IEC 61937-7:2004

IEC 61937-7 ®
Edition 2.0 2004-11
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Digital audio – Interface for non-linear PCM encoded audio bitstreams applying
to IEC 60958 –
Part 7: Non-linear PCM bitstreams according to the ATRAC, ATRAC2/3 and
ATRAC-X formats
Audionumérique – Interface pour les flux de bits audio à codage MIC non
linéaire conformément à la CEI 60958 –
Partie 7: Flux de bits MIC non linéaire selon les formats ATRAC, ATRAC2/3 et
ATRAC-X
All rights reserved. Unless otherwise specified, 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
either IEC or IEC's member National Committee in the country of the requester.
If you have any questions about IEC copyright or have an enquiry about obtaining additional rights to this publication,
please contact the address below or your local IEC member National Committee for further information.

Droits de reproduction réservés. Sauf indication contraire, aucune partie de cette publication ne peut être reproduite ni
utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique, y compris la photocopie et les
microfilms, sans l'accord écrit de la CEI ou du Comité national de la CEI du pays du demandeur.
Si vous avez des questions sur le copyright de la CEI ou si vous désirez obtenir des droits supplémentaires sur cette
publication, utilisez les coordonnées ci-après ou contactez le Comité national de la CEI de votre pays de résidence.

IEC Central Office Tel.: +41 22 919 02 11
3, rue de Varembé Fax: +41 22 919 03 00
CH-1211 Geneva 20 info@iec.ch
Switzerland www.iec.ch
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigenda or an amendment might have been published.

Useful links:
IEC publications search - www.iec.ch/searchpub Electropedia - www.electropedia.org
The advanced search enables you to find IEC publications The world's leading online dictionary of electronic and
by a variety of criteria (reference number, text, technical electrical terms containing more than 30 000 terms and
committee,…). definitions in English and French, with equivalent terms in
It also gives information on projects, replaced and additional languages. Also known as the International
withdrawn publications. Electrotechnical Vocabulary (IEV) on-line.

IEC Just Published - webstore.iec.ch/justpublished Customer Service Centre - webstore.iec.ch/csc
Stay up to date on all new IEC publications. Just Published If you wish to give us your feedback on this publication
details all new publications released. Available on-line and or need further assistance, please contact the
also once a month by email. Customer Service Centre: csc@iec.ch.

A propos de la CEI
La Commission Electrotechnique Internationale (CEI) est la première organisation mondiale qui élabore et publie des
Normes internationales pour tout ce qui a trait à l'électricité, à l'électronique et aux technologies apparentées.

A propos des publications CEI
Le contenu technique des publications de la CEI est constamment revu. Veuillez vous assurer que vous possédez
l’édition la plus récente, un corrigendum ou amendement peut avoir été publié.

Liens utiles:
Recherche de publications CEI - www.iec.ch/searchpub Electropedia - www.electropedia.org
La recherche avancée vous permet de trouver des Le premier dictionnaire en ligne au monde de termes
publications CEI en utilisant différents critères (numéro de électroniques et électriques. Il contient plus de 30 000
référence, texte, comité d’études,…). termes et définitions en anglais et en français, ainsi que
Elle donne aussi des informations sur les projets et les les termes équivalents dans les langues additionnelles.
publications remplacées ou retirées. Egalement appelé Vocabulaire Electrotechnique
International (VEI) en ligne.
Just Published CEI - webstore.iec.ch/justpublished
Service Clients - webstore.iec.ch/csc
Restez informé sur les nouvelles publications de la CEI.
Just Published détaille les nouvelles publications parues. Si vous désirez nous donner des commentaires sur
Disponible en ligne et aussi une fois par mois par email. cette publication ou si vous avez des questions
contactez-nous: csc@iec.ch.
IEC 61937-7 ®
Edition 2.0 2004-11
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Digital audio – Interface for non-linear PCM encoded audio bitstreams applying

to IEC 60958 –
Part 7: Non-linear PCM bitstreams according to the ATRAC, ATRAC2/3 and

ATRAC-X formats
Audionumérique – Interface pour les flux de bits audio à codage MIC non

linéaire conformément à la CEI 60958 –

Partie 7: Flux de bits MIC non linéaire selon les formats ATRAC, ATRAC2/3 et

ATRAC-X
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX M
ICS 33.160.01 ISBN 978-2-83220-524-2

– 2 – 61937-7  IEC:2004
CONTENTS
FOREWORD . 3

1 Scope . 5
2 Normative references . 5
3 Terms, definitions and abbreviations . 5
3.1 Definitions . 5
3.2 Abbreviations . 5
4 Mapping of the audio bitstream on to IEC 61937 . 6
4.1 General . 6
4.2 ATRAC, ATRAC2/3 and ATRAC-X burst-info . 6
5 Format of ATRAC, ATRAC2/3 and ATRAC-X data-bursts . 6
5.1 General . 6
5.2 Audio data-bursts . 7
5.2.1 The data ATRAC . 7
5.2.2 Latency of ATRAC decoding . 8
5.2.3 The data ATRAC2/3 . 8
5.2.4 Latency of ATRAC2/3 decoding . 9
5.2.5 The data ATRAC-X . 10
5.2.6 Latency of ATRAC-X decoding . 11

Bibliography . 13

Figure 1 – ATRAC data-burst . 7
Figure 2 – Latency of ATRAC decoding . 8
Figure 3 – ATRAC2/3 data-burst . 9
Figure 4 – Latency of ATRAC2/3 decoding . 10
Figure 5 – ATRAC-X data-burst . 10
Figure 6 – Latency of ATRAC-X decoding . 11

Table 1 – Fields of burst-info . 6
Table 2 – Data-type-dependent information for data-type ATRAC . 7
Table 3 – Data-type-dependent information for data-type ATRAC2/3 . 9
Table 4 – Data-type-dependent information for data-type ATRAC-X . 11

61937-7  IEC:2004 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
DIGITAL AUDIO –
INTERFACE FOR NON-LINEAR PCM ENCODED
AUDIO BITSTREAMS APPLYING IEC 60958 –

Part 7: Non-linear PCM bitstreams according to
the ATRAC, ATRAC2/3 and ATRAC-X 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 61937-7 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 2002. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) In this edition, a new audio data-type of ATRAC-X is added to ATRAC and ATRAC2/3.
b) Specific properties such as reference points, repetition period, the method of filling stream
gaps, and decoding latency are specified for data-type of ATRAC-X.

