IEC 61937-6:2006
(Main)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
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
IEC 61937-6:2006 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. This second edition of IEC 61937-6 cancels and replaces the first edition published in 2002. It contains the following significant technical changes:
- addition of data-type for MPEG2 AAC low sampling frequency;
- addition of data-type for MPEG-4 AAC.
Audionumérique - Interface pour les flux de bits audio à codage MIC non linéaire conformement 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.
General Information
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Standards Content (Sample)
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
Reference number
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edition numbers 1.0, 1.1 and 1.2 refer, respectively, to the base publication, the
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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
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International Electrotechnical Commission
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For price, see current catalogue
– 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
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
– 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
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“IEC Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee
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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.
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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.
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.
– 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
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
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
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.
– 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
rate low sampling frequency
01 Subdata-type for MPEG-2 AAC ADTS Bit 0 of Pa 4 096
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
01 Subdata-type for MPEG4 AAC half-rate Bit 0 of Pa 2 048
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
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.
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.
– 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
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
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 3 – MPEG-2 AAC half-rate low sampling frequency data-burst
The data-type-dependent information for the MPEG-2 AAC half-rate low sampling frequency is
given in Table 7.
Table 7 – Data-type-dependent information for data-type MPEG-2 AAC
half-rate low sampling frequency
Bits of Pc Value Contents
LSB.MSB
8-12 0 No indication
1 LC profile
2, 3 Reserved for future profile
4 LC profile with SBR
5-31 Reserved
The reference point of an MPEG-2 AAC half-rate low sampling frequency data-burst is bit 0 of
Pa and occurs exactly once every 2 048 sampling periods. The data-burst containing the
– 12 – 61937-6 IEC:2006(E)
MPEG-2 AAC half-rate low sampling frequency frames shall occur at a regular rate, with the
reference point of each MPEG-2 AAC half-rate low sampling frequency data-burst beginning
2 048 IEC 60958 frames after the reference point of the preceding MPEG-2 AAC half-rate low
sampling frequency 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
half-rate low sampling frequency bitstream as described in IEC 61937, and that pause data-
bursts be transmitted with a repetition period of 64 IEC 60958 frames, except when other
repetition periods are necessary to fill the precise stream gap length (which may not be a
multiple of 64 IEC 60958 frames) or to meet the requirement on burst spacing (see
IEC 61937).
When a stream gap in an MPEG-2 AAC half-rate low sampling frequency stream is filled by a
sequence of pause data-bursts, the Pa of the first pause data-burst shall be located 2 048
sampling periods following the Pa of the previous MPEG-2 AAC half-rate low sampling
frequency 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 64
IEC 60958 frame length of the pause data-burst) the Pa of the first MPEG-2 AAC half-rate low
sampling frequency 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 half-rate
low sampling frequency decoder
...
IEC 61937-6 ®
Edition 2.0 2006-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
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
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
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IEC 61937-6 ®
Edition 2.0 2006-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
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
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
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX S
ICS 33.160.60; 35.040 ISBN 978-2-83220-529-7
– 2 – 61937-6 IEC:2006
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 8 – Latency of MPEG-4 AAC decoding . 16
Figure 9 – MPEG-4 AAC half-rate low sampling frequency data-burst . 16
Figure 10 – Latency of MPEG-4 AAC half-rate low sampling frequency decoding . 17
Figure 11 – MPEG-4 AAC quarter-rate low sampling frequency data-burst . 18
Figure 12 – Latency of MPEG-4 AAC quarter-rate low sampling frequency decoding . 19
Figure 13 – MPEG-4 AAC double-rate high sampling frequency data-burst . 20
Figure 14 – 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
61937-6 IEC:2006 – 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
– 4 – 61937-6 IEC:2006
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.
61937-6 IEC:2006 – 5 –
This bilingual version (2012-12) corresponds to the monolingual English version, published in
2006-01.
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.
The French version of this standard has not been voted upon.
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.
– 6 – 61937-6 IEC: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
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
61937-6 IEC:2006 – 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
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
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.
– 8 – 61937-6 IEC:2006
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
rate low sampling frequency
01 Subdata-type for MPEG-2 AAC ADTS Bit 0 of Pa 4 096
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
01 Subdata-type for MPEG4 AAC half-rate Bit 0 of Pa 2 048
low sampling frequency
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
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.
61937-6 IEC:2006 – 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.
– 10 – 61937-6 IEC:2006
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
61937-6 IEC:2006 – 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
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 3 – MPEG-2 AAC half-rate low sampling frequency data-burst
The data-type-dependent information for the MPEG-2 AAC half-rate low sampling frequency is
given in Table 7.
