IEC 61937-8:2006

Digital audio - Interface for non-linear PCM encoded audio bitstreams applying IEC 60958 - Part 8: Non-linear PCM bitstreams according to the Windows Media Audio (WMA) Professional format

specifies the method for the digital audio interface specified in IEC 60958 to convey non-linear PCM bitstreams encoded in accordance with the WMA Professional format.

General Information

• Status: Published
• Publication Date: 24-Oct-2006
• ICS: 35.040.40 - Coding of audio, video, multimedia and hypermedia information
• Technical Committee: TC 100 - Audio, video and multimedia systems and equipment
• Current Stage: PPUB - Publication issued
• Start Date: 25-Oct-2006
• Completion Date: 31-Dec-2006

Overview

IEC 61937-8:2006 defines how to transport Windows Media Audio (WMA) Professional non-linear PCM bitstreams over the digital audio interface specified in IEC 60958. It is Part 8 of the IEC 61937 series and specifies burst formatting, burst-info fields, repetition timing, pause handling and decoder latency requirements for WMA Professional streams mapped onto the IEC 60958 physical interface.

Key topics and technical requirements

• Mapping to IEC 60958: Defines how WMA Professional bitstreams are carried as IEC 61937 data‑bursts (burst-preamble + burst-payload) on an IEC 60958 link.
• Burst-info fields: A 16‑bit burst-info word identifies the data-type and subtype for WMA Professional and contains repetition/format information. The standard provides exact bit-field definitions for these values.
• Four WMA subtypes (Type I–IV): The standard defines four WMA Professional subtypes with different frame sizes and reference points:
  • Type I - frame = 4 096 samples (intended for >48 kHz sample rates such as 88.2 kHz, 96 kHz)
  • Type II - frame = 2 048 samples
  • Type III - implied smaller frame (reference point Pa = 1 024)
  • Type IV - implied smaller frame (reference point Pa = 512)
• Pause data‑bursts: A defined pause data‑burst format and recommended repetition period (typically three IEC 60958 frames) for filling stream gaps; includes a gap-length parameter to indicate missing decoded PCM samples.
• Latency and synchronization: Latency is defined as receiving delay(s) plus decoding delay. For Type I, latency equals two frames plus two‑thirds of a frame (examples: 123.84 ms at 88.2 kHz, 113.77 ms at 96 kHz). Transmitters should schedule bursts using these latency figures to maintain audio/video sync.
• Normative references: Requires IEC 60958 (digital audio interface) and IEC 61937 Parts 1 and 2 for general framing and burst-info conventions.

Applications and who uses it

• Hardware and firmware engineers implementing digital audio interfaces on consumer electronics (DVD/Blu‑ray players, set‑top boxes), professional audio devices, and audio decoders.
• System integrators and broadcast equipment vendors who must convey compressed WMA Professional streams over S/PDIF/IEC 60958 links.
• Test and compliance teams verifying proper burst formatting, pause handling, and synchronization/latency behavior.
• Manufacturers aiming to ensure interoperability between digital transmitters and external WMA Professional decoders.

Related standards

• IEC 60958 - Digital audio interface (physical/format basics)
• IEC 61937-1 - General mapping rules for non-linear PCM bitstreams
• IEC 61937-2 - Burst-info definitions and common fields

Keywords: IEC 61937-8, WMA Professional, digital audio interface, IEC 60958, non-linear PCM, data-burst, burst-info, latency, pause data-burst, audio synchronization.

