1、BRITISH STANDARDBS EN 61937-8:2007Digital 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 The European Standard EN 61937-8:2007 has the status of a British StandardICS 35.0
2、40g49g50g3g38g50g51g60g44g49g42g3g58g44g55g43g50g56g55g3g37g54g44g3g51g40g53g48g44g54g54g44g50g49g3g40g59g38g40g51g55g3g36g54g3g51g40g53g48g44g55g55g40g39g3g37g60g3g38g50g51g60g53g44g42g43g55g3g47g36g58BS EN 61937-8:2007This British Standard was published under the authority of the Standards Policy
3、and Strategy Committee on 31 May 2007 BSI 2007ISBN 978 0 580 50725 0National forewordThis British Standard was published by BSI. It is the UK implementation of EN 61937-8:2007. It is identical with IEC 61937-8:2006.The UK participation in its preparation was entrusted to Technical Committee EPL/100,
4、 Audio, video and multimedia systems and equipment.A list of organizations represented on this committee can be obtained on request to its secretary.This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application.Compliance w
5、ith a British Standard cannot confer immunity from legal obligations.Amendments issued since publicationAmd. No. Date CommentsEUROPEAN STANDARD EN 61937-8 NORME EUROPENNE EUROPISCHE NORM March 2007 CENELEC European Committee for Electrotechnical Standardization Comit Europen de Normalisation Electro
6、technique Europisches Komitee fr Elektrotechnische Normung Central Secretariat: rue de Stassart 35, B - 1050 Brussels 2007 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members. Ref. No. EN 61937-8:2007 E ICS 35.040 English version Digital audio - I
7、nterface 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 61937-8:2006) Audionumrique - Interface pour les flux de bits audio codage MIC non linaire, conformment la CEI 60958 - Parti
8、e 8: Flux de bits MIC non linaire selon le format “Windows Media Audio (WMA) Professional“ (CEI 61937-8:2006) Digitalton - Schnittstelle fr nichtlinear PCM-codierte Audio-Bitstrme unter Verwendung von IEC 60958 - Teil 8: Nichtlineare PCM-Bitstrme nach dem Windows-Media-Audio(WMA)-Professional-Format
9、 (IEC 61937-8:2006) This European Standard was approved by CENELEC on 2007-02-01. CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists
10、and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CENELEC member. This European Standard exists in two official versions (English and German). A version in any other language made by translation under the responsibil
11、ity of a CENELEC member into its own language and notified to the Central Secretariat has the same status as the official versions. CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Cyprus, the Czech Republic, Denmark, Estonia, Finland, France, Germany, Gree
12、ce, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. EN 61937-8:2007 2 Foreword The text of the International Standard IEC IEC 61937-8:2006, prepared by T
13、echnical Area 4, Digital system interfaces, of IEC TC 100, Audio, video and multimedia systems and equipment, was submitted to the formal vote and was approved by CENELEC as EN 61937-8 on 2007-02-01 without any modification. The following dates were fixed: latest date by which the EN has to be imple
14、mented at national level by publication of an identical national standard or by endorsement (dop) 2008-02-01 latest date by which the national standards conflicting with the EN have to be withdrawn (dow) 2010-02-01 Annex ZA has been added by CENELEC. _ Endorsement notice The text of the Internationa
15、l Standard IEC IEC 61937-8:2006 was approved by CENELEC as a European Standard without any modification. _ 3 EN 61937-8:2007 CONTENTS 1 Scope 4 2 Normative references .4 3 Terms, definitions and abbreviations .4 3.1 Terms and definitions 4 3.2 Abbreviations 4 3.3 Presentation convention 5 4 Mapping
16、of the audio bitstream on to IEC 61937 .5 4.1 General .5 4.2 Windows Media Audio Professional burst-info 5 5 Format of WMA Professional data-burst 5 5.1 General .5 5.2 Pause data-burst .6 5.3 Audio data-bursts 6 Annex ZA (normative) Normative references to international publications with their corre
17、sponding European publications 14 Bibliography .13 Figure 1 Windows Media Audio Professional type I data-burst.6 Figure 2 Latency of WMA Professional type I decoding.7 Figure 3 Windows Media Audio Professional type II data-burst7 Figure 4 Latency of WMA Professional type II decoding8 Figure 5 Window
18、s Media Audio Professional type III data-burst.9 Figure 6 Latency of WMA Professional type III decoding.9 Figure 7 Windows Media Audio Professional type IV data-burst 10 Figure 8 Latency of WMA Professional type IV decoding.11 Table 1 Fields of burst-info.5 Table 2 Repetition period of Pause data-bu
19、rsts.6 Table 3 Data-type-dependent when data-type = 18 and sub-type = 0.6 Table 4 Data-type-dependent when data-type = 18 and sub-type = 1.8 Table 5 Data-type-dependent when data-type = 18 and sub-type = 2.9 Table 6 Data-type-dependent when data-type = 18 and sub-type = 3.10 EN 61937-8:2007 4 DIGITA
20、L 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-l