– 4 – 61937-7  IEC:2004
This bilingual version (2012-12) corresponds to the monolingual English version, published in
2004-11.
The text of this standard is based on the following documents:
CDV Report on voting
100/752/CDV 100/834/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, undert 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 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 format
Part 7: Non-linear PCM bitstreams according to the ATRAC, ATRAC2/3 and ATRAC-X
formats (TA4)
Part 8: Non-linear PCM bitstreams according to the Windows Media Audio Professional
(TA4)
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.
———————
Under consideration.
61937-7  IEC:2004 – 5 –
DIGITAL AUDIO –
INTERFACE FOR NON-LINEAR PCM ENCODED
AUDIO BITSTREAMS APPLYING IEC 60958 –

Part 7: Non-linear PCM bitstreams according to
the ATRAC, ATRAC2/3 and ATRAC-X 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 ATRAC,
ATRAC2/3 and ATRAC-X 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 60958-1, 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
3 Terms, definitions and abbreviations
3.1 Definitions
For the purposes of this document, the definitions given in IEC 61937-1 and IEC 61937-2, as
well as the following, apply.
3.1.1
latency
delay time of an external audio decoder to decode an ATRAC, ATRAC2/3 and ATRAC-X data-
burst, defined as the sum of two values of the receiving delay time and the decoding delay
time
3.2 Abbreviations
ATRAC Adaptive TRansform Acoustic Coding
ATRAC2 Adaptive TRansform Acoustic Coding 2
ATRAC3 Adaptive TRansform Acoustic Coding 3
ATRAC2/3 ATRAC2 and/or ATRAC3
ATRAC-X Adaptive TRansform Acoustic Coding-X

– 6 – 61937-7  IEC:2004
4 Mapping of the audio bitstream on to IEC 61937
4.1 General
The coding of the bitstream and data-burst shall be in accordance with IEC 61937-1 and
IEC 61937-2.
4.2 ATRAC, ATRAC2/3 and ATRAC-X burst-info
This 16-bit burst-info shall contain data-burst information structured in accordance with
Table 1.
Table 1 – Fields of burst-info
Repetition period
Reference point
Bits of Pc Value Contents of data-burst in
R
IEC 60958 frames
0-4 data-type
0-13 in accordance with IEC 61937-1 and
IEC 61937-2
14 ATRAC bit 0 of Pa 512
15 ATRAC2/3 bit 0 of Pa 1 024
16 ATRAC-X Sub-data-type Sub-data-type
dependent dependent
17-31 in accordance with IEC 61937-2
5, 6 00 Reserved in ATRAC and ATRAC2/3
formats
00 Sub-data-type for ATRAC-X bit 0 of Pa 2 048
01 , 10 , 11 Reserved for sub-data-type in ATRAC-X
2 2 2
7-15 in accordance with IEC 61937-1 and
IEC 61937-2
5 Format of ATRAC, ATRAC2/3 and ATRAC-X data-bursts
5.1 General
This clause specifies the audio data-bursts ATRAC, ATRAC2/3 and ATRAC-X. Specific
properties such as reference points, repetition period, the method of filling stream gaps, and
decoding latency are specified for each data-type of ATRAC, ATRAC2/3 and ATRAC-X.
The decoding latency (or delay), indicated for the data-types, shall be used by the transmitter
to schedule data-bursts as necessary to establish synchronization between the picture and
the decoded audio.
NOTE For ATRAC, ATRAC2/3 and ATRAC-X formats, the recommended repetition value period of pause data-
bursts is 32 IEC 60958 frames.

61937-7  IEC:2004 – 7 –
5.2 Audio data-bursts
5.2.1 The data ATRAC
The ATRAC bitstream consists of sequences of ATRAC frames. The data-type of an ATRAC
data-burst is 0Eh. The data-burst is headed with a burst-preamble, followed by the burst-
payload, and is stuffed with stuffing bits (see Figure 1). The burst-payload of each data-burst
of ATRAC data shall contain one complete ATRAC frame, and represents 512 samples for
each encoded channel. The length of the ATRAC data-burst depends on the encoded bit rate
(which determines the ATRAC-frame length).
NOTE The reference to the specification for the ATRAC bitstream, representing 512 samples of encoded audio
per frame, may be found in the bibliography.

Pa Pb Pc Pd ATRAC Pa Pb Pc Pd ATRAC
Burst_payload Burst_payload
Bit 0 of Pa Bit 0 of Pa
Stuffing ATRAC frame
ATRAC frame
Regular rate of ATRAC frames
Repetition period of the burst
IEC  1525/04
Figure 1 – ATRAC data-burst
The data-type-dependent information for ATRAC is given in Table 2.
Table 2 – Data-type-dependent information for data-type ATRAC
Bits of Pc Data type dependent, Contents
bit number
LSB.MSB LSB.MSB
8-12 00h – 1Fh reserved, shall be set to ‘0’

The reference point of an ATRAC data-burst is bit 0 of Pa and shall occur exactly once every
512 sampling periods. The data-burst containing ATRAC frames shall occur at a regular rate,
with the reference point of each ATRAC data-burst beginning 512 IEC 60958 frames after the
reference point of the preceding ATRAC data-burst (of the same bit-stream-number).
NOTE 1 It is recommended that Pause data-bursts are used to fill stream gaps in the ATRAC bit stream as
described in IEC 61937-1, 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 61937-1).
When a stream gap in an ATRAC stream is filled by a sequence of Pause data-bursts, the Pa
of the first Pause data-burst shall be located 512 sampling periods following the Pa of the
previous ATRAC frame.
NOTE 2 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 considering the 32 IEC 60958 frame length of the Pause data-burst) the
Pa of the first ATRAC data-burst which follows the stream gap.
The gap-length parameter contained in the Pause data-burst is intended to be interpreted by
the ATRAC decoder as an indication of the number of decoded PCM samples which are
missing (due to the resulting audio gap).

– 8 – 61937-7  IEC:2004
5.2.2 Latency of ATRAC decoding
The latency of an external audio decoder to decode ATRAC is defined as the sum of the
receiving delay time and the decoding delay time, as illustrated in Figure 2.

Pa Pb Pc Pd ATRAC Pa Pb Pc Pd ATRAC
Burst_payload Burst_payload
Bit 0 of Pa Bit 0 of Pa
Stuffing ATRAC frame
ATRAC frame
Repetition period of the burst
Receiving delay Decoding delay
Latency of ATRAC decoder
IEC  1526/04
Figure 2 – Latency of ATRAC decoding
EXAMPLE The receiving delay time to receive a whole data-burst is calculated as follows.
The length of preamble is 64 bits. If each ATRAC frame consists of 1 696 B (eight channels of
146,08 kbit/s per channel), the length of the whole data burst-payload is 13 568 bits. In this
case, the whole length of the data burst is 13 632 bits. The receiving delay time is calculated
as 9,66 ms with 44,1 kHz sampling frequency. The decoding delay time is calculated as
11,61 ms, and is equal to the decoding time for one ATRAC frame data. Hence, the latency of
ATRAC decoding is approximately 21,27 ms in this case.
The absolute maximum decoding latency is taken when ATRAC burst-payload extends to just
before the Pa of the next frame and is equal to 23,22 ms at 44,1 kHz sampling frequency.
5.2.3 The data ATRAC2/3
The ATRAC2/3 bitstream consists of sequences of ATRAC2/3 frames. The data-type of an
ATRAC2/3 data-burst is 0Fh. The data-burst is headed with a burst-preamble, followed by the
burst-payload, and stuffed with stuffing bits (see Figure 3). The burst-payload of each data-
burst of ATRAC2/3 data shall contain one complete ATRAC2/3 frame, and represents 1 024
samples for each encoded channels. The length of the ATRAC2/3 data-burst depends on the
encoded bit rate (which determines the ATRAC2/3-frame length).
NOTE The reference to the specification for the ATRAC2/3 bitstream, representing 1 024 samples of encoded
audio per frame, may be found in the bibliography.

