IEC 61937-10:2017

Digital audio - Interface for non-linear PCM encoded audio bitstreams applying IEC 60958 - Part 10: Non-linear PCM bitstreams according to the MPEG-4 audio lossless coding (ALS) format

IEC 61937-10:2017(E) specifies the method for IEC 60958 to convey non-linear PCM bitstreams encoded in accordance with the MPEG-4 audio lossless coding (ALS) format.
This second edition cancels and replaces the first edition published in 2011. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous edition:
a) Addition of Levels 2, 3, 4 of MPEG-4 ALS Simple Profile;
b) Addition of data-type bits 0-4 and data-type bits 5-6 for MPEG-4 ALS with LATM/LOAS header.

General Information

• Status: Published
• Publication Date: 27-Jul-2017
• ICS: 33.160.30 - Audio systems
• ICS: 35.240.99 - IT applications in other fields
• Technical Committee: TA 20 - Analogue and digital audio
• Drafting Committee: MT 61937-10 - TC 100/MT 61937-10
• Current Stage: PPUB - Publication issued
• Start Date: 28-Jul-2017
• Completion Date: 04-Aug-2017

Relations

• Revises: IEC 61937-10:2011 - Digital audio - Interface for non-linear PCM encoded audio bitstreams applying IEC 60958 - Part 10: Non-linear PCM bitstreams according to the MPEG-4 audio lossless coding (ALS) format
• Effective Date: 05-Sep-2023

Overview

IEC 61937-10:2017 defines how to carry non-linear PCM audio bitstreams encoded with the MPEG‑4 Audio Lossless Coding (ALS) format over the IEC 60958 digital audio interface. Part of the IEC 61937 series, this second edition (2017) is a technical revision that extends support for additional ALS Simple Profile levels and adds metadata handling for LATM/LOAS-wrapped ALS streams. The standard specifies burst mapping, burst-info fields, payload format and timing/latency considerations needed for reliable transport and synchronization.

Key Topics

• Mapping onto IEC 61937: Rules for packaging MPEG‑4 ALS frames into IEC 61937 data-bursts so legacy IEC 60958 interfaces can transport lossless ALS bitstreams.
• Burst‑info (16‑bit field): Definition of the 16‑bit burst-info word including data-type bits 0–4, data-type bits 5–6, an error flag and ALS‑specific fields (multiplier, Simple Profile Level). Table mappings indicate when ALS or LATM/LOAS is used.
• Burst payload format: Normative description of the ALS burst payload and optional LATM/LOAS header handling; includes ALSSpecificConfig and auxiliary data fields required to decode each burst.
• ALS Simple Profile levels: Addition of Levels 2, 3 and 4 to support higher complexity/use cases while retaining Simple Profile restrictions.
• Timing and latency: Guidance on decoder latency, repetition periods of data‑bursts, IEC 60958 frame rates and how to schedule bursts for AV synchronization.
• Constraints and profiles: Limits on channels, sampling rates and word length implied by the ALS Simple Profile (referenced normative limits in the standard).

Applications and Users

Practical applications include:

• Transporting lossless multichannel audio over consumer and professional S/PDIF or AES3 links that implement IEC 60958.
• Interoperability between external decoders, AV receivers, set‑top boxes, DACs and content sources using MPEG‑4 ALS.
• Supporting LATM/LOAS-based multiplexing scenarios where ALS elementary streams are wrapped before transmission.

Who uses this standard:

• Hardware and firmware engineers designing digital audio interfaces and receivers.
• Systems integrators and manufacturers of broadcast, pro‑audio and consumer A/V equipment.
• Test labs and QA teams validating compliance and interoperability of IEC 61937 transports.

Related Standards

• IEC 60958-1 / IEC 60958-3 - Digital audio interface (general and consumer).
• IEC 61937-1 / IEC 61937-2 - General and burst-info rules for IEC 61937 series.
• ISO/IEC 14496-3 (MPEG‑4 Audio) - ALS Simple Profile and LATM/LOAS transport.

