Modern Television Systems to HDTV and beyond Jim Slater I. Eng., AMIERE PITMAN PUBLISHING 128 Long Acre, London WC2E 9AN A Division of Longman Group UK Limited © J.N.Slater 1991 First published in Great Britain 1991 This edition published in the Taylor & Francis e-Library, 2004. British Library Cataloguing in Publication Data Slater, Jim Modern television systems. I. Title 621.388 ISBN 0-203-16851-8 Master e-book ISBN ISBN 0-203-26370-7 (Adobe eReader Format) ISBN 0-273-03122-8 (Print Edition) All rights reserved. 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 and/or otherwise without either the prior written permission of the Publishers or a licence permitting restricted copying in the United Kingdom issued by the Copyright Licensing Agency Ltd. 90 Tottenham Court Rd., London W1P 0BR. 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Contents 1 Principles of television systems, and a little history 1 2 The search for a compatible colour system 15 Colour vision and colour television—the basic principles 16 Colour-difference components 18 Compatibility considerations 19 Constant luminance problems 20 Composite colour systems 22 3 NTSC—the world’s first practical colour television system 23 Baseband spectrum 23 Radio frequency spectrum 25 Cross-colour and cross-luminance 27 Subcarrier modulation 27 Chrominance signal amplitude restrictions 28 Chrominance signal bandwidths 29 The complete video signal 32 Disadvantages of the NTSC system 32 4 The development of PAL and SECAM 35 SECAM—Sequentiel Couleur À Mémoire 35 The basics of the SECAM system 35 Colour synchronisation methods 37 Differential weighting 39 Disadvantages of SECAM 39 Fading and mixing SECAM signals 40 SECAM developments 41 PAL—an alternative engineering solution to the problems of NTSC 42 Basics of the PAL system 43 Vector representation of PAL signals 44 Simple PAL receivers 45 Delay-line PAL receivers 47 iii Compatibility and the choice of subcarrier frequency 49 Frequency spectrum characteristics 50 Disadvantages of the PAL system 52 5 MAC—the first of a new generation of television systems 56 Introduction 56 The MAC (multiplexed analogue components) system 61 A time-compressed analogue waveform 70 Bandwidth considerations 71 Wide-screen pictures 71 The complete MAC signal—adding the data burst 75 MAC variants, but a common vision signal 76 A-MAC 77 B-MAC 78 C-MAC 80 The D-MAC/packet system 82 Packet organisation 89 The data capacity of the D-MAC and D-2 MAC/packet systems 95 Sound coding options with MAC 96 MAC—a good basis for future systems 98 MAC for studio centres—S-MAC 98 Sending MAC signals along contribution and distribution links 100 An alternative MAC system for ENG links—T-MAC 102 Conditional access: a built-in scrambling system 102 MAC in practice—the chip sets 105 Progress with MAC 106 6 Recommendation 601—one world standard; digital video and the world digital studio standard 108 Digital television 108 The advantages of digital television 111 The need for a digital standard 113 Composite digital video 113 Component digital video 115 Quantisation levels 119 Rounding errors 119 The 4:2:2 shorthand 121 The transmission of digital signals 123 Bit-rate reduction 123 iv Standards 124 Composite digital reappears 125 7 The long road towards a better system—higher definition on the horizon 127 Is there a need for better-quality television? 127 High-definition television—what do we mean? 130 The beginnings of HDTV 137 Terminology 141 8 Japan’s Hi-Vision—the world’s first HDTV system 145 Introduction 145 The basic parameters of the Japanese HDTV system 146 The HDTV studio production standard 151 Sampling and subsampling principles as applied to television 152 The MUSE system 154 9 Compatible approaches to HDTV 161 The options 161 EUREKA—the European approach to HDTV 164 Transmitting compatible HDTV signals 173 Characteristics of the working HD-MAC transmission system 175 Enhanced television—the half-way house? 181 10 American approaches to HDTV 188 Introduction 188 ‘Taboo’ channels 189 The spectrum usage options for ATV 191 Standardisation in America 192 Advanced compatible television (ACTV) 195 ACTV-I—NTSC-compatible EDTV 196 ACTV-II—full HDTV in a compatible manner 202 Entry-level ACTV 207 Progress with ACTV 208 SuperNTSC—Faroudja Laboratories 209 The Zenith Spectrum Compatible HDTV system 213 HD-NTSC—the Del Rey Group HDTV system 221 MITV-CC and MITV-RC—two ‘channel-compatible’ systems from the Massachusetts Institute of Technology 225 The VISTA system, from Dr William Glen of the New York Institute of Technology 230 v The North American Philips proposals—HDNTSC and HDMAC-60 234 The Bell Laboratories proposal—the SLSC (Split Luminance/Split Chrominance) system 237 HDB-MAC—the Scientific Atlanta HDTV proposal 238 The High Resolution Sciences CCF system 240 QuanTV—a new technique from the Quanticon company 242 The