illrich Reimers Digital Video Broadcasting (DVB) Springer-Verlag Berlin Heidelberg GmbH Ulrich Reimers Digital Video Broadcasting (DVB) The International Standard for Digital Television With 175 figures i Springer Prof.Dr.-Ing. Ulrich Reimers Dr.-Ing. Frank Fechter Dipl.-Ing. Dirk Jaeger Dipl.-Ing. Christian Johansen Dipl.-Ing. Uwe Ladebusch Dipl.-Ing. ChristofRicken Dipl.-Ing. Alexander Roy Dipl.-Ing. Markus Trauberg Dipl.-Ing. Andreas Verse Technische Universitat Braunschweig Institut fUr Nachrichtentechnik (Braunschweig Technical University Institute for Communications Technology) Schleinitzstrasse 22 38092 Braunschweig E-mail: [email protected] Library of Congress Cataloging-in-Publication Data Digitale Fernsehtechnik, English Digital video broadcasting (DVB) ; the international standard for digital television I [edited by] Ulrich Reimers. p.cm. Includes bibliographical references and index. 1. Digital television--Standards. 2. MPEG (Video coding standard). 3. Television broadcasting. I. Reimers, Ulrich. II. Title. ISBN 978-3-662-04564-0 ISBN 978-3-662-04562-6 (eBook) DOI 10.1007/978-3-662-04562-6 This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfllm or in other ways, and storage in data banks. Duplication of this publication or parts thereof is permitted only under the provisions of the German Copyright Law of September 9, 1965, in its current version, and permission for use must always be obtained from Springer-Verlag. Violations are liable for prosecution act under German Copyright Law. © Springer-Verlag Berlin Heidelberg 2001 Originally published by Springer-Verlag Berlin Heidelberg New York in 2001 Softcover reprint of the hardcover 18t edition 2001 The use of general descriptive names, registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. Typesetting: Data Conversion by typetwo, Berlin Cover-Design: Struve & Partner, Heidelberg SPIN: 10525858 Printed on acid-free paper 68/3020 - 5 4 3 2 1 0 - Preface Digital Television ("Digital TeleVision Broadcasting" [DTVB] or "Digital Video Broadcasting" [DVBJ) has become one of the most exciting develop ments in the area of consumer electronics at the end of the twentieth century. The term digital television is not typically used either to describe the digitisa tion of the production studio or to indicate the advent of digital signal proc essing in the integrated circuits used in television receivers. Rather, digital television refers to the source coding of audio, data and video signals, the channel coding and the methods for the transport ofDVB signals via all kinds of transmission media. The term normally also embraces the technologies used for the return path from the consumer back to the programme provider, techniques for scrambling and conditional access, the concepts of data broad casting, the software platforms used in the terminal devices, as well as the user interfaces providing easy access to DVB services. The aim of this book is to describe the technologies of digital television. The description refers to a point in time at which much of the technical devel opment work had taken place. No doubt, in the future there will inevitably be a considerable number of modifications and additions to the list of technical documents describing the technologies used for DVB. The performance data of the DVB systems, specifically of the one used for terrestrial transmission, are still in the process of being evaluated in many countries throughout the world. In some respects this book must therefore be regarded as a report on the present intermediate stage of the development of digital television and of the practical experience gained so far. I nevertheless consider it timely to present such a report, since at the date of its publication DVB will have be come a market reality in many countries. The focus is on the developments within, and the achievements of, the "Moving Pictures Experts Group (MPEG)" in the area of source coding of audio and video signals, followed by an extended description of the work and the results of the "DVB Project", the international body dealing with the design of all the other technical solutions required for the successful operation of digital television. The combination of the specifications de signed by MPEG and those designed by the DVB Project has led to the overall system that we can now call digital television. The system for the vi Preface terrestrial transmission of MPEG signals presented by the "Advanced Tele vision Systems Committee (ATSC)" will not be described in detail in this book. This system will be used in the United States of America, in Canada, Mexico and some other