Table 7 – Data-type-dependent information for data-type MPEG-2 AAC
half-rate low sampling frequency
Bits of Pc Value Contents
LSB.MSB
8-12 0 No indication
1 LC profile
2, 3 Reserved for future profile
4 LC profile with SBR
5-31 Reserved
The reference point of an MPEG-2 AAC half-rate low sampling frequency data-burst is bit 0 of
Pa and occurs exactly once every 2 048 sampling periods. The data-burst containing the
– 12 – 61937-6 IEC:2006
MPEG-2 AAC half-rate low sampling frequency frames shall occur at a regular rate, with the
reference point of each MPEG-2 AAC half-rate low sampling frequency data-burst beginning
2 048 IEC 60958 frames after the reference point of the preceding MPEG-2 AAC half-rate low
sampling frequency 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
half-rate low sampling frequency bitstream as described in IEC 61937, and that pause data-
bursts be transmitted with a repetition period of 64 IEC 60958 frames, except when other
repetition periods are necessary to fill the precise stream gap length (which may not be a
multiple of 64 IEC 60958 frames) or to meet the requirement on burst spacing (see
IEC 61937).
When a stream gap in an MPEG-2 AAC half-rate low sampling frequency stream is filled by a
sequence of pause data-bursts, the Pa of the first pause data-burst shall be located 2 048
sampling periods following the Pa of the previous MPEG-2 AAC half-rate low sampling
frequency 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 64
IEC 60958 frame length of the pause data-burst) the Pa of the first MPEG-2 AAC half-rate low
sampling frequency 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 half-rate
low sampling frequency decoder as an indication of the number of decoded PCM samples
which are missing (due to the resulting audio gap).
5.2.4 Latency of MPEG-2 AAC half-rate low sampling frequency decoding
The latency of an external audio decoder to decode the MPEG-2 AAC half-rate low sampling
frequency is defined as the sum of the receiving delay time and the decoding delay time.
MPEG-2 AAC low sample MPEG-2 AAC low sample
Pa Pb Pc Pd Pa Pb Pc Pd
rate burst_payload rate 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 low sampling frequency decoder
Figure 4 – Latency of MPEG-2 AAC half-rate low sampling frequency decoding
EXAMPLE The receiving delay time to receive a whole data-burst with maximum length is
calculated as follows. The length of the preamble is 64 bits. The maximum length of the whole
data-burst payload is 4 096 bits in the Japanese satellite DTV specified maximum bit rate of
96 kbit/s. In this case, the maximum length of data-bursts is 4 096 bits. The receiving delay
time is calculated as 2,667 ms in the case of 48 kHz sampling frequency. The decoding delay
time is calculated as 42,667 ms. It is equal to the decoding time for one MPEG-2 AAC half-
rate low sampling frequency frame data. Hence, the latency of MPEG-2 AAC half-rate low
sampling frequency decoding is approximately 45,333 ms.
The absolute maximum length of 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 2 048. Therefore, the maximum length of data-burst leads to
2 048 sample * 2 ch * 16 bit – 4 word * 16 bit = 65 472 bits. The receiving delay time is
calculated as 42,625 ms in the case of 48 kHz sampling frequency (65 472/1 536 000 = 0,042
625). The decoding delay time is 42,667 ms as above. Hence, the latency of the MPEG-
2 AAC half-rate low sampling frequency decoding is a maximum of 85,29 ms.
61937-6 IEC:2006 – 13 –
For synchronization (for example, with video), the recommended value of latency is 85,29 ms.
A shorter latency is acceptable when synchronization is not required.
5.2.5 The data MPEG-2 AAC quarter-rate low sampling frequency
The stream of the data-bursts for the MPEG-2 AAC quarter-rate low sampling frequency
consists of sequences of the MPEG-2 AAC quarter-rate low sampling frequency ADTS frames.
The data-type of an MPEG-2 AAC quarter-rate low sampling frequency data-burst is 19 and
the subdata type of an MPEG-2 AAC quarter-rate low sampling frequency is 1. 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 quarter-rate low sampling
frequency data shall contain one complete MPEG-2 AAC quarter-rate low sampling frequency
ADTS frame, and represents 4 096 samples for each encoded channel. The length of the
MPEG-2 AAC quarter-rate low sampling frequency data-burst depends on the encoded bit
rate (which determines the MPEG-2 AAC quarter-rate low sampling frequency ADTS frame
length). The reference to the specification for the MPEG-2 AAC quarter-rate low sampling
frequency bitstream, representing 4 096 samples of encoded audio per frame may be found in
ISO/IEC 13818-7.
