text-generating capability. Used in computer- at a point in the signal path that the brightest parts based SSTV systems. of the transmitted scene are allowed to attain. Other PC-tuner A device that allows PCs to receive and dis- tonal values lie somewhere between peak white level play signals from broadcasts, cable TV, VCRs or laser and black level, that represent the two extreme val- discs. ues between which the picture signal can vary. At PC-TV Matsushita, Japan. A multimedia model; a com- those points where the DC component is present, puter with a hard drive, a CD-ROM drive and a TV. the peak white level has a fixed value in the same Users can watch TV through an application window way as black level is fixed, but at other points where and download TV graphics to other programs. the DC component is absent the potential corre- PC-TV hybrid, First International Computer Inc. (FIC). sponding to peak white is variable, depending on A PC that has a TV signal converter for watching the mean value of the picture signal. regular TV on the monitor. It also includes an MPEG pedestal 1. An offset to separate the active video from audio/video card that allows users to view laser disks. the blanking level. When a video system uses a ped- PC-TV tuner Front-end unit that allows PCs to receive estal, the black level is above the blanking level by a and display signals from broadcasts, CATV, VCRs or small amount. When a video system doesn’t use a laser discs. pedestal, the black and blanking levels are the same. PDC Program Delivery Control, a system that controls NTSC uses a pedestal (except in Japan), PAL and suitably equipped video recorders using hidden codes SECAM do not. 2. A flat-topped pulse that elevates in the teletext service. If a TV show scheduled to be the base level for another pulse (e.g., in TV sets, videotaped is delayed or re-scheduled, the record- SSC pulse has a pedestal that is the difference be- ing is automatically rescheduled as well. tween black level and blanking level). 3. Black level.

208 phase comparator

The minimum level the blackest portions of the dis- persistence characteristic The relation between lu- played signal are allowed to reach. minance and time after excitation of a luminescent pedestal level Blanking level. screen. It is also called the decay characteristic. pedestal level control (PLC) A function of industrial- persistence of vision The ability of the brain in con- type video cameras that affects the contrast levels junction with the eyes to retain the impression of an as well as the shades of gray of the screen image. image for a short time after the image has disap- The PLC is also designed to balance the images of peared. This characteristic enables the eye to fill in multiple cameras used simultaneously. the dark intervals between successive images in mov- pedestal tripod A professional tripod, often with a ies and TV and give the illusion of motion. hydraulic shaft. persistent phosphor Phosphor in which the image pel Pixel, picture element. persists after excitation and whose decay law is such Pepper’s ghost A procedure in which a camera shoots that a usable or viewable image remains for TV pur- through an angled glass or mirror, so that a reflected poses over the intervals commonly encountered. scene—suggesting the ghost of the subject—can personal communications services (PCS) Wireless be picked up. The technique, developed by John and cellular telephone, videophone, fax, and com- Henry Pepper, a British scientist, is used for various puting services available to private persons with special effects in TV. pocket-size, microprocessor-based radio telephones perceived color See Variables of perceived colors. provided by local telephone companies. Peritel An audiovisual connector standard for Euro- personal video See Portable video. pean TV receivers. Serves the same purpose as AV personal videoconferencing Syn.: desktop connector on some American TV sets. Also SCART videoconferencing. connector. perspective The angle at which we see things; our permanent binary zeros See Time code word. viewpoint. A lens produces its own perspective of permanent magnet (PM) A piece of hardened steel the scene it is viewing, which may or may not agree or other magnetic material that has been strongly with our sense of perspective. magnetized and retains its magnetism indefinitely. persuader An electrode in an image orthicon tube permanent-magnet centering Centering of the im- biased so as to direct the return scanning beam into age on the screen of a TV picture tube by magnetic the electron multiplier that surrounds the electron fields produced by permanent magnets mounted gun. The persuader is in the form of a short cylinder around the neck of the tube. and is given a positive bias (with respect to the elec- permanent-magnet focusing Focusing of the elec- tron-gun-cathode potential) that is adjusted to give tron beam in a TV picture tube by the magnetic field the best uniformity of illumination over the area of produced by one or more permanent magnets the reproduced image: the adjustment is usually la- mounted around the neck of the tube. beled “multiplier focus.” permeability A measure of the ability of any given perveance A factor expressing the ability of a elec- material to act as a path for magnetic lines of force, tron gun to provide an electron stream under the compared with air. It is the ratio of the magnetiza- stimulus of a given accelerating voltage. It is equal tion flux density B to the magnetizing force H. The to the space-charge-limited current divided by the permeability of air is assumed as 1. The video head three-halves power of the accelerating voltage. material must have high permeability so that a sat- PG 1. A pulse generator used in VCR servo circuits to isfactory flux density is induced with a modest mag- create PG pulses that are directly related to the speed netizing force. of the head rotation. 2. Parental Guidance sug- permeability tuner A TV or radio tuner with a tuning gested—some material may not be suitable for chil- dial that moves the powdered iron cores of coils in dren; see Movie rating systems. the tuning circuits. PG-13 Parental Guidance suggested—no one under permeability tuning The tuning of a resonant circuit 13 admitted; see Movie rating systems. by moving a in or out of a coil, thereby phase adjust A term used to describe a method of changing the effective permeability of the core and adjusting the color in a NTSC video signal. The phase the inductance of the circuit. of the color subcarrier is moved, or adjusted, rela- permutation See Encryption. tive to the color burst. This adjustment affects the persistence Syn.: afterglow. In a CRT, the time a phos- hue of the picture. phor dot remains illuminated after being energized. Phase Alternating Line PAL. Popular TV standard used The persistence depends on the nature of the phos- in Europe and Asia. See PAL. phor and for luminescent screens is commonly cho- phase cancellation See Phasing. sen to be less than the persistence of the image on phase comparator A circuit used in a phase-locked the human retina (about 0.1 s). Long-persistent phos- loop (PLL) to tell how well two signals line up with phors reduce flicker, but generate ghostlike images each other. For example, there are two signals, A that linger on screen for a fraction of a second. and B, with signal A connected to the positive (+)

209

input of the phase comparator and signal B con- Philips HDS-NA system See HDS-NA system. nected to the minus (–) input. If both signals are Philips VCR format A 1/2" cassette format (1961) exactly the same, the output of the phase compara- not compatible with either Beta or VHS. The Philips tor is 0; they are perfectly aligned. If signal A is just VCR used a rotating transformer instead of slip rings a little faster than signal B, then the output of the to couple the rotating head signal to the preampli- phase comparator is a 1, showing that A is faster fier. The Philips V-2000 VCR, marketed by than B. If signal A is slower than B, then the output Germany’s Grundig company, had one speed and of the phase comparator is a –1, designating that B could record for 4 hours on each side of its video- is faster. cassette for a total of 8 hours. The cassette size phase correlation Method of motion estimation based was similar to that of the VHS. Although the tape on the measured position of the peaks on a phase was 1/2", two 1/4" tracks were recorded on it. This correlation surface derived using a fast Fourier trans- permitted the cassette to be flipped over for ex- form (FFT), spectrum normalization and inverse fast tended play without lowering tape speed, which fourier transform (IFFT). usually reduces picture quality. Other features in- phase distortion See Distortion. cluded noise-free automatic scanning, freeze frame phase inversion See SECAM chrominance phase and slow motion, an exceptionally fast forward and switching. rewind and programmability for 100 days and 5 phase locked loop (PLL) A circuit that consists essen- different events. tially of a phase detector that compares the fre- phone plug Variety of jack often used as a micro- quency of a voltage-controlled oscillator (VCO) with . that of an incoming carrier signal or reference-fre- phono jack (PJ) A popular-size receptacle on VCRs, quency generator. The output of the phase detec- DVD players, TVs, and other audio and video com- tor, after passing through a low-pass filter, is fed ponents. Known as the RCA phono jack, it accepts back to the VCO to keep it exactly in phase with the the RCA phono plug. On VHS machines PJs are used incoming or reference frequency. Color TV includes for both audio and video inputs and outputs. a PLL, for example, in color decoders and tuners phono plug Variety of jack most often used with au- (AFT). dio amps. Also known as RCA plug. phase noise Refers to the random phase instability of phosphor A material capable of luminescence and a signal. Phase noise is one of several types of deg- therefore used as a coating for the screens of CRTs, radation that affects the NTSC picture quality. Con- such as TV picture tubes. A number of different ma- tinuous research and studies have been made to terials are used depending on the color and the per- correct these influences so that transmission signals sistence required. Phosphor glows when struck by can be improved to match the improved quality TV an electron beam; thus, pictures can be constructed monitors and TV in general. by selectively directing a beam at the phosphor coat- phase quadrature See Quadrature. ing on the back side of the tube’s viewing surface. phase reference switch On a color vectorscope, a Syn.: luminophor. control designed to bring two video signals “in phosphor color In projection TV, the precise color at phase” or together simultaneously at the same point. which the material at the front of the screen glows For example, the switch is activated to test whether when it is struck by the electron scanning beam. the signals from two video cameras are in phase CRT projectors often use phosphors that fall between when using a genlocked system with an external high light output and exact color rendition. Other sync generator. The two vectors produced by the projection TV systems face the same dilemma as a cameras will appear superimposed on the graticule result of trying to produce maximum light output of the vectorscope if they are in phase. If they are while competing with ambient light usually present not, the signals are out of phase and the phase ad- when projection TV is operating. justment of the cameras or the cable lengths should phosphor dot One of the tiny dots of phosphor ma- be checked. terial that are used in groups of three, one for each phasing In general, the adjustment of an oscillating primary color, on the screen of a color TV picture system to establish a desired phase relationship with tube. another system with the same frequency. In color phosphor-dot faceplate The glass faceplate on which TV, the process of ensuring that the time of arrival the trios of color phosphor dots are mounted in a of video or synchronizing signals at a particular point shadow-mask three-gun color TV picture tube. are within the tolerances for the system. In sound phosphor grain Granular structure of the phosphor reproduction, means connecting a (monophonic) of a CRT, visible as a disturbance of the resolution audio signal to the terminals of the individual units of a picture. of a multi-unit loudspeaker or of the reproducers of phosphor saturation State where further excitation a stereo system so that all the diaphragms move in of a phosphor produces no increase of light output. phase. phosphor screen Coating of chemical substances de-

210 picture element

posited on the face of a CRT. When bombarded by on the disc. The fluctuations in the light intensity electrons, the substances emit light. reflected from these pits are focused on the light- photoboard A set of still photographs, made from a sensitive surface of the . film or videotape, or recorded on a TV screen, with photoflood A self-contained light bulb, that gives a accompanying script, usually produced on a 8.5 x very bright, intense light without the use of exter- 11" sheet of paper so that it is a transcript of a com- nal lenses or lamp housings. mercial or a segment of a TV program. photopic luminosity function The response of the Electrode in a camera tube that emits eye with normal level of brightness. photoelectrons when irradiated by light. In a cam- PIC Picture image compression. era tube, an optical image of the scene to be tele- pickup 1. In general, a transducer that converts sig- vised is focused on the face of the photocathode nals in a nonelectrical form of energy into corre- which is transparent so that photoelectrons are lib- sponding electrical signals. Thus, a TV camera tube erated from the opposite face. The liberated photo- was at one time termed a vision pickup tube, but electrons are focused by an electron lens to form a this term is no longer used. 2. See Remote. corresponding charge image on the target of the pickup device See Image sensor. camera tube. pickup pattern A determination of the directions from photocell Light sensitive element. which a microphone is sensitive to sound waves; photoconductive camera tube A camera tube in varies with the mic element and mic design. The which the photosensitive electrode is photoconduc- two most common pickup patterns are omni- and tive. Such tubes are known as vidicons and are used unidirectional. in color TV cameras. pickup response The tendency of a microphone to photoconductive lag In photoconductive tubes, a receive or reject sound coming from different direc- charge remaining at the next scan and subsequent tions; the sensitivity of the mic to various frequen- scans after removal of the light. A measure of lag is cies. See Polar response. the rate of decay of the video signal appearing as pickup tube A camera or TV’s imaging device. See tailing on moving objects, or as an image retention CRT. after the cutoff of the light of an image. If the expo- picture The image on the screen of a TV receiver. A sure to light is short, the lag will be low and will be source image for a simple frame or two interlaced determined primarily by the time-constant of the fields. beam resistance multiplied by photoconductor capaci- picture area The area of a TV screen containing the tance. Furthermore, if the exposure to light is longer, video picture. the lag will be greater because of a combination of picture brightness The brightness of the highlights photoconductive lag and the significant addition of of a TV picture, usually expressed in candelas per trapping effects. Blooming and comet tails are de- square meter. fects related to lag in that they are spurious signals picture carrier A carrier frequency located 1.25 MHz that result from the transducer’s response to changes above the lower frequency limit of a standard NTSC in light level. They are caused by overloading of pho- TV signal. In color TV, this carrier transmits luminance tosensitive surface with extremely bright highlights. information; the chrominance subcarrier, which is photoconductive tube A device that makes use of 3.579545 MHz higher, transmits the color informa- changes in the apparent electrical resistance of a tion. The sound carrier, 5.75 MHz above the picture photoconductor when exposed to light. The first carrier, transmits the sound information. It is also commercial photoconductive tube was the vidicon. called luminance carrier. PAL also uses a similar Variation of the electrical conduc- scheme. See also TV channel assignments. tivity of a material when it is irradiated by electro- picture description instruction (PDI) A form of code magnetic waves within a particular frequency range. used to describe the formation of an image by means Examples of materials that exhibit photoconductiv- of a combination of elements such as dots, lines, ity are selenium, antimony trisulphide and copper polygons, arcs, etc. PDIs are used, for example, in oxide, all of which have been used in the targets of alphageometric videotex coding standards. vidicon camera tubes. picture detail The total number of lines or elements photodiode A semiconductor diode in which the re- that make up a picture on the screen of a TV verse current varies with illumination. In a laser-op- receiver. tical video disc player, the component that conducts picture element (US: dot); pel, pixel. The smallest sub- electricity proportional to the amount of light that division of a TV image. In a color TV set it is one strikes its surface. The signal formed by this process color phosphor dot. In a black-and-white TV set it is carries two audio tracks as well as the video mate- a square segment of a scanning line whose dimen- rial. LaserVision players do not use a stylus that physi- sion is equal to the nominal line width. Resolution cally touches the videodisc. Instead, a beam of light (crispness and clarity of images) improves as the “reads” the information encoded as microscopic pits number of pixels displayed increases.

211 picture equalization picture equalization A camcorder feature allowing out with an offering called Picturephone Meeting manual adjustment of color, tint and sharpness Service that provided full video teleconferencing. It during shooting. was available through rented rooms or through picture flutter Irregular bouncing or flapping of the equipment sold or rented to corporations. It also picture on a TV screen. See Flutter. didn’t do well since the service was expensive and picture frequency (frame frequency) In TV, the num- no one wanted to spend the time traveling to the ber of times the whole picture is scanned in a sec- conferencing rooms. In 1992 AT&T introduced a ond. In the British TV system the picture frequency product called Videophone 2500, that transmitted is 25 Hz and in the USA the frame frequency is moving (albeit slowly-moving) color pictures over 30 Hz. normal analog phone lines. picture if (PIF) See VIF. Picturephone Meeting Service (PMS) An AT&T ser- picture indexing See Electronic program indexing, vice once provided under experimental tariff. It com- Index search. bined TV techniques with voice transmission. PMS picture-in-picture (PIP, P.I.P., PinP) A TV receiver fea- was usually only available between telephone com- ture that sequentially scans several channels and dis- pany-located Picturephone centers. plays their programs in the form of insert pictures in picture search/lock A VCR feature that permits the the main screen image. This permits the viewer to user to view the contents of a videotape in forward survey the contents of other programs while simul- or backward mode at up to about seven times the taneously watching a main program. PIP, which de- normal speed in Standard Play mode or about 21 pends on digital circuitry for its special effects, allows times normal speed in Extended Play. See Search the main picture to be swapped for the insert. In mode. addition, stereo sound can be exchanged between picture signal (US: noncomposite signal) In TV, the the two pictures. Some TV monitor/receivers can signal that results from the scanning process and display up to nine images at a time, freeze the PIP which, when combined with the synchronizing sig- image, store the main image for later recall or view nal, forms the video signal; the portion of the video a strobe effect of nine images simultaneously. The signal above the pedestal. first viable use of PIP appeared in 1979 with Sharp’s picture-signal amplitude The difference between the DualVision TV set that was capable of producing a white peak and the blanking level of a video signal. 4" black and white picture within a 17" color picture-signal polarity The polarity of the signal volt- image. age that represents a dark area of a scene with re- picture-in-shuttle In professional video recorders, spect to the signal voltage representing a light area. mode for rapid search of picture content for the lo- It is expressed as black negative or black positive. cation of a particular frame at 20 or 30 times its picture size The useful viewing area on the screen of normal forward speed. a TV receiver, in square inches. picture line-amplifier output The junction between picture synchronizing pulse Vertical synchronizing the TV studio facility and the line feeding a relay pulse. transmitter, a visual transmitter, or a network. picture/sync ratio In video, the ratio of the maximum picture line standard The number of horizontal lines picture signal amplitude to the amplitude of the syn- in a complete TV image. The NTSC standard is 525 chronizing signals, i.e. (white level-blanking level): lines, for PAL 625 lines. HDTV uses 720 and 1135 (blanking level-sync level). The ratio must be chosen lines. with care. If it is too large, the sync signals will be picture locking Synchronizing the picture signal; the too small to hold pictures steady at the receiver, and sync controls on a picture. if it is too small the pictures may be too noisy to picture monitor A CRT and associated circuits, ar- view, even though synchronization may be perfect. ranged to view a TV picture or its signal characteris- picture transmission The transmission, over wires or tics at station facilities. by radio, of a picture that has a gradation of shade Picturephone® AT&T’s trademark for a video tele- values. phone that permitted the user to see as well as talk picture transmitter Visual transmitter. with the person at the distant end. AT&T introduced picture tube A CRT used to display pictures in a TV it at the 1964 World’s Fair in Flushing Meadow, receiver or monitor. Usually has electrostatic focus- Queens, NYC. The device had a camera mounted ing and is designed for wide angle magnetic deflec- on the top and a 5.25" x 4.75" screen. Audio sig- tion to give a short tube suitable for mounting in a nals were transmitted separately from video signals cabinet. Tubes for displaying black and white pic- and the system could not use the public switched tures have a single electron gun and a screen made telephone network. It needed a transmission band- of a continuous layer of phosphor giving an approxi- width of 6.3 Mbps and no one wanted to pay the mation to white light. For displaying color TV pic- price for the service, so it never got off the ground. tures three guns are necessary (or a single gun firing AT&T picked up on the name Picturephone and came three beams) and the screen is made up of dots or

212 pirate box

strips of phosphors giving red, green and blue light. voltage at the horizontal sweep rate to make the Also called a TV picture tube. picture straight at the top and bottom of the screen. picture tube booster A device that provides an over- pincushion distortion Distortion of a picture tube in voltage to reactivate the ineffective electron emitter which the sides of a reproduced square bulge in- of a TV picture tube. There are two types of boost- wards. When a video screen is distorted—with the ers. One is for parallel (transformer-type) tube hook- top, bottom and sides pushing in—the screen is said ups and the other is for series tube hookups to be suffering pincushion distortion. Usually caused (transformerless). by nonuniformity of the field produced by the scan- picture-tube brightener A small step-up transformer ning coils. It is the opposite of barrel distortion. that can be connected between the socket and base p-i-n diode A diode having a thin layer of intrinsic of a picture tube to increase the heater voltage. It (undoped) silicon between the p and n regions. With increases picture brightness to compensate for nor- no bias applied, the intrinsic (i) region is empty of mal aging of the tube. free charges. In the forward-biased condition, elec- PictureTel One of the two largest manufacturers of trons from the n region flow into the i region and videoconferencing equipment (both desktop systems lower its AC resistance. The greater the DC current, and room-based systems) in the world. the lower the AC resistance is. This particular phe- PID Packet identifier for transport packets in MPEG-2 nomenon finds application in RF modulators circuits. Transport Streams. PinP Picture-in-picture. piezoelectric The property of a material to generate a PIP Also P.I.P. and Picture-in-picture. voltage when mechanical force is applied, or to pro- PIP accessory A video unit that takes advantage of duce a mechanical force when a voltage is applied, digital technology by providing insert pictures so that as in piezoelectric crystal. the viewer can watch two live broadcasts at the same piezoelectric crystal A crystal that has piezoelectric time. VCRs, VDPs or video cameras can be connected properties. Crystal loudspeakers and crystal micro- to provide the second source image. The accessory, phones are made from this material. which may come equipped with one or two built-in piezoelectric microphone A microphone containing tuners, produces pictures instantaneously. In addi- a ceramic or crystal element that produces a signal tion, the insert can be changed in size and posi- voltage whenever the movement of the diaphragm tioned anywhere on the screen. Other features puts stress on the element. These inexpensive mics, include freezing the action of the insert, exchang- also known as ceramic or crystal mics, have a lim- ing the main picture with the insert and monitoring ited frequency range and are easily affected by another location through the use of a video changes in temperature. camera. pif Picture IF. See VIF. piped program A radio or TV program sent over com- A frame that the image does not completely mercial transmission lines. fill horizontally (i.e., a 4:3 image on a 16:9 screen), pipeline architecture A special hardware process, in the same way that a letterbox describes a frame used with some character generators, designed to that the image does not fill vertically. regenerate an entire video display for each video pilot See Stereo pilot. field. This technique adds flexibility when animat- pilot light Refers to a special light that indicates ing characters in real time. Pipeline architecture dif- whether a unit or one of its parts is functioning. The fers from the conventional frame-buffer method pilot light usually maintains a particular position or used with many character generators. color to differentiate it from other similar lights. Some pipelined operations A mode of operation for dis- VCRs, for example, may have a yellow light to sig- plays when a stream of data such as pixels passes nify that the machine is in Record mode, an amber through a set of processing circuits. light for the Pause mode and a green light that des- PIP source mode A feature, appearing only on some ignates that the power is on. TV sets, that allows the viewer to select the source, pilot tone A videotape technique to monitor and such as another TV channel or a VCR, for a PIP. The correct color. PIP source mode usually is displayed as one of the pinch roller A part of a VCR designed, along with the features of a special screen menu and is activated capstan, to help control the tape as it moves along from a remote control. its path. Usually composed of rubber, it presses the piracy The unauthorized use of copyrighted material. videotape to the capstan. There are two types of piracy in the electronic com- pincushion corrector A TV circuit that compensates munications world, signal theft and replication. The for pincushion distortion. The horizontal pincush- largest unauthorized use occurs in three areas: cable ion corrector uses the vertical sawtooth voltage to systems, satellite-delivered program networks (sig- vary the load on the horizontal sweep system at the nal theft), and home video (replication). vertical rate and thereby straighten the sides of the pirate box A picturesque term for an illegal decoding picture. The vertical corrector circuit uses a parabolic device that allows unauthorized viewers to watch

213 PI sequence

otherwise scrambled satellite transmissions of cable animation. The Record mode is pressed to record a services. These “black boxes,” chiefly interest the subject, then stopped. The subject is moved slightly more than 2 million owners of satellite TV systems. while the camera is in off position. The Record-Stop Title 47, Section 605, of the U.S. Code, warns that cycle is then repeated to create the animated effect. the penalty for unauthorized interception of satel- plaintext A message that is not encrypted. lite signals is two years in prison and a $50,000 fine. Plan 9 Experimental operating system treating all re- Various agencies, including the F.B.I. and the Mo- sources as files (named after a 1950s science fiction tion Picture Association of America, have vowed to B movie); AT&T Bell Laboratories in Murray Hill, N.J. go after and prosecute the manufacturers and dis- The operating system needs no technical sophisti- tributors of these decoders. cation to handle graphics, since the images are pro- PI sequence See SECAM chrominance phase duced at the application software level. However, switching. to manage video, the operating system must com- pit In optical recording, a microscopic depression made prehend realtime, where a data stream represent- on the disc surface by the recording laser beam. Re- ing many frames of video must move to the display corded information is contained in the pits and the in a prescribed period of time. spaces between pits—lands. plano-concave A lens configuration in which the ele- pitch black Extremely dark, as pitch (tar). ment has an inward curve on one side and a flat pix 1. Picture. 2. Show-business jargon for motion pic- surface on the other. tures or pictures in general. plano-convex A lens configuration in which the ele- pixel Picture element or picture cell. The smallest re- ment has an outward curve on one side and a flat solvable and addressable segment (in terms of X and surface on the other. Y coordinates) on a video display screen. It can be plant The physical components of a cable-TV system. the pattern made by the RGB electron guns on a The term is applied specifically to the headend equip- color TV or computer screen, or the smallest elec- ment but it is sometimes used to refer to all techni- trode on a LCD panel. The number of pixels helps to cal aspects of the operation, including trunk lines, determine the sharpness of the picture. In HDTV, feeder cables, drop lines, amps, and all other elec- with its 1080 horizontal scanning lines, the pixel tronic gear. The equivalent of a plant in the TV broad- number is said to be five times greater than that of casting industries is facilities. the NTSC, 525-line system, resulting in a sharper plant native format The highest video resolution of picture than that of 35-mm movie film. which a particular physical plant is capable. pixel array A collection of pixels that cumulatively plasma An ionized gas containing an approximately represent the color and form of an image. equal number of positive and negative charges. The pixel clock A generator to divide the incoming hori- gas emits light when subjected to a sufficiently high zontal line of video into pixels. This pixel clock has voltage. to be stable (a very small amount of jitter) relative to plasma panel The part of a video display tube or other the incoming video or the picture will not be stored display device that consists of a grid of electrodes in correctly. The higher the frequency of the pixel clock, a flat, gas-filled area (a panel) in which the energiz- the more pixels that will appear across the screen. ing of the electrodes causes the gas to be ionized pixel drop out In some instances, a pixel drop out (the ionized gaseous discharge is called plasma) and looks like black spots on the screen, either station- light to be emitted; also called gas panel or gas tube. ary or moving around. Several things can cause pixel plasma technology A technology that is the most drop out, such as the a-to-d converter not digitizing promising for flat, wall-mounted TV applications the video correctly. Also, the timing between the because it combines wide viewing angle, fast re- ADC and the frame buffer might not be correct, sponse and ease of fabrication. causing the wrong number to be stored in the buffer. Plasmavision TV Full-color flat-panel gas-plasma TV; For that matter, the timing anywhere in the video Fujitsu. The screen is slender enough for mounting stream might cause a pixel drop out. on a wall. The flat-panel technology became avail- pixellation In a digital image, a subjective impairment able in Japan in 1994. In this technology, a gas held where the pixels are large enough to become indi- in tiny cells is excited by an electrical charge. The vidually visible. excited gas—or plasma—causes phosphor dots on pixel operation The process of modifying a pixel value the viewing screen to glow. for some specific purpose. plastic effect In TV, an effect of relief in reproduced pixel pitch A central distance between the pixels on images caused by exaggeration of the tonal transi- the image display surface. tions. The effect can be caused by a poor low-fre- pixel value A number or series of numbers that repre- quency response in the video amplifier. It can also sent the color and luminance of a single pixel. See be caused in images reproduced from an image or- also Color value. thicon tube because this type of tube tends to pro- pixilation A rudimentary method of creating video vide black borders around image highlights.

214 polarity play A control button on all VCRs and DVD players plugumentary Informal. A film or TV program that that brings the information on the videotape or DVD purports to be disinterested factual documentary but to the TV screen in the form of a picture. contains publicity material. A blend of plug and playback 1. Reproduction of a recording. A function documentary. that permits a VCR or DVD player to convert the plumbicon A high-quality, low-velocity TV camera tube recorded information into a signal for display on a used in professional broadcasting video cameras. The TV screen. 2. A multimedia term. Playback is the plumbicon tube was partially responsible for the de- process of viewing multimedia materials created by velopment of color TV broadcasting in 1964. The an author. Playback can include a range of activi- tube is alleged to feature greater sensitivity, higher ties, from viewing a single video clip to participating resolution and less lag characteristics than the saticon in a series of interactive multimedia training mod- camera tube. ules. Some playback applications (e.g., many train- plus diopter A special lens accessory that fits over a ing and presentation applications) are sold separately camera lens to make that lens capable of extreme from their authoring applications. However, many close-ups. developers are selling authoring and playback ca- PLV 1. Presentation-level video. 2. Production level pabilities in a single product. 3. See Foldback. video, DVI Technology’s highest quality motion video playback amplifier In video, a circuit that increases compression algorithm. It is about 120-1 compres- the video signal before it is supplied to a TV receiver. sion. Compression is done “off-line,”—i.e., non-real In audio, a circuit that amplifies the audio signal prior time—and playback (decompression) is real time. to its being reproduced through a speaker. Independent of the technology in use, off-line com- playback head Syn.: read head. The part that con- pression will produce a better image quality than verts the magnetic information on the tape or disc real time since more time and processing power is into an electrical signal. Moving the magnetic fields used per frame. on the medium (tape or disc) past the playback head PM 1. Permanent magnet. 2. Phase modulation. generates a tiny voltage, which is picked up in a PMS Picturephone Meeting Service. conductor (a coil) in the playback head and sent onto Pockel’s effect See Kerr effect. the electronic equipment where it is amplified or point gamma In TV, the slope of the curve relating transmitted. the logarithm of the output of a device, equipment play speed indicator A feature on many VCRs that or system to the logarithm of the input. The input tells the tape speed mode when the machine is in or output may be light or an electrical signal and Play. Most VCRs simply play back a cassette auto- thus there can be a point gamma for a camera tube matically in the speed in which it is recorded, re- or the overall system. gardless of the selector button. The indicator point of purchase See POP. presents no problem in Record or Stop mode, since point-to-multipoint A circuit by which a single signal the machine will operate in the function that it is goes from one origination point to many destina- set for. But since the VCR speed is activated auto- tion points. The classic example is a TV signal being matically by electronics when it is in Playback, it is broadcast from one satellite to many CATV subscrib- difficult to determine the mode without the play ers all around the country. Not to be confused with speed indicator. a multi-drop circuit. PLL Phase locked loop. point-to-point A private circuit, conversation or tele- pluge pulse A signal, found on some color bars, that conference in which there is one person at each end, helps in adjusting TV black level. The best luminance usually connected by some dedicated transmission occurs when the brightness control is turned so that line. the pluge pulse is barely visible. point-to-point communication Radio communica- plug 1. The male connector or counterpart to the jack. tion between two fixed stations. The audio and video inputs and outputs on compo- point-to-point connection An uninterrupted connec- nents are also called audio and video jacks into which tion between one piece of equipment and another. compatible plugs are connected. However, plugs are point-to-point topology A where often referred to as jacks and vice versa. The plug, one node connects directly to another node. such as the RCA phono plug, is usually the end part polacoat A special material used in making rear pro- of a cable or wire. 2. The process of promoting a jection screens for film-to-videotape transfers. A product or service on a TV program. Guests on a sheet of polacoat is usually stapled to a homemade talk show often discuss their recent books or new wooden frame and a projected image is cast on the movies in a seemingly casual way and thus “plug” rear of the screen. A video camera captures the the product. This form of advertising differs from a bright image from the front. Polacoat is preferred commercial in that the personalities or the compa- over front projection beaded screening that diffuses nies they represent are not charged a fee by the sta- the light instead of concentrating it. tion, network, or cable system. polarity 1. The positive or negative orientation of a

215 polarity of picture signal

signal; in video, the polarity of the picture is black/ polymorphic tweening A dramatic effect used by negative, white/positive; reversed polarity would professional videographers that changes the shape result in a negative picture. 2. The form in which of a screen object into another shape by controlling light waves vibrate. motion, timing and perspective. This special effect polarity of picture signal The polarity of the black is accomplished by blending image processing and portion of a picture signal with respect to the white animation with the help of a computer-generated portion. In a black-negative picture, the potential program. corresponding to the black areas of the picture is polysilicon Colloq. Polycrystalline silicon. Silicon in negative with respect to the potential correspond- polycrystalline form is most often used to form the ing to the white areas of the picture. In a black- gate electrodes in silicon-gate MOS ICs and CCDs. positive picture the potential corresponding to the In this application the silicon is doped with a suffi- black areas of the picture is positive. ciently high doping concentration so that it becomes polarization A characteristic of the electromagnetic degenerate and exhibits metallic properties. radiation (e.g., lightwave, radio, or microwave) polyvinyl chloride (PVC) Durable polymer that has great where the electric-field vector of the wave energy is physical strength and is capable of withstanding a perpendicular to the main direction, or vector, of great deal of abuse before serious damage or defor- the electromagnetic beam. The direction of the elec- mation results. Often used as the base material of tric field, as radiated from a transmitting antenna. magnetic tapes for audio and video recording. Horizontal polarization is standard for TV in the US, Pong The first successful electronic video game. In- and vertical polarization is standard in the UK. Four vented by Nolan Bushnell and introduced by Atari senses of polarization are used in satellite transmis- in 1972, Pong now seems primitive when contrasted sion: horizontal, vertical, right-hand circular, and left- with today’s sophisticated visual and audio effects. hand circular. See also Posterization. Although it was a simple black-and-white polarization rot(at)or A device that permits selec- nonprogrammable game, its success led to other tion of one or two orthogonal polarizations, or of companies invading the video game field with simi- any polarization angle. Not a polarizer. lar products. polarizer (also depolarizer) 1. A bi-refrigent compo- POP 1. Initials that stand for “point of purchase” pro- nent in a waveguide or antenna system, that con- motional materials in a retail setting. In home video verts between linear (plane) and circular stores, the materials consist of free-standing card- polarizations. Not a polarization rotor. 2. A Nicol board floor displays, sell sheets and brochures, tent prism or other device for polarizing light. cards, banners, mobiles, and posters touting new polarizing filter A special filter with polarizing prop- title releases, or counter standups that promote a erties; a filter which, when placed over the lens, can star. The POP materials are created by the program be rotated so that it cuts down the amount of re- suppliers and are distributed by them and their flected light coming into the lens. wholesalers to encourage impulse sales on the pre- polar mount In satellite TV systems, the base of an mises of a video store. 2. Picture-out-of-picture. antenna designed to be aligned on true north. The pop filter A sponge-rubber or plastic foam cap placed polar mount permits steering in hour angle (i.e., over the end of a microphone to reduce sibilance, along the geo arc) by remote to the appropriate breathy sounds, popping p’s and b’s, and other un- angle by rotation about a single axis so that it can wanted vocal effects. receive signals from any satellite. A classical polar porch The brief interval that occurs between the com- mount has its axis parallel to that of the earth. TVROs mencement of line blanking and the leading edge use modified polar mount geometry, incorporating of line sync and the somewhat longer interval sepa- a declination offset. Also called equatorial mount. rating the trailing edge of line sync and the end of Polaroid Trademark of Polaroid Corp. for a plastic sheet line blanking. These two very important features of material that produces plane-polarized light. a video signal waveform are correctly described as Polarotor A proprietory name for a type of polariza- the pre-sync line blanking period and the post-sync tion rotor, a transition with a remotely rotatable line blanking period, respectively. More succinctly, prode. they are commonly known as the front porch and polar response The pattern that illustrates the direc- the back porch. The purpose of the front porch is to tion from which sound waves reach a microphone. allow a sufficient interval of time at the end of each Polar response patterns are usually circular. For in- line scan prior to the commencement of line sync, stance, an omnidirectional microphone responds to during which the signal is free to return to black sound from all directions. Also known as microphone level from whatever tonal value corresponds with pickup response, pickup response, and polar re- the extreme end of the line; this latter may of course sponse pattern. be any level in the range from black to peak white. polymethyl methacrylate substrate A support layer The back porch is simply what is left of line blanking of plastic material used to make optical video discs. after the front porch and the line sync pulse have

216 power belt

been accounted for. However, it also serves as a con- positive interlace An interlace method where the po- venient part of the waveform for certain ancillary sition of each line is the same in every frame of video. functions, notably dc restoration and, in the case of Line 1 is in the exact same position in every frame, certain systems of color TV, it serves to contain a as are line 2, line 3, and so on. In positive interlace reference burst of color subcarrier. scanning, each line will always be exactly centered portable VCR A small and light version of a table-top between the lines that precede and follow it. All or home model VCR. The portable can be taken into professional broadcast equipment uses positive in- the field and operates on batteries as well as with terlace scanning. You might wonder if you can see AC power. First introduced in 1978 (a VHS model the difference between random and positive inter- by JVC and a Beta by Sony), the portable, designed lace. If you were to put the two systems next to for the consumer, climbed in popularity in the early each other on home TV systems, you probably 1980s. wouldn’t see any difference. The difference is im- portable video A hand-held portable TV or VCR unit. portant when you begin building a system and hook- The flat screen LCD measures about 3" diagonally. ing various components together and trying to use Portable video is sometimes described as personal sophisticated production techniques. video. positive modulation (US: upward modulation) Also Portapack The early versions of portable cameras and called positive transmission. In TV transmission, am- videotape recording equipment, manufactured by plitude modulation in which increased picture bright- Sony in 1970. The gear consisted of a small camera ness results in increased carrier amplitude. This is and a battery power pack that was worn around the system used in the original British 405-line TV the waist, along with a half-inch reel-to-reel record- system. ing unit that was often carried in a backpack. The positive/negative switch See Image reversal. gear was heavy and cumbersome, however, and was positive transmission Positive modulation. eventually replaced by the smaller camcorder units, positive trapping system A technique employed by but many people continue to call the modern por- some CATV operators to prevent nonsubscribers table assemblages by their original name. from receiving a pay TV service. A signal is transmit- portholing An effect created by using lenses at full ted in the center of a pay TV channel such as wide angle or keeping the iris open to its maximum. Showtime, causing picture break-up and sound in- Either of these conditions may cause the video im- stability for unauthorized receivers. The interfering age to “roll off” at the corners, resulting in a dis- signal is eliminated for subscribers by the use of a torted background. Portholing, especially critical special “trap.” when doing chromakeying, can be avoided by check- postdeflection focus tube Lawrence tube. ing the video signal in a waveform monitor. posterization 1. See Paint. 2. A VCR feature that per- portrait mode In camcorders, a mode to get Portrait mits changing the gradation of images during the effect (the subject is in focus and the background is editing process. Posterization, sometimes known as out of focus). Shooting situations: a still subject such polarization, often provides several gradations as it as a person or a flower; zooming in on a subject in exaggerates colors for a cosmic sunspot effect. This the telephoto mode; a subject behind an obstacle feature appears only with digital VCRs. Professional such as a net. editing consoles also offer this capability among their ports Air ducts built into microphones to control the many special effects. pickup pattern and frequency response characteristics. posted See Postproduction. position A place in relation to other objects or indi- posting See Postproduction. viduals. It is a part in relation to the configuration of postproduction In video (and audio), the process of the whole. The position of the image formed by a merging original video and audio from tape or film lens from an object is fixed in relation to the lens into a finished program. Postproduction includes ed- and object. iting, special effects, dubbing, titling, and many other position identification A professional tape-editing video and audio techniques. During the procedure that first uses a cue tone, then a time postproduction process, personnel are said to be code. Considered an early version of virtual editing, posting and after the job is completed, the program position identification editing made edit reviewing is said to have been posted. possible for the first time. poststripe The process of adding time code to a mas- positive booster See Booster. ter videotape after footage has been recorded. This positive ghost A ghost signal displayed on a TV screen is generally done by dubbing the time code onto a and containing the same tonal variations as those free audio channel. of the original image. pot Audio term for a volume control knob. positive image A picture as normally seen on a TV power adapter See AC adapter. picture tube; it has the same rendition of light and power belt A portable power source for a video re- shade as in the original scene being televised. corder. Worn around the waist like a belt, the acces-

217 power fluctuation

sory is usually made of leather, contains nickel-cad- difference can be represented by a smaller number mium cell pockets and includes a built-in overnight of bits per word, say four instead of eight. This tech- charger. The power belt is basically used in indus- nique is called differential pulse code modulation trial/educational applications with broadcast-type (DPCM). A DPCM system is overloaded when there cameras. is an occasional large difference between adjacent power fluctuation A condition in video caused by a pixels, as at a very sharp edge. This is called slope VCR or TV set connected to the same AC line as a overload and results in a smeared edge. DPCM also major appliance such as a refrigerator or air condi- has the problem that the amplitude of each pixel tioner. Power fluctuation can cause vertical distor- signal is the sum of the amplitude of the adjacent tion on the top third of a TV picture. pixel signal and the difference. If an error creeps into power/intensity A control usually found on the front one of the pixels, it will be repeated until the level is panel of a vectorscope. This knob functions both as reset. As the result of these problems, DPCM is not on/off switch and as a brightness control for the widely used by itself, but it is a useful technique vectors that are displayed on the CRT screen. when combined with others. power-off eject See Auto operation. predistortion Preemphasis. power saver A video camera feature that automati- pre-echo effect Print-through. cally shuts off the power of the camera after a cer- preemphasis The first part of a process for increasing tain time to preserve battery life. the strength of some frequency components with power zoom An electronic trigger-type control that respect to others, to help these components over- permits the video camera lens to be moved in and ride noise or reduce distortion. It emphasizes the out, thereby increasing or decreasing the screen higher audio/video frequencies in frequency- and image size of the subject. It is the most sophisti- phase-modulated transmitters and in sound/video cated of zoom controls, the others being the me- recording systems. It is also called accentuation, em- chanical zoom ring and the zoom ring lever. phasis, predistortion, and preequalization. The origi- power zoom ratio A camcorder’s parameter that in- nal relations are restored by the complementary dicates the difference between the widest wide- process of deemphasis before reproduction of the angle setting of a lens and the tightest telephoto sounds/images. shot. preemphasis network A filter inserted in a system to PP CATV hyperband channel, 390-396 MHz. See TV emphasize one range of frequencies with respect to channel assignments. another. It is also called an emphasizer. PPI Pixels per inch. preequalization Preemphasis. PPV 1. Peak-to-peak voltage. 2. Pay-per-view. premium channel A TV channel for which viewers Pr Red color-difference signal, (R-Y). pay an extra charge, such as Home Box Office (HBO). pre-amp Amplifier fed from a source of very low out- preproduction The preparations required before the put such as a photocell, capacitor microphone or actual shooting begins. This may include script writ- video camera, that boosts a signal before further ing, rehearsing, lighting, etc. transmission in order to reduce capacity and other preroll 1. A VCR feature, found chiefly on S-VHS decks, losses with consequent impairment of the signal- that runs the playback video for a few seconds—to to-noise ratio. For this reason, pre-amps are mounted attain the appropriate head and tape velocity and very close to the signal source, and often in the same sync—before entering the recording mode. The pur- enclosure. pose of this procedure is to provide greater accu- precision-guided munitions Bombs that employ TV, racy in recording and editing while reducing picture laser, or electrooptical guidance with or without mi- breakup. 2. The wobbly warmup period from when crowave remote control links between the bomb and a video camera starts until it is stabilized in the roll its launching aircraft. It is also called a smart bomb. mode. precision-in-line picture tube A shadow-mask pic- prescaler Frequency divider. Used in TV tuners, where ture tube in which three electron guns (or three the normal VHF and UHF oscillator frequencies for beams from a single gun) are arranged in a horizon- each channel are much too high to be used as a tal plane and the screen consists of vertical stripes comparison in the PLL integrated circuit. The of red, green and blue phosphors. The mask has prescaler drives the oscillator signal down. vertical slits, one for each group of three phosphor presence In reproduced sound the illusion of close- strips, so arranged that each strip is masked from ness to the performer or instrument. Presence can two of the beams. The convergence for such tubes be improved by applying a lift to frequencies in the is considerably simpler than for delta-array picture range 3 to 5 kHz and this is commonly done in hi-fi tubes. reproduction. prediction In digital TV, the technique based on the presentation entity The active element of a termi- fact that the difference in signal levels between ad- nal that is concerned with presentation. It inter- jacent pixels is usually small. If this is the case, the acts directly only with elements in the next higher

218 product cipher

division and the next lower division within a host to produce any desired set of intermediate colors, or terminal. within a limitation called the “gamut.” The primary presentation level protocol A set of rules, or proto- colors for color television are red, green, and blue. col, for the encoding of videotext and teletext. primary-color unit The area within a color cell in a presentation-level video (PLV) In DVI technology, the color picture tube that is occupied by one primary highest-quality video compression process, PLV re- color. quires the use of a large computer for compression. prime focus The focal point of a paraboloid reflector. presentation protocol control information (PPCI) In A feed system placed at that point. videotex, a header for a presentation protocol data prime time The hours between 7 and 11 P.M., when unit (PPDU) that serves to delimit the PPDU from the largest TV audience is available. preceding and following PPDUs. print-through The superimposing of the audio and presentation protocol data unit (PPDU) A unit of video signals of one part of the tape onto another. data consisting of presentation protocol information This problem may arise if the tape is very tightly (PPCI) followed by a presentation service data unit wound and stored for long periods of time. This (PSDU). causes one layer to “print through” part of its sig- presentation service data unit (PSDU) The portion nals onto adjacent layers of tape. However, this ap- of a PPDU that contains either management com- pears to be a minimal problem with videotape. Also mands or a particular data syntax as indicated in its known as pre-echo effect. PPCI. proc amp A processing amplifier that permits indi- pressure roller A flat, horizontal metal arm with a vidual control of certain aspects of a video signal, small vertical rubber cylinder at the end to hold the such as color hue and saturation as well as fading videotape firmly against the capstan that controls to and from black. Sometimes mistaken for a color the speed of the videotape. The pressure roller is processor, the proc amp increases the number of disengaged when the VCR is in Pause mode, caus- corrections and special effects of the processor. A ing the tape to remain stationary but in contact with proc amp can be used between VCRs to correct color the video heads. or prevent color-fringing during black and white dub- Short for Press and tell. Videotex system, Great bing. Professional proc amp units stabilize the pic- Britain. Prestel was the world’s first operational video- ture by eliminating the old synchronizing pulses and tex service, and it was launched in 1980 after ex- creating new ones. Sync pulses control the precise tensive trials. timing of video signals inside a VCR or video cam- preview 1. To view a vision signal on a monitor before era. Some proc amps employ a joy stick to control selecting it for transmission or similar application. overall color. Most models incorporate a distribu- 2. The monitoring of a video signal prior to its being tion amp as part of the unit. processed through a special effects generator. 3. In processing amplifier Proc amp, proc amplifier, signal digital TVs, a mode that displays the still picture of processor, video processor, helical scan processor. A nine channels in sequence, arranged in three rows unit inserted on the line between any two compo- and three columns on the screen. At predetermined nents through which a composite video signal trav- times, the display is changed so that all channels els; serves to stabilize the composite signal, programmed into the tuning-system memory are regenerate the control pulses, and in certain mod- scanned. els, change the gain and pedestal to improve preview monitor (PV) A TV screen used by the direc- contrast. tor to monitor and select a picture to be used from processor loop An electronic connection on various among shots by various cameras and other sources. units designed to link up other units such as a color previsualization A relatively recent technique used in corrector or special effects generator. A processor filmmaking to transfer and assemble still images of loop (sometime referred to as “loop through”) can scenes and artists’ conceptions onto videotape ac- accommodate several video signals, including ter- companied by the appropriate sound effects and dia- minals for audio, composite video and S-Video sig- logue. Previsualization gives the director a better nals. In addition, the connection can increase the opportunity to perceive an early version of this film. number of components attached to an audio/video prevue Preview. switcher. primaries The colors of constant chromaticity and vari- procr Processor. able amount that, when mixed in proper propor- Prodigy A subscription videotex service launched in tions, produce or specify other colors. 1988 by IBM and Sears, that operates via PCs. Served primary color A color that cannot be matched by any as a bridge from videotex to the new media projects combination of other primary colors. In color TV, the of the 1990s. Prodigy evolved from an unsuccessful three primary colors emitted by the phosphors in videotex program called Trintex, which started in the color picture tube are red, green, and blue. 1984. Now a major internet service provider. primary colors A set of colors that can be combined product cipher See Encryption.

219 production production In video, refers to the process of creating one event on different days and on various chan- programs. In more specific usage, production is the nels. The timer consists of a digital clock, control process of getting original video onto tape or film, panel, indicator lights and a microprocessor capable ready for postproduction. of programming the VCR. The original timers on early production master A final videotape that contains a machines could program only one event in a 24- continuous program consisting of quality video from hour time period. The serial timer could activate the beginning to end. Original program material is rere- VCR every 24 hours, but the channel remained the corded onto the production master from various same. The programmable timer, introduced in 1978 sources, in piece-by-piece fashion, until the final by RCA, allows programming multiple events on dif- edited video program has been assembled. Also ferent channels for several weeks in advance. called edited master. programming card A chart containing bar-line pat- production switcher A professional switcher/fader terns that are “read” by a pen-like optical scanner used chiefly in broadcast, production and post-pro- to transmit information to a VCR. Part of the bar duction work. The sophisticated unit offers such code programming process featured on several VCR features as 24 video inputs, a control panel divided models, the programming card lists days of the week, into groups, informative displays, dual generators along with a full range of time slots and numbers capable of producing scores of transition wipes, for channel selection. Along with this data are cor- and pattern keys for masking, etc. In addition, the responding bar-line patterns. The VCR owner can production switcher usually provides fade-to-black, set up the machine for recording by using the scan- a split-screen generator, a memory-controlled ef- ner to mark the appropriate information on the card. fects function that can store up to 64 predeter- An IR beam transmits the data to the VCR that then mined set-ups and full event auto-sequencing. can display the recording information on the TV Other models may offer a range of digital effects, screen for confirmation. including image compression and rotation, creation program overlap warning A VCR feature that auto- of 3-D effects and modification of screen image matically detects overlapping conflicts in program- perspectives. See Switcher. ming times. If one selected time range spills over production systems See System terminology. into another time span already preset, the program professional-level monitoring equipment See overlap warning mode blinks an alert so that an ad- Video monitoring equipment. justment can be made. program A sequence of audio signals alone, or audio program start locator A VCR feature that is part of and video signals, transmitted for entertainment or the index search. Usually operating from a jog/shuttle information. dial, the program start locator is activated by mov- program AE In camcorders, a function to select modes ing the dial or search function to a desired starting to suit your shooting situation—for example, por- point of an edit and pressing a button to store the trait mode, sports mode, high-speed shutter mode, location. VCRs that offer this feature often provide twilight mode. AE stands for Auto Exposure. for up to 99 individual index searches. Program Delivery Control (PDC) Information sent program timer A feature that allows the TV set to be during the vertical blanking interval using teletext programmed to automatically turn on at a prede- to control VCRs in Europe. The specification is ITU-R termined time. BT.809. progressive scan See noninterlaced. programmable remote control In addition to con- progressive scanning A type of scanning, used in trolling all major VCR functions, this IR remote con- computer monitors and DTV, in which every line is troller also allows programming timer recordings scanned on every field. The penalty, of course, is remotely. that twice the bandwidth is required over interlaced programmable scan Automatic channel scan. scanning. Digital televisions, as mandated by the programmable speed A VCR feature that permits FCC, can receive either progressive or interlaced for- the presetting of the videotape speed in which a mat. As the technology improves, DTV broadcasts program is to be recorded when the viewer is not in progressive scanning format will dominate. The present. Since TV programs to be set for recording HDTV standard specifies active vertical scanning lines may differ in content (talk shows, dramas, musicals), of 720 progressive () or 1080 interlaced (1080i) the viewer may wish to use a different speed for or higher. SDTV allows 480p and 576p formats. Also each show. Talk shows, for example, do not need called sequential scanning; noninterlaced scanning. standard play (SP mode), so the viewer can set the projection In video, the production of a video picture 6-hour SLP mode while using the SP mode for musi- signal as a strong light image that can be cast on a cals to ensure the best audio reproduction capable screen to attain a display area larger than a CRT is on the VCR. capable of giving. programmable timer A VCR feature that permits set- projection cathode-ray tube A TV CRT that produces ting the timer (automatic timing) to record more than an intensely bright but relatively small image that

220 public room

can be projected onto a large viewing screen by an the division ratio increases. A specific number of PSC optical system. pulses are produced by the PLL IC in response to projection optics A system of mirrors and lenses that channel-selection commands. Most PLL tuning sys- projects the image onto a screen in projection TV. tems found in TV sets use some form of PSC. The Schmidt system is an example. It is also called pseudo color Also pseudocolor. Refers to computer reflective optics. color display technique in which the pixel value in a projection tab Record-protect tab. frame buffer selects an entry in a color table that projection television System for reproducing TV pic- contains the intensities of the three primaries, red, tures in which the image formed on the screen of a green, and blue. Each color table entry typically has small picture tube is optically projected onto a larger 8 bits for each component, giving 256 levels of red, viewing screen. In domestic projection receivers, the 256 of green, etc. At any one time up to 256 colors screen is of ground glass and the optical image is out of a palette of 1024 can be displayed. focused on the rear by an optical system incorpo- PSIP Program and System Information Protocol, a part rating a concave mirror, a plane mirror and a cor- of the U.S. ATSC digital TV specification that en- recting lens designed to minimize optical distortion. ables a DTV receiver to identify program informa- The system is folded to occupy minimum space and tion and use it to create electronic program guides is a version of the system originated by Schmidt for for home viewers. Cable systems routinely ignore use in astronomical telescopes. For larger installa- the information, inserting their own data. tions—in cinemas, for example—the optical image PSTN Public Service Telephone Network. is projected onto the front surface of a reflecting psychoacoustics The study of how the human brain screen. records and deciphers the signals that indicate the projection TV remote control panel An accessory direction from which a sound originates. This sci- that permits the user to perform an array of func- ence has been helpful in producing audio/video tions while remaining away from the projector. Fea- equipment that attempts to duplicate the sound tures available on the remote control pad include often heard in movie theaters. Recently known as the usual registration and alignment and automatic Surround Sound, home systems employing this tech- test sequences. nique can simulate sound sources that may not ac- Pro Logic In audio, a Dolby term that refers to the tually exist. Special speakers built into a TV set, directing of Surround Sound signals to different although installed close to each other, can give the channels with greater effectiveness. Used widely on impression of multiple speakers in several locations. home video system receivers. PTV Portable TV. ProShare Personal videoconferencing system; Intel. public access TV A local channel (or part of one) of Works strictly over ISDN lines, not computer net- CATV that is free to individuals or groups of a local works, and the resulting video is only 15 frames/s. community, based on a first-come, first-served sched- But the system can reach many more people than a ule. Whether as a result of pressure from commer- network-based product such as C-Phone. cial TV to frustrate cable growth and competition, prosumers Consumers who seek to use video equip- from political activists seeking an outlet for their ment in a professional manner or professionals who voices or from idealistic or socially motivated gov- purchase high-end consumer video equipment for ernmental agencies, the FCC passed its first public use in their small business operations. Many manu- access regulations in 1972. Originally ordering four facturers offer equipment with professional video stations (public access, government, education and production features at prices slightly higher than con- leased access), the regulations over the years were sumer gear. Their prosumer camcorders, small vid- eventually eased to one channel. Even this ruling eotape formats, sound and lighting equipment, and was overturned in 1979 by the Supreme Court that accessories straddle the fence between the low end claimed that, since these channels were operating of industrial and professional lines and high-end con- locally, the FCC was overstepping its authority. The sumer equipment. court did, however, note that local authorities as well protocol A set of syntax rules that define the exchange as states can require public access channels. Despite of data, including timing, sequencing, error check- the above decision, many cable companies, aware ing, format, etc. either of their civic responsibilities or the public rela- proximity effect Associated with certain types of mi- tions benefits, still provide some public access time. crophones; the closer the sound is to the mic, the Of the more than 4,300 cable systems in the US, more the bass frequencies are exaggerated. approximately 30 of these are CATV cooperatives PSC Pulse swallow control. and municipal CATV stations. PSC system A system having a high-speed prescaler Public Broadcasting Service (PBS) The national net- with variable-division ratio. The variable-division ra- work of public TV stations. tio depends on the PSC signal from the PLL inte- public room A videoconferencing center that is ar- grated circuit. As the number of PSC pulses increase, ranged with transmission services. Public rooms can

221 public television

be rented by business customers who wish to have as well as testing edits before the actual dubbing a videoconference but do not have a facility avail- and distribution. able at their own offices. pulse distribution amplifier An amp designed to public by noncommercial TV boost the strength of the sync as well as other con- stations, supported mainly by viewers, foundation trols to the proper level for distribution to a number grants and government funds. Commercials are not of cameras, special effects generators, and the like. allowed, but large corporations can be credited for pulse-duration modulation (PDM) See Pulse-width underwriting production costs of special programs. modulation. Pulfrich illusion A process that is part of a 3-dimen- pulse modulation A form of modulation in which sional TV system. Utilized in Japan but originally de- pulses are used to modulate the carrier wave or, more veloped in California, the technique employs a gray commonly, in which a pulse train is used as the car- filter over one eye to create an illusion that objects rier (the pulse carrier). Information is conveyed by moving sideways are coming toward or moving away modulating some parameter of the pulses with a set from the viewer. The Pulfrich illusion process is com- of discrete instantaneous samples of the message sig- patible with 2-D, conventional TV. nal. The minimum sampling frequency is the mini- pulling Caused by part of the input RF signal affecting mum frequency at which the modulating waveform the horizontal oscillator. The top of the picture can be sampled to provide the set of discrete values “pulls” or “tears” to one side. without a significant loss of information. There are pulse and bar signal In TV, a test signal used for k- different forms of pulse modulation. In pulse-code rating measurements. The signal has a duration of modulation only certain discrete values are allowed one line and includes, in addition to a line sync sig- for the modulating signals. The modulating signal is nal, a sine-squared pulse and a rectangular pulse. sampled, as in other forms of pulse modulation, but pulse-code modulation (PCM) A technique for con- any sample falling within a specified range of values verting analog signals into a digital form. In PCM, is assigned a pattern of pulses and the signal trans- the amplitude (voltage) of an analog signal is peri- mitted by means of this code. The electronic circuit odically sampled. In video, PCM divides the light or device that produces the coded pulse train from and dark portions of an image and reassembles the modulating waveform is termed a coder (or pulse them into a flow of data or digital information. In coder). A suitable decoder must be used at the re- audio, it is a digital technique that converts VCRs ceiver in order to extract the original information from into hi-fi audio recorders. PCM uses digital encod- the transmitted pulse train. Pulse modulation is com- ing in place of the conventional analog technique monly used for time-division multiplexing. to reproduce music on tape, presenting a distor- pulse on/pulse off One of the methods employed to tion-free, truer and cleaner sound whose dynamic activate the Pause circuitry of a VCR. range is extended 20 dB. In addition, PCM pro- pulse swallow control See PSC system. vides stereo recording capability on 8mm video- pulse-width modulation (PWM) 1. A form of modu- tape. Although the recording (limited to a frequency lation in which the time of occurrence of the lead- response of only 15 kHz) does not capture the full ing edge or trailing edge is varied from its range of human hearing, it can capture the full unmodulated position. 2. A form of analog control range of all sounds broadcast over the air; it pro- in which the duration of the conduction time of the duces more dynamic range capacity than is other- output transistor or transistors in a switching-regu- wise available from either FM or TV audio lated power supply is varied by modulating the bias transmissions. on the gate or base of the transistors in response to pulse-code modulation recording Format for digi- changes in the load. See Chopper power supply. tal audio recording used by digital audio processors punch up To engage a function button, as in punch- and some 8mm VCR decks. ing up an effect on a special effects generator. pulse cross A special TV monitor mode for testing; pupil The dark circular opening in the center of the iris the display is synchronized so that the synchroniz- of the eye. ing pulse portion of the video signal shows in the purity 1. In color TV, the degree to which a display in center of the display. See also Video monitoring one of the primary colors is free from contamina- equipment. tion by the other primary colors. 2. A ratio of dis- pulse cross display An electronic unit that reposi- tances on the CIA chromaticity diagram that tions a monitor picture so that sync and blanking compares a sample color with a reference standard pulses become visible. This permits VTRs to be ad- light. justed for proper skew, tension and tracking. The purity coil A coil mounted on the neck of a color pulse cross display also checks vertical test signals picture tube, to produce the magnetic field needed and VCR/VTR head switching transients. Other ap- for adjusting color purity. The direct current through plications of the device include monitoring servo the coil is adjusted to a value that makes the mag- lock, take tension and proper sync of editing decks netic field orient the three individual electron beams

222 Px64

so each strikes only its assigned color of phosphor PV Preview monitor. dots. PVC Polyvinyl chloride. purity control A or rheostat that ad- PWM Pulse-width modulation. justs the direct current through the purity coil. Px64 This is basically the same as the H.261 ISDN- purple boundary A straight line drawn between the based videoconferencing ITU standard. The term is ends of the spectrum locus on the CIE chromaticity starting to fade into disuse since H.261 is used in diagram. applications other than ISDN video conferencing. A push A video effect where one image replaces an- newer version of the worldwide standard for other by pushing it across the screen. videoconferencing is ITU H.263.

