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DIGITAL TERRESTRIAL TELEVISION BROADCASTING

International Telecommunication Union

DTTB HANDBOOK

DIGITAL TERRESTRIAL TELEVISION BROADCASTING IN THE VHF/UHF BANDS

Version 1.02

Radiocommunication Bureau

 ITU 2013

All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU.

OVERALL INTRODUCTION

In view of their many advantages, digital television systems are destined to replace the analogue television systems which have been used for more than half a century to provide sound and vision services to countless millions of people around the world. The ITU-R has decided to provide guidance to engineers responsible for the implementation of digital terrestrial television broadcasting (DTTB) in the form of a single handbook which combines material dealing with both systems and planning aspects of this new, exciting and yet highly complex topic. The result is a rather large volume and anyone interested in the subject of digital television should find something in it which is both informative and useful.

It is not to be expected that all existing analogue television services will be replaced by digital services overnight. Rather, it will take several, perhaps many, years for this to happen. It is hoped that this handbook will continue to provide information and help throughout the interesting years which lie ahead.

PART 1

SYSTEMS PART

PART 1

TABLE OF CONTENTS

Page

CHAPTER  1  –  Introduction

7

1.1 Scope

7

1.2 Background

7

CHAPTER  2  –  An overview of the DTTB model

9

2.1 The challenge

9

2.2 The ITU DTTB model

10

CHAPTER  3  –  Video and audio source coding

13

3.1 Definitions

13

3.1.1 Source and channel coding

13

3.1.2 Source coding

13

3.1.3 Progressive scanning

13

3.1.4 Square pixels

13

3.2 Benefits

13

3.3 Low bit rate video coding and service quality

14

3.4 Examples of video scanning standards

14

3.5 Video compression and coding [1] [2] [3]

14

3.5.1 Introduction

14

3.5.2 Introduction to MPEG

14

3.5.3 Digital compression techniques

15

3.5.4 Inter-frame prediction coding and motion compensation

16

3.5.5 Intra-frame coding

18

3.5.6 Discrete cosine transform (DCT) coding

18

3.5.7 Coefficient quantization

19

3.5.8 Run length coding

21

3.5.9 Variable length coding

21

3.5.10 MPEG video encoder

22

3.5.11 I, B & P-frames

23

3.6 MPEG-2 video bit stream

24

Page

3.7 Audio compression and coding

29

3.7.1 Introduction

29

3.7.2 Characteristics of a DTTB audio system

30

3.7.3 Overview of the DTTB audio system

32

3.7.4 Overview and basics of audio compression

33

3.8 The ISO/IEC IS 13818-3 (MPEG-2) Layer II system

34

3.8.1 Introduction

34

3.8.2 Principal user features of ISO/IEC 13818-3 Layer II

35

3.8.3 MPEG-2 Layer II technical details

43

3.8.4 Conclusion

46

3.9 AC-3 system description

46

3.9.1 Introduction

46

3.9.2 AC-3 technical details

47

3.9.3 Bit stream syntax

50

3.9.4 Loudness and dynamic range

51

3.9.5 Main, associated, and multilingual services

54

3.9.6 Conclusion

58

3.10 Ancillary Data

58

3.10.1 Teletext

59

3.10.2 Programme subtitles

59

3.10.3 Broadcast multimedia ervices

59

3.11 The MPEG-2 multiplexing structure

59

3.11.1 Packetized elementary stream

61

CHAPTER  4  –  Service multiplex and transport

65

4.1 Available structures

65

4.1.1 ATM

65

4.1.2 MPEG-2

65

4.1.3 ISDB

66

4.2 Multiplexing of video, audio, and data

66

4.2.1 Introduction

66

4.2.2 Program versus Transport Stream multiplexing

67

4.2.3 Advantages of the fixed length packetization approach

68

4.2.4 Overview of the transport subsystem

69

Page

4.3 Higher level multiplexing functionality

70

4.3.1 Single program transport multiplex

70

4.3.2 System multiplex

71

4.4 The PES packet format

72

4.5 The packetization approach and functionality

80

4.5.1 Overview

80

4.5.2 The “link” layer

81

4.5.3 The Adaptation layer

84

4.5.4 PSIs and the pointer_field.

88

4.6 Features and services

92

4.6.1 Introduction

92

4.6.2 Audio compression types and language identification

92

