IEC 61937-4:2003

IEC 61937-4 ®
Edition 1.0 2003-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Digital audio – Interface for non-linear PCM encoded audio bitstreams applying
IEC 60958
Part 4: Non-linear PCM bitstreams according to the MPEG audio format

Audionumérique – Interface pour les flux de bits audio à codage MIC non
linéaire conformément à la CEI 60958 –
Partie 4: Flux de bits MIC non linéaire selon les formats audio MPEG

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IEC 61937-4 ®
Edition 1.0 2003-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Digital audio – Interface for non-linear PCM encoded audio bitstreams applying

IEC 60958
Part 4: Non-linear PCM bitstreams according to the MPEG audio format

Audionumérique – Interface pour les flux de bits audio à codage MIC non

linéaire conformément à la CEI 60958 –

Partie 4: Flux de bits MIC non linéaire selon les formats audio MPEG

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX M
ICS 33.160.30 ISBN 978-2-83220-528-0

– 2 – 61937-4  IEC:2003
CONTENTS
FOREWORD . 3

1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
3.1 Definitions . 5
3.2 Abbreviations . 5
3.3 Presentation convention . 5
4 Mapping of the audio bitstream on to IEC 61937 . 6
5 Format of MPEG audio data-burst . 6
5.1 General . 6
5.2 Pause data-burst . 6
5.3 Audio data-types . 7
5.3.1 MPEG-1 layer-1 . 7
5.3.2 MPEG-1 layer-2 or -3, or MPEG-2 without extension . 7
5.3.3 MPEG-2 with extension . 8
5.3.4 MPEG-2 layer-1 low sampling frequency . 10
5.3.5 MPEG-2 layer-2 Low sampling frequency . 11
5.3.6 MPEG-2 layer-3 low sampling frequency . 11

Bibliography . 13

Figure 1 – MPEG-1 layer-1 data-burst . 7
Figure 2 – Data-burst with MPEG-1 layer 2 or 3 or MPEG-2 without extension . 8
Figure 3 – Latency of MPEG-1 layer 2 or 3 or MPEG-2 without extension . 8
Figure 4 – Format of MPEG-base-frame and MPEG-extension-frame . 9
Figure 5 – MPEG 2 with extension data-burst . 9
Figure 6 – Latency of MPEG-2 with extension . 10
Figure 7 – MPEG-2 layer-1 low sampling frequency data-burst . 10
Figure 8 – MPEG-2 layer-2 low sampling frequency data-burst . 11
Figure 9 – MPEG-2 layer-3 low sampling frequency data-burst . 12

Table 1 – Fields of burst-info . 6
Table 2 – Repetition period of pause data-bursts . 7
Table 3 – Data-type-dependent info for data-types 5 and 6 . 9

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

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

FOREWORD
1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of the IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, the IEC publishes International Standards. Their preparation is
entrusted to technical committees; any IEC National Committee interested in the subject dealt with may
participate in this preparatory work. International, governmental and non-governmental organizations liaising
with the IEC also participate in this preparation. The IEC collaborates closely with the International
Organization for Standardization (ISO) in accordance with conditions determined by agreement between the
two organizations.
2) The formal decisions or agreements of the IEC on technical matters express, as nearly as possible, an
international consensus of opinion on the relevant subjects since each technical committee has representation
from all interested National Committees.
3) The documents produced have the form of recommendations for international use and are published in the form
of standards, technical specifications, technical reports or guides and they are accepted by the National
Committees in that sense.
4) In order to promote international unification, IEC National Committees undertake to apply IEC International
Standards transparently to the maximum extent possible in their national and regional standards. Any
divergence between the IEC Standard and the corresponding national or regional standard shall be clearly
indicated in the latter.
5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with one of its standards.
6) Attention is drawn to the possibility that some of the elements of this International Standard may be the subject
of patent rights. The IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61937-4 has been prepared by technical area 4: Digital system
interfaces, of IEC technical committee 100: Audio, video and multimedia systems and
equipment.
This standard cancels and replaces IEC 61937, published in 2000, which has been divided
into four parts (see below). This first edition constitutes a technical revision.
This bilingual version (2012-12) corresponds to the monolingual English version, published in
2003-05.
The text of this standard is based on the following documents:
FDIS Report on voting
100/647/FDIS 100/673/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
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.