223 Q

Q 1. In NTSC video, Q refers to the quadrature color quad chroma Refers to a technique where the pixel difference signal. It is 90 degrees out of phase with clock is four times the frequency of the chroma burst. the color subcarrier. 2. CATV superband channel, For NTSC this means that the pixel clock is 14.31818 258-264 MHz. MHz (4 x 3.57955), while for PAL pixel clock is QAM Quadrature amplitude modulation, a down- 17.73444 MHz (4 x 4.43361). The reason these are stream digital modulation technique conforming to popular sample clock frequencies is that, depend- ITU standard ITU-T J.83 Annex B, calling for 64 and ing on the method chosen, they make the chromi- 256 QAM with concatenated trellis coded modula- nance (color) decoding easier. tion. Commonly used in digital cable systems. quad-head recorder VTR using transverse recording. Q channel The 0.5-MHz-wide band used in the Ameri- Quadraplex A system of videotape recording using four can NTSC color TV system for transmitting green- rotating heads on a drum perpendicular to the tape. magenta color information. Original experiments in videotape recording used sta- QCIF Quarter Common Intermediate Format, a man- tionary heads similar to audio tape recording, but since datory part of the CCITT’s H.261 standard, which this method required an unusually high tape speed requires that noninterlaced video frames be sent with of approximately 100" per s, it took thousands of 144 luminance lines and 176 pixels. Also, Quarter feet of tape to record only a few minutes of video Common Interface Format. This video format was information. Obviously, this was impractical as well developed to allow the implementation of cheaper as too costly. Quadraplex, with its rotating heads, was video phones. The QCIF format has a resolution of developed by Ampex in the 1950s. Using 2" tape 176 x 144 active pixels and a refresh rate of 29.97 traveling at only 15" per second, the improved tech- frames per second. nique increased the quality of the video signal placed QDBS (or Q-DBS) Quasi-DBS. on the tape and enabled an hour of information to Q demodulator The demodulator that combines the be stored on convenient-sized reels. Quadraplex is chrominance signal and 90 degrees phase-shifted still used today in broadcasting studios. signal of the color-burst oscillator to recover the Q Quadrascan A technique used in arcade video games signal in a NTSC video decoder. permitting high resolution images to enter the screen Q-Phase A color TV signal carrier that has a phase differ- at different speeds and from all directions. The im- ence of 147 degrees from the color subcarrier. The Q- ages, appearing as targets, reveal exceptional detail Phase is sometimes referred to as the quadrature carrier. in their drawings. Quadrascan was developed by QPSK Quadrature phase-shift keying, a digital fre- Electrohome Electronics for Atari’s arcade video quency modulation technique used to send data game, “Asteroids.” over coaxial cable networks. Used primarily for quadrature Separated in phase by 90 degrees or one sending data from the cable subscriber upstream quarter-cycle. Two periodic quantities that have the to the head-end. same frequency and waveform are in quadrature QQ CATV hyperband channel, 396-402 MHz. when the phase difference between them is 90 de- QSIF Quarter size image format. The computer indus- grees. They therefore differ by 1/4 of a period, one try, which uses square pixels, has defined QSIF to be wave reaching its peak value when the other passes 160 x 120 active pixels, with a refresh rate of what- through zero. Also called phase quadrature. ever the computer is capable of supporting. quadrature amplifier An amp that shifts the phase Q signal The quadrature component of the chromi- of a signal 90 degrees. Used in older color TV sets to nance signal in NTSC color TV; it has a bandwidth amplify the signal 3.58-MHz chrominance subcarrier of 0.5 MHz. It consists of +0.48(R-Y) and +0.41(B- and shift its phase 90 degrees for use in the Q de- Y), where Y is the luminance signal, R is the red sig- modulator. nal, and B is the blue signal. quadrature amplitude modulation (QAM) Quadra- Q.T.R. Quick timer recording. ture modulation in which some form of AM is used

224 Quicktime

for both digital inputs. Used in digital TV transmis- over the incandescent light because it produces a sion; transmission speed: 3.1 bits/Hz. QAM is often bluer light that is closer to daylight, gives more light used in microwave and digital cable TV systems. and throws off less heat. Some models feature an quadrature carrier See Q-Phase. air-cooled housing and a distinct reflector for maxi- quadrature filter A filter that eliminates the quadra- mum efficiency. The light can often be handheld as ture components of signals in systems where infor- well as attached to the video camera. mation is contained in the quadrature modulation quartz-synthesized tuning One of several AFT meth- components of the carrier. ods designed to capture a strong broadcast signal quadrature modulation Method of transmitting two and keep it in phase. Quartz tuning utilizes the de- modulating signals independently on one carrier by pendability of the constant vibration of a quartz crys- splitting the carrier into two components in quadra- tal as its reference point. The crystal, which vibrates ture and using each signal to modulate one of the at the exact frequency of the selected channel, at- components. This method is used in the NTSC and tains very precise tuning regardless of frequency vi- PAL color TV systems to transmit the two color-dif- brations that may occur between channels and ference signals. They are transmitted by suppressed- broadcast signals. PLL is another method used in TV carrier AM of the two quadrature components of monitor/receivers for AFT. the color subcarrier. Quasar See Alpha wrap. quadrature phase shift keying See QPSK. Quasi-DBS (Q-DBS) The use of FSS satellites to pro- quadrature-phase subcarrier signal The portion of vide a broadcasting service. the chrominance signal that leads or lags the in- Quasi-PAL A color signal with alternate line, phase portion by 90 degrees. sequential modulation. quadricorrelator Quadrature information correlator. quaternary phase-shift keying (QPSK) Modula- A circuit sometimes added to the automatic phase tion of a carrier with two parallel streams of non- control loop in a NTSC/PAL video decoder to obtain return-to-zero data in such a way that the data is improved performance under severe interference transmitted as 90-degree phase shifts of the car- conditions. rier. This gives twice the message channel capac- quad split A TV switching effect to produce four dif- ity of binary phase-shift keying in the same ferent images on the screen at the same TV. bandwidth. Used in digital TV transmission; trans- quantization The process of converting a continuous mission speed: 1.9 bits/Hz. Frequently used in sat- analog signal into a set of discrete levels (digitizing). ellite systems. quantization noise Also called quantization distor- QUBE A two-way cable system based in Columbus, tion. This is the inherent uncertainty introduced dur- Ohio, that started operations in 1977. QUBE allowed ing quantization since only discrete, rather than subscribers to reply to video events via a small com- continuous, levels are generated. puterized console. Warner-Amex’s QUBE cable sys- quantizing error Inaccuracies in the digital represen- tem, introduced in Columbus, was the first major tation of an analog signal due to limitations in the experiment in interactive TV. Viewers have judged resolution of the digitizing process. talent shows, given their opinions on political issues, quantum efficiency See Sensitivity. voted, decided the fate of characters in soap op- quarter size A special feature, usually found on pro- eras, etc. Other QUBE systems sprang up across the fessional/industrial equipment such as time base cor- country, but they all eventually ceased operations rectors, that uses digital circuitry to produce an image for one or more reasons, including high expenses one quarter the size of the TV screen. The quarter- and poor marketing of the service. size picture can usually be made to appear in any quick-start A VCR mechanism that brings the picture corner of the screen. on the screen the moment you pop in the tape. A quartz A mineral found in nature and whose crystals mechanical procedure incorporated into some VCRs are highly useful in radio and carrier communica- designed to speed up such functions as play, FF and tion. Quartz crystals that are electrically charged vi- REW. To perform some of these commands, several brate and keep extremely accurate and stable seconds are normally required as the videotape en- frequencies. gages or disengages itself around the rotary head quartz bulb A small lighting element which produces drum of conventional VCRs, particularly those of the a great deal of light for a long period of time. VHS format. Some machines have modified the in- quartz halogen light The lighting source closest to ternal mechanism so that the tape can be wound or natural sunlight; yields a white color temperature unwound in less than two seconds. and offers a very bright lighting source. Quicktime The system software developed by Apple quartz light A special source of illumination for use that can serve as a container for many types of with video cameras. Preferred in low light situations, media, such as video, audio, and animation. the quartz light is balanced for the proper color tem- Quicktime contains compression systems for dif- perature. Although more costly, quartz is preferred ferent types of media. Decompression can be ac-

225 quick timer recording

complished using standard Macintosh hardware al- Quick View (QV) A feature found on some TV sets to though QuickTime accelerator cards with hardware switch between the current channel and the last one decompression chips give much better results. viewed. QV is available from the remote control quick timer recording (QTR) A VCR function that en- transmitter only. ables the device to do impromptu recordings at any Quincunx scanning See Bandwidth reduction (EU- time in the next 23 hours. Just select the channel, set REKA-95 HDMAC system). the recording start time, and the recording duration. QV See Quick View.

226 R

R 1. Red. 2. CATV superband channel, 264-270 MHz. microphone output—for example, in TV production 3. Reset. 4. Restricted; see Movie rating systems. where an actor has a part requiring great mobility. rabbit ears A V-shaped indoor dipole TV antenna The use of a boom mic or a trailing mic lead would whose arms are adjustable in angle and usually in restrict his movements but a radio microphone gives length. The antenna can be attached to the TV set the required freedom. or mounted on a base for use on top of the set. The range of electromagnetic frequen- rack 1. A cabinet or its vertical support or frame. In TV, cies used for radio, radar, and other communica- the lens turret sometimes is called a rack. 2. To set tion, including TV, from about 10 kHz to about 300 up on a rack or to set up generally. To rack a tape is GHz. AM radio operates in the middle of the spec- to put it on the tape player. trum—medium frequency—and FM radio and TV rack mounting Metal racks to which electronic equip- operate at higher frequencies. ment is attached in TV control or editing rooms. The radio window The range of radiofrequencies that are EIA devised a standard size for the racks to enable not reflected by the ionosphere but pass straight most electronic gear to fit into them. The racks are through it. The radio window extends from about slightly more than 19" wide, and all engineering 50 GHz to about 15 MHz (approximate wavelength equipment of that size (or smaller) can be easily range: 6 mm to 20 m). The effect of the ionosphere placed in them. Electronic units that are designed is still noticeable up to 100 MHz but decreases as to be rack-mounted have screw-mouths so they can the radiofrequency is increased. At frequencies above be secured to the racks. 10 GHz, rain can severely affect transmission. High- radial acceleration The rate at which a track on an frequency TV broadcasts fall within the radio win- optical disc accelerates toward and away from the dow and long-distance TV communication therefore center, because it is not perfectly aligned or perfectly requires the use of communications satellites as re- round. flectors. See Communications satellite. radiated interference TV picture disturbance, often RAID Redundant array of independent disks, a group- from such sources as automotive ignitions, power ing of hard disk drives together with a RAID control- transmitter lines and radio stations. Radiated inter- ler to create storage that behaves as a single disk. ference is usually the result of a poorly shielded TV rainbow effect See Moire. tuner. rainbow generator A signal generator that gener- radio The use of electromagnetic waves to transmit and ates a signal which, when fed into a color TV set, receive electrical signals over a distance without con- produces the entire color spectrum on the screen, necting wires. Thus radio, quite properly, embraces with the colors merging together. TV. However, the term radio is often restricted to the raised-cosine pulse See Sine-squared pulse. Because transmission and reception of sound signals. For ex- the square of a quantity is always positive regard- ample, receiver manufacturers commonly divide their less of the sign of the quantity, a sine-squared pulse catalogues into two parts, one describing radio (i.e., is positive for both half-cycles of the sine wave. Each sound) receivers and the other TV receivers. sine wave thus gives rise to two line-squared pulses interference shield RFI Shield. A and these pulses are positive; that is, they stand metal shield enclosing the printed circuit boards of above the zero axis and are thus raised. The identity the printer or computer to prevent radio and TV sin2A = (1-cos2A)/2 shows that the sine-squared interference. pulse is of cosine form and that its frequency is radio microphone A microphone, the audio output double that of the sine wave. of which is used to modulate a low-power transmit- RAM Random access memory, a temporary, volatile ter, the output of which is picked up by a nearby computer memory for storing data. receiver. Radio microphone is often used where it RAMDAC Random access memory digital-to-analog would be inconvenient to use a cable to carry the converter. The chip on a VGA board that translates

227 random access

the digital representation of a pixel into the analog deviation is ± 75 kHz and for the sound channel in information needed for display on the monitor. 625-line TV systems it is ± 50 kHz. random access In viewing and editing, the automatic, rated transmitted power In TV transmitting systems, rapid cuing to any point, particularly with laserdiscs, power at the peak of sync. Cf. average transmitted digital discs or solid-state memory components. On power. a VDP, random access permits the viewer to locate raw VBI data A technique where VBI data (such as instantly any frame on the disc. The frame number teletext and captioning data) is sampled by a fast usually is displayed digitally on the screen by punch- sample clock (i.e., 27 MHz), and output. This tech- ing in the number of the frame on a keypad. nique allows software decoding of the VBI data. random access tuning A feature on TV sets, VCRs or ray Beam. VDPs permitting the selection of any programmed RC-5 Remote control protocol. In the past, insufficient channel by means of touch sensor buttons. This is command capacity of remote controllers and in contrast to older rotary tuners in which other num- nonstandardization of commands and protocols bers must first be passed by. On a remote control, made it impossible to operate all remotely controlled random access is achieved by a set of separate keys equipment from a single remote control handset. for each number from 0 to 9. Random access chan- To solve this problem, Philips developed a remote nel selection is sometimes referred to as direct control (RC) protocol (RC-5) and the ICs to support access. it. The RC-5 protocol provides unified remote con- random interlace Interlace based on less precise trol of consumer equipment. timing of sweep frequencies than is required for RCA Radio Corporation of America. Developed and TV broadcasts. In random interlace the exact po- presented the first color video tape when it showed sition of each line varies with each frame scanned. a two-minute experimental demonstration on Oc- Certainly line 5 will be between lines 4 and 6, but tober 2, 1955 on NBC’s “Jonathan Winters Show.” it may not be exactly centered between the two The company, of course, pioneered in video by pre- lines and its position may vary a little with each senting the first public demonstration of the present frame. This is the system used with home video TV color format in 1953. cameras. RCA DSS All-digital, direct satellite broadcast system range The maximum distance from a TV transmitter delivering high quality TV signals to satellite dishes at which reception of the signal is possible. only 18" in diameter. Modern data-compression rapid access A feature on VDPs designed to locate a technology allows a pair of geostationary satellites desired scene or segment on the disc. The picture is co-located above the equator at 101 degrees West not visible during the rapid access search, but the longitude to transmit hundreds of high-fidelity pro- time delay, operating in conjunction with the stylus, grams to the continental US. Introduced in 1994. acts as a cue to help find the particular excerpt on RCA format This video format used four video heads, the disc. a 90-degrees tape wrap of the head drum, and a 3/ rapid picture search See Visual scan. 4"-wide tape cartridge. The head wheel extended raster 1. Essentially, a raster is the series of scan lines into the inserted cartridge to push against the tape, that make up a picture. It is the random pattern of permitting the head-to-head contact. One signifi- illumination seen on a TV screen when no video sig- cant result of RCA’s investigation of video tape re- nal is present. You may from time to time hear the cording at the time was a customer survey that term raster line, which is the same as scan line. All determined a 2-hour uninterrupted playing time was of the scan lines that make up a frame of video form desired by the TV viewers. a raster. 2. The pattern described by the scanning RCA jack A popular phono jack (sometimes called plug) spot of the electron beam as it scans the target area used in consumer equipment for both audio and of a camera cathode ray pickup tube. video inputs and outputs. The RCA phono type plug raster burn A change in the characteristics of the has become the industry standard for home video scanned area on the target of a camera tube, result- systems. RF connections use the F-type connector. ing in a spurious signal when a larger or tilted raster RCA plug Phono plug. is scanned. RC Time Code Rewritable time code, used in con- RasterOp Abbreviation for raster operation, or another sumer video products. term for bit-block-transfer (BitBlt), a technique for reactance control circuit A color TV receiver circuit image handling in graphics systems. The same term that converts the DC correction voltage from the also is used to refer to the boolean operation that phase detector into a capacitive reactance change can be performed as part of the BitBlt. See BitBlt. that maintains the 3.58-MHz oscillator at the cor- raster operation See RasterOp. rect frequency and phase. Modern TVs use digital rated frequency deviation The maximum value of techniques. the frequency deviation permitted in a FM system. reactivation Process of reviving the thermionic emis- For FM broadcasting in Band II the rated frequency sion of the cathode of CRT. One method is to apply

228 receiver-generated interference

an abnormally-high voltage to the heater for a few Real-time Transport Protocol See RTP. minutes, a process known as flashing. An alterna- Real-time Video (RTV) In DVI technology, the video tive approach is to increase the heater voltage per- compression/decompression technique that operates manently by, say, 10%. Both methods have the effect in real time using the DVI system itself. It provides of “boiling off” the original emitting surface of the picture quality suitable for application development cathode to expose a new surface. purposes, but it is normally replaced by Presenta- read before write A feature of some videotape re- tion Level Video for the final application. corders that plays back the video or audio signal RealVideo® The file format developed by from tape before it reaches the record heads, sends RealNetworks that is used to stream video over the the signal to an external device for modification, and Internet. then applies the modified signal to the record heads rear projection screen In video, a screen used for for re-recording in its original position on the tape. projection from behind the screen with a video cam- read/write head In video, the part of a VCR that reads era in front to make film-to-tape transfers. Rear pro- and writes information on tape. jection screens are recommended over conventional RealAudio® The file format developed by ones which diffuse the light instead of concentrat- RealNetworks that is used to stream audio over the ing it. A rear projection screen can be made at home Internet. by constructing a wooden frame and stapling onto real image An image captured originally from nature, it a special screening material called polacoat. usually by photography, cinematography, or rear projection TV A one-piece console TV system videography. Video refers to a system for electronic that produces a large projected image on the rear representation of images, whether real or computer portion of a special screen. Rear projection TVs usu- generated. Also called realistic image. ally consist of three color tubes (R,G,B) and a highly Real-Time Control Protocol See RTCP. reflective mirror within the projector-cabinet. The real time If a system incorporating a computer oper- picture is projected onto a plastic screen containing ates fast enough that it seems like there isn’t a com- a series of etched concentric rings. This specially con- puter in the loop, then that computer system is structed screen helps to deliver evenly distributed operating in real time. For NTSC video, that’s 30 light over its entire surface as well as a sharp pic- frames/s, with each frame made up of 525 individual ture. The screen also provides an image bright scan lines. That’s roughly equivalent to 60 Mbytes enough to be viewed with ordinary room light. Rear of data per second to be processed. projection TV systems have been gaining in popu- real-time counter A VCR feature that reveals tape larity because they are better suited than two-piece time precisely in hours, minutes and seconds. This is front projection TVs where space is limited. Some accomplished by keeping the tape in contact with rear TV systems utilize a black matrix lenticular screen the control head. Thus, the counter can calculate or black stripe projection TV process to increase pic- the control pulses. This handy feature, sometimes ture contrast. called real-time tape counter, linear time counter, or rebuild The physical improvements made in a cable linear time readout, can measure accurately the system by the replacement of various electronic com- length of programs and can help the viewer to lo- ponents and wiring. In the process, power supplies, cate any point in a tape by simply entering how far amps and other electronic gear are replaced with along in “time” that point is. state-of-the-art technology, and coaxial cables (along real-time digital storage system Professional/indus- with feeder and drop lines) are replaced with a fiber trial equipment, designed chiefly for post-produc- optic system to increase channel capacity. tion work, that uses RAM. These systems can store rebroadcast Repetition of a radio or TV program at a several seconds of digital video information and play later time. it back instantly as a digital videotape recording. receiver 1. A component of a communications sys- Graphics can be added to any portion of the image, tem that converts electrical waves into audible and and the color composition of the frame can be visible forms. Digital TV teceivers, integrated receiver/ changed. Film can be transferred to digital video- descramblers, monitor/receivers, satellite receivers, tape, after which shadows can be added or deleted, transmitter/receivers and TV receivers are some of lettering enhanced, colors manipulated and objects the units that play important roles in video. 2. In a highlighted and textures recreated. All changes are system, the integrated circuit which receives the data stored in memory and can be transferred back onto from the bus. videotape, which can then be edited with a conven- receiver-generated interference A number of spu- tional editor. One of the major benefits of using these rious signals that can be generated by receiving sys- professional workstations is that scenes do not have tems. Two of these, local oscillator radiation and IF to be reshot. images, result from the use of the superheterodyne Real-time Streaming Protocol See RTSP. principle in receivers. A third, intermodulation inter- real-time tape counter Real-time counter. ference, may result when strong signals are received

229 receiver primaries

from two stations having carriers separated by the record lock A feature found on some portable VCRs IF of the receiver. These problems are particularly designed to keep the tape wrapped around the drum troublesome for UHF stations, but they are mitigated when the machine is shut off. By not having to be by the FCC’s policy of channel assignments, which unthreaded and threaded again, the tape remains reduces the possibility of receiver-generated inter- accurately in position, ready for the next glitch-free ference from the use of the superheterodyne prin- recording. Record lock puts the VCR into Record ciple. Another potential source of interference is mode when the machine is turned on. In addition, intrachannel beat frequencies between the sound the VCR uses no power in Off while the camera still and picture carriers. receives power, thereby preserving the battery. If receiver primaries Display color primaries. record lock is pressed down after Off is pressed, the reclocking The technique of clocking digital data with VCR will enter Pause when the machine is turned a regenerated clock. on. In both cases, by having the machine begin in reconnaissance satellite An earth satellite that pro- either Record or Pause, it provides for glitch-free edits vides strategic information, as by TV, photography, between scenes. or radio link. record-protect tab The small square tab on a video- record A control button on all VCRs which, when cassette that, when removed, prevents accidental pressed, permits the machine to record information erasure of the recorded material on the tape. Plac- onto videotape. The VCR can record off the air, from ing a piece of vinyl tape over the opening once again CATV, from a video camera or from another VCR in prepares the tape for recording. Virtually all VCRs duplicating or copying a tape. Some machines pro- have a mechanical sensor that detects the obstruc- vide a safety feature to prevent accidental record- tion and treats the videocassette as though it has ing: two buttons, Play and Record, must be engaged the protection tab in place. Also called projection simultaneously to activate the Record mode. If Pause tab. is pressed while the VCR is in Record, the machine record review A feature on a video camera permit- will stop taping until either Stop is engaged or Pause ting automatic playback of the last few seconds of is disengaged, in which case the machine will con- a recorded tape. The tape is then placed in position tinue to record. for the next scene. With some cameras, this feature record deck Also called the “Target” deck, this is only when they are connected to certain VCRs. deck that source video footage is recorded onto. rectangular picture tube A TV picture tube that has recorded program A radio or TV program that de- an essentially rectangular faceplate and screen. The pends on CDs, electric transcriptions, magnetic typical aspect ratio is 3:5. tapes, or other means of reproduction. rectangular pixel A pixel that has different vertical recorded tape 1. A recording that is commercially avail- and horizontal sample spacing. Rectangular pixels able on magnetic tape, also called prerecorded tape. are usually used by consumer video equipment and 2. Any magnetic tape that has been recorded. video conferencing. Typical rectangular pixel video recorded wavelength A distance on the tape required resolutions are 720 x 480, 720 x 576, 352 x 240, to record one full AC signal cycle. and 352 x 288. recorder An instrument that makes a permanent record rectangular scanning A 2-D TV sector scan in which of varying electrical quantities or signals. A common a slow sector scan in one direction is superimposed industrial version records one or more quantities as a on a rapid sector scan in a perpendicular direction. function of another variable, usually time. Other types rectilinear scanning See Scanning. include the cathode-ray oscilloscope, fax recorder, ki- red/blue balance control A feature on a video cam- nescope recorder, magnetic-tape recorder, and VTR. era to permit adjusting for maximum blue and red record gap A gap that indicates the end of a record reproduction. The effect is either read on an accom- on magnetic tape. panying meter or judged on a nearby color monitor recording Process of impressing an audio or video sig- or receiver. The balance control may also be part of nal on a medium in such a way that it can be repro- a separate accessory, the color control unit or, in more duced whenever required. The impression can take sophisticated camera models, may work automati- the form of mechanical deformation of the medium cally through special circuitry. as in the lateral sound recording of gramophone red difference Syn.: red color difference (R-Y) signal. records, it can be magnetic as in the audio and video red eye A term used by professionals to describe the recording on magnetic tape, or it can be photo- red recording light on the front of video cameras. graphic on film. In all examples there is relative move- The light goes on when the camera is in operation ment between the medium and the recording or as a cue to the actor or subject. Several home video reproducing head. See also Copying. cameras provide this feature. recording amplifier Amp used in a VTR to set the red gun The electron gun whose beam strikes phos- level of the video signal prior to its being supplied phor dots emitting the red primary color in a three- to the video heads. gun color TV picture tube.

230 registration

redistribution The alteration of charges on an area of reference recording A recording of a radio or TV pro- a storage surface in a charge- or TV gram for future reference. camera tube by secondary electrons from any other reference white 1. The light from a nonselective dif- area of the surface. fuse reflector that receives the normal illumination red light The warning light over a door of a studio of a scene. 2. The standard white color reference indicating that it is in use; a light on a TV camera for specifying all other colors. The reference white indicating that it is in use. in color TV approximates direct sunlight or sky light red restorer The DC restorer for the red channel of a that has a color temperature of 6500 K. Primary three-gun color TV picture tube circuit. colors are specified in units such that one unit of reduction A zoom effect with objects being decreased each primary will combine to produce reference in size. Syn.: compression; zoom out. white. red video voltage The signal voltage output from reference white level The picture signal level that the red section of a color TV camera, or the signal corresponds to a specified maximum limit for white voltage grid of the red gun in a three-gun color TV peaks. It depends on the color TV system and usu- picture tube. ally serves as a 100% reference level to calibrate the red zone The flashing red lights outside a TV or film gains and settings of measurement devices. Syn.: studio that indicate a production in progress. nominal white level; white level. reed switch, satellite TV A mechanical switch that reflection The return or change in direction of light, uses two thin slivers of metal in a glass tube to make sound, or radio waves striking a surface or traveling and break electrical contact and thus to count pulses, from one medium into another. which are sent to the antenna actuator controller. reflections Radio waves that have been reflected from The position of the slivers of metal is governed by a a building, hill, or other conductive or magnetic field applied by a bar or other type of semiconductive surface during their travel to a TV magnet. receiving antenna. The resulting longer travel time reel A container that consists of a core and flanged causes ghost images on the screen. ends (a kind of spool) for winding on magnetic tape. refractive projection TV A simple one-tube , two- reel number The number assigned by the operator to piece projection TV system consisting of a TV set, a an audio or video reel or cassette to be used in an special magnifying lens and a large projection screen. edit session; used for the purpose of identifying each The small TV receiver (usually 12 or 13" measured reel or cassette on the edit list for the final assembly diagonally) is often enclosed in some type of box or or for future revisions. cabinet with the lens at the opposite end. The en- reel rocking Refers to finding an exact editing point closure prevents anbient light from dimming the by physically moving back and forth the two reels image. If the system is the result of a do-it-yourself of an open-reel tape recorder. By listening or look- project, the projected image will be backward, up- ing carefully for the cue, one can find the edit point. side down and rather washed out because of the This method was introduced to professional tape nature and quality of the magnifying lens. To cor- editors in 1974 by TV Research International (TVI). rect these shortcomings, manufacturers have pro- Prior to reel rocking, technicians used a more cum- duced systems with special TVs that have inverted bersome numerical procedure for editing. Today’s images and high quality lenses. However, these re- more sophisticated professional editing techniques fractive projection TVs cannot compete with the include, among others, magneto-optical nonlinear image quality and brightness of the more costly disc-based systems or nonlinear editing used in con- three-gun projection TV systems. These limitations junction with solid-state video recorders. no doubt have accounted for the general demise of reel-to-reel format A format of the early VTRs with the refractive system and the success of other large- manual tape “threading” from a supply reel, past screen techniques. the heads, to the take-up reel. refresh rate The number of times each second that reference black level The picture signal level that cor- the information displayed on a nonpermanent dis- responds to a specified maximum limit for black play is rewritten. An example is the number of times peaks. a CRT image must be rewritten or reenergized to reference disc, CD and CDV players Test disc. remain visible and flicker-free. reference oscillator In a color TV set (NTSC, PAL), an register In TV sets, the accurate superimposition of oscillator which is synchronized in frequency and in images from the three-color electron guns in a color phase with the color burst and is used to operate TV tube. Also called registration. the synchronous detectors that decode the chromi- registration In video cameras or video displays, the nance signal. process of causing the three color images to exactly reference phase The phase of the color-burst signal coincide in space. If a camera is not in exact regis- voltage in a color TV receiver, or the phase of the tration, there will be color fringes around sharp edges master-oscillator voltage in a color TV transmitter. in the reproduced picture. In spite of these difficul-

231 registration chart

ties, three-sensor cameras produce the highest qual- remote control range Refers to the effective distance ity images, and this approach is used for all the high- between a remote control pad and a VCR, DVD, TV est performance cameras. Also called register. or VDP. The range varies with different units and registration chart See Video test chart. often depends on the freshness of the batteries in regular reflection Direct reflection. the remote control pad. reinserter DC restorer. remote control unit See Remote control, Remote reinsertion of carrier Combining a locally generated control panel. carrier signal with an incoming suppressed-carrier remote pause button A control on a video camera signal. that permits operating the Pause mode of a VCR rejector Trap. from the camera. This feature, which gained preva- relative time delay The difference in time delay en- lence in 1979, gives the camera operator more flex- countered by the audio signal and the video signal ibility by centralizing more functions on the camera. or between the components of the picture signal However, some older VCRs are not designed to op- traveling over a TV relay system. erate in conjunction with this feature. relay A microwave or other radio system that passes a remote pause/still A button on a VCR remote con- signal from one radio communication link to another. trol panel which (1) stops the tape in Record mode See also Communications satellite. to eliminate undesired material, such as commer- relay channel The band of frequencies for transmit- cials, from being recorded and (2) stops the tape in ting a single TV relay signal, including the guard Play mode to provide a still picture, or freeze frame, bands. on the screen. This feature was first introduced by relay receiver A receiver that accepts a TV or micro- JVC. wave relay input and delivers a TV or microwave re- remote pickup Picking up a radio or TV program at a lay output signal to the transmitter portion of a remote location and transmitting it to the studio or repeater station. transmitter over wire lines or a shortwave or micro- remo See Remote. wave radio link. Also called remote. remote Programs produced or recorded live at a dis- remote sensor A feature on all remote-controlled tance from the TV studio. Also called remote pickup, VCRs, DVD players and TVs that senses the IR signal pickup, field pickup, outside broadcast, or remo. transmitted from the remote control pad. To oper- remote channel change A feature found on the re- ate correctly, the remote sensor depends chiefly on mote control panel of most VCRs that permits chang- two factors. First, the sensor, located on the front, ing the channel number of the recorder’s tuner. It should not be blocked by external objects. Second, also converts the TV receiver into a remote control the batteries in the remote control panel should be set by using the VCR’s tuner and the TV’s open chan- in good condition. nel (3 or 4). Older VCRs equipped with a mechani- remote telephone programming A VCR feature that cal rotary tuner were incapable of utilizing the remote permits the owner to program the unit by telephon- channel change. ing in the required instructions. A conventional remote control Means of controlling an equipment links the VCR to the telephone. from a distance. The link between the remote con- When the phone rings, the machine, which con- trol unit and the equipment may be a cable, an ul- tains a blank videocassette, answers with a beep, trasonic wave or infrared. Many VCRs, DVD players, signaling that it is ready to receive instructions. One TV receivers, VDPs, etc. have facilities for changing enhancement to remote telephone programming is channel, adjustment of different parameters, etc. by the electronic voice which responds to the telephone remote control. call and asks, in sequence, for information concern- remote control directivity Refers to the useful angle ing the day, time and channel for the intended re- range of a remote control pad in relation to the re- cording. ceiver. The effective angle of remote control direc- remote VCR on/off switch A function on the remote tivity depends on the distance between the control panel that controls the VCR button on the VCR. In pad and the unit. In other words, the farther away the VCR position, the tuner of the machine supplies from the sensor on the unit, the greater the angle the channel to the TV set, which now acts as a moni- or degrees. Directivity to some extent depends on tor. In the TV position, the tuner of the TV set be- the condition of the batteries in the remote control comes the source for the screen image, and the VCR pad. remains inactive unless it is recording another pro- remote control panel An electronic component con- gram from a different channel. taining all the function buttons necessary to oper- rendering Process of non-realtime drawing of a pic- ate a VCR, DVD, VDP and similar units that are some ture relying on computer processing speed for graph- distance away from the viewer. Remote control pan- ics and composing. els can be portable, fitting into the palm of a hand, repeat play A VCR feature that instructs the machine or can be desktop or console models. to play a videotape up to an index signal, stop and

232 retinal illumination

rewind to a previous index signal and continue to record and play back 3 MHz, then that machine is play that portion of the tape indefinitely until the listed at 240 lines. Black and white and color resolu- repeat play mode is pressed again. The length of tion are usually listed separately in specifications. the section to be replayed depends upon the mini- With a video camera, resolution refers to the maxi- mum time between two indexes. The Repeat fea- mum number of clear lines discernible on a resolu- ture also appears on several VDPs. Some offer two tion or video test chart. Resolution depends on Repeat modes—one that replays the present chap- several factors. Industrial or commercial equipment, ter or track, and another, sometimes called Repeat for example, generally produces higher resolution. All, that plays back the entire disc. Repeat play dif- Different consumer formats yield disparate ratings. fers from Auto Repeat, a feature on some VCRs and The ED-Beta format can generate more than 500 VCPs that replays the entire videotape. lines of horizontal resolution; laserdisc players, 425 ReplayTV™ One brand of Personal Video Recorder lines; S-VHS format (both camcorders and VCRs), (PVR), also called a digital video recorder (DVR). An more than 400 lines; broadcast TV, between 300- intelligent “black box” that records TV shows to an 330 lines. internal hard drive, allowing live TV to be paused, resolution chart Test pattern. See also Video test chart. rewound, played in slo-mo, etc. resolution independent Describes equipment that can residual elongation Refers to the capabilities of a operate at more than one resolution. Some modern videotape to return to its original length after it has TV equipment, especially that designed by the ITU-R undergone tension for a long period of time. Most BT.601 standard, can switch between specific formats tapes tend to stretch to some degree. However, be- and aspect ratios of 525/60 and 625/50. yond a certain point, usually listed at about 5%, elon- resolution line See Res-line. gated tapes become unplayable. Residual elongation resolution wedge A test pattern for resolution of a is only one of many factors that determine the over- video camera system consisting of a group of lines all quality of a tape. Manufacturers rarely list this angled so that they come closer together as you measurement on their packages move across the pattern. residual subcarrier The amount of color subcarrier resonant-line tuner A TV tuner in which resonant information in the color data after decoding a NTSC lines are used to tune the antenna, RF amp, and RF or PAL video signal. The number usually appears as oscillator circuits. Tuning is achieved by moving short- -n dB. The larger “n” is, the better. ing contacts that change the electrical lengths of resistor ladder A string of resistors used for defining the lines. voltage references. In the case of 8-bit flash ADCs, Resource Reservation Protocol See RSVP. the resistor ladder is made up of 256 individual re- response control A function on an image enhancer sistors, each having the same resistance. If a voltage (or mini-enhancer) designed to cut the high-fre- representing the number 1 is attached to one end quency noise of a video signal. The response con- of the ladder and the other end is attached to 0, trol usually works in conjunction with an enhance each junction between resistors is different from the control. First, the enhance (sharpness) button or dial other by 1/256. So, if we start at the top of the lad- is adjusted to a point where the picture appears der, the value is 1. If we move down one rung, the sharp, but slightly grainy. Then the response control value is 0.99609, the next rung’s value is 0.99219, is used to reduce the noise as much as possible with- the next rung’s is 0.98828 and so on down the lad- out affecting the sharpness or detail in the picture. der until we reach 0 (the other end of the ladder). A The control can often decrease 3-MHz signals, com- resistor ladder is an important part of a flash ADC posed mostly of noise, from zero to almost half their because each rung of the ladder, or tap, is connected enhancement. to one side of a comparator, in effect providing 256 retentivity In videotape, the ability of the particles references. See Flash A/D. that form the magnetic medium to keep their mag- res-line Resolution line. A line used to make up the netic charge. A tape with high retentivity character- image on a TV screen. istics demonstrates high quality. resolution The ability of an image reproducing sys- retina A delicate, multilayered, light-sensitive mem- tem to reproduce fine detail. In TV, resolution is a brane lining the inner eyeball and connected by the measure of sharpness of a TV image in both vertical optic nerve to the brain. The retina of the human and horizontal axes. TV resolution measurements are eye is covered with cones and rods, cells that ab- usually made with a test pattern that includes test sorb light and send electrical signals to the brain to wedges (a collection of black and white lines that form visual images. In 1995, for the first time, it be- converge at the center of the pattern), calibrated in came possible to see individual cones—the cells that lines per picture height. Horizontal resolution is mea- allow us to detect color. sured in lines. For NTSC and PAL, the number of retinal illumination Illumination that is determined lines results from multiplying 80 by the peak video by the image brightness and the size of the pupil’s frequency of the VCR. For instance, if a VCR can aperture. The latter, in turn, depends on the bright-

233 retinal image

ness of the surroundings as well as that of the im- the electron gun. Light falling on the target surface age itself. In a darkened motion picture theater, the changes the resistance of the surface, and thereby surround brightness is low, the pupil aperture is rela- modulates the energy in the return beam. tively large as the eye automatically adjusts to the return interval Retrace interval. low light level, and the retinal illumination is high in return line Retrace line. relation to the screen brightness. In a typical home return loss A measure of the ratio of signal power environment, the surround brightness is higher, the transmitted into a system to the power reflected or pupil aperture is smaller, and the retinal illumina- returned. tion is lower in relation to the image brightness. As return monitor A TV screen linked to a TV camera, so a result, the image brightness can be greater with- that an interviewee or broadcaster in one studio, out causing visible flicker in a home TV set than with for example, can see the interviewer or anchor in motion pictures in a theater. The difference is in- another studio. Ordinarily in such situations, the in- creased still further by the use of the lower field rate terviewee only can hear the interviewer. of 48 per second in motion picture systems. return period Retrace interval. retinal image In the human eye, the retinal image return time Retrace interval. received by one’s left eye and one’s right eye are return-to-zero code (RZ code) A communication code slightly different due to the eye separation (each eye in which a binary 0 is represented by one bit time at sees the scene at a slightly different angle), which the 0 level, and a binary 1 is pulsed so that it reaches differences the brain processes to produce neural the 1 level for only half a bit time. The signal there- depth information to give the perception of stereo fore returns to 0 (or stays at 0) after each bit. With depth. The same concept is realized electronically in this code, only half as much data can be stored in a some 3D TV systems. How the brain knows which given area or distance as with NRZ code. points in the retinal image corresponds to given reveal 1. To disclose; to bring to view; to make known: points in the right one is a mystery. In 3D TV sys- The person’s brain would interpret the two displays tems, this information can be obtained by each point to reveal its three-dimensional aspects. 2. In film, being tagged in turn with the laser beam. TV, a shot in which the camera is pulled away or the retrace The return of the electron beam to its starting lens zoomed or focused outward to enlarge the point in a CRT after a sweep. It is also called flyback. scene. In TV, a reveal is a succession of computer- retrace blanking Blanking a TV picture tube during generated lines of text that give the impression of vertical retrace intervals to prevent retrace lines from one line at a time being added to the screen, a com- showing on the screen. Voltage pulses for blanking mon technique in newscasts such as weather, sports are derived from a vertical sweep oscillator or verti- scores, and other lists. cal deflection circuits, and are applied to the control reverb Reverberation. grid of the picture tube. reverberation The persistent repetition of a sound retrace ghost A ghost image produced on a TV re- after the original sound has ceased: Hello-hello-ello- ceiver screen during retrace periods. Generally ello; caused by sound waves bouncing off objects caused by insufficient blanking of the camera tube and surfaces and thus reaching the ear or micro- at the transmitter. phone later than the original sound. Reverberation retrace interval The interval of time for the return of is characterized by a gradual cessation of sound, not the blanked scanning beam of a TV picture tube or to be confused with echo. camera tube to the starting point of a line or field. It reverberation time Of a room, hall or studio, the is about 7 µs for horizontal retrace and 500 to 750 time taken for the intensity of a sound to fall by 60 µs for vertical retrace in NTSC and PAL TV. It is also dB. It is an important parameter because if speech called retrace period, retrace time, retrace interval, is to be clear in a small room, the reverberation time return period, or return time. should be about 0.3 s over the audible spectrum. retrace line The line traced by the electron beam in a Similarly good acoustics in an orchestral hall require CRT in going from the end of one line or field to the a reverberation time of about 2 s and independent start of the next line or field. It is also called return of frequency. line. reverse compatibility Of a color TV system, a prop- retrace period Retrace interval. erty that permits a color TV receiver to reproduce a retrace time Retrace interval. normal black and white picture. return-beam mode A camera-tube operating mode reverse image switch A home video camera feature in which the output current is derived from that that permits changing the image from positive to portion of the scanning beam not accepted by the negative. This switch may be used to reverse photo- target. graphic negatives to positive pictures on the TV return-beam vidicon A vidicon whose electron beam screen. that scans the target is bent back from the target to reverse polarity adapter An accessory cable which an electron multiplier and anode which surround restores the original functions of a video camera that

234 ribbon microphone

is used with an incompatible portable VCR. For ex- and the splitter in the first example above and be- ample, although both units may be VHS in format, tween the VCR and the splitter in the second ex- the multi-pin connectors may not match. A green ample. An RF amp differs from a video distribution light in the camera viewfinder may go on when the amp in that the former produces RF signals that can VCR is off and may go out when the machine is be fed directly to TV receivers. operating. To reverse these functions, some video RF converter An accessory which converts or changes supply houses sell reverse polarity adapters. any video source such as a portable VCR or a video reverse polarity control Reverse image switch. camera to an RF signal for direct hook-up to a reverse scan See Visual scan. receiver’s input. The alteration is necessary since a review To scan the playback picture at a faster-than- video signal is different from and not compatible normal speed in the reverse direction. Syn.: search- with an RF signal. RF converters are sold separately reverse. or as combinations with image stabilizers. review button On some cameras, a control which RF copying See Copying. plays back, both in reverse and forward, the last few RF modulator An accessory designed to combine sepa- seconds of a tape through the electronic viewfinder rate audio and video signals from VCRs, image en- before the recorder reverts to Record/Pause mode. hancers, video cameras and other image processors The button is usually located on the handgrip of into an RF signal which can then be played through some cameras. a TV set. In a VCR, the RF modulator places a low- rew Rewind. power RF signal over the audio/video signals to trig- rewind A control button on all VCRs to rewind the ger the TV into accepting the transmission as a videotape in the cassette either partially or fully. On normal TV signal. top-of-the-line machines, the rewind solenoid con- RF signal The signal that mixes together audio and trol has an additional function. When pressed half- carrier signals; also, audio and video signals that can way while the VCR is in Play mode, the reverse visual be transmitted. RF refers to the range of frequen- scan feature is activated and the picture appears on cies used to transmit electric waves. RF, audio and the TV screen in reverse without sound. video signals are different in nature. For example, rewind auto shut off A function of some VTRs. When image processors accept video signals but do not the power button is pressed during the rewind mode, accept RF signals. including auto rewind, these VTRs will eject the cas- RF switcher See Switcher. sette and turn themselves off when rewinding is RG-6 See Coaxial. completed. RG-11/u A coaxial cable cable that is electrically simi- rewinder An accessory for rewinding videotape. The lar to RG-59/U coax, but with larger conductors for use of a rewinder keeps the tape away from the less signal loss over long distances. video and audio heads in this mode, thereby pro- RG-58A/u 50-ohm coaxial cable. Used in TVs to take longing their life to some degree. The rewinder is IF signals from a tuner; the low-impedance output also useful for uninterrupted use of the VCR. Since circuit of the tuner is interfaced with the input of the accessory is a separate unit, it can rewind one the IF amp. tape while another is playing or recording in the VCR. RG-59/u A type of coaxial cable characterized by an In addition, the rewinder, which is a relatively inex- impedance of 75 ohms, which is commonly used pensive item, saves on the wear and tear of the re- for the transmission of video signals. See also Co- winding mechanism of a VCR. Repairing or replacing axial. these parts can result in a relatively expensive repair RGB A color model based on the mixing of red, green, bill. Also called auto-winder, videocassette rewinder. and blue—the primary additive colors used by color rewind/review A button to rewind the tape. When monitor displays and TVs. The combination and in- this button is pressed during playback, the picture tensities of these three colors can represent the can be scanned in reverse at five times normal speed. whole spectrum. Color TV signals are oriented as RF Radio frequency. three separate pictures: R,G and B. Typically, they RF adapter A unit which acccepts the composite video are merged together as a composite signal but for signal and modulates a carrier frequency to produce maximum quality and for computer applications the a predetermined TV bandwidth, thus producing a signals are segregated. broadcast signal. See RF converter. RGB input A feature on some monitors and TVs that RF amplifier A device designed to maintain RF signal feeds the individual red, green and blue signals and strength, especially when that signal is split. For in- a sync signal directly to a picture display. stance, an amplifier may be necessary when an an- RHC Right-hand circular (polarization). tenna signal is divided between two or more TV ribbon In TV, the horizontal crawl superimposed at receivers with exceptionally long wires separating the bottom of the screen, such as for news bulleting them; or when a VCR is feeding a few TV receivers. or promotional announcements. The RF amp is connected between the antenna line ribbon microphone A velocity microphone whose

235 rim light

moving element is a thin corrugated metal ribbon dio system, network interfaces and other compo- mounted between the poles of permanent magnets. nents. These roll about systems can, in theory, be The ribbon cuts magnetic lines of force as it is moved moved from room-to-room but in fact are not, be- back and forth in proportion to the velocity of air cause they are electronic equipment that does not particles in a sound wave, so an AF output voltage benefit from jostling and are also heavy. is induced in the ribbon. It is an old-fashioned and roller A rubber tire or wheel. not very durable mic since the “ribbon” tends to rolling dropouts Horizontal lines, resembling fray at the edges. Used in TV. scratches, that move rapidly through the screen im- rim light Kicker. age. The problem is associated chiefly with video- rim magnet Field-neutralizing magnet. discs. Occasionally appearing in clusters, these rolling ringing 1. An oscillatory transient that occurs in the dropouts are often the result of a faulty aluminum output of a system as a result of a sudden change in coating or a defective videodisc stamper. input. In TV it might produce a series of closely roll off The preset attenuation of a predetermined spaced images or a black line immediately to the range of bass frequencies, used by some microphone right of a white object. Ringing in the video amp manufacturers on their mics to reduce the proximity gives rise to regularly spaced vertical stripes to the effect. right of each vertical line in the picture. 2. Refers to ROM Read only memory, a computer memory device a series of ripple-like effects that appear at the edge that is programmed once with a permanent pro- of a high-contrast object. Ringing tends to be a pe- gram or data that cannot be erased. culiarity more of tube-type than solid-state video rooter amplifier A nonlinear amp whose negative cameras. The problem results from random capaci- feedback makes the output voltage vary as the tance within the circuitry. A video test chart can de- square root or some other root of the input volt- termine whether a camera produces ringing in its age. It is used in TV transmitter video amps for image. gamma correction to compensate for camera-tube ripple effect 1. A condition of videotape that is stored characteristics. and not played for long periods of time. Because of rostrum camera An adjustable camera commonly this inactivity, the tape may develop wrinkles during used in TV and film animation to shoot artwork or recording. These wrinkles tend to develop the ripple other graphics on a table or other horizontal effect. Tape technicians usually recommend running surface. tapes through VCRs once in a while so they don’t rotary chroma The name of the process used in VHS “memorize” particular patterns during their setting to change the phase of the chrominance signal at a period. 2. A phenomenon occurring in videotape rate of 15,734 Hz (same as the TV horizontal sync time-code AB roll editing. When the position or frequency). length of an edit is changed from the original mas- rotary erase head A set of heads on the rotating ter list, the starting times and positions of all of the video-head assembly which erases the video signal following scheduled edits must also be changed. during recording and editing; usually positioned one RLE Run length encoding, a compression scheme. scan line in front of the video heads; produces RO Receive only. cleaner edits than a stationary erase head. Robot 1. Abbreviation for Robot 1200C scan converter, rotary idler Stationary guide along the tape path. pioneering a device that converted images in one rotary wipe A special effect produced by a mix/effects TV standard to another, in this case between slow- switcher in which a rotating radial line replaces one scan TV (SSTV) and NTSC/PAL, so camcorders, TV video image with another. The result is similar to that monitors, etc., could be used for creating and dis- of a clock hand rapidly moving around the dial. playing SSTV images. The Robot 1200C was discon- rotation Refers to a waveform monitor function de- tinued in 1992. 2. A family of SSTV transmission signed to adjust the instrument to the magnetic field modes introduced with the 1200C. at a shooting site. Rotation control is one of several Robot 1200c scan converter See Robot. basic features found on such units as portable wave- robotic television cameras Cameras without opera- form monitors, or oscilloscopes. tors. Mounted on tracks, they can be manipulated rough edit A rapid assembly of various segments in from the control room by a single operator seated the order they will appear in the final program; not at a computer panel. a finished master tape; not a clean edit. roll 1. A reel or spool of tape, film, paper, or other route To direct, send, forward, or transport by a speci- material. 2. Loss of vertical sync causing the picture fied route: the second camera display is routed to move up or down the screen. Roll may result from through a separate prism to the viewer’s right eye. anti-copying devices placed on commercial prere- routing switcher An accessory unit that directs sev- corded videotapes. eral audio and video connections into one box so roll about A totally self-contained videoconferencing that signals can be matched with various destina- system consisting of the codec, video monitor, au- tions. Routing switchers often incorporate a distri-

236 run length coding

bution amp that splits one input into more than one to reserve resources to guarantee a given quality of output for purposes of copying with little signal loss. service. Some switchers handle six VCRs, an auxiliary source, RTP RTP (Real-Time Transport Protocol) is a packet for- an external processor and a TV monitor/receiver. mat and protocol for the transport of real-time audio These units offer more flexibility, including mixing a and video data over an IP network. The data may be VCR picture with the audio of a CD and taping the any file format, including MPEG-2, MPEG-4, ASF, result on a separate VCR. Professional routers may QuickTime, etc. Implementing time reconstruction, feature HDTV compatibility at 30 MHz, remote con- loss detection, security and content identification, it trol and more than one level of switching. also supports multicasting (one source to many re- rover A portable TV camera, particularly the Sony ceivers) and unicasting (one source to one receiver) Portpack. of real-time audio and video. One-way transport (such RP-125 A SMPTE parallel component digital video rec- as video-on-demand) as well as interactive services ommended practice. Now SMPTE 125M. (such as Internet telephony) are supported. RTP is RPM Revolutions per minute. designed to work in conjunction with RTCP. RR CATV hyperband channel, 402-408 MHz. RTSP RTSP (Real-Time Streaming Protocol) is a client- RS-170 The U.S. standard that was used for black and server protocol to enable controlled delivery of white TV, and defines voltage levels, blanking times, streaming audio and video over an IP network. It the width of the sync pulses, and so forth. The speci- provides “VCR-style” remote control capabilities fication spells out everything required for a receiver such as play, pause, fast forward, and reverse. The to display a black and white picture. The output of actual data delivery is done using RTP. the small black and white security cameras hanging RTV Real-time video. from ceilings conforms to the RS170 specification. RTX Real-time executive. A subsystem module, DVI. It RS-170A RS-170, modified for color TV by adding the is a form of multitasking which runs inside of a DVI color components. When NTSC decided on the color application. The basic working unit of RTX is a task; broadcast standard, they modified RS-170 just a little the interrupt structure of the PC is set up so that a bit so that color could be added, with the result be- number of RTX tasks can operate “simultaneously.” ing called RS-170A. This change was so small that This is accomplished by interrupting the CPU 30 existing black and white TVs didn’t even notice it. times per second (not synchronized with the video RS-232 A standard, single-ended interconnection frame rate, however). When AVSS is running it acti- scheme for serial data communications. vates three high-priority RTX tasks: a server task, a RS-343 RS-343 does the same thing as RS-170, defin- decode task, and a display task. These three tasks ing a specification for video, but the difference is do all the detail work of playing video and audio. that RS-343 is for higher-resolution video (comput- rule of thirds A TV production guideline stating that ers) while RS-170 is for lower-resolution video (TV- the center of attention of a picture should be one resolution video). third of the way from the top of the screen or one RS-422 A medium-range balanced serial data trans- third of the way from the bottom, or one third from mission standard. Widely used for control links either edge of the screen. It should never be in the around production and post areas for a range of dead center of the picture. equipment. rule of thumb This rule says that you should be seated RSDL RSDL stands for Reverse Spiral Dual Layer. It is a at least 7 feet from a 31" screen, 15 feet from a storage method that uses two layers of information 52" screen and 17 feet from a screen that is 100" on one side of a DVD. For movies that are longer or larger. than can be recorded on one layer, the disc stops run length coding A type of data compression. Let’s spinning, reverses direction, and begins playing from say that this page is wide enough to hold a line of the next layer. 80 characters. Now, imagine a line that is almost RSVP RSVP (Resource Reservation Protocol) is a con- blank except for a few words. It’s 80 characters long, trol protocol that allows a receiver to request a spe- but it’s just about all blanks—let’s say 50 blanks be- cific quality of service level over an IP network. tween the words “coding” and “medium.” These Real-time applications, such as streaming video, use 50 blanks could be stored as 50 individual codes, RSVP to reserve necessary resources at routers along but that would take up 50 bytes of storage. An al- the transmission paths so that the requested band- ternative would be to define a special code that said width can be available when the transmission a string of blanks is coming and the next number is actually occurs. the amount of blanks in the string. So, using our RTCP RTCP (Real-Time Control Protocol) is a control example, we would need only 2 bytes to store the protocol designed to work in conjunction with RTP. string of 50 blanks, the first special code byte fol- During a RTP session, participants periodically send lowed by the number 50. We compressed the data; RTCP packets to convey status on quality of service 50 bytes down to 2. This is a compression ratio of and membership management. RTCP also uses RSVP 25:1. Not bad, except that we only compressed one

237 running log

line out of the entire document, so we should ex- running log A sequential listing, such as the log of TV pect that the total compression ratio would be much programs by time period. See also Grid log. less. Run length coding all by itself as applied to running shot See Moving shot. images is not as efficient as using a DCT for com- R-Y matrix A circuit to construct color difference sig- pression, since long runs of the same “number” nal R-Y according to the equation R-Y = 0.7R — rarely exist in real-world images. The only advan- 0.59G — 0.11B. tage of run length coding over the DCT is that it is R-Y signal The red-minus-luminance color-difference easier to implement. Even though run length cod- signal used in color TV. It is combined with the lumi- ing by itself is not efficient for compressing images, nance signal in a receiver to give the red color-pri- it is used as part of the JPEG, MPEG, H.261, and mary signal. H.263 compression schemes. RZ code Return-to-zero code.

