IEC 61937-3:2017

IEC 61937-3 ®
Edition 3.0 2017-07
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Digital audio – Interface for non-linear PCM encoded audio bitstreams applying
IEC 60958 –
Part 3: Non-linear PCM bitstreams according to the AC-3 and enhanced
AC-3 formats
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
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About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
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latest edition, a corrigenda or an amendment might have been published.

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IEC 61937-3 ®
Edition 3.0 2017-07
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Digital audio – Interface for non-linear PCM encoded audio bitstreams applying

IEC 60958 –
Part 3: Non-linear PCM bitstreams according to the AC-3 and enhanced

AC-3 formats
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 33.160.30 ISBN 978-2-8322-4677-1

– 2 – IEC 61937-3:2017 RLV © IEC 2017
CONTENTS
FOREWORD . 3
1 Scope . 5
2 Normative references . 5
3 Terms, definitions and abbreviated terms . 5
3.7 Abbreviated terms . 6
4 Mapping of the audio bitstream on to IEC 61937-1 . 6
4.1 General . 6
4.2 AC-3 and enhanced AC-3 burst-info . 6
5 Format of AC-3 and enhanced AC-3 data-bursts . 7
5.1 General . 7
5.2 Pause data-burst . 7
5.3 Audio data-bursts . 8
5.3.1 AC-3 data . 8
5.3.2 Latency of AC-3 decoding . 9
5.3.3 Enhanced AC-3 data . 10
5.3.4 Latency of the enhanced AC-3 decoder . 12
Bibliography . 14

Figure 1 – AC-3 data-burst, with reference point R. 8
Figure 2 – Latency of AC-3 decoding . 9
Figure 3 – Enhanced AC-3 data-burst . 11
Figure 4 – Latency of enhanced AC-3 decoding . 12

Table 1 – Fields of burst-info . 7
Table 2 – Repetition period of the pause data-bursts . 7
Table 3 – Data-type-dependent information when data-type bits 0-4= 1 . 8
Table 4 – Data-type-dependent information when data-type bits 0-4 = 21 and data-
type bits 5-6 = 0 . 11
Table 5 – Frame repetition period and maximum data rate for enhanced AC-3
bitstreams .
Table 5 – Maximum enhanced AC-3 burst-payload size and bitstream data rate per
sampling frequency and IEC 60958 frame rate . 12

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
DIGITAL AUDIO –
INTERFACE FOR NON-LINEAR PCM ENCODED AUDIO BITSTREAMS
APPLYING IEC 60958 –
Part 3: Non-linear PCM bitstreams according to the AC-3 and
enhanced AC-3 formats
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
This redline version of the official IEC Standard allows the user to identify the changes
made to the previous edition. A vertical bar appears in the margin wherever a change
has been made. Additions are in green text, deletions are in strikethrough red text.

– 4 – IEC 61937-3:2017 RLV © IEC 2017
International Standard IEC 61937-3 has been prepared by subcommittee technical area 4:
Digital system interfaces and protocols, of IEC technical committee 100: Audio, video and
multimedia systems and equipment.
This third edition of IEC 61937-3 cancels and replaces the second edition published in 2007.
This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) removal of support for enhanced AC-3 bitstreams with a sampling frequency of 32 kHz;
b) updates to normative and informative references;
c) clarification of pause data-burst usage for enhanced AC-3 bitstreams.
The text of this International Standard is based on the following documents:
CDV Report on voting
100/2720/CDV 100/2934/RVC
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts in the IEC 61973 series, published under the general title Digital audio –
Interface for non-linear PCM encoded audio bitstreams applying IEC 60958, can be found on
the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.

IMPORTANT – The “colour inside” logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct understanding
of its contents. Users should therefore print this publication using a colour printer.

