Introduction to Course 2EC411 Digital Television Engineering
Dr Usha Mehta Syllabus Calendar Lesson Plan Textbooks: Modern Television Practice by R. R. Gulati, New Age International Pub. Digital Television by Herve Benoit, Third Edition, Elsevier Composite Satellite and Cable Television by R. R. Gulati, New Age International Pub.
19-08-2014 2 Course Learning Outcomes
This course is being offered as a complete application/case study for involving mostly all concepts related to electronics and communication engineering. Upon completion of this course, students will be able to: Understand the concept of real signals like audio and video, color signal and its effective conversion into electrical signal Correlate the concept of preparation and processing of signal required before transmission like amplification, modulation etc. studied in earlier semesters with real life application. Understand the concept of transmission and receiver and able to prepare block level transmitter/receiver for given application. Analyze various digitization methods/standards and their effectiveness. Select the necessary digitization standards for given application Understand the concept of JPEG, MPEG, HDTV, TV over IP etc.
19-08 -2014 3 Self Learning
Sr. Topics No. 1 Recent Developments in Digital Television Pl. refer: esaki.ee.boun.edu.tr/~morgul/Recent%20TV.pdf
2 Advances in TV/computer motion monitoring Pl. refer: http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=96082&url=htt p%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnum ber%3D96082
3 Pl. learn following topics from net and go through it in detail Video-On-Demand Picture-In-Picture Technology Mirror TV
19-08-2014 4 Assessment Methods
Course TERM ASSIGNMENT (TA) LPW Subject Subject Course Faculty L T P C Code Name Coordinato Involved rs Assig No. of Term nmen 2 class Practica Conti. End ts Tests Special Assignment * l Asset Exam
Type of Assignme No. WT nt WT
WT WT 2EC41 Digital Dr. Usha Prof. 3 0 2 4 1 television Mehta Hardik Joshi Term NA 0.6 Paper 0.4 11 0.75 0.25
19-08-2014 5 Special Assignment Term Paper Topics
3D Television Pay-Per-View Ambilight Personal Video Recorder Broadcast Flag Pixelplus: Digital Filter Image CableCARD processing technology Digital Light Processing Picture-In-Picture Digital Right Managements Plasma Display Digital Video Recorder Remote Control Direct Broadcast Satellite Surface Conduction Electron Emitter Display DVD and HD-DVD Video On Demand Blue Ray Disc Ultra High Definition TV Flat Panel Display Sling Box High Definition Multimedia Interface Time Shifting IP TV Web TV Laser TV Display Technology Evaluation in Display Technology LCD Display History of television Morror TV Audiography OLED TV Audio Restoration P2P TV 19-08-2014 History of Sound Recording 6 Audio Engineering
Introduction to Television
Dr Usha Mehta Acknowledgement
This presentation has been summarized from various books, papers, websites and presentations on Television Engineering all over the world. I couldn’t remember where these large pull of hints and work come from. However, I’d like to thank all professors and scientists who created such a good work on this emerging field. Without those efforts in this very emerging technology, these notes and slides can’t be finished
19-08-2014 8 What is Television?
Tele: Distance, a Greek prefix Telegraph, telephone, teletex, telescope, telecast, telecommunication…… Vision: to see, Latin word From early days, mankind has a desire to see the things of far away… In Mahabharat, Dhutrashtra…. In real world, motion picture and then came television
19-08-2014 9 What is Television…
It contains….. Images - Black and White Shades of Grey Colour - Hue & Saturation Sound - Audio Information Data - Teletext & Other Data Synchronisation - Specifies the Timing Transport System - Gets all above items to your TV
19-08-2014 10 Let’s build our own TV Transmission- Receiver System
19-08-2014 11 19-08-2014 12 Was it happened in History the same way you think?