61937-7  IEC:2004 – 9 –
Pa Pb Pc Pd ATRAC2/3 Pa Pb Pc Pd ATRAC2/3
Burst_payload Burst_payload
Bit 0 of Pa Bit 0 of Pa
Stuffing ATRAC2/3 frame
ATRAC2/3 frame
Regular rate of ATRAC2/3 frames
Repetition period of the burst
IEC  1527/04
Figure 3 – ATRAC2/3 data-burst
The data-type-dependent information for ATRAC2/3 is given in Table 3.
Table 3 – Data-type-dependent information for data-type ATRAC2/3
Data type dependent
Bits of Pc bit number Contents
LSB.MSB LSB.MSB
8-12 00h ATRAC2
01h ATRAC3
02h-1Fh reserved, shall be set to ‘0’

The reference point of an ATRAC2/3 data-burst is bit 0 of Pa and shall occur exactly once
every 1 024 sampling periods. The data-burst containing ATRAC2/3 frames shall occur at a
regular rate, with the reference point of each ATRAC2/3 data-burst beginning 1 024
IEC 60958 frames after the reference point of the preceding ATRAC2/3 data-burst (of the
same bit-stream-number).
NOTE 1 It is recommended that Pause data-bursts are used to fill stream gaps in the ATRAC2/3 bit stream as
described in IEC 61937-1, 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 61937-1).
When a stream gap in an ATRAC2/3 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 ATRAC2/3 frame.
NOTE 2 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 considering the 32 IEC 60958 frame length of the Pause data-burst) the
Pa of the first ATRAC2/3 data-burst which follows the stream gap.
The gap-length parameter contained in the Pause data-burst is intended to be interpreted by
the ATRAC2/3 decoder as an indication of the number of decoded PCM samples which are
missing (due to the resulting audio gap).
5.2.4 Latency of ATRAC2/3 decoding
The latency of an external audio decoder to decode ATRAC2/3 is defined as the sum of the
receiving delay time and the decoding delay time (see Figure 4).

– 10 – 61937-7  IEC:2004
Pa Pb Pc Pd ATRAC2/3 Pa Pb Pc Pd ATRAC2/3
Burst_payload Burst_payload
Bit 0 of Pa Bit 0 of Pa
Stuffing ATRAC2/3 frame
ATRAC2/3 frame
Repetition period of the burst
Receiving delay Decoding delay
Latency of ATRAC2/3 decoder
IEC  1528/04
Figure 4 – Latency of ATRAC2/3 decoding
EXAMPLE The receiving delay time to receive a whole data-burst is calculated as follows.
The length of preamble is 64 bits. If, for example, each ATRAC2/3 frame consists of 1 696 B
(Eight channels of 73,04 kbit/s per channel), the length of the whole data burst-payload is 13
568 bits. In this case, the whole length of data burst is 13 632 bits. The receiving delay time is
calculated as 9,66 ms with 44,1 kHz sampling frequency. The decoding delay time is
calculated as 23,22 ms, and is equal to the decoding time for one ATRAC2/3 frame data.
Hence, the latency of ATRAC2/3 decoding is approximately 32,88 ms in this case.
The absolute maximum decoding latency is taken when ATRAC2/3 burst-payload extends to
just before the Pa of the next frame, and is equal to 46,44 ms at 44,1 kHz sampling frequency.
5.2.5 The data ATRAC-X
The ATRAC-X bitstream consists of sequences of ATRAC-X frames. The data-type of an
ATRAC-X data-burst is 10 h. The data-burst is headed with a burst-preamble, followed by the
burst-payload, and is stuffed with stuffing bits (see Figure 5). The burst-payload of each data-
burst of ATRAC-X data shall contain one complete ATRAC-X frame, and represents 2 048
samples for each encoded channel. The length of the ATRAC-X data-burst depends on the
encoded bit rate (which determines the ATRAC-X-frame length).
NOTE The reference to the specification for the ATRAC-X bitstream, representing 2 048 samples of encoded
audio per frame, may be found in the bibliography.

Pa Pb Pc Pd ATRAC-X Pa Pb Pc Pd ATRAC-X
Burst_payload Burst_payload
Bit 0 of Pa Bit 0 of Pa
Stuffing ATRAC-X frame
ATRAC-X frame
Regular rate of ATRAC-X frames
Repetition period of the burst
IEC  1529/04
Figure 5 – ATRAC-X data-burst
The data-type-dependent information for ATRAC-X is given in Table 4.

61937-7  IEC:2004 – 11 –
Table 4 – Data-type-dependent information for data-type ATRAC-X
Bits of Pc Data type dependent, Contents
bit number
LSB.MSB LSB.MSB
8-12 00h – 1Fh reserved, shall be set to ‘0’

The reference point of an ATRAC-X data-burst is bit 0 of Pa and shall occur exactly once
every 2 048 sampling periods. The data-burst containing ATRAC-X frames shall occur at a
regular rate, with the reference point of each ATRAC-X data-burst beginning 2 048 IEC 60958
frames after the reference point of the preceding ATRAC-X data-burst (of the same bit-
stream-number).
NOTE 1 It is recommended that Pause data-bursts are used to fill stream gaps in the ATRAC-X bit stream as
described in IEC 61937-1, 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 61937-1).
When a stream gap in an ATRAC-X stream is filled by a sequence of Pause data-bursts, the
Pa of the first Pause data-burst shall be located 2 048 sampling periods following the Pa of
the previous ATRAC-X frame.
NOTE 2 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 considering the 32 IEC 60958 frame length of the Pause data-burst) the
Pa of the first ATRAC-X data-burst which follows the stream gap.
The gap-length parameter contained in the Pause data-burst is intended to be interpreted by
the ATRAC-X decoder as an indication of the number of decoded PCM samples which are
missing (due to the resulting audio gap).
5.2.6 Latency of ATRAC-X decoding
The latency of an external audio decoder to decode ATRAC-X is defined as the sum of the
receiving delay time and the decoding delay time (see Figure 6).