4.6.3 Program information

92

4.6.4 Captioning

92

4.6.5 Closed captioning

92

4.6.6 Program source and program identification

93

4.6.7 Conditional access identification

93

4.6.8 Picture structure information

93

4.6.9 Colorimetry

93

4.6.10 Colour field identification

93

4.6.11 Scene changes and clean-insertion points

93

4.6.12 Field/frame rate and film pull-down

94

4.6.13 Pan and scan

94

4.6.14 Random entry into the compressed bit stream

94

4.6.15 Local program insertion

94

4.6.16 Individual programme identification

95

4.6.17 Other channel information

95

CHAPTER  5  –  Physical Layer – Channel coding and modulation

97

5.1 Introduction

97

5.2 Spectral efficiency

97

5.3 Modulation techniques

98

5.3.1 General considerations

98

5.3.2 Single-carrier modulation (SCM)

98

5.3.3 Multi-carrier modulation (MCM)

99

Page

5.4 Channel coding (error correction coding)

105

5.5 Comparisons of early implementations of single- and multi-carrier systems

106

5.5.1 Impulse interference

107

5.5.2 Multipath distortion

107

5.5.3 Co-channel interference from analogue TV

108

5.5.4 Peak and average power ratio issues

109

5.6 Coverage issues

110

5.6.1 Hierarchical transmission

110

5.6.2 Multi-transmitter systems

111

CHAPTER  6  –  Systems overview

113

6.1 The ATSC system

113

6.2 The DVB-T system

113

6.3 The ISDB-T system

115

6.3.1 Transmission bandwidths of ISDB-T

115

6.3.2 Hierarchical transmission

116

6.3.3 Partial reception

116

6.3.4 Multiplex for Hierarchical Transmission

117

6.3.5 Functional Block Diagram of the ISDB-T

118

6.3.6 Transmission parameters

119

CHAPTER  7  –  List of ITU-R Recommendations relating to digital terrestrial television broadcasting (DTTB)

125

PART 2

(See page 127)

CHAPTER 1

INTRODUCTION

1.1 Scope

This part of the Handbook provides tutorial information and an overview on the subject of digital terrestrial television broadcasting (DTTB) systems. It describes a system designed to transmit high quality audio and video services over a single 6, 7, or 8 MHz broadcasting channel and provides a tutorial on the technologies that support the Recommendations developed by the former Task Group 11/3 during the period 1992 through 1996. It also provides a summary of the state of development in systems specifications and plans for service implementation up to the end of 1998.

1.2 Background

The majority of established broadcasters use terrestrially-based emission systems operating in the VHF/UHF frequency bands. The issue of delivery of high-definition television (HDTV) picture signals and associated sound services within a single 6, 7, or 8 MHz VHF/UHF channel resulted in a review of the application of digital coding techniques in terrestrial transmission.

The migration from a television service dependent primarily on the application of analogue technologies to one that is based on digital technologies has been evolving over the past thirty years. This television service migration is part of a natural outgrowth of the convergence of the television, telecommunications, and computer arts and sciences through the shared use of digital technology.

The input and output signals of television systems, at the camera and at the receiver, respectively, are inherently analogue. Thus, the question “why digital?” is a natural one.

While signal degradations in the analogue signal are cumulative and the characteristics of the degradations make them difficult to distinguish from the video signal, the ability to regenerate a digital pulse train exactly renders the digital signals theoretically immune to impairments from external sources. Digital bit streams can be interleaved within a single channel. This interleaving process allows for the emission, transmission, storage, or processing of ancillary signals along with the video and associated audio. Further, compression techniques based on redundancy reduction can be applied to digitized video and audio services allowing the possibility of transmitting one HDTV service or multiple standard services in an exi