EN 61937-6:2006

Digital audio - Interface for non-linear PCM encoded audio bitstreams applying IEC 60958 - Part 6: Non-linear PCM bitstreams according to the MPEG-2 AAC and MPEG-4 AAC formats

specifies the method for IEC 60958 to convey non-linear PCM bitstreams encoded in accordance with the MPEG-2 AAC (Advanced Audio Coding) and MPEG-4 AAC formats.

Digitalton - Schnittstelle für nichtlinear-PCM-codierte Audio-Bitströme unter Verwendung von IEC 60958 - Teil 6: Nichtlineare PCM-Bitströme nach MPEG-2 AAC- und MPEG-4 AAC-Formaten

Audionumérique - Interface pour les flux de bits audio à codage MIC non linéaire, conformément à la CEI 60958 - Partie 6: Flux de bits MIC non linéaire selon les formats MPEG-2 AAC et MPEG-4 AAC

La CEI 61937-6:2006 spécifie la méthode de la CEI 60958 pour acheminer des flux de bits MIC non linéaire codés selon les formats MPEG-2 AAC (codage du son avancé) et MPEG-4 AAC. Cette deuxième édition de la CEI 61937-6 annule et remplace la première édition parue en 2002. Elle contient les modifications techniques importantes suivantes: - ajout du type de données au format MPEG-2 AAC à faible fréquence d'échantillonnage; - ajout du type de données au format MPEG-4 AAC.

Digitalni avdio - Vmesnik za nelinearne bitne struje, kodirane s PCM z uporabo standarda IEC 60958 - 6. del: Nelinearne PCM-bitne struje po zvokovnih formatih MPEG-2 AAC in MPEG-4 AAC (IEC 61937-6:2006)

Ta del standarda IEC 61937 določa metodo za standard IEC 60958 za prenos nelinearnih PCM-bitnih tokov v skladu s formatoma MPEG-2 AAC (Advanced Audio Coding) in MPEG-4 AAC.

General Information

• Status: Published
• Publication Date: 13-Jul-2006
• ICS: 33.160.60 - Multimedia systems and teleconferencing equipment
• ICS: 35.040 - Information coding
• ICS: 35.040.40 - Coding of audio, video, multimedia and hypermedia information
• Technical Committee: CLC/TC 100X - Audio, video and multimedia systems and equipment and related sub-systems
• Drafting Committee: IEC/TC 100 - IEC_TC_100
• Parallel Committee: IEC/TC 100 - IEC_TC_100
• Current Stage: 6060 - Document made available - Publishing
• Start Date: 14-Jul-2006
• Completion Date: 14-Jul-2006
• Ref Project: SIST EN 61937-6:2007 - Digital audio - Interface for non-linear PCM encoded audio bitstreams applying IEC 60958 -- Part 6: Non-linear PCM bitstreams according to the MPEG-2 AAC and MPEG-4 AAC audio formats

Relations

• Revised: EN 61937-6:2002 - Digital Audio - Interface for non-linear PCM encoded audio bitstreams applying IEC 60958 - Part 6: Non-linear PCM bitstreams according to the MPEG-2 AAC format
• Effective Date: 13-May-2010
• Replaces: EN 61937-6:2002 - Digital Audio - Interface for non-linear PCM encoded audio bitstreams applying IEC 60958 - Part 6: Non-linear PCM bitstreams according to the MPEG-2 AAC format
• Effective Date: 07-Jun-2022

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN 61937-6:2007
01-januar-2007
1DGRPHãþD
SIST EN 61937-6:2003
Digitalni avdio - Vmesnik za nelinearne bitne struje, kodirane s PCM z uporabo
standarda IEC 60958 - 6. del: Nelinearne PCM-bitne struje po zvokovnih formatih
MPEG-2 AAC in MPEG-4 AAC (IEC 61937-6:2006)
Digital audio - Interface for non-linear PCM encoded audio bitstreams applying IEC
60958 -- Part 6: Non-linear PCM bitstreams according to the MPEG-2 AAC and MPEG-4
AAC audio formats
Digitalton - Schnittstelle für nichtlinear-PCM-codierte Audio-Bitströme unter Verwendung
von IEC 60958 -- Teil 6: Nichtlineare PCM-Bitströme nach MPEG-2 AAC- und MPEG-4
AAC-Audio-Formaten
Audionumérique - Interface pour les flux de bits audio à codage MIC non linéaire,
conformément à la CEI 60958 -- Partie 6: Flux de bits MIC non linéaire selon les formats
MPEG-2 AAC et MPEG-4 AAC
Ta slovenski standard je istoveten z: EN 61937-6:2006
ICS:
33.160.30 Avdio sistemi Audio systems
35.200 Vmesniška in povezovalna Interface and interconnection
oprema equipment
SIST EN 61937-6:2007 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 61937-6:2007

