IEC 61937-3:2017
(Main)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
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
IEC 61937-3:2017 is available as IEC 61937-3:2017 RLV which contains the International Standard and its Redline version, showing all changes of the technical content compared to the previous edition.
IEC 61937-3:2017 describes the method used to convey non-linear PCM bitstreams encoded according to the AC-3 and enhanced AC-3 formats. This third edition of IEC 61937-3 cancels and replaces the second edition published in 2007. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous edition:
a) removal of support for enhanced AC-3 bitstreams with a sampling frequency of 32 kHz;
b) updates to normative and informative references;
c) clarification of pause data-burst usage for enhanced AC-3 bitstreams.
General Information
Standards Content (sample)
IEC 61937-3
Edition 3.0 2017-07
INTERNATIONAL
STANDARD
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
IEC 61937-3:2017-07(en)
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IEC 61937-3
Edition 3.0 2017-07
INTERNATIONAL
STANDARD
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
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 33.160.30 ISBN 978-2-8322-4557-6
Warning! Make sure that you obtained this publication from an authorized distributor.
® Registered trademark of the International Electrotechnical Commission---------------------- Page: 3 ----------------------
– 2 – IEC 61937-3:2017 © IEC 2017
CONTENTS
FOREWORD ........................................................................................................................... 3
1 Scope .............................................................................................................................. 5
2 Normative references ...................................................................................................... 5
3 Terms, definitions and abbreviated terms ........................................................................ 5
3.7 Abbreviated terms ................................................................................................... 6
4 Mapping of the audio bitstream on to IEC 61937-1 .......................................................... 6
4.1 General ................................................................................................................... 6
4.2 AC-3 and enhanced AC-3 burst-info ........................................................................ 6
5 Format of AC-3 and enhanced AC-3 data-bursts .............................................................. 7
5.1 General ................................................................................................................... 7
5.2 Pause data-burst .................................................................................................... 7
5.3 Audio data-bursts .................................................................................................... 7
5.3.1 AC-3 data ........................................................................................................ 7
5.3.2 Latency of AC-3 decoding ................................................................................ 8
5.3.3 Enhanced AC-3 data ........................................................................................ 9
5.3.4 Latency of the enhanced AC-3 decoder ......................................................... 11
Bibliography .......................................................................................................................... 13
Figure 1 – AC-3 data-burst, with reference point R.................................................................. 7
Figure 2 – Latency of AC-3 decoding ...................................................................................... 8
Figure 3 – Enhanced AC-3 data-burst ................................................................................... 10
Figure 4 – Latency of enhanced AC-3 decoding .................................................................... 11
Table 1 – Fields of burst-info .................................................................................................. 6
Table 2 – Repetition period of the pause data-bursts .............................................................. 7
Table 3 – Data-type-dependent information when data-type bits 0-4 = 1 ................................ 8
Table 4 – Data-type-dependent information when data-type bits 0-4 = 21 and data-
type bits 5-6 = 0 .................................................................................................................... 10
Table 5 – Maximum enhanced AC-3 burst-payload size and bitstream data rate persampling frequency and IEC 60958 frame rate ...................................................................... 11
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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 and
enhanced AC-3 formats
FOREWORD
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International Standard IEC 61937-3 has been prepared by subcommittee technical area 4:
Digital system interfaces and protocols, of IEC technical committee 100: Audio, video and
multimedia systems and equipment.This third edition of IEC 61937-3 cancels and replaces the second edition published in 2007.
This edition constitutes a technical revision.This edition includes the following significant technical changes with respect to the previous
edition:a) removal of support for enhanced AC-3 bitstreams with a sampling frequency of 32 kHz;
b) updates to normative and informative references;c) clarification of pause data-burst usage for enhanced AC-3 bitstreams.
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The text of this International Standard is based on the following documents:
CDV Report on voting
100/2720/CDV 100/2934/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 parts in the IEC 61973 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.