MPEG-2 AAC low sample MPEG-2 AAC low sample
Pa Pc
Pa Pb Pc Pd Pb Pd
rate burst_payload
rate 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 5 – MPEG-2 AAC quarter-rate low sampling frequency data-burst
The data-type-dependent information for MPEG-2 AAC quarter-rate low sampling frequency is
given in Table 8.
Table 8 – Data-type-dependent information for data-type MPEG-2 AAC
quarter-rate low sampling frequency
Bits of Pc Value Contents
LSB.MSB
8-12 0 No indication
1 LC profile
2, 3 Reserved for future profile
4 LC profile with SBR
5-31 Reserved
The reference point of a MPEG-2 AAC quarter-rate low sampling frequency data-burst is bit 0
of Pa and occur exactly once every 4 096 sampling periods. The data-burst containing MPEG-
2 AAC quarter-rate low sampling frequency frames shall occur at a regular rate, with the
reference point of each MPEG-2 AAC quarter-rate low sampling frequency data-burst
beginning 4 096 IEC 60958 frames after the reference point of the preceding MPEG-2 AAC
quarter-rate low sampling frequency data-burst (of the same bitstream number).
– 14 – 61937-6 IEC:2006
It is recommended that pause data-bursts are used to fill stream gaps in the MPEG-2 AAC
quarter-rate low sampling frequency bitstream as described in IEC 61937, and that pause
data-bursts be transmitted with a repetition period of 128 IEC 60958 frames, except when
other repetition periods are necessary to fill the precise stream gap length (which may not be
a multiple of 128 IEC 60958 frames), or to meet the requirement on burst spacing (see
IEC 61937).
When a stream gap in an MPEG-2 AAC quarter-rate low sampling frequency stream is filled
by a sequence of pause data-bursts, the Pa of the first pause data-burst shall be located
4 096 sampling periods following the Pa of the previous MPEG-2 AAC quarter-rate low
sampling frequency 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 64 IEC 60958 frame length of the pause data-burst) the Pa of the first MPEG-
2 AAC quarter-rate low sampling frequency 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 quarter-rate low sampling frequency decoder as an indication of the number of
decoded PCM samples which are missing (due to the resulting audio gap).
5.2.6 Latency of MPEG-2 AAC quarter-rate low sampling frequency decoding
The latency of an external audio decoder to decode MPEG-2 AAC quarter-rate low sampling
frequency is defined as the sum of the receiving delay time and the decoding delay time.
MPEG-2 AAC low sample MPEG-2 AAC low sample
Pa Pb Pc Pd Pa Pb Pc Pd
rate burst_payload rate 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 low sampling frequency decoder
Figure 6 – Latency of MPEG-2 AAC quarter-rate low sampling frequency decoding
The absolute maximum length of data-burst is calculated as follows. In order to make a burst,
a minimum stuffing consists of 4 stuffing words (Pz of 16 bit) per burst. The repetition period of
data-burst in IEC 60958 frames is 4 096. Therefore, the maximum length of a data-burst leads to
4 096 sample * 2 ch * 16 bit – 4 word * 16 bit = 131 008 bit. The receiving delay time is
calculated as 85,29 ms in the case of the 48 kHz sampling frequency (131 008/1 536 000 =
0,085 29). The decoding delay time is 85,33 ms as above. Hence, the latency of MPEG-
2 AAC quarter-rate low sampling frequency decoding is a maximum of 170,62 ms.
For synchronization (for example, with video), the recommended value of latency is
170,62 ms. A shorter latency is acceptable when synchronization is not required.
5.2.7 The data MPEG-4 AAC
The stream of the data-bursts for MPEG-4 AAC consists of sequences of MPEG-4 AAC ADTS
frames. The data-type of a MPEG-4 AAC data-burst is 20. And the subdata type of an MPEG-
4 AAC 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 MPEG-4 AAC data shall
contain one complete MPEG-4 AAC ADTS frame and represents 1 024 samples for each
encoded channel. The length of the MPEG-4 AAC data-burst depends on the encoded bit rate
(which determines the MPEG-4 AAC ADTS frame length). The reference to the specification
for the MPEG-4 AAC bitstream, representing 1 024 samples of encoded audio per frame, is
found in ISO/IEC 14496-3 .
61937-6 IEC:2006 – 15 –
MPEG-4 AAC MPEG-4 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-4 AAC frames
Repetition period of the burst
Figure 7 – MPEG-4 AAC data-burst
The data-type-dependent information for MPEG-4 AAC is given in Table 9.