238 S

S CATV superband channel, 270-276 MHz. a process in which the value of a continuously vary- SABC South Africa Broadcasting Corporation. ing signal is measured at regular time or distance saddle coils Coils for magnetic deflection, usually of intervals. The values of the samples are reconverted rectangular form and shaped so as to fit the neck of to a continuous function, either electronically or by a CRT. the retentivity of the eye. Two sampling procedures safe-action area See , Safety. are employed in TV scanning. Variations in vertical safe area 90% of the TV screen, measured from the brightness are sampled by the scanning lines, and center of the screen; that area of the display screen the positions of objects in motion are sampled by (and therefore of the camera scanning area) which scanning the entire raster. will reproduce on every TV screen, no matter how sampling rate The number of times per second that the set is adjusted. Also called safe-action area. an analog signal is measured and converted to a safe title area 80% of the TV screen, measured from binary number, the purpose being to convert the the center of the screen; that area of the display analog signal to a digital signal. screen (and therefore of the camera scanning area) sand bags Canvas sacks filled with sand used to pro- which will reproduce legible title credits no matter vide stability and ballast to light stands, tripods, and how the set is adjusted. other portable equipment. safety 1. Extra copy of a video tape kept in case some- sandcastle pulse (SC) A pulse used in older color TV thing happens to the original copy; usually a sec- receivers. It has two levels (SSC has three levels): burst ond generation copy, although on special effects gating level (required input more than 7 V) and line- generators with two program outputs it’s possible blanking level (required input voltage 4 to 5 V, typ. to record two master tapes, one to be set aside as 4.5 V). the safety tape. 2. The outer area, or safety area, of Sanyo V Cord Two format The first consumer video a TV film or tape, often eliminated and not seen on machine to offer two recording speeds, freeze-frame the screen of a TV set. Broadcasters therefore con- and slow motion. Introduced in 1976. No longer fine text and action to the centered area—about manufactured. 90%—called the safe-action area. SAP Separate (also Second, Secondary, Special) Audio safety-action area See Safety. Program. A monaural channel provided for by the safety area See Safety. EIA’s BTSC (Broadcast Television Systems Commit- salad A pileup, such as the wedging or jamming of tee) standard. SAP was designed as an additional film or tape in a camera, printer, or projector; also soundtrack for bilingual programs or other such called jam. purpose without interfering with monaural recep- sample To obtain values of a signal at periodic intervals. tion of current TV receivers. Used in some multichan- Also the value of a signal at a given moment in time. nel TV sound (MTS) broadcasts. The SAP feature sample and hold A circuit that samples a signal and usually can be controlled from the remote control holds the value until the next sample is taken. of a monitor/receiver or TV set. Transmission of the sample rate Sample rate is how often a sample of a SAP channel is at the option of the local broadcast signal is taken. The sample rate is determined by station and may not be present along with the ste- the sample clock. reo broadcast signal. sampling 1. Converting continuous signals, like voice SAP indicator A feature, located on the front panel or video, into discrete values—for example, digital of some VCRs, that lights up when a second, or sepa- signals. In order that the output values represent rate, audio program broadcast is received. the input signal without significant loss of informa- SAS-AD1 Digital satellite system hardware introduced tion the rate of sampling of a periodic quantity must in 1995 providing home reception of up to 175 chan- be at least twice the frequency of the signal, called nels via high-powered satellite and requiring a dish the Nyquist rate. 2. Scanning is a form of sampling, only 18" in diameter; Sony.

239 SATCOM

SATCOM The name of satellites built by RCA Astro- with a solar-cell power supply can produce about Electronics and operated by RCA Americom. 500 W of output power. SATCOM I was the second commercial satellite in satellite dish A special antenna used in conjunction the U.S., launched in 1975. These satellites distrib- with a TV satellite system. The dish shape collects ute programming to cable-TV systems and provide and concentrates signals from the satellite. Fixed network radio transmissions, as well as commercial dishes are targeted for reception of a single satel- and government voice, data, and video services. lite, while rotating dish antennas are aimed at sev- SATCOM F1 American TV satellite (operated by RCA) eral satellites. C-band antennas range from 5–12 ft. used to supply most of the cable-TV programming in diameter, while Ku-band antennas range from 18 on 24 transponders (12 are vertically and 12 are hori- inches to 6 ft. zontally polarized). It is located at 135 degrees west satellite focus The area on earth covered or focused longitude. Also referred to as F1. upon by a particular satellite’s transmission. The sat- SATCOM F2 American TV satellite (operated by RCA) ellite signal may vary from narrow to broad in the used to supply assorted video and data program- zone or land area it reaches. For example, one type, ming to and other points in the US. Like the domestic satellite, transmits its signal to a con- its sister, F1, it too has 24 transponders. It is lo- fined area, such as one country. It is also known as a cated at 119 degrees west longitude. Also referred spotbeam satellite. A second kind, the hemispheric to as F2. satellite, transmits to an individual hemisphere. It, satellite A manmade object orbiting the earth which too, has another name: zone satellite. The global or has revolutionized all aspects of telecommunictions international satellite transmits to large areas of and brought the concept of a “global village” into earth. Some satellites may have signals that cover the realm of possibility. Television became a major two or all of the areas above. user of communications satellites in the 1970s. A satellite location The position of a communications satellite is placed in orbit 22,300 miles above the satellite in orbit for the purpose of receiving and earth’s equator so that it travels at the same speed transmitting various signals. There are various sources as that of the earth’s rotation (geosynchronous). of information for owners of satellite TV systems that Onboard transponders receive the signals and trans- reveal where satellites are and which programs ap- mit them back to earth after converting them to a pear on each. Home satellite handbooks list the lo- frequency that can be received by a ground-based cations of satellites and how they operate. Wall antenna. Among those who have placed communi- charts position the many satellites and their foot- cations satellites in orbit are AT&T, the Canadian gov- prints. Monthly magazines provide a program guide ernment, , RCA, and Western Union. to all the US satellites. Also called artificial satellite. Satellite Master Antenna Television (SMATV) An Satellite Broadcasting and Communications alternative over-the-air system of delivering satellite- Association (SBCA) Formed in 1986 from the transmitted channels. SMATV entails communal use merger of SPACE and the Direct Broadcast Satellite of a dish, receiving and distribution unit, and cable Association (DBSA) to represent all segments of the network. The system offers clear reception via cable satellite consumer services industry. (www.sbca.org) to the TV receivers of apartment or hotel dwellers. satellite channels The two bands allocated for TV Also called private cable. satellite broadcast are the C-band (4 to 6 GHz) and satellite modulator Satellite TV modulator. the Ku-band (10–17 GHz). The downlink spectrum satellite newsgathering See SNG. for the C-band satellite system consists of 24 chan- satellite news vehicle (SNV) See SNG. nels, each having 40-MHz bandwidth, in the 3.7- to satellite programmer A company that produces, 4.2-GHz frequency band. Each channel overlaps its packages, or distributes video, audio, and/or data adjacent channel by 20 MHz. Even-numbered chan- services for distribution to the home satellite dish nels are horizontally polarized to give a minimum of and cable markets. 30-dB separation. Satellite transponder power out- satellite receiver The component of a satellite TV sys- put is 5 to 10 W. The Ku-band has been split by the tem designed to convert the microwave signal to FCC into two segments: the 11.7–12.2 GHz band VHF and modulate it for acceptance by the antenna known as FSS (Fixed Satellite Service), and the 12.2– input of the TV receiver. A satellite receiver may be 12.7 GHz segment known as BSS (Broadcast Satel- built into the horn assembly of the dish just as the lite Service). The number of channels that Ku-band LNA is, or attached to the base of the dish or kept satellites are capable of delivering is rapidly increas- indoors. Those built into the antenna allegedly mini- ing due to improved technology. mize signal loss by the absence of cables and addi- satellite communication Communication with an tional circuitry. The more sophisticated table-model active or passive satellite to extend the range of a receivers, also known as integrated receiver/ radio, TV, or other transmitter by returning signals descramblers (IRDs), have a host of special features, to earth from an orbiting satellite. An active satellite including integrated descramblers, on-screen menus

240 scaling

for various controls, programmable tuners, digital gions of allowed and attenuated frequencies. Used stereo sound and video noise reduction for clearer in TV sets and VCRs to assure the desired IF response. images. Usually the SAW filter is located between the tuner satellite signal An FM signal carrying both audio and and IF amp. video information transmitted from an earth station sawtooth A periodic signal, named for its shape, in (uplink) to a satellite which converts the signal be- which each cycle consists of a linear change followed fore returning it (downlink) to a ground station an- by a rapid return to the value at the beginning of tenna. The International Telecommunications Union the linear change. Such signals are used extensively (ITU) has set aside space in the super high frequency for feeding the deflecting systems in TV picture tubes (SHF) bands located between 2.5 and 22 GHz for and camera tubes, and also in the conversion be- satellite transmissions (microwave frequencies). tween analog and digital signals. The linear rise is satellite transponder See Transponder. known as the working stroke (active interval) and satellite TV Refers to any of the satellites in orbit the rapid collapse as the flyback or retrace. In most (22,300 miles above the equator), each of which generators a sawtooth voltage is developed across can collect signals from broadcasters and amplify a capacitor by passing a constant current through them before sending them back to earth via the mi- it, flyback being achieved by discharging the capaci- crowave band. The three basic units of a satellite TV tor. Such circuits may be free-running, in which case system include a special antenna, a low-noise am- they are usually synchronized by external signals or plifier (LNA) and a satellite receiver. The antenna may they may be driven types, in which case external be either a parabolic or spherical type. The LNA am- triggering signals are essential to drive them. plifies the signal from the antenna while the receiver sawtooth current A current that has a sawtooth wave- converts the signal to VHF and modulates it for the form (in horizontal and vertical deflection systems TV set. of TVs). satellite TV modulator In a satellite TV system, that sawtooth generator A relaxation oscillator that pro- part that permits the output to go directly to the duces a sawtooth waveform—for example, horizon- antenna input of a TV receiver. A modulator con- tal or vertical generator in TV receivers. verts the audio and video signals to an RF signal. sawtooth voltage A voltage that has a sawtooth Most satellite receivers have a modulator built in. waveform (in vertical deflection systems of TVs). saticon camera tube (High-band, mixed-field). A tube sawtooth waveform A waveform characterized by a used in broadcast TV and some consumer slow rise time and a sharp fall, resembling the tooth videocameras; constructed from arsenic and tellu- of a saw. rium by Hitachi and RCA. It provides higher resolu- SBCA See Satellite Broadcasting and Communications tion than the vidicon, and has the ability to produce Association. less noise under high illumination, but the saticon is SC 1. Suppressed carrier. 2. SandCastle pulse. more susceptible to image retention or lag. To com- SCA Subsidiary Communication Authority or Authori- pensate for this, different techniques are employed zation, an awkward FCC term for a relatively new in the design of the tube. audio channel. The FCC later changed the nomen- saturated color A pure color, not contaminated by clature to Subsidiary Communication Service (SCS), white. but the broadcasting industry continues to use the saturation 1. In color perception, the degree to which original term. It is the second audio, or subcarrier, the light energy is confined to a narrow frequency channel used for stereo broadcasting and other pur- band. It is thus the converse of the extent to which poses in the US. The signal is multiplexed on the FM the color is diluted with white light. The difference band by a modulator. See also SAP. between pink and red is one of saturation. Also scalable coding Encoding a visual sequence so as to called color saturation. See also Variables of per- enable the decoding of the digital data stream at ceived color. 2. In satellite transponders, a power different spatial and/or temporal resolutions. Typi- level above which an increase in input causes no cally, scalable compression techniques filter the im- further increase in output. The output of the receiver age into separate bands of spatial and/or temporal should drive the transponder to saturation. data. Data reduction techniques are applied to match saturation control Achieved by varying the amount human vision response characteristics. of color information with respect to the luminance scaling The act of changing the effective resolution of information. the image. For example, say we need to display an SAV Start of active video, a synchronizing code word image at a resolution of 640 x 480 as a smaller pic- used in component digital video. ture on the same screen, so that multiple pictures SAW Surface acoustic wave. can be shown simultaneously. We could scale the SAW filter An acoustic wave filter that utilizes the original image down to a resolution of 320 x 240, surface wave of a piezoelectric element of very com- which is one fourth of the original size. Now, four pact design to allow a sharp transition between re- pictures can be shown at the same time. That is an

241 scallop

example of “scaling down.” Scaling up is what oc- safe-action area, which is the central part of the pic- curs when a snapshot is enlarged into an 8" x 10" ture received and seen on the TV set. glossy. There are many different methods for image scanning disk A rotating metal disk that has one or scaling, and some “look” better than others. In gen- more spirals of holes near its circumference. It was eral, though, the better the algorithm “looks,” the used in early mechanical TV systems to break up a harder or more expensive it is to implement. scene into elemental areas at a TV camera or to re- scallop In TV, a wavy picture. construct a scene in a TV receiver. scan To examine an area or a region in space point by scanning line (US: strip) In TV, one of the horizontal point in an ordered sequence, as when converting a rows of elements of which the image is assumed to scene or image to an electrical signal. be composed and which is explored by the scanning scan converter 1. A device that converts one TV stan- beam during transmission and reception. The ele- dard to another. 2. A CRT that is capable of storing ments in each line are scanned in order from left to radar, TV, and data displays for nondestructive read- right with a rapid return to the left to start the next out over prolonged periods of time. Applications line below, and a rapid return to the top of the image include buildup of repetitive signals submerged in when the bottom line has been completed. The mo- noise, conversion of video displays from one scan tion of the scanning beam is, in fact, similar to that of mode to another, and special overlay and merging the eye in reading. The definition of a TV system is effects for TV and radar displays. primarily determined by the number of scanning lines scan line An individual sweep across the face of the chosen and most conventional systems use 525 or display by the electron beam that makes the pic- 625, HDTV 750 progressive or 1125 interlaced. Not ture. An electron beam “scans” the screen to pro- all the lines are reproduced on receivers because a duce the image on the display. It takes 525 of these number are lost during the vertical flyback. scan lines to make up a NTSC TV picture and 625 scanning method The video scanning method can scan lines to make up a PAL TV picture. be either interlaced or progressive. Interlaced scan- scanner The center portion of a three-part video head ning, used in today’s analog TV, fills in the odd-num- drum. The scanner, which contains the video heads, bered lines (1, 3, 5, 7, ... ) and then fills in the rotates against the videotape while the upper and even-numbered lines (2, 4, 6, 8, ... ) until the frame lower parts of the drum remain stationary. See also is complete. Progressive scanning fills in each line Flying-spot scanner. consecutively, as a computer display does. scanning 1. In TV, the process of analyzing or synthe- scanning rate The rate of displacement of the scan- sizing the light content of the elements constituting ning spot along the scanning line. the scene. In practice this is achieved by an electron scanning spot In TV, the small area of the target of a beam which moves over the target of the camera camera tube or screen of a picture tube that is af- tube or the screen of the picture tube in a series of fected by the scanning beam at any instant during lines which embrace every element of the image. 2. the scanning process. In film-to-video transfer, scanning refers to the hori- scanning yoke Syn.: deflecting yoke, deflection yoke, zontal movement of the video camera across the yoke. See Cathode-ray tube. film image projected on a screen. To capture wide- Scan Velocity Modulation See velocity scan modulation. screen films on tape, a blank space would have to SCART Syndicat des Constructeurs d’Appareils Radio appear across the top and bottom of the TV screen. recepteurs et Televiseurs). A 21-pin connector used Therefore, to fill the screen, some of the film image extensively in Europe to connect and interface au- is deleted by scanning. The best possible smaller dio and video components. The SCART connector is image is selected from the wider film image based now the standard component for audio, video and on esthetics, information (which actor is speaking RGB purposes in Europe. The standard version car- at the moment), the avoidance of head chopping ries stereo audio, composite video, S-video, RGB and other cosiderations. A professionally scanned video and blanking signals. The pin signal allocation TV broadcast appears unobtrusive and gives the for the standard SCART connector is listed in Table viewer the feeling that nothing has been removed. 1. There are some differences between the pin allo- However, no matter how carefully the film has been cation on the standard SCART connector and that scanned, there have been voices of criticism from used to connect satellite decoders. those involved in the creative process of filmmaking who believe that the scanning process compromises Table 1. Standard SCART socket connections the artistic integrity of the original wide-screen work. Digital transfer, an alternative to scanning, offers a Pin Specification Signal more sophisticated technique of converting theatri- Number cal films to video. scanning area The part of a picture that the camera 1 Right CH Audio Out 0.5 V actually sees. It is larger than the essential area, or 2 Right CH Audio In 0.5 V

242 SCSA

3 Left CH Audio Out 0.5 V scophony system System of projection TV in which a 4 Audio Ground beam of light is modulated by a Kerr cell and then 5 Blue Ground projected on to a screen after reflection at a rotat- 6 Left CH Audio In 0.5 V ing system of mirrors (known as a mirror screw), 7 Blue In 0.7 V which gives the required scanning pattern. 8 Source Switching Max 12 V scotopic luminosity function The response of the 9 Green Ground eye with normal levels of brightness. The peak of 10 Intercommunication Line the scotopic function occurs at a shorter wavelength, 11 Green In 0.7 V approximately 510 nm. 12 Intercommunication Line Scottie A family of amateur slow-scan TV (SSTV) trans- 13 Red Ground mission modes developed by Eddie Murphy, 14 Intercommunication Line Ground GM3BSC, in Scotland. 15 Red In 0.7 V SCPC Single channel per carrier. 16 Fast RGB Blanking variable SCR Silicon-controlled rectifier. 17 Composite Video Ground scrambled channel A cable or satellite system chan- 18 Fast Blanking Ground nel that is unviewable unless a decoder is used. 19 Composite Video Out 1 V Scrambled channels, of course, are usually premium 20 Composite Video In 1 V channels that require an additional monthly fee from 21 Socket Ground the subscriber who receives a special decoder for unscrambling the channel’s programs. scatterwind The uneven winding of tape, usually re- scrambler A circuit or device that is used in communi- sulting in damage to its edges, which hold the au- cation systems to produce an unintelligible version dio and control tracks. In a videocassette, reel of the signal to be transmitted, in a predetermined spindles control the tape so that it is packed evenly. manner. The received signal is rendered intelligible Scatterwind is usually caused by defective spindles by an unscrambling circuit used at the receiver, in or other similar faulty parts of a cassette. sympathy with the scrambler. scene transition stabilizing Automatic transition scrambling A method of altering the identity of a video editing. or audio signal in order to prevent a reception by Sceptre AT&T. A consumer videotex interactive termi- persons not having authorized decoders. nal introduced in 1983 which, when used with a TV SCR dimmer A silicon-controlled rectifier used in light- set and a phone line, allowed the consumer to in- ing control in TV. teract with a videotex data base service. Withdrawn screen 1. The viewing surface of a CRT. In projection from the market in 1986. TV, the surface upon which the projected image is SC-HDTV system Zenith and AT&T. Spectrum-com- cast. A special aluminum screen gives optimum per- patible HDTV system employing progressive scan- formance. The beaded-type screen is barely accept- ning, digital DCT compression, and four-level able since it scatters the light and the flat matte vestigial sideband modulation. Features of this sys- screen gives a washed-out picture under normal tem were adopted in the final HDTV standard lighting conditions. The surfaces of these screens adopted by the FCC. need special care. To decrease bright spots in the Schlieren Regions in a translucent medium that have picture area and to maximize the reflected light, pro- a different density and index of refraction than the jection TV screens are often curved. 2. Screen grid. rest of the medium. A Schlieren lens is used for video 3. Syn.: shield. Material that is suitably arranged so production. as to prevent or reduce the penetration of an elec- Schmidt optical system An arrangement of lenses and tric or magnetic field into a particular region. 4. See mirrors in combination with a very bright CRT; used Frame. in video projection systems. The first successful screen gain See Brightness, Projection screens. method of producing large screen TV pictures using screen saturation Limitation of the brightness of a a CRT, mirrors and a set of reflectors. Developed in CRT fluorescent screen by the rate at which energy the 1940s, this system was employed at first to in- from the electron beam can be transformed into crease the screen size of small CRT TV sets and was light. Usually accompanied by burning. later used in theaters for special sports events. screen size Normally, the diagonal measurement of a scoop A large bowl-shaped unit—often made of alu- TV screen in inches. A 19" screen measures that dis- minum—into which a lightsource is placed so that tance from one corner to the opposite corner. it will reflect light over a wide area. SCS Subsidiary Communication Service. See SCA. scophony An abortive attempt to eliminate the CRT SCSA Signal Computing System Architecture. An ar- as the display method of large screen TV. Developed chitecture that describes how both hardware and in England in the 1940s, scophony employed a com- software building blocks work together. It focuses posite of electronic and mechanics in its process. on “signal computing” devices, which refers to any

243 SCSI

devices that are required to transmit information over search-tuning A VTR system to select one out of four the telephone network. Information can be trans- tuners, each representing a particular band. mitted via data modems, fax, voice or even video. SECAM Systeme en Couleurs a Memoire. A compat- SCSA defines how all these devices work together. ible color TV system originated in France in which Signal computing systems combine three major ele- the luminance signal is transmitted by amplitude ments for call processing. Network interfaces pro- modulation of the vision carrier and color informa- vide for the input and output of signals transmitted tion is transmitted by frequency modulation of the and switched in telecommunications networks. Digi- vision subcarrier, the two chrominance signals be- tal signal processors and software algorithms trans- ing sent separately on alternate lines. The total band- form the signals through low-level manipulation. width is the same as that of a black and white system Application programs provide computer control of using the same line standards. A line-period delay the processed signals to bring value to the end user. line and an electronic switch are needed at the re- (www.scsa.org) ceiver to ensure use of both chrominance signals on SCSI Small computer systems interface, a popular high- each displayed line. The system is used in France, data-rate, general-purpose parallel interface. and a number of other countries. SD 1. Super density. 2. Standard definition television. SECAM chrominance phase switching The line-by- See SDTV. line and field-by-field variation of initial phase of the SDDI Serial digital data interface. SECAM chrominance signal following the specified SDI Serial Digital [Video] Interface; Serial Digital I/O. pattern (in degrees): from line to line: 0, 0, 180, 0, Another name for the 270 Mbps or 360 Mbps serial 0, 180,… or 0, 0, 0, 180, 0, 0, 0, 180,… ; from field interface defined by BT.656. It is used primarily on to field: 0, 180, 0, 180, … Syn.: chrominance phase professional and studio video equipment. switching; phase inversion; PI sequence. SDL-VCR Standard definition-long VCR. An IEC digital SECAM encoder A device (YCbCr or RGB) to convert video (DV) format standard (525/60, 625/50) for signals into a signal according to the SECAM system. consumer market devices. SECAM-H Modern variant of the SECAM system with- SD-Ready A TV set that can display a 480p-format out vertical color identification signals (“bottles”); standard-definition digital TV signal as well as VGA H stands for horizontal color sync, the bursts of un- and SVGA signals from a computer. modulated chrominance on the line back porch that SDTI Serial data transport interface. are used as a Dr/Db color sequence sync reference. SDTI-CP Serial digital transport interface-content pack- If in any doubt, signals produced in SECAM-V with age. Sony’s method for formatting MPEG IMX (50 “bottles” will always be usable on SECAM-H equip- Mbps, I Frame MPEG-2 streams) for transporting on ment, but not vice versa. This should not be con- a serial digital transport interface. fused with the two different VHS recording methods SDTV Standard Definition TV. SDTV and high defini- for SECAM known as SECAM-L and SECAM-ME. tion TV (HDTV) are the two categories of display SECAM-L 1. Broadcast TV standard used in France. 2. formats for digital television (DTV) transmissions, Common label on multi-standard VHS machines to which are becoming the standard. Both SDTV and denote operation in a VHS tape format unique to HDTV are supported by the Digital Video Broadcast- France whereby frequency-modulated SECAM ing (DVB) and ATSC standards. chrominance is down-converted utilizing frequency SD-VCR Standard definition VCR, an IEC digital video division by a factor of four. The usual chroma pro- format standard (525/60, 625/50) for consumer cessing method in consumer VCRs is heterodyning. market devices. Cassettes recorded on SECAM-L machines will not search-forward (cue), search-reverse (review) In play back in color on any other type of SECAM VCR. order to quickly find a particular segment on the SECAM-M 1. Common label on multi-standard VHS tape during playback, the user can speed up the machines to denote operation in a VHS tape format capstan and reel tables to nine times the normal similar to that used for PAL, hence its common in- speed, either forward or reverse, by pressing Cue or clusion in low-cost multi-standard VCRs. This for- Review buttons. At this time, noise bars will appear mat is in fact used throughout the SECAM world in the picture because of head crossover. This is nor- except in France, where a VHS system commonly mal on some model VHS and Betamax machines. known as SECAM-L, is in use. SECAM-L is actually For example, some show four noise bars in cue and the description of the French Broadcast TV standard. five noise bars in the review mode. 2. Sometimes incorrectly used to describe SECAM- search mode A function employed by VCRs, video cam- H without “bottles” as opposed to SECAM-V. eras or VDPs to locate a desired point in a videotape SECAM-V Older variant of SECAM system where the or disc, in the case of a VDP, for viewing or editing. color identification signal should be present on the These three types of units provide a variety of search nine lines in the vertical blanking interval. If in any modes and procedures. The search mode is some- doubt, signals produced in SECAM-V will always be times referred to as cue/review or cue and review. usable on SECAM-H equipment, but not vice versa.

244 sensor

This should not be confused with the two different self-keyed insert See Overlay. VHS recording methods for SECAM known as self-timer A video camera feature that, when acti- SECAM-L and SECAM-M. vated, delays recording operation for several seconds SECAM switch Sync pulse with period of two lines, so that the camera user can enter the scene. the rising edge of which marks the start of a line semitransparent cathode A photocathode that ex- with positive polarity of the V component in the PAL hibits photoemission from both surfaces in response chrominance signal or the start of a Dr line in Dr/Db to electromagnetic radiation incident on one of the sequence in SECAM chrominance signal. Syn.: 2H; surfaces. This type of photocathode has the advan- 7.8 kHz; Dr/Db switch; PAL switch; PAL switching tage that electron emission occurs on the opposite signal. side to the incident radiation and it is often used in Secondary Audio Program See SAP. TV camera tubes. secondary electron An electron emitted from a ma- sendust Iron/silicon/aluminum alloy. Used as a video terial as a result of secondary emission. head (pole-tip) material. secondary emission The emission of electrons from sensitivity A figure of merit that expresses the ability the surface of a material, usually a metal, as the re- of a circuit or device to respond to an input quan- sult of bombardment by high-velocity electrons or tity. Expressed as divisions per volt or ohms per volt positive ions. for a measuring instrument, as spot displacement secondary-electron multiplier Electron multiplier, per volt of deflection voltage or ampere of deflec- device used in the image-orthicon tube. tion current for a CRT, as output current per unit See SAP. incident radiation density for a camera tube or other Second Audio Program (SAP) signal See Multichan- photoelectric device, and as microvolts of input sig- nel television sound. nal when specifying minimum signal strength to second generation See Generation. which a receiver will respond. The definition of the see-through mode A video camera feature that makes sensitivity of TV imagers of greatest interest to sci- the background image visible through the use of entists is their quantum efficiency, the percent of superposition. incident light quanta that create electron-hole pairs SEG 1. Special effects generator. 2. See Segue. in the photoconductor. For plumbicons and saticons, segment recording One-touch recording. the quantum efficiency is approximately 85% at the segue From the Italian sequire, to follow. The smooth peak of their spectral response curves. Recent im- transition from one sound to another, often by the provements in charge-coupled device (CCD) tech- use of a crossfade. Often shortened to “seg” in ev- nology have increased the sensitivity of CCD images eryday use. Used primarily in TV audio production: to the point that it is comparable to or greater than it characterizes a production technique in which one that of plumbicons and saticons. sound fades out while another fades in. The term is sensitivity range The difference between the least less frequently used to describe visual transitions such and the greatest amount of light to which a video as a change of a mood or scene, usually through a camera responds while still maintaining good pic- dissolve. ture resolution. The sensitivity range of a typical cam- selective fading See Fading. era is 10-10,000 fc. Some cameras feature a selective focus The adjustment of the lens so that a sensitivity switch to increase response to light, but particular object in a scene is in perfect focus. When this often causes the resolution to suffer, resulting a telephoto lens is used, all but that object will be in a noisier picture. A neutral density filter may be out of focus, creating the familiar effect of an ob- attached to the front of the lens to decrease the ject surrounded by blur. sensitivity range. selenicon Specialized camera pick-up tube of vidicon sensitivity switch A video camera feature which per- type using selenium as the active material. Used as mits the electronic increase of the camera’s sensitiv- a luminance tube in some color telecines. ity to light. The switch extends the general self-fill key A luminance key whereby the hole cut is amplification of the video signal so that the camera filled by the video that cut the hole. can produce a picture even in poor light, although self-focused picture tube A TV picture tube that has the image will be noisier. Each camera has its own automatic electrostatic focus incorporated into the sensitivity range. For example, one camera may list design of the electron gun. its range as 5 to 6500 fc. Most video cameras aver- self key Keying mode when the mixer creates a key age about 10-10,000 fc. This range can be decreased signal from the video that will itself eventually fill if desired by adding a neutral density filter to the the hole. A common example is simple insertion of front of the lens. On cameras without a sensitivity captions (generated with a black background) over switch, low light problems are handled by the auto- the desired program output. In this case any lumi- matic gain control (AGC), which otherwise differs nance value above black can be easily detected to in its functions from that of the switch. make a key signal for the captions. Syn.: on-lay. sensor A device for converting sounds or images to

245 Separate Audio Program

electrical signals, such as a microphone or video cam- with 20-bits resolution four-channel audio. In addi- era. Also called transducer. The eye is a sensor, too. tion, integrating the model D-1 component digital Separate Audio Program See SAP. VTR with the D-2 composite equipment becomes separate mesh A mesh screen located in vidicon cam- much simpler, since only one cable is required. eras, which helps control the path of the electron serial digital transport interface (SDTI) SMPTE 305M. beam from cathode to target area, thus improving Allows faster-than-realtime transfers between vari- the scanning process and the resulting picture. ous servers and between acquisition types, disk- separate mesh vidicon Improved form of vidicon based editing systems and servers, with both 270 which contains an extra electrode in the form of a Mbps and 360 Mbps supported. wire mesh. The result is to improve the resolution of serial storage architecture (SSA) A high-speed data the tube. interface used to connect storage devices with sequence A coded video segment that begins with a systems. sequence header followed by one or more groups series peaking The use of a peaking coil and resistor of pictures, and ends with a sequence end code. in series as the load for a video amp to produce sequence edit mode A digital VCR edit feature that peaking at some desired frequency in the passband. can handle several assemble edits automatically. Se- It can compensate for previous loss of gain at the quence edit is usually part of a bevy of edit func- high-frequency end of the passband. tions, including edit start and preview and assemble serrated vertical pulse A vertical sync pulse that is edit. broken up by five notches that extend down to the sequential color television A color TV system in black level of a TV signal. It gives six component which the primary color components of a picture pulses, each lasting about 0.4 line, to keep the hori- are transmitted one after the other. The three basic zontal sweep circuits in step during the vertical sync types are the line-, dot-, and field-sequential color pulse interval. TV systems. It is also called a sequential system. serration pulses Pulses that occur during the vertical sequential interlace TV interlace in which the lines sync interval, at twice the normal horizontal scan of one field fall directly under the corresponding lines rate. These exist to ensure correct 2:1 interlacing (in of the preceding field. early TVs) and eliminate DC offset buildup. sequential scanning Also called progressive scanning. server A computer or device on a network that man- Scanning system in which all the lines composing ages network resources. the image are scanned in succession during each server (video) Storage system that provides audio and vertical downward sweep of the scanning agent. It video storage for a network of clients. Most used in is therefore noninterlaced scanning. professional and broadcast applications are based sequential system Sequential color television. on digital disk storage. In addition to those used for serial One bit at a time, on a single transmission path. video on demand (VOD), other applications include serial attribute A coding system common in videotex transmission, post production, and news. Store sizes and , where the attributes of a char- are large, up to 500 gigabytes or more. acter (e.g., color, size) are represented by a code service area The area that is effectively served by a within the coding scheme, which is transmitted and given radio or TV transmitter, navigation aid, or other stored but not displayed or printed (unless a special type of transmitter. Also called coverage. command is effected). The attribute code precedes servo Short for servo mechanism. An electromechani- the character(s) having the required attribute, and cal device whose mechanical operation (e.g., motor appears on a display or printout as a space. Cf. speed) is constantly being measured and regulated parallel attribute. so that it closely matches or follows an external ref- serial digital Often used informally to refer to serial erence. The servo circuitry of a VCR compares the digital television signals. phase of the 30-PG signal to that of the vertical sync Serial Digital [Video] Interface (SDI) 1. Format in separated from the video input signal in the record which 10-bit serialized video data are transmitted mode so as to control the drum rotation and keep via BNC type connector or fiber-optical connector its phase constant. A signal twice as long as the cycle with clock rate: 10 x 4 x 3.579 = 143 MHz (digital of the VD signal (vertical sync) is fed to the CTL (con- composite NTSC and PAL-M), 10 x 4 x 4.433 = 177 trol) head as the servo reference signal during play- MHz (digital composite PAL), 10 x 27 = 270 MHz back and is recorded onto the tape. (digital component 4:2:2) or 10 x 36 = 360 MHz servo hunting In satellite TV, an oscillatory searching (Rec.601 Part B, digital component). 2. An input/ of the feedhorn probe when use of inadequate output capability built into advanced professional/ gauge control cables results in insufficient voltage industrial VTR machines such as Sony’s D-2 video- at the feedhorn. tape recording system. SDI, a marked improvement set 1. A radio or TV receiver. 2. The decor of a stage over parallel inputs and outputs, can handle signals play or the location of a film, TV, or other produc- with up to 10-bits resolution for the video signal, tion. A set designer or set decorator creates the de-

246 sharpness control

cor of a play, movie, or show. An abstract set has a effects in reproduced images. High-velocity camera neutral background, as on a TV news program. tubes generate such signals and, in the early days of set day Build day for the set. TV, these signals were neutralized by adding to the set-top box (STB) The electronic device that sits on camera output specially generated waveforms at line top of a TV, connecting it to an incoming cable/sat- and field frequencies (known as tilt and bend wave- ellite signal, digital TV signal, or internet functions. forms). Set-tops vary greatly in their complexity, with older shadow mask A perforated metal screen containing models merely translating the frequency received off hundreds of thousands of small apertures and posi- the cable into a frequency suitable for the TV tioned between the neck or yoke of a TV picture receiver while current models are addressable with tube and just before the face or raster of the CRT. a unique identity much like a telephone. Also called Three electron guns, one for each of the primary set-top converter. colors, are stationed at the rear of the tube. When set-top converter In cable TV, a device that hetero- the electrons leave each of the three color guns, they dynes all incoming channels to a single output chan- pass through the shadow mask and affect only the nel, usually channel 3 or 4. Also called set-top box. color of their origin. For example, if a red barn is setup 1. The ratio between reference black level and reproduced, only the electrons from the red elec- reference white level in TV, both measured from tron gun pass through the mask to activate the red blanking level. It is expressed as a percentage. 2. phosphor dots on the face of the picture screen. Setup is the same thing as pedestal. 3. The position The function of the mask, therefore, is to focus the of the camera, microphones and artists at the com- proper electron beam to the correct phosphor color. mencement of a shot or scene. Sony’s fine-pitch picture tube, known as Fine-Pitch setup day Build day. Aperture Grille, was a variation of the shadow mask. setup menu A remote control feature found on some It utilizes a series of unbroken vertical slits or stripes TV sets that displays a set of color diagrams of in- to produce more and tinier pixels. With the addition stallation connections. The menu, designed chiefly of a dark, tinted screen, these TV monitor/receivers for new owners of the unit, includes color-coded offer improved picture definition (as much as 600 jacks, located on the rear of the TV system, that lines of horizontal resolution with direct video in- match the different connections appearing on put) and a higher contrast ratio. screen. Setup menus also provide automatic chan- shadow-mask picture tube RCA-developed standard nel search, allow setting of time displays and permit color picture tube with three electron guns (or a popular channels to be arranged in tuning sequence. single gun firing three beams) in which the screen is setup tape Monitor/receiver reference tape. composed of dots or stripes of red, green and blue SFX Refers to the special effects of a VCR, VDP, video phosphors, a shadow mask near the screen ensur- camera, camcorder, etc. The two main types are con- ing that each beam always strikes the same color ventional and digital special effects. phosphor. In some tubes the phosphor dots are ar- shader 1. A special feature, found chiefly on profes- ranged in groups of three in a triangular pattern sional/industrial workstations, that produces various known as a triad (delta-array color tube) and in oth- textures, such as marble, wood, glass, etc. These ers as vertical stripes (precision-in-line color tube). workstations usually incorporate the use of a com- shaft encoder In VCRs, a sensor module to drive an puter and special software. 2. A nickname for a video electronic tape counter. When the encoder turns, control engineer, who is in charge of video but not an IR LED and sensor detect movement and direc- audio. tion. This information is supplied to the counter shading 1. A variation in brightness over the area of a electronics. reproduced TV picture, caused by spurious signals shake absorber Optical image stabilization system. generated in a TV camera tube during the retrace Used in Canon’s camcorders (UCS5, E700); has a intervals. Those spurious signals are generally due specially designed vari-angle prism. The prism opti- to redistribution of secondary electrons over the cally compensates for hand tremors and external vi- mosaic in a storage-type camera tube, and vary from brations to ensure that perfectly steady video images scene to scene as background illumination changes. are achieved, especially in telephoto situations. 2. Compensation for the spurious signals generated shaky cam Slang for a film or TV segment made by a by a TV camera tube during the flyback interval. hand-held (hence, shaky) camera such as a minicam. shading generator One of the signal generators in a sharpness Image sharpness. TV transmitter that generates waveforms 180 de- sharpness control A feature, found on many TV re- grees out of phase with the undesired shading sig- ceivers, VCRs, monitors, component TV systems, nals produced by a TV camera in order to provide image enhancers and other image processors, that uniform scene brightness. allows the viewer to artificially vary the bandwidth, shading signals In TV, components in the output of a thereby affecting the horizontal resolution. The camera tube which give rise to undesired shading sharpness control can soften as well as bring more

247 shield

detail to a screen image. With some units such as shuttle search The standard method of speeding the component TVs (capable of covering a wider band- videotape back and forth through a VCR to find a width and thereby producing an image of high reso- specific point. More advanced VCRs provide mul- lution), a sharper picture may also mean more tiple speed search in forward and reverse. With older detailed video noise. To minimize this interference, machines, FF and REW do not display any images the sharpness control can be turned down, which on the TV screen, whereas the newer models, with slightly softens the image detail, but also decreases their high-speed search feature, show a picture, al- the unwanted video noise. beit a fast-moving one, on the screen. shield Screen. shuttle speed The rapidity at which a video deck can shift A function of a VCR clock display designed to get from one end of a videotape to the other. The select a programmed instruction. When a particular speed factor, in relation to access time, is consid- button is pressed, another program item will appear ered a limiting component, especially in the editing on-screen ready to be set. For example, when time process. is set on some machines, the shift button is pressed side backlight Kicker. to prepare the clock display for the next entry, which sideband See Carrier wave. may be day of week, date of month, month and sidecar 1. In CATV, a small module attached to the year. Also, the term “shift” applies to a digital TV or converter terminal of the subscriber’s TV set to en- VCR feature that allows the viewer to exchange the able the subscriber to order items such as PPV films. main image and the inset image of the PIP function. 2. Slang for adapter. SHL Studio-headend link, a fixed cable television relay side converting Process that changes the number of service (CARS) station used for transmitting televi- pixels and/or frame rate and/or scanning format used sion program material and related communications to represent an image by interpolating existing pix- from a cable TV studio to the headend of a cable TV els to create new ones at closer spacing or by re- system. moving pixels. shooting ratio The amount of tape recorded as com- side frequency See Carrier wave. pared to the amount of tape actually used in the side lobe A parameter used to describe an antenna’s final, edited program. Expressed as a ratio—3:1 ability to detect off-axis signals. The larger the side means three times as much tape was recorded as lobes, the more noise and interference an antenna eventually comprised the finished program. can detect. shot box An instrument panel attached to or part of a side panels When a standard 4:3 picture is displayed TV camera with control push buttons for zoom or on a widescreen 16:9 aspect ratio television screen, other lens changes. typically with black bars on the side. Used to main- shotgun microphone A microphone with long, acous- tain the original aspect ratio of the source material. tical barrels to narrow its response into a beam See also Letterbox. pointed at the subject. A shotgun microphone SIF 1. Sound intermediate frequency. 2. Standard (or (named for its appearance) is effective in picking up Source) Input Format. This video format was devel- sound from some moderate distance or in noise- oped to allow the storage and transmission of digi- filled situations. It is a supersensitive, unidirectional tal video. The 625/50 SIF format has a resolution of microphone, rejecting most sound emanating from 352 x 288 active pixels and a refresh rate of 25 the sides. Often used in remote TV production, in frames per second. The 525/60 SIF format has a reso- outdoor scenes or large sets. lution of 352 x 240 active pixels and a refresh rate shot/reverse shot In film and TV, the cross-cutting of of 30 frames per second. MPEG-1 allows resolutions alternate direct and reverse shots, as in conversa- up to 4095 x 4095 active pixels; however, there is a tions in which the camera shows one person and “constrained subset” of parameters defined as SIF. then the other. The computer industry, which uses square pixels, has show business Also [colloq.] “show biz.” The the- defined SIF to be 320 x 240 active pixels, with a ater, motion pictures, TV, etc. as a business or refresh rate of whatever the computer is capable of industry. supporting. shrink-wrap The tight cellophane wrapping around a SIGGRAPH The Association of Computing Machinery blank or prerecorded commercial videocassette or (ACM)’s Special Interest Group on Computer Graph- DVD. ics (SIGGRAPH). Internet: www.siggraph.org. shunted black and white A color TV technique in signal Information converted into electrical impulses. which the luminance or black and white signal is There are RF, audio and video signals, all different in shunted around the chrominance modulator or nature. For instance, a video signal is not recorded chrominance demodulator. directly on tape, as is an audio signal. Audio and shutter A device that prevents light from reaching the video signals can be directly fed into audio/video light-sensitive surface of a TV camera except during inputs for better signal reproduction. But on units the desired period of exposure. without these inputs, such as TV sets, these signals

248 signal-to-weighted-noise ratio

must be converted to RF signals, which are accepted the TV signal. That is, the signal plate is the elec- into these conventional receivers. trode of a camera tube from which the output sig- signal amplifier An amp used when the signal com- nal is taken. ing from the antenna must be boosted. This amp is signal processor (SP) A device designed to stabilize, especially useful when the antenna is more than 100 enhance or control the degree of fading of a video feet from the VCR and TV. One type of amp attaches signal. The three major video signal processors are to the antenna mast and is powered by a small ac fade control, a stabilizer and an enhancer. These may adapter connected into the coaxial cable leading to be purchased separately, although some manufac- the VCR. The amp receives DC power through the turers have combined these three functions into one center conductor of the cable. When using such an accessory. However, some of these controls may al- amp, care must be taken to make sure that there ready be built into certain components. Many video are no baluns between the amp and the power cameras have the fade control feature while newer source. Most baluns block DC electricity, which model VCRs have circuitry that overrides anti-piracy would render the amp useless. It is always better signals that destabilize the picture. See also Process- (and usually cheaper) to replace the antenna with a ing amplifier. better model than trying to improve reception by signal splitter An accessory often used to split an adding an amp. input signal from a conventional 75-ohm cable so signal channel per carrier (SCPC) In satellite TV, a that it feeds more than one output. For example, a transmission system that employs a separate carrier two-way splitter is used to split an incoming signal for each channel, as opposed to frequency division from an antenna or VCR to two TV sets. If the wires multiplexing, which combines many channels on a run more than a few feet, an amplifier is sometimes single carrier. added to minimize signal loss, which causes a snowy signal computing Refers to computer telephony, the image. Another type of signal splitter is the VHF/ processing of analog signals for transmission over the UHF splitter in which the VHF signal goes to one worldwide telephone system. The signal computing source while the UHF signal goes to another. model gives nontraditional audio, video, speech, and signal-to-noise ratio (S/N or SNR) In general, the ra- communications technology providers opportunities tio of the power in the wanted signal to that of the to embrace PC channels. The term signal computing noise that tends to interfere with it or mask it. It is picked up steam with the announcement of SCSA usually expressed in dB. The precise way in which (Signal Computing System Architecture) in 1993. the signal and noise are measured depends on the signal generator A professional/industrial multi-sig- nature of the signal and the noise. For example, root- nal-generating instrument designed to produce all mean-square (RMS) measurements are used for the standard video signals used in broadcasting, sound signals and random noise, peak-to-peak mea- cable TV and TV set production. These include color surements for TV signals and impulsive noise. SNR is bar, cross-hatch, flat-field and gray step signals. The a very important parameter of a communications generator helps in the testing of TV receivers, moni- system because system efficiency depends, in the tors, broadcast studios, closed circuit TV studios and final analysis, on the SNR obtainable. Systems differ similar setups. More specifically, the color bar sig- considerably in SNR. For example, amplitude limit- nal, consisting of the standard six color bars, is used ing in FM systems permits a better SNR than AM by TV manufacturers to check the color portions of systems. In systems using pulse code modulation the their sets; the cross-hatch signal aids in aligning con- ability to regenerate clean pulses from received vergence and horizontal and vertical linearity; the pulses that are only marginally above the noise level flat-field signal is used to check color balance; gray makes possible very good SNRs. See also video sig- step helps to check color tracking. nal-to-noise ratio. signaling rate In a digital transmission system, the signal-to-weighted-noise ratio A measure of the maximum number of bits that can be transported significance of noise on an audio or video signal. over a given period of time. The signaling rate is The audibility of noise on sound or the visibility of typically much higher than the average data trans- noise on a TV picture depends on the frequency band fer rate for the system due to software overhead for in which the noise falls. Weighting networks can be network control, packet overhead, etc. constructed so that when they are connected to the signal insertion A circuit for data insertion, analog as output of a system in the absence of signal, and well as digital, which can be used for text display root-mean-square (RMS) meters are connected to systems (e.g., teletext), channel number display, etc. them, the readings of the meters indicate the sub- signal plate The metal plate that backs up the mica jective amplitude of the noise. In the case of audio sheet that contains the mosaic in one type of cath- signals, the signal with which this is compared to ode-ray TV camera tube. The capacitance that ex- find the signal-to-weighted-noise ratio is the nor- ists between this plate and each globule of the mal RMS output signal of the system; in the case of mosaic is acted on by the electron beam to produce video signals, the signal with which it is compared is

249 silence suppression

peak-to-peak amplitude of the video output signal, transition period in the U.S. to protect the public in- usually excluding the sync signals. terest. 3. VCR mode. Selects the video signal coming silence suppression A term used in voice compres- from the built-in tuner (TV programs) and the audio sion for transmission whereby silence in the voice signal coming from the unit that is connected to the conversation is filled with other transmissions — rear panel Audio Input L and R terminals. data, video, imaging, etc. According to AT&T, the simulcast HDTV In the U.S., the FCC requires broad- average voice conversation is 62% quiet and 38% casters to simultaneously broadcast the new high- not quiet (i.e. actual conversation). definition TV (HDTV) signals and the analog NTSC silicon-controlled rectifier Unidirectional , a signals for a period, enabling users to continue to four-layer, three-terminal (anode, cathode, and gate) use their analog TVs. PNPN semiconductor device that is normally an open simultaneous color television A color TV system in switch in both directions. When a pulse is applied which the phosphors for the three primary colors to the gate electrode, anode-to-cathode current is are excited at the same time, not one after another. initiated as in a conventional rectifier. Once turned The shadow-mask color picture tube gives a simul- on, it cannot be turned off by removing the gate taneous display. voltage. But it can be turned off by removing the sine-squared pulse A single unidirectional pulse equal anode voltage or waiting until the waveform across to the square of a sine wave and used for testing in the device passes the zero level. The silicon controlled TV. This signal can be used to determine phase and rectifier is used in the low- and high-voltage regula- gain between the luminance or detail information tor power supply circuits. In some TV chassis a sili- and the chrominance or color information. It is also con controlled rectifier can be used as the horizontal part of the VITS. Such a pulse has a limited spec- output device. trum and the pulse duration can be so chosen that silicon image sensor A solid-state TV camera in which it is well suited for testing TV circuits. It is used in k- a charge-coupled device (CCD) semiconductor chip rating determinations. See Raised-cosine pulse. replaces a vidicon or other camera tube. The image sine-wave scrambling A scrambling method that uses is focused on an array that can consist of 163,840 the addition of a 15.75-kHz (or other frequency) sine pixels, charging each element in proportion to the wave to the video signal. If the negative peak of the light falling on it. The charges are removed from the sine wave corresponds to the positive peak of the elements electronically and passed on to the cam- signal (sync pulse) or vice versa, the sync signal is era output as standard TV signals. suppressed below the peak video level. This “con- silicon imaging device A solid-state industrial TV cam- fuses” the sync separator circuits in the TV set and era that uses CCD technology to form individual they cease to function properly. light-sensitive elements. One version has an array single-channel system An approach to HDTV system of 512x320 elements (a total of 163,840 elements) design conforming to MPEG-2 single-channel com- producing standard 525-line video output within a pressed digital TV standard. At 60 Hz, HDTV signals 3-MHz bandwidth. require about 19 Mbits per second, achieved by simple editing A term used by some manufacturers MPEG-2 and Dolby’s AC-3 compression schemes. to indicate that the VTRs do not have capstan servo This fits into a standard 6-MHz frequency band used or head drum servo editing facilities; an imprecise for analog NTSC over-the-air TV signals—hence, a method of electronic editing, which does not guar- single channel of ultra-high-quality HDTV. However, antee clean edits. this single channel could instead be used for several simple profile MPEG image streams using only I and SDTV signals—a matter of some controversy at this P frames. This profile is less efficient than coding point. See HDTV. with B frames but requires less buffer memory for single conversion block converter A device utilized decoding. by some cable TV systems to transmit midband chan- simulated stereo A process employed on some TV nels so that the picture has a higher frequency than receivers and accessories to give the effect of stereo the sound, a reversal from the normal broadcasting sound. Some frequencies are distributed to the right procedure. This prevents VCRs and TV sets with speaker while others are directed to the left, giving varactor tuners from picking up both of these sig- a fuller sound, although not true stereo, since both nals simultaneously. However, authorized subscrib- speakers are producing the identical sound. The tech- ers to the cable system are able to receive these nique is similar to that used in audio when mono stations. recordings are electronically rechanneled. single-crystal ferrite A video head (core) material: simulcast Simultaneous broadcast. 1. To broadcast si- permeability 300-500; resistivity 100,000 ohm/cm. multaneously by FM and AM radio or by radio and Single-crystal ferrites can be machined or otherwise TV. See also Stereo/TV simulcast. 2. Refers to U.S. tele- shaped more accurately than hot-pressed ferrites, vision stations simultaneously broadcasting DTV and but the crystallographic orientation must be care- NTSC signals. Required toward the end of the DTV fully controlled.