Pa Pb Pc Pd ATRAC-X Pa Pb Pc Pd ATRAC-X
Burst_payload Burst_payload
Bit 0 of Pa Bit 0 of Pa
Stuffing ATRAC-X frame
ATRAC-X frame
Repetition period of the burst
Receiving delay Decoding delay
Latency of ATRAC-X decoder
IEC  1530/04
Figure 6 – Latency of ATRAC-X decoding
EXAMPLE The receiving delay time to receive a whole data-burst is calculated as follows.
The length of preamble is 64 bits. If each ATRAC-X frame consists of maximum bit rate of
352,8 kbit/s, the maximum length of the whole data burst-payload is 16 384 bits. In this case,
the whole length of the data burst is 16 448 bits. The receiving delay time is calculated as
11,66 ms with 44,1 kHz sampling frequency. The decoding delay time is calculated as

– 12 – 61937-7  IEC:2004
46,44 ms, and is equal to the decoding time for one ATRAC-X frame data. Hence, the latency
of ATRAC-X decoding is approximately 58,10 ms in this case.
The absolute maximum decoding latency is taken when ATRAC-X burst-payload extends to
just before the Pa of the next frame and is equal to 92,88 ms at 44,1 kHz sampling frequency.

61937-7  IEC:2004 – 13 –
Bibliography
...

IEC 61937-7 ®
Edition 2.1 2016-05
CONSOLIDATED VERSION
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Digital audio – Interface for non-linear PCM encoded audio bitstreams applying
to IEC 60958 –
Part 7: Non-linear PCM bitstreams according to the ATRAC, ATRAC2/3 and
ATRAC-X formats
Audionumérique – Interface pour les flux de bits audio à codage MIC non
linéaire conformément à l’IEC 60958 –
Partie 7: Flux de bits MIC non linéaire selon les formats ATRAC, ATRAC2/3 et
ATRAC-X
All rights reserved. Unless otherwise specified, 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
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or
your local IEC member National Committee for further information.

Droits de reproduction réservés. Sauf indication contraire, aucune partie de cette publication ne peut être reproduite
ni utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique, y compris la photocopie
et les microfilms, sans l'accord écrit de l'IEC ou du Comité national de l'IEC du pays du demandeur. Si vous avez des
questions sur le copyright de l'IEC ou si vous désirez obtenir des droits supplémentaires sur cette publication, utilisez
les coordonnées ci-après ou contactez le Comité national de l'IEC de votre pays de résidence.

IEC Central Office Tel.: +41 22 919 02 11
3, rue de Varembé Fax: +41 22 919 03 00
CH-1211 Geneva 20 info@iec.ch
Switzerland www.iec.ch
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigenda or an amendment might have been published.

IEC Catalogue - webstore.iec.ch/catalogue Electropedia - www.electropedia.org
The stand-alone application for consulting the entire The world's leading online dictionary of electronic and
bibliographical information on IEC International Standards, electrical terms containing 20 000 terms and definitions in
Technical Specifications, Technical Reports and other English and French, with equivalent terms in 15 additional
documents. Available for PC, Mac OS, Android Tablets and languages. Also known as the International Electrotechnical
iPad. Vocabulary (IEV) online.

IEC publications search - www.iec.ch/searchpub IEC Glossary - std.iec.ch/glossary
The advanced search enables to find IEC publications by a 65 000 electrotechnical terminology entries in English and
variety of criteria (reference number, text, technical French extracted from the Terms and Definitions clause of
committee,…). It also gives information on projects, replaced IEC publications issued since 2002. Some entries have been
and withdrawn publications. collected from earlier publications of IEC TC 37, 77, 86 and

CISPR.
IEC Just Published - webstore.iec.ch/justpublished

Stay up to date on all new IEC publications. Just Published IEC Customer Service Centre - webstore.iec.ch/csc
details all new publications released. Available online and If you wish to give us your feedback on this publication or
also once a month by email. need further assistance, please contact the Customer Service
Centre: csc@iec.ch.
A propos de l'IEC
La Commission Electrotechnique Internationale (IEC) est la première organisation mondiale qui élabore et publie des
Normes internationales pour tout ce qui a trait à l'électricité, à l'électronique et aux technologies apparentées.

A propos des publications IEC
Le contenu technique des publications IEC est constamment revu. Veuillez vous assurer que vous possédez l’édition la
plus récente, un corrigendum ou amendement peut avoir été publié.

Catalogue IEC - webstore.iec.ch/catalogue Electropedia - www.electropedia.org
Application autonome pour consulter tous les renseignements
Le premier dictionnaire en ligne de termes électroniques et
bibliographiques sur les Normes internationales,
électriques. Il contient 20 000 termes et définitions en anglais
Spécifications techniques, Rapports techniques et autres
et en français, ainsi que les termes équivalents dans 15
documents de l'IEC. Disponible pour PC, Mac OS, tablettes
langues additionnelles. Egalement appelé Vocabulaire
Android et iPad.
Electrotechnique International (IEV) en ligne.

Recherche de publications IEC - www.iec.ch/searchpub
Glossaire IEC - std.iec.ch/glossary
La recherche avancée permet de trouver des publications IEC
65 000 entrées terminologiques électrotechniques, en anglais
en utilisant différents critères (numéro de référence, texte,
et en français, extraites des articles Termes et Définitions des
comité d’études,…). Elle donne aussi des informations sur les
publications IEC parues depuis 2002. Plus certaines entrées
projets et les publications remplacées ou retirées.
antérieures extraites des publications des CE 37, 77, 86 et

CISPR de l'IEC.
IEC Just Published - webstore.iec.ch/justpublished

Restez informé sur les nouvelles publications IEC. Just Service Clients - webstore.iec.ch/csc
Published détaille les nouvelles publications parues. Si vous désirez nous donner des commentaires sur cette
Disponible en ligne et aussi une fois par mois par email. publication ou si vous avez des questions contactez-nous:
csc@iec.ch.
IEC 61937-7 ®
Edition 2.1 2016-05
CONSOLIDATED VERSION
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Digital audio – Interface for non-linear PCM encoded audio bitstreams applying

to IEC 60958 –
Part 7: Non-linear PCM bitstreams according to the ATRAC, ATRAC2/3 and

ATRAC-X formats
Audionumérique – Interface pour les flux de bits audio à codage MIC non

linéaire conformément à l’IEC 60958 –

Partie 7: Flux de bits MIC non linéaire selon les formats ATRAC, ATRAC2/3 et

ATRAC-X
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 33.160.01 ISBN 978-2-8322-3415-0

