这是关于14496-3 音频标准的SBR部分
Contents
Amendment subpart 1 5
1 Terms and definitions........................................................................................................................... 5
2 Profiles 5
2.1 Audio object types................................................................................................................................ 5
2.2 AAC Profile and High Efficiency AAC Profile........................................................................................ 8
Amendment subpart 4 11
3 Scope 11
3.1 Technical overview............................................................................................................................. 11
4 Syntax 12
4.1.1 SBR Extension Payload for the audio object types AAC main, AAC SSR, AAC LC and AAC LTP........ 14
4.1.2 SBR Extension Payload for the audio object types ER AAC LC, ER AAC LTP and ER AAC LD............ 14
4.2 General information............................................................................................................................ 21
4.2.1 SBR Bitstream Element Definition....................................................................................................... 21
4.3 Error sensitivity category assignment for SBR..................................................................................... 24
5 SBR Tool 27
5.1 Tool description 27
5.2 Definitions 27
5.3 Decoding process................................................................................................................................ 30
5.3.1 Introduction 30
5.3.2 Frequency Band Tables...................................................................................................................... 30
5.3.3 Time / Frequency Grid........................................................................................................................ 35
5.3.4 Envelope and Noise Floor Decoding................................................................................................... 37
5.3.5 Dequantization and Stereo Decoding................................................................................................. 38
5.4 SBR tool filterbanks............................................................................................................................ 40
5.4.1 Analysis Filterbank.............................................................................................................................. 40
5.4.2 Synthesis Filterbank............................................................................................................................ 40
5.5 SBR tool overview.............................................................................................................................. 43
5.6 HF Generation 46
5.6.1 HF Generator 46
5.6.2 Limiter Frequency Band Table........................................................................................................... 48
5.7 HF Adjustment 51
5.7.1 Introduction 51
5.7.2 Mapping 51
5.7.3 Estimation of Current Envelope........................................................................................................... 53
5.7.4 Calculation of Levels of Additional HF Signal Components................................................................ 53
5.7.5 Calculation of Gain............................................................................................................................. 54
5.7.6 Assembling HF Signals....................................................................................................................... 55
5.8 Low complexity SBR tool.................................................................................................................... 58
5.8.1 Introduction 58
5.8.2 Low complexity SBR tool filterbanks.................................................................................................. 58
5.8.3 Aliasing detection............................................................................................................................... 61
5.8.4 Modification of the energy calculation................................................................................................ 65
5.8.5 Aliasing reduction............................................................................................................................... 65
1.A Annex A (normative) Normative Tables.............................................................................................. 68
1.A.1 SBR Huffman Tables........................................................................................................................... 68
1.A.1.1 Miscellaneous SBR Tables................................................................................................................ 75
1.B Annex B (informative) Encoder Tools.................................................................................................. 84
1.B.1 Informative SBR Encoder Description................................................................................................. 84
1.B.1.1 Encoder Overview............................................................................................................................. 84
1.B.1.2 Analysis Filterbank............................................................................................................................ 84
1.B.1.3 Time / Frequency Grid Generation................................................................................................... 86
1.B.1.4 Envelope Estimation......................................................................................................................... 86
1.B.1.5 Additional Control Parameters.......................................................................................................... 87
1.B.1.6 Data Quantization............................................................................................................................. 87
1.B.1.7 Envelope Coding............................................................................................................................... 88
1.B.1.8 Bitstream restrictions........................................................................................................................ 90
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