250 skip field recording

single-D A type of ported microphone with reduced Solid-state sensors are particularly suited to making proximity effect. single-sensor cameras. Because the resolution ca- single echo Echo occurs on video signals as it does on pability of solid-state sensors is steadily improving, sound signals, and a single echo is a sample of the single-sensor cameras are also improving. original signal that arrives later than the original does, single sideband The technique of reducing the signal owing to a reflection. It may be reversed in phase. bandwidth by entirely suppressing the frequencies single-frame terminal Frame-stopping terminal. produced by modulation on one side of the carrier, single gun color tube A specially designed TV tube and leaving information to reconstitute the signal. with three separate cathodes, each producing a SIP Single in-line package. green, blue or red electron beam, each contained in sister station Radio or TV stations owned by the same a single control grid. An electrostatic focusing sys- company. tem interacts with all three beams. Each color beam sizing See Character sizing. must pass through a respective channel. The three skew 1. Another term for tension error. Skew is actully channels make up an electrostatic convergence tech- the change of size or shape of the video tracks on nique that functions similarly to the three-gun sys- the tape from the time of recording to the time of tems of conventional TV sets. The most popular playback. This can occur as a result of poor tension application of the single-gun picture tube is Sony’s regulation by the VCR or by ambient conditions that Trinitron system. affect the tape. 2. A term used to describe the ad- single-in-line package (SIP) An electronic component justment necessary to fine tune the feedhorn polar- package with a thin rectangular case and a row of ity detector when scanning between satellites. 3. leads for mounting and connecting projecting from The tape tension between supply reel and first ro- one of its edges. A SIP package saves circuit board tary idler or tape path around head assembly of a space because it is mounted vertically in a row of VTR; skew must be maintained properly or picture holes in the circuit board. instability will result. single-point stereo microphone (S-PSM) A small, skew correction 1. Correction of a skew parallelo- single-unit microphone with two enclosed compo- gram-shaped TV scan to a true rectangle. Skew er- nents, one to pick up sound on the left, the other to ror may be due to off-center placing of a large-screen record sound on its right. Employing electret-type TV projector. 2. The various VHS machines have condensers, these stereo mics provide clear, well- speeds that are referred to as SP, LP and SLP. In the balanced sound although they lack the high specifi- SLP mode and with the proper VHS cassette the play- cations of the more costly studio models. Some ing time is 6 hours. Horizontal sync alignment on manufacturers offer S-PSMs but use a different ap- the tape occurs in the SP and SLP modes, but not in proach. One internal component is aimed forward the LP mode. Thus, when using cue or review on LP while the second is capable of picking up sound on recording, severe skew or picture bending will oc- both its left and right. This is sometimes known as cur at the top portion of the screen. Also, the color MS principle. AFC will malfunction for this same reason. To cor- single-sensor color camera A camera using a sys- rect this, the playback video is delayed by 0.5 H to tem of filtering that splits the incoming light into compensate for skew, and the AFC frequency is spots of colored light appearing side by side on the shifted to maintain color lock. surface of the sensor. When the sensor is scanned skew error A term that describes the differences in in the normal way, the electrical output for each spot the angles or lengths of the diagonal tracks placed in the image consists of three values coming in se- on videotape by two different machines. These dis- quence, representing the R, G, and B values for that crepancies may lead to flagging or bending in the point. Because of the critical relationship required upper portion of a TV picture. If the tracks are slightly between the sensor and the color filter, it is custom- longer, the image tends to pull to the left; if shorter, ary to build the color filter on top of the sensor’s it may pull to the right. storage layer. Electronic circuits are then used to skewing A slanted or zigzag pattern on the TV screen. separate the sequential output from the sensor as it skip-field A very common budget digital video effect is scanned, into the required three separate signals. where the image is merely frozen for a determined This approach is effective if the three spots of color period and then instantly updated at the beginning can be small enough that they do not reduce the of the next period. Live images may sometimes be resolution of the final reproduction. Because that used in-between freezes. Syn.: multi-grab; strobe; requires a threefold increase in the resolution of the stroboscope. sensor used (and that is difficult to come by), single- skip field recording A technique used in video re- sensor cameras often are a compromise with respect cording to reproduce one field twice instead of nor- to resolution. However, they are still the simplest, mally reproducing two fields that compose one lowest cost, and most reliable cameras, and there- frame. A similar technique is employed in playback fore single-sensor color cameras are widely used. with the freeze frame mode in which the heads pick

251 skip memory

up one field twice instead of a frame (consisting of standard speed (for prerecorded tapes), the tapes two fields). they produce may have noise or snow on the screen. skip memory A TV or VCR feature that permits the These machines have heads with a narrower gap viewer to eliminate unused or unwanted channels while the other machines used for playback may during the scanning process so that only desired have heads with a wider gap. Therefore, the wider channels appear. The chief advantage of skip heads are picking up more than the narrow diago- memory is that it removes the static and interfer- nal track laid down by the narrow-gapped heads. ence displayed on screen by inactive channels dur- slaving The operation of making a local synchroniz- ing the selection process. ing pulse generator operate in lock with an incom- skip scan A feature, first introduced by Sony on its ing video signal in both line and field. Beta VCRs, that slows down the FF or REW mode so sleep timer A feature built into some TV sets allowing that the viewer can see a portion of the tape on the them to be programmed to turn off the unit at a screen. Other VCR formats have since adopted the certain time. function. slice A contiguous sequence of macroblocks was first skip search A VCR feature that slows down the vid- designated in MPEG-1. A slice is the basic synchro- eotape in FF or REW mode when it senses an elec- nizing unit for reconstructing image data and typi- tronic index previously placed on the tape cally consists of all the blocks in one horizontal automatically or manually. In addition, skip search picture interval. The sequence may represent only displays the beginning of the scene for several sec- one macroblock up to all macroblocks in a field or onds before continuing on its search. The viewer frame. can activate the Play mode whenever a desired scene sliced VBI data A technique where a vertical blanking is reached. At this point, the VCR returns to the be- interval (VBI) decoder samples the VBI data (such as ginning of that scene and plays it back in its teletext and captioning data), locks to the timing entirety. information, and converts it to binary 0’s and 1’s. sky In TV, an overbright area. Streaks in the sky are DC offsets, amplitude variations, and ghosting must called comet tails. be compensated for by the VBI decoder to accu- A direct broadcast satellite service proposed rately recover the data. in 1990, a joint venture of NBC, Sys- slo-mo Also slomo. Informal. Slowed-down action on tems, ’s News Corp. and Hughes film or videotape; slow motion. Communications. The partnership was dissolved, slope overload See Prediction. but Hughes continued the venture, which became slot mask A color picture tube mask that has vertical DirecTV. slots positioned in front of a screen on which color skycam A production device in which a camera is sus- phosphors are arranged in vertical strips. It is in the pended on wires over an area or . The wires Trinitron and other picture tubes that have in-line are connected to small winches, which are computer- electron guns. It is also called an aperture grille. controlled. By adjusting the wires, the unmanned slot matrix tube See Color picture tube. camera can be made to move and zoom from ground slow motion One of the special effects of a VCR and level to 150 feet at a maximum speed of 20 miles designed to slow down the tape speed to permit a per h. closer look at a scene. Some VCRs provide variable slant range The distance that a signal travels from slow motion, a control which adjusts the rate of slow satellite to a TVRO. motion. At its slowest speed, this feature is difficult slant track The original, now rarely heard, term for to watch, since the movement loses a sense of con- helical scan. tinuity. A speed one half to one quarter that of nor- slave When two devices are coupled together in such mal retains movement and is the most popular range a way that one device is controlled by the other, the of this special effect. The slow motion mode, like controlled device is called the slave, and the con- other special effects, is usually accompanied by video trolling device the master. noise, such as horizontal bars of snow, on many ma- slavelock British term to describe a number of remote chines. The newer digital VCRs have corrected this TV stations running synchronously with a main sta- defect. If VCRs are kept in the slow motion mode tion by means of radiated signals from the main sta- for long periods of time, the video heads or the tape tion, the main station being the master and the may be damaged. remote stations the slaves. slow-scan TV See SSTV. The idea of SSTV was to re- slave VCR In video, that VCR which is used as the duce the bandwidth of a TV signal so that it could recording half of the duplicating process. The play- be transmitted on the MF/HF amateur radio bands. back unit is called the master VCR. The use of the Originally, all SSTV was 8-s black and white frames. wrong slave units may cause problems in prerecorded The received picture appeared on a long-persistance tapes. Some VCRs are optimized for the slowest CRT monitor one line at a time—like a window shade speed. When these machines are used as slaves at being pulled down—and it faded away quickly. The

252 SMPTE 293M

next advance was a digital scan converter that dis- Engineers, a professional organization that sets stan- played the image on a TV monitor. An SSTV scan dards for U.S. television. (www.smpte.org) 2. An converter translates the analog SSTV tones to digi- informal name for a color difference video format tal data (originally 128 pixels per line), and stores that uses a variation of the Y, R-Y, and B-Y signal the data in RAM. The converter then translates the set. digital data back to an analog signal suitable for dis- SMPTE 12M Defines the longitudinal (LTC) and verti- play on a TV monitor. Color SSTV pictures were first cal interval (VITC) timecode for NTSC and PAL video achieved by using digital scan converters with three systems. LTC requires an entire field time to store RAM banks. Color images are now the norm using timecode information, using a separate track. VITC PCs and a radio interface. Software is available for uses one scan line each field during the vertical blank- various formats. SSTV has been accepted for instal- ing interval. lation on board the International Space Station and SMPTE 125M SMPTE document equivalent to ITU-R will be used by ISS crews for image communications BT.656, which defines the standard for a bit parallel with amateur radio operators worldwide. digital interface for 55-line interlaced component slow tracking control A feature on a VCR designed video signals. Defines parameters needed to gener- to improve the image quality produced by the slow ate and distribute component video signals on a motion mode. It is sometimes located only on the parallel interface. remote control panel. The feature, which adjusts tape SMPTE 170M NTSC video specification for the United speed only during slow-motion playback, is also States. See RS-170A and BT.470. known as slow motion tracking control. SMPTE 240M 1920 x 1035 pro-video interlaced stan- SLP Extended play. dard (29.97 or 30 Hz). Covers the analog RGB and SM81 Universal stereo monitor to test stereo TV YPbPr representation. The digital parallel interface systems; Sencore. is defined by SMPTE 260M. The digital serial inter- small-area flicker See Flicker. face is defined by SMPTE 292M. Also defines color Smartpark® GTE’s registered trademark for a fiber- temperature, color space, and gamma as well as optic wired industrial park offering a wide variety of other parameters. voice, data and switching services. SMPTE 244M 768 x 486 pro-video interlaced stan- SMATV Satellite Master Antenna TV. A distribution dard (29.97 Hz). Covers the digital representation system that feeds satellite signals to hotels, apart- (composite NTSC video sampled at 4x Fsc) and the ments, etc. Often associated with pay-per-view. See digital parallel interface. The digital serial interface MATV. is defined by SMPTE 259M. smear 1. An analog artifact where vertical edges in SMPTE 253M Analog RGB video interface specifica- the picture display a spreading to the left or right. tion for pro-video SDTV systems. Typically caused by midfrequency distortions in an SMPTE 259M Pro-video serial digital interface for analog system. 2. A video image which displays SMPTE 244M. blurred objects, especially at their edges and beyond. SMPTE 260M Digital representation and parallel in- Smear is usually the result of insufficient lighting terface for SMPTE 240M video. combined with the idiosyncrasies of the vidicon cam- SMPTE 266M Defines the digital vertical interval era tube. Also known as streaking. 3. The undesir- timecode (DVITC). Also see BT.1366. able blurring of edges in a compressed image, often SMPTE 267M 960 x 480 pro-video interlaced stan- caused by the compression algorithm, which tends dard (29.97 Hz). Covers the digital representation to eliminate the high-frequency portions of an im- and the digital parallel interface. Also see BT.601 age that represent sharp edges. and BT.1302. smearing In TV, blurring of the verticals in a repro- SMPTE 272M Formatting AES/EBU digital audio and duced image. auxiliary data into the digital blanking intervals. Also smectic crystal A type of liquid crystal material. Unlike see BT.1305. the nematic liquid crystal used in LCDs for portable SMPTE 274M 1920 x 1080 pro-video interlaced and computers, calculators and pocket TV sets, smectic progressive standards. Covers the digital represen- liquid crystal is bistable. It remains set as either trans- tation, the analog RGB and YPbPr interfaces, and parent or opaque until it is deliberately changed from the digital parallel interface. The digital serial inter- one state to the other with the application of a volt- face is defined by SMPTE 292M. age across its electrodes. Nematic crystals, on the SMPTE 276M Transmission of AES/EBU digital audio other hand, will relax to their initial state when a and auxiliary data over coaxial cable. sustaining voltage is removed. Smectic liquid crys- SMPTE 291M Ancillary data packet and space format- tals are capable of faster switching. They also have ting for pro-video digital interfaces. Also see BT.1364. higher contrast and lower power consumption than SMPTE 292M 1.485 Gbps pro-video HDTV serial nematic types. interfaces. SMPTE 1. Society of Motion Picture and Television SMPTE 293M 720 x 480 pro-video progressive stan-

253 SMPTE 294M

dards (59.94 Hz). Covers the digital representation, tifying hours, minutes, seconds, and frame number; the analog RGB and YPbPr interfaces, and the digi- one for identifying color phase; one for identifying tal parallel interface. The digital serial interface is dropped frames (108 frames are dropped every hour defined by SMPTE 294M. Also see BT.1358 and to convert 30 frames/s to 29.97 frames/s); 32 for BT.1362. user identification; 16 for sync; and 4 undefined. SMPTE 294M Pro-video serial digital interface for The VITC has an additional 10 bits per block, for a SMPTE 293M. total of 90. The additional bits are used for a redun- SMPTE 296M 1280 x 720 pro-video progressive stan- dancy check and to identify individual fields (rather dards. Covers the digital representation and the ana- than frames). See also Time code. log RGB and YPbPr interfaces. The digital parallel SMPTE [color] bars A test matrix pattern that con- interface uses SMPTE 274M. The digital serial inter- sists of the following (from top to bottom): 67% of face is defined by SMPTE 292M. the field is occupied by 75% color bars with bar SMPTE 299M 24-bit digital audio format for pro-video eight missing (i.e., without Black); next 8% is the HDTV serial interfaces. Also see BT.1365. so-called “New Chroma Set” bars (Blue/Black/Ma- SMPTE 305M Serial data transport interface (SDTI). genta/Black/White); the remaining 25% shows a se- This is a 270 or 360 Mbps serial interface based on quence of –I, White, Q, Black, and the “Black Set” BT.656 that can be used to transfer almost any type signal (version of pluge). of digital data, including MPEG-2 program streams, SMPTE leader See Leader. MPEG-2 transport streams, DV bit streams, etc. You SMPTE RP160 Analog RGB and YPbPr video interface cannot exchange material between devices that use specification for pro-video HDTV systems. different data types. Material that is created in one SMPTE time code A standard for a signal recorded on data type can only be transported to other devices videotape to uniquely identify each frame of the that support the same data type. There are separate video signal. This digital code, laid down on tape, map documents that format each data type into the gives each frame of video a unique and unchanging 305M transport. address (03:38:52:04 would equal 3 h, 38 minutes, SMPTE 308M MPEG-2 4:2:2 profile at high level. 52 s, and 4 frames). It is used for control of editing SMPTE 314M Data structure for DV-based audio, data operations. Also called Time code. and compressed video at 25 and 50 Mbps. Also see SMT See Surface-mount technology. IEC 61834. S/N Signal-to-noise ratio. SMPTE 322M Data stream format for the exchange of snake A cable that combines several cables, as on a DV-based audio, data and compressed video over a stage or in a studio. Serial Data Transport Interface (SDTI or SMPTE snow Random noise or interference appearing in a 305M). picture as white specs and caused by an insufficient SMPTE 344M Defines a 540 Mbps serial digital inter- S/N input ratio to a TV set or monitor. Often result- face for pro-video applications. ing from dirty VCR heads. SMPTE 348M High data-rate serial data transport in- SNG Satellite newsgathering. A rapid news sending- terface (HD-SDTI). This is a 1.485 Gbps serial inter- and-receiving process. SNG became practical in the face based on SMPTE 292M that can be used to 1980s with electronic improvements and less expen- transfer almost any type of digital data, including sive equipment. News events can be covered with MPEG-2 program streams, MPEG-2 transport trucks equipped with satellite uplinks to send the streams, DV bit streams, etc. You cannot exchange information to stations with TVRO dishes. Many TV material between devices that use different data stations purchased satellite news vehicles (sometimes types. Material that is created in one data type can called SNVs or “live eyes”) to transmit breaking news only be transported to other devices that support to their own stations or others in the region or the same data type. There are separate map docu- around the nation. ments that format each data type into the 348M SNR Signal-to-noise ratio. transport. SNV Satellite news vehicle. See SNG. SMPTE/ANSI frame coding A method of structuring Society For Private And Commercial Earth Stations and editing video material. To create a program by (SPACE) An organization devoted to protecting and combining material from several sources, it is im- promoting the rights of home satellite TV owners portant that individual frames in each source be iden- and manufacturers. In 1986 merged with the Direct tified by a unique code so that they can be quickly Broadcast Satellite Association to form the SBCA located and addressed. The SMPTE/ANSI time code (Satellite Broadcasting and Communications was developed for this purpose. It has two formats, Association). the longitudinal time code (LTC) and the vertical in- society leader See Leader. terval time code (VITC). Both have a bit rate of 2400 Society Of Motion Picture and Television Engineers bits/s and thus can be recorded on an audio track. (SMPTE) An organization established for the advance- Each block in the LTC code has 80 bits: 26 for iden- ment of theory and practice related to the produc-

254 sound carrier

tion and utilization of motion pictures and TV pro- transfer device (FFTD), interline transfer device (ITD), grams. The society frequently sets standards in its and frame interline transfer device (FITD). related field. For example, it issues an official color solid-state image sensor Charge-coupled image bar to adjust, test or measure various aspects of a TV sensor. See also Image sensor. picture or individual equipment. (www.smpte.org) solid-state memory Electronic digital memory that soft-edge wipe In film and TV, a wipe (an optical ef- contains no moving parts. In editing, sequences fect between two succeeding shots) in which the marked for placement elsewhere used to be stored border between the two images is blurred or soft- on a separate videotape. When all the necessary ened, such as by shooting out of focus. copying was completed, the editor would assemble Soft RAID A RAID system implemented by low-level the completed, revised tape from the different seg- software in the host system instead of a dedicated ments. Solid-state memory permits the editor to store RAID controller. While saving on hardware, opera- the coded segments in memory, which is then called tion consumes some of the host’s power. See RAID. upon to automatically reassemble the final version software-only video playback A multimedia term. more rapidly and accurately. Video software playback displays a stream of video solid-state TV camera A TV camera based on solid- without any specialized chips or boards. The play- state charge-coupled devices (CCDs) for the image back is done through a software application. The sensor as well as all circuits. Also called solid-state video is usually compressed to minimize the storage camera. space required. Sonet Synchronous optical network, a set of standards A device that uses the photovoltaic effect in for the digital transmission of information over fi- order to convert radiation from the sun directly into ber optics, based on increments of 51 Mbps. It was electrical energy. Solar cells are the most important developed to cost-effectively support broadband long-duration power supply for satellites and space services and multi-vendor internetworking. vehicles. delay line Acoustic delay line. solarization See Posterization. Sony The Japanese firm that started home video. The solar outage The loss of reception that occurs when first home video machine from the company was the sun is positioned directly behind a target satel- the Betamax SL-7200. It used a 1/2" Beta cassette lite. When this occurs, solar noise drowns out the that played in only one speed, Beta I, with a maxi- satellite signal and reception is lost. mum playing time of one hour. It offered no timer solenoid control An electromagnetic circuit system features, no remote control, etc. The second VCR, that uses relays in conjunction with the tape motion the SL-8200, offered two speeds, Beta I and II, for buttons to operate various functions on a VCR. So- 1- or 2-hour playtime. These two machines were lenoid controls offer distinct advantages over older, discontinued with the introduction of the SL-8600, conventional keys, among them (1) the convenience a single-speed, Beta II, with remote pause control, of a light touch to change functions, (2) the ability built-in electronic 24-hour timer and 3-hour record to switch functions without going through the Stop and play capability with the L-750 tape. Later VCRs mode, and (3) quieter operation in contrast to the by Sony featured the slower Beta III speed, electronic clunking piano-type keys previously provided. A ma- tuner, etc. When Beta lost the VCR wars to VHS, chine equipped with solenoid controls, for example, Sony switched to VHS equipment in 1988. Sony also can go from Reverse to FF mode without first going introduced the first portable VCR (SL-3000) in 1978. into the Stop mode. sound The sensation of hearing, produced when sound solid-state Referring to the use of semiconductor tech- waves act on the brain through the auditory organs nology in electronic devices. of the ears. The extreme frequency limits for human solid-state camera A TV camera in which the light- hearing are from about 15 to 20,000 Hz. Also called sensitive target area consists of an array of charge- audio (slang) and sound sensation. coupled devices (CCDs). Exposure to light energy sound balancer Operator who controls the level and results in the generation of electron-hole pairs in quality of TV sound and puts the sound program the semiconductor substrate; the number of elec- together. Also known as sound mixer. tron-hole pairs generated is a function of the light sound bar One of the two or more alternate dark and intensity. The majority carriers migrate into the bulk bright horizontal bars that appear in a TV picture material and the minority carriers accumulate in the when audio frequency voltage reaches the video in- potential wells at the electrodes of the CCDs. The put circuit of the picture tube. accumulated charge is transferred into other sound carrier The TV carrier that is frequency-modu- nonphotosensitive CCD storage sites during the re- lated by the sound portion of a TV program. The trace intervals of the TV display system and is then unmodulated center frequency of the sound car- transferred to the output device while further sig- rier is 4.5, 5.5, or 6.5 MHz higher than the video nals are being generated. Three basic architectures carrier frequency for the same channel. See also for obtaining the video signal are used, a frame/field TV channel assignments.

255 sound channel sound channel The series of stages that handles only sparklies Popular term for impulse noise spikes visible the sound signal in a TV receiver. as black and/or white spots, or streaks in the TV pic- sound mixer Sound balancer. ture, as insufficient signal-to-noise ratio. sound on sound An audio dubbing technique found spatial frequency The number of black and white on some VCRs that permits recording a second line pairs displayed on a screen per degree of visual soundtrack over an existing one without erasing the angle. Spatial frequency is expressed as cycles per original. Conventional audio dubbing automatically degree or as lines per inch for a given viewing erases the previous audio track. Sound on sound distance. can be particularly useful in adding narration to a spatial resolution The number of pixels horizontally scene while keeping the natural sounds of the back- and vertically in a digital image. ground or the music. spatiotemporal analysis The images picked up by a sound on vision A fault condition (due to mistuning TV camera are sampled in space and in time. The or maladjustment) in which the sound signal appears line structure represents sampling in the vertical axis. as a cross-modulation of picture information, or In digital processing, each line is sampled by the causes break-up of the synchronization. At least 40 analog-to-digital converter, thereby producing dB of sound signal rejection is required if sound on samples in the horizontal axis of the image. These vision is to be avoided. In receiver design, therefore, perpendicular sampling processes provide the spa- one or more trap circuits is provided before the video tial analysis. The field and frame repetitions provide IF amp to produce maximum attenuation at the ad- the temporal sampling of the image. The signal con- jacent sound channel frequency and zero attenua- tent of all three dimensions must be exploited by tion at the video carrier frequency. the system designer to take full advantage of the Sound Retrieval System® (SRS) Refers to a TV set channel’s capacity to carry information. This ap- that utilizes electronics to manipulate the audio sig- proach, spatiotemporal analysis, has become an es- nal for the purpose of widening the stereo effect. sential tool in advanced TV system development. Two Introduced by Sony, the Sound Retrieval System pro- of the dimensions are divided into specific intervals: vides a stereo effect through a room without the the vertical distance between the centers of the scan- viewer having to sit between the two basic speak- ning lines and the time occupied by each field scan. ers. This is accomplished by special circuits that first The third dimension, in the analog operation of the blend left and right signals and then create “differ- system, is not so divided since scanning the picture ence” signals. Each set produces distinct spatial and elements is then a continuous process. The intervals sound characteristics before they are once again in the vertical and field-time dimensions result from combined. Ordinarily, TV sets and monitor/receivers sampling of distance and time, respectively. The with stereo and built-in speakers are limited in pro- Nyquist limit applicable to sampled quantities im- ducing stereo separation since the speakers are re- poses limits on their rates of change and these lim- stricted to the width of the TV unit. its must be observed in processing the signals sound sensation Sound. resulting from the repetition of the scanned lines sound wave The traveling wave produced in an elas- and fields. The 3D nature of the video signal requires tic medium by vibrations in the frequency range of that it be represented as a solid figure, known as a sound. See also Acoustic wave. Nyquist volume. The cross-section of this volume is source deck The videotape deck that plays back raw bounded by the maximum frequencies at which the footage in an edit system. vertical and time information may be transmitted, SPACE Society for Private and Commercial Earth Sta- while its long dimension is bounded by the maxi- tions; merged in 1986 with the Direct Broadcast Sat- mum frequency at which the picture elements may ellite Association (DBSA) to form the Satellite be scanned. Study of the volume’s contents thus Broadcasting and Communication Association reveals which frequencies are occupied by a given (SBCA). signal format, where additional signal information space pattern A geometric pattern on a test chart, might be added, the extent of the interference used to measure geometric distortion in TV equip- (“crosstalk”) thereby created, by filtering to reduce ment. or eliminate the crosstalk. The spatiotemporal analy- space wave A radiowave that travels between a trans- sis of signal content has been particularly valuable mitting and a receiving aerial situated above the in the design of the single-channel advanced TV sys- ground, which includes the direct wave and the tems, such as the ACTV-1 system. ground-reflected wave. It is the component of the SPDIF Short for Sony/Philips Digital InterFace. This is a ground wave that does not travel along the surface consumer interface used to transfer digital audio. A of the earth. If the two aerials are placed at a suffi- serial, self-clocking scheme is used, based on a coax cient height above the ground, the surface wave is or fiber interconnect. The audio samples may be 16- negligible and only the space wave needs to be con- 24 bits each. 16 different sampling rates are sup- sidered. ported, with 32, 44.1, and 48 kHz being the most

256 splicing

common. Compressed Dolby Digital and DTS may trial unit designed to measure signal drift, draw low- also be transferred over this interface. IEC 60958 level signals from noise, check signal changes, close now fully defines this interface for consumer and in on the frequency span for closer investigation, professional applications. read amplitude, etc. A highly technical and costly Special Audio Program See SAP. piece of equipment. special bits See Time code word. spectrum-compatible HDTV system See SC-HDTV. special effects 1. Refers to the various features on spectrum locus The locus of points representing the virtually all VCRs, with the top-of-the-line models chromaticities of spectrally pure stimuli in a chro- providing the most sophisticated. By changing the maticity diagram. speed of the tape, a variety of special effects are speech recognition A voice-controlled method de- possible. Visual scan permits skipping over unwanted signed to turn the power on and off, change chan- portions of recorded material. Slow motion provides nels, switch modes and perform other similar the viewer with the opportunity to study a particu- functions on VCRs, TV sets and related units. lar segment of a tape with greater scrutiny. Freeze speed control A control that changes the speed of a frame locks in a single picture so that the image motor or other drive mechanism, as for a VCR or appears as though it were a slide. Double-speed play magnetic-tape recorder. allows viewing material at twice the normal speed speed selector switch A feature on most VCRs that but with intelligible sound. Frame advance moves permits the choice of a tape speed mode for record- the recorded information along at one frame at a ing. The Play mode usually operates automatically time. Not all effects work in all speed modes. Some through electronic circuitry that selects the proper VCRs offer several features in slow speed while other playing speed. VHS machines usually feature three models provide the same effects in more than one speeds, SP, LP and SLP (or EP). However, on some speed mode. 2. A video manipulation technique VHS models the LP mode functions only as a play- used to enhance or smooth a transition between back feature, since these machines optimize the camera shots or to create an usual appearance. Typi- video head gaps for either the SP or the SLP speeds. cal transition effects are wipes, fades, or dissolves. spherical aberration An image defect caused by the special effects editing A general term applied to a spherical form of an optical or electron lens or mir- group of video camera features designed to enhance ror, resulting in blurred focus and image distortion. the editing process. For example, wipe, fade, a char- spherical antenna 1. An antenna that has the shape acter generator for titling and date/time insert are of a sphere, used chiefly in theoretical studies. 2. An some of special effects editing functions that can almost flat, rigidly mounted antenna dish used in be used with the camera in the field. satellite TV systems. Because of its shape, it can pick special effects generator (SEG) A unit used in video up more than one satellite without being moved. production to mix, switch, and otherwise process Instead, one or more feed horns designed to collect various video signals to create a final signal known signals are placed in front of the antenna and moved as the program signal. The SEG is usually combined accordingly. with a switcher/fader, which permits connecting two spherical faceplate A TV picture tube faceplate that video cameras to one sync source. is a portion of a spherical surface. specific lighting Lighting used to illuminate an object spider box A small, portable receptacle for several in order to create a desired effect on the display electrical outlets, such as for lighting units; also screen; any lighting units that are set up especially called (in the case of two connectors) junction box. for recording an event. It is commonly used in the film, theater, TV, and spectral response Spectral sensitivity characteristic. exhibitions. spectral sensitivity characteristic The relation be- spike suppressor A device designed to filter electrical tween the radiant sensitivity and the wavelength of lines to prevent fluctuations or “spikes” in the cur- the incident radiation of a camera tube or photo- rent. These variations may result in motor speed dis- tube, under specified conditions of irradiation. It is crepancies as well as picture breakup. also called spectral response. spin A special case of the rotation effect that causes spectral space The measurement between frequen- the displayed picture to appear as spinning (in the cies of a signal. For instance, a VHS VCR produces a screen plane) around the Z-axis (perpendicular to brightness signal on tape, occupying 1 MHz of spec- the screen plane). tral space between 3.4 and 4.4 MHz. On the other spinwheel In digital video, it describes a single co- hand, S-VHS machines provide more picture detail ordinate control used for changing effects param- as a result of increased spectral space. The bright- eters in the Z-axis (perpendicular to the screen plane). ness signal recorded on tape with the V-VHS format Syn.: Z-wheel. extends to 1.6 MHz—the difference between 5.4 splice Tape splice. and 7 MHz. splicing The physical cutting and rejoining of record- spectrum analyzer mainframe A professional/indus- ing tape; the joint of the two ends of the video or

257 split frame

audio tape is secured by tape coated with an adhe- spot size The cross-section of an electron beam at the sive substance on the side. screen of a CRT. split frame See Split screen. spot wobble A technique used in black and white TV split image See Split screen. receivers to make the line structure of the displayed split screen Also called split frame, split image. A tech- image less obvious by superimposing a vertical os- nique in video permitting the viewer to watch two cillation of very small amplitude on the scanning spot images simultaneously. Used primarily in sports and of an oscillator working at a frequency well above news programs, in the past the split screen has been the video band. controlled by the studio or station, not the viewer. How- sprite In computer graphics and video games, a mov- ever, this situation has changed with the development able object or figure on a video screen. 2. In MPEG- of picture-in-picture on TVs. See Multivision, PIP. 4, static background scenes. A coordinate system is split sync scrambling A video scrambling technique, provided to locate objects in relation to each other usually used with either horizontal blanking inver- and the sprites. sion, active video inversion, or both. In split sync, SP speed The fastest speed on three-speed VHS-for- the horizontal sync pulse is “split,” with the second mat VCRs. With a basic T-120 videocassette, stan- half of the pulse at +100 IRE instead of the standard dard play speed can record and play back for two -40 IRE. Depending on the scrambling mode, either hours. SP has several advantages over the other two the entire horizontal blanking interval is inverted speeds of the VHS format. It provides less video noise about the +30 IRE axis, the active video is inverted than the LP (4-hour) and SLP (6-hour) modes. Cop- about the +30 IRE axis, both are inverted, or neither ies made from tapes recorded in SP offer better pic- is inverted. By splitting the horizontal sync pulse, a ture resolution. All VCRs are equipped with this reference of both -40 IRE and +100 IRE is available speed, whereas some machines may not have the to the descrambler. Since a portion of the horizon- LP or SLP mode. Finally, when a tape recorded in SP tal sync is still at -40 IRE, some sync separators may is played on machines by other manufacturers, fewer still lock on the shortened horizontal sync pulses. tracking and other related problems arise. SP is stan- However, the timing circuits that look for color burst dard for industrial and professional VHS equipment. a fixed interval after the beginning of horizontal sync This speed is recognized as the mode that provides may be confused. In addition, if the active video is the best audio and video reproduction in the VHS inverted, some video information may fall below 0 format and is used almost universally by the prere- IRE, possibly confusing sync detector circuits. The corded tape industry. burst is always present at the correct frequency and spurious shading An unwanted signal that gives the timing; however, the phase is shifted 180 degrees effect of brightness changes over the line or frame when the horizontal blanking interval is inverted. period of the TV picture. The term is usually reserved splitter Signal splitter. for the description of signals generated in the cam- spool A cylinder or roller on which tape, wire, or other era tube, although it is sometimes used to describe material is wound. spurious signals due to poor frequency response of sports mode In camcorders, a mode to capture high- amps. speed action. Shooting situations: outdoor sport spurious signal An unwanted signal generated in the scenes such as football, tennis, golf or skiing; a land- equipment itself, such as spurious radiation or un- scape from a moving car. desired shading signals generated in a TV camera spot 1. In CRTs, the small area of luminescence on the tube. screen where the electron beam strikes it. Efforts Sputnik The world’s first artificial satellite. It was are made in the design of CRTs and associated cir- launched by the Russians on October 4, 1957. cuitry to keep the spot area as small as possible in squaerial A flat diamond-shaped aerial for receiving order to improve the definition of the display. 2. A satellite TV broadcasts. This form of aerial (its name commercial announcement of short duration, in- is a blend of square and aerial) is compact in size serted in programs or broadcast between programs. and contains an array of small antennae set on a spot beam A radio-frequency beam from a satellite flat surface. It can be fixed to the wall of a house. that has a narrow aperture angle to cover a rela- square pixels Pixels having the same horizontal and tively small geographic area. vertical sampling grid. There is some evidence that spotbeam satellite See Satellite focus. a large mismatch between horizontal and vertical spotlight A lighting unit whose light can be focused resolution prevents the higher resolution from be- into a beam and directed at a particular object or ing fully perceived by the human visual system. part of the scene. squeeze In TV, slang for a visual inserted in a window spot-optimizer magnet A permanent magnet that or on the screen, generally to the right of a news- resembles that of an ion trap, placed on the neck of caster to identify the subject of a news report. It is some color picture tubes to provide an adjustment more commonly called a topic box. Also called a for optimum picture detail. box, frame, theme identifier.

258 standard focusing

SRAM Static RAM, a type of computer memory that nant circuits to particular frequencies within the pass- behaves in general like dynamic RAM (DRAM) ex- band. This technique is used in the IF amps of TV cept that static RAMs retain data in a six-transistor sets and in multicavity in TV transmitters. cell needing only power to operate (DRAMs require staircase composite test signal, NTSC The test sig- clocks as well). Because of this, current available nal, a component of the vertical interval timing se- capacity is 4 Mbits—lower than DRAM—and costs quence, that is usually transmitted on both fields of are higher, but speed is greater. line 18 in the vertical blanking interval. It has a num- SRP board, VCR System control, DC power supply, ber of components. The first square wave is called and pause control circuits. the line bar, window test signal or white flag at 100 SS In VCRs, Slow and Still picture modes. IRE. Any tilting of the top portion indicates poor low- SSAVI™ Sync Suppression And Active Video Inversion, frequency response visible as picture streaking. The scrambling/descrambling system using a dynamic spike which follows, the sine squared pulse or 2-T scrambling algorithm trademarked by Zenith. This signal, is a good indicator of phase distortion. The system has four modes of operation: (1) Suppressed next wider pulse is referred to the chrominance pulse sync and inverted video; (2) Suppressed sync and test signal and provides an accurate method to de- normal video; (3) Normal sync and inverted video; termine gain and delay difference between the (4) Unscrambled operation. chroma and luminance signals. The final staircase SSC Super sandcastle. Three-level pulse used in older waveform can be used to measure the amounts of TV sets. differential gain, or variations in gain across the fre- SSO Single-system operator. A CATV company with quency spectrum. only one system; not an MSO, or multi-station staircase signal In video, a test signal incorporating operator. several steps at increasing luminance levels. The sub- SST Single-sideband transmission. carrier frequency normally amplitude-modulates the SSTV Slow-scan TV used in amateur radio. Sending staircase waveform, which helps to check the am- still images by means of audio tones on the MF/HF plitude and phase linearities in video systems. The bands using transmission times of a few seconds to staircase signal is one of the many test patterns pro- a few minutes. duced by such components as the video test stabamp Stabilizing amplifier. A video amp designed generator. to remove transient disturbances and bring a TV sig- stair-stepping Professional jargon for spatial aliasing nal into a standard condition suitable for transmis- on near-horizontal lines in a TV picture. Caused by sion or recording. Applications are at the termination lack of prefiltering. Syn.: jaggies. In addition, of a cable or link circuit and following vision-switch- stairstepping applies to lines drawn at angles other ing equipment. Controls, manual or automatic, typi- than 45 degrees that appear on raster (picture-tube cally include picture amplitude, sync pulse amplitude, face) displays. peak , clamping and set-up. stairstep linearity The ability of a VCR to accurately stabilizer Image stabilizer. reproduce the shades of grade between black and stabilizing mesh (US: barrier grid) The mesh situated white. near the target of a low-velocity TV camera tube stand-alone An early CATV term that described cable and biased positively with respect to it to prevent systems that were not part of any cable network. instability of the target potential by effectively limit- While the systems carried local and distant signals, ing the maximum potential that it can develop. For they secured videotapes directly from distributor and small light inputs to the camera, the mesh collects other program suppliers, often via a bicycling the secondary electrons emitted from the target with method, and ran their own pay (premium) cable ser- the result that the target develops a positive charge vices. Lower-cost TVRO dishes made interconnec- image. If, however, any area of the target tends to tion via satellite feasible, and by the early 1980s become more positive than the mesh potential, then nearly all stand-alone operations had been replaced the electric field between mesh and target returns by the programming services from satellite cable the secondary electrons to the target until the tar- networks. get potential equals the mesh potential. Thus, no stand-alone service TV programming provided by in- area of the target can develop a potential exceed- dividual videotapes rather than transmitted via sat- ing that of the mesh. ellite or cable. stage plug An electric connector that can handle Standard-Definition Television (SDTV) A subset of more power than a conventional plug, used in film, the digital TV (DTV) standard that includes DTV sig- stage, and TV for distributing electricity to lighting nals with picture quality at least as good as that of equipment. conventional analog TV. Typical SDTV resolutions are stagger-through A first TV rehearsal with cameras. defined by ATSC and DVB to be 704 x 480 or 720 x stagger tuning The process of obtaining a level re- 576 interlaced. sponse over a desired bandwidth by tuning the reso- standard focusing Optical nomenclature used to de-

259 standard-grade videotape

scribe a lens that can be focused by moving a sec- Starsight® A national electronic television guide sub- tion of the other barrel of the lens backward or for- scriber service. It allows you to sort the guide by ward until the image passing through the lens is your order of preference and delete stations you shown in sharp detail on the image plane. never watch. standard-grade videotape The basic tape that many start/stop In camcorders, a button to start/stop re- VCR owners use for time-shifting, copying or other cording. uses. Manufacturers usually recommend their higher- static Static electrical charges; random noise or grade tapes for preserving more important mate- specks on a TV screen produced by atmospheric rial. The term “standard grade” has a specific disturbance. meaning, whereas other grades of tape, such as high static convergence Convergence of the three elec- grade and super high grade, tend to be more nebu- tron beams at an opening in the center of the lous. However, many professionals in the video field shadow mask in a color picture tube. This is called have narrowed down all these terms to four basic static convergence because the beams must meet types of videotype: standard grade, high grade, Hi- at this point when there are no scanning forces. Fi or stereo, and professional grade. static focus The focus of the undeflected electron standardized time code See Time code. beam in a CRT. standard (minimum) signal The peak-to-peak volt- static matte insert Inlay. age of a signal whose amplitude is sufficient for its station 1. A location where TV or other electronic use within a system. equipment is installed. 2. Broadcast station. standards converter A professional/industrial unit de- station timing Refers to a synchronizing pulse gen- signed to adapt one video or broadcast standard to erator that is used by TV stations to lock together another. The basic converter can usually handle different picture sources both at field and line fre- NTSC, PAL, PAL-M, SECAM and other standards. quencies. This makes it possible for cuts and mixes Some models offer other features as well, such as a between these sources to be carried out without built-in proc amp, noise reduction, automatic input disturbance of synchronization at the receiving end, selection and image enhancement. thus avoiding picture roll-over and other undesir- standard-TV specifications In 1995, the Technical able effects. Sub-Group of the ACATS—advisor to the FCC—ac- statistical coding In video compression, a coding tech- cepted video scanning parameters that were recom- nique that makes use of the fact that all pixel values mended by its Expert Group on Scanning Formats are not equally probable. Shorter words are used to and Compression. These parameters are to be used define the more frequently encountered values, with for Standard-Definition TV (SDTV) transmission a reduction in the total number of bits. This tech- within a digital HDTV broadcast system. The HDTV nique requires the transmission of a code such as system was developed by the Grand Alliance, the the Huffman code so that the length of each byte combination of the four joint-venture contestants can be identified at the receiving end. whose proposed systems were tested in 1992 with- statistical multiplexing A technique for Increasing out any one system emerging a clear winner over the overall efficiency of a multichannel digital tele- the others. The SDTV scanning parameters are: 480 vision transmission multiplex by varying the bit-rate lines by 704 pixels; aspect ratios 4:3 and 16:9; pic- of each of its channels to take only that share of the ture rates 60 per s (interlaced) and 24, 30 and 60 total multiplex bit-rate it needs at any one time. The (progressive). (Also 60/1.001, 24/1.001, 30/1.001 for com- share apportioned to each channel is predicted sta- patibility with NTSC refresh rates.) Also: 480 lines tistically with reference to its current and recent-past by 640 pixels; aspect ratio 4:3; picture rates the same demands. as above. The Technical Sub-Group also accepted step picture A videodisc or VCR feature that permits the recommendation to eliminate all of the 360- (the the viewer to display one video frame at a time. broadcast industry) and 240-line (the TV manufac- “Stepping,” which works only with CAV discs, can turing industry) progressive-scanning schemes that operate in both forward and reverse. Some VCRs had earlier been considered for inclusion. In 1996, permit bi-directional stepping at various speeds, in- the U.S. FCC adopted the major elements of the cluding sound. ATSC DTV standard, mandating its use for digital steps Term used to describe the number of controls terrestrial TV broadcasts in the U.S. The FCC did not on a colorizer; the control for each color is called a mandate use of the specific HDTV and SDTV video step. formats contained in the ATSC standard, but these stereo Refers simply to the use of two separate audio have since been uniformly adopted on a voluntary channels, one left and one right. A stereo system basis by broadcasters and receiver manufacturers. built into a VCR or camera does not necessarily mean DVB set the other world-wide standards for SDTV, that the unit is capable of producing hi-fi, which including additional resolutions of 576 lines by 720 implies other parameters and standards, such as of- pixels and picture rates of 50 per s. See SDTV. fering frequency response over the entire audible

260 stereo TV

range and producing a quiet background free from or three dimensions. Used in 3D TV systems to tape hiss. watch two images of the same scene as a single stereo adaptable Means that the VCR can be con- 3D picture. nected to a decoder that includes the circuitry nec- stereoscopic A reference to a 3D visual image. essary to receive and process the stereo sound. stereoscopic perception The perception of a 3D-im- Without the box, the TV processes monaural sound age to a human observer by displaying a number of only. A VCR that is stereo adaptable has an MPX, or 2D-images. multiplex, jack for connection to the decoder. stereoscopic image See Three-dimensional picture stereo audio output The jacks on some DVD players, image. VCRs and TV monitor/receivers that are used to con- stereoscopic television TV that imparts a 3D appear- nect cables to the left- and right-channel audio in- ance to viewed images. puts of an external stereo amplifier. This connection stereo separation The ratio of the electric signal in produces stereo sound through an external stereo the right stereo channel to the signal in the left ste- hi-fi system. reo channel when only a right signal is transmitted, stereo decoder An accessory unit designed to bring or vice versa. The greater this ratio, which is mea- MTS (multichannel TV sound) stereo to monaural sured in dB, the better the stereo effect. TV sets or VCRs. A relatively inexpensive way of cap- stereo simulator Circuitry using simulated stereo. turing MTS stereo broadcasts with mono units, ste- stereo synthesis The presentation of a stereo effect reo decoders may be used with self-powered by artificial methods. There are various means of pro- speakers or a home stereo system. These units usu- ducing stereo. One of these processes, for example, ally have dual stereo audio line outputs for playing transmits many of the low sounds to one channel back a program through a stereo system while while much of the high frequency is directed to a recording on a stereo VCR. second. A truer stereo effect may be achieved by stereo pilot A component of the MTS (multichannel utilizing a “phasing” process that directs related TV sound) signal that deviates the aural carrier 5 sounds to a particular speaker. The most advanced kHz and is used in the TV receiver to detect the L-R technique, however, separates the audio signal into stereo subchannel. Generated at 15.734 kHz. multiple frequency bands, sending different seg- stereo-ready 1. It means that the VCR has an MTS ments of each band into each of the speakers. The (multichannel TV sound) tuner built into it, so that last two of the above processes are more sophisti- without extra circuitry, the deck can receive and pro- cated than the first but tend to exhibit problems cess programs broadcast in stereo. 2. Refers to a with certain instruments “drifting” from one side VCR that can record in stereo and one that has a to the other. Several accessories, under names such jack to connect to an external stereo-TV decoder. as stereo simulator and stereo synthesizer, are avail- The term “stereo-ready” may be misleading since it able for use with VCRs and TV sets. Some of these does ensure that the VCR is prepared to receive ste- devices have controls which compensate for instru- reo TV broadcasts. For a VCR to receive and decode ment drift or movement. stereo TV sound, the unit often displays either the stereo TV A TV receiver capable of reproducing two abbreviation MTS or BTSC (Broadcast TV Sound audio channels, usually through the use of its spe- Committee). cial tuner or tuners, and playing the discrete chan- stereo-ready camera A video camera capable of pro- nels through dual speakers. Since manufacturers of ducing stereophonic videotapes by means of two TV sets as well as TV broadcasting companies em- microphone inputs. This does away with the need phasized the picture half of TV over the sound por- to connect two microphones to the stereo VCR. Dif- tion, the potential of audio remained a low priority ferent connections are required to obtain stereo with for decades. Motorola in 1958 developed a stereo conventional video cameras. An AC adapter is nec- TV broadcast system but with very limited frequency essary when using a one-microphone video camera response. Its narrow-band FM frequency proved that with a table-model stereo VCR. The camera is con- the main obstructions to stereo TV in the US were nected to the adapter, which is then hooked up to the limitations of audio and telephone transmission. the recorder’s video input. By connecting two mics The 1960s witnessed stereo of concerts to the mic inputs of the stereo machine, all is ready using one channel via TV and the other over an FM for stereo recording. In some cases, the stereo VCR monaural station. In the 1970s two events moved has a built-in camera jack, thereby eliminating the stereo TV closer to reality. First, the Japanese domi- need for an AC adapter. nated TV set production and studio equipment with stereoscope An instrument with two eyepieces their sophisticated audio technology. Second, the through which a pair of photographs of the same technique of duplexing, or carrying two audio chan- scene or subject, taken at slightly different angles, nels on video circuits, made quality stereo transmis- are viewed side by side: the two photographs are sion feasible. On multichannel TV sound (MTS) in seen as a single picture apparently having depth, the U.S., one channel provides stereo sound using

261 stereo/TV simulcast

left/right channel difference signals relative to trans- adheres to the drum. 3. Surface friction, as between mitted mono audio track. parts of a TV camera or other mechanisms. stereo/TV simulcast Outstanding musical programs still adjustment control A control knob found on on TV, such as concerts and operas, are often broad- some VCRs designed to stabilize an image that has cast at the same time in stereo sound by an FM ra- been locked in by pressing the Pause mode. This dio station. These dual broadcasts are called stereo/ control usually is used only if the on-screen picture TV simulcasts. wiggles. stereo VCR A VCR capable of recording and playing still field Freeze field. back two discrete audio channels. Stereo was first still frame Freeze frame. introduced into VCRs by Akai in 1981 in its portable still mode See Freeze frame, Pause. model 7350. JVC followed its VHS competitor with still store A device that converts an image from ana- its own stereo VCR in 1982. To obtain stereo, the log format to digital and holds the image until it is longitudinal audio track on a videotape is divided needed for editing, etc. Used in professional/indus- into two parts, one for each channel. Because the trial processing, still store images are often used as regular mono sound of VCRs is only adequate due backgrounds while foreground images are then to the slow tape speeds inherent in the video pro- placed over the former to produce composites. The cess, an even poorer signal-to-noise ratio results results, after going through a variety of changes, when prerecorded tapes are played back on the including color-correcting, appear as one image. smaller audio tracks of stereo VCRs. VHS machines still video camera A camera that takes individual therefore incorporate a noise reduction system such images or pictures on an electronic disc rather than as Dolby B to help compensate for this. Marantz on film. The forerunner of present-day digital cam- was first with a Beta stereo recorder. Sony soon fol- eras, it was introduced by Sony in 1980. The Mavica lowed with its own unique stereo process called Beta (MAgnetic VIdeo CAmera) was a revolutionary in- Hi-Fi. Instead of using conventional stereo tape heads novation employing a miniature video floppy disc, which produce longitudinal tracks, Sony first FM- but the images were only 640 x 480 resolution, much modulates the audio signal, combines it with the lower quality than film. Digital technology has over- video and finally the video heads place the audio taken analog still video imaging. signal on the tape. The FM modulation retains the still video floppy disk The medium used in still video audio quality and the use of the video heads sharply cameras. The video floppy, or VF, as it sometimes increases the dynamic range. In VDPs the laser for- referred to, contains a coating of metal particles, is mats sold by Magnavox and Pioneer were the first slightly less than 2" in diameter and enclosed in a to offer stereo, with RCA’s CED format following in sealed hard plastic cartridge that measures 2.4" x 1982. 2.1" x 0.14". The VF can record 25 video frames of STG2000 See NV1. full resolution or 50 fields (half-resolution). sticking An effect in a TV camera tube that has been still video printer A machine that makes a photo- subjected to a stationary optical image for a long graphic print from a still video floppy disc. Designed period whereby the tube continues to give a picture to accompany still video cameras, these devices pro- signal of the image after the image has been re- vide a way in which the images from a still video moved. In image orthicon tubes, the effect occurs camera that are normally seen only on a TV set can immediately after switching on because the target also be turned into a physical print. See Kodak still- resistance is too high and the charge image persists picture process, Still video camera. longer than in normal operation. still video recorder/player An electronic unit that sticking potential See Cathode-ray tube. can record, play back and store in memory video stiction 1. Static friction. Friction that tends to pre- signals from several video sources. These include still vent relative motion between two movable parts at video images, video camera frames, images from their null position. It is often seen in moving-coil video scanners and computer graphics. The unit, meters. 2. VCRs that have logged many hours of which uses a 2" floppy disk with rapid random ac- use might begin to exhibit a condition described as cess and is similar to a VCR in appearance, is de- stiction. The word, a combination of the words stick- signed for professional use in broadcasting, video ing and friction, indicates a condition of the video productions, trade shows, etc. head drum assembly that causes the tape to stop stimulus A signal that affects the controlled variable moving during record or playback. If this occurs, in a control system. severe clogging of the video heads and tape dam- STL Studio transmitter link. age could result. The apparent cause of stiction is STN Supertwisted nematic. the loss of an air “cushion” between the tape and (The) Stockholm Agreement, (1961) The “Regional the record drum head. As the VCR is used, friction Agreement for the European Broadcasting Area Con- from tape travel polishes the drum surface smooth. cerning the Use of Frequencies by the Broadcasting This prevents the required air buildup, and the tape Service in the VHF and UHF Bands” adopted by the

262 subcarrier drive

European VHF/UHF Broadcasting Conference stripe filter A chrominance tube system in which the (Stockholm, 1961). target area of the tube is divided into sequential stop Also f-stop. The aperture or useful opening of a stripes for R,G,B and Y, and can therefore derive a lens, usually adjustable by a diaphragm. color signal by using only one pickup tube. stop action A still or freeze-frame technique that was strobe 1. In digital TVs, a mode to display eight time- adapted from motion picture film production to the sequenced still pictures at once, while showing the TV medium. It is used in televised football games, in real-time picture in the lower corner of the screen. which a playback of the action is stopped at a given The editing mode allows the user to change the point. still pictures displayed in the strobe mode. 2. A stop down To close down a lens; to adjust the iris/ very common budget digital video effect where the aperture of the lens so that less light passes through image is merely frozen for a determined period and the lens. A lens set at f2 which is then adjusted to then instantly updated at the beginning of the f4.5 is said to be stopped down two steps; to stop a next period. Live images may sometimes be used lens down all the way is to set it at its highest f-stop in-between freezes. Syn.: multi-grab; skip-field; number. Contrasted with open up. stroboscope. storage camera tube A camera tube in which a charge strobe display A digital VCR feature that unfolds a image corresponding to the optical image input quick sequence of still images in electronic slow mo- grows in magnitude on the target until neutralized tion rather than continuous motion. The audio track by the scanning beam. This occurs in all the camera continues in real time while strobe display is on. tubes, such as the iconoscope, image iconoscope, Some VCRs can adjust the strobe display rate to orthicon, image orthicon and vidicon, which have present from 1.5 to 8 fr/s. Because of the digital been successfully used in TV. Storage occurs by vir- process built into these units, the images contain tue of the capacitance of the target and it brings no noise bars or other video interferences. When in about a considerable increase in the sensitivity of strobe mode, the VCR records one frame at a time the tube. In fact it was not until the advantage of and stores the frames in digital memory for predeter- the storage principle was appreciated that tubes sen- mined lengths of time prior to capturing more frames. sitive enough for use in TV became possible. See stroboscope See Strobe. also CCD. studio A room in which TV or radio programs are store and forward In communications systems, when produced. a message is transmitted to some intermediate re- studio camera Normal camera system made up of lay point and stored temporarily. Later the message two separate units: the camera head and the cam- is sent the rest of the way. Useful for transmission of era control unit (CCU). The camera head actually slow scan TV. changes the light images into electrical signals. The streaking A TV picture condition indicated by white CCU allows the engineer to make adjustments and or black horizontal streaks or smudges that appear control the quality of the picture while the camera to follow images across the screen. The effect is more is in operation. See Field camera. apparent at vertical edges of objects where there is studio headend link (SHL) See Studio transmitter link. an abrupt transition from black to white or white to studio transmitter link (STL) A specific application of black. It can be caused by excessive low-frequency a microwave relay system that connects the studio response. of a TV station to its transmitter site. The STL trans- stream 1. To transmit multimedia files that begin play- mits a signal point-to-point from the studio to the ing upon arrival of the first packets, without need- transmitter where it is retransmitted on the station’s ing to wait for all the data to arrive. 2. To send data assigned channel. In CATV a similar electronic con- in such a way as to simulate real-time delivery of figuration is called a studio headend link (SHL). See multimedia. also AML frequencies. streaming media Multimedia content—such as video, subaudio A frequency below the normal audio range. audio, text, or animation—that is displayed by a cli- The lower audio limit cannot be accurately defined ent as it is received from the Internet, broadcast but a subaudio frequency can be taken as one network, or local storage. below 15 Hz. streaming video Compressed audio and video that is subband channels Special TV channels, 11-41 MHz transmitted over the Internet or other network in real (below channel 2). time. Typical compression techniques are MPEG-2, subcarrier A secondary signal containing information MPEG-4, Microsoft WMT, RealNetworks, and Apple’s that is added to a main signal. QuickTime. It usually offers “VCR-style” remote con- subcarrier band A band associated with a given sub- trol capabilities such as play, pause, fast forward, carrier and specified in terms of maximum subcar- and reverse. rier deviation. stringer light Kicker. subcarrier drive Sine wave signal at subcarrier refer- strip (US) Scanning line. ence frequency.