IEC 61937-7 ®
Edition 2.1 2016-05
CONSOLIDATED VERSION
REDLINE VERSION
VERSION REDLINE
colour
inside
Digital audio – Interface for non-linear PCM encoded audio bitstreams applying
to IEC 60958 –
Part 7: Non-linear PCM bitstreams according to the ATRAC, ATRAC2/3 and
ATRAC-X formats
Audionumérique – Interface pour les flux de bits audio à codage MIC non
linéaire conformément à l’IEC 60958 –
Partie 7: Flux de bits MIC non linéaire selon les formats ATRAC, ATRAC2/3 et
ATRAC-X
– 2 – IEC 61937-7:2004+AMD1:2016 CSV
 IEC 2016
CONTENTS
FOREWORD. 3
INTRODUCTION to Amendment 1 . 5
1 Scope . 6
2 Normative references . 6
3 Terms, definitions and abbreviations . 6
3.1 Definitions . 6
3.2 Abbreviations . 6
4 Mapping of the audio bitstream on to IEC 61937 . 7
4.1 General . 7
4.2 ATRAC, ATRAC2/3 and ATRAC-X burst-info . 7
5 Format of ATRAC, ATRAC2/3 and ATRAC-X data-bursts . 7
5.1 General . 7
5.2 Audio data-bursts . 7
5.2.1 The data ATRAC . 7
5.2.2 Latency of ATRAC decoding . 8
5.2.3 The data ATRAC2/3 . 9
5.2.4 Latency of ATRAC2/3 decoding . 10
5.2.5 The data ATRAC-X . 11
5.2.6 Latency of ATRAC-X decoding . 12
Bibliography . 14

Figure 1 – ATRAC data-burst . 8
Figure 2 – Latency of ATRAC decoding . 9
Figure 3 – ATRAC2/3 data-burst . 9
Figure 4 – Latency of ATRAC2/3 decoding . 10
Figure 5 – ATRAC-X data-burst . 11
Figure 6 – Latency of ATRAC-X decoding . 12

Table 1 – Fields of burst-info . 7
Table 2 – Data-type-dependent information for data-type ATRAC. 8
Table 3 – Data-type-dependent information for data-type ATRAC2/3 . 10
Table 4 – Data-type-dependent information for data-type ATRAC-X . 11

 IEC 2016
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
DIGITAL AUDIO –
INTERFACE FOR NON-LINEAR PCM ENCODED
AUDIO BITSTREAMS APPLYING IEC 60958 –
Part 7: Non-linear PCM bitstreams according to
the ATRAC, ATRAC2/3 and ATRAC-X 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 itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
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.
This consolidated version of the official IEC Standard and its amendment has been prepared
for user convenience.
IEC 61937-7 edition 2.1 contains the second edition (2004-11) [documents 100/752/CDV and
100/834/RVC] and its amendment 1 (2016-05) [documents 100/2503/CDV and 100/2614/RVC].
In this Redline version, a vertical line in the margin shows where the technical content is
modified by amendment 1. Additions are in green text, deletions are in strikethrough red text.
A separate Final version with all changes accepted is available in this publication.

– 4 – IEC 61937-7:2004+AMD1:2016 CSV
 IEC 2016
International Standard IEC 61937-7 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 edition includes the following significant technical changes with respect to the previous
edition:
a) In this edition, a new audio data-type of ATRAC-X is added to ATRAC and ATRAC2/3.
b) Specific properties such as reference points, repetition period, the method of filling stream
gaps, and decoding latency are specified for data-type of ATRAC-X.
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, undert 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 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 format
Part 7: Non-linear PCM bitstreams according to the ATRAC, ATRAC2/3 and ATRAC-X
formats (TA4)
Part 8: Non-linear PCM bitstreams according to the Windows Media Audio Professional
(TA4)
The committee has decided that the contents of the base publication and its amendment will
remain unchanged until the stability 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.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
———————
Under consideration.
 IEC 2016
INTRODUCTION to Amendment 1
The revision of IEC 61937-7:2004 has become necessary to specify the new additional
subdata-types of ATRAC-X low latency. This amendment includes the following technical
changes:
a) new three subdata-types of ATRAC-X low latency are defined;
b) specific properties such as reference points, repetition period, and decoding latency are
specified for each subdata-type of ATRAC-X.

– 6 – IEC 61937-7:2004+AMD1:2016 CSV
 IEC 2016
DIGITAL AUDIO –
INTERFACE FOR NON-LINEAR PCM ENCODED
AUDIO BITSTREAMS APPLYING IEC 60958 –

Part 7: Non-linear PCM bitstreams according to
the ATRAC, ATRAC2/3 and ATRAC-X 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 ATRAC,
ATRAC2/3 and ATRAC-X 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 60958-1, 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
3 Terms, definitions and abbreviations
3.1 Definitions
For the purposes of this document, the definitions given in IEC 61937-1 and IEC 61937-2, as
well as the following, apply.
3.1.1
latency
delay time of an external audio decoder to decode an ATRAC, ATRAC2/3 and ATRAC-X data-
burst, defined as the sum of two values of the receiving delay time and the decoding delay
time
3.2 Abbreviations
ATRAC Adaptive TRansform Acoustic Coding
ATRAC2 Adaptive TRansform Acoustic Coding 2
ATRAC3 Adaptive TRansform Acoustic Coding 3
ATRAC2/3 ATRAC2 and/or ATRAC3
ATRAC-X Adaptive TRansform Acoustic Coding-X

© IEC 2016
4 Mapping of the audio bitstream on to IEC 61937
4.1 General
The coding of the bitstream and data-burst shall be in accordance with IEC 61937-1 and
IEC 61937-2.
4.2 ATRAC, ATRAC2/3 and ATRAC-X burst-info
This 16-bit burst-info shall contain data-burst information structured in accordance with
Table 1.
Table 1 – Fields of burst-info
Repetition period
Bits of Reference
Value Contents of data-burst in
Pc point R
IEC 60958 frames
0-4 Data-type
0-13 In accordance with IEC 61937-1 and IEC 61937-2
14 ATRAC bit 0 of Pa 512
15 ATRAC2/3 bit 0 of Pa 1 024
16 ATRAC-X Subdata-type Subdata-type
dependent dependent
17-31 In accordance with IEC 61937-2

5, 6 00 Reserved in ATRAC and ATRAC2/3 formats
00 Subdata-type for ATRAC-X bit 0 of Pa 2 048
01 , 10 , Reserved for sub-data-type in ATRAC-X
2 2
01 Subdata-type for ATRAC-X low latency bit 0 of Pa 512
10 Subdata-type for ATRAC-X low latency bit 0 of Pa 256
Subdata-type for ATRAC-X low latency bit 0 of Pa 128
7-15 In accordance with IEC 61937-1 and IEC 61937-2

