An Introduction to Digital Audio - Index

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An Introduction to

Digital AudioSecond Edition

John Watkinson



Focal PressAn imprint of Elsevier ScienceLinacre House, Jordan Hill, Oxford OX2 8DP225 Wildwood Avenue, Woburn, MA 01801-2041

First published 1994Reprinted 1995, 1998, 1999Second Edition 2002

Copyright © 1994, 2002, John Watkinson. All rights reserved

The right of John Watkinson to be identified as the author of this work hasbeen asserted in accordance with the Copyright, Designs and Patents Act 1988

No part of this publication may be reproduced in any material form (includingphotocopying or storing in any medium by electronic means and whether or not transiently or incidentally to some other use of this publication) withoutthe written permission of the copyright holder except in accordance with theprovisions of the Copyright, Designs and Patents Act 1988 or under the terms of a licence issued by the Copyright Licensing Agency Ltd, 90 Tottenham Court Road,London, England W1T 4LP. Applications for the copyright holder’s writtenpermission to reproduce any part of this publication should be addressedto the publisher

British Library Cataloguing in Publication DataA catalogue record for this book is available from the British Library

Library of Congress Cataloguing in Publication Data

Watkinson, John.An introduction to digital audio/John Watkinson – 2nd ed.p.cm.ISBN 0 240 51643 5 (alk. paper)1. Sound – Recording and reproducing – Digital techniques. I. Title.

TK7881.4 W3834 2002621.389'3 – dc21 2002026543

ISBN 0 240 51643 5

For information on all Focal Press publications visit our website at:www.focalpress.com

Composition by Genesis Typesetting, Rochester, KentPrinted and bound in Great Britain by



Contents

Preface to the second edition xi

Chapter 1 Introducing digital audio 1

1.1 Audio as data 11.2 What is an audio signal? 31.3 Why binary? 51.4 Why digital? 91.5 Some digital audio processes outlined 91.6 Time compression and expansion 111.7 Error correction and concealment 14

1.8 Channel coding 181.9 Audio compression 181.10 Disk-based recording 191.11 Rotary-head digital recorders 211.12 Digital audio broadcasting 211.13 Networks 22

Reference 22

Chapter 2 Some audio principles 23

2.1 The physics of sound 23

2.2 Wavelength 242.3 Periodic and aperiodic signals 252.4 Sound and the ear 262.5 The cochlea 282.6 Mental processes 292.7 Level and loudness 312.8 Frequency discrimination 332.9 Frequency response and linearity 362.10 The sine wave 372.11 Root mean square measurements 392.12 The deciBel 41

2.13 Audio level metering 45References 46





Contents vii

5.5 Quality measurement 1655.6 The limits 1665.7 Some guidelines 1675.8 Audio compression tools 168

5.9 Sub-band coding 1725.10 Transform coding 1755.11 Compression formats 1765.12 MPEG Layer I 1775.13 MPEG Layer II 1815.14 MPEG Layer III 183

References 191

Chapter 6 Digital coding principles 193

6.1 Introduction 1936.2 Types of transmission channel 1946.3 Transmission lines 1956.4 Types of recording medium 1976.5 Magnetic recording 1976.6 Azimuth recording and rotary heads 2036.7 Optical and magneto-optical disks 2046.8 Equalization and data separation 2066.9 Slicing and jitter rejection 2086.10 Channel coding 2136.11 Simple codes 215

6.12 Group codes 2186.13 Randomizing and encryption 2206.14 Synchronizing 2216.15 Basic error correction 2226.16 Concealment by interpolation 2256.17 Parity 2256.18 Block and convolutional codes 2286.19 Cyclic codes 2306.20 Introduction to the Reed–Solomon codes 2356.21 Correction by erasure 2436.22 Interleaving 244

6.23 Product codes 245Appendix 6.1 Calculation of Reed–Solomon generator polynomials 247

References 249

Chapter 7 Transmission 250

7.1 Introduction 2507.2 The AES/EBU interface 2507.3 Channel status 2557.4 User bits 259

7.5 MADI – Multi-channel audio digital interface 2597.6 Fibre-optic interfacing 263



viii Contents

7.7 Synchronizing 2637.8 Asynchronous operation 2657.9 Routing and networks 2667.10 Networks 268

7.11 FireWire 2747.12 Broadband networks and ATM 2767.13 Introduction to NICAM 728 2827.14 Audio in digital television broadcasting 2877.15 Packets and time stamps 2897.16 MPEG transport streams 2907.17 Clock references 2917.18 Program Specific Information (PSI) 2927.19 Introduction to DAB 294

References 297

Chapter 8 Digital audio tape recorders 299

8.1 Rotary versus stationary heads 2998.2 PCM adaptors 2998.3 Introduction to DAT 3008.4 DAT specification 3068.5 DAT block diagram 3078.6 Track following in DAT 3098.7 DAT data channel 3118.8 Multi-channel rotary-head recorders 3148.9 Stationary-head recorders 316

8.10 DASH format 3188.11 DCC – Digital Compact Cassette 320References 324

Chapter 9 Magnetic disk drives 325

9.1 Types of disk drive 3259.2 Structure of disk 3279.3 Principle of flying head 3279.4 Reading and writing 3289.5 Moving the heads 331

9.6 Rotation 3339.7 Servo-surface disks 3339.8 Soft sectoring 3339.9 Winchester technology 3349.10 Rotary positioners 3359.11 The disk controller 3379.12 Defect handling 3399.13 Digital audio disk system 3429.14 Arranging the audio data on disk 3439.15 Spooling files 3449.16 Broadcast applications 344

9.17 Sampling rate and playing time 345References 345



Contents ix

Chapter 10 Digital audio editing 347

10.1 Introduction 34710.2 Editing with random access media 34710.3 Editing on recording media 34810.4 The structure of an editor 34910.5 Timecode 35010.6 Locating the edit point 35010.7 Editing with disk drives 35410.8 Editing in DAT 35610.9 Editing in open-reel digital recorders 35710.10 Jump editing 357

References 360

Chapter 11 Optical disks in digital audio 361

11.1 Types of optical disk 36111.2 CD and MD contrasted 36411.3 CD and MD – disk construction 36511.4 Rejecting surface contamination 36611.5 Playing optical disks 36911.6 Focus and tracking systems 37211.7 Typical pickups 37611.8 CD readout in detail 37911.9 How optical disks are made 38311.10 How recordable MiniDiscs are made 38511.11 Channel code of CD and MiniDisc 38611.12 Error-correction strategy 39311.13 Track layout of MD 39711.14 Player structure 398

References 405

Glossary 406

Index 409

Documents

An Introduction to Digital Audio - Index