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SIST EN 61937-6:2007


EUROPEAN STANDARD
EN 61937-6

NORME EUROPÉENNE
July 2006
EUROPÄISCHE NORM

ICS 33.160.60, 35.040 Supersedes EN 61937-6:2002


English version


Digital audio –
Interface for non-linear PCM encoded audio bitstreams
applying IEC 60958
Part 6: Non-linear PCM bitstreams according to the MPEG-2 AAC
and MPEG-4 AAC audio formats
(IEC 61937-6:2006)


Audionumérique –  Digitalton –
Interface pour les flux de bits audio Schnittstelle für nichtlinear-PCM-codierte
à codage MIC non linéaire, Audio-Bitströme unter Verwendung
conformément à la CEI 60958 von IEC 60958
Partie 6: Flux de bits MIC non linéaire Teil 6: Nichtlineare PCM-Bitströme
selon les formats MPEG-2 AAC nach MPEG-2 AAC- und MPEG-4 AAC-
et MPEG-4 AAC Audio-Formaten
(CEI 61937-6:2006) (IEC 61937-6:2006)


This European Standard was approved by CENELEC on 2006-07-01. CENELEC members are bound to
comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration.

Up-to-date lists and bibliographical references concerning such national standards may be obtained on
application to the Central Secretariat or to any CENELEC member.

This European Standard exists in two official versions (English and German). A version in any other language
made by translation under the responsibility of a CENELEC member into its own language and notified to the
Central Secretariat has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Cyprus, the Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia,
Spain, Sweden, Switzerland and the United Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Central Secretariat: rue de Stassart 35, B - 1050 Brussels


© 2006 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
-
Ref. No. EN 61937-6:2006 E

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SIST EN 61937-6:2007
EN 61937-6:2006 - 2 -
Foreword
The text of the International Standard IEC 61937-6:2006, prepared by IEC TC 100, Audio, video and
multimedia systems and equipment, was submitted to the formal vote and was approved by CENELEC as
EN 61937-6 on 2006-07-01 without any modification.
This European Standard supersedes EN 61937-6:2002.
It includes the following significant technical changes with respect to EN 61937-6:2002:
a) addition of data-type for MPEG2 AAC low sampling frequency;
b) additon of data-type for MPEG-4 AAC.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2007-07-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2009-07-01
Annex ZA has been added by CENELEC.
__________
Endorsement notice
The text of the International Standard IEC 61937-6:2006 was approved by CENELEC as a European
Standard without any modification.
__________

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SIST EN 61937-6:2007
- 3 - EN 61937-6:2006
Annex ZA
(normative)

Normative references to international publications
with their corresponding European publications

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.

NOTE  When an international publication has been modified by common modifications, indicated by (mod), the relevant EN/HD
applies.


Publication Year Title EN/HD Year

IEC 60958 Series Digital audio interface EN 60958 Series


IEC 61937 Series Digital audio - Interface for non-linear PCM EN 61937 Series
encoded audio bitstreams applying
IEC 60958


1) 2)
IEC 61937-1 Digital audio - Interface for non-linear PCM EN 61937-1
- 2003
encoded audio bitstreams applying
IEC 60958
Part 1: General


1) 2)
IEC 61937-2 - Digital audio - Interface for non-linear PCM EN 61937-2 2003
encoded audio bitstreams applying
IEC 60958
Part 2: Burst-info


ISO/IEC 13818-7 2004 Information technology - Generic coding of - -
moving pictures and associated audio
information
Part 7: Advanced Audio Coding (AAC)


ISO/IEC 14496-3 2001 Information technology - Coding of audio- - -
+ A1 2003 visual objects
Part 3: Audio




1)
Undated reference.
2)
Valid edition at date of issue.