Table 9 – Data-type-dependent information for data-type MPEG-4 AAC
Bits of Pc Value Contents
LSB.MSB
8-12 00 No indication
01 AAC profile, format for transmission is ADTS
02, 03 Reserved for future profile
04 HE-AAC profile, format for transmission is ADTS
05-31 Reserved
The reference point of an MPEG-4 AAC data-burst is bit 0 of Pa and occurs exactly once
every 1 024 sampling periods. The data-burst containing MPEG-4 AAC frames shall occur at
a regular rate, with the reference point of each MPEG-4 AAC data-burst beginning 1 024
IEC 60958 frames after the reference point of the preceding MPEG-4 AAC data-burst (of the
same bitstream number).
It is recommended that pause data-bursts are used to fill stream gaps in the MPEG-4 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-4 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-4 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-
4 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-4 AAC decoder as an indication
of the number of decoded PCM samples which are missing (due to the resulting audio gap).
5.2.8 Latency of MPEG-4 AAC decoding
The latency of an external audio decoder to decode MPEG-4 AAC is defined as the sum of the
receiving delay time and the decoding delay time.
– 16 – 61937-6 IEC:2006
MPEG-4 AAC MPEG-4 AAC
Pa Pb Pc Pd Pa Pb Pc Pd
burst-payload Burst-payload
Bit 0 of Pa
Bit 0 of Pa
MPEG-4 AAC frame Stuffing
MPEG-4 AAC frame
Repetition period of the burst
Receiving delay Decoding delay
Latency of MPEG-4 AAC decoder
Figure 8 – Latency of MPEG-4 AAC decoding
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 bit) 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 bit – 4 word * 16 bit = 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 36 000 =
0,021 9) The decoding delay time is 21,33 ms as above. Hence, the latency of MPEG-4 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.
5.2.9 The data MPEG-4 AAC half-rate low sampling frequency
The stream of the data-bursts for MPEG-4 AAC half-rate low sampling frequency consists of
sequences of MPEG-4 AAC low sampling frequency ADTS frames. The data-type of an
MPEG-4 AAC low sampling frequency data-burst is 20 and the subdata type of an MPEG-
4 AAC half-rate low sampling frequency is 1. 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-4 AAC half-rate low sampling frequency data shall contain one complete
MPEG-4 AAC half-rate low sampling frequency ADTS frame and represents 2 048 samples for
each encoded channel. The length of the MPEG-4 AAC half-rate low sampling frequency
data-burst depends on the encoded bit rate (which determines the MPEG-4 AAC half-rate low
sampling frequency ADTS frame length). The reference to the specification for the MPEG-
4 AAC half-rate low sampling frequency bitstream, representing 2 048 samples of encoded
audio per frame is found in ISO/IEC 14496-3.
MPEG-4 AAC low sample rate MPEG-4 AAC low sample rate
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-4 AAC frames
Repetition period of the burst
Figure 9 – MPEG-4 AAC half-rate low sampling frequency data-burst
The data-type-dependent information for MPEG-4 AAC half-rate low sampling frequency is
given in Table 10.
61937-6 IEC:2006 – 17 –
Table 10 – Data-type-dependent information for data-type MPEG-4 AAC
half-rate low sampling frequency
Bits of Pc Value Contents
LSB.MSB
8-12 0 No indication
1 AAC profile, Format for transmission is ADTS
2, 3 Reserved for future profile
4 HE-AAC profile, format for transmission is ADTS
5-31 Reserved
The reference point of an MPEG-4 AAC half-rate low sampling frequency data-burst is bit 0 of
Pa and occurs exactly once every 2 048 sampling periods. The data-burst containing MPEG-
4 AAC half-rate low sampling frequency frames shall occur at a regular rate, with the
reference point of each MPEG-4 AAC half-rate low sampling frequen
...