5 Format of ATRAC, ATRAC2/3 and ATRAC-X data-bursts
5.1 General
This clause specifies the audio data-bursts ATRAC, ATRAC2/3 and ATRAC-X. Specific
properties such as reference points, repetition period, the method of filling stream gaps, and
decoding latency are specified for each data-type of ATRAC, ATRAC2/3 and ATRAC-X.
The decoding latency (or delay), indicated for the data-types, shall be used by the transmitter
to schedule data-bursts as necessary to establish synchronization between the picture and
the decoded audio.
NOTE For ATRAC, ATRAC2/3 and ATRAC-X formats, the recommended repetition value period of pause data-
bursts is 32 IEC 60958 frames.
5.2 Audio data-bursts
5.2.1 The data ATRAC
The ATRAC bitstream consists of sequences of ATRAC frames. The data-type of an ATRAC
data-burst is 0Eh. The data-burst is headed with a burst-preamble, followed by the burst-
payload, and is stuffed with stuffing bits (see Figure 1). The burst-payload of each data-burst

– 8 – IEC 61937-7:2004+AMD1:2016 CSV
 IEC 2016
of ATRAC data shall contain one complete ATRAC frame, and represents 512 samples for
each encoded channel. The length of the ATRAC data-burst depends on the encoded bit rate
(which determines the ATRAC-frame length).
NOTE The reference to the specification for the ATRAC bitstream, representing 512 samples of encoded audio
per frame, may be found in the bibliography.

Pa Pb Pc Pd ATRAC Pa Pb Pc Pd ATRAC
Burst_payload Burst_payload
Bit 0 of Pa Bit 0 of Pa
Stuffing ATRAC frame
ATRAC frame
Regular rate of ATRAC frames
Repetition period of the burst
IEC  1525/04
Figure 1 – ATRAC data-burst
The data-type-dependent information for ATRAC is given in Table 2.
Table 2 – Data-type-dependent information for data-type ATRAC
Bits of Pc Data type dependent, Contents
bit number
LSB.MSB LSB.MSB
8-12 00h – 1Fh reserved, shall be set to ‘0’

The reference point of an ATRAC data-burst is bit 0 of Pa and shall occur exactly once every
512 sampling periods. The data-burst containing ATRAC frames shall occur at a regular rate,
with the reference point of each ATRAC data-burst beginning 512 IEC 60958 frames after the
reference point of the preceding ATRAC data-burst (of the same bit-stream-number).
NOTE 1 It is recommended that Pause data-bursts are used to fill stream gaps in the ATRAC bit stream as
described in IEC 61937-1, 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 61937-1).
When a stream gap in an ATRAC stream is filled by a sequence of Pause data-bursts, the Pa
of the first Pause data-burst shall be located 512 sampling periods following the Pa of the
previous ATRAC frame.
NOTE 2 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 considering the 32 IEC 60958 frame length of the Pause data-burst) the
Pa of the first ATRAC data-burst which follows the stream gap.
The gap-length parameter contained in the Pause data-burst is intended to be interpreted by
the ATRAC 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 ATRAC decoding
The latency of an external audio decoder to decode ATRAC is defined as the sum of the
receiving delay time and the decoding delay time, as illustrated in Figure 2.

 IEC 2016
Pa Pb Pc Pd ATRAC Pa Pb Pc Pd ATRAC
Burst_payload Burst_payload
Bit 0 of Pa Bit 0 of Pa
Stuffing ATRAC frame
ATRAC frame
Repetition period of the burst
Receiving delay Decoding delay
Latency of ATRAC decoder
IEC  1526/04
Figure 2 – Latency of ATRAC decoding
EXAMPLE The receiving delay time to receive a whole data-burst is calculated as follows.
The length of preamble is 64 bits. If each ATRAC frame consists of 1 696 B (eight channels of
146,08 kbit/s per channel), the length of the whole data burst-payload is 13 568 bits. In this
case, the whole length of the data burst is 13 632 bits. The receiving delay time is calculated
as 9,66 ms with 44,1 kHz sampling frequency. The decoding delay time is calculated as
11,61 ms, and is equal to the decoding time for one ATRAC frame data. Hence, the latency of
ATRAC decoding is approximately 21,27 ms in this case.
The absolute maximum decoding latency is taken when ATRAC burst-payload extends to just
before the Pa of the next frame and is equal to 23,22 ms at 44,1 kHz sampling frequency.
5.2.3 The data ATRAC2/3
The ATRAC2/3 bitstream consists of sequences of ATRAC2/3 frames. The data-type of an
ATRAC2/3 data-burst is 0Fh. The data-burst is headed with a burst-preamble, followed by the
burst-payload, and stuffed with stuffing bits (see Figure 3). The burst-payload of each data-
burst of ATRAC2/3 data shall contain one complete ATRAC2/3 frame, and represents 1 024
samples for each encoded channels. The length of the ATRAC2/3 data-burst depends on the
encoded bit rate (which determines the ATRAC2/3-frame length).
NOTE The reference to the specification for the ATRAC2/3 bitstream, representing 1 024 samples of encoded
audio per frame, may be found in the bibliography.

Pb Pc Pd
Pa Pb Pc Pd ATRAC2/3 Pa ATRAC2/3
Burst_payload Burst_payload
Bit 0 of Pa Bit 0 of Pa
Stuffing ATRAC2/3 frame
ATRAC2/3 frame
Regular rate of ATRAC2/3 frames
Repetition period of the burst
IEC  1527/04
Figure 3 – ATRAC2/3 data-burst

– 10 – IEC 61937-7:2004+AMD1:2016 CSV
 IEC 2016
The data-type-dependent information for ATRAC2/3 is given in Table 3.
Table 3 – Data-type-dependent information for data-type ATRAC2/3
Data type dependent
Bits of Pc bit number Contents
LSB.MSB LSB.MSB
8-12 00h ATRAC2
01h ATRAC3
02h-1Fh reserved, shall be set to ‘0’

The reference point of an ATRAC2/3 data-burst is bit 0 of Pa and shall occur exactly once
every 1 024 sampling periods. The data-burst containing ATRAC2/3 frames shall occur at a
regular rate, with the reference point of each ATRAC2/3 data-burst beginning 1 024
IEC 60958 frames after the reference point of the preceding ATRAC2/3 data-burst (of the
same bit-stream-number).
NOTE 1 It is recommended that Pause data-bursts are used to fill stream gaps in the ATRAC2/3 bit stream as
described in IEC 61937-1, 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 61937-1).
When a stream gap in an ATRAC2/3 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 ATRAC2/3 frame.
NOTE 2 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 considering the 32 IEC 60958 frame length of the Pause data-burst) the
Pa of the first ATRAC2/3 data-burst which follows the stream gap.
The gap-length parameter contained in the Pause data-burst is intended to be interpreted by
the ATRAC2/3 decoder as an indication of the number of decoded PCM samples which are
missing (due to the resulting audio gap).
5.2.4 Latency of ATRAC2/3 decoding
The latency of an external audio decoder to decode ATRAC2/3 is defined as the sum of the
receiving delay time and the decoding delay time (see Figure 4).