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SIST EN 61937-6:2007

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SIST EN 61937-6:2007


INTERNATIONAL IEC


STANDARD 61937-6





Second edition
2006-01


Digital audio – Interface for non-linear PCM
encoded audio bitstreams applying IEC 60958 –
Part 6:
Non-linear PCM bitstreams according
to the MPEG-2 AAC and MPEG-4 AAC
audio formats

 IEC 2006  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: [phone] Telefax: [phone] E-mail: [e-mail] Web: www.iec.ch
PRICE CODE
Commission Electrotechnique Internationale S
International Electrotechnical Commission
МеждународнаяЭлектротехническаяКомиссия
For price, see current catalogue

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SIST EN 61937-6:2007
– 2 – 61937-6  IEC:2006(E)
CONTENTS
FOREWORD.4

1 Scope.6
2 Normative references .6
3 Terms, definitions, abbreviations and presentation convention .6
3.1 Terms and definitions .6
3.2 Abbreviations .7
3.3 Presentation convention .7
4 Mapping of the audio bitstream on to IEC 61937 .7
4.1 MPEG-2 AAC burst-info.7
4.2 MPEG-4 AAC burst-info.8
5 Format of MPEG-2 AAC and MPEG-4 AAC data-bursts .8
5.1 Pause data-burst.9
5.2 Audio data-bursts .9


Figure 1 – MPEG-2 AAC data-burst .9
Figure 2 – Latency of MPEG-2 AAC decoding.10
Figure 3 – MPEG-2 AAC half-rate low sampling frequency data-burst .11
Figure 4 – Latency of MPEG-2 AAC half-rate low sampling frequency decoding.12
Figure 5 – MPEG-2 AAC quarter-rate low sampling frequency data-burst.13
Figure 6 – Latency of MPEG-2 AAC quarter-rate low sampling frequency decoding .14
Figure 7 – MPEG-4 AAC data-burst .15
Figure 7 – Latency of MPEG-4 AAC decoding.16
Figure 8 – MPEG-4 AAC half-rate low sampling frequency data-burst .16
Figure 9 – Latency of MPEG-4 AAC half-rate low sampling frequency decoding.17
Figure 10 – MPEG-4 AAC quarter-rate low sampling frequency data-burst.18
Figure 11 – Latency of MPEG-4 AAC quarter-rate low sampling frequency decoding .19
Figure 12 – MPEG-4 AAC double-rate high sampling frequency data-burst .20
Figure 13 – Latency of MPEG-4 AAC double-rate high sampling frequency decoding.21

Table 1 – Fields of burst-info (data-type=7) .7
Table 2 – Fields of burst-info (data-type=19).8
Table 3 – Fields of burst-info (data-type=20).8
Table 4 – Repetition period of pause data-bursts .9
Table 5 – Repetition period of pause data-bursts .9
Table 6 – Data-type-dependent information for data-type MPEG-2 AAC.10
Table 7 – Data-type-dependent information for data-type MPEG-2 AAC
half-rate low sampling frequency.11
Table 8 – Data-type-dependent information for data-type MPEG-2 AAC
quarter-rate low sampling frequency .13

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SIST EN 61937-6:2007
61937-6  IEC:2006(E) – 3 –
Table 9 – Data-type-dependent information for data-type MPEG-4 AAC.15
Table 10 – Data-type-dependent information for data-type MPEG-4 AAC
half-rate low sampling frequency.17
Table 11 – Data-type-dependent information for data-type MPEG-4 AAC
quarter-rate low sampling frequency .18
Table 12 – Data-type-dependent information for data-type MPEG-4 AAC
double-rate high sampling frequency .20

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SIST EN 61937-6:2007
– 4 – 61937-6  IEC:2006(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________

DIGITAL AUDIO –
INTERFACE FOR NON-LINEAR PCM ENCODED
AUDIO BITSTREAMS APPLYING IEC 60958 –

Part 6: Non-linear PCM bitstreams according to
the MPEG-2 AAC and MPEG-4 AAC 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 provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
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.
International Standard IEC 61937-6 has been prepared by technical area 4: Digital systems
interfaces, of IEC technical committee 100: Audio, video and multimedia systems and
equipment.
This second edition of IEC 61937-6 cancels and replaces the first edition published in 2002.
This edition contains the following significant technical changes with respect to the previous
edition:
a) addition of data-type for MPEG2 AAC low sampling frequency;
b) addition of data-type for MPEG-4 AAC.

