1、Information technology MPEG audio technologies Part 3: Unified speech and audio coding AMENDMENT 3: Support of MPEG-D DRC, audio pre-roll and immediate play- out frame Technologies de linformation Technologies audio MPEG Partie 3: Discours unifi et codage audio AMENDEMENT 3: Support de DRC MPEG-D, m
2、essage prliminaire audio et cadre de lecture immdiat INTERNATIONAL STANDARD ISO/IEC 23003-3 First edition 2012-04-01 Reference number ISO/IEC 23003-3:2012/Amd.3:2016(E) AMENDMENT 3 2016-08-01 ISO/IEC 2016 ii ISO/IEC 2016 All rights reserved COPYRIGHT PROTECTED DOCUMENT ISO/IEC 2016, Published in Swi
3、tzerland All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission. Permission can be
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5、23003-3:2012/Amd.3:2016(E) Foreword ISO (the International Organization for Standardization) and IEC (the International Electrotechnical Commission) form the specialized system for worldwide standardization. National bodies that are members of ISO or IEC participate in the development of Internation
6、al Standards through technical committees established by the respective organization to deal with particular fields of technical activity. ISO and IEC technical committees collaborate in fields of mutual interest. Other international organizations, governmental and non-governmental, in liaison with
7、ISO and IEC, also take part in the work. In the field of information technology, ISO and IEC have established a joint technical committee, ISO/IEC JTC 1. The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part 1. In pa
8、rticular the different approval criteria needed for the different types of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives). Attention is drawn to the possibility that some of the elements o
9、f this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any patent rights identified during the development of the document will be in the Introduction and/or on the ISO list of patent declarations received (see
10、 www.iso.org/patents). Any trade name used in this document is information given for the convenience of users and does not constitute an endorsement. For an explanation on the meaning of ISO specific terms and expressions related to conformit y assessment, as well as information about ISOs adherence
11、 to the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following URL: www.iso.org/iso/foreword.html. Amendment 3 to ISO/IEC 23003-3:2012 was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology, Subcommittee SC 29, Coding of audio, p
12、icture, multimedia and hypermedia information. ISO/IEC 2016 All rights reserved iii Information technology MPEG audio technologies Part 3: Unified speech and audio coding AMENDMENT 3: Support of MPEG-D DRC, audio pre-roll and immediate play-out frame Page 1, Normative references Add the following re
13、ference: ISO/IEC 23003-4, Information technology MPEG audio technologies Part 4: Dynamic Range Control Page 4, 4.4 Add new subclause at the end of 4.4: 4.4.1 Decoder behaviour 4.4.1.1 General decoding process The decoder shall operate in such a way that the decoding of one access unit shall always a
14、nd immediately produce one full composition unit of audio signal data (one audio frame with outputFrameLength number of samples). The decoder shall not discard any audio samples. In particular the decoder shall make no assumptions about encoder delay and shall also not attempt to compensate assumed
15、encoder processing delay by removing audio samples from the composition unit buffer. Discarding of audio samples due to the presence of an EditListBox as described in Annex F is not part of the normative USAC decoder but shall be applied by the MPEG-4 Systems infrastructure. 4.4.1.2 Initialization a
16、nd re-initialization of the USAC decoder Upon (re-) initialization all decoder internal signal buffers shall be set to zero. Due to the initialized state of the decoder internal buffers, the decoder output may contain “start-up samples” when decoding the first access units of a given compressed data
17、 stream. These start-up samples are samples that do not have a direct relation to the audio input data and are typically zero-valued and may be discarded by the Systems infrastructure. The number of start-up samples to be discarded may for example be transmitted by means of the media_time field in t
18、he EditListbox in an ISO Base Media file format environment. Note that this must be done by the encoder. If a given USAC decoder implementation produces more than the minimum number of start-up samples (i.e. it creates additional decoder delay), the number of additional samples must be reported by t
