IEC 61937-4:2003

INTERNATIONAL IEC
STANDARD
61937-4
First edition
2003-05
Digital audio –
Interface for non-linear PCM encoded
audio bitstreams applying IEC 60958 –
Part 4:
Non-linear PCM bitstreams
according to the MPEG audio format
Reference number
Publication numbering
As from 1 January 1997 all IEC publications are issued with a designation in the
60000 series. For example, IEC 34-1 is now referred to as IEC 60034-1.
Consolidated editions
The IEC is now publishing consolidated versions of its publications. For example,
edition numbers 1.0, 1.1 and 1.2 refer, respectively, to the base publication, the
base publication incorporating amendment 1 and the base publication incorporating
amendments 1 and 2.
Further information on IEC publications
The technical content of IEC publications is kept under constant review by the IEC,
thus ensuring that the content reflects current technology. Information relating to
this publication, including its validity, is available in the IEC Catalogue of
publications (see below) in addition to new editions, amendments and corrigenda.
Information on the subjects under consideration and work in progress undertaken
by the technical committee which has prepared this publication, as well as the list
of publications issued, is also available from the following:
• IEC Web Site (www.iec.ch)
• Catalogue of IEC publications
The on-line catalogue on the IEC web site (http://www.iec.ch/searchpub/cur_fut.htm)
enables you to search by a variety of criteria including text searches, technical
committees and date of publication. On-line information is also available on
recently issued publications, withdrawn and replaced publications, as well as
corrigenda.
• IEC Just Published
This summary of recently issued publications (http://www.iec.ch/online_news/
justpub/jp_entry.htm) is also available by email. Please contact the Customer
Service Centre (see below) for further information.
• Customer Service Centre
If you have any questions regarding this publication or need further assistance,
please contact the Customer Service Centre:
Email: custserv@iec.ch
Tel: +41 22 919 02 11
Fax: +41 22 919 03 00
INTERNATIONAL IEC
STANDARD
61937-4
First edition
2003-05
Digital audio –
Interface for non-linear PCM encoded
audio bitstreams applying IEC 60958 –
Part 4:
Non-linear PCM bitstreams
according to the MPEG audio format
 IEC 2003  Copyright - all rights reserved
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 the publisher.
International Electrotechnical Commission, 3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, Switzerland
Telephone: +41 22 919 02 11 Telefax: +41 22 919 03 00 E-mail: inmail@iec.ch  Web: www.iec.ch
PRICE CODE
Commission Electrotechnique Internationale
M
International Electrotechnical Commission
Международная Электротехническая Комиссия
For price, see current catalogue

– 2 – 61937-4  IEC:2003(E)
CONTENTS
FOREWORD . 3
1 Scope . 5
2 Normative references. 5
3 Terms and definitions . 5
3.1 Definitions . 5
3.2 Abbreviations. 5
3.3 Presentation convention . 6
4 Mapping of the audio bitstream on to IEC 61937. 6
5 Format of MPEG audio data-burst. 6
5.1 General . 6
5.2 Pause data-burst . 6
5.3 Audio data-types. 7
5.3.1 MPEG-1 layer-1 . 7
5.3.2 MPEG-1 layer-2 or -3, or MPEG-2 without extension. 7
5.3.3 MPEG-2 with extension. 8
5.3.4 MPEG-2 layer-1 low sampling frequency.10
5.3.5 MPEG-2 layer-2 Low sampling frequency.11
5.3.6 MPEG-2 layer-3 low sampling frequency.11
Bibliography.13
Figure 1 – MPEG-1 layer-1 data-burst. 7
Figure 2 – Data-burst with MPEG-1 layer 2 or 3 or MPEG-2 without extension . 8
Figure 3 – Latency of MPEG-1 layer 2 or 3 or MPEG-2 without extension . 8
Figure 4 – Format of MPEG-base-frame and MPEG-extension-frame . 9
Figure 5 – MPEG 2 with extension data-burst. 9
Figure 6 – Latency of MPEG-2 with extension .10
Figure 7 – MPEG-2 layer-1 low sampling frequency data-burst.10
Figure 8 – MPEG-2 layer-2 low sampling frequency data-burst.11
Figure 9 – MPEG-2 layer-3 low sampling frequency data-burst.12
Table 1 – Fields of burst-info.6
Table 2 – Repetition period of pause data-bursts . 7
Table 3 – Data-type-dependent info for data-types 5 and 6 . 9

61937-4  IEC:2003(E) – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
DIGITAL AUDIO –
INTERFACE FOR NON-LINEAR PCM ENCODED
AUDIO BITSTREAMS APPLYING IEC 60958 –

Part 4: Non-linear PCM bitstreams
according to the MPEG audio formats

FOREWORD
1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of the 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, the IEC publishes International Standards. 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. The 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 the 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 National Committees.
3) The documents produced have the form of recommendations for international use and are published in the form
of standards, technical specifications, technical reports or guides and they are accepted by the National
Committees in that sense.
4) In order to promote international unification, IEC National Committees undertake to apply IEC International
Standards transparently to the maximum extent possible in their national and regional standards. Any
divergence between the IEC Standard and the corresponding national or regional standard shall be clearly
indicated in the latter.
5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with one of its standards.
6) Attention is drawn to the possibility that some of the elements of this International Standard may be the subject
of patent rights. The IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61937-4 has been prepared by technical area 4: Digital system
interfaces, of IEC technical committee 100: Audio, video and multimedia systems and
equipment.
This standard cancels and replaces IEC 61937, published in 2000, which has been divided
into four parts (see below). This first edition constitutes a technical revision.
The text of this standard is based on the following documents:
FDIS Report on voting
100/647/FDIS 100/673/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

