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

Status
Published
Publication Date
24-Jan-2006
Current Stage
PPUB - Publication issued
Start Date
25-Jan-2006
Completion Date
25-Jan-2006
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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 formats
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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
IEC 61937-6:2006
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
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

Warning! Make sure that you obtained this publication from an authorized distributor.

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
---------------------- Page: 3 ----------------------
– 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

---------------------- Page: 4 ----------------------
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

---------------------- Page: 5 ----------------------
– 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.
---------------------- Page: 6 ----------------------
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.
---------------------- Page: 7 ----------------------
– 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
---------------------- Page: 8 ----------------------
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.
---------------------- Page: 9 ----------------------
– 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
102
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.
---------------------- Page: 10 ----------------------
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.
---------------------- Page: 11 ----------------------
– 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

---------------------- Page: 12 ----------------------
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

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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 preci
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