Pb Pc Pd
Pa Pb Pc Pd ATRAC2/3 Pa ATRAC2/3
Burst_payload Burst_payload
Bit 0 of Pa Bit 0 of Pa
Stuffing ATRAC2/3 frame
ATRAC2/3 frame
Repetition period of the burst
Receiving delay Decoding delay
Latency of ATRAC2/3 decoder
IEC  1528/04
Figure 4 – Latency of ATRAC2/3 decoding
EXAMPLE The receiving delay time to receive a whole data-burst is calculated as follows.
The length of preamble is 64 bits. If, for example, each ATRAC2/3 frame consists of 1 696 B
(Eight channels of 73,04 kbit/s per channel), the length of the whole data burst-payload is 13

 IEC 2016
568 bits. In this case, the whole length of data burst is 13 632 bits. The receiving delay time is
calculated as 9,66 ms with 44,1 kHz sampling frequency. The decoding delay time is
calculated as 23,22 ms, and is equal to the decoding time for one ATRAC2/3 frame data.
Hence, the latency of ATRAC2/3 decoding is approximately 32,88 ms in this case.
The absolute maximum decoding latency is taken when ATRAC2/3 burst-payload extends to
just before the Pa of the next frame, and is equal to 46,44 ms at 44,1 kHz sampling frequency.
5.2.5 The data ATRAC-X
The ATRAC-X bitstream consists of sequences of ATRAC-X frames. The data-type of an
ATRAC-X data-burst is 10 h. The data-burst is headed with a burst-preamble, followed by the
burst-payload, and is stuffed with stuffing bits (see Figure 5). The burst-payload of each data-
burst of ATRAC-X data shall contain one complete ATRAC-X frame, and represents 2 048,
512, 256 or 128 samples for each encoded channel. The length of the ATRAC-X data-burst
depends on the encoded bit rate (which determines the ATRAC-X-frame length).
NOTE The reference to the specification for the ATRAC-X bitstream, representing 2 048, 512, 256 or 128 samples
of encoded audio per frame, may be found in the Bibliography.

Pa Pb Pc Pd ATRAC-X Pa Pb Pc Pd ATRAC-X
Burst_payload Burst_payload
Bit 0 of Pa Bit 0 of Pa
Stuffing ATRAC-X frame
ATRAC-X frame
Regular rate of ATRAC-X frames
Repetition period of the burst
IEC  1529/04
Figure 5 – ATRAC-X data-burst
The data-type-dependent information for ATRAC-X is given in Table 4.
Table 4 – Data-type-dependent information for data-type ATRAC-X
Bits of Pc Data type dependent, Contents
bit number
LSB.MSB LSB.MSB
8-12 00h – 1Fh reserved, shall be set to ‘0’

The reference point of an ATRAC-X data-burst is bit 0 of Pa and shall occur exactly once
every 2 048, 512, 256 or 128 sampling periods. The data-burst containing ATRAC-X frames
shall occur at a regular rate, with the reference point of each ATRAC-X data-burst beginning
2 048, 512, 256 or 128 IEC 60958 frames after the reference point of the preceding ATRAC-X
data-burst (of the same bit-stream-number).
NOTE 1 It is recommended that Pause data-bursts are used to fill stream gaps in the ATRAC-X bit stream as
described in IEC 61937-1, 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 61937-1).
When a stream gap in an ATRAC-X stream is filled by a sequence of Pause data-bursts, the
Pa of the first Pause data-burst shall be located 2 048, 512, 256 or 128 sampling periods
following the Pa of the previous ATRAC-X frame.

– 12 – IEC 61937-7:2004+AMD1:2016 CSV
 IEC 2016
NOTE 2 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 considering the 32 IEC 60958 frame length of the Pause data-burst) the
Pa of the first ATRAC-X data-burst which follows the stream gap.
The gap-length parameter contained in the Pause data-burst is intended to be interpreted by
the ATRAC-X decoder as an indication of the number of decoded PCM samples which are
missing (due to the resulting audio gap).
5.2.6 Latency of ATRAC-X decoding
The latency of an external audio decoder to decode ATRAC-X is defined as the sum of the
receiving delay time and the decoding delay time (see Figure 6).

Pb Pc Pd
Pa Pb Pc Pd ATRAC-X Pa ATRAC-X
Burst_payload Burst_payload
Bit 0 of Pa Bit 0 of Pa
Stuffing ATRAC-X frame
ATRAC-X frame
Repetition period of the burst
Receiving delay Decoding delay
Latency of ATRAC-X decoder
IEC  1530/04
Figure 6 – Latency of ATRAC-X decoding
EXAMPLE The receiving delay time to receive a whole data-burst is calculated as follows.
The length of preamble is 64 bits. If each ATRAC-X frame consists of maximum bit rate of
352,8 kbit/s, the maximum length of the whole data burst-payload is 16 384 bits. In this case,
the whole length of the data burst is 16 448 bits. The receiving delay time is calculated as
11,66 ms with 44,1 kHz sampling frequency. The decoding delay time is calculated as
46,44 ms, and is equal to the decoding time for one ATRAC-X frame data. Hence, the latency
of ATRAC-X decoding is approximately 58,10 ms in this case.
The latencies of each subdata-type ATRAC-X and ATRAC-X low latency are calculated as
follows.
EXAMPLE 1 (ATRAC-X subdata-type 0) In this case, the sampling period is 2 048. The length of preamble is
64 bit. If each ATRAC-X frame consists of a maximum bit rate of 352,8 kbit/s, the maximum length of the whole
data burst-payload is 16 384 bit. In this case, the whole length of the data burst is 16 448 bit. The receiving delay
time is calculated as 11,66 ms with 44,1 kHz sampling frequency. The decoding delay time is calculated as
46,44 ms, and is equal to the decoding time for one ATRAC-X frame data. Hence, the latency of ATRAC-X
decoding is approximately 58,10 ms in this case.
The absolute maximum decoding latency is taken when ATRAC-X burst-payload extends to
just before the Pa of the next frame and is equal to 92,88 ms at 44,1 kHz sampling frequency.
EXAMPLE 2 (ATRAC-X low latency subdata-type 1) In this case, the sampling period is 512. The length of
preamble is 64 bit. If each ATRAC-X low latency subdata-type 1 frame consists of bit rate of 990 kbit/s, the length
of the whole data burst-payload is 2 640 bit. In this case, the whole length of the data burst is 2 704 bit. The
receiving delay time is calculated as 0,44 ms with 192 kHz sampling frequency. The decoding delay time is
calculated as 2,66 ms, and is equal to the decoding time for one ATRAC-X low latency subdata-type 1 frame data.
Hence, the latency of ATRAC-X low latency subdata-type 1 decoding is approximately 3,10 ms in this case.

