IEC 61937-3:2003

Digital audio - Interface for non-linear PCM encoded audio bitstreams applying IEC 60958 - Part 3: Non-linear PCM bitstreams according to the AC-3 format

specifies the method for the digital audio interface specified in IEC 60958 to convey non-linear PCM bitstreams encoded in accordance with the AC-3 format. The contents of the corrigendum of March 2004 have been included in this copy.

General Information

• Status: Published
• Publication Date: 15-May-2003
• ICS: 33.160.30 - Audio systems
• Technical Committee: TC 100 - Audio, video and multimedia systems and equipment
• Current Stage: DELPUB - Deleted Publication
• Start Date: 07-Nov-2007
• Completion Date: 26-Oct-2025

Relations

• Replaces: IEC 61937:2000 - Digital audio - Interface for non-linear PCM encoded audio bitstreams applying IEC 60958
• Effective Date: 05-Sep-2023
• Corrected By: IEC 61937-3:2003/COR1:2004 - Corrigendum 1 - Digital audio - Interface for non-linear PCM encoded audio bitstreams applying IEC 60958 - Part 3: Non-linear PCM bitstreams according to the AC-3 format
• Effective Date: 05-Sep-2023
• Revised: IEC 61937-3:2007 - Digital audio - Interface for non-linear PCM encoded audio bitstreams applying IEC 60958 - Part 3: Non-linear PCM bitstreams according to the AC-3 and enhanced AC-3 formats
• Effective Date: 05-Sep-2023

Overview

IEC 61937-3:2003 (Digital audio - Interface for non-linear PCM encoded audio bitstreams applying IEC 60958 - Part 3) specifies how AC-3 non-linear PCM bitstreams are mapped and transported over the IEC 60958 digital audio interface. This part defines the burst structure, burst-info fields, pause data-bursts for stream gaps, and decoder latency expectations. The consolidated edition includes the March 2004 corrigendum.

This standard is essential when carrying AC-3 (A/52) encoded streams between consumer and broadcast equipment where the IEC 60958 physical/interface format is used for bitstream transmission.

Key Topics

• Burst-info mapping: A 16-bit burst-info conveys type and metadata for each data-burst. For AC-3 the data-type value is 01h and certain bits of Pc convey AC-3 specific values (for example bsmod bits).

• AC-3 data-burst format: Each AC-3 data-burst contains a burst-preamble followed by a burst-payload that shall include one complete AC-3 frame. An AC-3 frame represents 1 536 samples per encoded audio channel.

• Reference point and timing: The reference point (R-AC-3) for each AC-3 burst is defined as the IEC 60958 frame located two-thirds of the way through the AC-3 payload (rounded to the nearest 32-bit word). Data-bursts of the same bitstream are scheduled so that reference points are separated by 1 536 sampling periods.

• Pause data-bursts and gap handling: The standard specifies recommended repetition periods for pause bursts (recommended: 3 IEC 60958 frames) and guidance on using pause bursts to fill stream gaps. Pause payloads may include a gap-length parameter to assist AC-3 decoders in audio concealment.

• Decoder latency: The AC-3 decoder latency is specified as 1 AC-3 block time (256 PCM samples). At 48 kHz this corresponds to approximately 5.33 ms, and transmitters should account for this when scheduling bursts for sync with video.

Applications

• Transporting AC-3 (Dolby Digital / A/52) bitstreams between source devices, professional encoders/decoders and consumer receivers using the IEC 60958 interface.
• Broadcast and post-production systems that require precise timing, gap concealment and deterministic latency for lip‑sync and multicore audio workflows.
• Consumer AV devices, set‑top boxes and digital audio interfaces where AC-3 must be carried as non-linear PCM bursts.

Related Standards

• IEC 60958 (all parts) - Digital audio interface (physical and framing rules used by IEC 61937 family).
• IEC 61937-1 - General mapping and burst-info conventions for non-linear PCM bitstreams.
• ATSC A/52 (AC-3) and ITU‑R BS.1196‑1 - Specifications for the AC-3 bitstream and coding referenced by this part.

For implementers, follow the burst timing, reference point definition and pause-burst recommendations in IEC 61937-3 to ensure interoperability, predictable latency and robust gap concealment when carrying AC-3 over IEC 60958.

Standards Content (Sample)

INTERNATIONAL IEC
STANDARD
61937-3
First edition
2003-05
Digital audio –
Interface for non-linear PCM encoded
audio bitstreams applying IEC 60958 –
Part 3:
Non-linear PCM bitstreams
according to the AC-3 format
Reference number
Publication numbering
As from 1 January 1997 all IEC publications are issued with a designation in the

60000 series. For example, IEC 34-1 is now referred to as IEC 60034-1.

Consolidated editions
The IEC is now publishing consolidated versions of its publications. For example,

edition numbers 1.0, 1.1 and 1.2 refer, respectively, to the base publication, the

base publication incorporating amendment 1 and the base publication incorporating

amendments 1 and 2.
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INTERNATIONAL IEC
STANDARD
61937-3
First edition
2003-05
Digital audio –
Interface for non-linear PCM encoded
audio bitstreams applying IEC 60958 –
Part 3:
Non-linear PCM bitstreams
according to the AC-3 format
 IEC 2003  Copyright - all rights reserved
No part of this publication may be reproduced or utilized in any form or by any means, electronic or
mechanical, including photocopying and microfilm, without permission in writing from the publisher.
International Electrotechnical Commission, 3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, Switzerland
Telephone: [phone] Telefax: [phone] E-mail: [e-mail]  Web: www.iec.ch
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Commission Electrotechnique Internationale
J
International Electrotechnical Commission
Международная Электротехническая Комиссия
For price, see current catalogue

–  – 61937-3  IEC:2003(E)
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 . 6
4 Mapping of the audio bitstream on to IEC 61937. 6
4.1 AC-3 burst-info . 6
5 Format of AC-3 data-burst . 6
5.1 General . 6
5.2 Pause data-burst . 6
5.3 Audio data-bursts . 6
5.3.1 The data AC-3 . 6
5.3.2 Latency of AC-3 decoding . 7
Bibliography. 9
Figure 1 – AC-3 data-burst, with reference point R. 7
Figure 2 – Latency of AC-3 decoding . 8
Table 1 – Fields of burst-info.6
Table 2 – Repetition period of pause data-bursts . 6
Table 3 – Data-type-dependent when data-type = 1 . 7

61937-3  IEC:2003(E) – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION

____________
DIGITAL AUDIO –
INTERFACE FOR NON-LINEAR PCM ENCODED

AUDIO BITSTREAMS APPLYING IEC 60958 –

Part 3: Non-linear PCM bitstreams according to the AC-3 format

FOREWORD
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all national electrotechnical committees (IEC National Committees). The object of the IEC is to promote
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of patent rights. The IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61937-3 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.

The text of this standard is based on the following documents:
FDIS Report on voting
100/646/FDIS 100/672/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.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

–  – 61937-3  IEC:2003(E)
IEC 61937 consists of the following parts under the general title Digital audio – Interface for
non-linear PCM encoded audio bistreams applying IEC 60958:

Part 1: General
Part 2: Burst-info
Part 3: Non-linear PCM 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 Theatre Systems) format(s)

Part 6: Non-linear PCM bitstreams according to the MPEG-2 AAC format

Part 7: Non-l
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