1、 INTERNATIONAL STANDARD IEC 61937-8First edition 2006-10Digital 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 IEC 61937-8:2006(E) Publication numbering A
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8、11 Fax: +41 22 919 03 00 INTERNATIONAL STANDARD IEC 61937-8First edition 2006-10Digital 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 rese
9、rved 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 Varemb, PO Box 131, CH-1211 Geneva 20, Sw
10、itzerland Telephone: +41 22 919 02 11 Telefax: +41 22 919 03 00 E-mail: inmailiec.ch Web: www.iec.ch M For price, see current catalogue PRICE CODE Commission Electrotechnique Internationale International Electrotechnical Commission 2 61937-8 IEC:2006(E) CONTENTS FOREWORD.3 1 Scope.5 2 Normative refe
11、rences .5 3 Terms, definitions and abbreviations 5 3.1 Terms and definitions 5 3.2 Abbreviations 5 3.3 Presentation convention5 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
12、.6 5.2 Pause data-burst.7 5.3 Audio data-bursts 7 Bibliography13 Figure 1 Windows Media Audio Professional type I data-burst .7 Figure 2 Latency of WMA Professional type I decoding8 Figure 3 Windows Media Audio Professional type II data-burst 8 Figure 4 Latency of WMA Professional type II decoding.9
13、 Figure 5 Windows Media Audio Professional type III data-burst .10 Figure 6 Latency of WMA Professional type III decoding10 Figure 7 Windows Media Audio Professional type IV data-burst .11 Figure 8 Latency of WMA Professional type IV decoding11 Table 1 Fields of burst-info 6 Table 2 Repetition perio
14、d of Pause data-bursts7 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 61
15、937-8 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 1) The International Electrotechnical Commi
16、ssion (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 i
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24、ther 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
25、. 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 pat
26、ent rights. 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 100/10
27、95/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, und
28、er 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 “h
29、ttp:/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
30、-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 enco
31、ded 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
32、 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: Bur
33、st-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
34、 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 Au
35、dio 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 bur
36、st-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 Bits of Pc Value Contents Reference point R Repetition period of data-burst in IEC 60958 frames 0 4 Data-type 0-17 According to IEC 61937-2 18 WMA Professional Su
37、btype dependent Subtype dependent 19-31 According to IEC 61937-2 5 6 Data subtype 0 WMA Professional Type I Bit 0 of Pa a2 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 ref
38、erence 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
39、 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 data-bursts as necessary to establish synchronization between picture and decoded audio. 61937-8 IEC:2006(E) 7 5.2 Pause d
40、ata-burst Pause data-burst for WMA Professional Types I, II, III, and IV are given in Table 2. Table 2 Repetition period of Pause data-bursts Repetition period of Pause data-burst Data-type of Audio data-burst Mandatory Recommended Windows Media Audio Professional Type I - 3 IEC 60958 frames Windows
41、 Media Audio Professional Type II - 3 IEC 60958 frames Windows Media Audio Professional Type III - 3 IEC 60958 frames Windows Media Audio Professional Type IV - 3 IEC 60958 frames 5.3 Audio data-bursts 5.3.1 The data-burst for WMA Professional Type I WMA Professional Type I is primarily intended for
42、 use at sample rates above 48 kHz (for example, 88,2 kHz or 96 kHz). The IEC 60958 link should be operated at the sample rate of the decoded audio. The WMA Professional bitstream consists of a sequence of WMA Professional frames. The data-type of a WMA Professional Type I data-burst is 12 h and the
43、subtype is 0 h. A WMA Professional Type I frame represents 4 096 samples of each encoded audio channel (left, centre, etc.) transmitted in two sequential data-bursts. The data-burst is headed with a burst- preamble, followed by the burst-payload. The burst-payload of each pair of data-bursts of WMA
44、Professional Type I data shall contain one complete WMA Professional frame. The length of the WMA Professional data-burst will depend on the encoded bit rate (which determines the WMA Professional frame length). Figure 1 Windows Media Audio Professional Type I data-burst The data-type-dependent info
45、 for WMA Professional is given in Table 3. Table 3 Data-type-dependent when data-type = 18 and subtype = 0 Bits of Pc LSBMSB Data type dependent, bit number LSBMSB Contents 8-12 0-4 Reserved, shall be set to 00 The data-bursts containing WMA Professional Type I frames shall occur at a regular rate,
46、with the reference point of each WMA Professional frame (bit 0 of Pa of the first of the pair of data- bursts) beginning (except in the case of a gap) 4 096 sampling periods of the audio after the reference point of the preceding WMA Professional frame (of the same bit-stream-number). IEC 1986/06 8
47、61937-8 IEC:2006(E) 5.3.2 Latency of WMA Professional Type I decoding The latency of an audio decoder to decode a Windows Media Audio Professional data-burst is defined as two Windows Media Audio Professional frames, plus a decoding delay of two-thirds of a Windows Media Audio Professional frame. Th
48、is corresponds to a latency of 123,84 ms at 88,2 kHz and 113,77 ms at 96 kHz sampling frequency, where the maximum frame size is 4 096 samples per frame. Figure 2 Latency of WMA Professional Type I decoding It is recommended that Pause data-bursts are used to fill stream gaps in the WMA Professional
49、 bit-stream as described in IEC 61937-1, and that Pause data-bursts be transmitted with a repetition period of three sampling periods of the audio, except when other repetition periods are necessary to fill the precise stream gap length (which may not be a multiple of three sampling periods of the audio), or to meet the requirement on burst spacing (see IEC 61937-1, 6.3.3). When a s