19-08-2014 13 History - Ferdinand Braun - CRT 1890 Ferdinand Braun developed the Cathode Ray Tube. 1897 developed the Cathode Ray Oscillograph, the precursor to the radar screen and the television tube 1907 First use of cathode ray tube to produce the rudiments of television images. He shared the Nobel Prize for physics in 1909 with Guglielmo Marconi for his contributions to the development of wireless telegraphy 19-08-2014 14
John Logie Baird - Basic TV
Oct 1923 John Logie Baird was the first person anywhere in the world to demonstrate true television in the form of recognisable images, instantaneous movement and correct gradations in light and shade. Scanning was done mechanically with a Nipkow disc. The first 30 line picture transmitted was a Maltese cross. 1927 he also demonstrated video recording 1928 transatlantic television 1937 the broadcast of high definition colour pictures 1941 stereoscopic television in colour 1944 the multi-gun colour television tube, the forerunner of the type used in most homes today 19-08-2014 15 Early Mechanical Approach to TV
Mechanical Nipkow discs were used to scan the image and reconstitute the image at the receiver. PE cells were used to capture the image. The problem was synchronising the disks
19-08-2014 16 30 Line Mechanical TV
19-08-2014 17 Electronic Television - Farnsworth
In 1922 at Age 14 Philo Farnsworth had the idea of how to make Electronic Television possible. Sept. 7, 1927, Farnsworth painted a square of glass black and scratched a straight line on the centre. The slide was dropped between the Image Dissector (the camera tube that Farnsworth had invented earlier that year) and a hot, bright, carbon arc lamp. On the receiver they saw the straight- line image and then, as the slide was turned 90 degrees, they saw it move. This was the first all-electronic television picture ever transmitted.
19-08-2014 18 Vladimir Zworykin - Iconoscope
In 1923 Vladimir Zworykin of RCA made a patent application for a camera device, and by 1933 had developed a camera tube he called an Iconoscope. Although Zworykin submitted his patent application first after many years of legal battle Farnsworth was acknowledged as the inventor of electronic television. By the end of 1923 he had also produced a picture display tube, the "Kinescope“
19-08-2014 19 Significant Television Inventions
These inventions were the underlying basis of the development of Television as we know it today
19-08 -2014 20 Evolution 1857: Isolation of selenium by Bergelius 1873: Discovery of light sensitive property of Selenium 1884:Nipko’s Disk 1908: All Electronic TV system by A.A. Campbell 1923: Iconoscope by V. Zworykin 1926:TV transmission for members of Royal Institution 1928: Color Transmission 1930: Similar idea by Fransworth After years of patent battles, Fransworth won but RCA (Radio Corporation of America) bought ideas from both 1936: Britain strarted TV Program 1939: USA 1959:India 1982:Color TV in India 19-08-2014 21 Picture Transmission Picture info is optical and broken in “Pixels” Ideally infinite pixels Simultaneous pick-up of info is not possible so scanning With scanning, the problem of “Image Storage” Energy conversion from optical to electrical form by camera using scanning process Photoelectric Effects Photoemission Photo conductivity
19-08-2014 22 Photoemission
Light is in the forms of bundles of energy called photons When these photons of light are bomarded on certain metals, the electrons are dislodged from the surface Caesium Silver, Bismuth, Lithium etc Photons are proportion to intensity of light Iconoscope, Image Orthicone etc use this principal
19-08-2014 23 Photoconductivity
The resistance of semiconductor material is proportional to light incidenting on it. Selenium, Antimony Trisulphide, Lead oxide etc. Vidicon, Plumbicon etc. use this effect
19-08-2014 24 Charge Coupled Device
A charge-coupled device (CCD) is a light- sensitive integrated circuit that stores and displays the data for an image in such a way that each pixel (picture element) in the image is converted into an electical charge, the intensity of which is related to a color in the color spectrum. CCDs are now commonly included in digital still and video cameras.
19-08-2014 25 In the absence of an external electric field the photo generated hole and electron will quickly re-combine and be lost. In a CCD an electric field is introduced to sweep these charge carriers apart and prevent recombination.
19-08-2014 26
19-08-2014 27 Four Primary Functions
Charge Generation Collection & storage Charge transfer Charge measurements
19-08-2014 28 19-08-2014 29 19-08-2014 30 19-08-2014 31 CMOS Sensor/Active Pixel Sensor
photodiode
19-08-2014 32 CCD CMOS High quality Because of large Low noise images number of transistors, some of photons lost More matured devices because of mass and light sensitivity is production low Lower quality, resolution, sensitivity Lower cost and longer battery life
19-08-2014 33 Vidicon Camera Tube
19-08-2014 34 Colour Camera
Partially silvered
19-08-2014 35 Basic Monochrome Television Transmitter
19-08-2014 36 Basic Monochrome Television Receiver
19-08-2014 37 Elements of Picture Tube
19-08-2014 38 Elements of Color Picture Tube
19-08-2014 39 Display Technologies
Cathode Ray Tube (CRT) Vacuum Florescent Display (VFD) Field Emission Display (FED) Flat Panel Display Light Crystal Display (LCD) Plasma Display Panel (PDP) Rear projection/ front projection Digital Light Processing DLPs Organic Light Emitting Diode (OLED)
19-08-2014 40 19-08-2014 41 DLP
19-08-2014 42 How LCD Works
LCD Monitor Technique Animation.mp4
19-08-2014 43 19-08-2014 44 Geometric Form
Frame adopted is rectangle with Aspect Ratio (Width/Height) = 4/3 Reasons: 1.Most of the motion occurs in horizontal plane 2.Eyes can view more easily and comfortably 3.For enabling direct television transmission of film programs without wastage of any film area - Motion pictures use a rectangular frame with width/height ratio of 4/3 – so adopted this aspect ratio in TV
19-08-2014 45 Aspect Ratio
Not the actual size but aspect ratio of the size of the picture produced on the receiver screen and the picture being televised must be the same. achieved by setting the magnitude of the current in the deflection coils to correct values both at the TV camera and the receiving picture tube
19-08-2014 46 Various Aspect Ratio
4:3 => old TV and Computer Monitor 3:2=>classic 35mm movie in silent era 8:5=>credit card 5:3=>European wide screen 1.85:1=>US wide screen 2.39:1=>current wide screen 16:9=>HD video
19-08-2014 47 Aspect Ratio Comparison
19-08-2014 48 Why 16:9?
