Table Of Contentillrich 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
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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
