1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationDigital audio Interface for non-linear PCM encodedaudio bitstreams applying IEC 60958 Part 3: Non-linear PCM bitstreams according to the AC-3 and enhanced AC-3 formatsBS EN 61937
2、-3:2009National forewordThis British Standard is the UK implementation of EN 61937-3:2009. It is identical to IEC 61937-3:2007. It supersedes BS EN 61937-3:2003, which is withdrawn.The UK participation in its preparation was entrusted to Technical Committee EPL/100, Audio, video and multimedia syste
3、ms 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. BSI 2011ISBN 978 0 580 76165 2 ICS 33.160.30C
4、ompliance with a British Standard cannot confer immunity from legal obligations.This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 July 2011.Amendments issued since publicationAmd. No. Date Text affectedBRITISH STANDARDBS EN 61937-3:2009EUROP
5、EAN STANDARD EN 61937-3 NORME EUROPENNE EUROPISCHE NORM August 2009 CENELEC European Committee for Electrotechnical Standardization Comit Europen de Normalisation Electrotechnique Europisches Komitee fr Elektrotechnische Normung Central Secretariat: Avenue Marnix 17, B - 1000 Brussels 2009 CENELEC -
6、 All rights of exploitation in any form and by any means reserved worldwide for CENELEC members. Ref. No. EN 61937-3:2009 E ICS 33.160.30 Supersedes EN 61937-3:2003English version Digital audio - Interface for non-linear PCM encoded audio bitstreams applying IEC 60958 - Part 3: Non-linear PCM bitstr
7、eams according to the AC-3 and enhanced AC-3 formats (IEC 61937-3:2007) Audionumrique - Interface pour les flux de bits audio codage MIC non linaire conformment la CEI 60958 - Partie 3: Flux de bits MIC non linaire conformment aux formats AC-3 et AC-3 amlior (CEI 61937-3:2007) Digitalton - Schnittst
8、elle fr nichtlinear-PCM-codierte Audio-Bitstrme unter Verwendung von IEC 60958 - Teil 3: Nichtlineare PCM-Bitstrme nach dem AC-3- und dem erweiterten AC-3-Format (IEC 61937-3:2007) This European Standard was approved by CENELEC on 2009-07-01. CENELEC members are bound to comply with the CEN/CENELEC
9、Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CENEL
10、EC member. This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CENELEC member into its own language and notified to the Central Secretariat has the same status as the official versions.
11、CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Cyprus, the Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slov
12、akia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. BS EN 61937-3:2009EN 61937-3:2009 Foreword The text of document 100/1207/CDV, future edition 2 of IEC 61937-3, prepared by technical area 4, Digital system interfaces, of IEC TC 100, Audio, video and multimedia systems and equipment,
13、 was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as EN 61937-3 on 2009-07-01. This European Standard supersedes EN 61937-3:2003. EN 61937-3:2009 contains the following significant technical changes with respect to EN 61937-3:2003. the definition of the audio data-burst req
14、uired to deliver enhanced AC-3 bitstreams has been added; the definition of the latency of an enhanced AC-3 decoder has been added; the use of pause data-bursts when delivering enhanced AC-3 bitstreams has been added. The following dates were fixed: latest date by which the EN has to be implemented
15、at national level by publication of an identical national standard or by endorsement (dop) 2010-04-01 latest date by which the national standards conflicting with the EN have to be withdrawn (dow) 2012-07-01 Annex ZA has been added by CENELEC. _ Endorsement notice The text of the International Stand
16、ard IEC 61937-3:2007 was approved by CENELEC as a European Standard without any modification. _ BS EN 61937-3:2009EN 61937-3:2009 Annex ZA (normative) Normative references to international publications with their corresponding European publications The following referenced documents are indispensabl
17、e 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. NOTE When an international publication has been modified by common modifications, indicated by (mod)
18、, the relevant EN/HD applies. Publication Year Title EN/HD Year IEC 60958 Series Digital audio interface EN 60958 Series IEC 61937-1 2007 Digital audio - Interface for non-linear PCM encoded audio bitstreams applying IEC 60958 - Part 1: General EN 61937-1 2007 IEC 61937-2 2007 Digital audio - Interf
19、ace for non-linear PCM encoded audio bitstreams applying IEC 60958 - Part 2: Burst-info EN 61937-2 2007 ETSI TS 102 366 - 1 )Digital Audio Compression (AC-3, Enhanced AC-3) - - ATSC A/52B - 1)Digital Audio Compression (AC-3, E-AC-3), Rev. B - - 1)Undated reference. BS EN 61937-3:200961937-3 IEC:2007
20、(E) CONTENTS 1 Scope.5 2 Normative references.5 3 Terms, definitions and abbreviations . 5 3.1 Terms and definitions5 3.2 Abbreviations. .6 4 Mapping of the audio bitstream on to IEC 61937-1 . 6 4.1 General . 6 4.2 AC-3 and enhanced AC-3 burst-info6 5 Format of AC-3 and enhanced AC-3 data-bursts . .