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IEC 61937-3:2017 © IEC 2017 – 5 –
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
1 Scope
This part of IEC 61937 describes the method used to convey non-linear PCM bitstreams
encoded according to the AC-3 and enhanced AC-3 formats.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 61937-1:2007, Digital audio interface for non-linear PCM encoded audio bit streams
applying IEC 60958 – Part 1: GeneralIEC 61937-1:2007/AMD1:2011, Digital audio interface for non-linear PCM encoded audio bit
streams applying IEC 60958 – Part 1: GeneralIEC 61937-2, Digital audio interface for non-linear PCM encoded audio bit streams applying
IEC 60958 – Part 2: Burst-infoETSI TS 102 366, Digital Audio Compression (AC-3, Enhanced AC-3) Standard
3 Terms, definitions and abbreviated terms
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
block identification flag
flag used to indicate that the first audio block of an enhanced AC-3 syncframe with a stream
type value of two formed the first audio block in the AC-3 syncframe from which it was
converted3.2
converter synchronization flag
flag used for synchronization by a device that converts an enhanced AC-3 bitstream to a
bitstream compliant with an AC-3 decoder and indicates that the first block in this enhanced
AC-3 syncframe will form the first block of the AC-3 syncframe output by the conversion
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3.3
latency
delay time of an external audio decoder to decode an AC-3 or enhanced AC-3 data-burst,
defined as the sum of two values: the receiving delay time and the decoding delay time
3.4stream type
parameter of an enhanced AC-3 syncframe identifying the type of substream of which the
syncframe is a partNote 1 to entry: An enhanced AC-3 bitstream is constructed from one or more substreams, with each substream
being constructed from a sequence of syncframes.3.5
substream identification
parameter of an enhanced AC-3 syncframe which, in conjunction with the stream type
parameter, identifies the substream in the bitstream of which the syncframe is a part
3.6syncframe
minimum portion of the AC-3 or enhanced AC-3 audio serial bitstream capable of being fully
decoded, also known as a synchronization frame3.7 Abbreviated terms
ATSC Advanced Television Systems Committee
ETSI European Telecommunications Standards Institute
4 Mapping of the audio bitstream on to IEC 61937-1
4.1 General
The coding of the bitstream and data-burst is in accordance with IEC 61937-1,
IEC 61937-1:2007/AMD1:2011 and IEC 61937-2, including field names such as "Pc", "Pa" and
"R".4.2 AC-3 and enhanced AC-3 burst-info
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
Bits of Data-type Data-type Contents Reference Repetition period of data-burst measured in
Pc bits 0-4 bits 5-6 point RIEC 60958 frames
0 to 6 1 0 AC-3 R-AC-3 1 536
1 to 3 Reserved
2 to 20 According to IEC 61937
21 0 Enhanced AC-3 Bit 0 of Pa 6 144
1 to 3 According to IEC 61937
22 to 31 According to IEC 61937
7 to 15 According to IEC 61937
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IEC 61937-3:2017 © IEC 2017 – 7 –
5 Format of AC-3 and enhanced AC-3 data-bursts
5.1 General
This clause specifies the audio data-bursts AC-3 and enhanced AC-3. Specific properties
such as reference points, repetition periods, the method of filling stream gaps and decoding
latency are specified.The decoding latency (or delay), indicated for the data-type bits 0-4, 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 AC-3 and enhanced AC-3 are given in Table 2.
Table 2 – Repetition period of the pause data-bursts
Data-type bits 0-4 of audio data-burst Repetition period of pause data-burst
Mandatory Recommended
AC-3 - 3 IEC 60958 frames
Enhanced AC-3 - 4 IEC 60958 frames
5.3 Audio data-bursts
5.3.1 AC-3 data
The AC-3 bitstream consists of a sequence of AC-3 syncframes. The data-type bits 0-4 of an
AC 3 data-burst is 1. An AC-3 syncframe represents 1 536 samples of each encoded audio
channel (left, centre, etc.). The data-burst is headed with a burst-preamble followed by the
burst-payload. The burst-payload of each data-burst of AC-3 data shall c...
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