Keywords: IEC 61937-10, MPEG‑4 ALS, IEC 60958, digital audio interface, non-linear PCM, LATM/LOAS, burst-info, burst-payload, ALS Simple Profile.

Standards Content (Sample)

IEC 61937-10 ®
Edition 2.0 2017-07
INTERNATIONAL
STANDARD
Digital audio – interface for non-linear PCM encoded audio bitstreams applying
IEC 60958 –
Part 10: Non-linear PCM bitstreams according to the MPEG-4 audio lossless
coding (ALS) format
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IEC 61937-10 ®
Edition 2.0 2017-07
INTERNATIONAL
STANDARD
Digital audio – interface for non-linear PCM encoded audio bitstreams applying

IEC 60958 –
Part 10: Non-linear PCM bitstreams according to the MPEG-4 audio lossless

coding (ALS) format
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 33.160.30; 35.240.99 ISBN 978-2-8322-4560-6

– 2 – IEC 61937-10:2017 © IEC 2017

CONTENTS
FOREWORD . 3
1 Scope . 5
2 Normative references . 5
3 Terms, definitions, abbreviated terms and conventions . 5
3.1 Terms and definitions . 5
3.2 Abbreviated terms . 7
3.3 Presentation convention . 7
4 Mapping of the audio bitstream onto IEC 61937 . 7
4.1 General . 7
4.2 MPEG-4 ALS burst-info . 7
5 Format of MPEG-4 ALS data-bursts . 8
5.1 General . 8
5.2 Audio data-bursts . 9
5.2.1 Data-burst for MPEG-4 ALS . 9
5.2.2 Latency of MPEG-4 ALS decoding . 10
5.2.3 Data-burst for MPEG-4 ALS in LATM/LOAS . 12
Annex A (informative) Effect of repetition period of data-burst and IEC 60958 frame
rate on frame period for the MPEG-4 ALS bitstreams . 13
Annex B (normative) Burst payload format for MPEG-4 ALS . 14
Annex C (normative) Values for ALSSpecificConfig in the MPEG-4 ALS burst payload
format . 15
Annex D (informative) Example use case of the ALS simple profile in LATM/LOAS . 17

Figure 1 – MPEG-4 ALS data-burst . 9
Figure 2 – Latency of MPEG-4 ALS decoding . 11
Figure 3 – The MPEG-4 ALS burst-payload . 11
Figure 4 – MPEG-4 ALS burst-payload with LATM/LOAS header . 12
Figure B.1 – MPEG-4 ALS burst-payload . 14

Table 1 – Fields of burst-info (data-type bits 0-4=23, data-type bits 5-6=0/ data-type
bits 0-4=25, data-type bits 5-6=2) . 8
Table 2 – Sampling frequency, multiplier, and IEC 60958 frame rate . 10
Table A.1 – MPEG-4 ALS payload and frame repetition: some examples . 13
Table C.1 – Recommended values for the ALSSpecificConfig in the MPEG-4 ALS
burst-payload . 15
Table D.1 – MPEG-4 ALS simple profile, maximum payload size and frame repetition:
some examples . 17

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
DIGITAL AUDIO – INTERFACE FOR NON-LINEAR PCM ENCODED
AUDIO BITSTREAMS APPLYING IEC 60958 –

Part 10: Non-linear PCM bitstreams according to the MPEG-4 audio
lossless coding (ALS) format
FOREWORD
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International Standard IEC 61937-10 has been prepared by technical area 4: Digital system
interfaces and protocols, of IEC technical committee 100: Audio, video and multimedia
systems and equipment.
This second edition cancels and replaces the first edition published in 2011. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) Addition of Levels 2, 3, 4 of MPEG-4 ALS Simple Profile;
b) Addition of data-type bits 0-4 and data-type bits 5-6 for MPEG-4 ALS with LATM/LOAS
header.
– 4 – IEC 61937-10:2017 © IEC 2017

The text of this International Standard is based on the following documents:
CDV Report on voting
100/2630/CDV 100/2930/RVC
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all the parts in the IEC 61937 series, published under the general title Digital audio –
Interface for non-linear PCM encoded audio bitstreams applying IEC 60958 can be found on
the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.

