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1、 Reference number ISO/IEC 14496-3:2005/Amd.9:2008(E) ISO/IEC 2008 INTERNATIONAL STANDARD ISO/IEC 14496-3 Third edition 2005-12-01 AMENDMENT 9 2008-07-01 Information technology Coding of audio-visual objects Part 3: Audio AMENDMENT 9: Enhanced low delay AAC Technologies de linformation Codage des obj
2、ets audiovisuels Partie 3: Codage audio AMENDEMENT 9: Retard faible amlior AAC ISO/IEC 14496-3:2005/Amd.9:2008(E) PDF disclaimer This PDF file may contain embedded typefaces. In accordance with Adobes licensing policy, this file may be printed or viewed but shall not be edited unless the typefaces w
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7、w.iso.org Published in Switzerland ii ISO/IEC 2008 All rights reserved ISO/IEC 14496-3:2005/Amd.9:2008(E) ISO/IEC 2008 All rights reserved iii Foreword ISO (the International Organization for Standardization) and IEC (the International Electrotechnical Commission) form the specialized system for wor
8、ldwide standardization. National bodies that are members of ISO or IEC participate in the development of International Standards through technical committees established by the respective organization to deal with particular fields of technical activity. ISO and IEC technical committees collaborate
9、in fields of mutual interest. Other international organizations, governmental and non-governmental, in liaison with 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. International Standards are dr
10、afted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of the joint technical committee is to prepare International Standards. Draft International Standards adopted by the joint technical committee are circulated to national bodies for voting. Publication as an Int
11、ernational Standard requires approval by at least 75 % of the national bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO and IEC shall not be held responsible for identifying any or all such patent rights.
12、 Amendment 9 to ISO/IEC 14496-3:2005 was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology, Subcommittee SC 29, Coding of audio, picture, multimedia and hypermedia information. -,-,- ISO/IEC 14496-3:2005/Amd.9:2008(E) ISO/IEC 2008 All rights reserved 1 Information technolog
13、y Coding of audio-visual objects Part 3: Audio AMENDMENT 9: Enhanced low delay AAC In the following, changes in existing text and tables are highlighted by grey background. In 1.5.1.1, extend Table 1.1 with the following entries: Table 1.1 Audio Object Type definition based on Tools/Modules Object T
14、ype ID Audio Object Type gain control block switching window shapes - standard window shapes AAC LD Low Delay Window filterbank - standard filterbank - SSR TNS LTP intensity coupling frequency deomain prediction PNS MS SIAQ FSS upsampling filter tool quantisation samplingFrequencyIndex; 4 bslbf if (
15、 samplingFrequencyIndex = 0xf ) samplingFrequency; 24 uimsbf channelConfiguration; 4 bslbf sbrPresentFlag = -1; psPresentFlag = -1; if ( audioObjectType = 5 | audioObjectType = 29 ) extensionAudioObjectType = audioObjectType; sbrPresentFlag = 1; if ( audioObjectType = 29 ) psPresentFlag = 1; extensi
16、onSamplingFrequencyIndex; 4 uimsbf if ( extensionSamplingFrequencyIndex = 0xf ) extensionSamplingFrequency; 24 uimsbf audioObjectType = GetAudioObjectType(); else extensionAudioObjectType = 0; switch (audioObjectType) -,-,- ISO/IEC 14496-3:2005/Amd.9:2008(E) ISO/IEC 2008 All rights reserved 3 case 1
17、: case 2: case 3: case 4: case 6: case 7: case 17: case 19: case 20: case 21: case 22: case 23: GASpecificConfig(); break: case 8: CelpSpecificConfig(); break; case 9: HvxcSpecificConfig(); break: case 12: TTSSpecificConfig(); break; case 13: case 14: case 15: case 16: StructuredAudioSpecificConfig(
18、); break; case 24: ErrorResilientCelpSpecificConfig(); break; case 25: ErrorResilientHvxcSpecificConfig(); break; case 26: case 27: ParametricSpecificConfig(); break; case 28: SSCSpecificConfig(); break; case 32: case 33: case 34: MPEG_1_2_SpecificConfig(); break; case 35: DSTSpecificConfig(); break
19、; case 36: fillBits; 5 bslbf ALSSpecificConfig(); break; case 37: case 38: SLSSpecificConfig(); break; case 39: -,-,- ISO/IEC 14496-3:2005/Amd.9:2008(E) 4 ISO/IEC 2008 All rights reserved ELDSpecificConfig(channelConfiguration); break; default: /* reserved */ switch (audioObjectType) case 17: case 1