Dr. Powers cut out rectangles with equal areas, shaped to match each of the popular aspect ratios. When overlapped with their center points aligned, he found that all of those aspect ratio rectangles fit within an outer rectangle with an aspect ratio of 1.77:1 and all of them also covered a smaller common inner rectangle with the same aspect ratio 1.77:1. The value found by Powers is exactly the geometric mean of the extreme aspect ratios, 4:3 (1.33:1) and 2.35:1, which is coincidentally close to 16:9 (1.77:1). Applying the same geometric mean technique to 16:9 and 4:3 yields the 14:9 aspect ratio, which is likewise used as a compromise between these ratios.
19-08-2014 49 Synchronization
Same coordinated should be scanned at any instant both by the camera tube beam and the picture tube beam achieved by transmitting synchronizing pulses along with the picture information
19-08-2014 50 Image Continuity
Persistence of vision : sensation produced when nerves of the eye’s retina are stimulated by incident light does not cease immediately after the light is removed but persists for about 1/16th of a second Scanning rate is made greater than 16 per second i.e. number of pictures shown per second is more than 16 – hence our eye can able to integrate the changing levels of brightness in the scene Present day motion pictures – 24 still pictures of the scene are taken per second and projected on the screen at the same rate
19-08-2014 51
Scanning
19-08-2014 52 Horizontal Scanning
Linear rise of current in the deflection coils deflects the beam across the screen with a continuous uniform motion for the trace from left to right . At the peak of the rise, the saw tooth wave reverses its direction and decreases rapidly to its initial value, producing the retrace or flyback
19-08 -2014 53 Vertical Scanning
19-08-2014 54 . Because of the motion in the scene being televised, the information or brightness at the top of the target plate or picture tube screen normally changes by the time the beam returns to the top to recommence the whole process. This information is picked up during the next scanning cycle and the whole process is repeated 25 times to cause an illusion of continuity . During the horizontal and vertical retrace intervals, the scanning beams at the camera tube and the picture tube are blanked and no picture information is either picked up or reproduced . Synchronizing pulses are transmitted during this period – resulting in distortionless reproduction of the picture details
19-08-2014 55 No. of Scanning Lines . Most scenes have brightness gradations in the vertical directions . The ability of the scanning beam to allow reproduction of electrical signals according to these variations and the capability of the human eye to resolve these distinctly (while viewing) depends on the total number of lines employed for scanning . Number of scanning lines is judged by considering the bar pattern as shown where alternate lines are black and white 19-08-2014 56
No. of Scanning Lines…..