– 4 – 61937-4  IEC:2003(E)
IEC 61937 consists of the following parts under the general title Digital audio – Interface for
non-linear PCM encoded audio bitstreams applying IEC 60958:
Part 1: General
Part 2: Burst-info
Part 3: Non-linear PCM bistreams according to the AC-3 format
Part 4: Non-linear PCM bitstreams according to the MPEG audio formats
Part 5: Non-linear PCM bitstreams according to the DTS (Digital Theatre Systems) format(s)
Part 6: Non-linear PCM bitstreams according to the MPEG-2 AAC format
Part 7: Non-linear PCM bitstreams according to the ATRAC and ATRAC2/3 formats
The committee has decided that the contents of this publication will remain unchanged until
October 2005. At this date, the publication will be
• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.
The contents of the corrigendum of March 2004 have been included in this copy.

61937-4  IEC:2003(E) – 5 –
DIGITAL AUDIO –
INTERFACE FOR NON-LINEAR PCM ENCODED
AUDIO BITSTREAMS APPLYING IEC 60958 –
Part 4: Non-linear PCM bitstreams
according to the MPEG audio formats
1 Scope
This part of IEC 61937 specifies the method for the digital audio interface specified in
IEC 60958 to convey non-linear PCM bitstreams encoded in accordance with the MPEG
audio.
2 Normative references
The following referenced documents are indispensable for the application 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, Digital audio – Interface for non-linear PCM encoded audio bitstreams applying
IEC 60958 – Part 1: General
3 Terms and definitions
For the purposes of this document, the following definitions, abbreviations and presentation
convention apply.
3.1 Definitions
3.1.1
latency
delay time of an external audio decoder to decode an AC-3 data-burst, defined as the sum of
two values of the receiving delay time and the decoding delay time
3.2 Abbreviations
3.2.1
ATSC
Advanced Television Systems Committee
3.2.2
MPEG
Moving Pictures Expert Group, a joint committee of ISO and IEC
3.2.3
ITU-R
International Telecommunication Union, Radio Communication Bureau

– 6 – 61937-4  IEC:2003(E)
3.3 Presentation convention
F872h
Value ‘F872’ in hexadecimal format
4 Mapping of the audio bitstream on to IEC 61937
The coding of the bitstream and data-burst is in accordance with IEC 61937-1.
The 16-bit burst-info contains information about the data that will be found in the data-burst
(see Table 1).
Table 1 – Fields of burst-info
Repetition period of
Reference
Bits of Pc Value Contents data-burst in
point R
IEC 60958 frames
0 – 4 Data-type
0 – 3 According to IEC 61937
4 MPEG-1 layer-1 data Bit 0 of Pa 384
5 MPEG-1 layer-2 or -3 data, or MPEG-2 Bit 0 of Pa 1 152
without extension
6 MPEG-2 data with extension Bit 0 of Pa 1 152
7 MPEG-2 AAC Bit 0 of Pa 1 024
8 MPEG-2 layer-1 low sampling frequency Bit 0 of Pa 768
9 MPEG-2 layer-2 low sampling frequency Bit 0 of Pa 2 304
10 MPEG-2 layer-3 low sampling frequency Bit 0 of Pa 1 152
10 – 31 According to IEC 61937
5 – 15 According to IEC 61937
5 Format of MPEG audio data-burst
5.1 General
This clause specifies the audio data-burst of MPEG audio. Specific properties such as
reference points, repetition period, method of filling stream gaps and decoding latency are
specified.
The decoding latency (or delay), indicated for the data-types, should be used by the
transmitter to schedule data-bursts as necessary to establish synchronization between picture
and decoded audio.
5.2 Pause data-burst
Pause data-bursts for MPEG audio are given in Table 2.

61937-4  IEC:2003(E) – 7 –
Table 2 – Repetition period of pause data-bursts
Repetition period of pause data-burst
Data-type of audio data-burst
Mandatory Recommended
MPEG-1 layer-1 data 32 IEC 60958 frames
MPEG-1 layer-2 or -3 data, or MPEG-2 without extension 32 IEC 60958 frames
MPEG-2 data with extension 32 IEC 60958 frames
MPEG-2 layer-1 low sampling frequency 64 IEC 60958 frames
MPEG-2 layer-2 low sampling frequency 64 IEC 60958 frames
MPEG-2 layer-3 low sampling frequency 64 IEC 60958 frames
5.3 Audio data-types
5.3.1 MPEG-1 layer-1
An MPEG-1 layer-1 MPEG-frame represents 384 samples of each encoded channel and can
be transferred using data-type 04h. The data-burst is headed with a burst-preamble, followed
by the burst-payload.
Pa Pb Pc Pd MPEG-1 layer-1 burst_payload Pa Pb Pc Pd
Bit 0 of Pa Bit 0 of Pa
MPEG-1 layer-1 frame Stuffing
Repetition period of the burst
IEC  1300/03
Figure 1 – MPEG-1 Layer-1 data-burst
In the case where pause data-bursts are used to fill stream gaps in the MPEG-1 layer-1 bit-
stream as described in IEC 61937-1, it is recommended tha
...