20、9: case 20: case 21: case 22: case 23: case 24: case 25: case 26: case 27: case 39: epConfig; 2 bslbf if ( epConfig = 2 | epConfig = 3 ) ErrorProtectionSpecificConfig(); if ( epConfig = 3 ) directMapping; 1 bslbf if ( ! directMapping ) /* tbd */ if ( extensionAudioObjectType != 5 11 bslbf if (syncEx
21、tensionType = 0x2b7) extensionAudioObjectType = GetAudioObjectType(); if ( extensionAudioObjectType = 5 ) sbrPresentFlag; 1 uimsbf if (sbrPresentFlag = 1) extensionSamplingFrequencyIndex; 4 uimsbf if ( extensionSamplingFrequencyIndex = 0xf ) extensionSamplingFrequency; 24 uimsbf if ( bits_to_decode(
22、) = 12 ) syncExtensionType; 11 bslbf if (syncExtensionType = 0x548) psPresentFlag; 1 uimsbf -,-,- ISO/IEC 14496-3:2005/Amd.9:2008(E) ISO/IEC 2008 All rights reserved 5 In 1.6.2.2.1, extend Table 1.15 “Audio Object Types” as follows: Table 1.15 Audio Object Types Object Type ID Audio Object Type defi
23、nition of elementary stream payloads and detailed syntax Mapping of audio payloads to access units and elementary streams 39 ER AAC ELD ISO/IEC 14496-3 subpart 4 see subclause 1.6.2.2.2.4 Add 1.6.2.2.4 with the title “ER AAC ELD“: 1.6.2.2.2 .4 ER AAC ELD The top level payload for ER AAC ELD is defin
24、ed in er_raw_data_block_eld(). All definitions mentioned in subclause 1.6.2.2.2.3 are also valid for this AOT. At the end of 1.6.5.1, add a sentence: “NOTE: None of these signaling methods described in this subclause is allowed for AAC ELD in order to signal the low delay sbr tool. For this case the
25、 ldSbrPresentFlag in the ELDSpecificConfig is to be used” Before 4.5, insert Tables AMD9.2 to AMD9.8: Table AMD9.2 Syntax of top level payload for audio object types ER AAC ELD (er_raw_data_block_eld() Syntax No. of bits Mnemonic er_raw_data_block_eld(channelConfiguration) switch(channelConfiguratio
26、n) case 1: single_channel_element_eld(); break; case 2: channel_pair_element_eld (); break; case 3: single_channel_element_eld (); channel_pair_element_eld (); break; case 4: single_channel_element_eld (); channel_pair_element_eld (); single_channel_element_eld (); break; ISO/IEC 14496-3:2005/Amd.9:
27、2008(E) 6 ISO/IEC 2008 All rights reserved case 5: single_channel_element_eld (); channel_pair_element_eld (); channel_pair_element_eld (); break; case 6: single_channel_element_eld (); channel_pair_element_eld (); channel_pair_element_eld (); lfe_channel_element_eld (); break; case 7: single_channe
28、l_element_eld (); channel_pair_element_eld (); channel_pair_element_eld (); channel_pair_element_eld (); lfe_channel_element_eld (); break; default: /* reserved */ break; if (ldSbrPresentFlag) er_low_delay_sbr_block(channelConfiguration); cnt = bits_to_decode() / 8; while ( cnt = 1 ) cnt -= extensio
29、n_payload(cnt); byte_alignment(); Table AMD9.3 Syntax of single_channel_element_eld() Syntax No. of bitsMnemonic single_channel_element_eld() individual_channel_stream_eld (0); Table AMD9.4 Syntax of lfe_channel_element_eld() Syntax No. of bitsMnemonic lfe_channel_element_eld() individual_channel_st
30、ream_eld (0); -,-,- ISO/IEC 14496-3:2005/Amd.9:2008(E) ISO/IEC 2008 All rights reserved 7 Table AMD9.5 Syntax of channel_pair_element_eld() Syntax No. of bits Mnemonic channel_pair_element_eld() common_window = 1; max_sfb; 6 uimsbf ms_mask_present; 2 uimsbf if ( ms_mask_present = 1 ) for (sfb = 0; s
31、fb 1) bs_num_noisech = 2; Else bs_num_noisech = 1; Note 1: bs_num_env is restricted according to subclause 4.6.18.3. Note 2: the Table LD_Envelope_Table is given in Table AMD9.11 4.6.19.3.3 Calculation of )(ltE (changes to 4.6.18.3.3) in case bs_frame_class = LD_TRAN: )(0 1_)( )( 0)0( EE EE E Llforl
32、positiontransientbsbleEnvelopeTaLDlt SlotsnumberTimeLt t += = = 4.6.19.3.4 Calculation of A l (changes to 4.6.18.7.2) in case bs_frame_class = LD_TRAN: 4_positiontransientbsbleEnvelopeTaLDlA= ISO/IEC 14496-3:2005/Amd.9:2008(E) 14 ISO/IEC 2008 All rights reserved 4.6.19.3.5 Envelope Lookup Table Tabl
33、e AMD9.11 Lookup Table for LD_Envelope_Table (bs_transient_position) bs_transient_position num_envelopesborder1border2transientIdx 0 2 4 - 0 1 2 5 - 0 2 3 2 6 1 3 3 3 7 1 4 3 4 8 1 5 3 5 9 1 6 3 6 10 1 7 3 7 11 1 8 3 8 12 1 9 3 9 13 1 10* 3/2 10 14/- 1 11 2 11 - 1 12 2 12 - 1 13 2 13 - 1 14 2 14 - 1