Osborne Compression System 244 The Fukinuki approach to improved NTSC 246 The QUME system—Quadrature Modulation of the Picture Carrier 247 CBS proposal 249 GENESYS—a remarkable proposal from Production Services Inc. 251 The Avelex system 252 The Broadcasting Technology Association proposal 253 The noise margin method of hiding enhancement information 253 Liberty Television/Weaver proposal 255 The DigiCipher HDTV system 255 MUSE for the USA—a Japanese hierarchy of systems 259 The US ATV proposals—thoughts and conclusions 267 DBS for the USA—at last? The Sky Cable project 273 11 Progress towards a world standard—the 1990s 276 Common image format 278 The common data rate 279 Open architecture receivers 281 Virtual studio standard 284 12 HDTV with no standards required—a glimpse into the future 286 Spectrum utilisation 286 Spectrum conservation 288 Digital storage—the frame store 288 HDTV—already passé? 289 HDTV—just another computer program? 289 Telecommunications and HDTV 290 The ultimate goal—HDTV without standards 293 Appendix: Digital television—developments in transmission 295 Index 301 vi Preface Television viewers are understandably reluctant to face the expense of replacing their receiving equipment at frequent intervals. This simple fact puts considerable constraints on research and development engineers who would ideally like to introduce new and improved television systems from time to time, which they know could provide better pictures and sound as well as a whole range of new facilities. It is thus a fact of life that television transmission systems must, by their very nature, exist for a long period of time if they are to be commercially viable. There is nothing new about this, and the three currently used colour television standards of the world, NTSC, SECAM, and PAL, have been in use for over a quarter of a century and look set to continue in use for almost as long again before they are finally discontinued. As an example of this, the transmitting authorities in the United Kingdom are currently replacing their existing PAL transmitters with new ones which, it is anticipated, will have lifetimes of at least twenty years, and broadcasters throughout the world are continuing to expand their transmitter networks using the existing standards. It is no surprise then that television transmission standards have stayed fairly static over the last couple of decades, and many of the excellent books that were written at the time when the existing systems were just being introduced have now become classics, and are regarded as the ‘bibles’ of the television art, even by engineers who are new to the business. Quite simply, since the systems have stayed static, the need for new books on television transmission systems has not really arisen. This rather dull scenario is, however, about to undergo meteoric changes, since the coming of satellite broadcasting has brought the key which is opening up new opportunities for higher-quality television systems and the eventual dissemination of High Definition Television signals throughout the world. Over the past few years development laboratories have been humming with ideas for new and better ways of transmitting television signals, and topics such as digital television, multiplexed component transmission systems, and the dozens of ideas for enhanced definition television pictures and sound that are now being put forward have led to the need for this book, which attempts to give a comprehensive overview of this fast-moving and exciting field. vii Aimed primarily at the television engineer who wishes to gain an up-to- date understanding of the basic tenets of the new television transmission systems, the book provides a sound appreciation of the various topics whilst avoiding unnecessarily detailed mathematical considerations. The author hopes that it will also prove of interest to students, to non-technical professionals in the communications industry, and to the intelligent layman who wishes to broaden understanding of these novel techniques which will eventually affect us all. viii Principles of television systems, and a little 1 history ‘If men could learn from history, what lessons it might each us!’ This cry from the heart of Samuel Taylor Coleridge in 1831 will still be echoed by the world’s television engineers two hundred years later if they refuse to learn from mistakes of the past. ‘What mistakes?’, you might ask, ‘don’t we have excellent television pictures, bright, sharp, and in colour; aren’t our transmitters reliable and our receivers trouble-free and inexpensive?’ All those things are true, but just try taking your portable television receiver the twenty miles across the English Channel to France, or from the USA across either the Pacific or the Atlantic, and you will begin to get just an inkling of the problems that really face television.