parts of the world. It uses vestigial side-band mo dulation (VSB) of a single carrier per channel, and sound coding called Dolby AC-3. VSB will be explained in the chapter dealing with modulation techniques. The book addresses readers who wish to gain an in-depth understanding of the techniques used for digital television. They should already have a good knowledge of the existing analogue television systems and should know the properties of analogue audio and video signals. They should also have some understanding of the techniques used in digital signal origination and digital signal processing. Chapter 1 is an introduction to the DVB world. It presents an overview of the whole DVB scenario and answers the very fundamental questions con cerning the goals of the development of digital television. It describes the state of technical developments and tries to evaluate several scenarios for the introduction of services using the different transmission media. Chapter 2 recapitulates the fundamentals of the digitisation of audio and video signals. It explains the parameters chosen for the digitisation, such as the quantisation scales and the sampling frequencies, and derives the result ing data rates. On the basis of the figures presented in chapter 2 the funda mentals of source coding of audio and video signals are described in chapters 3 and 4, respectively. The primary goal of source coding is to reduce the data rate for the representation of audio and video signals in such a way that no de terioration of the perceptual quality results or, at most, only a well-defined one. In this way the resources required for the transmission and/or storage of the signals can be limited. Before the data-reduced signals can actually be transmitted they have to be amalgamated into a system multiplex. Tools for the synchronisation of audio and video, auxiliary data needed for the description of the multiplex and of the programme content conveyed by that multiplex, teletext data, and a great deal of other information need to be added. Chapter 5 explains the multiplex ing and the structure of the auxiliary data. One of the special features of digital signals is that they can be protected against the effects of unavoidable errors occurring during transmission by adding forward error correction before the signals are sent. Chapter 6 de scribes methods of forward error correction (FEC) in general. It then concen trates on the two methods used in the DVB world, namely, Reed-Solomon coding and convolutional coding. Digital modulation is dealt with in chapter 7. Here again we highlight those methods which are used in DVB (QPSK, QAM, OFDM, VSB). Preface vii The techniques used for the scrambling of digital signals are presented in chapter 8. Owing to the very nature of this topic it is impossible to describe in detail the specific methods which are used for DVB. The three standards for the transmission of DVB signals via satellite, on ca ble and via terrestrial networks are described in chapters 9,10 and 11, respec tively. In addition to merely explaining the specific details of the standards, we give the performance data and further information regarding the hard ware implementation in the receivers. Finally, the methods of measuring and evaluating DVB signals as well as audio and video quality are explained in chapter 12. This book is the result of the joint effort of several researchers working at the Institute for Communications Technology (Institut fur Nachrichtentech nik - IfN) at Braunschweig Technical University (Technische UniversiHit Braunschweig) in Germany. The contents are based upon a series of seminars held for interested European industrial professionals since the beginning of 1994. To date, over 250 participants have attended such seminars, in which we not only present the theoretical background of the DVB systems but demon strate the possibilities of DVB and the existing DVB systems and services. In nearly all cases the authors report about areas in which they themselves have carried out research work. Amongst other things, this work has already gen erated four doctoral theses. Several of the researchers are - or have been - members of either ad-hoc groups of the DVB Project or of the Moving Pic tures Experts Group (MPEG). I wish to thank the authors for their competency and co-operation in meet ing deadlines for the various manuscripts. Ms. Boguslawa Brandt and Ms. Si mone Sengpiel prepared a large number of the drawings used in this book and Dipl.