DIGITAL AUDIO –
INTERFACE FOR NON-LINEAR PCM ENCODED AUDIO BITSTREAMS
APPLYING IEC 60958 –
Part 3: Non-linear PCM bitstreams according to the AC-3 and
enhanced AC-3 formats
1 Scope
This part of IEC 61937 describes the method used to convey non-linear PCM bitstreams
encoded according to the AC-3 and enhanced AC-3 formats.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their
content constitutes requirements of this document. For dated references, only the edition
cited applies. For undated references, the latest edition of the referenced document (including
any amendments) applies.
IEC 60958 (all parts), Digital audio interface
IEC 61937-1:2007, Digital audio interface for non-linear PCM encoded audio bit streams
applying IEC 60958 – Part 1: General
IEC 61937-1:2007/AMD1:2011, Digital audio interface for non-linear PCM encoded audio bit
streams applying IEC 60958 – Part 1: General
IEC 61937-2:2007, Digital audio interface for non-linear PCM encoded audio bit streams
applying IEC 60958 – Part 2: Burst-info
ATSC Standard A/52B, Digital Audio Compression (AC-3, E-AC-3), Rev. B
ETSI TS 102 366, Digital Audio Compression (AC-3, Enhanced AC-3) Standard
3 Terms, definitions and abbreviated terms
For the purposes of this document, the following terms and definitions and abbreviations
apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
...

IEC 61937-3 ®
Edition 3.1 2020-09
CONSOLIDATED VERSION
INTERNATIONAL
STANDARD
colour
inside
Digital audio – Interface for non-linear PCM encoded audio bitstreams applying
IEC 60958 –
Part 3: Non-linear PCM bitstreams according to the AC-3 and enhanced
AC-3 formats
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or
your local IEC member National Committee for further information.

IEC Central Office Tel.: +41 22 919 02 11
3, rue de Varembé info@iec.ch
CH-1211 Geneva 20 www.iec.ch
Switzerland
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigendum or an amendment might have been published.

IEC publications search - webstore.iec.ch/advsearchform Electropedia - www.electropedia.org
The advanced search enables to find IEC publications by a The world's leading online dictionary on electrotechnology,
variety of criteria (reference number, text, technical containing more than 22 000 terminological entries in English
committee,…). It also gives information on projects, replaced and French, with equivalent terms in 16 additional languages.
and withdrawn publications. Also known as the International Electrotechnical Vocabulary

(IEV) online.
IEC Just Published - webstore.iec.ch/justpublished
Stay up to date on all new IEC publications. Just Published IEC Glossary - std.iec.ch/glossary
details all new publications released. Available online and 67 000 electrotechnical terminology entries in English and
once a month by email. French extracted from the Terms and definitions clause of
IEC publications issued between 2002 and 2015. Some
IEC Customer Service Centre - webstore.iec.ch/csc entries have been collected from earlier publications of IEC
If you wish to give us your feedback on this publication or TC 37, 77, 86 and CISPR.

need further assistance, please contact the Customer Service

Centre: sales@iec.ch.
IEC 61937-3 ®
Edition 3.1 2020-09
CONSOLIDATED VERSION
INTERNATIONAL
STANDARD
colour
inside
Digital audio – Interface for non-linear PCM encoded audio bitstreams applying

IEC 60958 –
Part 3: Non-linear PCM bitstreams according to the AC-3 and enhanced

AC-3 formats
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 33.160.30 ISBN 978-2-8322-8910-5

IEC 61937-3 ®
Edition 3.1 2020-09
CONSOLIDATED VERSION
REDLINE VERSION
colour
inside
Digital audio – Interface for non-linear PCM encoded audio bitstreams applying
IEC 60958 –
Part 3: Non-linear PCM bitstreams according to the AC-3 and enhanced
AC-3 formats
– 2 – IEC 61937-3:2017+AMD1:2020 CSV
© IEC 2020
CONTENTS
FOREWORD . 3
1 Scope . 6
2 Normative references . 6
3 Terms, definitions and abbreviated terms . 6
3.7 Abbreviated terms . 7
4 Mapping of the audio bitstream on to IEC 61937-1 . 7
4.1 General . 7
4.2 AC-3 and enhanced AC-3 burst-info . 7
5 Format of AC-3 and enhanced AC-3 data-bursts . 8
5.1 General . 8
5.2 Pause data-burst . 8
5.3 Audio data-bursts . 8
5.3.1 AC-3 data . 8
5.3.2 Latency of AC-3 decoding . 9
5.3.3 Enhanced AC-3 data . 10
5.3.4 Latency of the enhanced AC-3 decoder . 12
Bibliography . 14

