1、 STD-BSI BS EN ISO/EC 33818-3-ENGL 3775 3b24bb7 0583073 AT7 BRITISH STANDARD Implementation of EN ISO/IEC 13818-3 : 1996 Information technology - Generic coding of moving pictures and associated audio information Part 3. Audio The European Standard EN ISOIEC 138183 : 1996 has the status of a Briish
2、Standard BS EN ISO/JEC 13818-3 : 1996 BS ISOBEC 13818-3 : 1995 renumbered Amendment No. 1 incmti?lg NO COPYING WITBOUT BSI PERMISSION EXCEPT AS PEBMIITED BY COPYRIGHT LAW STD.BSI BS EN ISO/IEC 13818-3-ENGL 1995 LbZqbb 0583072 733 Amd. No. Date 9285 December 1996 BS EN Iso/IEC 1381843 : 1996 Issue 2,
3、 December 1996 Text dected Irclicated by a sideline in the margin % 13/12/46 Committees responsible for this British Standard The prepamtion of this British Standard was entrusted to Technical cOmmi,ee IS“X37, Coding of picms, audio, inultimedia and hypemedia infunnaon, upon which the foiiowing bodi
4、es were represented: British Broadcasting Corporation British Telecommunications plc Elysium Ltd. GEC Plessey Semiconductors TBM United Kingdom Lt. institution of Electrid Engineers internationai Computers Limited Naionai Health Services Naionai imscommunidons Ltd. PICON Phiiips Recearch Laborabries
5、 Pioneer Digitai Design Cenm Ud. SGS Thomson Microelectronics Ltd. UKERMA This British standard, having been prepared under the direction of the information Systems Technology Assembly, was published under the authority of the Standards Board and comes into effect on 15 October 1995 8 BSI lS5 The fo
6、llowing BSI references relate to the work on this mdad Committee reference ISTL37 Draft fur conment !U4545298 DC ISBN O 580 24811 9 - STD-BSI BS EN ISOIIEC 13818-3-ENGL 1995 = 1b24bb9 0583093 b7T 9 he 1, December 1996 BS EN ISO/IEC 138183 : 1996 Summary of pages The following table identifies the cu
7、rrent issue of each page. Issue 1 indicates that a page has been introduced for the first time by amendment. Subsequent issue numbers indicate an upated page. Verticai sidelining on replacement pages indicates the most recent changes (amendment, addition, deletion). Front cover Inside front cover a
8、b i ii EN cover page iib XSOAEC cover page ii iii issue 2 2 1 blank 2 blank 1 1 Original Original Original iv vi vii viii ix 1 - 101 Back cover V X Change of identifier Wherever BS ISO/IEC 138183 : 1995 appears in this standard, it should be read as BS EN ISOAEC 138183 : 1996. Issue Olginal Original
9、 Original Original Original Orighd Original Originai 2 O BSI 1996 a Issue2, December 1996 BS EN ISMEC 13818-3 : 1996 National foreword This British standard has been prepared by Technical Com IsT/37 and is the English language versior of EN Iso/IEC 138183 - Ibrmatbn tmhmyg - Generic of nuwing ming p
10、icturn txsm - present to the responsible international commi,ee any enquiries on intewretaton, or proposals for change, and keep K interests informW .:ms 48ms _ .- _ . ISOIIEC 13818 was prepared by SC29/WGll, also known as MPEG (Moving Pictures Expert Group). MPEG was formed in 1988 to establish a s
11、tandard for the coded representation of moving pictures and associated audio stored on digital storage media. ISO/lEC 13818 is published in three parts. Part 1 - systems - specifies the system coding layer of the standard. It defines a multiplexed structure for combining audio and video data and mws
12、 of representing the timing information needed to replay synchronised sequences in real-time. Part 2 - video - specifies the coded representation of video data and the decoding process required to reconstruct pictures. Part 3 - audio - specifies the coded representation of audio data and the decodin