If the thickness of the scanning beam is equal to the width of each black and white bar and the number of scanning lines is chosen equal to the number of bars, then the electrical information corresponding to the brightness of each bar will be correctly produced during the scanning process Greater the number of lines, better will be the resolution
19-08-2014 57 Critical Viewing Distance
The total number of lines is limited by the resolving capability of the human eye at the minimum viewing distance
19-08-2014 58 With reasonable brightness variation and a minimum viewing distance of 4 times the picture height (D/H = 4), the angle that any two adjacent elements must subtend at the eye for distinct resolution is approximately one minute (1/60 degree)
19-08-2014 59 . In practice, the picture elements are not arranged as equally spaced elements but have random distribution of black, grey and white depending on the nature of the picture details. . Analysis and tests suggests that about 70% of the total line get separately scanned in the vertical direction and the remaining 30% get merged with other elements due to the beam spot falling equally on two consecutive lines (as shown in figure)
Thus the effective number of lines distinctly resolved Nr = Nv × K where K is the resolution factor whose value lies between 0.65 & 0.75 Assuming the value of k = 0.7; Nr = 860 × 0.7 = 602 19.-08- 2014 60
Other factors affecting choice of No. of Scanning Lines
. Improvement in resolution is not very significant with line numbers > 500 . Channel bandwidth increases with the increase in number of lines - cost of the system increases - reduces the number of channels in a given VHF/UHF transmission band As a compromise between quality and cost, the total number of lines (inclusive of those lost during vertical retrace) has been chosen to be 625 in the 625-B monochrome TV system. 19-08-2014 61
Flicker
25 frames per second in television picture is not rapid enough to allow the brightness of one picture or frame to blend smoothly into the next during the time when the screen is blanked between successive frames Produces flicker Eliminated in motion pictures by showing each picture twice – ie 48 views of the scene per second – still the same 24 picture frames per second ie each picture frame twice It means more data to transfer with rapid speed means more bandwidth may require……. 19-08-2014 62 Scanning
Progressive Interlaced
19-08-2014 63 Interlaced Scanning
19-08-2014 64 Pixel Aspect Ratio and Scanning
Progressive VS Interlaced Video Modes and Pixel Aspect Ratio.mp4
19-08-2014 65 Resolution
The ability of the image reproducing system to represent the fine structure of an object is known as its resolving power or resolution.
19-08-2014 66 Vertical Resolution The extent to which the scanning system is capable of resolving picture details in the vertical direction is referred to as its vertical resolution. Vr = Na x K Na = No. of effective lines =625-40 (during retrace) =585 K=Kell’s factor, ratio between the number of lines of resolution perceived and the number of pixels or TV scan lines being used (across the same distance) taking into account degradation that might occur in any or all steps of the image reproduction process = 0.69 approx. Vr = 585 X 0.69 = 400lines 19-08-2014 67 Horizontal Resolution
Aiming at equal vertical and horizontal resolution and as such the number of alternate black and white bars that should be considered is equal to Na × aspect ratio = 585 × 4/3 = 780 But effective number of alternate black and white segment = N = Na × aspect ratio × k = 585 × 4/3 × 0.69 = 533
19-08-2014 68 Bandwidth for Monochrome Signal
To resolve the 533 squares or picture elements the scanning spot must develop a video signal of square wave nature switching continuously along the line between voltage levels corresponding to black and peak white.
Since along one line there are 533/2 ≈ 267 complete cyclic changes, 267 complete square wave cycles get generated during the time the beam takes to travel along the width of the pattern. Thus the time duration th of one square wave cycle is equal to
19-08-2014 69 Let’s try…..
The relevant data for a closed circuit TV system is given below. Calculate the highest modulating frequency that will be generated while scanning the most stringent case of alternate black and white dots for equal vertical and horizontal resolution. No. of lines = 250 Interlace ratio = 1 : 1 Picture repetition rate = 50/sec Aspect ratio = 4/3 Vertical retrace time = 10% of the picture frame time Horizontal retrace time = 20% of the total line time Assume resolution factor = 0.8
19-08-2014 70 Influence of number of lines on bandwidth… Effect of interlaced scanning on bandwidth Effect of field frequency on bandwidth Bandwidth requirement of transmitting synchronization pulses…
19-08-2014 71 1080p (aka Full HD/ FHD and BT.709) is a set of HDTV high-definition video modes characterized by 1080 horizontal lines of vertical resolution[1] and progressive scan, as opposed to interlaced, as is the case with the 1080idisplay standard. The term usually assumes a widescreen aspect ratio of 16:9, implying a resolution of 1920x1080 (2.1 megapixel) often marketed as Full HD.
19-08-2014 72 Why odd no. of lines in interlaced scanning?
Interlaced error
19-08-2014 73 Bandwidth for Colour signal
For a very small colour details, the eye can perceive only its brightness, not its hue, so large bandwidth is not required for colour signal Perception of colours by the eye is limited to objects which result in a video frequency output up to about 1.5 MHz.
19-08-2014 74 Brightness and Contrast
19-08-2014 75 Brightness: by adding/subtracting equal dc value to each pixel Contrast: by increasing/decreasing the peak-to-peak amplitude or differences between white and black level
19-08-2014 76 Luminance, Hue and Saturation Luminance/Brightness Amount of light intensity as perceived by the eye regardless of the color Hue/tint Predominant spectral colour of the received light. Different hue has different wavelengths of spectral radiation Saturation The spectral purity of the colour light An indication of how little the color is diluted by white 19-08-2014 77
Hue, Saturation and Luminance
19-08-2014 78 Questions!!!!!
Were you waiting for this slide to come???
19-08-2014 79 Thanks!
19-08-2014 80