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

61937-4  IEC:2003 – 5 –
DIGITAL AUDIO –
INTERFACE FOR NON-LINEAR PCM ENCODED
AUDIO BITSTREAMS APPLYING IEC 60958 –

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

1 Scope
This part of IEC 61937 specifies the method for the digital audio interface specified in
IEC 60958 to convey non-linear PCM bitstreams encoded in accordance with the MPEG audio.
2 Normative references
The following referenced documents are indispensable for the application of this document.
For dated references, only the edition cited applies. For undated references, the latest edition
of the referenced document (including any amendments) applies.
IEC 60958 (all parts), Digital audio interface
IEC 61937-1, Digital audio – Interface for non-linear PCM encoded audio bitstreams applying
IEC 60958 – Part 1: General
3 Terms and definitions
For the purposes of this document, the following definitions, abbreviations and presentation
convention apply.
3.1 Definitions
3.1.1
latency
delay time of an external audio decoder to decode an AC-3 data-burst, defined as the sum of
two values of the receiving delay time and the decoding delay time
3.2 Abbreviations
3.2.1
ATSC
Advanced Television Systems Committee
3.2.2
MPEG
Moving Pictures Expert Group, a joint committee of ISO and IEC
3.2.3
ITU-R
International Telecommunication Union, Radio Communication Bureau
3.3 Presentation convention
F872h
Value ‘F872’ in hexadecimal format

– 6 – 61937-4  IEC:2003
4 Mapping of the audio bitstream on to IEC 61937
The coding of the bitstream and data-burst is in accordance with IEC 61937-1.
The 16-bit burst-info contains information about the data that will be found in the data-burst
(see Table 1).
Table 1 – Fields of burst-info
Repetition period of
Reference
Bits of Pc Value Contents data-burst in
point R
IEC 60958 frames
0 – 4 Data-type
0 – 3 According to IEC 61937
4 MPEG-1 layer-1 data Bit 0 of Pa 384
5 MPEG-1 layer-2 or -3 data, or MPEG-2 Bit 0 of Pa 1 152
without extension
6 MPEG-2 data with extension Bit 0 of Pa 1 152
7 MPEG-2 AAC Bit 0 of Pa 1 024
8 MPEG-2 layer-1 low sampling frequency Bit 0 of Pa 768
9 MPEG-2 layer-2 low sampling frequency Bit 0 of Pa 2 304
10 MPEG-2 layer-3 low sampling frequency Bit 0 of Pa 1 152
10 – 31 According to IEC 61937
5 – 15 According to IEC 61937

5 Format of MPEG audio data-burst
5.1 General
This clause specifies the audio data-burst of MPEG audio. Specific properties such as
reference points, repetition period, method of filling stream gaps and decoding latency are
specified.
The decoding latency (or delay), indicated for the data-types, should be used by the
transmitter to schedule data-bursts as necessary to establish synchronization between picture
and decoded audio.
5.2 Pause data-burst
Pause data-bursts for MPEG audio are given in Table 2.

61937-4  IEC:2003 – 7 –
Table 2 – Repetition period of pause data-bursts
Repetition period of pause data-burst
Data-type of audio data-burst
Mandatory Recommended
MPEG-1 layer-1 data 32 IEC 60958 frames
MPEG-1 layer-2 or -3 data, or MPEG-2 without extension 32 IEC 60958 frames
MPEG-2 data with extension 32 IEC 60958 frames
MPEG-2 layer-1 low sampling frequency 64 IEC 60958 frames
MPEG-2 layer-2 low sampling frequency 64 IEC 60958 frames
MPEG-2 layer-3 low sampling frequency 64 IEC 60958 frames