-Ing. Christian Johansen was responsible for the final co-ordinating and editing of the whole text. I extend my thanks to all three of them. The first German edition of this book was published in 1995. It was followed by a revised second edition in 1997. The English version is based upon that sec ond German edition. Of course, several amendments portraying develop ments between 1997 and 1998 have been included. The translation from Ger man into English was done by Ms. Vivienne Bruns and Ms. Anne Kampendonk. I am most grateful to both ladies for having taken on this very difficult job. Dr. George Waters, the former Director of Engineering of the European Broadcasting Union (EBU), undertook the final proofreading of the English version. I am especially indebted to him for his invaluable contribution to the quality of the book. Springer publishers, and in particular Dipl.-Ing. Thomas Lehnert, were competent and active partners in producing the book. My thanks go to them for their guidance and assistance during the publication process of the Eng lish version. viii Preface Digital television, based on the specifications developed by the DVB Pro ject, would most certainly have remained a dream without the co-operation of countless researchers and engineers in Europe, North America and Asia who were highly enthusiastic about the creation of the digital television para digm. I have the pleasure of being chairman of the Technical Module of the DVB Project and I wish to join the other authors of this book in thanking all the DVB colleagues and friends for such a great achievement. Braunschweig, December 1998 Prof. Dr.-Ing. Ulrich Reimers Table of Contents 1 Digital Television - a First Summary (REIMERS) . 1 1.1 Definitions and Range of Application. . . . . 1 1.2 The Genesis of Recommendations for Digital Television 4 1.2.1 Work in the United States of America. 5 1.2.2 Work in Europe. . . 6 1.2·3 Work in Japan, Canada and Korea 9 1.3 Objectives in the Development of Digital Television 9 1.4 Data Reduction as the Key to Success. 11 1.5 Possible Means of Transmission for Digital Television 13 1.6 Standards and Norms in the World of Digital Television 16 2 Digitisation and Representation of Audio and Video Signals (JOHANSEN) 19 2.1 Sampling and Quantising . 19 2.2 Digitising Video Signals 20 2.2.1 ADCs and DACs for Video Signals 22 2.2.2 Representation of Video Signals 24 2·3 Digitising Audio Signals 27 2·3·1 Representation of Audio Signals 28 2·3·2 ADCs and DACs for Audio Signals . 28 3 MPEG Source Coding of Audio Signals (FECHTER) . 35 3·1 Basics of Bit-rate Reduction .. 35 3·2 Psychoacoustic Basics 37 3·2.1 Threshold of Audibility and Auditory Sensation Area. 37 3·2.2 Masking 38 Source Coding of Audio Signals Utilising the Masking 3·3 Qualities of the Human Ear. 42 3·3-1 Basic Structure of the MPEG Coding Technique 43 3·3·2 Coding in Accordance with Layer 1 . 47 3-3·3 Coding in Accordance with Layer 2 . 49 3·3·4 Coding in Accordance with Layer 3 . 50 3·3·5 Decoding. 52 x Table of Contents 3·3·6 The Parameters of MPEG Audio 52 3·3·7 MPEG-2 Audio Coding . 53 3·4 Summary ........... . 54 4 JPEG and MPEG Source Coding of Video Signals (RICKEN). 57 4·1 Coding in Accordance with JPEG. . . . 58 4·1.1 Block Diagram of Encoder and Decoder 58 4·1.2 Discrete Cosine Transform . 59 4·1.3 Quantisation . . . . . . 61 4·1.4 Redundancy Reduction. 63 4·1.5 Specific Modes . . . . . 65 4·1.6 Interchange Format . . 68 4·2 Coding in Accordance with the MPEG Standards . 69 4·2.1 Block Diagrams of Encoder and Decoder. 71 4.2.2 Motion Estimation . . 73 4·2·3 Reordering of Pictures . . . 76 4·2·4 Data-rate Control. ..... 77 4·2·5 Special Features of MPEG-1. 78 4·2.6 Special Features of MPEG-2. 81 4·3 Summary ......... . 87 5 MPEG-2 Systems and Multiplexing (RICKEN) . 5·1 Differences between Programme Multiplex and Transport Multiplex ..................... . 89 5·2 Positioning of Systems in the ISOIOSI Layer Model. 90 5·3 End-to-end Synchronisation 92 5·4 Service Information . . . . . . . . . . . . . . . . 97 6 Forward Error Correction (FEC) in Digital Television Transmission (RoY) 99 6.1 Basic Observations. . . . . . . . . . . . . . . . 99 6.2 Reed-Solomon Codes .............. . 102 6.2.1 Introduction to the Arithmetic of the Galois Field 103 6.2.2 Definition of the RS Code and the Encoding/Decoding in the Frequency Domain. . . . . . . . . . . . . . . . 109 6.2·3 Error Correction Using the RS Code . . . . . . . . . . 110 6.2-4 Examples of Encoding/Decoding in the Frequency Domain. 113 6.2·5 Encoding and Decoding in the Time Domain. 115 6.2.6 Efficiency of the RS Code. . . . . 116 6.3 Convolutional Codes . . . . . . . . . . . . . 117 6·3·1 Basics of the Convolutional Codes . . . . . . 117 6.3.2 Examples of Convolutional Encoding and Decoding 119