34、 15 2 15 - 1 * in case of AAC frame = 480 use second Table entry 4.6.19.4 Low Delay SBR Filterbank (changes to 4.6.18.4) Instead of subclause 4.6.18.4, use the description below for filterbank processing. Note, that basically the processing descibed in the flowcharts Figure 4.41, 4.42, 4.43, 4.50, 4
35、.51, 4.52 is similar to the processing of the low-delay filterbank. Only the windowing and the modulation differ. 4.6.19.4.1 Analysis filterbank Shift the samples in the array x by 32 positions. The oldest 32 samples are discarded and 32 new samples are stored in positions 0 to 31. Multiply the samp
36、les of array x by the coefficient of window ci. The window coefficients ci are obtained by linear interpolation of the coefficients c, i.e. through the equation 3200,)2() 12( 2 1 )(+=iicicici The window coefficients of c can be found in Table AMD9.17. Sum the samples according to the formula in the
37、flowchart in Figure 4.41 to create the 64-element array u. -,-,- ISO/IEC 14496-3:2005/Amd.9:2008(E) ISO/IEC 2008 All rights reserved 15 Calculate 32 new subband samples by the matrix operation Mu, where + = 640 320 , 64 )952()5 . 0( exp2),( n k nki nk In the equation, exp() denotes the complex expon
38、ential function and i is the imaginary unit. 4.6.19.4.2 Synthesis filterbank Shift the samples in the array v by 128 positions. The oldest 128 samples are discarded. The 64 new complex-valued subband samples are multiplied by the matrix N, where + = 1280 640 , 128 )632()5 . 0( exp 64 1 ),( n k nki n
39、k In the equation, exp() denotes the complex exponential function and i is the imaginary unit. The real part of the output from this operation is stored in the positions 0 to 127 of array v. Extract samples from v according to the flowchart in Figure 4.42 to create the 640-element array g. Multiply
40、the samples of array g by window c to produce array w. The window coefficients of c can be found in Table AMD9.17. Calculate 64 new output samples by summation of samples from array w according to the last step in the flowchart of in Figure 4.42 4.6.19.4.3 Downsampled synthesis filterbank Shift the
41、samples in the array v by 64 positions. The oldest 64 samples are discarded. The 32 new complex-valued subband samples are multiplied by the matrix N, where + = 640 320 , 64 )312()5 . 0( exp 64 1 ),( n k nki nk In the equation, exp() denotes the complex exponential function and i is the imaginary un
42、it. The real part of the output from this operation is stored in the positions 0 to 63 of array v. Extract samples from v according to the flowchart in Figure 4.43 to create the 320-element array g. Multiply the samples of array g by the coefficient of window ci to produce array w. The window coeffi
43、cients ci are obtained by linear interpolation of the coefficients c, i.e. through the equation 3200,)2() 12( 2 1 )(+=iicicici The window coefficients of c can be found in Table AMD9.17. Calculate 32 new output samples by summation of samples from array w according to the last step in the flowchart
44、of Figure 4.43 -,-,- ISO/IEC 14496-3:2005/Amd.9:2008(E) 16 ISO/IEC 2008 All rights reserved 4.6.19.5 Low Power SBR Filterbank (4.6.18.8.2) 4.6.19.5.1 Real-valued analysis filterbank Shift the samples in the array x by 32 positions. The oldest 32 samples are discarded and 32 new samples are stored in
45、 positions 0 to 31. Multiply the samples of array x by the coefficient of window ci. The window coefficients ci are obtained by linear interpolation of the coefficients c, i.e. through the equation 3200,)2() 12( 2 1 )(+=iicicici The window coefficients of c can be found in Table Table AMD9.17. Sum t
46、he samples according to the formula in the flowchart to create the 64-element array u. Calculate new 32 subband samples by the matrix operation Mru, where + = 640 320 , 64 )952()5 . 0( cos2),( n k nk nk r 4.6.19.5.2 Real-valued synthesis filterbank Shift the samples in the array v by 128 positions.
47、The oldest 128 samples are discarded. The 64 new subband samples are multiplied by the matrix Nr, where + = 1280 640 , 128 )632()5 . 0( cos 32 1 ),( n k nk nk r The output from this operation is stored in the positions 0 to 127 of array v. Extract samples from v according to the flowchart in Figure 4.50 to create the 640-