5.3 Audio data-types
5.3.1 MPEG-1 layer-1
An MPEG-1 layer-1 MPEG-frame represents 384 samples of each encoded channel and can
be transferred using data-type 04h. The data-burst is headed with a burst-preamble, followed
by the burst-payload.
Pa Pb Pc Pd MPEG-1 layer-1 burst_payload Pa Pb Pc Pd
Bit 0 of Pa Bit 0 of Pa
MPEG-1 layer-1 frame
Stuffing
Repetition period of the burst
IEC  1300/03
Figure 1 – MPEG-1 Layer-1 data-burst
In the case where pause data-bursts are used to fill stream gaps in the MPEG-1 layer-1 bit-
stream as described in IEC 61937-1, it is recommended that the pause data-bursts be
transmitted with a repetition period of 32 IEC 60958 frames. The total gap length shall be a
multiple of 32 IEC 60958 frames.
When a stream gap in an MPEG bitstream is filled by a sequence of pause data-bursts,
the Pa of the initial pause data-burst should be located at the 16-bit data word located
384 IEC 60958 frames following the Pa of the previous MPEG data-burst. The sequence(s) of
pause data-bursts that fill the stream gap shall continue from this point up to the Pa of the
first MPEG data-burst which follows the stream gap. The gap-length parameter contained in
the pause data-burst may be used to specify the number of decoded PCM samples that are
missing (due to the gap).
The latency of an audio decoder to decode an MPEG-1 layer-1 data-burst is not defined.
5.3.2 MPEG-1 layer-2 or -3, or MPEG-2 without extension
The burst-payload of data type MPEG-1 layer-2 or -3 MPEG-2 without extension represents
1 152 samples of each encoded channel and can be transferred using data-type 05h. The
data-burst is headed with a burst-preamble, followed by the burst-payload.

– 8 – 61937-4  IEC:2003
MPEG-1 layer-2 or -3 or MPEG-2
Pa Pb Pc Pd Pa Pb Pc Pd
without extension burst_payload
Bit 0 of Pa
Bit 0 of Pa
Stuffing
MPEG-1 layer-2 or -3 or MPEG-2
without extension frame
Repetition period of the burst
IEC  1301/03
Figure 2 – Data-burst with MPEG-1 layer-2 or -3 or MPEG-2 without extension
NOTE An MPEG-2 layer-1 super-frame contains 3 MPEG-1 layer-1 base-frames and the MPEG-extension-frame.
The MPEG layer-1 super-frame contains 3 × 384 = 1 152 samples per channel (see ISO/IEC 13818-3).
The data-type-dependent info for MPEG-1 layer-2 or -3 data or MPEG-2 without extension is
given in Table 3.
In the case where pause data-bursts are used to fill stream gaps in the MPEG-1 layer-2 or -3
data or MPEG-2 without extension bitstream as described in IEC 61937-1, it is recommended
that the pause data-bursts be transmitted with a repetition period of 32 IEC 60958 frames.
The total gap length shall be a multiple of 96 IEC 60958 frames.
When a stream gap in an MPEG bitstream is filled by a sequence of pause data-bursts,
the Pa of the initial pause data-burst should be located at the 16-bit data word located
1 152 IEC 60958 frames following the Pa of the previous MPEG data-burst. The sequence(s)
of pause data-bursts that fill the stream gap shall continue from this point up to the Pa of the
first MPEG data-burst which follows the stream gap. The gap-length parameter contained in
the pause data-burst may be used to specify the number of decoded PCM samples that are
missing (due to the gap).
MPEG-1 layer-2 or -3 or MPEG-2
Pa Pb Pc Pd Pa Pb Pc Pd
without extension burst_payload
Bit 0 of Pa Bit 0 of Pa
MPEG-1 layer-2 or -3 or MPEG-2
without extension frame
Stuffing
Time to receive data-burst, with maximum length
Decoding
delay
Latency of MPEG-1 layer-2 or -3
or MPEG-2 without extension
Repetition period of the burst
IEC  1302/03
Figure 3 – Latency of MPEG-1 layer-2 or -3 or MPEG-2 without extension
The latency of an audio decoder to decode a MPEG-1 layer-2 or -3 or MPEG-2 without
extension data-burst is defined as the time to receive the whole data-burst with maximum
length (16,75 ms for fs = 48 kHz), plus the decoding delay, which is the time to output the first
linear PCM sample (Figure 3, 4,15 ms for fs = 48 kHz). The latency is defined as a delay of
20,9 ms for fs = 48 kHz, 22,75 ms for fs = 44,1 kHz, and 31,35 ms for fs = 32 kHz.
5.3.3 MPEG-2 with extension
An MPEG-2 frame represents 1 152 samples of each encoded channel. The data type is 06h.
The data-burst is headed with a burst-preamble, followed by the burst-payload.