Standards Content (Sample)

INTERNATIONAL IEC
STANDARD 61937-8
First edition
2006-10
Digital Audio –
Interface for non-linear PCM encoded
audio bitstreams applying IEC 60958 –
Part 8:
Non-linear PCM bitstreams according to the
Windows Media Audio (WMA) Professional 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.
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INTERNATIONAL IEC
STANDARD 61937-8
First edition
2006-10
Digital Audio –
Interface for non-linear PCM encoded
audio bitstreams applying IEC 60958 –
Part 8:
Non-linear PCM bitstreams according to the
Windows Media Audio (WMA) Professional format
© IEC 2006 ⎯ 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
PRICE CODE
Commission Electrotechnique Internationale M
International Electrotechnical Commission
МеждународнаяЭлектротехническаяКомиссия
For price, see current catalogue

– 2 – 61937-8 © IEC:2006(E)
CONTENTS
FOREWORD.3

1 Scope.5
2 Normative references .5
3 Terms, definitions and abbreviations .5
3.1 Terms and definitions .5
3.2 Abbreviations .5
3.3 Presentation convention .5
4 Mapping of the audio bitstream on to IEC 61937 .6
4.1 General .6
4.2 Windows Media Audio Professional burst-info .6
5 Format of WMA Professional data-burst .6
5.1 General .6
5.2 Pause data-burst.7
5.3 Audio data-bursts .7

Bibliography.13

Figure 1 – Windows Media Audio Professional type I data-burst .7
Figure 2 – Latency of WMA Professional type I decoding .8
Figure 3 – Windows Media Audio Professional type II data-burst .8
Figure 4 – Latency of WMA Professional type II decoding.9
Figure 5 – Windows Media Audio Professional type III data-burst .10
Figure 6 – Latency of WMA Professional type III decoding.10
Figure 7 – Windows Media Audio Professional type IV data-burst .11
Figure 8 – Latency of WMA Professional type IV decoding.11

Table 1 – Fields of burst-info .6
Table 2 – Repetition period of Pause data-bursts.7
Table 3 – Data-type-dependent when data-type = 18 and sub-type = 0 .7
Table 4 – Data-type-dependent when data-type = 18 and sub-type = 1 .9
Table 5 – Data-type-dependent when data-type = 18 and sub-type = 2 .10
Table 6 – Data-type-dependent when data-type = 18 and sub-type = 3 .11

61937-8 © IEC:2006(E) – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
DIGITAL AUDIO –
INTERFACE FOR NON-LINEAR PCM ENCODED
AUDIO BITSTREAMS APPLYING IEC 60958

Part-8: Non-linear PCM bitstreams according to
the Windows Media Audio (WMA) Professional format

FOREWORD
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International Standard IEC 61937-8 has been prepared by Technical Area 4: Digital system
interfaces, of IEC technical committee 100: Audio, video and multimedia systems and
equipment.
The text of this standard is based on the following documents:
CDV Report on voting
100/1018A/CDV 100/1095/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.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

– 4 – 61937-8 © IEC:2006(E)
The list of all the parts of the IEC 61937 series, 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 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.
A bilingual version of this publication may be issued at a later date.

61937-8 © IEC:2006(E) – 5 –
DIGITAL AUDIO –
INTERFACE FOR NON-LINEAR PCM ENCODED
AUDIO BITSTREAMS APPLYING IEC 60958

Part-8: Non-linear PCM bitstreams according to
the Windows Media Audio (WMA) Professional format

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

– 6 – 61937-8 © IEC:2006(E)
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.
4.2 Windows Media Audio Professional 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.
Table 1 – Fields of burst-info
Reference Repetition period of
Bits of Pc Value Contents point R data-burst in
IEC 60958 frames
0 – 4 Data-type
0-17 According to IEC 61937-2
18 WMA Professional Subtype dependent Subtype dependent
19-31 According to IEC 61937-2
5 – 6 Data subtype
a
0 WMA Professional – Type I Bit 0 of Pa 2 048
1 WMA Professional – Type II Bit 0 of Pa 2 048
2 WMA Professional – Type III Bit 0 of Pa 1 024
3 WMA Professional – Type IV Bit 0 of Pa 512
7 – 15 According to IEC 61937-2

a
The reference point for a WMA Professional Type I stream is bit 0 of Pa of the first of a payload pair.

5 Format of WMA Professional data-burst
5.1 General
This clause specifies the audio data-burst for WMA Professional. Specific properties such as
reference points, repetition period, the method of filling stream gaps, and decoding latency
are specified for each data-type.
The decoding latency (or delay), indicated for the data-types, should be used by the
transmitter to schedule d
...