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SIST EN 61937-6:2007
61937-6  IEC:2006(E) – 5 –
The text of this standard is based on the following documents:
CDV Report on voting
100/942/CDV 100/1043A/RVC

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.
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 bitstreams 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 Theater Systems)
format(s)
Part 6: Non-linear PCM bitstreams according to the MPEG-2 AAC and MPEG-4 AAC
formats
Part 7: Non-linear PCM bitstreams according to the ATRAC, ATRAC2/3 and ATRAC-X
formats

The committee has decided that the contents of this publication will remain unchanged until
the maintenance result 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.

A bilingual version of this document may be issued at a later date.

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SIST EN 61937-6:2007
– 6 – 61937-6  IEC:2006(E)
DIGITAL AUDIO –
INTERFACE FOR NON-LINEAR PCM ENCODED
AUDIO BITSTREAMS APPLYING IEC 60958 –

Part 6: Non-linear PCM bitstreams according to
the MPEG-2 AAC and MPEG-4 AAC formats



1 Scope
This part of IEC 61937 specifies the method for IEC 60958 to convey non-linear PCM
bitstreams encoded in accordance with the MPEG-2 AAC (Advanced Audio Coding) and
MPEG-4 AAC formats.
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 (all parts), Digital audio – Interface for non-linear PCM encoded audio bitstreams
applying IEC 60958
IEC 61937-1, Digital audio – Interface for non-linear PCM encoded audio bitstreams applying
IEC 60958 – Part 1: General
IEC 61937-2, Digital audio – Interface for non-linear PCM encoded audio bitstreams applying
IEC 60958 – Part 2: Burst-info
ISO/IEC 13818-7:2004, Information technology – Generic coding of moving pictures and
associated audio information – Part 7: Advanced Audio Coding (AAC)
ISO/IEC 14496-3:2001, Information technology – Coding of audio-visual objects – Part 3:
Audio
Amendment 1 (2003)
3 Terms, definitions, abbreviations and presentation convention
For the purposes of this document, the following terms, definitions, abbreviations and
presentation convention apply.
3.1 Terms and definitions
3.1.1
subdata-type
reference to the type of payload of the data-burst defined for use with the specified data-type
3.1.2
LC profile
low complexity profile identified in ISO/IEC 13818-7

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SIST EN 61937-6:2007
61937-6  IEC:2006(E) – 7 –
3.1.3
LC profile with SBR
low complexity profile with spectral band replication identified in ISO/IEC 13818-7
3.1.4
latency
delay time of an external audio decoder to decode a MPEG-2 AAC or MPEG-4 AAC data-burst
defined as the sum of two values of the receiving delay time and the decoding delay time
3.1.5
AAC profile
AAC profile identified in ISO/IEC 14496-3
3.1.6
HE-AAC profile
HE-AAC profile identified in ISO/IEC 14496-3
3.2 Abbreviations
AAC Advanced Audio Coding
ADTS Audio Data Transport Stream
SBR Spectral Band Replication
HE-AAC  High Efficiency AAC
3.3 Presentation convention
01 Value “01” in binary format
2

4 Mapping of the audio bitstream on to IEC 61937
The coding of the bitstream and data-burst is in accordance with IEC 61937.
4.1 MPEG-2 AAC burst-info
MPEG-2 AAC burst-info (data-type=7) is given in Table 1.
Table 1 – Fields of burst-info (data-type=7)
Bits of Pc Value Contents Reference Repetition period
point R of data-burst in
IEC 60958 frames
0-4 Data-type
7 MPEG-2 AAC ADTS Bit 0 of Pa 1 024
5,6 00 Reserved
2
7-15 In accordance with IEC 61937-1 and
IEC 61937-2

MPEG-2 AAC burst-info (data-type=19) is given in Table 2.

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SIST EN 61937-6:2007
– 8 – 61937-6  IEC:2006(E)
Table 2 – Fields of burst-info (data-type=19)
Bits of Pc Value Contents Reference Repetition period
point R of data-burst in
IEC 60958 frames
0-4 Data-type
19 MPEG-2 AAC ADTS low sampling Depends on
frequency  subdata-type

5,6 Subdata-type

00 Subdata-type for MPEG-2 AAC ADTS half- Bit 0 of Pa 2 048
2
rate low sampling frequency
01 Subdata-type for MPEG-2 AAC ADTS Bit 0 of Pa 4 096
2
quarter-rate low sampling frequency
10 11 Reserved
2, 2
7-15 In accordance with IEC 61937-1 and
IEC 61937-2