IEC 61937-6 ®
Edition 2.1 2014-01
CONSOLIDATED VERSION
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
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
Audionumérique – Interface pour les flux de bits audio à codage MIC non
linéaire conformément à l’IEC 60958 –
Partie 6: Flux de bits MIC non linéaire selon les formats MPEG-2 AAC et MPEG-4
AAC
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IEC 61937-6 ®
Edition 2.1 2014-01
CONSOLIDATED VERSION
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
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
Audionumérique – Interface pour les flux de bits audio à codage MIC non
linéaire conformément à l’IEC 60958 –
Partie 6: Flux de bits MIC non linéaire selon les formats MPEG-2 AAC et MPEG-4
AAC
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 33.160.60; 35.040 ISBN 978-2-8322-1372-8
IEC 61937-6 ®
Edition 2.1 2014-01
CONSOLIDATED VERSION
REDLINE VERSION
VERSION REDLINE
colour
inside
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
Audionumérique – Interface pour les flux de bits audio à codage MIC non
linéaire conformément à l’IEC 60958 –
Partie 6: Flux de bits MIC non linéaire selon les formats MPEG-2 AAC et MPEG-4
AAC
– 2 – 61937-6 IEC:2006+A1:2014
CONTENTS
FOREWORD . 4
INTRODUCTION TO AMENDMENT 1 . 6
1 Scope . 7
2 Normative references . 7
3 Terms, definitions, abbreviations and presentation convention . 7
3.1 Terms and definitions . 7
3.2 Abbreviations . 8
3.3 Presentation convention . 8
4 Mapping of the audio bitstream on to IEC 61937 . 8
4.1 MPEG-2 AAC burst-info . 8
4.2 MPEG-4 AAC burst-info . 9
5 Format of MPEG-2 AAC and MPEG-4 AAC data-bursts . 10
5.1 Pause data-burst . 10
5.2 Audio data-bursts . 10
Figure 1 – MPEG-2 AAC data-burst . 11
Figure 2 – Latency of MPEG-2 AAC decoding . 12
Figure 3 – MPEG-2 AAC half-rate low sampling frequency data-burst . 12
Figure 4 – Latency of MPEG-2 AAC half-rate low sampling frequency decoding . 14
Figure 5 – MPEG-2 AAC quarter-rate low sampling frequency data-burst . 15
Figure 6 – Latency of MPEG-2 AAC quarter-rate low sampling frequency decoding . 16
Figure 7 – MPEG-4 AAC data-burst . 16
Figure 8 – Latency of MPEG-4 AAC decoding . 18
Figure 9 – MPEG-4 AAC half-rate low sampling frequency data-burst . 18
Figure 10 – Latency of MPEG-4 AAC half-rate low sampling frequency decoding . 20
Figure 11 – MPEG-4 AAC quarter-rate low sampling frequency data-burst . 20
Figure 12 – Latency of MPEG-4 AAC quarter-rate low sampling frequency decoding . 22
Figure 13 – MPEG-4 AAC double-rate high sampling frequency data-burst . 22
Figure 14 – Latency of MPEG-4 AAC double-rate high sampling frequency decoding . 23
Table 1 – Fields of burst-info (data-type=7) . 9
Table 2 – Fields of burst-info (data-type=19) . 9
Table 3 – Fields of burst-info (data-type=20) . 9
Table 4 – Repetition period of pause data-bursts . 10
Table 5 – Repetition period of pause data-bursts . 10
Table 6 – Data-type-dependent information for data-type MPEG-2 AAC . 11
Table 7 – Data-type-dependent information for data-type MPEG-2 AAC
half-rate low sampling frequency. 13
Table 8 – Data-type-dependent information for data-type MPEG-2 AAC
quarter-rate low sampling frequency . 15
61937-6 IEC:2006+A1:2014 – 3 –
Table 9 – Data-type-dependent information for data-type MPEG-4 AAC . 17
Table 10 – Data-type-dependent information for data-type MPEG-4 AAC
half-rate low sampling frequency. 19
Table 11 – Data-type-dependent information for data-type MPEG-4 AAC
quarter-rate low sampling frequency . 21
Table 12 – Data-type-dependent information for data-type MPEG-4 AAC
double-rate high sampling frequency . 23
– 4 – 61937-6 IEC:2006+A1:2014
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
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5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
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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
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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 61937-6 edition 2.1 contains the second edition (2006-01) [documents 100/942/CDV
and 100/1043A/RVC] and its amendment 1 (2014-01) [documents 100/2052/CDV and
100/2117/RVC].
In this Redline version, a vertical line in the margin shows where the technical content is
modified by amendment 1. Additions and deletions are displayed in red, with deletions
being struck through. A separate Final version with all changes accepted is available in
this publication.
61937-6 IEC:2006+A1:2014 – 5 –
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 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.
The French version of this standard has not been voted upon.
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 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 publication using a colour printer.
– 6 – 61937-6 IEC:2006+A1:2014
INTRODUCTION TO AMENDMENT 1
The revision of IEC 61937-6:2006 has become necessary to define new additional data-type-
dependent information. This Amendment 1 contains the following significant technical
changes with respect to the base publication. The revised items apply to the small parts of
IEC 61937-6.