 IEC 2016
The absolute maximum decoding latency is taken when ATRAC-X low latency subdata-type 1
burst-payload extends to just before the Pa of the next frame and is equal to 5,33 ms at
192 kHz sampling frequency.
EXAMPLE 3 (ATRAC-X low latency subdata-type 2) In this case, the sampling period is 256. The length of
preamble is 64 bit. If each ATRAC-X low latency subdata-type 2 frame consists of bit rate of 990 kbit/s, the length
of the whole data burst-payload is 2 640 bit. In this case, the whole length of the data burst is 2 704 bit. The
receiving delay time is calculated as 0,88 ms with 96 kHz sampling frequency. The decoding delay time is
calculated as 2,66 ms, and is equal to the decoding time for one ATRAC-X low latency subdata-type 2 frame data.
Hence, the latency of ATRAC-X low latency subdata-type 2 decoding is approximately 3,54 ms in this case.
The absolute maximum decoding latency is taken when ATRAC-X low latency subdata-type 2
burst-payload extends to just before the Pa of the next frame and is equal to 5,33 ms at
96 kHz sampling frequency.
EXAMPLE 4 (ATRAC-X low latency subdata-type 3) In this case, the sampling period is 128. The length of
preamble is 64 bit. If each ATRAC-X low latency subdata-type 3 frame consists of a bit rate of 990 kbit/s, the
length of the whole data burst-payload is 2 640 bit. In this case, the whole length of the data burst is 2 704 bit. The
receiving delay time is calculated as 1,76 ms with 48 kHz sampling frequency. The decoding delay time is
calculated as 2,66 ms, and is equal to the decoding time for one ATRAC-X low latency subdata-type 3 frame data.
Hence, the latency of ATRAC-X low latency subdata-type 3 decoding is approximately 4,42 ms in this case.
The absolute maximum decoding latency is taken when ATRAC-X low latency subdata-type 3
burst-payload extends to just before the Pa of the next frame and is equal to 5,33 ms at
48 kHz sampling frequency.
NOTE ATRAC-X low latency has plural sampling periods to change by sampling frequency. Therefore, several
sampling periods have the same decoding delay time.

– 14 – IEC 61937-7:2004+AMD1:2016 CSV
 IEC 2016
Bibliography
The following documents have served as references for the specification of the related data-
type and other parts of IEC 61937.
Data-type Reference
ATRAC IEC 61909, Audio recording – Minidisc system
ATRAC2 MD Data System Description, January 1995, Sony Corporation
ATRAC3 Memory Stick Standard Audio File Format Specifications, ver. 1.0, Chap. 6
ATRAC3, September 1999, Sony Corporation
ATRAC-X ATRAC-X, Memory Stick Standard Audio File Format Specifications,
ver. 2.1, Chap. 7
ATRAC-X, 2001, 2002, Sony Corporation (ATRAC-X)
ATRAC-X, low latency Standard Specification ver.1.0, 2014, Sony
Corporation. (ATRAC-X low latency subdata-type 1, 2 and 3)

___________
– 16 – IEC 61937-7:2004+AMD1:2016 CSV
 IEC 2016
SOMMAIRE
AVANT-PROPOS . 17
INTRODUCTION à l’Amendement 1 . 20
1 Domaine d’application . 21
2 Références normatives . 21
3 Termes, définitions et abréviations . 21
3.1 Définitions . 21
3.2 Abréviations . 21
4 Mappage du flux de bits audio sur l'interface IEC 61937 . 22
4.1 Généralités . 22
4.2 Salve d'informations aux formats ATRAC, ATRAC2/3 et ATRAC-X . 22
5 Formats des salves de données ATRAC, ATRAC2/3 et ATRAC-X . 22
5.1 Généralités . 22
5.2 Salves de données audio . 23
5.2.1 Données ATRAC . 23
5.2.2 Latence du décodage ATRAC . 24
5.2.3 Données ATRAC2/3 . 24
5.2.4 Latence du décodage ATRAC2/3 . 26
5.2.5 Données ATRAC-X . 26
5.2.6 Latence du décodage ATRAC-X . 27
Bibliographie . 30

Figure 1 – Salve de données au format ATRAC . 23
Figure 2 – Latence du décodage ATRAC . 24
Figure 3 – Salve de données au format ATRAC2/3 . 25
Figure 4 – Latence du décodage ATRAC2/3 . 26
Figure 5 – Salve de données au format ATRAC-X . 27
Figure 6 – Latence du décodage ATRAC-X. 28

Tableau 1 – Champs de la salve d’informations . 22
Tableau 2 – Informations dépendantes du type de données pour le type de données au
format ATRAC . 23
Tableau 3 – Informations dépendantes du type de données pour le type de données au
format ATRAC2/3. 25
Tableau 4 – Informations dépendantes du type de données pour le type de données au
format ATRAC-X . 27

 IEC 2016
COMMISSION ÉLECTROTECHNIQUE INTERNATIONALE
____________
AUDIONUMÉRIQUE –
INTERFACE POUR LES FLUX DE BITS AUDIO À CODAGE MIC
NON LINÉAIRE CONFORMÉMENT À L’IEC 60958 –
Partie 7: Flux de bits MIC non linéaire selon les formats ATRAC,
ATRAC2/3 et ATRAC-X
AVANT-PROPOS
1) La Commission Electrotechnique Internationale (IEC) est une organisation mondiale de normalisation
composée de l'ensemble des comités électrotechniques nationaux (Comités nationaux de l’IEC). L’IEC a pour
objet de favoriser la coopération internationale pour toutes les questions de normalisation dans les domaines
de l'électricité et de l'électronique. A cet effet, l’IEC – entre autres activités – publie des Normes internationales,
des Spécifications techniques, des Rapports techniques, des Spécifications accessibles au public (PAS) et des
Guides (ci-après dénommés "Publication(s) de l’IEC"). Leur élaboration est confiée à des comités d'études, aux
travaux desquels tout Comité national intéressé par le sujet traité peut participer. Les organisations
internationales, gouvernementales et non gouvernementales, en liaison avec l’IEC, participent également aux
travaux. L’IEC collabore étroitement avec l'Organisation Internationale de Normalisation (ISO), selon des
conditions fixées par accord entre les deux organisations.
2) Les décisions ou accords officiels de l’IEC concernant les questions techniques représentent, dans la mesure
du possible, un accord international sur les sujets étudiés, étant donné que les Comités nationaux de l’IEC
intéressés sont représentés dans chaque comité d’études.
3) Les Publications de l’IEC se présentent sous la forme de recommandations internationales et sont agréées
comme telles par les Comités nationaux de l’IEC. Tous les efforts raisonnables sont entrepris afin que l’IEC
s'assure de l'exactitude du contenu technique de ses publications; l’IEC ne peut pas être tenue responsable de
l'éventuelle mauvaise utilisation ou interprétation qui en est faite par un quelconque utilisateur fi
...