4.2 MPEG-4 AAC burst-info
MPEG-4 AAC burst-info (data-type=20) is given in Table 3.
Table 3 – Fields of burst-info (data-type=20)
Bits of Pc Value Contents Reference Repetition period
point R of data-burst in
IEC 60958 frames
0-4 Data-type
20 MPEG-4 AAC  Depends on
subdata-type
5,6 Subdata-type
00 Subdata-type for MPEG4 AAC Bit 0 of Pa 1024
2
01 Subdata-type for MPEG4 AAC half-rate Bit 0 of Pa 2 048
2
low sampling frequency

102 Subdata-type for MPEG4 AAC quarter-rate Bit 0 of Pa 4 096
low sampling frequency
11 Subdata-type for MPEG4 AAC double-rate Bit 0 of Pa 512
2
high sampling frequency
7-15 In accordance with IEC 61937-1 and
IEC 61937-2

5 Format of MPEG-2 AAC and MPEG-4 AAC data-bursts
This clause specifies the audio data-bursts MPEG-2 AAC and MPEG-4 AAC. Specific
properties such as reference points, repetition period, the method of filling stream gaps, and
decoding latency are specified for each data-type.
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 the
picture and the decoded audio.

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SIST EN 61937-6:2007
61937-6  IEC:2006(E) – 9 –
5.1 Pause data-burst
5.1.1 The data MPEG-2 AAC
The pause data-burst for MPEG-2 AAC is given in Table 4.
Table 4 – Repetition period of pause data-bursts
Data-type of audio data-burst Repetition period of pause data-burst
Mandatory Recommended
MPEG-2 AAC - 32 IEC 60958 frames
MPEG-2 AAC and half-rate low sampling frequency - 64 IEC 60958 frames
MPEG-2 AAC and quarter-rate low sampling frequency - 128 IEC 60958 frames

5.1.2 The data MPEG-4 AAC
The pause data-burst for MPEG-4 AAC is given in Table 5.
Table 5 – Repetition period of pause data-bursts
Data-type of audio data-burst Repetition period of pause data-burst
Mandatory Recommended
MPEG-4 AAC - 32 IEC 60958 frames
MPEG-4 AAC and half-rate low sampling frequency - 64 IEC 60958 frames
MPEG-4 AAC and quarter-rate low sampling frequency - 128 IEC 60958 frames
MPEG-4 AAC double-rate high sampling frequency - 16 IEC 60958 frames

5.2 Audio data-bursts
5.2.1 The data MPEG-2 AAC
The stream of the data-bursts for MPEG-2 AAC consists of sequences of MPEG-2 AAC ADTS
frames. The data-type of an MPEG-2 AAC data-burst is 7. The data-burst is headed with a
burst-preamble, followed by the burst-payload, and stuffed with stuffing bits. The burst-
payload of each data-burst of MPEG-2 AAC data shall contain one complete MPEG-2 AAC
ADTS frame and represents 1 024 samples for each encoded channel. The length of the
MPEG-2 AAC data-burst depends on the encoded bit rate (which determines the MPEG-
2 AAC ADTS frame length). The reference to the specification for the MPEG-2 AAC bitstream,
representing 1 024 samples of encoded audio per frame is found in ISO/IEC 13818-7.

MPEG-2 AAC MPEG-2 AAC
Pa Pb Pc Pd Pa Pb Pc Pd
burst_payload burst_payload
Bit 0 of Pa Bit 0 of Pa
AAC frame Stuffing AAC frame
Regular rate of the MPEG-2 AAC frames
Repetition period of the burst

Figure 1 – MPEG-2 AAC data-burst
The data-type-dependent information for MPEG-2 AAC is given in Table 6.

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SIST EN 61937-6:2007
– 10 – 61937-6  IEC:2006(E)
Table 6 – Data-type-dependent information for data-type MPEG-2 AAC
Bits of Pc Value Contents

LSB.MSB
8-12 00 No indication
01 LC profile
02, 03 Reserved for future profile
04-31 Reserved