19、he decoder to the Systems infrastructure. Systems infrastructure shall then correctly apply delay compensation or time-alignment. ISO/IEC 23003-3:2012/Amd.3:2016(E) ISO 2016 All rights reserved 1 ISO/IEC 23003-3:2012/Amd.3:2016(E) 4.4.1.3 Decoding process of access unit with audio pre-roll The decod
20、ing process of access units with embedded audio pre-roll frames is identical to the above description. The presence of audio pre-roll in the first access unit prepares the decoder internal signal buffers. This allows an encoder to produce a compressed data stream, that will cause the decoder output
21、buffer to contain less or no start-up samples. The decoding description when changing from one configuration to another while employing audio pre-roll is described in 7.18.3.3. If a given decoder implementation produces additional start-up samples (additional decoder delay), then the flushing of the
22、 old configuration (FlushDecoder() shall be increased by the same amount of samples. The signal crossfade must be delayed accordingly. The decoder must ensure that the number of additional start-up samples (additional decoder delay) does not change when switching to another stream in the adaptation
23、set. Page 11, 4.5.3 Add the following paragraph at the end of 4.5.3: Furthermore the following requirements apply: The number of pre-roll frames, numPreRollFrames, in an AudioPreRoll() extension payload shall not exceed 3. Decoders conforming to the Baseline USAC profile shall support the full decod
24、ing and correct handling of the AudioPreRoll() extension. NOTE The number of pre-roll frames required for seamless operation of the audio codec may be lower than the above mentioned number. See B.26 for encoder implementation guide lines. Page 12, Clause 4 Add new subclause at the end of Clause 4: 4
25、.6 Combination of USAC with MPEG-D DRC The output of the USAC decoder can be further processed by MPEG-D DRC (ISO/IEC 23003-4). If the SBR tool in USAC is active, a USAC decoder can typically be efficiently combined with a subsequent MPEG-D DRC decoder by connecting them in the QMF domain in the sam
26、e way as it is described in ISO/IEC 23003- 4. If a connection in the QMF domain is not possible they shall be connected in the time domain. The MPEG-D DRC payload shall be embedded into a USAC bitstream by means of the usacExtElement mechanism, with usacExtElementType of type ID_EXT_ELE_UNI_DRC. The
27、 loudness metadata shall be embedded by means of the usacConfigExt mechanism with usacConfigExtType of type ID_CONFIG_ EXT_LOUDNESS_INFO. The time-alignment between the USAC data and the MPEG-D DRC data assumes the most efficient connection between the USAC decoder and the MPEG-D DRC decoder. If the
28、 SBR tool in USAC is active, the most efficient connection is in the QMF domain. Otherwise, the most efficient connection is in the time domain. The DRC tool is operated in regular delay mode and the DRC frame size has the same duration as the USAC frame size. The same holds for the DRC sampling rat
29、e, which is synchronized to the USAC sampling rate.2 ISO 2016 All rights reserved ISO/IEC 23003-3:2012/Amd.3:2016(E) The time resolution of the DRC tool is specified by deltaTmin in units of the audio sample interval. It is calculated as specified in ISO/IEC 23003-4. Specific values are provided her
30、e as examples based on the following formula: = M The applicable exponent M is found by looking up the audio sample rate range that fulfils: Table AMD3.1 Lookup table for the exponent M fs,min Hz fs,max Hz M 8000 16000 3 16000 32000 4 32000 64000 5 64000 128000 6 Given the codec frame size N Codec(=
31、outputFrameLength), the DRC frame size in units of DRC samples at a rate of deltaTmin is: 2 For USAC, MPEG-D DRC offers mandatory decoding capability of up to four DRC subbands using the time-domain DRC filter bank. More DRC subbands can be supported by operating in the QMF-domain. DRC sets that con
32、tain more than four DRC subbands must contain gain sequences that are all aligned with the QMF-domain used for SBR. If the SBR tool in USAC is active, MPEG-D DRC shall always operate in the QMF-domain. The gain sequences are all aligned with the QMF domain in that case. If no additional filter bank
33、is required for the application of multiband DRC gains, MPEG-D DRC doesnt introduce any additional decoding delay. The drcLocation parameter shall be encoded according to Table AMD3.2. Table AMD3.2 Encoding of drcLocation parameter drcLocation n Payload 1 uniDrcConfig() / uniDrcGain() (see ISO/IEC 2
34、3003-4) 2 reserved 3 reserved 4 reserved ISO 2016 All rights reserved 3 ISO/IEC 23003-3:2012/Amd.3:2016(E) Page 16, Table 14 Replace Table 14 with the following table: Table 14 Syntax of UsacExtElementConfig() Syntax No. of bits Mnemonic UsacExtElementConfig() usacExtElementType = escapedValue(4,8,1