61937-4  IEC:2003 – 9 –
MPEG-1 MPEG-1 MPEG-1 MC MC side Ancillary Ext. MC side MC audio
Anc
header side info audio header info I data header info II data
MPEG-1 compatible MPEG-2 multi-channel
MPEG-2 extension frame
MPEG-2 base frame
MPEG-2 burst_payload
IEC  1303/03
Figure 4 – Format of MPEG-base-frame and MPEG-extension-frame

Pa Pb Pc Pd MPEG-2 burst_payload Pa Pb Pc Pd
Bit 0 of Pa Bit 0 of Pa
MPEG-2 base frame, with extension frame
Stuffing
Repetition period of burst
IEC  1304/03
Figure 5 – MPEG 2 with extension data-burst
NOTE An MPEG-2 layer-1 MPEG-super-frame contains 3 layer-1 base frames and the extension frame. The layer-
1 MPEG-super-frame contains 3 × 384 = 1 152 samples per channel (see ISO/IEC 13818-3).
The data-type-dependent info is given in Table 3.
Table 3 – Data-type-dependent info for data-types 5 and 6
Bits of Pc Value
Contents Remarks
LSB.MSB LSB.MSB
8 0 Normal mode Second stereo = second stereo
1 Karaoke mode Second stereo = Karaoke
9 – 10 00 Dynamic Range Control does not exist
in MPEG audio stream
10 Dynamic Range Control exists in MPEG
audio stream
01 Reserved
11 Reserved
11 – 12 00 Reserved
10 Reserved
01 Reserved
11 Reserved
In the case where pause data-bursts are used to fill stream gaps in the MPEG-2 with
extension bit stream as described in IEC 61937-1, it is recommended that the Pause data-
bursts be transmitted with a repetition period of 32 IEC 60958 frames. The total gap length
shall be a multiple of IEC 60958 frames. The total gap length shall be a multiple of 96 IEC
60958 frames.
– 10 – 61937-4  IEC:2003
When a stream gap in an MPEG bitstream is filled by a sequence of Pause data-bursts,
the Pa of the initial pause data-burst should be located at the 16-bit data word located
1 152 sampling periods following the Pa of the previous MPEG data-burst. The sequence(s) of
pause data-bursts that fill the stream gap shall continue from this point up to the Pa of the
first MPEG data-burst which follows the gap. The gap-length parameter contained in
the pause data-burst may be used to specify the number of decoded PCM samples that are
missing (due to the gap).
Pa Pb Pc Pd MPEG-2 burst-payload Pa Pb Pc Pd
MPEG-2 with
Bit 0 of Pa Bit 0 of Pa
extension frame
Stuffing
Time to receive data-burst, with maximum length
Decoding
delay
Latency of MPEG decoding
Repetition period of burst
IEC  1305/03
Figure 6 – Latency of MPEG-2 with extension
The latency of an audio decoder to decode an MPEG-2 with extension data-burst is defined
as the time to receive the whole data-burst with maximum length (16,75 ms for fs = 48 kHz),
plus the decoding delay, which is the time to output the first linear PCM sample (Figure 3,
4,15 ms for fs = 48 kHz). The latency is defined as a delay of 20,9 ms for fs = 48 kHz, 22,75
ms for fs = 44,1 kHz, and 31,35 ms for fs = 32 kHz.
5.3.4 MPEG-2 layer-1 low sampling frequency
An MPEG-2 layer-1 frame with low sampling frequency represents 384 samples of each
encoded channel and can be transferred using data-type 08h. The data-burst is headed with a
burst-preamble, followed by the burst-payload.
In the case where pause data-bursts are used to fill gaps in the MPEG-2 layer-1 low sampling
frequency bitstream as described in IEC 61937-1, it is recommended that the pause data-
bursts be transmitted with a repetition period of 64 IEC 60958 frames. The total gap length
shall be a multiple of 64 IEC 60958 frames.
MPEG-2 layer-1 low sample
Pa Pb Pc Pd Pa Pb Pc Pd
rate burst_payload
Bit 0 of Pa
Bit 0 of Pa
MPEG-2 layer-1 frame
Stuffing
Repetition period of the burst
IEC  1306/03
Figure 7 – MPEG-2 layer-1 low sampling frequency data-burst