263 subcarrier oscillator subcarrier oscillator The crystal oscillator that oper- terpolation are widely used in digital TV for video ates at the chrominance subcarrier or burst frequency compression. of 3.579545 (or 4.433618) MHz in a color TV re- Subsidiary Communication Authorization See SCA. ceiver. This oscillator, synchronized in frequency and Subsidiary Communication Service (SCS) See SCA. phase with the transmitter master oscillator, furnishes subsonic filter Special VCR electronic circuitry that the continuous subcarrier frequency required for de- operates below 20 Hz to eliminate undesirable sub- modulators in the receiver. sonic signals by accurately tracking the noise reduc- subcarrier pass filter A particular bandpass filter tion system. These filters that work within the VCR’s whose function it is to restrict the luminance infor- audio system correct any mistracking resulting from mation in color TV signals. Subcarrier pass filters are inappropriate audio circuitry that is incapable of used when it is necessary to separate color informa- tracking a wideband signal. tion. Another application of these filters is in mea- substitution See Encryption. suring differential gain distortion. The filter can be substrate A material whose surface contains an ad- connected directly to the signal paths. hesive chemical for bonding or coating purposes. subcarrier phase shifter Special circuitry designed to Videotape, for example, has a substrate designed control the phase relationships of the two portions to hold oxide or other magnetic particles necessary of the encoded color signal so that they maintain for recording information. their correct relationship during recording, transmis- subtitle Superimposed caption at the bottom of the sion and reproduction. A phase shifter allows the TV screen; a translation of dialogue in a foreign user to change the timing of the signals involved so movie shown at the bottom of the screen. that they occur at the correct time and are thus said sun outage A natural phenomenon that occurs when to be in phase. the orbital positions are such that a satellite and the subcarrier rejection filter A bandstop filter that mini- sun are in one line. As a result, the earth station mizes the level of subcarrier color signals, either NTSC receives signals from both, with the more powerful or PAL (3.58 or 4.43 MHz). To reduce the distortion sun suppressing the preferred signal. This results in of the luminance signal, these filters utilize phase a sun outage. equalization. The rejection filters are used to prevent sun shade A metal cylinder attached to the end of a flashes of color on the TV screen when black and lens to keep light from entering the lens from the white information is broadcast on a color system. The periphery of the angle of view. filter is simply inserted in the video line. It may also be super The superimposition of one video signal on an- used in conjunction with black and white monitors other using the fader controls of the special effects to prevent interference from the color signal. generator. subjective grading Of the performance of an equip- super band A range of radio frequencies from 216 to ment or system, a method of grading in which a 600 MHz, used for citizen’s band (CB) and CATV. panel of observers records their assessments accord- superband cable TV TV channels that occupy fre- ing to a scale. For example, interference to a sound quencies not used for TV broadcasting. Superband or TV program can be classified as negligible, slightly channels, which start just above channel 13, usually distracting, distracting, very distracting or completely range from channel J, operating at 216 to 222 MHz, distracting. to wherever the cable operators want to take them. subliminal Below the threshold of conscious respon- See also TV channel assignments. siveness to a stimulus. Applications include behav- Super Beta A VCR and camcorder enhancement in- ior modification that involves audio or video troduced by Sony and designed to improve the qual- motivational stimuli. ity of the video image. subpixel A subdivision of each pixel (picture element). Super Beta Hi-Fi. A system that overcame the limited Although digital images are made up of pixels, it resolution of not only Beta Hi-Fi but also of conven- can be useful to resolve image detail to smaller than tional Betamax units. The increased resolution was pixel size. For example, in order for a curve to ap- achieved by using narrower gap heads that resulted pear smooth on television, the data used to gener- in an improved high frequency response, and a 0.8- ate it must be created to a finer accuracy than the MHz upward shift of the FM luminance carrier re- pixel grid in order not to appear jagged. sults in a larger lower sideband. subsampled Subsampled means that a signal has been Superbit DVD See DVD-Video. sampled at a lower rate than some other signal in Super Black A keying signal embedded within the the system. A prime example of this is the YCbCr composite video signal as a level between black and color space used in ITU-R BT.601. For every two lu- sync. It is usually used to improve luma self-keying minance (Y) samples, only one Cr and Cb sample is because the video signal contains black, making a taken. The Cr and Cb signals are subsampled. good luma self-key hard to implement. When a subsampling A method of reducing the bandwidth downstream keyer detects the super black level, it required to transmit a signal. Subsampling and in- inserts the second composite video signal.

264 Super-VHS

supercapacitor In video, the memory backup method an intermediate “carrier” and transmitted by satel- employed by many VCRs in the event of a power lite to cable systems throughout the nation. Basi- failure. The supercapacitor stores an electrical charge cally, it is a local station with typical local that is activated whenever an external electrical out- programming of sports, films and other features, age occurs. This smaller element, which retains VCR tuned in by residents of the city in which the program instructions and keeps the clock function- superstation is based. But because of its national ing from about 5 seconds to about 30 minutes, has exposure, the station can raise its advertising rates. generally replaced the more costly nickel cadmium Ted Turner’s Atlanta TV station, WTBS-Channel 17, battery cells, which were known to last for several was the first superstation to appear on cable TV. hours. A handful of VCR manufacturers utilize a large Other include WGN-TV, which began supercapacitor to provide extended protection broadcasting in in 1948 and went on satel- against power failure. lite in 1978; WOR-TV in New York; and KUTV in super-cardioid Variable-D. A microphone with a very Oakland. directional pickup pattern, allowing sound to affect supersync signal A combination vertical and hori- the element only if it is coming toward the front of zontal sync signal transmitted at the end of each TV the mic. scanning line to synchronize the operation of a TV Super Density (SD) One of the first versions of DVD receiver with that of the transmitter. systems; Toshiba/Time Warner. Competed with Mul- supertrunk A cable that carries several video chan- timedia Compact Disc (MMCD). In 1995, all com- nels between facilities of a cable TV company. A panies agreed to the single DVD standard. trunk between the master and the hub headends in super emitron Image iconoscope. a hub CATV system. superhigh frequency (SHF) A frequency range in the supertrunking Method used by CATV systems to electromagnetic frequency spectrum measured in transport signals from hub to hub, where the hub GHz rather than in the conventional MHz of the site is the center of a distribution center for a given lower spectrum. Used primarily for high-data-rate community. Unlike conventional TV system trunk LOS microwave, multichannel radio relay, lines, the supertrunking usually contains no bridg- troposcatter, and satellite systems. ing amps and no signal splits; generally it just con- super iconoscope Syn.: emitron. nects hub to hub points. superimposition The overlapping of one image onto superturnstile antenna The superturnstile antenna another. In video, a character or special effects gen- was one of the first to be introduced in the early erator is used to create this effect. Some video cam- years of TV broadcasting, and it is still in wide use eras permit electronic superimposition as well as for VHF stations. The dipole is a pair of radiators, titling. One of the shortcomings of early generators sometimes called bat wings because of their shape, was that one of the cameras (the one supplying the mounted on opposite sides of a supporting pole. special effect) had to be a black and white model. The radiator consists of two dipoles mounted at right Superimpositions can be tinted any color. angles, and the antenna consists of two to twelve super in sync A direction to superimpose words or an layers of dipoles. image on a TV screen while an off-camera voice reads supertwisted nematic (STN) A reference to an ad- the text. vanced form of liquid crystal that is used in active- Super-NTSC Also Faroudja Super-NTSC; see also Line matrix liquid-crystal video displays. doubling. A proposed modification to NTSC that Super VGA See SVGA. improved the signal to near analog HDTV quality. A Super-VHS A VHS format that delivers a sharper pic- single-channel NTSC-compatible EDTV system op- ture, produces 400 lines of horizontal resolution and erating on a 6-MHz channel with a 525-line, 59.94- can play back standard videotapes recorded on con- fields/s, 2-to-1 interlaced signal. The aspect ratio was ventional machines. Although present American 4:3 initially, with 29:18 (=1.61) as a later objective. analog broadcast and cable programs produce a Progressive scanning was used in the camera and maximum of about 330 lines, S-VHS recorders pro- advanced receiver display. Camera scanning was at vide better quality reproductions than standard VHS 525 lines for initial low-cast production, with a subse- machines that can capture only 230 to 240 lines. quent preferred value of 1050 lines, 59.94 frames/s. Technically, S-VHS accomplishes its improvements by The progressive scan was converted to interlaced for increasing the Y signal range, reducing the Y and C compatible service in a scan converter that stored (chrominance) signal crosstalk, using a better grade the progressive lines and read them out at the inter- of tape and narrowing the video head gap. In addi- laced intervals. Included in the converter were tion, the format has increased its frequency band- Nyquist prefilters that reduced aliasing from verti- width from 3.4 to 5.4 MHz, thereby expanding the cal, temporal, and interlaced sampling. amount of information that can be recorded. This super sandcastle pulse Three-level sandcastle pulse. results in better detail in the final screen image. To superstation A local TV station that is picked up by carry the increased data, a high-grade tape capable

265 Super-VHS-C

of holding the finer and more densely distributed tor at the receiver that regenerates the carrier fre- particles is required. To fully enjoy the benefits of quency and mixes it with the received signal in or- the S-VHS format, which was introduced in 1987, a der to detect the modulating wave. This method of high-resolution monitor equipped with separate Y/ detection is termed synchronous detection. C video inputs is essential. suppression Blanking. Super-VHS-C A VHS video recording format that pro- suppressor Interference suppressor. duces 400 or more lines of resolution with a special, surface acoustic wave See Surface acoustic wave higher-priced compact videocassette. These mini-cas- (SAW) device. settes are compatible with full-sized Super-VHS re- surface acoustic wave (SAW) device A device which corders by way of an adapter cassette. S-VHS-C makes use of radio waves in the form of surface offers certain advantages, including higher resolu- deformations on piezoelectric materials. Such waves tion, smaller and lighter camcorders, improved cop- can be excited by suitable transducers and they have ies and editing as a result of reduced signal loss and wavelengths about 100,000 times smaller than those Y/C video connectors. in free space. Thus, the wavelength of a 35-MHz Super-VHS compatibility The ability of the S-VHS wave is less than a millimeter and it is possible by format to play back standard VHS tapes. S-VHS com- suitably shaping the piezoelectric surface to produce patibility has its limitations. Although the format can an extremely small filter by techniques similar to play back standard VHS tapes (without the additional those used in microwave filters. Bandpass filters of quality), S-VHS videocassettes will not play back on this type are used in the IF amps in TV sets and VCRs. standard VHS machines. surface acoustic wave (SAW) filter See SAW filter. Super-VHS tape A videotape capable of recording surface integrity Refers to the face or surface of a high-frequency signals without the use of a metallic parabolic antenna that is part of a satellite TV sys- powder formulation that would make standard VHS tem. To receive the best possible signal from a satel- taping incompatible. Tape designed for S-VHS ma- lite, the surface of the antenna dish should be as chines employs a ferric-oxide compound like that close to perfect as possible, threby concentrating found on regular VHS tape. Super-VHS tapes, how- the reflected energy into one point. Deviations in ever, use smaller particles more densely packed and the parabolic curve cause this energy to stray or miss provide higher frequency output. the feed horn (or focal point) which is mounted ex- Super Video CD (SVCD) Next generation video CDs, actly in the center and front of the antenna. Toler- defined by the China National Technical Committee ances in this area are rather small. If the surface of Standards on Recording, primarily to sidestep DVD integrity is off more than about 1/16", reception technology royalties and to create pressue for lower may be adversely affected. Tolerances can be DVD player prices in China. SVCDs hold up to about checked by using a solid parabolic form called a tem- 2 hours of digital audio and video information. plate, sometimes supplied by the antenna company. MPEG-2 video is used, with a resolution of 480 x surface-mount technology (SMT) A manufacturing 576. MPEG audio layer 2 is used for two-channel technology in which leadless components are sol- audio. Subtitles use overlays rather than subpictures dered to leads on the surface of a circuit board with- (DVD) or being encoded as video (Video CD). Vari- out plated-through holes. able bit-rate encoding is used, with a maximum data surface wave A radiowave that travels along the sur- bitrate of 2.2 Mbps. face separating the transmitting and receiving aeri- Super-video input See S-video input. als. The surface wave is affected by the properties Super-video output See S-video output. of the ground along which it travels. supplementary lens An accessory lens placed over surrogate travel A technique of interactive audio/ the regular video camera lens, changing the view- video applications. With surrogate travel, we can sit ing angle of the original. With a supplementary lens, in our living room or our office and ask the com- a normal lens can be temporarily converted to a puter to take us to a distant site and show us the wide-angle lens; with a different attachment, a lens scenes and let us hear the sounds of that locality can be made to function as a telephoto. However, while we interactively control our position within the some of these accessory lenses may not fit a lens site. from another manufacturer. surround brightness Brightness of the area around suppressed carrier (SC) A carrier that is suppressed the image. See also Retinal illumination. at the transmitter. The chrominance subcarrier in a Surround decoder A technique designed to decode color TV transmitter is an example. the rear-channel audio track of theatrical films that suppressed-carrier transmission A transmission tech- have been encoded with Dolby Surround. See nique in which only the sidebands (one or both) are Audio decoder. transmitted and the main carrier is not transmitted surround shot An angle of view peculiar to highly and thus not used. NTSC and PAL are examples. Sup- portable recording equipment; the camera can en- pressed-carrier transmission requires a local oscilla- ter into the action and wander through it, giving

266 switchable delay time

the viewer the impression that the camera is part of letterbox picture format is being output. The extra the event. DC offset is used to indicate the mode to a 16:9 TV Surround Sound Circuitry, built into TV monitor/re- so it can process the image to full screen. A stan- ceivers, designed to enhance the stereo audio por- dard 4:3 TV ignores all DC offsets and so displays a tion of the system to simulate a theatrical or typical letterbox picture. Unlike component video, concert-hall effect. This is usually accomplished with S-Video does not keep each of the three primary only the two built-in speakers of the TV unit. More color signals separate. than 2,000 theatrical films have been made with S-video input An input for high-resolution video Dolby stereo Surround-Sound tracks; many have sources such as laser disc players and Super VHS, been transferred to prerecorded tapes with these Beta or Hi-8 VCRs. tracks intact. With the proper components, this sur- S-video output A connection on SVHS decks and DVD round effect, with its directional and ambient sounds, players that helps to deliver high-resolution Y and C can be reproduced in the home. Surround Sound signals to other units such as TVs. gives the effect that the audio is coming from the SVM See Velocity scan modulation. front, sides and rear of a room. One setup sends the sweep 1. The steady movement of the electron beam principal left and right audio signals (music and across the screen of a CRT, producing a steady bright speech, for example) to the two speakers at the sides line when no signal is present. 2. The steady change of the TV screen while another channel with ambi- in the output frequency of a signal generator from ent sounds (automobile, airplane, etc.) are sent to a one limit of its range to the other. pair of rear speakers. Surround Sound systems of- sweep amplifier An amp in a TV receiver that ampli- ten require a decoder and a separate amplifier. Walt fies the sawtooth output voltage of the sweep os- Disney’s production of “Fantasia” (1940) was one cillator and shapes the waveform as required for the of the earliest theatrical films with multichannel deflection circuits. sound. The technique involved two synchronized sweep circuit The sweep oscillator, sweep amp, and films running simultaneously, with the second con- any other stages that produce the deflection volt- taining four-track sound. The Dolby Surround sys- age or current for a CRT. tem currently used in theaters gained its popularity sweep frequency The rate at which an electron beam as a result of the successes of the films, Star Wars is swept back and forth across the screen of a CRT. (1975) and Close Encounters of the Third Kind sweep generator A test instrument that generates (1977). an RF voltage whose frequency varies back and surveillance Systematic observation of air, surface, or forth through a given frequency range at a rapid subsurface areas or volumes by visual, electronic, constant rate. It produces an input signal for cir- photographic, or other means for intelligence cuits or devices whose frequency response is to be gathering. observed on an oscilloscope. It is also called a sweep surveillance camera A simplified TV camera, usually oscillator. black and white, used with closed-circuit video sweep oscillator 1. An oscillator that generates a equipment for security systems. sawtooth voltage which can be amplified to deflect SVCD See Super Video CD. the electron beam of a CRT. It is also called a time- SVGA Super VGA. A computer graphics standard de- base generator, a sweep generator, or a timing-axis signed to offer greater resolution than VGA. Also oscillator. called extended VGA and VGA Plus. sweetening A technique employed to enhance the S-VHS Super-VHS. An enhancement to regular VHS audio portion of a TV show. The process can be ap- video tape decks. S-VHS provides better resolution plied during or after the recording of the program and less noise than VHS. S-VHS video tape decks and involves audio control, recording, mixing and support S-video inputs and outputs, although this is post-production work. To sweeten or enrich the not required. It does, however, improve the quality audio, highly specialized and complex components by not having to separate and then merge the luma are usually required, such as echo-producing units, and chroma signals. audio tape recorders, equalizers and audio-mixing S-VHS quasi playback Playback of S-VHS tapes in consoles as well as high-quality microphones. The VHS. term is also occasionally used to describe the im- S-Video Separate Video, also called Y/C video. 1. A provement of the video image in a production. video format used in S-VHS and Hi-8mm video sys- swing The limits of the values of a varying electrical tems that separates the luminance (Y) and the parameter, such as amplitude or frequency. chrominance (C) of the signal to improve image qual- swish pan A rapid horizontal movement of a movie ity. By simply adding together the Y and C signals, or TV camera resulting in a blur; also called blur pan, you generate a composite video signal. 2. A video flash pan, flick pan, whip pan, or zip pan. The tran- interface standard. On some DVD players, a DC off- sitional or blurred scene itself also called a swish pan. set of +2.3v or +5v is added to the C output when a switchable delay time Adjustable Y-delay line.

267 switcher switcher 1. An accessory that permits routing any of inputs (any combination of antenna, VDP, video several input signals to any of several outputs. For game, VCR, etc.) and three outputs (two TV receiv- example, inputs usually include antenna, VCR, video ers and a VCR, for example). This unit would be des- game, pay TV decoder box, etc. Outputs may in- ignated as a 4x3 switching matrix. See Switcher. clude main TV, a second TV set, VCR (for duplicat- SXGA Super Extended Graphics Array. Computer ing tapes from the input VCR), etc. A simple switcher graphics display standard offering a resolution of permits viewing standard TV while recording en- 1280 x 1024 pixels. coded pay TV or vice versa—at the same time. It symmetry A digital video effect where the displayed also allows monitoring the output of either VCR picture appears as though split by an imaginary line, during the process of duplicating a tape from one one side having the original image and on the other machine to the other. A switcher simplifies the com- side of the split is a complementary mirror image. plexity of connecting various components and elimi- Syn.: double mirror. nates the entanglement of cables and wires around sync A shortened form used for referring to synchro- and behind the TV set. A passive switcher is one nous, synchronizing, synchronization, synchronize, etc. that has no amp or other device to change or modify sync data Information encoded within the time code the signals. Switchers are also listed by their num- word. The sync data, found in 16 bits at the end of ber of inputs and outputs. One with four inputs and the time code word, are used to define the end of three outputs, for example, is known as a 4x3 each frame. Because time code can be read in ei- switcher. Switchers, sometimes called video switch- ther direction, the sync data bits also function as a ers, are generally rated by their isolation, listed in signal to the controlling device as to the direction in dB. The higher the number, the better the isolation which the tape is moving. of signals. Production switchers are professional/in- sync generator A sync generator is a circuit that pro- dustrial units that provide a vast array of sophisti- vides sync signals. A sync generator may have cated features. See Digital switcher, Mid-range genlock capability, or it may not. A sync generator switcher, Production switcher. 2. The term is often supplies sync pulses to TV studio and transmitter used to describe a special effects generator, a unit equipment. It is also employed in all home video that allows the operator to switch between video cameras to synchronize the pulses required to regu- camera signals. Switchers are often used in indus- late or control a video system. Also called a sync- trial applications to switch between video cam- signal generator. eras monitoring certain areas for display on one synchro edit A conventional function of some VHS monitor; these kinds of switchers do not have sync movie cameras: editing start and stop operation is generators. performed precisely on the desired points by a single switcher contact That part of a switcher that acti- push-button control. This feature solves the problem vates the changing of signals from one input/out- of releasing Pause on two units simultaneously. The put to another. Contacts can be mechanical or synchro edit function may also be found on many electronic. Mechanical contacts may eventually de- VCRs, edit controllers and external editing consoles. velop dirt build-up, thereby diminishing the resis- synchro-edit input A special VCR jack that permits tance-free electrical circuit necessary to avoid noise. the VCR to be connected to a camcorder or another Switchers with electronic contacts are considered VCR of the same format for editing or dubbing pur- preferable since this type of contact retains its ef- poses. See Synchro edit. fective signal-to-noise ratio (measured in dB) indefi- synchronization 1. The maintenance of one opera- nitely. See Switcher. tion in step with another, as in keeping the electron switcher/fader A device that allows the connection beam of a TV picture tube in step with the electron of more than one video camera into a video system. beam of the TV camera tube at the transmitter. It is The switcher/fader permits two cameras or more to also called sync. 2. A multimedia term. A very pre- operate from the same sync source, thereby elimi- cise real-time processing, down to the millisecond. nating a discontinuous signal, which causes picture Some forms of multimedia, such as audio and video, roll, etc. The fader portion of the accessory permits are time-critical. Time delays that might not be no- the slow transition from one camera to the other. ticeable in text or graphics delivery are unaccept- switching area Timing window on a specific TV line able for audio and video. Workstations and networks where vertical interval switching is to be performed. must be capable of transmitting this kind of data in According to the SMPTE RP168 it must occur be- a synchronized manner. Where audio and video are tween the 25th and 35th microsecond on line 10 for combined, they must be time-stamped so that they the 525 system and between the 25th and 35th mi- can both play back at the same time. 3. In the I2C- crosecond on line 6 for the 625 system. bus system, procedure to synchronize the clock sig- switching matrix Refers to the number of inputs and nals of two or more devices. outputs on a switcher. Switchers have various in- synchronize To produce synchronization. Also called puts and outputs. A typical model may feature four sync.

268 synthetic diamond display

synchronizer A device performing a variable delay same frequency and are maintained in a desired function from minimal up to one whole frame, for phase relationship. Any of several data codes may the purpose of synchronization. Slight differences be used for the transmission, as long as the code between the frame rates of incoming and reference uses the required line-control characters. Also called signals can usually be accommodated. If the incom- bi-sync, or binary synchronous. ing and reference frame rates are different then oc- sync level In TV, the level reached by the peaks of the casional fields must be added or dropped, which synchronizing signals. can cause visible jumps. It is for this reason that VCRs sync limiter A limiter circuit for TV that prevents sync are often field-locked to zero, the long-term frame pulses from exceeding a predetermined amplitude. rate difference. Occasionally the word ”synchro- sync noise gate Used to define an area within the nizer” is used to describe a line synchronizer, with- video waveform where the video decoder is to look out a framestore. for the sync pulse. Anything outside of this defined synchronized editing See Synchro edit. window will be rejected. The main purpose of the synchronizing pulse See Sync pulse. sync noise gate is to make sure that the output of synchronizing signal In TV, the signals that ensure the video decoder is clean and correct. that the horizontal and vertical scanning circuits in sync processor A professional/industrial unit designed picture-display equipment are synchronized with the to reproduce the correct sync, blanking and burst picture-generating equipment. In color TV the syn- information, including their proper levels. The sync chronizing signal includes the color burst, which syn- processor can help to correct such problems as those chronizes the chrominance decoder. The resulting from noisy off-air signals as well as from synchronizing signal is added to the picture signal other video sources. Some models offer additional to form the video signal. Also called sync signal. features, including switchable line bypassing and a synchronism 1. Equality of frequencies and phases locking system that allows the processor to replace between two or more scanning processes. 2. Equal- any missing sync. ity of frequencies with fixed phase differences be- sync pulse One of the pulses that make up a sync signal. tween two or more scanning processes. sync separator A circuit that separates sync pulses synchronous Refers to two or more events that hap- from the video signal in a TV receiver. pen in a system or circuit at the same time. In digital sync signal Synchronizing signal. transmission, a procedure by which the bit and char- sync-signal generator Sync generator. acter stream are slaved to accurately synchronized sync stripper A video signal contains video informa- clocks at both the sending and receiving ends. tion, which is the picture to be displayed, and tim- synchronous demodulator See Synchronous ing (sync) information that tells the receiver where detector. to put this video information on the display. A sync synchronous detection Syn.: coherent detection. See stripper pulls out the sync information from the video Suppressed-carrier transmission. signal and throws the rest away. synchronous detector A detector sensitive to phase sync/test generator A professional instrument de- and amplitude variations in the modulated signal signed to synchronize with all standard composite applied to it. Such detectors are used for indepen- video signals so that various aspects of these pulses dently recovering the two components of the can be tested and measured. The sync/test genera- chrominance signal from the quadrature-modulated tor usually contains a color bar, “staircase,” white- subcarrier in the NTSC and PAL color TV systems. on-black window, convergence, alignment and color For successful operation the detector must be syn- raster displays. Some versions feature multiburst fre- chronized with the reference signal (color burst) con- quencies while others provide graduated video tained in the TV color signal. Also called synchronous sweeps. Other functions include variable control of demodulator. luminance and chroma, interlace and progressive synchronous satellite A satellite that is placed in or- scanning, outputs of composite video, subcarrier, bit in a west-to-east direction 22,300 mi (35,880 black burst, etc. In addition, many models measure km) above and parallel to the equator. It completes sync amplitude, equalizer width, vertical pulse width, an orbit of the earth in 24 h and therefore appears horizontal and vertical blanking widths, burst am- to be stationary. When functioning as a communi- plitude and number of cycles in burst. cation satellite, it can carry relay transmitters that sync timing Relative timing of two sets of horizontal greatly increase the range of TV and radio transmis- and vertical sync pulses held in synchronism. An er- sion. Also called geosynchronous satellite. ror in sync timing results in horizontal and vertical synchronous transmission A transmission method shifts of TV picture. The term is often incorrectly iden- where the synchronizing of characters is controlled tified with horizontal timing only. Sometimes the by timing signals generated at the sending and re- words are used to stress the lack of subcarrier tim- ceiving stations (as opposed to start/stop communi- ing or non-zero SCH timing. cations). Both stations operate continuously at the synthetic diamond display A video display for flat-

269 synthetic interlace

panel TVs using synthetic diamond film; SI Diamond In an ideal system, the gamma should be 1. In prac- Technology (SIDT). The synthetic diamond display is tice, it appears to be about 1.4. an alternative to LCDs and CRTs. When SIDT’s dia- system terminology These are the current catego- mond film is exposed to an electric field, it emits ries of TV systems: electrons better than any known material. Each dia- Conventional systems. The NTSC, PAL, and SECAM mond emitter activates a colored phosphor. As in systems as standardized prior to the development conventional TV tubes, the lit phosphors produce a of advanced systems. picture. The technique is known as field emitter dis- Improved definition systems (IDTV). Conventional play technology. systems modified to offer improved vertical and/or synthetic interlace See Bandwidth reduction (EU- horizontal definition. REKA-95 HDMAC system). Enhanced definition systems (EDTV). Progressive scan synthetic video Images constructed by combining a versions of SDTV. computer three-dimensional model with real video Advanced systems. In the broad sense, all systems images of surfaces, patterns, and textures. This tech- other than conventional systems. In the narrow nique allows a range of applications that create re- sense, all systems other than conventional and HDTV. alistic rendering of computer-designed objects, High-definition systems (HDTV). Systems having ac- interior designs, landscapes, or architecture. tive vertical resolutions of at least 720p. system blanking Combination of horizontal and ver- Simulcast systems. Transmission of conventional tical blanking added to a TV signal to ensure that NTSC, PAL, or SECAM on existing channels and no picture information is present during the synchro- HDTV transmission of the same program on one or nizing and retrace period of a receiver. more additional channels. system control and standard scanning A circuit to Production systems. Systems intended for use in the provide the information to set the multistandard production of program, but not necessarily in their color decoder into some TV receivers to the desired distribution. standard and system (NTSC-3.58, NTSC-4.43, PAL, Distribution systems. Terrestrial broadcast, cable, sat- SECAM, etc.). ellite, video cassette, and optical disk methods of system gamma The overall light-in/light-out charac- bringing programs to the viewing audience. teristic of a TV system, from camera through receiver. SDTV. Digital equivalent of NTSC and PAL standards.

270 T

T 1. The measurement unit describing the width of take-up reel spindle The right spindle in the VCR sine squared pulses and bar edges with reference to that drives the take-up tape reel of a cassette. the nominal system bandwidth. T = 1/(2xB), where talkback 1. A communications system within an au- B is assumed bandwidth. For countries using the dio or video studio linking the control room with 625-line standard it was agreed to set T = 100 ns, people in the studio. 2. In TV, a brief sequence at and for countries using the 525 line standard it was the end of a live remote news report in which the agreed to set T = 125 ns. 2. CATV superband channel, anchor asks one or more questions of the reporter. 276-282 MHz. talking head That part of the person seen in the typi- T-1 Also spelled T1. A digital transmission link with a cal business videoconference; the head and shoul- capacity of 1.544 Mbps (1,544,000 bits per second). ders. This type of image is fairly easy to capture with T-1 is a standard for digital transmission in the US, compressed video because there is very little mo- Canada, Hong Kong and Japan. Outside of the US tion in a talking head image. and Canada, the T-1 line bit rate is usually 2,048,000 tally A system of audio intercommunication among bits per second. At the higher rate of 2,048,000, 32 various members of the video production crew. A time slots are defined at the CEPT (the Conference tally light is set on top of each camera and glows of European Postal and Telecommunications admin- when that camera is the one on the line as the pro- istrations) interface, but two are used for signalling gram signal camera. and other housekeeping chores. Typically 30 chan- tally light Also called camera cue. Part of a tally sys- nels are left for user information—voice, video, data, tem, standard equipment on some studio cameras; etc. signals which camera of a multi-camera system is in Table 3 Compression Format Constraints Refers to use at any given moment. Light in a TV studio which the original 18 ATSC voluntary digital video formats. warns that a particular camera is in operation. In See ATSC. Britain, called a cue light. tabloid television Populist TV programming designed tap 1. An electrical connection permitting signals to be to appeal to a mass audience by featuring pop mu- transmitted onto or off a bus. 2. The link between sic, videos, and news and gossip about celebrities. the bus and the drop cable that connects the work- tails out A tape that has been played but not rewound; station to the bus. 3. A device used on CATV cables a tape whose end is nearest the outside of the rest; for matching impedance or connecting subscriber the opposite of heads out. drops. take 1. A scene, shot, or other single uninterrupted tape 1. A medium capable of storing an electronic sig- component. 2. A direction to move from one TV nal and consisting of backing, binder, and iron oxide camera or other video source to another. Take cam- coating. The orientation of the iron oxide determines era is an instruction to a performer to turn toward whether the tape can be used for helical scan video the camera. 3. In a DVE or vision mixer a “take” tape recording. 2. Television Audience Program Evalu- button (which may be remote controlled) will usu- ation, a technique of evaluating viewer reaction. ally trigger a predefined transition. In this context, tape cassette A package that holds a length of mag- “take” is sometimes called “auto-transition.” netic tape so that the package can be slipped into a take-bar In TV, a device that records and stores cuts, tape recorder or VCR and played without threading mixes, and other effects and then automatically pro- the tape. The tape runs back and forth between two duces them from memory for use in editing when a reels inside the cassette, called a cartridge. bar is pressed. tape deck The basic component of a tape recorder, take camera See Take. comprising the tape transport and a head assembly. take-up reel The reel upon which the tape is wound Some tape decks provide playback-only amplifiers as it leaves the supply reel during recording or play- and are usually listed as tape players. See Videocas- back on a tape recorder. sette player.

271 tape end sensor, VCR tape end sensor, VCR The metallic foil attached to 500 cassette. VHS provides 2 hours of playing time both the tape start and end are detected. An elec- in its SP mode with a tape speed of 3.34 cm/s, 4 trical circuit is closed, driving the auto-stop circuit. hours in its LP mode at 1.67 cm/s and 6 hours in EP tape-free editing Nonlinear electronic editing. or SLP with a tape speed of 1.14 cm/s, all with a tape guide In video, a metal and plastic free-spinning standard T-120 cassette. In addition, tape speed may spindle designed to keep the tape aligned with the vary within a specific format, depending upon the rotating video heads. Tape guides are sometimes mis- special effects built into the VCR and activated by takenly identified as twist pins, which serve a similar the user. These include slow motion, double speed but different function. A tape guide has a wide base play, several visual search mode speeds and full- and head, similar to a spool of thread, whereas a speed search without picture. twist pin has a tapered top. tape splice Physically connecting two ends of video- tape-guide spindle One of several posts used in VCRs tape. Splicing is usually not recommended because to accurately position the tape in the transport of potential damage to video heads, but kits and mechanism. special splicing tape are available. Videotape can- tape length Videotape length. not be spliced like movie film which, when held up tapeless camcorder A camcorder using minidiscs or to a light, reveals specific frames. It is almost impos- DVD discs to store digital video instead of tape. Some sible to locate one frame on tape since images are cameras can record high-resolution still pictures as placed down electronically as a diagonal magnetic well. To reduce the amount of memory needed, the signal. image data is compressed following the MPEG-2 tape tension guide The first tape guide near the sup- standard. ply reel of the videocassette. It is designed and ad- tapeless VCR Also known as a Personal Video Re- justed to maintain the appropriate skew of the tape. corder (PVR). Merging with computer technology, A faulty tape tension guide can cause video as well this device records TV programs on a computer hard as audio distortion during record and playback. drive instead of videotape. Nonlinear, so portions of tape-tension lever In VCRs, a lever that is used to a program can be viewed while simultaneously re- detect tape supply-reel tension. The lever is con- cording another portion. nected to a brake; when the tension decreases, the tape-load switch A small leaf switch in some VCRs to brake tightens to slow the reel. The reverse occurs detect when the threading mechanism has fully when the tape tension increases. threaded the tape around the video heads. tape threading A method of pulling the tape out of tape path The circuit the tape runs from supply reel to the cassette and around the head drum. take-up reel past the erase head, video heads, au- tape time remaining indicator Tape remaining dio/control track head, and between capstan and indicator. pinch roller; standardized on 1/2" machines by the tape transport Those mechanical components of the EIAJ. VTR that move the tape from supply reel to take-up tape-remaining indicator A VCR or video camera reel and back. feature that registers how much recording time is tape transport control A multi-function feature that left on a particular videotape. Usually displayed in transfers the forward and reverse visual scan and minutes, the indicator works regardless of the tape single frame advance functions from the VCR to the speed. This function was first introduced in 1980 by video camera. The built-in control is standard on Sharp on its VHS video recorder. The VCR contained some cameras and optional on others. a switch which had to be set according to the cas- tape transport system A system for moving and align- sette tape length. Sony further refined the function ing videotape within a VCR. The individual parts in- in 1982 on its SL-2500 model. Also known as tape clude tape guides, capstan, pins, and tension guides. time remaining indicator. A faulty transport system results in poor picture re- tape repair See Tape splice. production, damaged tape, etc. tape slack sensor, VCR If slack tape is detected in the target area In reference to a video camera, the face play or record mode, the tape must be rewound. of a camera tube. Also, with a CRT, the area on which When the tape slack is detected by the tape slack the image is formed and transformed into an elec- sensor element, the auto-stop circuit is energized. tronic signal. Home video cameras that use a cam- tape speed The speed at which videotape travels era tube usually have a target area 2/3" in diameter. through a VCR. Sony’s original 1-hour playing time The raster differs from the target area in the sense Betamax had a tape speed of 4 cm/s (Beta I). Its Beta that it (the raster) refers to the pattern formed on II speed on its next generation of VCRs cut the tape the target area (the flat surface area coated with a speed in half to 2 cm/s with a 2-hour playing time. light-sensitive element). Finally, to compete with VHS, Sony once again re- target voltage The potential difference between the duced the tape speed to 1.35 cm/s with its Beta III cathode and the signal electrode of a low-electron- mode, offering 3-hour maximum with a standard L- velocity camera tube. The minimum value that is re-

272 Teletel

quired to produce a discernible video output is the reception of signals, writing, images, sounds, or in- target cut-off voltage. telligence of any nature by wire, radio, visual, or other tartan [color] bars A test matrix consisting of several electromagnetic systems. The terms telecommuni- (usually 8) bands, each containing color bars with a cation and communication are used interchangeably, different sequence of colors. Together they cover but is usually the preferred term all—or almost all—possible horizontal and vertical when long distances are involved. color transitions. Useful to test 2D chrominance pro- telecommunication system The complete assembly cessing devices—e.g., comb filters. of apparatus and circuits required to effect a de- TBC Time Base Corrector. sired transfer of information. Systems include TV, TBS Turner Broadcasting System. See WTBS. radio, and telephony. TC Time code. teleconference A conference whose participants are TCI Time compression integration. some distance apart but are able to talk to and see TCP/IP Transmission control protocol/Internet proto- each other because of telephone and/or TV links. col. An Internet protocol standard developed by the telematics A synthesis of functions: the integration of U.S. Department of Defense in the 1970s. TCP con- voice communications with text, image, and data trols the exchange of sequential data. IP handles the communications into a new system. In a broader routing of outgoing and recognition of incoming sense it also includes entertainment and the postal messages. service. “Telematics” is the word commonly used in TDF Telediffusion de France. Europe for the integration of voice communications TDM 1. Time division multiplexer. 2. Time division with text, image, and data communications. In the multiplexing. U.S., “compunications” is sometimes used. tearing A TV picture defect in which groups of hori- telemedicine Using videoconferencing to diagnose zontal lines are displaced in an irregular manner, illness and provide medical treatment over a dis- caused by inadequate horizontal synchronization. If tance. Used in rural areas where health care is not this occurs in a satellite-TV picture, it is usually an readily available and to provide medical services to indication that the receiver is operating well below prisoners. the FM threshold. tele-macro A video camera feature that allows the TEL Trans-Europe Line. user to fill the entire frame of the picture with an telco A telephone company. In broadcasting, a telco object at distances of between 2 and 3.5 feet. Tele- line is telephone cable, commonly used to transmit macro virtually closes the gap between the minimum radio and TV broadcasts. The plural is telcos. normal focus distance and the maximum macro set- telco line See Telco. ting. With a conventional camera in the normal telcos See Telco. mode, the operator would have to move in to about tele- Prefix meaning from a distance. 4 feet of the subject or object. telebook A book published to accompany, and give telenovela A romantic TV soap opera; especially in further background detail relating to, a TV series. South and Central America. telecast Television broadcast. 1. To broadcast by TV. tele-operated Remote-controlled. 2. The transmission of a TV program intended for telephone programming See Remote telephone reception by the general public. programming. telecasting Broadcasting a TV program. telephoto lens A lens with a long focal length that telecine A device for turning motion picture images permits a TV camera to obtain large images of into TV signals. Performs TV analysis of motion pic- distant objects. ture films and occasionally diapositive (reversal) stills. telepic A feature-length motion picture made for TV. Also called film scanner. See Film chain. teleports Engineering complexes that contain on-line telecine adapter A device usually containing a mir- technical capabilities primarily related to satellite ror, a lens and a small screen used for making film- communications. Teleports provide uplink and down- to-tape transfers. A film or slide projector is aimed link services for audio, video, and data and voice at a lens and/or angled mirror which transfers the transmission on Ku-band and C-band satellites. They image onto a small screen, which in turn is recorded normally have microwave relay and fiber optic ca- by a video camera. These adapters vary in complex- pabilities for technical interconnections to and from ity and price. producers, stations, syndycators, and SNG operations telecom gold See Teletext. and can provide encryption (scrambling) services. telecomms Informal telecommunications. Cf. comms. Some teleports also have production and telecommunication facilities The aggregate of equip- postproduction facilities. ment, such as telephones, cables, switches, etc., used teleprompter TV device by which a speaker can read for various modes of transmission, such as digital an enlargement of the script in front of him/her, so data, audio signals, image and video signals. that he/she seems to speak spontaneously. telecommunication Any transmission, emission, or Teletel A two-way French videotex system that has

273 teletext

become a national service. It is sometimes referred the user, and is displayed on a TV screen. TV sys- to as Minitel. The system received a great deal of tems are basically sequential transmitting systems attention for its development of an electronic phone and are limited by the time taken for the required book. An individual can query a computer data base information to become available to the user. A tele- for a telephone number, which appears on the TV phone system, however, is capable of providing screen. Other uses involve “smart cards,” which al- much more information to the user, since any infor- low the user to insert a slim credit card into a home mation in the central store may be demanded by terminal to transfer money or pay bills. In addition, the user, and it is limited only by the size of the cen- families can shop at home and make hotel reserva- tral store. It also differs from TV systems in that it is tions, as well as access news and information. an interactive two-way system in which data may teletext (TT) 1. A method of transmitting data with a be transmitted to the central system by the user em- video signal. ITU-R BT.653 lists the major teletext ploying a suitable interface with the system, such as systems used around the world. North American a microcomputer. With the emergence of digital TV, Broadcast Teletext Specification (NABTS) is 525-line the future of teletext is in doubt. system C. For digital transmissions such as HDTV teletext datacasting Datacasting is the use of lines and SDTV, the teletext characters are multiplexed as in the vertical blanking intervals to transmit a data a separate stream along with the video and audio service for commercial purposes. The ordinary TV data. It is common practice to actually embed this viewer is generally oblivious to the existence of the stream in the MPEG video bitstream itself, rather service. The datacast service is offered by the BBC in than at the transport layer. Unfortunately, there is the UK. The first equipment designed to offer the no wide-spread standard for this teletext stream— facility commercially was activated in 1986 at the each system (DSS, DVB, ATSC, DVD) has its own BBC TV center. The datacast line structure differs solution. The practical place in MPEG to put teletext from the ordinary teletext line structure because it is data is in the user_data field, which can be placed not page dependent. Thus, only changing data needs at various frequencies within the video stream. For to be sent to the receiving decoder. The background DVD, it is the group_of_pictures header, which usu- image can be generated by a computer program ally precedes intra pictures (this happens about two resident in the receiving decoder. This factor improves times a second). For ASTC broadcasts the data is the overall security of the system. The clock run in inserted in the user_data field of individual picture and framing code are identical to ordinary teletext headers (up to 60 times/sec). 2. An information ser- line parameters. This is to enable the use of stan- vice in which information can be displayed as pages dard transmission techniques. of text on the screen of a commercial TV receiver. teletext decoder A device that detects teletext sig- The information may be transmitted as part of the nals on a TV broadcast and converts them into a commercial TV broadcast signal or as coded tele- text and graphics image displayed on the TV screen. phone signals. It is in the form of PCM signals that teletext editing terminal A device for creating the use two of the unused lines in an analog TV video text and graphics codes for teletext transmission. signal transmitted during the normal vertical retrace teletext line[s] 1. Line[s] in the vertical blanking inter- period. Special decoding circuits are required for the val allocated for teletext service. 2. Coded pulse extraction of the TT signals from the normal TV sig- sequences inserted in one or more lines of the verti- nals or from the telephone line and for decoding cal blanking interval and carrying teletext data. them. A typical TT page consists of 24 rows with up teletext printer An accessory used in conjunction with to 40 characters in a row. A limited amount of color TV sets capable of receiving and saving teletext in- information can be used and a flashing facility is formation for future reference. Teletext printers are also provided. The TV systems transmit the coded usually activated by the remote control that is sup- lines during each field blanking period. TT decoders plied with the TV receiver. contain facilities enabling the user to select the page teletext standards The published character codes and required and to store and display the information. transmission standards for a teletext system. The Brit- They also have facilities for inserting news flashes ish Ceefax teletext service uses an alphamosaic into the normal TV picture, or to insert subtitles for standard. people with impaired hearing. Some allow the full televangelism The activities of a televangelist. text to be superimposed on the normal picture or televangelist (especially in the US) A Christian minis- can store the required information for later display. ter, who hosts TV shows in which the church’s mes- It is also possible to display the current TV program sage is preached with great fervor and donations in much reduced format as a small insert in the TT are sought. display. TT is widely used in the UK. The BBC’s Ceefax televise To pick up a scene with a TV camera and was the world’s first teletext service. convert it into corresponding electric signals for The TT information in a telephone system is trans- transmission by a TV station. mitted as coded telephone signals, on demand from television A telecommunication system in which both

274 television repeat-back guidance

visual and aural information is transmitted for re- channels fall within 54 to 890 MHz. This comprises production at a receiver. The basic elements of the all VHF low-band, VHF high-band, UHF (standard), system are: UHF (translator), RCI subchannels, and midband, • TV cameras and microphones that convert the superband and hyperband cable TV channels. See original visual and aural information into elec- also TV channel assignments. trical signals—i.e., into video signals and audio television game Video game. signals respectively; television-guided bomb A bomb that carries a small • amplifiers and control and transmission circuits TV camera in its nose for guidance. The camera sys- that transmit the information along a suitable tem can be locked on the target before the bomb is communication channel: broadcast TV uses a dropped, for self-guidance, or the pilot can monitor modulated RF carrier wave; the camera picture over a microwave relay link and • a TV receiver that detects the signals and pro- adjust the course of the bomb by remote control duces an image on the screen of a specially de- after dropping the bomb. signed CRT and a simultaneous sound output (TVI) Interference produced from a loudspeaker. in TV receivers by computers, power tools, amateur Two men claimed to have coined the word “tele- radio, and other transmitters. vision.” One was Hugo Gernsback, then the publisher television line (tvl, TV line) Commonly used measure of Radio News (he later founded Gernsback Inc., the of spatial frequency of periodic pattern in a TV pic- publisher of Radio-Electronics, which was renamed ture expressed as a ratio of picture height to the Electronics Now in 1993). In the August 1928 issue half period of the pattern. For example, for 625/50/ of Radio News, Gernsback wrote: “The word televi- 2:1 scanning standard, a 1-MHz video signal pro- sion was first coined by myself in an article entitled duces a periodic TV screen pattern with a spatial ‘Television and the Telephot’ which appeared in the frequency of about 78 tvl. December 1909 issue of Modern Electrics.” The other television line number See Aperture response. person who claimed to have coined the word in 1900 television pickup station A land mobile station used was a Frenchman named Perskyi. for the transmission of TV program material and re- television black See Black. lated communications from the scene of an event television broadcast band The band extending from occurring at a point remote from a TV broadcast 54 to 890 MHz. 6-MHz channels are assigned to TV station. broadcast stations in the US. The frequencies are 54 to television picture photography To obtain photo- 72 MHz (channels 2 through 4), 76 to 88 MHz (chan- graphs of the screen of a TV receiver, a speed of 1/30 s nels 5 and 6), 174 to 216 MHz (channels 7 through (1/25 is closest on most cameras) is required to ob- 13), and 470 to 890 MHz (channels 14 through 83). tain one complete frame (two fields). The aperture Many countries use 7 or 8 MHz channels. must be set according to the reading of an expo- television broadcast translator Translator. sure meter, using the daylight exposure index. Very television camera The pickup unit that converts a fast pan film, such as Tri-X with an ASA daylight scene into corresponding electric signals. Optical index of 200, is needed. A tripod is essential. Turn lenses focus the scene to be televised on the photo- out room lights, and use the maximum brilliance that sensitive surface, typically made up of solid-state still gives a clear picture. receptors called charge-coupled devices (CCDs) in television picture tube See picture tube. today’s cameras. The target area of the CCD con- television receive-only antenna A parabolic reflec- tains from hundreds of thousands to millions of pixel tor or dish large enough to receive signals intended points, each of which responds electrically to the for cable TV systems from geostationary satellites, amount of light focused on its surface. together with a feed horn that collects the signals television camera tube Pickup device in a television reflected by the dish, a low-noise amplifier (LNA) camera. for preamplification, and a tunable satellite receiver. A band of frequencies 6, 7, or 8 television receiver Also, television set. A device to MHz wide in the TV broadcast band, available for convert incoming TV signals into the original scenes assignment to a TV broadcast station. along with the associated sounds. television engineering The field of engineering that television reconnaissance Reconnaissance in which deals with the design, manufacture, and testing of TV transmits a scene from the reconnoitering point equipment required for the transmission and recep- to another location on the surface or in the air. tion of TV programs. television relay system Television repeater. television film scanner A motion-picture projector television repeat-back guidance Command guid- adapted for use with a TV camera tube to televise ance in which a TV camera and transmitter are 24 frame/s motion-picture film at the 30 frame/s rate mounted in a guided missile or pilotless vehicle to required for TV. provide a view ahead for the operator at the remote- television frequency spectrum All TV broadcast control location.

275 television repeater television repeater Also called television relay sta- temporal resolution The capability of a display to re- tion. A repeater that transmits TV signals from point produce adequate image detail to allow the visual to point by using radio waves in free space as a system to distinguish the separate parts or compo- medium. This transmission is not intended for direct nents of an object moving through the display. reception by the public. tension The pull of the capstan assembly on the video television satellite An orbiting satellite that relays TV tape to keep it against the video head drum assem- signals between ground stations. bly; used in conjunction with the skew control to television screen The fluorescent screen of the pic- keep tape properly in path. ture tube in a TV set. tension error Skew. television set Television receiver. tent card A point-of-purchase (POP) merchandising television signal The general term for the audio and device that is a small advertising display for an item visual signals that are broadcast together to provide in a retail store or home video outlet. It is imprinted the sounds and pictures of a TV program. on two sides and folded so that it can stand alone -transmitter link A fixed station that and be read from either side. transmits TV program material and related commu- tentelometer An instrument to measure video tape nications from a studio to the transmitter of a TV tension anywhere in the tape path and at any diam- broadcast station. eter of tape pack. television transmission standards The standards that terminal A device with which information may be in- specify the characteristics of a TV signals. For NTSC put to or output from a communications system. signals in the U.S., channel width is 6 MHz, the vi- Visual display units are often known as terminals. In sual carrier is 4.5 MHz lower than the audio center videotex, the presentation entity that exchanges frequency, the audio center frequency is 0.25 MHz coded bit combinations with the host by means of lower than the upper frequency limit of the chan- telecommunications and presents it for human con- nel. There are 525 scanning lines per frame period, sumption. and they are interlaced 2-to-1. The frame frequency termination The insertion of a load at the end of a is 30 per s and the field frequency is 60 per s. The line carrying a signal; a video termination is a 75- aspect ratio of the transmitted TV picture is 4:3. The ohm resistor placed at the end of a line to keep the scene is scanned from left to right horizontally and signal from bouncing back along the line; 600 ohms from top to bottom vertically at uniform velocities. is commonly used to terminate an audio line. A decrease in initial light intensity increases the ra- terminating resistor A resistor (usually 75 ohms) at- diated power. tached to the end of a cable or to an input or out- A visual and an audio trans- put on a piece of video equipment. The resistor mitter interconnected together for transmitting a restores proper system impedance. complete TV signal. terminator A plug connected to unused outputs of television white Net pure white, having about 60% distribution amplifiers and other open terminals to reflectance (about 60% of light is reflected from the prevent power loss. The 75-ohm type is generally TV screen). The TV camera cannot reproduce pure used. white or pure black. terrain shielding A broadcasting situation in which Telidon Videotex system, Canada, founded in 1978, mountainous or other irregular terrain blocks or went offline in 1985. weakens the transmitted signals of a radio or TV telly Colloq. television (in British usage). facility. Such topographical shielding sometimes pre- telop Telopticon. A device for projecting small cards vents interference with the signals of other nearby on TV for announcements. The term is also used to broadcast operations. describe the slides used with a balopticon, though terrestrial (of TV transmissions) Carried out from con- these actually are balops. ventional ground stations rather than by satellite. Telset Videotex system, Finland. terrestrial field Radio, TV, or other transmission via Telstar Communications satellite used (commercially) land lines such as telephone, or direct (without lines); for the transmission of telephone messages and TV. different from satellite field. Telstar I was launched in 1962. terrestrial HDTV broadcasting See HDTV. temporal aliasing Video picture defect that occurs terrestrial interference (TI) Interference to satellite when the image being sampled moves too quickly reception caused by ground-based microwave trans- for the sampling rate. A common example is when mitting systems, often from telephone companies a wheel appears to rotate backwards because of that transmit in bands similar those of satellites. It video scanning that moves more slowly than the can affect one TV channel or more. Sometimes relo- wheel. cating the parabolic antenna minimizes the prob- temporal coding Compression achieved by compar- lem of TI. A special TI filter or circuit helps to eliminate ing frames of video over time to eliminate redun- microwave and other unwanted signals. dancies between frames. tesselated sync Serrated sync (Europe).

