6 0 th

ANNIVERSARYYEAR

1930 1990

ResearchDepartment

Report

NICAM 728 DIGITAL TWO-CHANNELSOUND FOR TERRESTRlAL TELEVISION

A.J. Bower, M.A., Ph.D.

Research Department, Engineering DivisionTHE BRITISH BROADCASTING CORPORATION

BBC RD 1990/6

NICAM 728 - DIGITAL TWO-CHANNEL SOUND FORTERRESTRIAL TELEVISION

A.J. Bower, M.A., Ph.D.

Summary

This Report describes the development and technical specification of theNICAM 728 system for broadcasting digital two-channel sound with terrestrial televisiontransmissions. NICAM 728 conveys two high-quality digitally-coded sound signals alongwith the picture and monophonic FM sound signals of the existing System I and SystemsB, G and H terrestrial television transmission standards.

The NICAM 728 system was developed initially by the BBC, and jinalised inconsultation with the IBA and BREMA. Tests have proved that the system is compatiblewith existing transmission standards; and that the digital sound signals are rugged and willbe reliably received wherever the colour picture is satisfactory.

In September 1986, the joint BBC/IBA/BREMA technical specification wasapproved by the United Kingdom Government for use in the UK with the System Itelevision transmission standard. The system has been successfully adapted, with theminimum of modifications, for operation with television Systems B, G and H, which areused in much of Europe and elsewhere in the world As a result, NICAM 728 hasattracted considerable international interest, and the system now forms the basis of atechnical specification and recommendation from the European Broadcasting Union (EBU)with the CCIR having drafted a similar Recommendation.

Index terms: TV signals; digital audio signals; stereophony; multichannel systems;companding; companding; bit rate reduction; PSK; modulation

Issued under the Authority of

Research Department, Engineering DivisionBRITISH BROADCASTING CORPORATION Head of Research Department

(EL-203) 1990

British Broadcasting Corporation

No part of this publication may be reproduced, stored in aretrieval system, or transmitted in any form or by anymeans, electronic, mechanical, photocopying, recording,or otherwise, without prior permission.

1.

2.

3. Tests of the System in the UK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

4. International Interest and Tests.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

5. NICAM 728 Equipment..................................................... 25

6. Conclusions and Future Developments.. . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

7. Acknowledgements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

8. References................................................................ 26

NICAM 728 DIGITAL TWO-CHANNEL SOUNDFOR TERRESTRIAL TELEVISION

A.J. Bower, M.A., Ph.D.

l n t r o d u c t i o n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.1 NICAM 728 - an overview of the system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.2 Background history - design objectives. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Specification of the NICAM 728 system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2.1 General description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2.2 Baseband coding specification. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52.2.1 Main features of the baseband coding specification . . . . . . . . . . . . . . . . . . . . . . 52.2.2 Anaiogue-to-digital conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62.2.3 Near instantaneous companding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2.2.3.1 14-10 Ni companding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72.2.3.2 Error protection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92.2.3.3 Signaliing-in-Parity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102.2.3.4 The ‘Ci’bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

2.2.4 Multiplexing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112.2.4.1 NICAM 728 frame structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112.2.4.2 Control information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122.2.4.3 Additional data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142.2.4.4 Sound/data block . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142.2.4.5 Bit-interleaving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142.2.4.6 Energy dispersal scrambling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I4

2.3 Specification of the modulation parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152.3.1 Frequency and level of the digitally-modulated carrier . . . . . . . . . . . . . . . . . . . . 152.3.2 Specification of the digitally-modulated carrier . . . . . . . . . . . . . . . . . . . . . . . . . . 172.3.3 Performance under impaired reception conditions - low field strength . . . . . . 212.3.4 Performance under impaired reception conditions - multipath reception . . . . 22

Published by

BBC Research & Development

Kingswood Warren

Tadworth

Surrey

KT20 6NP

England

http://www.bbc.co.uk/rd