21、inear 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 refer
22、enced 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 apply
23、ing 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 d
24、ata 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 Bu
25、reauWMA Windows Media Audio 5 EN 61937-8:2007 3.3 Presentation convention F872h Value F872 in hexadecimal format 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
26、-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 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
27、 WMA Professional Subtype dependent Subtype dependent 19-31 According to IEC 61937-2 5 6 Data subtype 0 WMA Professional Type I Bit 0 of Paa2 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 IE
28、C 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, th
29、e method of filling stream gaps, and decoding latency are specified for each data-type. EN 61937-8:2007 6 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 aud
30、io. 5.2 Pause data-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
31、 frames Windows 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 primari
32、ly intended for 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 i
33、s 12 h and the 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-
34、bursts of WMA 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). Pa Pb Pc Pd Burst-payload Pa Pb Pc PdBit 0 of PaBit 0 of PaWMA Professiona
35、l frameRepetition period of the burstPa Pb Pc Pd Burst-payload (cont.)StuffingFigure 1 Windows Media Audio Professional Type I data-burst The data-type-dependent info 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
36、 dependent, bit number LSBMSB Contents 8-12 0-4 Reserved, shall be set to 00 IEC 1986/06 7 EN 61937-8:2007 The data-bursts containing WMA Professional Type I frames shall occur at a regular rate, with the reference point of each WMA Professional frame (bit 0 of Pa of the first of the pair of data-bu
37、rsts) 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). 5.3.2 Latency of WMA Professional Type I decoding The latency of an audio decoder to decode a Windows Media Audio Profe
38、ssional 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. This 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 samp
39、les per frame. IEC 1987/06 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 bit-stream as described in IEC 61937-1, and that Pause data-bursts be transmitted with a repetition period of three sampling p
40、eriods 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 stream gap in a WMA Professional Type I str
41、eam 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 WMA Professional frame. It is recommended that the sequence(s) of Pause data-bursts which fill the stream gap should continue from this poin
42、t up to (as close as possible considering the three IEC 60958 frame length of the Pause data-burst) the Pa of the first WMA Professional data-burst which follows the stream gap. The gap-length parameter contained in the Pause data-burst is intended to be interpreted by the WMA Professional decoder a
43、s an indication of the number of decoded PCM samples which are missing (due to the resulting audio gap). 5.3.3 The data-burst for WMA Professional Type II The WMA Professional bitstream consists of a sequence of WMA Professional frames. The data-type of a WMA Professional Type II data-burst is 12 h
44、and the subtype is 1 h. A WMA Professional Type II frame represents 2 048 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 WMA Professional Type II data shall contain one
45、 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). Pa Pb Pc Pd WMA Professional burst-payload Pa Pb Pc PdBit 0 of Pa Bit 0 of PaWMA Professional frame StuffingRepetition period of t
46、he burstIEC 1988/06 Figure 3 Windows Media Audio Professional Type II data-burst EN 61937-8:2007 8 The data-type-dependent info for WMA Professional is given in Table 4. Table 4 Data-type-dependent when data-type = 18 and subtype = 1 Bits of Pc LSBMSB Data type dependent, bit number LSBMSB Contents
47、8-12 0-4 reserved, shall be set to 00 The data-bursts containing WMA Professional Type II frames shall occur at a regular rate, with the reference point of each WMA Professional data-burst (bit 0 of Pa) beginning (except in the case of a gap) 2 048 sampling periods of the audio after the reference p
48、oint of the preceding WMA Professional data-burst (of the same bit-stream-number). 5.3.4 Latency of WMA Professional Type II decoding The latency of an audio decoder to decode a Windows Media Audio Professional data-burst is defined as two repetition periods (85,33 ms for fs = 48 kHz), plus the deco
49、ding delay, which is the time to output the first linear PCM sample (Figure 4, 28,44 ms for fs = 48 kHz). The latency is defined as a delay of 113,77 ms for fs = 48 kHz, 123,83 ms for fs = 44,1 kHz, and 56,88 ms for fs = 96 kHz. Pa Pb Pc Pd Burst-payload Pa Pb Pc PdBit 0 of Pa Bit 0 of PaFrameBurst-payload Pa Pb Pc PdStuffingTime to receive data-burstof maximum lengthRepetition period of the burstDecoding delayLatency of WMA Professio