276 Three-dimensional image perception test disc (TD) In DVD, CD and CDV players, a standard chine may be rated as follows: THD of 2.9% at SP disc with signals recorded at the factory using very and 3.1% at LP and EP. The smaller the number, the precise test equipment and signal sources. The TD is better the performance. played on a player being serviced and the response thermal protection A feature found in some TV sets is noted and/or the signals are used to align and to protect the vertical deflection IC against too high adjust the player. Also called alignment disc, check dissipation. The protection is “active” at 175 de- disc, reference disc. grees Celsius (347 degrees Fahrenheit) and reduces test monitoring switcher A professional accessory the deflection current to such a value that the dissi- used in conjunction with video cameras, a video re- pation cannot increase. corder, a waveform monitor, and a color vectorscope. third generation Two copies away from the master The special switcher permits checking a recoded sig- tape. nal as well as the individual camera signals. The test threading A function of the VCR where tape is with- monitoring switcher differs from, but can be used drawn from the cassette and placed against the roll- along with, a production switcher. The cameras are ers and magnetic heads to facilitate recording and hooked up to the production switcher, which is con- playback. Threading is accomplished by the thread- nected to the test switcher, which in turn is plugged ing mechanism. into the vectorscope. Finally, the waveform monitor three-dimensional digital video effects system A is connected to the vectorscope. sophisticated professional/industrial device designed test pattern A signal or pattern used in TV broadcast- to simplify the creation of cubes and other solid ing that is transmitted at certain times when no pro- shapes on screen. The process involves the use of gram is being transmitted. The patterns are placed three separate inputs that will map a signal in three in front of a camera, or they may be artificially gen- dimensions onto a form during one pass on a single erated signals which are introduced into the system channel unit. after the camera. Because a camera has its own kinds Three-dimensional image perception The most of impairment, it usually cannot generate an accept- common example of three-dimensional image per- able signal for testing the rest of the system. There- ception is a person’s vision. When viewing an ob- fore, a camera is tested by itself with test charts, ject, a person’s eyes usually are situated at the same and then the rest of the system is tested with theo- vertical height but separated horizontally by 2.5" or retically perfect signals, which are electronically gen- so. As each eye sees the same scene, the perspec- erated by test signal generators. See Resolution tive each eye sees of the scene is slightly different. wedge. For example, the left eye, because of its spaced-apart test signal generator An industrial video unit that position from the right eye, will see just slightly more provides dozens of test patterns in composite, S- or less around a corner or curved surface than the VHS, RGB and several other output formats, with right eye. If the scene viewed by the eyes is broken RF channel coverage of all broadcast and cable chan- up into many very small dots of viewing perception, nels. Some models have a menu-driven multipur- the left retina will receive some dots which are hori- pose LCD readout control panel and storage zontally displaced from dots received by the right capability for 100 events. Standard patterns include eye due to depth difference and due to the fact that multiburst, video sweep, SMPTE color bars, modu- the left eye is spaced apart from the right eye. How- lated/unmodulated staircase, raster convergence and ever, no “advantage” is gained vertically since there crosshatch. The unit is known also as a video test is no vertical displacement between the eyes and signal generator. the same vertical component is seen by both eyes. text grabber A telecaption decoder that lets the user The person’s brain receives the images from each capture a transcript of any closed-captioned TV pro- eye (processes not yet understood), compares and gram for the hearing impaired and download it to a combines the images to give 3D sense to the scene PC. viewed by the person. The lessons of the eye may TFT Thin film transistor. A display technology which be applied to TV camera and receiver systems by uses active matrix technology that operates by as- utilizing two closely spaced TV cameras viewing the signing a tiny transistor to each pixel, making it pos- same scene whereupon the video signal output of sible to control pixels independently of each other. each camera is directed to a pair of TV receivers. TFT screens are very fast, have a high contrast ratio The scene viewed by each camera is repeated on and a wide viewing area. TFT screens are sometimes the CRT of a respective receiver. Then, if a party were called active-matrix LCDs. to view the two receivers stereoscopically—i.e., THD Total harmonic distortion. Refers to the distortion where a person’s left eye could only view the CRT of of the audio part of video equipment such as DVDs, the TV set receiving the output of the left TV cam- VCRs and VDPs. THD is measured in percent fig- era and the right eye viewing only the CRT of the ures, with each play/record speed having its own TV system receiving the output of the right TV cam- designated number. For instance, a typical VHS ma- era, the eyes would then see on the TV CRTs exactly

277 three-dimensional picture image

what they would see if they were viewing the scene the amount of light reaching the screen, the more themselves. The person’s brain would interpret the costly gun systems are preferred. This process sepa- two displays to reveal its three-dimensional aspects. rates the TV signal into basic color elements pro- three-dimensional picture image Picture images jected through quality lenses, retaining a sharp and called three-dimensional picture image or stereo- bright image, so essential in projection TV. Each color scopic image are classified into the following three image is enlarged by a refractive lens system utiliz- types: (1) Two-eye type picture image. From the point ing an F opening of f/1.0 or f/1.3 with 4-element, 5- of view of an amount of information, such a picture inch optics. Henry Kloss developed the three-gun image has an amount of information for the left technique. and right eyes. Also called a stereoscopic picture im- three-level sandcastle pulse Syn.: super sandcastle age. (2) A picture image as a reproduction image of pulse. A pulse used in older color TV sets and con- a body which looks afloat at a certain location in a sisting of horizontal blanking (required input volt- space. Thus, if a visual point moves, then a different age 4-5 V, typ. 4.5 V), vertical blanking (required side face of the picture image can be seen. Such a input 2-3 V, typ. 2.5 V), and burst gate (more than 7 V) picture image has an amount of information equal pulses. to or greater than that for a plurality of eyes. Such a three-point lighting The standard lighting setup used picture image is called three-dimensional picture in most video productions, which consists of a key image in a narrow sense. (3) A picture image that light, backlight, and fill light. The key light is the makes use of an optical illusion. main light source; the backlight illuminates the hair three-dimensional television After the popular suc- and outline of the subject; and the fill light softens cess of 3D films in theaters during the 1950s, sev- the shadows on the face created by the key light. eral companies made attempts to develop a 3D three-tube color camera A color-capable camera that system for TV. The major setback has been its in- produces a color signal through the use of three compatibility with normal, two-dimensional TV. pickup tubes, each assigned to one of the primary Mexico experimented with 3D in 1954, but by the colors. An early stage in the development of the color following year the process was dropped. Japan and video camera, introduced by RCA in 1940. Australia also tried to introduce 3D, but these at- threshold In an FM system, the value of the carrier-to- tempts also failed. All of the above systems used noise ratio (CNR) at which the linear relationship be- the special two-color glasses familiar to moviegoers tween CNR and demodulated signal-to-noise ratio in the 1950s. In 1975 a company called Mortek dem- (SNR) breaks down. See also Sparklies. onstrated a system without the use of glasses. In threshold extension Techniques for reducing the car- 1979 an optometrist, Dr. Robert McElveen, presented rier-to-noise ratio (CNR) value at which threshold ef- his glasses-free 3D system, which was compatible fects occur. with 2D TV. However, the picture flickered unaccept- threshold of visibility See TOV. ably. James Butterfield, chief scientist of 3D TV Sys- through-the-lens optical viewfinder A video cam- tems, Inc., presented his “3D Video” on subscription era viewfinder with the advantages of displaying TV in Los Angeles in December 1980, but once again exactly what the lens sees and offering adjustable viewers needed glasses. New York City had its day focus. It is more expensive than the simple optical when a local channel in the summer of 1982 pre- finder but less costly than the electronic type, which sented the 1954 movie Gorilla at Large in 3D, re- has become the dominant system used on home quiring viewers to purchase glasses at local chain video cameras. stores. Meanwhile, other systems continue to THX sound A consumer sound system designed to emerge. The latest systems make use of flat panel provide the best theater-quality sound for DVD, vid- LCD and plasma displays fitted with a wavelength eocassette and laserdisc viewing in the home. The optical filter to provide a wide-angle, “no-glasses” system is designed to bring out the unrealized au- 3D display. dio potential of theatrical film sound tracks and to three-gun picture tube A color TV picture tube with handle soft passages, high trebles, and deep bass three electron guns that emit three electron beams, tones with superior clarity. Developed in 1990. one for each primary color. Each beam is directed TI Terrestrial interference. onto phosphor dots that emit only the correspond- TIA Telecommunications Industries Association. ing primary color. Each gun is controlled by its ap- tier A pay TV channel carried by a cable TV service and propriate primary color signal. The shadow-mask offered to its subscribers for an additional monthly color picture tube is an example. charge. For example, Home Box Office is one tier three-gun projection TV A large-screen TV system commonly carried by many cable TV systems that using three separate lenses or tubes to project each can offer one or more tiers. of the three primary colors (red, green and blue) onto tiering Charging a CATV subscriber extra for pay-TV a screen. Since single-gun or single-lens projection channels and other tiers, often at a package price. systems limit the degree of picture sharpness and TI filter See Terrestrial interference.

278 time code word tight shot Close-up. problems such as faulty tape guides, tape tension tight two shot A direction to a TV camera operator discrepancies between VCRs, worn tape heads and for a close-up of the heads of two people. defective tape—all leading to an unstable TV pic- tilt 1. To move the camera up or down; pivotal move- ture. Time-base instability, or time base error as it ment of the camera in a vertical plane. 2. The angle sometimes incorrectly called, also refers to mechani- that an antenna axis forms with respect to the cal speed variations or the differences, however mi- horizontal. nor, in the actual timing of two VCRs. Since no two time base (TB) 1. The horizontal line formed by the machines are exactly the same, a dubbed tape may electron beam driven by the sweep-circuit on the often produce a picture with jitter or vertical roll. screen of a cathode-ray tube (CRT). 2. A voltage time-base stability The control and maintenance of that is a predetermined function of time and that is the scanning process to extremely close tolerances. used to deflect the electron beam of a CRT so that time code (TC) SMPTE standard for encoding time for the luminous spot traverses the screen in a desired video or audio in hours:minutes:seconds:frames. It manner. One complete traverse of the screen, usu- is an electronic or digital address (time code address) ally in a horizontal direction, is termed a sweep (or that individually identifies each frame and permits TB). The most common type of TB is one that pro- random access to each one. Time code is particu- duces a linear sweep: a sawtooth waveform is used larly significant in the editing process. Often, pro- to effect this. The circuit that produces the required fessional videographers use portable units hooked voltage is a TB generator; it may be free-running, in up to their camcorders or VCRs to record the time that a periodic sawtooth waveform is produced, or code on a separate address track, thus freeing both it may be clocked, when one sweep is produced on audio channels. Amateurs, however, face difficul- application of a trigger pulse to the circuit. The pe- ties in recording the SMPTE time code because the riod during which the spot returns to the starting simultaneous recording of the code and microphone point is the flyback and in TV sets the flyback is sup- signal by way of the Audio Dub mode often causes pressed—i.e., no luminous spot is observed on the “bleeding.” The standardized time code made off- screen during the return interval. The sweep fre- line editing efficient and functional for profession- quency is the repetition rate of the sweeps across als. Also called SMPTE time code. See VITC, LTC. the screen. A Miller sweep generator is a TB gen- time code address See Time code. erator that contains a Miller integrator in the circuit time code analyzer An external test instrument used in order to improve the linearity of the sweep. TV for locating time code errors during editing. In addi- systems employ TBs in the camera tubes and in the tion, the unit can match color frames, help set tape receivers to scan the lines and frames. The TB in the speed, realign video playback heads and check for receiver is controlled by sync pulses in order to re- “wow” (tape speed variations) on an audio synchro- tain the correct relationship to the transmitter. 3. nizer. The time code analyzer presents a readout of The relative accuracy of any portion of the video each time code. The unit, known also as a time code scanning process in record and/or reproduction as reader/generator, often comes equipped with video measured against the theoretical “time” at which a key and LED displays. given scan element is supposed to occur. The TB of time code generator A module that is either part of a field, e.g., is 60 times/s, each of which should oc- a stand-alone device or built into VTRs that outputs cupy no more or less than 1/60 s. a user-definable stream of time code onto a tape. time base corrector (TBC) Equipment that corrects time code reader A counter designed to read and for time base errors in VTRs. It is a computer that display SMPTE time code. evaluates the video signal to determine if each scan time code reader/generator Time code analyzer. line, field, and frame is in the correct time position. time code word Electronic time-encoded information If any of these elements is occurring too early, the recorded for each audio or video frame. Each word TBC will fill in the space left open by repeating a is divided into 80 segments called bits, which are previous line or field information. numbered consecutively from 0 through 79. One time base error The instability of a videotape play- word covers an entire audio or video frame, so that back signal created by the machine’s inability to play for every frame there is a corresponding time code back at exactly the same speed at which the tape address. In addition to the encoded time code ad- was recorded. Typically visible as a horizontal jitter dress, two other types of information are represented or instability in the reproduced picture. Time base within the time code word: user information (user error is measured in lines. It takes the electron gun bits) and sync information (sync data). The 26 time 63.5 µs to scan a video line. If the playback signal is code address bits, 32 user bits, and 16 sync data 63.5 µs off from where it should be, there is one bits add up to 74 bits, leaving 6 bits to complete the line of error. 80-bit time code word. These were originally unas- time-base generator Sweep generator. See Time base. signed bits intended for use with a future standard time-base instability A general term for technical mode of operation. Four of these bits are unassigned

279 time compression

and are defined as permanent binary zeros. Two bits time-division multiplexer (TDM) A device that de- have a special function (special bits). rives multiple channels on a single transmission fa- time compression A process that permits intelligible cility by connecting bit streams one at a time at viewing of and listening to a tape at a faster than regular intervals. It interleaves bits or characters from normal speed (usually double speed). The technique, each terminal or device using the time. See Time- using special integrated circuitry, eliminates distorted division multiplexing. sound, known as the Donald Duck effect, by drop- time lapse The shrinking of large periods of time into ping the pitch to normal. Time compression is use- shorter ones. Also called animation. ful in recording odd-length films on standard time lapse video Similar to time lapse (animation) cassettes. For example, a 128-minute movie can be photography, time lapse video entails recording ac- placed on a 2-hour cassette without editing. In ad- tion intermittently over an extended range of time vertising, the process can pack more information (such as sunrise to sunset) so that during playback than usual into a 30-second commercial. Some VCRs the action appears speeded up. Used mostly for spe- offer a feature called double-speed play that basi- cial effects, the technique is more difficult in video cally performs this function. than in photography because keeping the VCR com- time compression integration (TCI) A variation of ponent in pause for longer than 5 minutes may dam- the subsampling and interpolation technology, the age the tape or the video heads. A special timing basis of the Muse system developed and employed device called an intervalometer may be employed in by NHK. The analog signal is sampled and stored, this process to turn the video camera on and off but only a fraction of the samples—e.g., the samples automatically. The first home video camera with a from every third field—are read out. In this example, built-in time lapse feature was distributed by Akai. a point on the raster receives a signal only once ev- It had the capability of automatically shooting a sub- ery three frames. This causes no problems for sta- ject for up to 11 days at 90-second intervals with a tionary objects, but the resolution of moving objects conventional VHS cassette. is reduced. This problem can be corrected by mo- time-lapse VCR A VCR designed to record the video tion compensation circuits that interpolate the signal from a surveillance camera either in two hours missing information. of real time or up to hundreds of hours in time-lapse time compressor/expander A device, used in video recording mode. Some of these professional/indus- postproduction, film, and broadcasting, to make trial time-lapse VCRs use computer software that changes in the running time of a film or video and permits adding on-screen text to the recording. audio recording while maintaining the original, natu- time-lapse video recording A type of video record- ral pitch of voices, music, and effects. This device ing that captures images over a very long period of may be used to either shorten or lengthen a TV or time. Using a special VTR connected to a camera, radio spot so it will fit into an allotted time slot. the process can record anywhere from 8 to 200 hrs time constant 1. The time required for a voltage or of action, depending on the VTR model. Time-lapse current in a circuit to rise to approximately 63% of recorders are used to capture scientific experiments its steady final value, or to fall to approximately 37% and for surveillance and security purposes with hid- of its initial value. 2. The amount of variation in the den cameras in malls and banks. rate of sync pulses that automatic circuits of a TV timeline In nonlinear editing, the area in which video set will accept. The longer the time constant, the and audio clips are applied, usually giving duration slower the TV set can react to a different sync situa- in frames and seconds. Also used in animation and tion, and conversely, the shorter the time constant, composition software. the quicker the set’s response. time phase circuit See Automatic transition editing. time/date superimposition A video camera/VCR fea- timer See Programmable timer. ture that automatically records the time and date time search A VCR feature that permits the locating over an image. With a VCR, the time, date and chan- of any desired point on the tape by designating its nel are written at the beginning of any recording. time position. It can be operated by the remote con- time datum A reference time moment at the mid- trol. The time search is performed in cooperation level crossing point of the leading edge of the line with the linear counter that calculates the tape time sync pulse. This is the default timing reference in by detecting control pulse. Time search is especially the TV environment (as opposed to the active line helpful when trying to find a scene or program on a start that is commonly used in computing environ- commercial prerecorded tape or a tape not made ments). Syn.: 0h; line datum; line start [moment]. on your machine, two types that may not respond time-division multiplexing (TDM) A technique for to ordinary index searches. transmitting a number of separate data, voice and/ time shift In video, the ability to watch a TV-broad- or video signals simultaneously over one communi- cast program at the viewer’s prerogative, not at the cations medium by quickly interleaving a piece of officially scheduled time. This is done by setting the each signal one after another. VCR to record the program for playback at the

280 tracking level meter

viewer’s discretion. Because of the VCR’s recording topcoat Structural layer of magnetic tape. Used to capabilities, the machine differs from the VDP (which smooth the surface of video and digital audio does not record) in that the VCR can play back pre- magnetic tape. recorded tapes and time-shift programs whereas the topic box See Squeeze. VDP can handle only prerecorded discs. VCRs are top loading A type of cassette-loading scheme in often advertised as allowing the viewer to set up his which the tape is inserted into a lift mechanism on own “prime time.” Time shift, therefore, is one of top of the deck. Top-loading VCRs are no longer the VCR’s strongest features. See Downloading. made (with one exception—the camcorder). time shifting recording A VCR ability to record pro- torque The tendency of a force to produce rotation grams under timer control. about an axis. In VCRs, torque usually relates to the timing the system Ensuring that all of the sync pulses rotational force exerted by the supply and take-up from the various pieces of equipment arrive at the reels. switcher at the same time. total harmonic distortion See THD. tint See Color tint control; Hue; Hue control. touch sensor button A feature found on TV sets and tint control Hue control. VCRs and utilized in conjunction with electronic tun- TIROS Television InfraRed Observation Satellite. One ers and remote control accessories. A slight touch of a series of meteorological satellites carrying IR of one of these buttons may change a programmed equipment and TV cameras. It transmits pictures of channel or another function on the VCR. See Ran- cloud cover, locations of ice floes, and other weather dom access. data. TOV Threshold of visibility, the impairment level be- Title 17 The Federal Bureau of Investigation warning yond which a source of impairment or interference that precedes or follows commercial prerecorded can introduce visible deficiencies in sensitive program material on videotapes and videodiscs. Title 17, US material. Code, Sections 501 and 506, reads as follows: “Fed- trace The image traced out by the luminous spot on eral law provides severe civil and criminal penalties the screen of a CRT. for the unauthorized reproduction, distribution or trace interval Syn.: active interval. See Sawtooth wave- exhibition of copyrighted motion pictures and vid- form. eotapes.” The FBI has been known to investigate track The portion of a moving storage medium, such allegations of criminal copyright infringement. as magnetic tape or disk, that is accessible to a given titler See Character generator, Superimposition. reading device. TiVo™ One brand of Personal Video Recorder (PVR), tracking 1. The method employed by the video play- also called a digital video recorder (DVR). Records back head to follow or track exactly the helical sig- and stores TV programs on a computer hard drive, nal or path encoded by the recording head; the angle allowing users to pause live TV and instant replay, and speed at which the tape passes the video heads. slo-mo, and rewind live or recorded TV. Poor tracking (mistracking) results in video noise TNLCD Twisted-nematic LCD. while complete tracking loss causes picture break- Tomahawk A ship-launched cruise missile that has up. Tracking in a VCR is similar to framing on a movie both a long-range radar terrain-scanning tercom projector. 2. Maintaining the spot of light from the guidance system and near-target video-camera guid- laser accurately on the track of a CD. 3. Movement ance system. Tercom scans terrain features and com- of the whole camera when making a shot. Some- pares its data with a digitized “map” in its computer times called dollying. A tracking shot is a shot taken memory. The video system takes over near the tar- with the camera moving. Sometimes called a dolly get and compares its digitized output with a target shot. photograph in the missile. tracking control A knob or control, usually on the tone 1. In audio, a sinusoidal signal of constant fre- front of a VCR, used to correct video noise, picture quency used for test purposes or to identify circuits. instability, flagging and other video anomalies caused 2. In popular speech, the term is used to describe by tracking problems. For example, sometimes a tape the quality of a musical sound. For example, a cello recorded on one machine will not play correctly on may be described as having a mellow tone. 3. In another of the same format because of the way one photography and TV, the degree of light or shade of VCR records and plays back the diagonal tracks. In an image or an element of an image. other cases, the problem may lie within the tape tone wedge In TV, a test image consisting of a series tensions of the machine, especially at slower speeds, of areas of which the tone varies in steps between or in a defective cassette, both leading to a tracking black and white. Most TV test cards incorporate a error so that an adjustment becomes necessary. The tone wedge that can be used for the adjustment of tracking control lifts or lowers the video heads so receivers. that they track or “read” the signal recorded on the top boost Another name for high frequency boost, a tape. method of improving the resolution of a picture. tracking level meter A VCR feature that displays the

281 tracking shot

strength of the recorded control track signal on vid- converting sounds or images to electrical signals: mi- eotape. Usually, a poor control track affects future crophone or video camera. editing. For example, a weak tracking level produced Trans-Europe Line (TEL) A 140-Mb/s fiber-optic com- by a video camera may result in greater instability munications system connecting Eastern and West- and more glitches. Super-VHS camcorders tend to ern Europe; Deutsche Bundespost Telecom, Bonn, lay down a stronger timing signal than the more Germany. compact S-VHS-C models. A tracking level meter transfer Copy recording on one tape to another tape. may be found on virtually all industrial VCRs designed In video production, a transfer is the process whereby for editing and some top-of-the-line home models. a recording made in one format is played in that tracking shot See Tracking. format and recorded in another format. Running off tracking weight In the now-defunct CED videodisc a VHS copy from a U-matic master is technically a system, the weight of the stylus assembly as it tracks transfer. But since it is going from a higher to lower the grooves of the disc. The CED player operated quality format, it is usually referred to as “making a much like a phonograph—the stylus made physical VHS copy.” Going the other way, however, is a trans- contact with the disc. This differed dramatically from fer. The transfer implies the producer is attempting the LaserVision (LV) videodisc system in that no con- to take a tape of one format and record a copy of tact is made with the disc; instead, a laser beam of that tape in a higher-technology format in a man- light “read” the information implanted into the disc. ner that gives the impression that the original re- Although the tracking weight of the CED system cording is of the higher-tech format. Usually some was only 65 milligrams, the stylus would eventually form of electronic processing, such as time-base have to be replaced while repeated plays would take correction, is necessary to make a transfer, so it is a their toll on both the picture and sound. more involved event, requiring the control room as track intro scan A feature, found on some VDPs, that well as duplication facilities of the house. See also permits the viewer to retrace the contents of a disc Film-to-tape transfer. by moving sequentially through each track and chap- transfer characteristic 1. Of an active device, the curve ter. In the case of combination LD/CD players, the obtained by plotting the output current against the track intro scan reviews the contents of CDs. The input voltage or current. For a field-effect transistor feature is similar to frame/chapter search. the input is taken as a voltage and for a bipolar tran- trailer 1. A bright streak at the right of a dark area or sistor as a current. 2. Of a TV camera tube, the dark line in a TV picture, or a dark area or streak at curve obtained by plotting the output current against the right of a bright part. It is caused by insufficient the light input (the relation between the degree of gain at low video frequencies. 2. A strip of extra- illumination of a TV camera tube and the corre- strong nonmagnetic tape attached to the end of sponding output current under specified conditions). recording tape. Professional/industrial trailers, which 3. Of a magnetic recording system, the curve ob- come in several colors, often have one surface avail- tained by plotting the magnetic flux density against able for writing. the magnetizing force. 4. Of a photocell, graph trajectory In general a trajectory is any path between curves of electrical output vs light (e.g., from laser) two points although intermediate points should be energy input. given to describe complex trajectories. Hence, in the transformation In video compression, a transforma- context of a DVE, a trajectory is created by a series of tion of the values of a group of pixels into another keyframes that have been defined by the operator. set, which can be transmitted with less data. After transaction provider (TP) A company or organiza- transmission, an inverse transform is performed that tion that provides a service enabling subscribers to recovers the original values. make reservations or purchase products and services transient detecting stage A differentiator that is part directly through a videotex and TV stations. Trans- of a color transient improvement circuit. The switch- actional services include banking and shopping. ing stages, which are controlled by transient detect- transceiver A component used in electronic still video ing stages, switch to a value that has been stored at and designed to send images over telephone lines. the beginning of the transients. The differentiating transcoding 1. The conversion of video signals with stages get their signal from the color difference de- different color systems but with the same scanning tecting signal. Used in TVs. standard—e.g., PAL to SECAM or SECAM to PAL. transient response The response of a circuit to a sud- 2. Often used in North America (particularly in Que- den change in an input quantity, such as to a step bec) to mean standards conversion. 3. To convert function. In making the transition from black to one version of MPEG to another—i.e., MPEG-2 to white, the voltage of the video signal changes value. MPEG-4. If the TV set can’t handle these changes properly, transducer (sensor) Any device that converts a non- there is wavering along the edges of certain objects electrical parameter, such as sound or light, into elec- in a picture. For example, a TV set shows the black trical signals or vice versa. In TV, a device for line of a tree separated from the blue of the sky by a

282 transverse recording

white line. Such an error, or artifact, is caused by kinds of interference picked up by the TV antenna less-than-perfect transient response. in the range of 40 to 170 MHz. It consists of a 4 3/8-in transition 1. A vision mixer changeover operation from (11-cm) length of twin-lead-in cable that has a short- one source picture to another picture, or from one circuit at one end and an adjustable ceramic capaci- keyframe to another. 2. An abrupt change of video tor at the other end, taped to the receiver signal level, e.g., “green-magenta transition” in the twin-lead-in cable. center of a color bar pattern. transmission plane The plane of vibration of polar- transitional digital video effects Refers to a series ized light that will pass through a Nicol prism or other of special visual creations that can be generated by polarizer. certain sophisticated devices such as a digital video transmission primaries The set of three color prima- effects (DVE) system. Transitional effects like dissolves ries that correspond to the three independent sig- are used in post-production editing to shift smoothly nals contained in the color TV picture signal. The from one scene to another. Warp, prism, curvilinear, three receiver primaries in the color picture tube form montage, mirror, mosaic, sparkle, trailing, decay, one set. The luminance primary and the two chromi- drop shadow, multifreeze and rotation are some of nance primaries, known as the Y, I, and Q primaries, the more popular effects a DVE system can produce. form another possible set of transmission primaries. These differ from nontransitional digital video ef- transmit button A VCR remote control feature de- fects. signed to send programming information from the transition editing recording Syn.: add-on recording. remote control to a VCR. Ordinarily, to program VCRs transition effects Special effects that occur at the equipped with on-screen displays to record a cer- transition between different video camera shots. tain channel at a given time and day, the TV set must transition status display A professional/industrial be on. However, remote controls with LCD displays switcher feature that permits keying into any TV can be programmed directly, even while in another monitor and presents on screen the operating sta- room, and sent to the VCR by way of the transmit tus of the switcher. Different windows of the video button without going through the TV set. graphic device report various parameters, including transmittance Transmission. the on-air source, source name, preroll name, posi- transmitted-carrier transmission A telecommuni- tion of the automation feature and transition type cation system that uses amplitude modulation of a and duration. Windows can be concealed by the carrier wave in which the carrier is transmitted. Cf. operator. See Switcher. suppressed-carrier transmission. transit time In general, the time taken for a charge transmitter In television, electronic equipment used carrier to cross a given gap. In electron tubes, the to transmit radio-frequency (RF) television signals, time taken by electrons to travel from the cathode modulated by composite video, synchronizing, and to other electrodes. audio information. translation frequency The 2.2-GHz frequency differ- transmitter/receiver system See VCR transmitter. ence between an uplink and downlink signal. transparent 1. Permitting passage of radiation or par- translator station In TV broadcasting, a repeater sta- ticles. 2. See Video monitoring equipment. tion that receives a primary station’s signal, ampli- transponder Part of a communications satellite. Broad- fies it, shifts it in frequency, and rebroadcasts it, cast signals are transmitted from earth to the satel- usually on a UHF channel from No.70 to No.83. See lite where they are then passed through a also Booster station, Frequency translation. transponder and sent back to earth. Each satellite transmission 1. The process of transferring a signal, may have a number of these transponders. One tran- message, picture, or other form of intelligence from sponder can transmit thousands of weather mes- one location to one or more other locations by fi- sages back to earth—simultaneously. But the same ber-optic cable, wire lines, radio, light or infrared transponder can hold only one or two TV signals (IR) beams, or other communication systems. 2. A because of the wider TV band. See also Capture ratio. message, signal, or other form of intelligence that is transverse recording A method of recording that being transmitted. 3. The ratio of the light flux trans- produces tracks across the tape at right angles to mitted by a medium to the light flux incident upon the length of the tape. A video head moves across it. Transmission can be either diffuse or specular. It the tape at a relatively high speed, as the tape moves is also called transmittance. rather slowly past the head mount. This results in a transmission ability The amount of light that a fil- high head-to-tape speed, also called writing speed. ter will allow to pass through it, usually expressed This idea of a moving head led to the development as a percentage. A filter with 80% transmission of a rotating head mechanism. Two heads are re- ability, therefore, will admit 80% of the light while quired for this operation. Head A is recording a track rejecting 20%. on the tape while head B is retracing or returning to transmission-line trap An interference trap that can the top edge of the tape for its next track. When be installed in TV sets to minimize FM and other that position is reached, head A is switched off and

283 trap

head B is switched on. Thus, properly timed switch- phosphor dots repeated many thousands of times ing is an important requirement of the rotating head to form the color-reproducing surface of a shadow and transverse recording process. mask TV display tube. Each dot emits one of the trap 1. A tuned circuit in the RF or IF section of a three primary colors—red, green, or blue—when receiver that rejects undesired frequencies. Traps in scanned by the CRT’s electron beam. The set of three TV set video circuits keep the sound signal out of phosphor dots makes up a pixel, the smallest pic- the picture channel. It is also called a rejector. 2. ture element on the screen. Refers to special circuitry used by a cable company triangulation 1. The process of determining the dis- to lock out certain channels that customers have tance between points or the relative positions of not subscribed to. Traps are installed between the points, by dividing up an area into a series of con- multitap on the feeder line and the cable drop line nected triangles, measuring a base line between two going to the subscriber’s home. Because they are points, and then locating a third point by comput- usually attached to the feeder line above the ground ing both the size of the angles made by lines from near a telephone pole, they are a relatively effective this point to each end of the base line and the lengths antidote to piracy. See also Scrambling. of these lines. 2. The triangles thus marked out. trapezium distortion See Distortion. triangulation comparison circuit In some 3D TV cam- trapping effect In photoconductive tubes, a long-term era systems with laser projectors, a circuit that com- nonlinearly decaying level of charge after each suc- pares the electrical signal outputs of left and right cessive scan. The length of time for retention of this triangulation sensors to form the depth video signal. residual charge will vary with different photocath- triangulation sensor In 3D TV camera systems with ode materials. laser projectors, a sensor that is sensitive only to the traveling shot Moving the video camera about while laser beam, either to the frequency of the laser beam it is recording the scene. Professionals use a dolly or or, if the laser beam is coded, to the coding of the tracks to produce smooth traveling shots. Amateurs laser beam. Used to generate the depth signal (to- can get satisfactory results by simply holding the gether with the second sensor). camera firmly while moving forward or by placing triax camera cable The first color cameras were con- the camera on a small cart with wheels. nected to the control unit with three large, heavy traveling-wave tube (TWT) An electron tube in which cables. With the smaller size, lower power require- a stream of electrons interacts continuously or re- ments, and greater stability of solid-state compo- peatedly with a guided electromagnetic wave mov- nents and the use of photoconductive and ing substantially in synchronism with it, in such a charge-coupled device (CCD) imagers, it has been way that there is a net transfer of energy from the possible to concentrate more of the circuitry in the stream to the wave. The tube can function as an camera head and to reduce the number of connec- amplifier or oscillator at microwave frequencies. tions between the camera head and the camera traveling-wave tube amplifier A broadband micro- control unit (CCU). This made it possible to transmit wave amplifier that includes one or more traveling- all the video, control, and power connections in a wave tubes to provide power output that can exceed single small triax cable. The control signals are digi- 200 W in the frequency range of 1 to 40 GHz. Origi- tally multiplexed, and the video circuits are trans- nally used in satellite transponders, but, as with much mitted by subcarriers. of the electronics industry, a transition has been trichlorotrifluoroethane (TF) A video head cleaning made to solid-state power amplifiers, SSPAs. solvent. It evaporates more quickly than alcohol, leav- treatment A narrative writeup, usually nontechnical, ing no residue that attracts dirt. TF is the most popu- that describes a proposed creative work such as a lar solvent used in video cleaning kits. It is available software application or an audio/video production in liquid form and spray cans. If the spray is used, it segment. is applied to the swab, not directly to the heads. tree network A configuration shaped like a branch- trichromatic camera Camera using the three-color ing tree with one central node. It is characterized by principle (i.e., employing no separate luminance the existence of only one route between any two tube). network nodes. This configuration is presently em- trichromatic coefficient Chromaticity coordinate. ployed in coaxial CATV systems: distribution amps tri-electrode tube A video camera tube that utilizes are installed in multiple stages on trunk lines and three internal lenses, instead of the conventional signals are distributed through branch points. The one, to isolate the three primary colors. Sony’s design resembles a tree: the signals from the Trinicon image pickup tube uses this system. Other headend (the root) are carried to trunk lines (major types of camera tubes include the most widely used limbs) and then through feeder cables (large vidicon and the saticon. branches) to cable drops (small branches), and fi- trigger alarm A video camera feature that alerts nally to the individual converter (leaf) in the home. the user by means of a beeping sound when a triad A triangular group of three small color-sensitive recording begins or ends. This function, sometimes

284 t-stop

listed as beeper feedback, appears on relatively tri-stimulus In color reproduction, a method that uses few cameras. three primary colors or three color signals for image tri-level sync A sync signal that has three levels, and transmission and reproduction. is commonly used for analog HDTV signals. See sync. trolley See Crane. trim To add or subtract from an edit duration using a Propagation of TV signals time code address entry. by sky way through the troposphere or weather- Trinicon® camera tube A video camera tube that forming region approximately 1/2 to 10 miles above allegedly has higher resolution than other tubes. The the earth’s surface, instead of close to the surface Trinicon tube is a single tube system comprised of by ground wave. At distances of more than 50 miles three color filters (primary colors) that separate the from a transmitter, the sky way becomes of increas- incoming light. Used by Sony, it is a modified ver- ing importance because of the marked attenuation sion of the saticon. The average user, however, would of the ground wave. Temperature and pressure varia- probably not be able to detect any significant ad- tions in the troposphere cause the refractive index vantages in any one tube over the others. of the atmosphere to alter, so that high-frequency Trinitron® Tradename; a Sony color picture tube that waves are reflected back to earth, causing fading has its phosphor screen deposited in narrow vertical and interference. stripes instead of dots. The mask in front of the trucking Moving the camera left (truck left) or right screen is a grille of vertical slots instead of a shadow (truck right) on a tripod with a dolly, or moving your mask with round holes. A single electron gun emits body while holding a portable camera. three beams, one for each primary color, in a hori- truck left See Crab; Trucking. zontal line. The phosphor stripes are very narrow truck right See Crab; Trucking. compared to the beams, so each beam spreads true color True color means that each sample of an across two slots in the mask. The angle at that a image is individually represented using three color beam enters a slot determines which color of phos- components, such as RGB or Y’CbCr. In addition, phor stripe it hits. the color components of each sample may be inde- triple beats In CATV, third order distortion products pendently modified. True-color (24-bit) computer of the f1 ± f2 ± f3 type, where f1, f2, f3 are video images are composed by dedicating 24 bits of carrier frequencies containing . memory to each pixel, 8 each for red, green, and These triple beats are caused by the nonlinearities blue components. of the amplifier’s transfer characteristic. All of these truncation 1. Loss of outermost side frequencies of sum and difference frequency components increase an FM signal due to filtering. Shows as “tearing” with the number of carriers carried on the cable. effect of noise on video transients, sharp vertical The greater the bandwidth, the more the channels edges. 2. In video compression, the technique of and the greater the number of beats. When these reducing the number of bits per pixel by throwing beats increase in number, amplitude picture impair- away some of the least significant bits from each ment is evident. Beats that fall within a channel space pixel. are called composite triple beats for fully loaded cable trunk line (TL) The main highway of a cable operation systems. in a tree network. The TLs begin the distribution of tripler A solid-state component made up of capaci- the electronic signals from the headend to the tors and diodes to triple the applied RF voltage from subscriber’s TV set. Consisting of large coaxial cables, the flyback or horizontal output transformer. In the 3/4 to 1" in diameter, they carry the signal to smaller TV chassis the horizontal output transformer and feeder cables, that continue the distribution to even the high-voltage can be molded into one smaller cable drop lines, that connect to the component. subscriber’s home. Bridging amplifiers are placed at tripod A three-legged stand on top of which a cam- periodic intervals (every 1/3 to 1/2 mile on TLs) to era is mounted. Video tripods differ from those de- boost the original signal and correct the problem of signed for film cameras. A good tripod consists of attenuation. sturdy legs that can contract to a size small enough t-stop A rating of a lens in terms of its ability to trans- to be considered portable, a center column that can mit light; the transmission ability, or transmission be raised or lowered, supports that protrude from stop, of a lens; more exact in terms of a lens trans- the base to the legs and a camera mount with pan mission ability than an f-stop rating, but no more (left/right) and tilt (up/down) controls. More costly helpful than the f-stop when working with a video and professional tripods feature fluid heads, instead camera; used on some lenses in motion picture and of the conventional countersprings, for controlling still photography in place of f-stop. The t-stop num- the pan and tilt controls. ber (the t stands for transmission) indicates the ex- tripod head The top portion of a tripod where its legs act amount of light reaching the film or tape, meet and the camera is mounted; friction- or fluid- whereas the f-stop number indicates the amount of head tripod designs are available. light reaching the lens.

285 TT

TT See Teletext. TV antenna See Antenna. TTL optical finder See Through-the-lens optical TV broadcast signal The composite RF signal that is viewfinder. transmitted from TV stations. These signals are tumble A combination of gradual vertical squeeze and picked up by a TV antenna, pass through the an- mirror effects that cause the displayed picture to tenna cable to the TV tuner that is used to select the appear as though it is rotating about a horizontal channel or frequency. The signals are amplified and axis. Syn.: turn. converted to a lower frequency signal by the tuner tuner The first stage of a TV set that is used to select a so that they can be fed to the TV picture tube. The particular broadcast channel. There are two types broadcast signals are then divided into their audio of electronic tuners: the analog type that are adjust- and video parts by a video detector and again able and the frequency-synthesis tuners that are pre- amplified. set for all cable-ready channels. A TV tuner TV/cable tuner A device to convert a non-cable-ready commonly contains only the RF amp, LO and mixer TV into a cable TV. stages, whereas a radio tuner also contains the IF TV camera Video camera. amp and second-detector stages. Also called front TVCR A TV set/videocassette combination, sometimes end. described as a TV/VCR. Some models are quite por- tuner/controller A unit that permits owners of pro- table, offering a 3.3" screen and weighing only five jection TVs to receive cable or broadcast signals with- pounds. Other TVCRs have a 19" or 27" screen with out the use of a VCR tuner. The tuner/controller often hi-fi stereo sound. comes with remote control; on-screen audio and TV Crossover Link A type of enhancement that noti- video control; and several inputs and outputs, in- fies users that there is enhanced or Web content cluding those for S-video and RGB, the latter for associated with a program or an advertisement. A driving video projectors. TV Crossover Link appears as a small icon in the cor- tuner/timer The second half of a two-part portable ner of the TV screen at a point in time determined VCR system. The tuner/timer permits recording off- by content producers. Clicking the link displays a the-air programs at predetermined times by pre-set- panel, giving the viewer an option to go to the con- ting the timer. This unit usually remains behind while tent enhancement (Web site) or continue watching the VCR deck, that contains the battery, is taken TV. If the viewer chooses to go to the Web site, the into the field along with a video camera. Some receiver connects to the site, while the current pro- manufacturers have sold each unit separately while gram or advertisement remains on-screen. Pressing others offered only the complete system. Tuner/tim- the View button on the remote control or keyboard ers have virtually faded from the home video mar- returns to TV viewing. The term is a trademark of ket with the introduction of the one-piece the Microsoft Corporation. camera-recorder, or camcorder. TVI TV interference. turn See Tumble. tvl See TV line. turnaround Flipover. TV line (television line, tvl) Commonly used measure Turner, Ted Businessman, promoter, owner of the At- of spatial frequency of periodic pattern in a TV pic- lanta Braves, TV station owner. He built his Atlanta ture expressed as a ratio of picture height to the station, WTBS-Channel 17, into a superstation in half period of the pattern. E.g., for 625/50/2:1 scan- 1976 by placing its signal on RCA’s satellite, Satcom, ning standard a 1-MHz video signal produces a pe- enabling WTBS to be picked up by virtually any cable riodic TV screen pattern with a spatial frequency of system in the country. He also introduced the first about 78 tvl . 24-hour all-news cable station, Cable News Network TV line number See Aperture response. (CNN). TV memory See Memory. turnstile antenna An antenna that consists of one or TV monitor See Monitor, Monitor/receiver. more layers of crossed horizontal dipoles on a mast, TV receiver Also called TV set. A unit that collects RF usually energized so the currents in the two dipoles broadcasts and reproduces them in their original of a pair are equal and in quadrature. It is used with audio and video forms. A TV receiver has a tuner for TV, FM, and other VHF or UHF transmitters to ob- channel selection. Radio waves transmitted from a tain an essentially omnidirectional radiation pattern. TV station enter the TV set as an RF signal through turret tuner A tuning device used in a TV set. It con- the antenna input. The composite signal carries tains a set of resonant circuits each tuned to the video, audio and sync information and is separated frequency of one of the separate broadcast chan- by various components. Each channel signal enters nels. One or more manually operated switches, an IF amplifier that increases the signal that then termed band switches, allow the particular circuit travels to a video detector where it is separated into corresponding to the desired channel to be selected a video and audio signal (the separation is also pos- by the user. sible after a tuner). The video portion is carried to a TV Television. video amplifier for more processing until it ends up

286 two-channel sound

displayed on the CRT. The audio is sent to its own twin-interlaced scanning The lines of each vertical amplifiers and finally to the speaker. sweep fall midway between those of the previous TVRO A TV-Receive-Only satellite system. Usally refers sweep—process by which adjacent lines in the to the large-dish systems as opposed to the small- scanned image belong to alternate fields—i.e., line dish Ku-band DSS systems. TVRO systems receive 1, line 3, line 5, etc., form part of the odd field, and TV signals from C-band satellites. lines 2,4 and 6 form part of the even field. Com- TV set TV receiver. pared with a sequential system of the same picture TV signal generator Signal generator. frequency and number of lines, a twin-interlace sys- TV still See Memory. tem requires only half the transmitted bandwidth, TV storyboard Sheets of paper with blank TV screens but it also conveys only half the picture informa- on them; used for roughing out the action of a tion. Its purpose is to double the effective picture program. rate and thus raise the flicker frequency from an TV trigger Video trigger. unacceptable 25 or 30 Hz to an acceptable figure TV/VCR combo A hybrid TV and VCR. Today, TV/VCR of 50 or 60 Hz. combos most generally come in 13-inch and 19/20- twinlead TV hookup cable that consists of two wires inch models, usually with two-head VCRs. separated a certain distance by a plastic spine. It TV/VCR selector A control on a VCR used to choose needs no connectors and is less costly than the 75- either the antenna or the VCR source programming. ohm coaxial. The 300-ohm twinlead is more sus- The selector permits (1) watching regular TV with ceptible to radio interference and has a propensity the VCR off, (2) taping a TV program while watch- for more signal loss than its counterpart. It is also ing another, (3) taping a TV program while watch- available in a shielded version that better maintains ing it, and (4) playing a recorded videotape. With a signal quality. recorded tape set in the VCR, the machine will au- twin lens scanner In a telecine (film scanner), two tomatically switch to VCR mode when Play is separate lenses may be used to focus two separate engaged. images of the scanning tube onto separate places. tweaking A term used for the technical modification This is done to achieve double scanning of a frame of recording devices in which the automatic gain of film. control (AGC) is deliberately bypassed. Since the twisted-nematic LCD (TNLCD) A display containing AGC attenuates and boosts all sounds, it may present a liquid crystal whose twisted-nematic molecules problems in certain situations. For example, if a sub- align on a helical axis in the absence of an electric ject being interviewed is prone to long pauses, the field, twisting polarized light up to 90 degrees. When AGC will boost these intervals, causing extraneous the liquid crystal is channeled on its new axis through sounds to be recorded. In addition, when the sub- an exit polarizer, the viewer sees a bright background ject continues the interview, his remarks will begin region. With an electric field across opposing elec- at an excessively high level. Tweaking restores con- trodes, the crystals align themselves parallel to the trol of the audio level to the operator of the VCR or field, and entering polarized light is blocked by the other recording unit. exit polarizer. A dark region appears—typically dots tweens Jargon term to designate frames computed (pixels) or alphanumeric segments. The electrodes by a computer animation workstation or digital video can be organized so that the OFF state corresponds effects equipment to fill the time intervals between to the dark background region and the ON state to actual defined or selected keyframes. In the case of bright picture elements. a DVE, trajectory settings are used to enable the cal- twist pin A thin metal guidepost that works in con- culation of tweens. Syn.: in-betweens . junction with a tape guide at different stress points twilight mode In camcorders, a mode to record night of the tape path, positioning the tape at the same views, neon signs or fireworks. angle as the head drum. Twist pins are usually lo- twinax Twinaxial cable made up of two central con- cated next to tape guides. ducting leads of coaxial cable. See Twinaxial cable. two-channel sound On a VCR, the ability of the ma- twinaxial cable Two insulated conductors inside a chine to record and play back audio on two sepa- common insulator, covered by a metallic shield, and rate tracks. Of course, this is the basis for stereo enclosed in a cable sheath. Because it carries high sound in VCRs. Two-channel sound also permits frequencies, twinaxial cable is often used for data audio dubbing in stereo. Mono sound is produced transmission and video applications, especially for by a single sound track (in home video, the audio cable TV. track is located near the top edge of the videotape). Twincam Dual-lens camcorder, Sharp. To obtain two-channel sound, that portion of the twin-deck domestic VTR A VTR that combines most tape allotted to audio is divided into two, one part of the facilities of two standard domestic VHS ma- for the left channel and the other half for the right chines neatly and conveniently inside a single case. channel, with a small separation band between the twin-digital tracking Digital tracking. two tracks. Because each audio track is so small,

287 two-eye picture image

the sound quality would suffer without the aid of scans, respectively. Thus, a second’s worth of film some noise reduction system. contains 12 frames scanned twice, making 24 plus two-eye picture image See Three-dimensional 36 or 60 fields. Also called 3:2 pulldown. picture image. two-tube color camera A video camera with one two-field metering system Refers to an electronic vidicon tube dedicated to luminance (black and process employed by some camcorders as a means white brightness values) and the other to color (hue of providing a balanced exposure. The system in- and saturation of color). volves one separate reading of the entire field and TWT See Traveling-wave tube. another reading of the central zone. Both are then Type B video recorder See Type C video recorder. automatically calculated by the camcorder to pro- Type C video recorder The standard of broadcast- duce an accurate exposure. level analog composite video recorders. Uses 1" two-field picture One complete frame of an inter- video tape in a reel-to-reel format. This equipment laced TV picture is made up of two fields, normally is the workhorse of broadcast TV around the world called odd and even. These two fields are interlaced and delivers the best analog recording performance to form a complete picture. available today. The basic Type C machine is a large two-inch See Quadraplex. unit weighing somewhat more than 100 pounds and two-shot A photograph, motion picture, or close-up intended for fixed or transportable use. The Type C TV scene that focuses on two persons or objects. recorders will deliver good performance after three two-thirds-inch vidicon A vidicon with a target area generations and are usable up to 5 or 6 genera- 2/3" in diameter; the most commonly used vidicon tions. Another broadcast-level format, which is in portable video cameras. somewhat less used in the USA but is found exten- two-three-two-three scanning Method of display- sively in Europe is the Type B system. The Type B ing a 24-fps film on a 60-field TV system (the North recorders also use 1" tape, but their format is differ- American standard). Successive frames of the film ent in a way that allows smaller machines to be built. are exposed to two field scans and then three field Type B performance is equivalent to Type C.

288 U

U CATV superband channel, 282-288 MHz. Ultimedia IBM’s word for the ultimate in multime- UCM Ultra Compact Machine. A 1/2" home video cam- dia, combining sound, motion video, photographic era developed chiefly by Japanese manufacturers in imagery, graphics, text and touch into a unified, natu- the early 1980s. Small and light, UCM cameras were ral interface. Coined in 1992. one-piece units, combining camera and recorder, and See UHF. had a one-hour recording time. A small videocas- ultra hi-res Ultra high resolution. Properly speaking, sette fit directly into the camera, which produced a the term should be for monitors with resolutions of picture of satisfactory resolution. This mini- 1600 x 1200 or better, but it is sometimes used to camcorder differed from Technicolor’s CVC (Com- describe monitors with 800 x 600 resolution and pact Video Cassette), which came out at about the above. same time but was a two-piece unit. These two sys- ultrasonic A reference to signals, equipment, or phe- tems were incompatible with each other and the nomena involving frequencies just above the range VHS-C format, another mini-system which used a of human hearing, hence above about 20 kHz. small VHS cassette that fitted into a conventional ultrasonic delay line A delay line that depends on VHS holder for playback on any VHS machine. the propagation time of sound through a medium UCT UltraClean Technology. to obtain a time delay of a signal. UHF A band of frequencies extending from 300 to 1000 ultrasonic light valve A device that can be used to MHz. In TV, refers to the ultra high frequency chan- transmit video information. It consists of a piezo- nels 14 through 83. Found on most TV sets and VCRs. electric quartz crystal immersed in a transparent liq- UHF connector Standard type of video-in/video-out uid. The crystal is excited by ultrasonic-frequency jack; also commonly found on professional moni- alternating current and the resulting mechanical vi- tors; used to carry either composite or noncomposite brations set up compressive waves in the liquid. If video signal. the crystal is fed a modulated video signal, corre- UHF converter An electronic circuit that converts UHF sponding changes in the compression result. The signals to a lower frequency to permit reception on system acts as a liquid diffraction grating to a light a VHF receiver. It converts UHF TV signals to VHF beam that is shone through it. The video informa- signals for reception on VHF TV receivers. tion may be recorded on photographic film or de- UHF taboos A set of NTSC transmission prohibitions tected with a suitable . based upon certain UHF TV channel combinations Ultrawideband (UWB) An emerging technology us- and transmitter mileage separations that the FCC ing the transmission of very short impulses determined are required to prevent interference to of radio frequency (RF) energy whose characteristic TV receivers; most of the taboos are caused by spectrum signature extends across a very wide range receiver characteristics. of frequencies. UWB systems have shown UHF translator A TV broadcast translator station that promise for application in a number of telecommu- operates on a UHF TV broadcast channel. nications functions, including short-range broadband U-load The Beta format loading system. The video- wireless networks. In 2002 the FCC approved tape is threaded around the video head drum in a U limited use of unlicensed wireless systems that trans- shape. A typical Beta VCR withdraws about 24" of mit high-speed data using UWB. videotape from the cassette, wraps the tape around U-Matic A 3/4" video cassette system designed by the head drum and directs it in a U-turn around vari- Sony, 1971. In professional-level, the format uses a ous tape guides before it returns to the take-up reel cassette with 3/4" tape; machines come in rack- in the cassette. The VHS format uses the M-load mounted, tabletop, and portable configurations. The system. 3/4" system uses a method of getting the compos- U loop The shape in which tape is laced around the ite signal onto the tape that requires that the lumi- heads in U-Matic and Beta VCRs. nance and chrominance be taken apart and then

289 unassigned bits

put back together inside the recorder. Doing that to supercapacitor, two very dependable memory a composite signal introduces some inherent degra- backup methods, they usually offer less storage time dations so that the picture quality of the 3/4" sys- than the more costly UPS device. tem is not as good as Type C, particularly with respect unique hue See Variables of perceived color. to color sharpness and luminance bandwidth. The universal lens mount A uniform bayonet-mount stan- 3/4" system typically can go only two generations dard designed for interchanging lenses regardless with acceptable pictures. of the camcorder format. Japanese manufacturers unassigned bits See Time code word. of VHS, VHS-C and 8mm camcorders early in 1990 unattended recording A feature, found on virtually decided to turn out interchangeable lenses and all VCRs, which permits the machine to automati- camcorders containing microprocessors which would cally record a program at a pre-set time. This is per- permit the camera to control the autofocus, power formed by setting the digital clock and zoom and auto-iris of any lens. programmable timer. Unattended recording can re- universal remote control A single control unit that fer to programming any home VCR or portable can operate a variety of components, including those model with a built-in automatic timer capable of of different brands. The universal control has the taping one event within a 24-hour period or record- capability of “learning” different pulse patterns, ing up to 8 events from as many channels over a which it then transmits to various equipment. This 12-month period. See Time shift. is accomplished by placing the universal control next underbunching A condition that represents less than to each remote control from other units. The uni- optimum bunching in a velocity-modulation tube versal control then “listens” and memorizes all the such as klystron. necessary commands of each remote. A built-in sen- underlay data In Digital Video Interactive (DVI) tech- sor in the TV set, VCR or other unit then translates nology, data contained in a separate stream in an these pulse patterns into electrical signals so that audio-video subsystem (AVSS) file, intended for use individual instructions can be executed. Some VCRs for any purpose that requires data retrieval in syn- provide several built-in weekly timers and can store chronism with the frames of video. An example of up to 38 sequences of up to 14 commands each. underlay data is the time code that must be stored See Multi-purpose remote control, Remote control, with each frame of an AVSS file created by Real- Unified remote control. Time Video (RTV). universal VHS VCR A VCR, in the VHS format, de- underscan A condition that occurs when an image signed to record and play back different broadcast does not fill the entire screen. An underscanned pic- standards of tape. In addition, the universal unit can ture has a black border at the edges of the screen convert one standard to another so that the signal where the image normally extends. This is some- can be duplicated on another machine. One could, times done deliberately to make certain that no part for example, copy a tape encoded with the PAL stan- of the picture is lost. dard by playing it on the universal unit which would unexcited field brightness Syn.: dark field bright- deliver an NTSC signal to another VCR with the NTSC ness. The brightness of the kinescope when it is standard. Although there have been other multiformat turned off; this is primarily the result of reflection of VCRs, none have been able to offer all the functions ambient light from the picture tube face. of the universal VCR. unidirectional microphone A cardioid-type micro- up converter An electronic device which changes or phone designed to minimize unwanted sounds from “converts” VHF, midband and superband cable TV behind and beside the mic. signals to conventional UHF channels. The converter unified (multi-purpose, universal) remote control permits a programmable VCR to record all channels A single control unit designed to operate several dif- including those on CATV. For example, midband ferent components of the same brand, including a cable channels A through I on a cable box now be- TV set, DVD player, VCR, LP turntable, stereo amp, come channels 47 to 56 on UHF while superband AM/FM tuner, an audio cassette deck and a CD letters J-R are translate into UHF numbers 63-71. player. See Multi-purpose remote control, Remote Also known as block converter or cable converter. control, Universal remote control. up converting A process that increases the number of uninterrupted power supply (UPS) An alternative pixels and/or frame rate and/or scanning format used method of assuring that a VCR (or other electronic to represent an image by interpolating existing pix- device) will operate during unattended recording els to create new ones at closer spacing. The pro- even after a power failure. The UPS unit is an exter- cess does not actually increase the resolution of the nal accessory designed to sense power loss, in which image. Up converting is done from standard defini- case it automatically becomes active and provides tion to high definition. the necessary power to keep a VCR running for a uplink The radio or optical transmission path upward limited time. Although most VCRs come equipped from the earth to a communication satellite. The with either a built-in nickel cadmium battery or a return path is the downlink. Also the component of

290 UXGA

a satellite TV system on earth which transmits the addition to simultaneous retransmission of over-the- original signal to the satellite. The uplink signals that air programs to 10,000 or more subscriber termi- are transmitted usually range from 5.9 to 6.4 GHz, nals with two-way transmission capabilities. with each channel requiring a bandwidth of 40 MHz. URC Universal remote control. Since the difference in the range amounts to 500 user bits An additional encoded information for users MHz, there is room for 12 satellite TV channels. The of time code to enter their own information. It may spherical dish that receives the return signal from contain date of shooting, shot or take identifica- the satellite is called the downlink antenna. tion, reel number, etc. upper sideband See Carrier wave. Uvicon A TV camera tube that has a conventional vidi- UPS Uninterrupted power supply. con scanning section preceded by an ultraviolet-sen- upstream channel The band of frequencies on a CATV sitive photocathode, an electron-accelerating channel reserved for transmission from the user to section, and a special target. the CATV company’s headend. UWB See Ultrawideband. upward modulation (US) Positive modulation. UXGA Ultra Extended Graphics Array. Computer graph- urban-type CATV A CATV system which provides five ics display standard offering a resolution of 1600 x or more channels of locally originated programs in 1200.