21、6 5.1 General . 6 5.2 Pause data-burst . 7 5.3 Audio data-bursts . .7 5.3.1 AC-3 data . .7 5.3.2 Latency of AC-3 decoding . 8 5.3.3 Enhanced AC-3 data . .9 5.3.4 Latency of the enhanced AC-3 decoder . .10 Bibliography . 13 Figure 1 AC-3 data-burst, with reference point R 7 Figure 2 Latency of AC-3 d
22、ecoding . 8 Figure 3 Enhanced AC-3 data-burst. .10 Figure 4 Latency of enhanced AC-3 decoding . 11 Table 1 Fields of burst-info.6 Table 2 Repetition period of the pause data-bursts . .7 Table 3 Data-type-dependent information when data-type = 1 . .7 Table 4 Data-type-dependent information when data-
23、type = 21 10 Table 5 Frame repetition period and maximum data rate for enhanced AC-3 bitstreams . .10 BS EN 61937-3:200961937-3 IEC:2007(E) 5 DIGITAL AUDIO INTERFACE FOR NON-LINEAR PCM ENCODED AUDIO BITSTREAMS APPLYING IEC 60958 Part 3: Non-linear PCM bitstreams according to the AC-3 and enhanced AC
24、-3 formats 1 Scope This part of IEC 61937 describes the method used to convey non-linear PCM bitstreams encoded according to the AC-3 and enhanced AC-3 formats. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, onl
25、y 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 61937-1:2007, Digital audio interface for non-linear PCM encoded audio bitstreams applying IEC 60958 Part 1: Gener
26、al IEC 61937-2:2007, Digital audio interface for non-linear PCM encoded audio bitstreams applying IEC 60958 Part 2: Burst-info ATSC Standard A/52B, Digital Audio Compression (AC-3, E-AC-3), Rev. B ETSI TS 102 366, Digital Audio Compression (AC-3, Enhanced AC-3) 3 Terms and definitions For the purpos
27、es of this standard, the following terms, definitions and abbreviations apply. 3.1 Terms and definitions 3.1.1 latency delay time of an external audio decoder to decode an AC-3 or enhanced AC-3 data burst, defined as the sum of two values of the receiving delay time and the decoding delay time. 3.1.
28、2 stream type an enhanced AC-3 bitstream is constructed from one or more substreams, with each substream being constructed from a sequence of frames. The stream type parameter of an enhanced AC-3 frame identifies the type of substream of which the frame is a part BS EN 61937-3:2009 6 61937-3 IEC:200
29、7(E) 3.1.3 substream identification substream identification parameter of an enhanced AC-3 frame which, in conjunction with the stream type parameter, identifies the substream in the bitstream of which the enhanced AC-3 frame is a part 3.1.4 converter synchronization flag flag used for synchronizati
30、on by a device that converts an enhanced AC-3 bitstream to a bitstream compliant with an AC-3 decoder and indicates that the first block in this enhanced AC-3 frame will form the first block of the AC-3 frame output by the conversion process 3.1.5 block identification flag if the stream type value o
31、f an enhanced AC-3 substream is two, indicating that the bitstream has been converted from an AC-3 bitstream, this bit is set to 1 to indicate that the first block in this enhanced AC-3 frame was the first block in the original standard AC-3 frame 3.2 Abbreviations ATSC Advanced Television Standards
32、 Committee ETSI European Telecommunication Standards Institute IEC International Electrotechnical Commission ISO/IEC MPEG Moving Pictures Expert Group, a joint committee of ISO and IEC 4 Mapping of the audio bitstream on to IEC 61937-1 4.1 General The coding of the bitstream and data-burst is in acc
33、ordance with IEC 61937-1 and 61937-2. 4.2 AC-3 and enhanced AC-3 burst-info The 16-bit burst-info contains information about the data which will be found in the data-burst (see Table 1). Table 1 Fields of burst-info Data-type Value of Pc bits 0-4 Sub- data-type Value of Pc bits 5-6 Contents Referenc
34、e point R Repetition period of data-burst measured in IEC 60958 frames 1 0 AC-3 R-AC-3 1 536 21 0 Enhanced AC-3 Bit 0 of Pa 6 144 1-3 Reserved Reserved Reserved 5 Format of AC-3 and enhanced AC-3 data-bursts 5.1 General This clause specifies the audio data-bursts AC-3 and enhanced AC-3. Specific pro
35、perties such as reference points, repetition periods, the method of filling stream gaps, and decoding latency are specified. BS EN 61937-3:200961937-3 IEC:2007(E) 7 The decoding latency (or delay), indicated for the data-type, should be used by the transmitter to schedule data-bursts as necessary to