35、6);usacExtElementConfigLength = escapedValue(4,8,16);usacExtElementDefaultLengthPresent; 1 uimsbfif (usacExtElementDefaultLengthPresent) usacExtElementDefaultLength = escapedValue(8,16,0) + 1; else usacExtElementDefaultLength = 0;usacExtElementPayloadFrag; 1 uimsbfswitch (usacExtElementType) case ID
36、_EXT_ELE_FILL:break;case ID_EXT_ELE_MPEGS:SpatialSpecificConfig();break;case ID_EXT_ELE_SAOC:SaocSpecificConfig();break;case ID_EXT_ELE_AUDIOPREROLL:/* No configuration element */break;case ID_EXT_ELE_UNI_DRC:uniDrcConfig();break;default: NOTEwhile (usacExtElementConfigLength-) tmp; 8 uimsbfbreak; N
37、OTE: The default entry for the usacExtElementType is used for unknown extElementTypes so that legacy decoders can cope with future extensions.4 ISO 2016 All rights reserved ISO/IEC 23003-3:2012/Amd.3:2016(E) Page 16, Table 15 Replace Table 15 with the following table: Table 15 Syntax of UsacConfigEx
38、tension() Syntax No. of bits Mnemonic UsacConfigExtension() numConfigExtensions = escapedValue(2,4,8) + 1;for (confExtIdx=0; confExtIdxnumConfigExtensions; confExtIdx+) usacConfigExtTypeconfExtIdx = escapedValue(4,8,16);usacConfigExtLengthconfExtIdx = escapedValue(4,8,16);switch (usacConfigExtTypeco
39、nfExtIdx) case ID_CONFIG_EXT_FILL:while (usacConfigExtLengthconfExtIdx-) fill_bytei; /* should be 10100101 */ 8 uimsbfbreak;case ID_CONFIG_EXT_LOUDNESS_INFO:loudnessInfoSet()break;default:while (usacConfigExtLengthconfExtIdx-) tmp; 8 uimsbfbreak; ISO 2016 All rights reserved 5 ISO/IEC 23003-3:2012/A
40、md.3:2016(E) Page 50, Clause 5 Add new subclause at the end of Clause 5: 5.3.5 Payload of extension elements Table AMD3.3 Syntax of AudioPreRoll() Syntax No. of bits Mnemonic AudioPreRoll() configLen = escapedValue(4,4,8); 416Config() 8*configLenapplyCrossfade;reserved; 1 1 bool boolnumPreRollFrames
41、 = escapedValue(2,4,0); 26for (frameIdx=0; frameIdx numPreRollFrames; +frameIdx) auLen = escapedValued(16,16,0) 1632 uimsbfAccessUnit() 8*auLen Page 58, Table 73 Replace Table 73 with the following table: Table 73 Value of usacExtElementType usacExtElementType Value ID_EXT_ELE_FILL 0 ID_EXT_ELE_MPEG
42、S 1 ID_EXT_ELE_SAOC 2 ID_EXT_ELE_AUDIOPREROLL 3 ID_EXT_ELE_UNI_DRC 4 /* reserved for ISO use */ 5-127 /* reserved for use outside of ISO scope */ 128 and higher N OTE A p p li ca ti o n - sp ecifi c usa c ExtEl e m e n tT yp e val u es are man da ted to b e in th e sp a c e reserved for use outside
43、of ISO scope. These are skipped by a decoder as a minimum of structure is required by the decoder to skip these extensions.6 ISO 2016 All rights reserved ISO/IEC 23003-3:2012/Amd.3:2016(E) Page 58, Table 74 Replace Table 74 with the following table: Table 74 Value of usacConfigExtType usacConfigExtT
44、ype Value ID_CONFIG_EXT_FILL 0 /* reserved for ISO use */ 1 ID_CONFIG_EXT_LOUDNESS_INFO 2 /* reserved for ISO use */ 3-127 /* reserved for use outside of ISO scope */ 128 and higher Page 64, Table 81 Replace Table 81 with the following table: Table 81 Interpretation of data blocks for USAC extension
45、 payload decoding usacExtElementType The concatenated usacExtElementSegment- Data represents: ID_EXT_ELE_FIL Series of fill_byte ID_EXT_ELE_MPEGS SpatialFrame() ID_EXT_ELE_SAOC SaocFrame() ID_EXT_ELE_AUDIOPREROLL AudioPreRoll() ID_EXT_ELE_UNI_DRC uniDrcGain() as defined in ISO/IEC 23003-4 unknown un
46、known data. The data block shall be discarded. Page 210, Clause 7 Add new subclause at the end of Clause 7: 7.18 Audio Pre-Roll 7.18.1 General The AudioPreRoll() syntax element is used to transmit audio information of previous frames along with the data of the present frame. The additional audio dat
47、a can be used to compensate the decoder startup delay (pre-roll), thus enabling random access at stream access points (SAP) that make use of AudioPreRoll(). A UsacExtElement() with the usacExtElementType of ID_EXT_ELE_AUDIOPREROLL shall be used to transmit the AudioPreRoll(). 7.18.2 Semantics config
48、Len Size of the configuration syntax element in bytes. Config() The decoder configuration syntax element. In the context of this standard this shall be the UsacConfig() as defined in 5.2. The Config() field may be transmit- ted to be able to respond to changes in the audio configuration (e.g. switch
49、ing of streams). applyCrossfade If this flag is set to 1, a linear crossfade shall be applied in case of configuration change, as defined in 7.18.3.3. ISO 2016 All rights reserved 7 ISO/IEC 23003-3:2012/Amd.3:2016(E) reserved reserved bit shall be zero. numPreRollFrames The number of pre-roll access units (AUs) transmitted as audio pre-roll data. The reasonabl