61937-4  IEC:2003 – 11 –
When a stream gap in an MPEG bitstream is filled by a sequence of pause data-bursts, the
Pa of the initial pause data-burst should be located at the 16-bit data word located 768
IEC 60958 frames following the Pa of the previous MPEG data-burst. The sequence(s) of
pause data-bursts that fill the stream gap shall continue from this point up to the Pa of the
first MPEG data-burst which follows the stream gap. The gap-length parameter contained in
the pause data-burst may be used to specify the number of decoded PCM samples that are
missing (due to the gap).
The latency of an audio decoder to decode a MPEG-2 layer-1 low sampling frequency data-
burst is not defined.
5.3.5 MPEG-2 layer-2 Low sampling frequency
The payload of data type MPEG-2 layer-2 low sampling frequency represents 1 152 samples
of each encoded channel and can be transferred using data-type 09h. The data-burst is
headed with a burst-preamble, followed by the burst-payload.
MPEG-2 layer-2 low sample
Pa Pb Pc Pd Pa Pb Pc Pd
rate burst_payload
Bit 0 of Pa
Bit 0 of Pa
MPEG-2 layer-2 frame
Stuffing
Repetition period of the burst
IEC  1307/03
Figure 8 – MPEG-2 layer-2 low sampling frequency data-burst
In the case where pause data-bursts are used to fill gaps in the MPEG-2 Layer-2 Low
sampling frequency bitstream as described in IEC 61937-1, it is recommended that the pause
data-bursts be transmitted with a repetition period of 64 IEC 60958 frames. The total gap
length shall be a multiple of 192 IEC 60958 frames.
When a stream gap in an MPEG bitstream is filled by a sequence of pause data-bursts, the
Pa of the initial pause data-burst should be located at the 16-bit data word located 2 304
IEC 60958 frames following the Pa of the previous MPEG data-burst. The sequence(s)
of pause data-bursts that fill the stream gap shall continue from this point up to the Pa of
the first MPEG data-burst which follows the gap. The gap-length parameter contained in the
pause data-burst may be used to specify the number of decoded PCM samples that are
missing (due to the gap).
The latency of an audio decoder to decode a MPEG-2 layer-2 low sampling frequency data-
burst is not defined.
5.3.6 MPEG-2 layer-3 low sampling frequency
The payload of data type MPEG-2 layer-3 low sampling frequency represents 576 samples of
each encoded channel and can be transferred using data-type 0Ah. The data-burst is headed
with a burst-preamble, followed by the burst-payload.

– 12 – 61937-4  IEC:2003
MPEG-2 layer-3 low sample rate
Pa Pb Pc Pd Pa Pb Pc Pd
burst_payload
Bit 0 of Pa
Bit 0 of Pa
MPEG-2 layer-3 frame
Stuffing
Repetition period of the burst
IEC  1308/03
Figure 9 – MPEG-2 layer-3 low sampling frequency data-burst
In the case where pause data-bursts are used to fill gaps in the MPEG-2 layer-3 low sampling
frequency bit stream as described in IEC 61937-1, it is recommended that the pause data-
bursts be transmitted with a repetition period of 64 IEC 60958 frames. The total gap length
shall be a multiple of 192 IEC 60958 frames.
When a stream gap in an MPEG bitstream is filled by a sequence of pause data-bursts, the
Pa of the initial
...