291 V

V 1. Vertical. 2. VHF. 3. CATV superband channel, varactor tuner is sometimes blocked from receiving 288-294 MHz. mid- and super-band channels by a few cable TV VAD Value-added data. A communications network systems that employ single conversion block with additional data services. Cf. VAN. converters. value-added network (VAN) A service (e.g., video- varactor tuning Capacitive tuning employed in TV tex), provided through telecommunications, for receivers and VCRs, in which the variable capaci- which a charge is made, thus providing additional tance element is provided by a varactor. value to the basic network technology. variable audio line output A VCR remote control VAN Value-added network. VANs are communications feature that permits the user to control the volume services that, as well as transmitting data via a com- of several TV sets along with the TV set connected mon carrier, offer some sort of extra (added-value) to the VCR. This feature is usually restricted to uni- facility, such as a particular sort of software. fied remote control units. Van Allen belts Belts of high-energy radiation encir- variable audio output A TV monitor/receiver feature cling the earth, important in satellite communica- designed to control the volume of the unit even tions because they may damage electronic when it is connected to an external stereo amp and components. speaker system. Variable audio output can be oper- VAPI Video Application Programming Interface. The C- ated by the TV’s remote control pad. language programmer’s interface for DVI technology. variable bit rate Variable bit rate (VBR) means that a vapor deposition A technique of placing magnetic bitstream (compressed or uncompressed) has a oxides on tape without the use of a binder, result- changing number of bits each second. Simple scenes ing in fewer dropouts, etc. Evaporated metal is can be assigned a low bit rate, with complex scenes placed on the backing while in a vacuum. This pro- using a higher bit rate. This enables maintaining the cess combines metal foil with the backing, eliminat- audio and video quality at a more consistent level. ing the binder on which oxide or metal particles are variable-d See Super-cardioid. normally placed. Doing away with the binder results variable-focal-length lens A TV camera lens system in a stronger, much thinner tape, providing longer whose focal length can be changed continuously lengths for extended playing time. In addition, va- during use while maintaining sharp focusing and a por deposition offers the potential for a higher den- constant aperture, to give the effect of gradually sity of magnetic material, leading to better moving the camera toward or away from the sub- performance. ject. The Zoomar lens is an example. vaporware Software or hardware that is talked about, variable-length Huffman coding In HDTV, a coding promised, or “hyped” before it is completed or on to reduce the data rate by assigning short code words the market. to certain values in the data stream that occur more varactor Variable reactor. A semiconductor diode or often than others. Longer code words need be used operated with reverse bias so that it only for values occurring less frequently. An example behaves like a voltage-dependent capacitor. Also of that technique can be seen in the International called varactor diode, , varicap diode. Morse Code where letters A, E, I, M, N, and T are varactor diode Varactor. represented with just one or two dots or dashes. By varactor tuner A tuner that uses the change in ca- contrast, less frequently used letters (e.g. J, Q, and pacitance of varicap diodes to select a desired sta- X) and numbers are assigned four or five symbols. tion. On some VCRs, a feature that, among other variable microphone A microphone with a number things, permits tuning in midband cable TV chan- of ports in its casing, designed to correct the prox- nels D through I on the high-band range. In some imity effect and to produce a super-cardioid pickup cases, the VCR can tune in as low as channel B and pattern. as high as channel I of the mid-band channels. A variable power zoom lens Zoom lens.

292 vaults

variable slow motion A feature of many VCRs that appears to be coming from the direction of a color permits changing the rate of speed of the slow patch is called the luminosity of the color, but the motion control—usually starting from freeze frame. proportion of total light that appears to be reflected The result on the screen is often accompanied by by the area of color seen is called the lightness of the various noise bars, except in some VCR models that color. Luminosity ranges from total darkness up to offer variable noiseless slow motion and other ma- dazzling or blinding light, and applies to any perceived chines with digital effects. Slow-motion playback patch, including a primary source of light. Lightness speeds often range from 1/30 to 1/6 of normal ranges between extremes of absolute black (seem- speed. Variable speed slow motion, as it is some- ing to reflect no light) and absolute white (seeming times called, was first introduced by JVC. See Slow to reflect all the light); it applies only to illuminated motion. objects, or secondary sources, and can be assessed variables of perceived color The appearance of col- only where colors can be related together with some ors can be described and ordered in terms of three standard. The moon, for example, though a second- independent variables: hue, saturation, and bright- ary source, is unrelated to other objects and does not ness. Three variables are necessary and sufficient, look at all gray; in comparison with the sun it merely so the range of perceived colors may be represented appears to be rather dim, with a low luminosity, and by a 3D spatial co-ordinate system. it is not directly perceptible that this is partly because Hue: Hue is a variable describing the similarity of it has a rather low reflection factor. a color to one in the series ranging circularly through variable speed display Variable speed playback. red, yellow, green, blue, purple and back to red. variable speed playback A DVD, VCR, and videodisc Colors either have a hue that can be fitted some- player feature that allows the viewer to control slow where into this series (e.g., flesh pink: a yellowish- motion to a fraction of a second or view fast play at red hue; tobacco brown: a reddish-yellow hue; olive several times the normal speed. Variable speed play- drab: a greenish-yellow hue; etc.), and are called back, also known as variable speed display, performs chromatic colors; or they have no hue at all (black, other special-effects tasks such as advancing one white and gray) and are called achromatic colors. video frame at a time. For any point in the hue sequence, there is another variable speed search A VCR feature that permits that is least like it, and opposite to it in character; steady images during the searching process at dif- such pairs of opposite hues are loosely called comple- ferent speeds. The results of special electronic cir- mentary colors. Two pairs of opposite hues (red and cuitry and uniquely designed video heads, variable green, blue and yellow) suffice to define any hue, speed search gives the viewer the choice of moving much as directions are defined by the cardinal points from about 3 to 21 times the normal speed—in ei- of the compass. These four are called unique hues. ther direction—while retaining a stable picture. Saturation: This is the variable that describes the variable speed shutter A video camera feature that position of a chromatic color in a radial series in terms allows the camera user to select a setting commen- of its distance from the nearest achromatic color— surate with the action of the subject in different light- in other words, its difference from gray. Neutral or ing conditions. Some variable speed shutters range truly achromatic whites, grays and blacks have zero from 1/60 to 1/4000 of a second. The faster the saturation; yellowish whites, greenish grays and blu- shutter, the sharper or clearer the moving subject ish blacks, etc., have very low saturation. Dull, gray- will appear on screen. ish and pale colors have moderately low saturation, variable window filter A noise reduction device de- whereas vivid and brilliant colors have high satura- signed to eliminate hiss. The filter permits loud sound tion. Chroma refers to the distance from gray, taken (which covers hiss) to pass through, but when sound as a measure of the amount of coloredness of the is low and hiss is detectable, part of the treble range color. Sometimes the word saturation is restricted is cut. to mean the proportion of coloredness to varicap Also varactor, varactor diode, varicap diode. uncoloredness in the color; in these terms, when an In TV set/VCR tuners, a variable tuning element in object is moved into shade, the saturation of its color both VHF and UHF local oscillators. remains the same but the chroma is reduced, be- varicap diode Varicap. cause the object now appears less colorful. VASS VHS address search system. An electronic index- Brightness: The position of any color in a vertical ing system that marks videotape during recording series on a scale from darker to lighter is called bright- or playback so that the viewer may later quickly lo- ness. It can be found by comparing the color with cate specific points on the tape. See Address search, the nearest one of a series of achromatic colors. Con- Index search. sideration of this variable leads at once to the con- vaults Storage places for long-term and archival keep- cept of light as something that shines through space ing of videotapes. Vaults are of fireproof construc- and makes objects visible—more light makes every- tion, and are either provided with means of thing look brighter. The total amount of light that temperature control and humidification, or are so

293 VBI

situated that these factors remain as constant as nate second generation (copy) losses including pic- possible. ture sharpness and audio crispness. VBI Vertical blanking interval. In interlaced NTSC, an VCR modification See Modification kit. interval that comprises 21 lines. Each line arrives in VCR PLUS+ Also VCR Plus. A device for unattended two 1/60-second stages, or fields, totaling 42 of the recording. The compact gadget operates a VCR au- 525 horizontal scan lines in a 1/30-second frame of tomatically and—if applicable—a cable tuner for un- NTSC video. The VBI is used for carrying close-cap- attended recording. The device uses a short tioned signals for the hearing impaired. Digitized numerical code printed with the show in local pro- data can also be inserted into the VBI for transmis- gram listings. At the proper time, the VCR Plus+ will sion at rates greater than 100,000 bps. Information generate IR signals to power up a VCR, tune to the services such as stock market quotations and news correct channel and start recording. offering are available via the VBI of a CATV signal. VCR transmitter A device to send a signal from a The data embedded in the VBI signal is retrieved VCR in one room to a TV set in another; 902- to from a standard cable or satellite receiver wall out- 928-MHz UHF frequencies, range of roughly 100- let by a receiver set, that connects to a RS-232 port 200 feet. on a microcomputer. Software packages then allow VCR/TV selector See TV/VCR selector. subscribers instant access to the information, which VCS Video computer system. may be displayed in a number of formats. Also VCXO Voltage-controlled crystal (X) oscillator. known as field suppression. VDA Video distribution amplifier. VBR Abbreviation for variable bit rate. VDP Videodisc player. VC-C1 Communication video camera; Canon. It fea- VDT Video display terminal. A data terminal with a TV tures a motorized pan/tilt mechanism in a portable screen. Another name for computer monitor package. The camera’s multiple parts connect to a (Europe). desktop computer using the built-in computer in- VDU Visual display unit. terface, or with an IR remote control. Up to six posi- vector A quantity in the visual (video) telecommunica- tions can be set—e.g., to highlight certain speakers tions industry that describes the magnitude and di- at a conference. rection of an object’s movement—for example, a VCD Abbreviation for VideoCD. head moving to the right. See Vector image. VCEP Video compression/expansion processor chip. vector assignment Operation of signal post-process- V-chip See EIA-744. ing in a motion estimator that attributes motion VCO Voltage-controlled oscillator. vectors to pixels by creating boundaries around sets V-CORD A now-defunct VCR system introduced by of pixels having the same motion. Sanyo in the late 1970s. Because it had its own vid- vector image Image based on lines drawn between eocassette format that was incompatible with ei- specific coordinates. In contrast, a raster image is a ther Beta or VHS, it failed to win consumer approval bit-mapped (i.e., bit-drawn) image. A vector image and was dropped by the company. can easily be converted to a raster image, but it’s VCP Videocassette player. much more difficult to go from a raster image to a VCR . vector image. Some storage systems now store im- VCR-2 A dual deck videocassette machine consisting ages as combination raster/vector. of two VCRs. It allows convenient dubbing and vid- vectorscope A piece of equipment that shows a eotape editing for the home video buff. The pat- graphic display of the color portion of the video sig- ented device has two loading slots, side by side on nal. See Color vectorscope, Oscilloscope. the front panel. A blank tape is inserted in one slot veejay Video disc jockey. and the tape to be copied in the other. Punching a velocity-modulated scanning An electronic tech- button marked “Copy Tape” starts both cassettes nique designed to increase the sharpness and con- rolling. trast of a TV monitor/receiver image. This is VCR deck The unit of a two-piece portable VCR that is accomplished by means of a series of electromag- taken into the field and to which a video camera is netic coils encircling the neck of a CRT so that the usually connected. It contains the videocassette speed of the electron beam is altered. By changing housing; operating keys such as Play, Stop, Eject; this speed, the scanning process allows the beam tape counter; tracking control; and other essential signal, which must pass from black to white to pro- elements that affect the tape movement, recording duce image contrast, to remain longer on white. and playback. The second unit, that usually remains Variations of velocity-modulated scanning, or velocity behind, is known as the tuner/timer. With home scan modulation as it is sometimes called, include video systems, the one-piece camcorder has virtu- delay line aperture control and horizontal image de- ally replaced the two-piece video camera. lineation. VCR dubbing enhancer A device to boost video sig- velocity modulation The process of periodically al- nal for improved results when dubbing. Helps elimi- tering the velocity of an electron stream by subject-

294 vertical lock

ing it to a high-frequency electric field that alter- that, when received by a VIR-equipped receiver, helps nately accelerates and decelerates the beam. If the to automatically control both tint and color. The VIR period of the variation is comparable with the tran- signal, developed in 1977 by GE, is broadcast on sit time of the electrons in the space concerned, the one (usually on line 19) of the vertical blanking in- electrons subsequently gather into bunches. Bunch- terval lines. It contains a color reference bar, color ing makes possible microwave amplification and os- sync, a black level reference and the horizontal sync cillation in klystrons and traveling-wave tubes. pulse. The appropriately equipped receiver matches velocity scan modulation See Velocity-modulated its red and blue color and black level with those of scanning. the incoming signal and automatically eliminates any vertical blanking Blanking of a TV picture tube dur- color distortion. ing the vertical retrace. vertical interval signaling (VIS) Digital encoding of vertical blanking interval (VBI) The brief time inter- the transmission mode in the vertical sync portion val between TV fields or frames required for the scan- of a slow-scan TV (SSTV) image. This allows the re- ning electron gun to retrace from the bottom of the ceiver of a picture to automatically select the proper image to the top to begin scanning the next field or mode. This was introduced as part of the Robot frame. It is the fraction of time during broadcasting modes and is now used by all SSTV software de- and playback of videotape in which the screen goes signers. blank, which is the time the VCR switches from one vertical interval switcher A switcher that delays cuts video head to the other. This interval is impercep- between video sources until the entire system is in ver- tible to the viewer but important in electronics. For tical blanking. Since vertical blanking happens 60 times example, during freeze frame special circuitry moves a second, the delay is very small and imperceptible to the tape so that any noise bars are hidden during humans, but it ensures sharp, clean cuts every time. the vertical blanking interval. See VBI. Anything that is going to be switched for use on the vertical centering control 1. The centering control air must go through a vertical interval switcher. provided in a TV set to shift the position of the en- vertical interval switching A method of switching tire image vertically in either direction on the screen. video signals in a special effects generator (SEG); 2. A feature found on waveform monitors designed this replacement of one signal with another takes to place blanking at zero (0) IRE so that accurate place during the vertical retrace period. waveform interpretation can be attained. Vertical vertical interval test signals See VITS. centering control is a basic function of portable vertical interval time code (VITC) In video, a special waveform monitors made for field use. signal recorded during the VBI. One of its uses is in vertical convergence control The control that ad- relation to some edit controllers that depend on the justs the amplitude of the vertical dynamic conver- VITC for accurate editing. These controllers use the gence voltage in a color TV set. VITC to find and return to specific edit points. See vertical definition Vertical resolution. SMPTE/ANSI frame coding. vertical deflection oscillator The oscillator that pro- vertical linearity control A linearity control that per- duces, under control of the vertical sync signals, the mits narrowing or expanding the height of the im- sawtooth voltage waveform that is amplified to feed age on the upper half of the screen of a TV picture the vertical deflection coils on the picture tube of a tube. It gives linearity in the vertical direction so cir- TV set. It is also called vertical oscillator. cular objects appear as true circles. vertical hold A control that regulates and stabilizes vertical lock A method of stabilizing videotape play- the TV image and keeps it from rolling. Many TV back that tries to match the control track pulses of manufacturers have eliminated this external feature, the playback signal to vertical sync pulses coming depending on internal circuitry to halt vertical im- from the sync generator. Since the vertical sync pulses age problems. However, many anti-piracy signals come from the sync generator at precise intervals, work on the principle of a weak vertical hold so they act as a clock. If there are 60 pulses from the that VCRs cannot duplicate tapes with this track. sync generator and only 55 from the control track, But some TV sets without the external control can- then the tape is moving too slowly and the capstan not lock into these prerecorded tapes. Image stabi- servo is signaled to increase the playback speed. But lizers, sold for this purpose, control the vertical signal if there are 60 pulses from the sync generator and both in TV sets and in VCRs, thereby defeating the 63 from the control track, then the tape is moving purpose of most anti-copying signals. too fast and the capstan servo is signaled to slow it vertical interval Vertical blanking interval. down. The big advantage of vertical lock is that a vertical interval editing A method of electronic edit- vertical interval switcher will be able to switch to ing in which the edit takes place on the vertical inter- tape without a breakup. However, time base error val between picture fields so the picture switches from will still be a problem and dissolves, wipes and other one signal to the next without visible distortion. special effects with tape will not be possible. Also vertical interval reference (VIR) A broadcast signal called capstan servo. See Lockup.

295 vertical oscillator vertical oscillator Vertical deflection oscillator. VF 1. Video frequency. 2. Still video floppy disk. The vertical polarization Property of an electromagnetic medium used in still video cameras. See Still video wave in which the plane of polarization of the elec- floppy disk. trical field is vertical. VGA . A graphics display system vertical resolution The number of distinct horizontal for personal computers. Unlike previous graphics lines, alternately black and white, that can be seen standards for PCs—MDA, CGA and EGA—VGA uses in the reproduced image of a TV test pattern. Verti- analog signals rather than digital signals. cal resolution is primarily fixed by the number of VHD videodisc system A now-defunct format that horizontal lines used in scanning. The more hori- used a rotating disc to produce a picture and sound zontal lines, the better the vertical resolution or de- by means of a TV set or monitor. The Video High tail and quality of the picture. With many home video Density player used a stylus similar to that of the components, a vertical resolution of 400 horizontal RCA system and a groove-less disc like that of the lines is considered excellent. Although the US stan- LaserVision (LV) format. The VHD player, which had dard produces 525 lines, very few pieces of equip- a playing capacity of 1 h per side, offered fast and ment come close to that number. Also called vertical slow motion, freeze frame, rapid picture scan and definition. several other features. It played in stereo, similar vertical retrace The return of the electron beam to to other formats. the top of the screen at the end of each field in TV. VHF 30-300 MHz. In TV, refers to the Very High Fre- vertical scan rate For noninterlaced video, this is the quency channels 2-13. VHF uses less energy during same as the frame rate. For , it is transmission than does UHF. See also TV channel usually one-half the field rate. assignments. vertical sweep The downward motion of the scan- VHF/UHF splitter See Signal splitter. ning beam from the top to bottom of a televised VHS Video home system. A format of VCR recording, image. JVC, 1976, that is the dominant format for home vertical sync The signal that tells the electron beam use. The video heads are mounted in a rotating drum to return to the top of the screen for the start of a or cylinder, and the half-inch tape is wrapped around new video field or frame; the portion of the com- the cylinder. This way, the heads can scan the tape posite video signal that tells the receiver the loca- as it moves. When a head scans the tape, it is said tion of the top of the picture. to have made a track. In NTSC two-head helical for- vertical timebase In a CRT, the circuits generating mat, each head records one TV field, or 262.5 hori- the signals that give vertical deflection of the beam. zontal lines, as it scans across the tape. Therefore, In TV this is usually termed the field or frame each head must scan the tape 30 times/s to give a timebase. field rate of 60 fields/s. vertical timing Relative (in discrete lines) of two sets VHS Address Search System See Address search. of vertical sync pulses held in synchronism. An error VHS-C A format of VCR recording that uses a mini- in V-timing results in vertical shifts of the TV picture. cassette (C for compact) inserted into the camcorder. Syn.: V-timing. The minicassette can later be installed into a special very high frequency (VHF) Radio waves in the range VHS housing or adapter to be played on conventional from 30 to 300 MHz; used primarily for TV broad- VHS machines. Besides offering a compact and light- casts. weight camcorder, the format allows editing, with very small aperture terminal (VSAT) Very small earth the addition of an optional editor, onto a regular VHS station that is capable of bidirectional communica- cassette. The format was originally restricted to SP tion by Ku-band. mode for quality recording. Later VHS machines have vestigial sideband A method of encoding digital data a permanent built-in adapter for VHS-C cassettes. onto a carrier for RF transmission. 8-VSB is used for VHS Hi-Fi A method of very high-quality audio re- over-the-air broadcasting of ATSC HDTV in the USA. cording using a VHS video cassette as the recording vestigial sideband transmission A system of modu- medium. VCRs equipped with the VHS Hi-Fi system, lation in which one sideband is transmitted in full, have a regular audio track and two VHS Hi-Fi audio only part of the other sideband being transmitted tracks, allowing audio recordings in the stereo or (usually that corresponding to the lower modulating bilingual modes to be made from an MTS broad- frequencies). The system is used for transmitting the cast, a stereo audio system, stereo videodisc or VCR vision component of a TV signal and has the advan- and played back in the stereo or bilingual mode. In tage that it occupies less bandwidth than if both side- VHS Hi-Fi VCRs, the video signal is recorded on the bands were transmitted in full. It is also called tape surface, and the hi-fi audio signal is recorded asymmetrical-sideband transmission. May also be below the video signal on the video tracks of the used in digital frequency modulation to send data tape. A mono audio signal is recorded automatically over a coaxial cable network. It is faster than the more onto the mono audio track, even if hi-fi is selected commonly used QAM, but also more noise-sensitive. for recording.

296 video camera features

VHS HQ circuitry See HQ circuitry. called SubRoc-3D. Other innovations in arcade VHS Index Search System (VISS) With this system, games include the use of videodiscs for realism and up to 20 addresses can be skipped to directly locate the process of holography to produce 3D images. the beginning of the desired program in FF or REW video art A creative use of video technology includ- mode. An index signal is automatically recorded ev- ing lasers, videotape, computers, TV furniture and ery time when the REC button is pressed. See VISS. sound; expressed, often abstractly, in stills, moving VHS speed mode A speed at which videotape plays or images, sculpture and sometimes architectural records in a VHS-type VCR. The three basic speeds forms. Artists first experimented with video as a are SP (Standard Play), LP (Long Play) and EP or SLP means of artistic expression in the late 1960s. To (Extended or Super Long Play). SP plays for 2 h on a some video artists the term is considered deroga- conventional T-120 cassette and is the mode used tory; they prefer to be known as “artists who use for best resolution and prerecorded tapes. LP, which video.” has a 4-hour range, has been phased out as a record- video artist Any artist who works full- or part-time ing mode by some VHS manufacturers who consider with any number of components related to video the speed superfluous. These companies often pro- and/or its technology. vide two additional video heads designed especially video/audio amplifier Audio/video amplifier. for the EP mode. With a thinner-type tape, the VHS video cable Coaxial cable for signal transmission in maximum play/record time has been extended to 8 h. video systems. Also used as TV tuner-to-IF amp in- VHS/VHS-C VCR A VCR that can accommodate both terface—see RG-58A/U. Basic types include: (1) 75- standard VHS cassettes and VHS-C compact cas- ohm unbalanced indoor cable, (2) outdoor cable that settes without the required additional adapter. Nor- has a single conductor centered in a shield, (3) 124- mally, the smaller VHS-C cassettes, to play in ohm balanced indoor cable, and (4) outdoor cable conventional VHS machines, must first be placed into that has two parallel or twisted insulated conduc- a cassette adapter that is then inserted into the VCR. tors centered in a shield. The decks have a dual-loading system consisting of video cable tester A device designed to check cables a built-in VHS-C adapter in the main transport com- for broken conductors, continuity and shorts and partment and special transport devices to handle the whether the problem stems from the shield or the thinner tape. center conductor. The tester usually accepts BNC vid Informal. A short video film. and UHF cables as well as a combination, such as V-identification Using the special signals in each field BNC-to-UHF. There are separate audio cable testers blanking period to recognize SECAM signals. V-iden- available. tification is more reliable than the H-identification video camera A video recording system component because the identification signals are longer and have that collects images (through a lens onto an image a greater frequency deviation (3.9 MHz for B-Y and pickup tube or similar device) and sound (through a 4.756 MHz for R-Y). When it is required to transmit microphone) and converts them into electrical sig- other information during the field blanking period, nals that are then changed to magnetic signals by a several transmitters (e.g., in France) stop transmit- VCR. There are several types of video cameras: pro- ting the V-identification signals. fessional, industrial, surveillance (in banks, stores and video Literally “I see” in Latin. Refers to picture infor- other places requiring high security) and home mod- mation or a medium which uses TV to transmit and els. Early home video cameras required a two-piece receive video. Video has emerged to a position in system made up chiefly of the lens, image pickup which it is no longer synonymous with TV. For in- tube and viewfinder in one unit and a portable tape stance, video does not have to be sent from long deck in the second unit. The one-piece camcorder, distance as TV does. Participating in a video game which houses both components in one compact unit, or playing back a videotape or videodisc is not watch- has virtually replaced the two-piece home models. ing TV. TV is, or has become, only one form of video, Digital video cameras have also come to prominence. albeit a major one. video camera features Any functions, controls and/ video accessory See Accessory. or switches excluding the basic components, such video album maker A VCR function that lets the user as the lens, of a video camera. The number and so- pick out exactly the sections desired and dub them phistication of features vary, of course, with each to another VCR in any order. camera. Some offer the most popular features, such video amplifier A wideband amplifier capable of am- as audio/video dub, which replaces part of the old plifying video frequencies in TV. audio and video; backlight control, which slightly video animation See Pixilation. boosts exposure; clock/calendar to superimpose time video arcade game A coin-operated electronic game and/or date; self timer, which allows the camera user console containing its own controls and screen. It is to step into a scene; and tape time remaining indi- often adapted to home video game use. Sega En- cator, which shows how much shooting time is left terprises introduced the first 3D video arcade game on the cassette. Other camera models provide addi-

297 video camera sensitivity

tional features, including, among others, auto im- settes. Some machines provide built-in adapters that age stabilizer, which moves the lens assembly to help accept the compact cassettes directly. steady the video capture; character generator for videocassette player (VCP) A videocassette deck that making titles; color viewfinder; digital enhancer to has the appropriate functions to play back prere- boost contrast for better images in low light; dual corded tapes but lacks those features needed to camera recording, which mixes pictures from two record. Obviously designed as a second unit or a different cameras; flying erase head, which helps to primary machine for those who just want to view prevent video noise and glitches between scenes; tapes, these players often have additional features, microphone mixing; monitor speaker, which replaced such as automatic rewind, on-screen displays (for headphones; and trigger alarm, which warns user the time counter), double speed play and high-speed at the beginning and end of recording. search. Dubbing, of course, can only be done from video camera sensitivity The ability of a camera to a VCP to a VCR and not vice versa. reproduce a usable image with a minimal amount videocassette recorder (VCR) A consumer electron- of light. Sensitivity is usually measured in footcandles ics video recorder that can capture live TV programs (fc) or lux. For instance, the sensitivity of a certain on tape for later replay. It is also capable of playing camera may be rated at 50 lux (5 fc). Many video back prerecorded cassettes of personal events (from cameras feature a sensitivity switch, which increases camcorders), commercial movies, or other televised sensitivity. To decrease sensitivity, a neutral density entertainment or educational material through a filter is attached to the front of the lens. All video standard TV set. cameras have a sensitivity range, the average range videocassette rewinder Rewinder. being approximately 10-10,000 fc. Video CD Compact discs that hold up to about an video capture Converting a video signal into a for- hour of digital audio and video information. The mat that can be saved onto a hard disk or optical audio and video are compressed and stored using storage device and manipulated with graphics soft- MPEG-1. Video resolution is 352 x 240 (NTSC). DVD ware. This is accomplished with a device internal to provides much higher resolution, and Video CD a computer called a “frame grabber” or video cap- never caught on in North America. The next gen- ture board. Images thus captured are digitized, and eration, defined for the Chinese market, is Super can be dropped into a document or database record Video CD. and may be transmitted locally on a LAN or long video circuit A broadband circuit that carries intelli- distance over a WAN. See Video capture board. gence that could become visible. video capture board To capture a single frame of video codec The device that converts an analog video motion video successfully, a board inside a PC must signal into digital code. capture the two fields comprising a single video video coder overload Can occur with rapid scene frame. See also Frame grabber. cuts, only a few frames apart, which stress digital video carrier 1. A specific frequency that is modu- compression systems by presenting them with a lated with video data before being mixed with the video signal that contains little or no temporal re- audio data and transmitted. 2. The TV signal that dundancy (frame-to-frame correlation). carries the picture, sync and blanking signals within video combination IC A device to convert the color its modulation sidebands. difference signals and the luminance signal into the video card/adapter An expansion board used in a RGB signals. Usually this integrated circuit (IC) in- computer to produce the video signal required by corporates the saturation, contrast, and brightness the monitor to display text or graphics. control circuits and allows for the insertion of exter- videocassette A rectangular, flat plastic shell or hous- nal RGB signals. Used in older TV sets. ing containing two built-in tape reels (supply and video compositing A system, similar to chroma key- takeup) and a single, 1/2-inch-wide cobalt-alloy mag- ing, in which one or more images is combined with netic tape that is exchanged between them during another image to form a final and different picture. recording, rewind, and playback. The cassette is in- For instance, a shot of the Grand Canyon can be serted in the VCR, and the VCR pulls out the tape used as background. Then a family is recorded and positions it over rollers and around a rotating against a blue background. When the two shots are head drum at an angle for helical recording. The integrated, it appears as though the family were at cassette for the most popular VHS format measures the site. approximately 7-3/8 x 4 x 1 in and records at a rate video compression Refers to methods for reducing of 580 m/s. the size of video files digitally so they can be stored videocassette adapter An accessory that allows VHS- and transmitted using less memory and bandwidth. C mini-cassettes to be played in conventional VHS Video compression methods are advancing at a rapid machines. Normally, the compact videocassette is rate, with new, powerful codecs (compression/de- placed into the adapter, which is then inserted into compression techniques) being developed. Codecs the VCR housing that accepts conventional-size cas- work in two ways: using temporal compression,

298 video dial tone

which compares frames and deletes redundant in- VideoCrypt Encryption system in European and US formation; and using spatial compression, which also satellite TV. The VideoCrypt scrambling system used looks for redundancy but defines those areas using by the DSS system in the US differs from the Euro- coordinates. See MPEG. pean implementation: European VideoCrypt is a video conference Also videoconference. To commu- purely analog system that scrambles only the video. nicate with others using video and audio software DSS is a completely digital system that encrypts the and hardware. Audio can be provided through spe- digitally encoded video and audio. However, there cialized videoconferencing equipment, through the are many similarities between DSS and VideoCrypt, telephone, or through the computer. Video- including the use of smart cards. conferencing has traditionally been done with dedi- video data Information transmitted electronically and cated video equipment. But, increasingly PCs displayed on a TV screen. There are three systems of communicating over switched digital lines are be- providing video data. Cable TV offers a one-way pas- ing used for videoconferencing. sive system in limited areas to paying subscribers only. video conferencing Also videoconferencing. Video Computer networks, available to subscribers nation- and audio communication between two or more ally, offer the most sophisticated video data services. people via videocodec at either end and linked by This data can be stored or processed by a machine digital circuits. Formerly needing at least T-1 speeds into hard (printed) copy. This system also permits (1.54 megabits/s), systems are now available offer- data input. The third method consists of signals car- ing acceptable quality for general use at 128 kbits/s ried by telephone lines or broadcasts available pres- and reasonable 7-kHz audio. Factors influencing the ently only in a few areas. The above three sources growth of videoconferencing are improved compres- of video data vary in programming, from simple news sion technology, reduced cost through VLSI chip printout, financial information and transportation technology, lower-cost switched digital networks— schedules to ordering merchandise electronically and particularly T-1, fractional T-1, and ISDN—and the reserving a seat on a commercial airline. emergence of standards. See Teleconference, video data digital processing Digital processing of Videoconferencing standards. video signals for pictures transmitted over a TV link, videoconferencing standards CCITT H.261 was the to improve picture quality by reducing the effects standards watershed. Announced in 1990, it relates of noise and distortion. The computer compares to the decoding process used when decompressing each scanned line with adjacent lines and elimi- videoconferencing pictures, providing a uniform pro- nates extreme changes caused by electromagnetic cess for codecs to read the incoming signals. Origi- interference. nally defined by Compression Labs Inc. Other video detector The detector that demodulates video important standards are H.221: communications intermediate frequency (IF) signals in a TV set. framing; H.230: control and indication signals and video dial tone In “telco-speak,” a means by which H.242d: call set-up and disconnect. Since replaced the phone company, in competition with the cable by H.263. TV business, can provide video to houses and of- video controller A professional/industrial device that fices. It does not affect the content of that video provides frame-accurate control of most videotape signal in any way. This is Nortel’s explanation of video and videodisc units. Similar to an edit controller or dial tone: “Recent advances in communications and editing console, the video controller offers several computer technology, such as fiber optic cables, digi- additional and unique features. A composite video tal switching and hyperspeed computing, make it switching function, for example, allows frame-cap- possible to transmit extraordinary volumes of inter- turing or frame recording to and from the same unit active electronic information in digital form through for rotoscoping purposes. In the field, the video con- telephone networks. Consumers may soon be able troller can pilot two machines. to access an intriguing array of multimedia electronic video converter A professional/industrial instrument entertainment and information services from the designed to convert video graphics to various broad- comfort of their homes via a gateway service called cast standards signal specifications, such as NTSC video dial tone, which is part of what multimedia is and PAL. Video converters may operate in genlock all about. Multimedia means interactive full-motion mode or independently with composite, Betacam, video, sound, text and graphics all available on your S-VHS and MII formats. TV, computer terminal or advanced intelligent video copy processor A unit designed to produce telecomputer. There may soon be a proliferation of full-color hard copies (print-outs) from video images. so-called “intelligent phones” that will transform the These professional/industrial machines incorporate touch-tone telephone into a versatile home com- a sublimation-type printing process, can store im- puter. By means of simple push-button commands, ages and data and produce 640 pixels x 480 lines customers will be able to: NTSC resolution. See Video printer. • Select entertainment on demand (movies, music, video crosstalk See Crosstalk. video).

299 video digitizer

• Order groceries or other services or products. video effect titler A stand-alone unit designed to su- • Record customized news and sports programming. perimpose computer-generated color images over • Enroll and participate in education programs from another video image coming from an external source the convenience of their living rooms. such as a VCR, video camera or VDP. The video ef- • Find up-to-minute medical, legal and encyclopedic fect titler permits the user to superimpose color titles information. over a camera image as well as add titles to prere- • Pay bills and manage finances. corded videotape while editing. Most industrial • Make airline, rental car and hotel reservations.” models include genlock (for locking in to other video video digitizer A professional/industrial instrument de- sources without time base correction), a keyboard, signed to display images of 30 frames/s in real time expansion port and computer interfacing. The key- on a computer monitor. Video digitizers can usually board may have a color key to change the color of accept multiple inputs, such as RGB, Super-VHS and characters, backgrounds of objects; an object key composite video signals from NTSC or PAL, with the to display, change or delete an object; and a page capability of displaying them at the same time. key to shift to any page in the unit’s memory. The videodisc A record that plays sound and pictures video effect titler usually includes several fonts, the through a conventional TV set. Two major types of capability of storing many pages of titles in memory videodiscs are the LaserVision and the Capacitance and special function keys such as color key, object Electronic Disc (CED). The grooveless LV disc is de- key, page key and clear key. Although a video effect coded by means of a laser; no arm or head makes titler is similar in many respects to the more costly physical contact with the disc. The now-defunct CED character generator, the latter has more sophisticated system used a grooved disc that required a stylus to features, such as direct and sequential page access, read the information on the surface. The videodisc, edit capability with full cursor control, screen blank popular in the early 1980s, fell into disfavor for most function and the ability to generate its own sync of the remainder of the decade, and made a come- without the presence of video. In addition, an in- back in the late 1980s. Still favored by some dustrial-model character generator may also feature videophiles because of its higher-quality picture. preview output, video fade control, key output, loop videodisc player (VDP) An electronic unit, resembling through and BNC connectors. a record player, that plays back pictures and sound video encryption A method of encoding video mate- from a prerecorded disc to a TV set. Although it can- rial for security reasons. There are several systems em- not record, the VDP features some advantages over ployed for video encryption. Some are designed to videotape, such as direct random access, longer-last- prevent access to unauthorized persons; others have ing software and better resolution. the capabilities to destroy video and audio data; still videodisc recorder A professional/industrial machine others are accessible through the use of certain de- that can produce 12" videodiscs. These units record coder devices. Both transmitted signals and video- on both sides, provide standard recordings of 54,000 tapes can be encrypted, depending on the system frames/s and offer remote control. used. Some systems, such as Macrovision, which con- videodisc speed The LaserVision has two speeds: CLV figures the vertical blanking lines, are chiefly used with (Constant Linear Velocity) discs play for 60 minutes consumer videocassettes. Other, more sophisticated per side while CAV (Constant Angular Velocity) discs systems, are used exclusively in professional situations. play for only 30 minutes. Both CLV and CAV discs Current professional video encryption systems, which are compatible with all LV machines, but the 60- because of the high cost can usually be rented, use minutes-per-side disc cannot be used with freeze- either analog or digital encryptors. frame and other special effects. video enhancer/stereo audio mixer An accessory video distribution amplifier (VDA) An amp for unit that combines the capabilities of an image en- strengthening the video signal so that it can be sup- hancer with selected audio features. The stereo au- plied to a number of video monitors at the same dio portion of the unit allows the user to add time. narration and/or background music to a home video video dubbing A special feature found on some VCRs tape. These accessories usually offer several stereo which permits the insertion of a scene or title onto audio inputs and separate volume control knobs an existing scene. Video dubbing with these VCRs along with video signal control. provides superimposed effects without picture video equalizer See Equalizer. breakup at the beginning or end of the newly added video feedback A simple special video effect created material. With conventional machines, recording by aiming a video camera at a TV set used as a moni- over previous information automatically erases what- tor during taping. By zooming in on the image, the ever audio and video signals are on the tape. Video camera records an infinite number of images of it- dubbing also applies to the technique of replacing a self videotaping itself. By changing positions, one portion of recorded video information while keep- can create an endless variety of images. ing the original sound track. Video for Windows Microsoft. System-level

300 video head drum

Windows software architecture integrating video, the game may be connected to the VHF input of sound, and animation, similar to Apple’s QuickTime. the recording machine. The VCR is set at an open video frequency (VF) A composite video signal channel, either 3 or 4, and the Record button is unmodulated by a radio carrier frequency. One of pressed. the frequencies that exist in the output of a TV cam- video game software The games, or game cartridges, era when an image is scanned. It can be any value disks and videocassettes, that fit the various video from almost 0 to well over 4 MHz. game consoles or systems. video-frequency amplifier An amplifier capable of video game system Also known as game consoles. handling the entire range of frequencies that com- A popular form of entertainment. The most current prise a periodic visual presentation in TV. video game systems include Microsoft’s , Sony video frequency converter An electronic accessory PlayStation, Nintendo 64, and Sega . A designed to convert the color frequency of a com- video game system is a highly specialized computer, posite video signal to a different frequency. For ex- easily connected to a TV and/or stereo system. Most ample, in some foreign systems in which a 4.43-MHz systems allow multiple players. Individual game car- frequency is used, the video encryption can change tridges can be purchased or rented. this to be compatible with the NTSC domestic fre- videographer A term sometimes applied to one who quency of 3.58 MHz. A professional/industrial com- uses a video camera or camcorder. From video ponent, the converter permits the connection of photographer. multi-standard video recorders to NTSC-standard video graphics See Graphics. monitors and recorders for both playback and video graphics generator An electronic accessory recording. designed for commercial displays, closed circuit TV video frequency response See Frequency response. applications and, through the use of color graphics video gain See Gain. and characters, the creation of pictures on the TV video game An electronic game that can be connected screen. Some graphics generators permit storing up to or built into a TV set, to use the TV screen as a to 15 pictures in its memory, provided the power is playing field or display showing player and ball move- not turned off, while other models allow superim- ments, scores, or other actions called for by the posing images on present recordings. Generally, the game, race, or other type of activity which is con- graphics produced by these generators lack the de- trolled remotely by one or more players. Micropro- tail of computer graphics. The units resemble the cessor-based models can also provide sound effects detachable keyboards of computer terminals. Some and interchangeable program cards for changing the low-cost video graphics generators do not reproduce rules of a game or changing the entire game. the same quality image on videotape as they do on video game cartridge Software for a video game sys- the TV screen. tem. In general, a cartridge produced for one par- video head A magnetic unit consisting of a small metal ticular system will not fit another game system. housing, a coil through which a signal is passed, video-game epilepsy (VGE) Youngsters who play and a narrow gap from which a magnetic force video games may suffer generalized convulsions, places video information on the videotape as it splitting headaches or other unpleasant symptoms passes by. The basic VCR has two heads, each of either while playing video games or watching other which places down a diagonal field on the tape. people play them. The affliction, first diagnosed in Some VHS machines have four heads, two for the 1981, is known as VGE. Studying children who had fastest speed and two with a special gap for the suffered attacks of VGE, Japanese doctors identi- slowest speed. Still other VHS recorders have four fied repetitive geometric patterns and flashing white heads, but with different functions. One pair is for lights as among the visual stimuli that set off sei- recording and playing back while the other two zures. While normal TV broadcasts or flickering TVs heads are for special effects such as slow motion have also provoked seizures in certain viewers, the and freeze frame. doctors speculated that video games might provoke video head alignment See Alignment. seizures more easily “because video-games show video head cleaner An accessory, such as individual more geometric figures and usually are played with swabs, complete kits and special cleaning cassettes, the child sitting close to the screen.” that dissolves or removes dirt, oxide particles, dust video game hardware The system upon which video and grease from heads and other critical parts of a games are inserted and played. Hardware may be VCR. dedicated game systems (such as those manufac- video head clogging A condition caused by an accu- tured by Atari, Nintendo and Sega), PCs equipped mulation of oxide particles peeling from the tape, with CD-ROM players, or combination computer/ dirt, dust and/or other foreign matter on the heads game arrangements. of a VCR. Clogging results in snow appearing in the video game recording The output of a video game TV image and other signs of picture interference. placed on tape by way of a VCR. The RF output of video head drum A cylindrical component that holds

301 video head gap

the video heads (it might also house the hi-fi audio part is a digital video interface (based on BT.656) heads in a VHS hi-fi VCR). Located inside the VCR, designed to simplify interfacing video ICs together. the drum rotates at 1800 rpm and is set at an angle. The other part is a host processor interface that is The diameter of the drum varies according to the similar to a two-bit PCI-type interface. Used to in- format of the machine. terface two or more digital video clips together. video head gap See Gap. video inversion A type of encoding or scrambling in video head separation The position of the video which the transmitted downlink video signals are heads as they appear on the head drum of a VCR. A inverted. The TV set may or may not sync on it (de- typical two-head machine has each of the heads pending whether the sync pulses are inverted also). mounted 180 degrees apart around the drum. Most Usually nothing is done to the sound, although it VCRs with four heads have each head equally lo- may be modulated onto an ultrasonic subcarrier, and cated 90 degrees apart. Some machines with four the sound carrier may have what is called barker heads, on the other hand, place two heads adja- audio on it. This is usually a taped message telling cent to each other while their two counterparts are you how to subscribe to the service, or what you on the opposite side of the head drum. This radical are missing. arrangement minimizes noise bars, thereby improv- video inverter A device to invert a camcorder video ing such special effects as freeze frame. output to view photographic negatives. video head-switching noise See Head-switching video jockey A person who presents a continuous noise. program of short video films and similar material on Video High Density See VHD videodisc system. TV. Video Home System See VHS. video keyer A professional/industrial post-production video hum Video disturbances caused by ground volt- unit that can combine several key sources over a age differences or electromagnetic pickup. single background picture. Other features include video IF See VIF. individual clip adjustment for each input, advanced video image compositing A professional/industrial edging effects and full linear keying through a wide- system that employs screen correction circuitry to range gain control. produce improved multi-layered compositing in post- video level Refers to the degree of brightness or con- production work and composites with imperfect blue trast in the screen picture. If the picture is too bright, screens. In addition, the system allows for realistic the detail in white portions of the image is lost; if composites with natural shadows in a multi-layered the picture is too dark, detail in the shadows or dark image without the usual darkening in the corners. portions of the image suffers. video input A jack or receptacle on a VCR or other video line in Video input. component that accepts video signals. It is often used videolog A videocassette featuring advertisements for in place of an RF input to give a direct signal, thus a items (e.g., clothes) that can be bought via mail higher definition picture. If a video signal is modu- order. lated to RF (as when using a TV receiver), then de- video mail Electronic mail that includes moving or modulated to its original form, some loss of still images. definition occurs. The video input is also used for videomicroscopy The use of TV cameras to brighten recording from another VCR’s video output. magnified images that are otherwise too dark to be video insert A video camera feature that permits re- seen with the naked eye. cording a new image over the previous one without video mixer A mixer that combines the output sig- affecting the audio portion of the tape. On some nals of two or more TV cameras. cameras the insert is performed in the following way: video mixing Merging two independent video sources the camera is placed in VCR mode and the tape ad- (they must be genlocked). See Alpha Mix. vanced to the part where the insert is to start. Next, video modulation Converting a baseband video sig- the Pause control is pressed to stop the tape. When nal to an RF signal. the camera trigger is pressed, the new video infor- Video Module Interface (VMI) A digital video inter- mation is recorded while retaining the original au- face initiated by SGS-Thomson designed to simplify dio material. The video insert feature is especially interfacing video ICs together. It is being replaced useful in adding titles to recorded videotape. by VIP. video inserter A stand-alone accessory designed to video moire See Moire. superimpose messages and graphics onto video im- video monitoring equipment Monitoring equipment ages. Chiefly a professional/industrial device, the for analog TV includes picture monitors, which also video inserter conforms to several standards, includ- come in various price/performance levels. Broadcast- ing NTSC, PAL and SECAM. Some models have the level video monitors cost several thousand dollars capability to display information from integral and come as close as possible to being transparent, memory or from external sources. which means that the picture you see depends on Video Interface Port (VIP) VIP has two parts. One the signal and not the monitor. Broadcast monitors

302 video server

also include various display modes that allow differ- video output A jack or receptacle on a DVD, VCR or ent aspects of the signal (in addition to the picture other piece of equipment to transmit the video sig- component) to be observed. One common feature nal to another unit. For example, when copying a is the pulse-cross display, which shows the synchro- videotape onto another machine, a cable is con- nizing signal part of a composite video signal. Broad- nected from the video output of the player to the cast monitors are designed to be capable of being video input of the recording VCR. Video jacks usu- matched, so that a group of monitors shows the ally accept RCA phono plugs. same signal the same way. Matching is important videophone Video telephone. when several monitors are to be used to set up sig- Videophone 2500 In 1992 AT&T introduced a prod- nals that may eventually be combined into the same uct called Videophone 2500, which transmitted program. In such a case, it is important that the color moving (albeit slowly moving) color pictures over reproduction of all signals match as closely as pos- normal analog phone lines. Videophone 2500 relies sible. Broadcast monitors always have inputs for on video compression from Compression Labs, Inc. composite signals. Some monitors also have RGB of San Jose, California. inputs, but this is unusual, because RGB signals sel- video piracy The illegal duplication and sale of copy- dom exist today in broadcast studios or righted material or receiving pay TV programs for postproduction facilities. Professional-level monitor- free via an illegal decoding device. See Anti-piracy ing equipment is designed to a slightly lower price/ signal. performance point—pictures are still very good but video player A player that converts a videodisc, vid- some features may be sacrificed in the interest of eotape, or other type of recorded TV program into price. Consumer-level monitoring equipment is signals suitable for driving a home TV set. mostly done with the ubiquitous TV receiver. All TV video printer A device to convert video images to still sets have an antenna input for receiving the com- prints. Usually uses a thermal ink transfer method. posite signal in RF form as it is broadcast on a TV Video printers equipped with field-only memory will channel. Current TV sets also have video inputs for capture one of the fields (half the image). a baseband composite signal, which may come from video processing Refers to the electronic alteration a consumer camera, VCR, or . (A of a video signal. This may take the form of adjust- baseband composite signal is a video signal that has ing the color or brightness of the signal during not been modulated up to a TV channel.) A YPbPr copying. or RGB input is also now included on most TV sets. video processor Processing amplifier. video music A technique employed to display music Video Program System (VPS) A device that assures graphically on a TV screen. The intensity of music that the TV shows programmed for timer recording being played on an average stereo system is trans- will be recorded exactly from beginning to end, even lated into visible patterns, shapes and colors. The if the actual broadcasting time is different from the TV image constantly changes as it responds to the scheduled time. The VPS function is operative when music, allowing the viewer to “visualize” the sound. the VCR is equipped with the VPS decoder. video noise Interference or an unwanted signal in the video recorder A recorder capable of storing the video TV picture, usually in the form of dark or light hori- signals for a TV program and feeding them back zontal lines, bars, etc. Video noise, which causes later to a TV transmitter or directly to a receiver. Ex- “snow” in black and white pictures and dark amples include electron-beam video, holographic blotches in color picture, is measured in dB. Video video, video disc, and VTRs. noise affects color clarity and image sharpness. The video recording Recording of information that has a higher the number of the signal/noise ratio, the bet- bandwidth in excess of about 500 kHz, such as TV ter the image. signals. video on demand (VOD) Punch some buttons. Order video repeater Amplifier inserted at a point in a video up “Gone With the Wind” to start playing at your line to compensate for the attenuation in the line. house at 9:38 P.M. on Channel 37. You have VOD. video replay Also known as video tape replay. 1. A In other words, when video can be requested at any procedure in which the audio and video signals of a time and is available at the discretion of the end- TV program are recorded on tape and then the tape user, it is VOD. VOD requires a very large media stor- is run through equipment later to rebroadcast the age system (terabytes). live scene. 2. A similar procedure in which the scene video-on-sound (VOS) A VCR editing feature that is rebroadcast almost immediately after it occurs. permits the user to record a video signal over an Also known as instant replay. earlier recorded hi-fi audio track. This provides more video scanner A computerized CCD unit designed to versatility in mixing audio and video. Hitherto, pic- copy flat artwork, text, maps, photographs and other ture and sound tracks were recorded simultaneously pictures. These graphic images can be altered with since they are both written in the same area on the new colors and superimposed on video recordings. videotape. video server A device that can store thousands of

303 video signal

movies, ready for watching by subscribers at their videotape A heavy-duty magnetic tape designed pri- individual whim. A video server could be a jukebox- marily for recording and playback of the video sig- like device that stacks several hundred movies, or it nals of TV programs. The tape consists of several could be a powerful, large computer with several elements: a backing that resists stretching and de- large hard disks and/or optical disk drives. This de- composition; a coating of microscopic particles that vice is to be used in conjunction with the local tele- can be easily magnetized, hold their magnetic charge phone companies’ service called video dial and resist shedding; and a binder that causes the par- tone—providing movies over normal phone lines to ticles to adhere to the base. Early videotape stemmed subscribers—or it can be used with the CATV from the technology of audio tape, with a handful of industry’s proposed video on demand service. manufacturers supplying the many tape companies. video signal (US: composite signal) In TV, the signal But the quality improved rapidly, especially with the obtained by combining the picture signal with the second generation, HG (High Grade) tapes. Present synchronizing signal. Some lines may carry closed tapes often consist of several layers, such as the mag- caption and teletext data. A commercial quality full- netic particles and binder, an adhesive, a film base, color, full-motion TV signal requires 6 MHz. carbon for added opacity, another film base followed video signal-to-noise ratio The amount of distor- by another adhesive, and a backcoating for improved tion or video noise in a picture, expressed in dB. The reliability. higher the dB ratio, the less noise or distortion in videotape cleaner A device designed to clean and the picture. Most home video components tend to polish a videotape in several minutes. Some video- fall into the 35 to 45 dB range. tape cleaners provide additional features such as in- video single (VS) A prerecorded videocassette intro- spection and rewinding. Other models have a tape duced by Sony in Japan in 1982 and in the US in information display that gives tape length and the 1983. VSs, contain two to four songs each and have number and position of physical defects. an average viewing time of about 15 or 20 minutes. videotape coating See Coating. They are similar to 45 rpm records in concept. videotape evaluator A table-top device which uses video stabilizer See Image stabilizer. LED readouts to count tape defects. A videocassette video still camera An electronic camera designed to is inserted into the evaluator which fast-forwards use a small electronic memory card instead of pho- the tape at 25 times the normal speed. The machine tographic film. After recording, the disc is inserted also cleans the tape during the defect-measuring into a viewer that displays still pictures on a TV set. process. Prints can be made on an accessory printer. This tech- videotape format Refers to the size, length and nology is moving more and more into the digital method of enclosure of videotape as well as to the realm. speed at which it moves past video heads. There are video streaming Refers to techniques for delivering formats for both consumer and professional/indus- video and audio files over the Internet, cable, or DSL trial use. Generally, consumer formats come in cas- from a server to a client, with the client playing the settes or cartridges and include VHS, Super-VHS, incoming multimedia stream in real time as the data Super-VHS-C, 8mm, Hi8; popular professional tape is received. New compression algorithms are being formats include D-1, D-2, 1" Type B, 1" Type C, 3/ developed specifically for , including 4", 1/4" SP, Betacam, Betacam SP, MII, industrial MPEG-4, wavelet and fractal codecs. Beta, HDTV. Three major techniques developed for video switcher A piece of equipment that allows a recording sound and picture on magnetic tape: lon- choice from many incoming video sources and makes gitudinal (LVR), quadruplex (quad), and helical scan transitions or other special effects between those videotape recording. LVR principles are seldom used sources. It is the keystone around which the rest of in video recording today, and the quad method is the TV studio is built. See Production switcher, SEG, obsolete. The helical-scan technology has become Switcher. the predominant method. video synthesizer An electronic console designed to videotape grade A method a manufacturer uses to transform video signals from various ordinary sources mark the quality of videotape. Although some video into a variety of patterns. Developed by video artists users believe there are no differences among the Nam June Paik and Shuya Abe, the synthesizer, of many grades of tape, manufacturers assert there are which there are several versions, is intended to turn distinctions in their tape formulas and processes and TV viewing from its passive absorption of images that higher-grade tapes provide better audio and into an active medium. video results. Tests conducted by some leading video Video System 2000 Teleconferencing system offer- magazines tend to show some differences, but the ing audio and videoconferencing via Europe’s ISDN. technicians are quick to point out these differences It comes with a video camera (to mount on top of generally are slight. Better-grade tapes usually are the monitor), an ISDN plug-in board, a headphone accompanied by such relative descriptions as “pro,” set and software. “super,” “high” or “extra” on their boxes. Some

304 videotex editing terminal

tests often list a high-quality standard tape as supe- rotation, linearity and centering of each channel by rior or equal to some high-grade tapes. using a special grid pattern. A gray-scale chart, pro- videotape lengths Minutes. gressing in steps from black to white, measures dif- Cassette VHS-SP VHS-LP VHS-EP ferences in phase and gain. A flesh tone reference chart checks for skin and hair color, avoiding the T-30 30 60 90 use of a live subject during camera setups. A multi- T-60 60 120 180 burst chart is used in testing and adjusting camera T-90 90 180 270 system response. There are also multi-chart systems T-120 120 240 360 for professional use. One two-chart system, e.g., con- T-160 160 320 480 tains a registration and color balance chart designed videotape quality The ability of videotape to with- to check alignment, registration and color balance. stand certain pressures, resist others and retain im- videotex A system of storing a large tree-structured portant features. Videotape performance can be database, consisting of pages of text and graphics measured in three basic areas: video, audio and data, with user-friendly commands, and accessing physical properties. Video characteristics include pages from low-cost terminals, often videotex adap- video signal-to-noise ratio, chroma signal-to-noise. tors, using a standard domestic TV set for the dis- video frequency response, dropouts, FM loss (affect- play screen. Data is communicated over standard ing the number of replays). Audio properties encom- telephone lines. A number of countries have estab- pass audio signal-to-noise ratio, audio frequency lished public videotex services, such as Ceefax in the response, etc. The physical aspects of tape that are UK, and private videotex systems have become of often judged involve length, width, strength, stretch- major importance to a wide range of commercial ing, evenness of tape edges. and industrial organizations. Videotex is the inter- videotape recorder See VTR. nationally accepted term for the system, originally videotape replay A VTR that uses a relatively short called viewdata in the UK. While popular in Europe, endless loop of magnetic tape to permit the repeti- videotex never became popular in the U.S., although tion of a televised sports scene within seconds after it could be said that early computer information ser- the original action. See also Video replay. vices such as Prodigy and CompuServe were a type Videotel Videotex system, Italy. of videotex service. video teleconferencing Also called video- videotex adaptor A device incorporating a modem conferencing. The real-time, and usually two-way, and videotex decoder which when attached to a transmission of digitized video images between two standard domestic TV set and to the public telephone or more locations. Transmitted images may be freeze- network allows a user to access a videotex system. frame (where the TV screen is repainted every few videotex charges Charges for the videotex system; they seconds to every 20 s) or full-motion. Bandwidth include the telephone line and a cost per page based requirements for two-way videoconferencing range on the value of the information. Charges are higher from 6 MHz for analog, full-motion, full-color, com- for specialized data; there is no charge for menus, mercial grade TV to two 56-Kbps lines for digitally classified advertisements, and some of the infopages. encoded reasonably full-motion, full-color, to 384 videotex decoder A circuit that permits the TV set to Kbps for even better video transmission, to 1544 be connected to the telephone network for commu- Mbit/s for very good quality, full-color, full-motion nication with a database. It can be built into existing TV. See Teleconference. TV sets or into adapters for attachment to existing video telephone Also called videophone. A combined units. A decoder is composed of five devices: telephone and video receiver that allows each party 1. A line isolator. Its function is to protect the tele- to see the other party while talking. phone lines from high voltages present in the TV. video test chart Refers to a method of testing or mea- 2. A modem to convert the analog telephone sig- suring one aspect, function or feature of a video nals into digital and the digital into analog. component. There are various test charts. For ex- 3. A memory to store data for display. ample, a color bar chart can be used for a video 4. A display generator able to transform characters camera set-up or for recording a color reference on stored in the memory to dot patterns. tape. Containing the primary and secondary colors, 5. An input processor, whose function is to control it checks the color accuracy of lenses, color separa- and synchronize component operations, process tion and other related areas. A resolution chart mea- incoming signals, and store the signals in memory. sures the sharpness of camera images; in addition, videotex default The default format: 24 rows of 40 it checks other aspects of a video camera, including columns with automatic wraparound on rows and camera streaking, ringing and aspect ratio. A linear- columns. ity chart measures a camera’s scanning linearity and videotex editing terminal A terminal that allows the assists in its adjustment. A registration chart is de- user to create videotex pages and update a video- signed to test cameras for scan height, skew, width, tex database.