13、g process required to decode audio signals. 0.1 Extension of ISOAEC 11 172-3 Audio Coding to Lower Sampling Frequencies In order to achieve better audio quality at very low bit rates ( O when x O Sign(x) = O when x = O Sign(x) = -1 when x Greater than. = I window 1 else for (sfb= sWl2; sfb+) for (wi
14、ndow=O windowO; window* scalefac-s eh sfb window I l eise for (sfbco,sfbc21; sfb-tt) scalefac-l chsfb I Huffmancodebits() I for (b=O; beno-of-ancillary-bit; b+) ancillary-bit O. .4 0.S 0.S 0.S uimsbf uimsbf uimsbf uimsbf 1 bslbf 1 Huffmancodebits - see ISO/IEC 11 172-3.2.4.1.7. 14 STD-BSI BS EN ISO/
15、IEC II38II-3-ENGL II775 9 IIbZqbb9 05IIlII7 70b bitrate-index IS0AE.C 138818-3 1W5(E) bitrate specified bids) for Fs = 16,22,05,24 kHz Layer I I Layer n, Layer III 2.4.2 Semantics for the Audio Bit stream Syntax 2.4.2.1 Audio Sequence General See ISOIIEC 11172-3,2.4.2.1. 2.4.2.2 Audio Frame See ISO/
16、iEC 11 172-3,2.4.2.2. 2.4.2.3 Header The first 32 bits (four bytes) are header information which is common to aU layers. syncword - See ISO/IEC 11 172-3,2.4.2.3. ID - One bit to indicate the ID of the algorithm. Equals 1 for ISOIEC 11172-3, O for extension to lower sampling frequencies. Layer - See
17、ISO/IEC 11 172-3,2.4.2.3. protection-bit - See ISOAEC 11 172-3,2.4.2.3. bitrate-index - Four bits to indicate the biuate. The all zero value indicates the free format condition, in which a fixed bitrate which does not need to be in the list can be used. Fixed means that a frame contains either N or
18、N+l slots, depending on the value of the padding bit. The bitrate-index is an index to a table, which is different for each layer. The bitrate-index indicates the total bitrate irrespective of the mode (stereo, joint-stereo, duaichannel, single-channel), according to the following table for Ibo. The
19、 decoder is not required to support bitrates higher than 256 kbids, 160 kbids, 160 kbids in respect to Layer I, II and III when in free format mode. 15 STD.BS1 BS EN ISOIIEC 13838-3-ENGL 1995 m 3b24bb7 0583320 428 ISO/JEC 13818-3:1995) sampling-frequency - Indicates the sampling frequency for Ibo, a
20、ccording to the following table. 10 11 reserved A reset of the audio decoder may be required to change the sampling rate. paddingbit - See ISOAEC 11172-3,2.4.2.3. Padding is necessary with a sampling frequency of 22,05 kHz. Padding may also be required in free format. private-bit - See ISOAEC 11172-
21、3,2.4.2.3. mode - See ISOLEC 11172-3,2.4.2.3. mode-extension - See ISOAEC 11172-3,2.4.2.3. copyright - See ISOAFC 11 172-3,2.4.2.3. originakopy - See ISOIIEC 11172-3,2.4.2.3. emphasis - See ISOLIEC 11172-3,2.4.2.3. 2.4.2.4 Error Check For Layer I and Layer II, see ISOAEC 11 172-3,2.4.2.4. For Layer
22、III, the bits used to calculate the error check are: for single channel mode, for other modes bits 1631 of the header bits 071 of audio-data bits O 135 of audio-data 2.4.2.5 Audio Data Layer I Se ISO/IEC 11 172-3,2.4.2.5. 2.4.2.6 Audio Data Layer II See ISOIIEC 11 172-3,2.4.2.6. 2.4.2.7 Audio Data L
23、ayer 111 See ISO/IEC 11 172-3,2.4.2.7 with the exception of a different definition of scalefac-compress. scalefaccompressch - Selects the number of bits used for the transmission of the scalefactors and sets or resets preflag. If prefag is set, the values of a table are added to the scaiefactors as described in ISODEC 11 172-3 (Table B.6 Annex B). 2.4.2.8 Ancillary Data See ISO/IEC 11 172-3,2.4.1.8.