• LC profile with MPEG Surround, LC profile with SBR and MPEG Surround in MPEG-2 AAC
are defined data-type-dependent information field in Pc.
• HE-AAC V2 profile itself, and MPEG-4 AAC profile, HE-AAC profile, HE-AAC V2 profile
combined with MPEG Surround respectively are defined data-type-dependent information
field in Pc.
61937-6 IEC:2006+A1:2014 – 7 –
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)
ISO/IEC 23003-1, Information technology – MPEG audio technologies – Part 1: MPEG
Surround
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
– 8 – 61937-6 IEC:2006+A1:2014
3.1.2
MPEG-2 AAC LC profile
MPEG-2 AAC low complexity profile identified in ISO/IEC 13818-7
3.1.3
MPEG-2 AAC LC profile with SBR
MPEG-2 AAC 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
MPEG-4 AAC profile
MPEG-4 AAC profile identified in ISO/IEC 14496-3
3.1.6
MPEG-4 HE-AAC profile
MPEG-4 HE-AAC profile identified in ISO/IEC 14496-3
3.1.7
MPEG-4 HE-AAC V2 profile
MPEG-4 HE-AAC V2 profile identified in ISO/IEC 14496-3
3.1.8
MPEG Surround
technology used for coding of multichannel signals based on a down mixed signal of the
original multichannel signal, and associated spatial parameters
Note 1 to entry: MPEG Surround in defined in ISO/IEC 23003-1.
3.2 Abbreviations
AAC Advanced Audio Coding
ADTS Audio Data Transport Stream
SBR Spectral Band Replication
HE-AAC MPEG-4 High Efficiency AAC
HE-AAC V2 MPEG-4 High Efficiency AAC Version 2
MPEG Moving Picture Experts Group
3.3 Presentation convention
01 Value “01” in binary 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.
4.1 MPEG-2 AAC burst-info
MPEG-2 AAC burst-info (data-type=7) is given in Table 1.
61937-6 IEC:2006+A1:2014 – 9 –
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
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.
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
rate low sampling frequency
01 Subdata-type for MPEG-2 AAC ADTS Bit 0 of Pa 4 096
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
Subdata-type for MPEG4 AAC Bit 0 of Pa 1024
01 Subdata-type for MPEG4 AAC half-rate Bit 0 of Pa 2 048
low sampling frequency
10 Subdata-type for MPEG4 AAC quarter-rate Bit 0 of Pa 4 096
low sampling frequency
112 Subdata-type for MPEG4 AAC double-rate Bit 0 of Pa 512
high sampling frequency
7-15 In accordance with IEC 61937-1 and
IEC 61937-2
– 10 – 61937-6 IEC:2006+A1:2014
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.
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.
61937-6 IEC:2006+A1:2014 – 11 –
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.
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.
– 12 – 61937-6 IEC:2006+A1:2014
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
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
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 3 – MPEG-2 AAC half-rate low sampling frequency data-burst
61937-6 IEC:2006+A1:2014 – 13 –
The data-type-dependent information for the MPEG-2 AAC half-rate low sampling frequency is
given in Table 7.
Table 7 – Data-type-dependent information for data-type MPEG-2 AAC
half-rate low sampling frequency
Bits of Pc Value Contents
LSB.MSB
8-12 00 No indication
01 LC profile
02, 3 Reserved for future profile
03 LC profile with MPEG Surround
04 LC profile with SBR
05-31, 06 Reserved
07 LC profile with SBR and MPEG Surround
08-31 Reserved
The reference point of an MPEG-2 AAC half-rate low sampling frequency data-burst is bit 0 of
Pa and occurs exactly once every 2 048 sampling periods. The data-burst containing the
MPEG-2 AAC half-rate low sampling frequency frames shall occur at a regular rate, with the
reference point of each MPEG-2 AAC half-rate low sampling frequency data-burst beginning
2 048 IEC 60958 frames after the reference point of the preceding MPEG-2 AAC half-rate low
sampling frequency 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
half-rate low sampling frequency bitstream as described in IEC 61937, and that pause data-
bursts be transmitted with a repetition period of 64 IEC 60958 frames, except when other
repetition periods are necessary to fill the precise stream gap length (which may not be a
multiple of 64 IEC 60958 frames) or to meet the requirement on burst spacing (see
IEC 61937).
When a stream gap in an MPEG-2 AAC half-rate low sampling frequency stream is filled by a
sequence of pause data-bursts, the Pa of the first pause data-burst shall be located 2 048
sampling periods following the Pa of the previous MPEG-2 AAC half-rate low sampling
frequency 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 64
IEC 60958 frame length of the pause data-burst) the Pa of the first MPEG-2 AAC half-rate low
sampling frequency 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 half-rate
low sampling frequency decoder as an indication of the number of decoded PCM samples
which are missing (due to the resulting audio gap).