Figure 1 – AC-3 data-burst, with reference point R. 8
Figure 2 – Latency of AC-3 decoding . 9
Figure 3 – Enhanced AC-3 data-burst . 11
Figure 4 – Latency of enhanced AC-3 decoding . 12

Table 1 – Fields of burst-info . 7
Table 2 – Repetition period of the pause data-bursts . 8
Table 3 – Data-type-dependent information when data-type bits 0-4 = 1 . 9
Table 4 – Data-type-dependent information when data-type bits 0-4 = 21 and data-
type bits 5-6 = 0 . 11
Table 5 – Maximum enhanced AC-3 burst-payload size and bitstream data rate per
sampling frequency and IEC 60958 frame rate . 12

© IEC 2020
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
DIGITAL AUDIO –
INTERFACE FOR NON-LINEAR PCM ENCODED AUDIO BITSTREAMS
APPLYING IEC 60958 –
Part 3: Non-linear PCM bitstreams according to the AC-3 and
enhanced AC-3 formats
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
This consolidated version of the official IEC Standard and its amendment has been
prepared for user convenience.
IEC 61937-3 edition 3.1 contains the third edition (2017-07) [documents 100/2720/CDV
and 100/2934/RVC] and its amendment 1 (2020-09) [documents 100/3392/CDV and
100/3456/RVC].
In this Redline version, a vertical line in the margin shows where the technical content
is modified by amendment 1. Additions are in green text, deletions are in strikethrough
red text. A separate Final version with all changes accepted is available in this
publication.
– 4 – IEC 61937-3:2017+AMD1:2020 CSV
© IEC 2020
International Standard IEC 61937-3 has been prepared by subcommittee technical area 4:
Digital system interfaces and protocols, of IEC technical committee 100: Audio, video and
multimedia systems and equipment.
This third edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) removal of support for enhanced AC-3 bitstreams with a sampling frequency of 32 kHz;
b) updates to normative and informative references;
c) clarification of pause data-burst usage for enhanced AC-3 bitstreams.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts in the IEC 61973 series, published under the general title Digital audio –
Interface for non-linear PCM encoded audio bitstreams applying IEC 60958, can be found on
the IEC website.
The committee has decided that the contents of the base publication and its amendment will
remain unchanged until the stability date indicated on the IEC web site under
"http://webstore.iec.ch" in the data related to the specific publication. At this date, the
publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
© IEC 2020
INTRODUCTION to Amendment 1
This amendment to 61937-3:2017 is necessary to remove the last paragraph from the
Enhanced AC-3 provisions that does not apply to Enhanced AC-3. It only applies to AC-3 and
was inadvertantly copied when Enhanced AC-3 was authored.

– 6 – IEC 61937-3:2017+AMD1:2020 CSV
© IEC 2020
DIGITAL AUDIO –
INTERFACE FOR NON-LINEAR PCM ENCODED AUDIO BITSTREAMS
APPLYING IEC 60958 –
Part 3: Non-linear PCM bitstreams according to the AC-3 and
enhanced AC-3 formats
1 Scope
This part of IEC 61937 describes the method used to convey non-linear PCM bitstreams
encoded according to the AC-3 and enhanced AC-3 formats.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their
content constitutes requirements of this document. For dated references, only the edition
cited applies. For undated references, the latest edition of the referenced document (including
any amendments) applies.
IEC 61937-1:2007, Digital audio interface for non-linear PCM encoded audio bit streams
applying IEC 60958 – Part 1: General
IEC 61937-1:2007/AMD1:2011, Digital audio interface for non-linear PCM encoded audio bit
streams applying IEC 60958 – Part 1: General
IEC 61937-2, Digital audio interface for non-linear PCM encoded audio bit streams applying
IEC 60958 – Part 2: Burst-info
ETSI TS 102 366, Digital Audio Compression (AC-3, Enhanced AC-3) Standard
3 Terms, definitions and abbreviated terms
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses
...