305 videotex features videotex features The ability to restrict access via se- active program selection and simultaneous control curity keys to parts of the database and only from of several players. authorized terminals; automatic billing of the video wallpaper A TV background or visual effects charges to the user; credits to the information pro- that are dull. viders concerned; the possibility of making purchases video waveform 1. The display of a video signal on via the system; and message handling facility. an oscilloscope. The signal is dissected into its vari- videotex page A single frame (screenful) of informa- ous components, which can be examined for integ- tion, containing 24 lines each of 40 characters of rity. 2. The portion of the TV signal waveform that the standard videotex character set. Normally only corresponds to visual information. Sync pulses are the middle 20 lines are free for information. The first not included. and last line are reserved for the videotex system, Videoway A Canadian interactive CATV system. Us- and it is well to leave a buffer line on each side. ing an interactive device located on the top of the videotex standard The standard adopted within a TV set, a viewer at home can select optional visual country or by a system supplier for the transmission images. of data within a videotex system. There are three video windowing display controller A professional/ main types of videotex standard: alphamosaic, industrial editing controller that integrates real-time alphageometric and alphaphotographic. video with computer-generated text and graphics Videotext 1. Videotex system, Spain and Switzerland. on a monitor. NTSC and PAL real-time video appears 2. Sometimes used to embrace both teletext and on screen as a window which can be positioned, videotex. scaled, clipped and superimposed with computer video-to-film A process in which theatrical produc- graphics. The resulting images can then be digitally tions are first produced on videotape and then trans- stored for future reference. Video windowing con- ferred to film. Using the latest video technology trollers, which accommodate several signals con- including HDTV and electronic beam scanning, film nected at the same time, can usually receive inputs studios can lower production and post-production from a video camera, recorder, live TV or interactive costs. videodisc. video track One “strip” of information laid down vidicon A photoconductive tube whose charge-den- during recording onto a tape as the video head scans sity pattern is formed by photoconduction and stored across the tape. on a photoconductor surface (a target area coated video transmitter See Visual transmitter. with antimony trisulfide) that is scanned by an elec- video trigger A circuitry in many scopes that extracts tron beam, usually of low-velocity electrons. Its chief the horizontal and vertical sync signals from the in- applications are in industrial and other closed-cir- put video to trigger the scope. The simplest form of cuit TV cameras. video triggering lets the user trigger on all horizon- vidiot A video idiot, a zealous amateur. tal sync pulses (all lines) or all vertical sync pulses (all vidiplex A simple “multiplexing” method, where two fields). More advanced triggering systems let the user different TV program signals are transmitted sequen- pick the individual line and field to trigger on, al- tially in the odd and even fields of the TV frame. lowing any particular portion of the video waveform Equally suitable for transmission of NTSC, PAL or to be easily displayed. Also called TV trigger. SECAM signals. videotron (US) Monoscope. Viditel Videotex sytem, Holland. video up A directive to brighten the TV picture, some- vidkid American. A child who is a compulsive watcher times used in editing videotape. of TV or video. videowall An assembly of closely placed video screens Vieth-Muller horopter In 3D TV systems (with laser working in unison and designed to display various projectors) based on a spatial depth signal, the shape special visual effects such as single, “split” images of the horopter circle is the same as for human vi- across all monitors or multiple images. Presenting sion since both systems rely on sensing the relative larger-than-life images in stores, shopping malls, ex- angles of incoming light rays at the two sensor (or hibitions and other shows with large attendances, eye) positions. (The horopter circle is the set of points videowall presentations are instant attention-. on the retina perceived to have no retinal disparity Layouts are described by the number of monitors; for a given fixation point.) For the 3D TV systems e.g., five screens across and three screens high (15 the assumption is made that at great distances from monitors) is commonly known as a 5x3 videowall. the sensors (in relation to the distance the sensors videowall controller (VC) A sophisticated electronic are apart), the horopter circle between adjacent instrument or unit designed to program and ma- viewed points is a straight line if there is no change nipulate the images of a group of closely placed in distance from the sensors. TV screens usually on display at trade shows, spe- ViewCam Camcorder configuration, Sharp. The first cial events and other places with large audiences. model employs the Hi8 format, but others are ex- VCs usually provide such special features as inter- pected in standard 8-mm size. In place of a tiny

306 virtual vision

viewfinder, ViewCam has a 4" color LCD mounted HDTV image must be larger than the conventional beside the camera portion of the camcorder that is one. When viewed at six feet, the HDTV image must able to swivel 180 degrees vertically. The user can be not less than two feet high, and its diagonal is hold the instrument at waist level and look down then not less than four feet. Displays capable of pre- into the viewer, or shoot over the heads of the crowd senting such large images represent a major frac- by looking up into the viewer. The viewing screen tion of the HDTV set cost. can be twisted so that the operator can get into the viewing ratio (VR) The ratio of viewing distance to picture while viewing the LCD; the supplier remote picture height. With 440 active scanning lines (as in control cable operates the camera. 525-line broadcast systems) and a visual acuity 1.7', ViewCam TelePort video modem Device that en- individual scanning lines can be distinguished at a abled sending one detailed still-frame from a home VR as great as 4.4. At a VR of 4, the minimum usu- video recording every 20 s over ordinary phone lines; ally assumed for broadcast systems, individual scan- Sharp. ning lines can be faintly distinguished by a typical viewdata Syn.: videotex. An information retrieval sys- viewer. A VR of 3 or less is usually assumed in de- tem that uses a remote database accessible through signing HDTV, while a range of VRs from 4 to 8 is the public telephone network. Video display of the assumed for broadcast TV. data is on a monitor or TV receiver. Another name VIF Video intermediate frequency (IF). VIF and SIF refer for videotex, the original UK name for it; still used to circuits between the front-end tuner and video pro- widely in the UK. cessing circuits. The circuits are generally known as viewed picture format Combination of screen the VIF and SIF stages, and usually include both video aspect ratio and picture aspect ratio. and sound detectors (although there are many differ- viewfinder That part of the video camera that dis- ent configurations in present-day integrated circuit plays, by various methods, the scene that will even- sets). The basic function of the IF and video/sound- tually be recorded. There are three types of detector circuits is to amplify both picture and sound viewfinders. The optical, easiest to use and the least processing circuits, and to trap (or reject) signals from costly, is also the most limited since it cannot ac- adjacent channels. In some Hitachi literature, the video commodate different focal-length lenses or zoom IF is called the picture IF, or PIF. lenses and doesn’t “see” exactly what the lens sees. VIP Video Interface Port. The TTL (through-the-lens) optical finder has ad- VIR See Vertical Interval Reference. vantages over the optical type and costs more. It virtual editing A technique used by an editor to record sees exactly what the lens sees, and when the zoom only decisions concerning editing, not audio or video. lens changes its angle of view, so does the finder. This editing system, used chiefly with industrial But the TTL finder does not have the special fea- equipment, usually requires several decks and an tures of the third kind, the electronic viewfinder, editing machine. Selected scenes are recorded on which can be made mobile and can be used as a different machines, each scene with extended foot- playback monitor. age at the beginning and end. These scenes are then viewfinder diopter adjustment A video camera fea- shuttled to and from each machine. If a scene needs ture that allows the near- or farsighted user to ad- to be lengthened, the information is available. Fi- just the finder so that he or she can record without nally, all the scenes are then assembled in their proper the need to wear glasses. sequence and length on one machine for the fin- viewfinder inversion switch A control on some video ished edited version. For an early version of virtual cameras to permit the user to change the position editing, see Position identification. of the viewfinder so that it can be used by either the virtual reality (VR) Now a common high-tech right or left eye. This arrangement also allows for buzzword, which refers to the combined computer special up-side-down effects. and video technologies that place the observer in viewing distance Since the eye’s ability to resolve computer-generated situations for obtaining new detail is limited, the more detailed HDTV image and exciting visual experiences vicariously, training should be viewed more closely than is customary in in the operation of moving vehicles, gaining insights the conventional systems in order to realize the ben- into architectural structures, and playing games. efits of the higher-definition image. Full visual reso- Virtual Reality Modeling Language See VRML. lution of the detail of conventional TV is available virtual vision A production device that allows the when it is viewed at a distance equal to about six cameraperson to see behind, above, or to the left times the height of the display. The HDTV image or right without turning the head. A pair of goggles should be viewed from a distance of about three attached to a camera includes a tiny color TV with a times the picture height for the full detail to be re- small mirror in front of it. The picture is projected solved. If viewed at six times the height of the pic- from the mirror onto a visor. The user can view the ture, the extra cost of the HDTV set is wasted so far picture, or if the visor is clear, can see the live action as pictorial detail is concerned. It follows that the on the set.

307 Virtual Vision Sport

Virtual Vision Sport One of the first head-wearable, and then FF (or REW), the viewer can visually scan entertainment video display system introduced in the material, skip indesirable portions or locate par- 1993 by Virtual Vision, Inc. It was based on the ticular segments. When the fast scan mode is oper- “heads-up” displays used in aircraft, and uses a ating, the picture is “noisier” than usual and the single LCD and lens-mirror to display a picture that sound track is muted. Introduced by Sony, it is also appears to be as large as 60 inches, 8 to 15 feet in known as fast scan, fast search, high-speed picture front of the viewer. The picture was off to one side, search or rapid picture search, depending on the so the user could perform other tasks while watch- brand and model. ing it. Has evolved into other wearable display visual signal The picture portion of a TV signal. systems. Visual Solutions A family of AT&T products that VIS See Vertical interval signaling. handle videoconferencing, first announced on visible light Electromagnetic radiation visible to the March 23, 1993. human eye at wavelengths of 400-700 nm. visual transmitter The radio equipment that trans- vision carrier In TV transmission, the carrier wave that mits the video part of a TV program. Also known is modulated by the video signal. as picture transmitter; video transmitter. The visual vision frequency In TV transmission, the frequency and audio transmitters together are called a TV of the vision carrier. transmitter. vision pickup Camera tube. visual transmitter power The peak power output Visortron A video picture system developed by Sony, when transmitting a standard TV signal. using two small LCDs that are viewed through built- VITC SMPTE/ANSI time code. See Vertical Interval Time in lens systems. Introduced in 1993. Code. VISS VHS index search system. See Index search. VITS Vertical interface test signal to check the quality Vista 1. A videotex project in Canada in the early 1980s. of the transmitted TV picture. Two common VITSs 2. Visual System Transmission Algorithm. Also NYIT/ are known as NTSC-7 signals, identified by the in- Glenn VISTA. A wide-channel HDTV system devised dustry committee report that standardized them at the New York Institute of Technology by Dr. W. E. in 1975. These test waveforms are transmitted Glenn. Employs a standard NTSC 6-MHz channel and along with the video during the vertical blanking a 6-MHz augmentation channel. A variation employs period. The video quality of a TV set can be deter- one of two 3-MHz augmentation channels, in a 6- mined by examining the video waveform on a MHz channel shared by two stations. waveform monitor. visual acuity The smallest angular separation at which vizmo A rear-projection device used to insert a back- individual lines can be distinguished. Visual acuity ground into a TV broadcast. varies widely, as much as from 0.5' to 5' (minutes of VJ Video jockey. See Veejay. arc), depending on the contrast ratio and the keen- VLC Variable length coding. ness of the individual’s vision. An acuity of 1.7' is VM Very mature; see Movie rating systems. often assumed in the design of TV systems. VMI Video module interface. visual angle The pitch between pixels divided by the VO Voice-over. viewing distance and converted into minutes of arc. VOB files The default format of DVD movies. They visual carrier frequency The frequency of the TV car- usually contain multiplexed Dolby Digital audio and rier that is modulated by picture information. MPEG-2 video. VOB Files are named as follows: visual display unit (VDU) Another term for a com- vts_XX_Y.vob where XX represents the title and Y puter monitor. VDU is preferred in Europe. the part of the title. There can be 99 titles and 10 visualization A combination of computerized graph- parts, although vts_XX_0.vob never contains video, ics and imaging technology that provides high-reso- usually just menu or navigational information. lution, video-like results on the workstation or VOD See Video on demand. personal computer’s screen. voice-activated universal remote A device that rec- visually compressed digital A special kind of signal ognizes voice commands to operate a TV or VCR. in TV cameras to eliminate unnecessary data that Can be taught to recognize the voices of a few the eye cannot see. Developed at Florida Atlantic different users. University. voice activated video A microphone/camera that is visual polarity Refers to amplitude-modulated (AM) activated in response to voice. visual carriers. Positive polarity indicates that an in- voice generator A VCR feature that uses a microchip crease in light intensity causes an increase in radi- to produce a synthetic voice that takes the viewer ated power. Negative polarity (as used in the through each step of the programming process. US—Standard M) means that a decrease in light Once the user has finished entering the necessary intensity causes an increase in radiated power. data, the ersatz voice reviews the information be- visual scan A feature on a VCR that permits the rapid fore it is saved. This voice-coaching method of pro- viewing of a tape. By first pressing the Play mode gramming the VCR was designed to help users who

308 VTR type B format

are often baffled by the complexities of setting up ports advanced voice, data and image network com- their machines for recording future off-the-air shows. munication tools including Group IV Fax, high reso- The feature is also known as voice-prompt remote lution image transfer, file transfer, videoconferencing control programming. and switched data service via access to SprintNet, a Voice Interactive Programming VCR Matsushita. A large public data network. VCR that could be programmed by voice command. Vpp Peak-to-peak voltage. voice/music switch See Music/voice switch. VPS Video program system. voice-over (VO) Spoken narrative added to a picture VPS decoder See Video program system. either during recording or after the video camera VR Virtual reality. has completed shooting. Some cameras have a rear VRML Virtual reality modeling language, an ISO stan- microphone attached for adding voice-over while dard for 3D multimedia and shared “virtual worlds” shooting. on the Internet. voice-prompt remote control programming See VSAT Very small aperture terminal. A relatively small Voice generator. satellite antenna, typically 1.5 to 3.0 m in diameter, voice recognition The ability of a machine to recog- used for transmitting and receiving one channel of nize your particular voice. This contrasts with speech data communications. VSATs can often be seen on top recognition, which is the ability of a machine to un- of retail stores, which use them for transmitting the derstand human speech. day’s receipts and receiving instructions for sales, etc. voice switching Equipment used in voice and video VSB Vestigial sideband. conferences that is activated by sounds of sufficient VSM See Velocity scan modulation. amplitude—hopefully speech, but also loud noises. VSWR Voltage standing-wave ratio. The ratio of the Fast switching activates microphones so that only amplitude of the electric field or voltage at a volt- one conference participant can speak at a time. See age minimum to that at an adjacent maximum in a also Voice activated video. stationary-wave system, as in a waveguide, coaxial voice synthesis module A video game accessory that cable, or other transmission line. adds speech to particular game cartridges. VSYNC See Vertical sync. voltage-controlled crystal oscillator (VCXO) A crystal VT Videotape. oscillator circuit whose oscillator output frequency V-timing Relative (in discrete lines) of two sets of verti- can be varied or swept over a range of frequencies cal sync pulses held in synchronism. An error in V- by varying a DC modulating voltage. A VCXO is just timing results in vertical shifts of the TV picture. Syn.: like a voltage-controlled oscillator except that a vertical timing. VCXO uses a crystal to set the free-running fre- VTR Videotape recorder. An open reel video recorder quency. This means that a VCXO is more stable than using a supply reel and a take-up reel. VTRs are a VCO but it’s also more expensive to implement. mostly used industrially and professionally. Some of voltage-controlled oscillator (VCO) An oscillator these machines use direct-drive capstan servo mo- whose frequency of oscillation can be varied by tors that permit a VTR to be synchronized electroni- changing an applied voltage. Used in down-con- cally with any other format for editing purposes. In verters and satellite receivers to select from among addition, these motors permit remote control, re- transponders. quired when connecting the deck to an editor. VTRs voltage selector Syn.: clipper. See Limiter. may have other features, such as variable voltage voltage spike protector An accessory plug that ab- power, not found on home VCRs. The introduction sorbs voltage fluctuations usually attributed to power of digital technology to VTRs has enhanced video- line surges while permitting normal current flow. The tape recording possibilities in both audio and video spike protector, used to protect home computers areas. Because the quality of digital recording re- and stereos as well as video equipment, plugs di- mains constant, the process solves such problems rectly into the wall socket. as dropouts and moire, which have plagued con- voltage standing wave ratio See VSWR. ventional analog recording. In addition, digital tape voltage-synthesized tuner A tuning system, installed life is much greater than analog. on some VCRs, that requires manual tuning of those VTR lockup See Lockup. channels that are not part of the conventional VHS VTR type B format A professional/industrial reel-to- broadcasting band. These include many cable and reel 1" videotape system still popular in Europe but UHF channels. These tuners, as opposed to fre- superseded in the US, especially with TV networks, quency-synthesized tuners, provide a restricted num- by the C format. Relegated primarily to production ber of presets that can be kept in memory. However, use, the B format still boasts of many loyal users some VCRs offer as many as 100 presets that can who emphasize its special virtues. They find it use- be selected. See Frequency-synthesis tuner; Tuner. ful in post-production work and, because it was the VOS Video-on-sound. first format to feature long play, they prefer it for VPN 56 Sprint’s Switched 56-Kbps service, that sup- producing film-to-tape transfer masters. Also, the

309 VTR type C format

format is more economical, consuming over 200 feet has largely replaced the B format. Although the two of tape less per hour than its counterpart. Perhaps formats are similar in terms of the spec sheets, the C most important, its users consider it more reliable in units can produce variable fast speed functions for the field. But the B format faces a few shortcom- broadcasting and less costly functions such as freeze ings and some major problems. It uses what is called frame. In addition, a larger number of commercials a segmented head system, necessitating the addi- and programs are produced in this format, more com- tion of an expensive digital storage unit for certain panies offer a wider range of C models and the units functions such as freeze frame. The C units, on the are less expensive than their B counterparts. See VTR other hand, use a less costly time base corrector to type B format. obtain these same effects. The B machines lack the VU meter A device which registers audio loudness or ability to produce variable fast speed functions, softness. Some VU (volume unit) meters have gauges which the C units perform with relative ease. Finally, divided into segments that represent dB levels while many large studios and networks have adopted the others are divided simply into a safe zone and a red C format as their standard. distortion zone. VTR type C format A professional/industrial reel-to- VX format A now-defunct VCR system introduced by reel 1" videotape system used widely in the US, par- Quasar. The VCR was not compatible with any other ticularly by TV networks, local stations and studios. format. The type C, which has become the industry standard, VXO Voltage-controlled crystal oscillator.

310 W

W 1. White. 2. Watt. 3. Wide. 4. Width. 5. CATV switchable IRE filter, on/off gain boost, sweep and superband channel, 294-300 MHz. 6. The first let- the ability to accurately master pedestal adjustments. ter in the call letters of almost all US radio and TV waveform digitizer An electronic component de- stations east of the Mississippi. signed to connect to an oscilloscope, converting the wallpaper video In TV, slang for generic visuals, graph- scope to a digital storage unit. Using its own memory ics, or other stills or tape that can be used as intro- to produce waveform storage without a storage CRT, ductions or backgrounds, or that can be inserted in the digitizer generates its own CRT readouts for video a window on the screen. They are commonly used sweep rates, deflection factors, etc. in newscasts. waveform generator A professional device designed wall-ready display A flat TV screen that can be to be used with a standard oscilloscope. The wave- mounted on a wall. See Plasmavision TV. See also form generator converts composite color video sig- Flat television receiver. nals to standard waveform monitor signals. Typical WAN Wide area network. A network that uses com- generators show luminance, chrominance, direct mon carrier-provided lines that cover an extended picture information and other related data. geographical area. Contrast with local area network waveform monitor Cathode ray oscilloscope specifi- (LAN). The WAN uses links provided by local tele- cally designed for displaying TV signals. The X or phone companies and usually connects dispersed horizontal axis represents time, and the Y or vertical sites. axis represents the amplitude of the signal. WARC World Administrative Radio Conference. Sets waveform sampler An electronic unit that permits international frequencies. the measurement of the composite video signal so warm color A color with a yellowish or reddish cast, that video equipment can be adjusted for optimum akin to that of the sun, as opposed to cold color. signal quality. In addition, the sampler checks such warning light See Camera cue. video functions as amplitude and pedestal level. warp A digital video effect involving any two- or three- wavelets technology Asymmetrical video compres- dimensional change in shape (deliberate geometric sion algorithms providing the transmission of video distortion) of a picture. over existing copper-based networks without an wash Variant of background with a gradual change ISDN link. The technology compresses video so that from one color to another across the picture. Syn.: it can be transmitted over 28.8-Kb/s modems. It al- graduated matte. lows a compression ratio of as much as 120:1 while WAV Windows-compatible audio file format. A WAV still producing images that convey facial expressions file can be recorded at 11 kHz, 22 kHz, or 44 kHz, and sharp facial features. In addition, the algorithms and in 8- or 16-bit mono and stereo. lend themselves to scaling more effectively than the waveform A graphic picturization of an electronic sig- DCT algorithms currently used. As communications nal. All signals such as video, blanking and sync have bandwidth is constrained, the wavelets algorithms a distinct waveform that can be displayed on either reduce picture quality, whereas DCT algorithms drop an oscilloscope or waveform monitor. Some video entire frames and transmit a jerky picture. This fea- cameras display a waveform in the electronic ture is especially useful in LANs, where bandwidth viewfinder as part of the information needed for changes dynamically as usage varies. The technol- proper adjustment. Waveforms are most often al- ogy solves the problems of today’s video teleconfer- luded to in repair manuals as a point of reference. encing solutions and MPEG-4 still image compression Each waveform should be adjusted to match its is based on wavelets. drawing in the manual. wave resonance A technique employed chiefly in waveform color/picture monitor A professional/in- some compact TV receivers to enhance the bass dustrial instrument designed chiefly to be used in sound. This is accomplished by separating the bass the field. The unit provides such features as on/off from the treble and mid-range tones and reproduc-

311 Weber’s law

ing and improving it so that it sounds more realistic. the IRE number, the better the color purity. A per- TV receivers with wave resonance try to emulate fect white balance would measure zero IRE. Adjust- large, full sound within the limited, available space ments for white balance are necessary when using of their cabinets. a color video camera so that all color and light val- Weber’s law The visibility of an object in an image ues register as true as possible. Some cameras have depends on the brightness contrast between differ- automatic controls and meters. Others have flash- ent areas. As in the case with most physical sensa- ing warning lights and a hue control dial that is ro- tions, the magnitude of this perception tends to be tated until the appropriate white balance has been proportional to the brightness ratio rather than to reached. the absolute brightness difference. This is expressed white balance control A feature on a video camera in Weber’s law: The increase in stimulus necessary to help set or define colors by matching the white to produce an increase in sensation of any of our balance of the camera exactly to prevailing light con- senses is not an absolute quantity but depends on ditions. There are different kinds of controls for this the proportion that the increase bears to the imme- purpose. Red/blue controls are convenient but inef- diately preceding stimulus. The perception of con- fective with green. Independent red and blue con- trast between two areas also depends on the trols can affect green by being turned all the way sharpness of the boundary. If the boundary is sharp, up (reducing green) or down (increasing green). a much smaller brightness difference can be Some cameras provide two tint dials: one for red perceived. and blue and one to balance green and magenta. WebTV Microsoft trademark for set-top boxes used These controls are operated either automatically, by for interactive and regular TV. Lets users access the meters, by indicator lights, by click-stop positions, Internet via connections to a standard TV and a etc. There are various ways to control white balance. phone line. Supports WebPIP, which lets users si- One approach is to factory-preset the red-green-blue multaneously view web pages and TV programming signals to tungsten light and place color conversion on the same screen. The WebTV service is now called filters behind the camera lens. A switch then deter- the MSN TV service. mines indoor/outdoor position (one filter) or, in some wedge A convergent pattern of equally spaced black cases, indoor/hazy/sunny (two filters). Another tech- and white stripes (usually from three to seven, on a nique for white balance control is to factory-preset gray background), that vary in repetition pitch so as average lighting condition such as tungsten, hazy to give the appearance of a wedge. Used in a TV light and bright sunlight. The proper level is then test pattern to indicate resolution. Syn.: wedge mire. set electrically by a switch. For more flexibility, a red/ wedge mire See Wedge. blue knob is added to change the relative balance weighting noise, audio component Human hear- of red and blue in the picture. The knob controls red ing is not equally sensitive to all frequencies. This is at one end of its turn and blue at the other. The especially true for low-level sounds, such as those in effects can be witnessed on a color monitor or on the background noise of audio systems. Our ears cameras with a meter. Expensive cameras feature are much more sensitive to midfrequencies than to Automatic white balance, while others provide three ultra-low and ultra-high tones. It follows, then, that controls: a switch to choose a filter or an electronic noise delivered by a component only at the frequency setting; then auto white balance is set; finally, the extremes would be less bothersome than an equal manual red/blue knob is used to check or override amount of noise at midfrequencies delivered by an- the white balance. other component. Because of this, a system of mea- white balance hold A video camera feature that, surement known as weighting has been developed, when engaged, “sees” a white object and locks the that attempts to measure signal/noise ratios in terms unit into this position to maintain proper color as of their subjective effect upon the listener. This sys- long as lighting conditions remain the same. tem employs a specific filter so that low and high whiteboard An electronic device on which text can frequency noise makes less of a contribution to the be written and one or more copies printed using final signal/noise readings than midfrequency noise. optical sensors. The material can be transmitted over If you see a specification preceded by the notation telephone lines and viewed on a TV set, so that a “A-weighted,” this method of measurement was whiteboard can be part of a teleconference. used. white clip After emphasis, the positive-going spikes wh White. (overshoot) of the video signal might be too large whip Syn.: zip pan. See also Swish pan. for safe FM modulation. A white-clip circuit is used white The mixture of red, green and blue in color TV. to cut these spikes off, at an adjustable level. See white balance Refers to the amount of color that can Dark clip. be seen on a neutral object when the white balance white clip level extension Part of the high-quality controls on a video camera are adjusted for opti- (HQ) circuitry of particular VCRs. The white clip level mum. White balance is measured in IRE: the lower phase of the circuit is designed to provide sharper

312 wide screen signaling

edges and a more distinct contrast between light whiter-than-white An excursion of the TV waveform and dark portions of the picture. signal above the normal peak (white) level. white compression (or white crushing) In TV, reduc- white saturation White compression. tion of the gain at signal levels corresponding to white set See White level set. white compared with the gain at black and mid- white uniformity On inferior TV sets, white objects grey levels. The effect of white compression is to on the screen may not always appear as white as reduce the visibility of detail in highlight areas of they should. White objects farthest from the screen’s the reproduced image. Also called white saturation. center may display as gray. A 100 IRE white field is white crushing A form of peak distortion in the TV used to measure how consistently whites are repro- image resulting from amplitude nonlinearity, affect- duced on the set without any gray areas or areas of ing the higher amplitude portions of the video sig- color contamination. nal. Since the signals corresponding to white are at whiz Syn.: zip pan. the peak of the waveform, they are often the first wholesale politics Chiefly American. Electoral cam- part to be distorted. They usually distort to a greater paigning via the media, especially TV, rather than by degree than signals corresponding to other tonal the politician’s traditional methods of addressing values, with the possible exception of signals at or meeting, canvassing, etc. near black. The nonlinearity causes the video signal Wide Area Network (WAN) A data network typically to be compressed, so that the tonal values no longer extending a LAN outside the building, over telephone have the same range. The resulting compression on common carrier lines to link to other LANs in re- the TV screen is a loss of detail in the whites of the mote buildings in possibly remote cities. A WAN typi- picture. If the amplitude distortion is severe, the cally uses common-carrier lines. A LAN doesn’t. white compression becomes white clipping, show- WANs typically run over leased phone lines—from ing as a complete loss of tonal detail in the white one analog phone line to T1 (1.544 Mbps). The jump parts of the picture. between a LAN and a WAN is made through a de- white field brightness The upper limit of the TV trans- vice called a bridge or a router. fer function (S-shaped curve). It is usually established wide-angle lens An optical lens with a very short fo- by the limitations of the display device, ordinarily a cal length; a lens that has a large angular field (angle kinescope. of view), generally greater than 80 degrees. white flag See Multiburst waveform — NTSC VITS. wideband Broadband. Refers to a channel wider in white level (US: reference white level) TV signal level bandwidth than a voice-grade channel. Denoting representing full peak excursion above or below the an electronic device or circuit, such as an amp, that sync level, according to whether modulation is posi- operates satisfactorily over a large range of input tive or negative. It represents a peak-white object. signal frequencies. This level defines what white is for the particular wideband axis The direction of the phasor that rep- video system. In black and white TV, the maximum resents the fine chrominance primary (the I signal) permitted level of the picture signal (or, in color TV, in NTSC color TV; it has a bandwidth from 0 to of the luminance component). 1.5 MHz. white level set White set. A camera control that es- wideband switch Switch capable of handling chan- tablishes the luminance level for a color camera. nels wider in bandwidth than voice-grade lines. Ra- white light Light that is comparable in wavelength dio and TV switches are examples of wideband content to average noon sunlight. switches. white object An object that reflects all wavelengths wideband video amplifier An electronic circuit, of- of light with substantially equal high efficiencies and ten found in TV monitor/receivers, designed to cap- considerable diffusion. ture and reproduce the entire range of an incoming white peak (US) A peak excursion of the picture signal video signal. The wideband video amplifier boosts in the white direction. Syn.: peak white, picture white. the video signal by rasing its frequency response, white peak carrier Part of a carrier wavelength that which affects the horizontal resolution. TV monitor/ holds the luminance signal. When the white peak receivers equipped with this active circuitry often carrier is increased, the amount of space available attain 800 lines or more of horizontal resolution. for recording video detail on tape is expanded. This wide open Descriptive of a lens set at its lowest f-stop contributes to the number of horizontal lines of reso- rating so that the iris is opened as wide as possible. lution, which, in some cases, may be raised to 400 widescreen Viewed picture format with aspect ratio lines or more. higher than in conventional TV and full screen oc- white peaking circuit Advanced circuitry used on cupation—e.g., 16:9. This is the aspect ratio used some TV monitor/receivers designed to produce a by HDTV. purer white on screen. This is accomplished by re- wide screen signaling (WSS) 1. Method of transmis- ducing the red beam of the electron gun and ampli- sion of information about aspect ratio and some fying the blue beam. other parameters towards the TV receiver by data

313 width

inserted in the vertical blanking interval. 2. Data em- ture is produced from part of an HDTV source pic- bedded in the video signal containing information ture with on-line control of its size and position. Syn.: on the image aspect ratio and its position, on helper zoom mode. signal presence, on the position of the subtitles and window of correction The maximum amount of time on the camera/film mode selection. In 625-lines sys- base error a time base corrector (TBC) can correct, tems—e.g., in the PALplus system—WSS data are measured in video lines. A TBC with a four-line win- transmitted during first half of TV line 23. WSS may dow might be fine for VTRs and tapes that never be used on (B, D, G, H, I) PAL line 23 and (M) NTSC leave the climate-controlled confines of a studio, but lines 20 and 283 to specify the aspect ratio of the it would be almost useless with tape that is shot in program and other information. 16:9 TVs may use the field. A TBC with a 32-line window costs a good this information to allow displaying of the program deal more money, but it should be able to handle in the correct aspect ratio. ITU-R BT.1119, ETSI anything shot in the studio or the field. EN300294 and IEC 61880 specify the WSS signal for Windows CE CE is a 32-bit real- PAL and NTSC systems. EIAJ CPX-1204 also specifies time embedded operating system (RTOS) designed another WSS signal for NTSC systems. from the ground up to empower the development width 1. The horizontal dimension of a TV picture. 2. of a new range of emerging computing appliances, The time duration of a pulse. including set-top boxes, digital versatile disc (DVD) width control 1. In TV receivers, the control that de- drives, entertainment consoles, smart phones, highly termines the amplitude of horizontal deflection and portable and personal computing devices like hence the width of the displayed picture. The con- handheld computers, and home appliances. Win- trol is often a variable inductor connected in series dows CE is modular, allowing use of a minimum set with the line deflection coils. 2. In stereo sound of software components needed to support receiver reproduction, a control that determines the appar- requirements. This uses less memory and improves ent width of the sound source. It is often a variable operating system performance. Windows CE pro- resistor bridging the two channels and, in the zero- vides a subset of the Win32 application program resistance position, parallels them so that the sound interface (API) set, which provides an effective appears to originate from a point source located amount of application source-code level portability midway between the two loudspeakers. and compatibility and user interface consistency with wild footage Audio tape recorded out of sync with other Microsoft Windows operating systems and any particular video picture for use in post-produc- Windows applications. tion as an audio track; video tape recorded without Windows Media Player Leading digital media plat- audio for use as visual material in post-production form for PCs that delivers the most popular stream- to which narration will be added. ing and local audio and video formats, including ASF, wind The manner in which magnetic tape is wound WAV, AVI, MPEG, QuickTime, and more. Windows onto a reel. In an A wind, the coated surface faces Media Player can play anything from low-bandwidth the hub. In a B wind, the coated surface faces away audio to full-screen video. from the hub. wind screen Similar to a pop filter; a heavy foam rub- wind noise switch A camcorder feature that helps to ber cover for a microphone, used outdoors to di- minimize some types of unwanted extraneous au- minish wind noise, etc. dio interference that may reach the built-in micro- wipe A special effect in which one image replaces phone. another by means of a predetermined pattern. In window 1. Test pattern in a form of a white box on a video, hundreds of different wipes can be produced black or gray background. A change of window size by using a professional device called a mix/effects provides an easy way to control the average picture switcher. Two of the more popular wipes are the level. 2. A mode of test pattern generation where rotary wipe and matrix wipe. the main test signal is gated by a window signal to wire broadcasting The distribution of sound and/or provide a gray or black background at the main test TV programs to a number of receivers over a wired perimeter. 3. In 3D-TV systems, the position of a distribution system using audio frequencies or modu- reference frontal place. See also Depth matrix. lated carrier frequencies. window dub A copy of a videotape that contains a wired city A city or area with a high level of fiber box in the lower third of the tape that displays the optic networks and Internet services; popular slang time code on the tape. Window dubs are generally in U.S. for a city that is attuned to the latest in tele- only used when logging tape and during the off- communications and information technology. line edit. wireless cable A TV service in which a TV signal is windowing The videotape slippage that sometimes re- received from a satellite and retransmitted to a sults from a loosely wound spool; also called clinching. viewer’s rooftop antenna on a superhigh-frequency window mode [of HDTV down conversion] Mode microwave channel. See Multichannel Multipoint of HDTV down conversion where the output TV pic- Distribution Service (MMDS).

314 WYSIWYG

Wireless Cable Association (WCA) An organization hypertext servers (HTTP servers) that allows graph- of cable operators who use microwave transmitters, ics, text, sound files, video files, etc., to be mixed as opposed to coaxial cable, to broadcast cable pro- together. gramming to subscribers. Wireless cable service re- WORM Write once, read many times. Refers to the type quires a microwave antenna and an addressable of storage devices that can be written to only once, receiver/descrambler. See Multipoint distribution ser- but read many times. In other words, once the data is vice. written, it cannot be erased. Being optical, WORMs wireless camcorder microphone A short-range, low- provide very high recording densities and are remov- power FM transmitter. Consists of three main sec- able, making them useful for archiving. tions: the microphone element, the audio amp, and wow Refers to tape speed variations that result in the the RF oscillator. The best receiver for the wireless distortion of the audio signal. camcorder microphone is a good-quality (sensitive) Wraase A family of amateur SSTV transmission modes Walkman-type FM receiver because it is portable and first introduced with Wraase SC-1 scan converter lightweight. The only requirement for the receiver is developed by Volker Wraase, DL2RZ, of Wraase that it must have a headphone jack. Electronic, Germany. wireless infrared See Remote control. wraparound controls In videotex, a set of rules that wireless remote control See Remote control. govern what happens when the active position at- wireless A device (transmitter and re- tempts to move off the defined display area. ceiver) to extend cable, TV and VCR signals through- wrap-around theater sound Surround sound. out a house. writing speed The effective speed at which video- Wollaston prism In a laser-type videodisc player, an tape moves past the recording heads in relation to optical component through which the laser passes the tape travel speed. On VHS and VCRs, the video before reaching the disc surface. It then returns in heads rotate at 1800 rpm while the linear tape speed polarized form. is (3.34 cm or 1.32" per second in SP. Therefore, the word graphics The titles, credits, announcements or effective writing speed equals 230 ips for VHS. See other word messages that appear superimposed on also Transverse recording. the TV screen. Word graphics may crawl vertically WSS Wide screen signaling. up or down on the screen or move horizontally across WST World Standard Teletext; World System Teletext. the bottom, announcing news flashes, election re- Based on the British teletext standard in which a turns and so on without interrupting program con- one-to-one correspondence exists between trans- tent. Word graphics are usually white or light-colored mitted characters, page memory, word addresses and against a dark background, often created by means the display screen character locations. Over 98% of of a technique called “keying.” the world’s TT decoders are WST compatible. word register See Digital image superimposer. WTBS A superstation transmitted by satellite, offering World Administrative Radio Conference (WARC) The baseball, basketball, professional wrestling, movies, ITU meetings that work out standards for interna- TV and some original shows. WTBS, owned tional radio communications (including satellite TV). by Ted Turner, was the first superstation in the US. It World Standard Teletext (WST) A British-developed began operations in 1976 and offers programming teletext system. Based on the successful experiences 24 hours a day. with both the Oracle and Ceefax one-way teletext W-VHS Compatible analog HDTV recording system, JVC. operations in the UK, WST has been aggressively The system is available in Japan for recording and promoted as the standard for all teletext systems. playback of standard, widescreen, and HDTV signals. See also Electra. www See World Wide Web. World System Teletext See WST. WYSIWYG Stands for “what you see is what you get” World Wide Web Another name for the Internet, used but screens don’t always work that way in reality. loosely. Actually refers to the entire constellation of Refers to the accuracy of a screen display in show- resources that can be accessed via Gopher, FTP, HTTP, ing how the final result will look—for example, how telnet, , and other tools, plus the universe of a brochure will appear in it’s final printed form.

315 X

X 1. Frequency band 8-12 GHz. 2. No one under 17 welded joints and other industrial X-ray applications. admitted; see Movie rating systems. The technique gives instant images, without the time X-1 The original Beta tape speed, providing 60 min- and cost of developing film. It can show enlarge- utes of recording and playing time on an L-500 vid- ments of as much as 50x, for detecting small de- eocassette. Today, Beta I is reserved for professional fects. For permanent records, a VTR can be added, and industrial machines. or the images on the TV screen can be photographed XGA Extended Graphics Array. Computer graphics dis- selectively. The TV monitor can be located remotely play standard introduced by IBM in 1990. XGA-2 from the inspection area, so personnel are protected offers 800 x 600 pixel resolution in true color (16 from harmful x-ray radiation. million colors) and 1024 x 768 resolution in 65,536 XSVCD Abbreviation for eXtended Super VideoCD. colors. See Super VideoCD. x-ray television A closed-circuit television system re- XVCD Abbreviation for eXtended VideoCD. See places photographic film during X-ray inspection of VideoCD.

316 Y

Y 1. Yellow. 2. In NTSC, PAL, SECAM and component people use the YcbCr notation rather than Y’CbCr video, the luminance signal, so named because it is or Y’Cb’Cr’. the Y-axis of the chart of the spectral sensitivity of the Y/C connection Popular two-signal interface format,

human visual system. 3. In HDMAC, YL and YH are where Y is a luminance component and C is a the low- and high-frequency components of the lu- chrominance component at NTSC or PAL color sub- minance signal. carrier frequency. Because the C signal is transmit- Y adapter A connecting audio cable that is used to ted separately there are no cross-effects, so the join two lines into a single input or output. The Y decoded picture looks almost as good as the origi- adapter can be applied to many tasks, such as copy- nal. The Y/C interface is used in DVD players, S-VHS ing a stereo tape onto a mono VCR. Using the ste- and 8-mm VCRs, set-top boxes, televisions, plus re- reo recorder as the playback machine, the owner lated equipment. Syn.: S-Video; Y/C interface. connects the Y adapter from the two audio channel Y/C connector A multipin input that helps to eliminate outputs of the stereo to the single audio input of several types of video interference by processing the the mono VCR. It comes with various plugs or jacks. brightness (Y) and (C) portions of the signal sepa- Also known as Y connector or Y splitter. rately. Previously, the luminance and chrominance sig- Yagi aerial A sharply directional aerial array from which nals were mixed and had to be separated by the TV most aerials used for TV have been developed. The set. By avoiding this intermediate step, the Y/C con- active part of the aerial consists of one or two di- nector eliminates such interference problems as pole aerials together with a parallel reflector and a crosstalk. Y/C connectors, usually installed on more set of parallel directors. The directors are relatively recent TV monitor/receivers and other similar equip- closely spaced, being from 0.15 to 0.25 of a wave- ment, accept connections from DVD players, Super- length apart. When the aerial is used for transmis- VHS and Beta VCRs, set-top boxes, and some models sion, the directors absorb energy from the back lobe of laserdisc players. These inputs are sometimes of the dipole radiation pattern and re-reflect it in known as S-video inputs or S-connectors. the forward direction; the major lobe is thus rein- YC-2 board Y (luminance) signal and C (chroma) sig- forced at the expense of the back lobe. When used nal record/playback circuits, Betamax VCR. for reception the inverse process occurs, causing the Y/C interface See Y/C connection. signal to be focused on the dipole. Y/C separator A Y/C separator is what is used in a yaw A term borrowed from aeronautics to describe NTSC/PAL decoder to separate the luma and chroma. the effective static rotation of the aircraft about an This is the first thing that any video decoder must imaginary vertical pin. Thus, the aircraft can be mov- do. The composite video signal is fed to a Y/C sepa- ing forward but not necessarily facing forward, off- rator so that the chroma can then be decoded fur- set by the yaw angle. In digital video effects, this ther. term can be used to describe the positioning of the Y/C video See S-video. effect (rotation about the Y axis). yellow The color obtained by mixing equal intensities Y/C Y equals the luminance portion and C equals of green and red light. the chrominance portions of the video signal. A yield strength Refers to the degree of force neces- Y/C piece of equipment or system will keep the sary to produce a 5% elongation in a videotape. If a components separate as much as possible. See tape is stretched beyond this point, it may affect the S-video. overall quality so that the tape is unwatchable. Y’CbCr, YCbCr Y’CbCr is the color space defined by Y’IQ, YIQ 1. The components of the NTSC system: lu- BT.601 and BT.709. Y’ is the luma component and minance and chroma. 2. Also Y’IQ. A color space the Cb and Cr components are color difference sig- optionally used in the NTSC video system. The Y’ com- nals. The technically correct notation is Y’Cb’Cr’ since ponent is the black-and-white portion of the image. all three components are derived from R’G’B’. Many The I and Q parts are the color difference compo-

317 Y matrix

nents; these are effectively nothing more than color minance and chroma. 2. Also Y’UV. The color space placed over the black and white, or luma, compo- used by the NTSC and PAL video systems. As with nent. Many people use the YIQ notation rather than the Y’IQ color space, the Y’ is the luma component Y’IQ or Y’I’Q’. The technically correct notation is Y’I’Q’ while the U and V are the color difference compo- since all three components are derived from R’G’B’. nents. Many people use the Y’UV notation when Y matrix A circuit to construct luminance signal ac- they actually mean Y’CbCr data. Most use the YUV cording to the equation Y = 0.299R’ + 0.587F’ + notation rather than Y’UV or Y’U’V’. The technically 0.114B’ (SDTV) or Y = 0.213R’ + 0.715G’ + 0.072B’ correct notation is Y’U’V’ since all three components (HDTV). are derived from R’G’B’. yoke Deflection yoke. See also Flyback transformer. YUV9 Intel’s compressed YUV (actually YCbCr) format, Y’PbPr, YPbPr Y’PbPr is a scaled version of the YUV providing a compression ratio of up to 3:1. The pic- color space, with specific levels and timing signals, ture is divided into blocks, with each block compris- designed to interface equipment together. Con- ing 4 x 4 pixels. For each block, 16 values of Y, one sumer video standards are defined by EIA-770; the value of U (Cb), and one value of V (Cr) are assigned. professional video standards are defined by numer- The result is an average of nine bits per pixel. ous SMPTE standards. VBI data formats for EIA-770 YUV12 Intel’s notation for 4:2:0 YCbCr stored in are defined by EIA-805. Many people use the YPbPr memory in a planar format. The picture is divided notation rather than Y’PbPr or Y’Pb’Pr’. The techni- into blocks, with each block comprising 2 x 2 pixels. cally correct notation is Y’Pb’Pr’ since all three com- For each block, four values of Y, one value of Cb, ponents are derived from R’G’B’. and one value of Cr are assigned. The result is an Y signal Luminance signal. average of 12 bits per pixel. Y’UV, YUV 1. The components of the PAL system: lu- YUY2 Intel’s notation for 4:2:2 YCbCr format.

318 Z

zap The use of a remote-control device to change TV per line. The video encoder applies adaptive + trans- channels or turn off the sound during commercial form/sub-band coding. Potentially, a full picture’s messages; the use of a device to blip out commer- content is retained but in flat areas with little detail cials, as with a pause button in videotaping; also called and little variation in the image, little information is zapping. The A.C. Nielsen company defines the term transmitted. This makes time available for the trans- as the practice of eliminating commercials on a vid- mission of more information needed for areas of eocassette during playback, but most industry practi- greater detail. Adaptation and control information tioners use zipping to describe that process. are transmitted separately during the vertical blank zapping See Zap. interval as part of the digital data signal. Z-axis modulation Intensity modulation. zero frame dissolve A dissolve with a duration of Z.B. An instruction to a camera operator to zoom back. zero frames, equivalent to a cut; a technique used zelda A mannequin, generally just the head and shoul- to synchronize two source machines so that manual ders, used to focus film or TV cameras. audio or video transitions can be made between zeroing Zeroing is what’s done to the bank of com- them. parators in a CMOS flash A-to-D converter to keep zero-subcarrier chromaticity The chromaticity that them accurate. Without zeroing, the comparators is intended to be displayed when the subcarrier am- build up enough error so that the output of the flash plitude is zero in a color TV system. ADC would no longer be correct. To solve the prob- zip pan A rapid movement of the TV or film camera; lem, the comparators are “zeroed,” or the accumu- also called blur, whip, or whiz. See also Swish pan. lated error removed. zipper 1. On a TV or broadcast, an inconsequential, Z demodulator Same as the X demodulator, except it humorous, or even zany final item; also called kicker. is for the blue (B-Y) signal. 2. See Creepy-crawlies. zebra tube A color display tube, so called from the zipping TV-commercial avoidance during playback ac- vertical red, green and blue-emitting stripes that complished by fast-forwarding through taped make up the phosphor screen, that closely resembles commercials. the apple tube. It is one of the index types and, like zonal mixing Keying mode when a key signal of the the apple tube, makes use of index strips over the mixer (e.g., a diamond-shaped wipe pattern) comes phosphors. These index strips, instead of giving out from a source other than the video that will eventu- secondary electrons, emit ultraviolet (UV) light that ally fill the hole. The key source, in this case, may be is amplified in a photomultiplier. By ingenious cir- either internal or external. Syn.: in-lay. cuitry, the need for a separate pilot electron beam is zone satellite See Satellite focus. eliminated. zoom To increase or reduce the size of a TV image, Zenith Spectrum-Compatible HDTV system Also usually in a gradual way. Zooming can be accom- SC-HDTV system, Spectrum-Compatible HDTV sys- plished by means of electronics or optics. See tem. A single-channel noncompatible simulcast Digital zoom. HDTV system specifically designed to coexist with zoomed video port Used on laptops, the ZV Port is a NTSC in the existing TV bands of terrestrial broad- point-to-point uni-directional bus between the PC casting. Sharing of the existing TV bands requires Card host adapter and the graphics controller, en- the use of the so-called “Taboo” channels. The cam- abling video data to be transferred real-time directly era of the SC-HDTV system progressively scans 787.5 from the PC Card into the graphics frame buffer. lines, at 59.94 frames/s for a horizontal deflection The PC Card host adapter has a special multime- frequency of 47.203 kHz, exactly three times the dia mode configuration. If a non-ZV PC Card is NTSC rate. The R, G, B bandwidths extend over 37. plugged into the slot, the host adapter is not The aspect ratio is 16:9. The number of active lines switched into the multimedia mode, and the PC Card per frame is 720 and there are 1280 active pixels behaves as expected. Once a ZV card has been

319 zoom in

plugged in and the host adapter has been switched depends on how close or large the subject appears to the multimedia mode, the pin assignments in the finder compared to its original distance or change. size. The typical zoom ratio is 6:1 although some zoom in Expansion of the picture details within the cameras feature an 8:1 ratio. Extender lenses are zoomed picture area. Syn.: expand. available; these extensions increase the zoom ratio. zoom lens Special lens that has a continuously vari- For example, a particular extender lens may increase able focal length (and thus magnification) over a cer- an 8:1 ratio to a 12:1 telephoto zoom. tain range without moving the camera. Most video zoom ring A control encircling the zoom lens. Its back- cameras come equipped with a standard 6:1 zoom and-forth movement permits the mechanical adjust- lens (relationship of the longest focal length to its short- ment of the focal length. When the zoom ring is est) while some consumer models offer an 8x, 10x or rotated, the focus is changed. Other zoom controls even 12x variable power zoom lens. The zoom may go are the zoom ring lever and the power zoom. from wide angle through normal viewing to close-up zoom ring lever A control on the zoom lens with an or vice versa. This feature is usually adjusted by a zoom extended handle to help facilitate changing the fo- ring, a zoom ring lever or a power zoom that works cal length. An intermediate control, it is easier to electronically. The focal lengths for video lenses are dif- operate than the basic zoom ring, but not as so- ferent from those used in still photography. For ex- phisticated as the power zoom. ample, a 12-75mm range in video would be zoom To increase or reduce the size of a TV image, equivalent to a 45-350mm lens on a 35mm camera. usually in a gradual way. zoom light An accessory normally used indoors with ZV port See Zoomed video port. a video camera. Some zoom lights can be connected zweiton A technique of implementing stereo or dual- to wall outlets while other models, if used in the mono audio for NTSC and PAL video. One FM sub- field, can be plugged into the cigarette-lighter socket carrier transmits a L+R signal, and a second FM of an automobile. subcarrier transmits a R signal (for stereo) or a sec- zoom mode Mode of HDTV down-conversion in which ond L+R signal. It is discussed in ITU-T BS.707, and the output picture is produced from part of an HDTV is similar to the BTSC technique. source picture with on-line control of its size and Z-wheel In the digital video effects sense, it describes position. Syn.: window mode [of HDTV down con- a single coordinate control used for changing ef- version]. fects parameters in the Z-axis (perpendicular to the zoom out A zoom effect with objects being decreased screen plane). Syn.: spinwheel. in size. Syn.: compression; reduction. Zworykin, Vladimir (1889–1982) Russian inventor of zoom ratio The telescoping range of a lens. A math- the iconoscope, a television transmitting tube, and ematical expression of the two extremes of focal the , a CRT that projects pictures it re- length available on a particular zoom lens. The ratio ceives onto a screen.

320 APPENDIX A ASSOCIATIONS

Advanced Television Enhancement Forum (ATVEF) http://www.atvef.com/

Advanced Television Forum (ATVF) http://www.atvf.org/

Canadian Association of Broadcasters http://www.cab-acr.ca/

CEA Consumer Electronics Association (formerly CEMA) http://www.ce.org/

Digital Display Working Group http://www.ddwg.org/

Digital Television Group http://www.dtg.org.uk/

DTVIA Digital Television Industrial Alliance of China Enterprise Confederation http://www.dtvia.com/

DVB-MHP DVB-MHP (Multimedia Home Platform) http://www.mhp.org/

DVDA DVD Assocation http://www.dvda.org/

ETG Entertainment Technology Group http://www.etg.tv/

321 ICDIA International CD-i Assocation http://www.icdia.org/

IEEE 1394 Trade Organization http://www.1394ta.org/

IMTC International Multimedia Telecommunications Consortium http://www.imtc.org/

Korea Multimedia Association http://www.multimedia.or.kr/

Linux4.tv http://www.linux4.tv/

LinuxTV.org http://www.linuxtv.org/

Media Communications Association http://www.mca-i.org/

MHP Forum Multimedia Home Platform Forum http://www.mhp-forum.de/

MIDI Manufacturers Association http://www.midi.org/

MPEG 4 Industry Forum http://www.m4if.org/

Multimedia Benchmark Committee http://www.spec.org/gpc/

Multimedia CD Consortium Marantz Japan, Inc. 35-1, 7-Chome, Sagamiono Sagamihara-shi, Kangawa Japan, 228 (81) 427-44-0431 FAX: (81) 427-48-1007

322 National Association of Broadcasters http://www.nab.org/

RTSP.org Real Time Streaming Protocol information and updates http://www.rtsp.org/

Satellite Broadcasting and Communications Association of America (SBCA) http://www.sbca.com/

323 [This page left blank.] APPENDIX B STANDARDS ORGANIZATIONS

AES Audio Engineering Society http://www.aes.org/

ATSC Advanced Television Systems Committee http://www.atsc.org/

DAVIC Digital Audio Visual Council http://www.davic.org/

DVB Digital Video Broadcast http://www.dvb.org/

DVD Forum http://www.dvdforum.org/

EBU European Broadcasting Union http://www.ebu.ch/

EIA Electronic Industries Association http://www.eia.org/

ETSI European Telecommunications Standards Institute http://www.etsi.org/

IEC International Electrotechnical Commission http://www.iec.ch/

IEEE Institute of Electrical and Electronics Engineers http://www.ieee.org/

325 ISO International Organization for Standardization http://www.iso.ch/

ISMA Internet Streaming Media Alliance http://www.isma.tv/

ITU International Telecommunication Union http://www.itu.ch/

MPEG Moving Picture Experts Group http://mpeg.telecomitalialab.com/

OpenCable http://www.opencable.com/

SCTE Society of Cable Telecommunications Engineers http://www.scte.org/

SMPTE Society of Motion Picture and Television Engineers http://www.smpte.org/

TV Anytime http://www.tv-anytime.org/

TV Linux Alliance http://www.tvlinuxalliance.org/

VESA Video Electronics Standards Association http://www.vesa.org/

326