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

Part 10: Non-linear PCM bitstreams according to the MPEG-4 audio
lossless coding (ALS) format
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-4 audio lossless coding (ALS) format.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their
content constitutes requirements 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 60958-1, Digital audio interface – Part 1: General
IEC 60958-3, Digital audio interface – Part 3: Consumer applications
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 14496-3:2009, Information technology – Coding of audio-visual objects – Part 3:
Audio
ISO/IEC 14496-3:2009/AMD2:2010, ALS simple profile and transport of SAOC
ISO/IEC 14496-3:2009/AMD5:2015, Support for Dynamic Range Control, New Levels for ALS
Simple Profile, and Audio Synchronization
3 Terms, definitions, abbreviated terms and conventions
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp

3.1.1
als_id
ALS identifier in ALSSpecificConfig

– 6 – IEC 61937-10:2017 © IEC 2017

3.1.2
ALS Simple Profile
MPEG-4 ALS Simple Profile defined by ISO/IEC 14496-3:2009/AMD2:2010 and
ISO/IEC 14496-3:2009/AMD5:2015
3.1.3
aux_data
auxiliary data contained in the MPEG-4 ALS burst payload
Note 1 to entry: Not required for decoding audio samples.
3.1.4
aux_size
size of the auxiliary data field in bytes for MPEG-4 ALS
3.1.5
channels
number of channels-1, 'channels', contained in the MPEG-4 ALS burst payload
3.1.6
latency
delay time of an external audio decoder to decode a MPEG-4 ALS data-burst, defined as the
sum of the receiving delay time and the decoding delay time
3.1.7
length code
code indicating the length of the data-burst-payload in 8-byte units according to this standard
3.1.8
low overhead audio stream
LOAS
synchronisation layer defined by ISO/IEC 14496-3
Note 1 to entry: Three different formats of LOAS are defined, each of which is designed to address the specific
characteristics of the underlying transmission layer. AudioSyncStream shall be used.
3.1.9
low-overhead MPEG-4 audio transport multiplex
LATM
multiplexing layer defined by ISO/IEC 14496-3
Note 1 to entry: LATM is used for multiplexing of audio elementary streams. AudioMuxElement shall be used.
3.1.10
resolution
bit depth of the audio samples contained in the MPEG-4 ALS burst payload
3.1.11
samples
number of audio samples per channel contained in the MPEG-4 ALS burst payload
Note 1 to entry: In contrast to the ALS specification, each data-burst provides its own ALSSpecificConfig. Thus
the 'samples' value refers to the total number of samples (per channel) of that data-burst.
3.1.12
samp_freq
sampling frequency of the audio samples contained in the MPEG-4 ALS burst payload

3.2 Abbreviated terms
ALS audio lossless coding
PCM pulse-code modulation
3.3 Presentation convention
01 Value "01" in binary format
4 Mapping of the audio bitstream onto IEC 61937
4.1 General
The coding of the bitstream and data-burst is in accordance with the IEC 61937 series of
standards.
4.2 MPEG-4 ALS burst-info
The 16-bit burst-info contains information about the data that will be found in the data-burst in
accordance with Table 1.
– 8 – IEC 61937-10:2017 © IEC 2017

Table 1 – Fields of burst-info
(data-type bits 0-4=23, data-type bits 5-6=0/ data-type bits 0-4=25, data-type bits 5-6=2)
Bits of Value Contents Reference Repetition period of
Pc point R data-burst in
IEC 60958 frames
0 to 4 data-type bits 0-4
0-22 In accordance with IEC 61937-2
23 MPEG-4 ALS or other applications according to Bit 0 of Pa See 5.2.1
IEC 61937-2, depending on data-type bits 5-6
24-24 In accordance with IEC 61937-2
25 MPEG-4 ALS or other applications according to Bit 0 of Pa See 5.2.1
IEC 61937-2, depending on data-type bits 5-6
26-31 In accordance with IEC 61937-2
5, 6 data-type bits 5-6 for data-type bits 0-4 23
0 MPEG-4 ALS See 5.2
...