5.2.4 Latency of MPEG-2 AAC half-rate low sampling frequency decoding
The latency of an external audio decoder to decode the MPEG-2 AAC half-rate low sampling
frequency is defined as the sum of the receiving delay time and the decoding delay time.
– 14 – 61937-6 IEC:2006+A1:2014
MPEG-2 AAC low sample MPEG-2 AAC low sample
Pa Pb Pc Pd Pa Pb Pc Pd
rate burst_payload rate 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 low sampling frequency decoder
Figure 4 – Latency of MPEG-2 AAC half-rate low sampling frequency decoding
EXAMPLE The receiving delay time to receive a whole data-burst with maximum length is
calculated as follows. The length of the preamble is 64 bits. The maximum length of the whole
data-burst payload is 4 096 bits in the Japanese satellite DTV specified maximum bit rate of
96 kbit/s. In this case, the maximum length of data-bursts is 4 096 bits. The receiving delay
time is calculated as 2,667 ms in the case of 48 kHz sampling frequency. The decoding delay
time is calculated as 42,667 ms. It is equal to the decoding time for one MPEG-2 AAC half-
rate low sampling frequency frame data. Hence, the latency of MPEG-2 AAC half-rate low
sampling frequency decoding is approximately 45,333 ms.
The absolute maximum length of 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 2 048. Therefore, the maximum length of data-burst leads to
2 048 sample * 2 ch * 16 bit – 4 word * 16 bit = 65 472 bits. The receiving delay time is
calculated as 42,625 ms in the case of 48 kHz sampling frequency (65 472/1 536 000 = 0,042
625). The decoding delay time is 42,667 ms as above. Hence, the latency of the MPEG-
2 AAC half-rate low sampling frequency decoding is a maximum of 85,29 ms.
For synchronization (for example, with video), the recommended value of latency is 85,29 ms.
A shorter latency is acceptable when synchronization is not required.
5.2.5 The data MPEG-2 AAC quarter-rate low sampling frequency
The stream of the data-bursts for the MPEG-2 AAC quarter-rate low sampling frequency
consists of sequences of the MPEG-2 AAC quarter-rate low sampling frequency ADTS frames.
The data-type of an MPEG-2 AAC quarter-rate low sampling frequency data-burst is 19 and
the subdata type of an MPEG-2 AAC quarter-rate low sampling frequency is 1. 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 quarter-rate low sampling
frequency data shall contain one complete MPEG-2 AAC quarter-rate low sampling frequency
ADTS frame, and represents 4 096 samples for each encoded channel. The length of the
MPEG-2 AAC quarter-rate low sampling frequency data-burst depends on the encoded bit
rate (which determines the MPEG-2 AAC quarter-rate low sampling frequency ADTS frame
length). The reference to the specification for the MPEG-2 AAC quarter-rate low sampling
frequency bitstream, representing 4 096 samples of encoded audio per frame may be found in
ISO/IEC 13818-7.
61937-6 IEC:2006+A1:2014 – 15 –
MPEG-2 AAC low sample MPEG-2 AAC low sample
Pa Pb Pc Pd Pa Pb Pc
Pd
rate burst_payload
rate 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 5 – MPEG-2 AAC quarter-rate low sampling frequency data-burst
The data-type-dependent information for MPEG-2 AAC quarter-rate low sampling frequency is
given in Table 8.
Table 8 – Data-type-dependent information for data-type MPEG-2 AAC
quarter-rate low sampling frequency
Bits of Pc Value Contents
LSB.MSB
8-12 00 No indication
01 LC profile
02, 3 Reserved for future profile
03 LC profile with MPEG Surround
04 LC profile with SBR
05-31, 06 Reserved
07 LC profile with SBR and MPEG Surround
08-31 Reserved
The reference point of a MPEG-2 AAC quarter-rate low sampling frequency data-burst is bit 0
of Pa and occur exactly once every 4 096 sampling periods. The data-burst containing MPEG-
2 AAC quarter-rate low sampling frequency frames shall occur at a regular rate, with the
reference point of each MPEG-2 AAC quarter-rate low sampling frequency data-burst
beginning 4 096 IEC 60958 frames after the reference point of the preceding MPEG-2 AAC
quarter-rate low sampling frequency 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
quarter-rate low sampling frequency bitstream as described in IEC 61937, and that pause
data-bursts be transmitted with a repetition period of 128 IEC 60958 frames, except when
other repetition periods are necessary to fill the precise stream gap length (which may not be
a multiple of 128 IEC 60958 frames), or to meet the requirement on burst spacing (see
IEC 61937).