The reference point of an MPEG-2 AAC data-burst is bit 0 of Pa and occurs exactly once
every 1 024 sampling periods. The data-burst containing MPEG-2 AAC frames shall occur at a
regular rate, with the reference point of each MPEG-2 AAC data-burst beginning 1 024
IEC 60958 frames after the reference point of the preceding MPEG-2 AAC data-burst (of the
same bitstream number).
It is recommended that pause data-bursts are used to fill stream gaps in the MPEG-2 AAC bit-
stream as described in IEC 61937, and that pause data-bursts be transmitted with a repetition
period of 32 IEC 60958 frames, except when other repetition periods are necessary to fill the
precise stream-gap length (which may not be a multiple of 32 IEC 60958 frames), or to meet
the requirement on burst spacing (see IEC 61937).
When a stream gap in an MPEG-2 AAC stream is filled by a sequence of pause data-bursts,
the Pa of the first pause data-burst shall be located 1 024 sampling periods following the Pa
of the previous MPEG-2 AAC frame. It is recommended that the sequence(s) of pause data-
bursts which fill the stream gap should continue from this point up to (as close as possible to,
considering the 32 IEC 60958 frame length of the pause data-burst) the Pa of the first MPEG-
2 AAC data-burst which follows the stream gap. The gap-length parameter contained in the
pause data-burst is intended to be interpreted by the MPEG-2 AAC decoder as an indication
of the number of decoded PCM samples which are missing (due to the resulting audio gap).
5.2.2 Latency of MPEG-2 AAC decoding
The latency of an external audio decoder to decode MPEG-2 AAC is defined as the sum of the
receiving delay time and the decoding delay time.

MPEG-2 AAC  MPEG-2 AAC
Pa Pb Pc Pd Pa Pb Pc Pd
burst-payload burst-payload
Bit 0 of Pa
Bit 0 of Pa
MPEG-2 AAC frame Stuffing
MPEG-2 AAC frame
Repetition period of the burst
Receiving delay Decoding delay
Latency of MPEG-2 AAC decoder

Figure 2 – Latency of MPEG-2 AAC decoding
EXAMPLE The receiving delay time to receive a whole data-burst with maximum length is
calculated as follows. The length of preamble is 64 bits. The maximum length of whole data-
burst payload is 8 192 bit in the Japanese satellite DTV specified maximum bit rate of
384 kbit/s. In this case, the maximum length of data-bursts is 8 256 bit. The receiving delay
time is calculated as 5,375 ms in the case of the 48 kHz sampling frequency. The decoding

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SIST EN 61937-6:2007
61937-6  IEC:2006(E) – 11 –
delay time is calculated as 21,333 ms. It is of equal value to the decoding time for one MPEG-
2 AAC frame data. Hence, the latency of MPEG-2 AAC decoding is approximately 26,708 ms.
The absolute maximum length of the data-burst is calculated as follows. In order to make a
burst, a minimum stuffing consists of 4 stuffing words (Pz of 16 bits) per burst. The repetition
period of data-burst in IEC 60958 frames is 1 024. Therefore, the maximum length of data-burst
leads to 1 024 sample * 2 ch * 16 bits – 4 word * 16 bits = 32 704 bits. The receiving delay
time is calculated as 21,29 ms in the case of the 48 kHz sampling frequency
(32 704/1 536 000 = 0,021 29). The decoding delay time is 21,333 ms as above. Hence, the
latency of MPEG-2 AAC decoding is a maximum of 42,62 ms.
For synchronization (for example, with video), the recommended value of latency is 42,62 ms.
A shorter latency is acceptable when synchronization is not required.
5.2.3 The data MPEG-2 AAC half-rate low sampling frequency
The stream of the data-bursts for MPEG-2 AAC half-rate low sampling frequency consists of
sequences of MPEG-2 AAC low sampling frequency ADTS frames. The data-type of an
MPEG-2 AAC low sampling frequency data-burst is 19; and the subdata type of an MPEG-
2 AAC half-rate low sampling frequency is 0. The data-burst is headed with a burst-preamble,
followed by the burst-payload, and stuffed with stuffing bits. The burst-payload of each data-
burst of the MPEG-2 AAC half-rate low sampling frequency data shall contain one complete
MPEG-2 AAC half-rate low sampling frequency ADTS frame, and represents 2 048 samples
for each encoded channel. The length of the MPEG-2 AAC half-rate low sampling frequency
data-burst depends on the encoded bit rate (which determines the MPEG-2 AAC half-rate low
sampling frequency ADTS frame length). The reference to the specification for the MPEG-
2 AAC half-rate low sampling frequency bitstream, representing 2 048 samples of encoded
audio per frame may be found in ISO/IEC 13818-7.
MPEG-2 AAC low sample rate
MPEG-2 AAC low sample rate
Pa Pb Pc Pd Pa Pb Pc Pd
burst_payload
burs
...