36、 establish synchronization between picture and decoded audio. 5.2 Pause data-burst Pause data-bursts for AC-3 and enhanced AC-3 are given in Table 2. Table 2 Repetition period of the pause data-bursts Repetition period of pause data-burst Data-type of audio data-burst Mandatory Recommended AC-3 - 3
37、IEC 60958 frames Enhanced AC-3 - 4 IEC 60958 frames 5.3 Audio data-bursts 5.3.1 AC-3 data The AC-3 bitstream consists of a sequence of AC-3 frames. The data-type of an AC-3 data-burst is 1. An AC-3 frame represents 1 536 samples of each encoded audio channel (left, centre, etc.). The data-burst is h
38、eaded with a burst-preamble followed by the burst-payload. The burst-payload of each data burst of AC-3 data shall contain one complete AC-3 frame. Figure 1 shows the structure of the AC-3 data-burst. The length of the AC-3 data-burst will depend on the encoded bit rate (which determines the AC-3 fr
39、ame length). The specification for the AC-3 bitstream may be found in ATSC Standard A52/B or in ETSI TS 102 366. Figure 1 AC-3 data-burst, with reference point R The data-type-dependent info for AC-3 is given in Table 3. Table 3 Data-type-dependent information when data-type = 1 Bits of Pc LSBMSB Da
40、ta type dependent, bit number LSBMSB Contents 8-10 0-2 Value of bsmod parameter in AC-3 elementary stream 11, 12 3-4 Reserved R-AC-3AC-3 burst-payload Pd Pa Pb Pc Repetition period of the burst StuffingRegular rate of the AC-3 syncframes AC-3 burst-payload Pd Pa Pb Pc AC-3 frame R-AC-3AC-3 frameBS E
41、N 61937-3:2009 8 61937-3 IEC:2007(E) The data-bursts containing AC-3 frames shall occur at a regular rate, with the reference point of each AC-3 data-burst beginning (except in the case of a gap) 1 536 sampling periods of the audio after the reference point of the preceding AC-3 data burst (of the s
42、ame bitstream number). The reference point of an AC-3 data-burst (R-AC-3) is the IEC 60958 frame that occurs two-thirds of the way through the AC-3 payload. The definition of the two-thirds value is the closest integer to the value of the AC-3 frame size measured in 32-bit words multiplied by the va
43、lue 2/3, or 2/3 frame size = int (0,5 + (2/3) (frame size in 32-bit words) 5.3.2 Latency of AC-3 decoding The latency of an AC-3 decoder which receives this signal is specified, with respect to the reference point of the AC-3 burst, to be equal to one AC-3 block time, which is equal to the time occu
44、pied by 256 PCM samples at the encoded sampling frequency (5,33 ms for 48 kHz sampling frequency; see Figure 2). Figure 2 Latency of AC-3 decoding It is recommended that pause data-bursts be used to fill stream gaps in the AC-3 bitstream, as described in IEC 61937-1, and that pause data-bursts be tr
45、ansmitted with a repetition period of three IEC 60958 frames, except when other repetition periods are necessary to fill the precise stream gap length (which may not be a multiple of three IEC 60958 frames), or to meet the requirement on burst spacing (see IEC 61937-1, 6.3.3). When a stream gap in a
46、n AC-3 stream is filled by a sequence of pause data-bursts, the Pa of the first pause data-burst shall be located one frame repetition period following the Pa of the previous AC-3 frame. It is recommended that the sequence(s) of pause data-bursts which fill the stream gap should continue from this p
47、oint up to (as close as possible considering the three IEC 60958 frame length of the pause data-burst) the Pa of the first AC-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 AC-3 decoder as an indication of th
48、e number of decoded PCM samples which are missing (due to the resulting audio gap). If the sizes of the AC-3 frames before and after the stream gap are not equal (due to a bitrate change in the interrupted AC-3 bitstream), this value may differ from the actual number of sampling periods of the audio
49、 contained in the stream gap due to the definition of the AC-3 burst reference points. Some AC-3 decoders may be capable of “concealing” audio gaps. The indication of the audio gap length (gap-length) which may be included in the payload of the pause data-burst allows the decoder to know how long an audio gap will need to be concealed, and thus allow the decoder to optimize the concealment process for the actual audio gap length. AC-3 decoders will mos