When a stream gap in an MPEG-2 AAC quarter-rate low sampling frequency stream is filled
by a sequence of pause data-bursts, the Pa of the first pause data-burst shall be located
4 096 sampling periods following the Pa of the previous MPEG-2 AAC quarter-rate low
sampling frequency 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 64 IEC 60958 frame length of the pause data-burst) the Pa of the first MPEG-
2 AAC quarter-rate low sampling frequency 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 quarter-rate low sampling frequency decoder as an indication of the number of
decoded PCM samples which are missing (due to the resulting audio gap).
– 16 – 61937-6 IEC:2006+A1:2014
5.2.6 Latency of MPEG-2 AAC quarter-rate low sampling frequency decoding
The latency of an external audio decoder to decode MPEG-2 AAC quarter-rate low sampling
frequency is defined as the sum of the receiving delay time and the decoding delay time.
MPEG-2 AAC low sample MPEG-2 AAC low sample
Pa Pb Pc Pd Pa Pb Pc Pd
rate burst_payload rate 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 low sampling frequency decoder
Figure 6 – Latency of MPEG-2 AAC quarter-rate low sampling frequency decoding
The absolute maximum length of data-burst is calculated as follows. In order to make a burst,
a minimum stuffing consists of 4 stuffing words (Pz of 16 bit) per burst. The repetition period of
data-burst in IEC 60958 frames is 4 096. Therefore, the maximum length of a data-burst leads to
4 096 sample * 2 ch * 16 bit – 4 word * 16 bit = 131 008 bit. The receiving delay time is
calculated as 85,29 ms in the case of the 48 kHz sampling frequency (131 008/1 536 000 =
0,085 29). The decoding delay time is 85,33 ms as above. Hence, the latency of MPEG-
2 AAC quarter-rate low sampling frequency decoding is a maximum of 170,62 ms.
For synchronization (for example, with video), the recommended value of latency is
170,62 ms. A shorter latency is acceptable when synchronization is not required.
5.2.7 The data MPEG-4 AAC
The stream of the data-bursts for MPEG-4 AAC consists of sequences of MPEG-4 AAC ADTS
frames. The data-type of a MPEG-4 AAC data-burst is 20. And the subdata type of an MPEG-
4 AAC 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 MPEG-4 AAC data shall
contain one complete MPEG-4 AAC ADTS frame and represents 1 024 samples for each
encoded channel. The length of the MPEG-4 AAC data-burst depends on the encoded bit rate
(which determines the MPEG-4 AAC ADTS frame length). The reference to the specification
for the MPEG-4 AAC bitstream, representing 1 024 samples of encoded audio per frame, is
found in ISO/IEC 14496-3 .
MPEG-4 AAC MPEG-4 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-4 AAC frames
Repetition period of the burst
Figure 7 – MPEG-4 AAC data-burst
The data-type-dependent information for MPEG-4 AAC is given in Table 9.
61937-6 IEC:2006+A1:2014 – 17 –
Table 9 – Data-type-dependent information for data-type MPEG-4 AAC
Bits of Pc Value Contents
LSB.MSB
8-12 00 No indication
01 AAC profile, format for transmission is ADTS
02, 03 Reserved for future profile
03 AAC profile with MPEG Surround, format for transmission is
ADTS, MPEG Surround data complies to MPEG Surround
baseline profile
04 HE-AAC profile, format for transmission is ADTS
05-31 Reserved
06 HE-AAC profile with MPEG Surround, format for
transmission is ADTS, MPEG Surround data complies to
MPEG Surround baseline profile
07-11 Reserved
12 HE-AAC V2 profile, format for transmission is ADTS.
13 Reserved
14 HE-AAC V2 profile with MPEG Surround, format for
transmission is ADTS, MPEG Surround data complies to
MPEG Surround baseline profile.
15-31 Reserved
The reference point of an MPEG-4 AAC data-burst is bit 0 of Pa and occurs exactly once
every 1 024 sampling periods. The data-burst containing MPEG-4 AAC frames shall occur at
a regular rate, with the reference point of each MPEG-4 AAC data-burst beginning 1 024
IEC 60958 frames after the reference point of the preceding MPEG-4 AAC data-burst (of the
same bitstream number).
It is recommended that pause data-bursts are used to fill stream gaps in the MPEG-4 AAC bit-
stream as described in IEC 61
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