ETSI TS 103 190-2 V1.2.1 (2018-02)

Digital Audio Compression (AC-4) Standard; Part 2: Immersive and personalized audio

RTS/JTC-043-2

General Information

• Status: Published
• Publication Date: 05-Feb-2018
• Technical Committee: BROADCAS - EBU/CENELEC/ETSI on Broadcasting
• Current Stage: 12 - Completion
• Due Date: 31-Jan-2018
• Completion Date: 06-Feb-2018

Standards Content (Sample)

ETSI TS 103 190-2 V1.2.1 (2018-02)






TECHNICAL SPECIFICATION
Digital Audio Compression (AC-4) Standard;
Part 2: Immersive and personalized audio

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2 ETSI TS 103 190-2 V1.2.1 (2018-02)



Reference
RTS/JTC-043-2
Keywords
audio, broadcasting, codec, content, digital,
distribution, object audio, personalization

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3 ETSI TS 103 190-2 V1.2.1 (2018-02)
Contents
Intellectual Property Rights . 17
Foreword . 17
Modal verbs terminology . 17
Introduction . 18
Motivation . 18
Structure of the present document . 18
1 Scope . 19
2 References . 19
2.1 Normative references . 19
2.2 Informative references . 19
3 Definitions, symbols, abbreviations and conventions . 20
3.1 Definitions . 20
3.2 Symbols . 25
3.3 Abbreviations . 25
3.4 Conventions . 26
4 Decoding the AC-4 bitstream . 28
4.1 Introduction . 28
4.2 Channels and objects . 28
4.3 Immersive audio . 29
4.4 Personalized Audio. 29
4.5 AC-4 bitstream . 30
4.5.1 Bitstream structure . 30
4.5.2 Data dependencies . 32
4.5.3 Frame rates. 33
4.6 Decoder compatibilities . 33
4.7 Decoding modes . 34
4.7.1 Introduction. 34
4.7.2 Full decoding mode . 34
4.7.3 Core decoding mode . 34
4.8 Decoding process . 35
4.8.1 Overview . 35
4.8.2 Selecting an audio presentation . 36
4.8.3 Decoding of substreams . 36
4.8.3.1 Introduction . 36
4.8.3.2 Identification of substream type . 37
4.8.3.3 Substream decoding overview . 39
4.8.3.4 Decoding of object properties . 40
4.8.3.4.1 Introduction . 40
4.8.3.4.2 Object audio metadata location . 40
4.8.3.5 Spectral frontends . 41
4.8.3.6 Stereo and multichannel processing (SMP) . 42
4.8.3.7 Inverse modified discrete cosine transformation (IMDCT) . 42
4.8.3.8 Simple coupling (S-CPL) . 42
4.8.3.9 QMF analysis . 42
4.8.3.10 Companding . 42
4.8.3.10.1 Introduction . 42
4.8.3.10.2 Channel audio substream . 42
4.8.3.10.3 Channel audio substream with an immersive channel element . 42
4.8.3.10.4 Object audio substream . 43
4.8.3.11 A-SPX . 43
4.8.3.11.1 Introduction . 43
4.8.3.11.2 Core decoding mode with ASPX_SCPL codec mode . 43
4.8.3.11.3 Full decoding mode with ASPX_SCPL codec mode . 44
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4 ETSI TS 103 190-2 V1.2.1 (2018-02)
4.8.3.12 Advanced joint channel coding (A-JCC) . 44
4.8.3.13 Advanced joint object coding (A-JOC) . 44
4.8.3.14 Advanced coupling (A-CPL) . 45
4.8.3.15 Dialogue enhancement . 45
4.8.3.16 Direct dynamic range control bitstream gain application . 46
4.8.3.17 Substream gain application for operation with associated audio. 46
4.8.3.18 Substream gain application for operation with dialogue substreams . 47
4.8.3.19 Substream rendering. 47
4.8.4 Mixing of decoded substreams . 47
4.8.5 Loudness correction . 48
4.8.5.1 Introduction . 48
4.8.5.2 Dialnorm location . 48
4.8.5.3 Downmix loudness correction . 48
4.8.5.4 Alternative audio presentation loudness correction . 49
4.8.5.5 Real-time loudness correction data . 49
4.8.6 Dynamic range control . 49
4.8.7 QMF synthesis . 49
4.8.8 Sample rate conversion . 50
5 Algorithmic details . 50
5.1 Bitstream processing . 50
5.1.1 Introduction. 50
5.1.2 Elementary stream multiplexing tool . 50
5.1.3 Efficient high frame rate mode . 52
5.2 Stereo and multichannel processing (SMP) for immersive audio . 54
5.2.1 Introduction. 54
5.2.2 Interface . 55
5.2.2.1 Inputs . 55
5.2.2.2 Outputs . 55
5.2.2.3 Controls . 55
5.2.3 Processing the immersive_channel_element . 55
5.2.3.1 Introduction . 55
5.2.3.2 immersive_codec_mode ∈ {SCPL, ASPX_SCPL, ASPX_ACPL_1} . 56
5.2.3.3 immersive_codec_mode = ASPX_ACPL_2 . 57
5.2.3.4 immersive_codec_mode = ASPX_AJCC . 57
5.2.4 Processing the 22_2_channel_element . 58
5.3 Simple coupling (S-CPL) . 58
5.3.1 Introduction. 58
5.3.2 Interface . 58
5.3.2.1 Inputs . 58
5.3.2.2 Outputs . 58
5.3.3 Reconstruction of the output channels . 59
5.3.3.1 Full decoding. 59
5.3.3.2 Core decoding . 59
5.4 Advanced spectral extension (A-SPX) postprocessing tool . 60
5.4.1 Introduction. 60
5.4.2 Interface . 60
5.4.2.1 Inputs . 60
5.4.2.2 Outputs . 60
5.4.3 Processing . 60
5.5 Advanced coupling (A-CPL) for immersive audio . 61
5.5.1 Introduction. 61
5.5.2 Processing the immersive_channel_element . 61
5.6 Advanced joint channel coding (A-JCC) . 63
5.6.1 Introduction. 63
5.6.2 Interface . 63
5.6.2.1 Inputs . 63
5.6.2.2 Outputs . 63
5.6.2.3 Controls . 63
5.6.3 Processing . 64
5.6.3.1 Parameter band to QMF subband mapping . 64
5.6.3.2 Differential decoding and dequantization . 64
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5 ETSI TS 103 190-2 V1.2.1 (2018-02)
5.6.3.3 Interpolation . 65
5.6.3.4 Decorrelator and transient ducker . 66
5.6.3.5 Reconstruction of the output channels . 67
5.6.3.5.1 Input channels . 67
5.6.3.5.2 A-JCC full decoding mode . 67
5.6.3.5.3 A-JCC core decoding mode . 71
5.7 Advanced joint object coding (A-JOC) . 74
5.7.1 Introduction. 74
5.7.2 Interface . 75
5.7.2.1 Inputs . 75
5.7.2.2 Outputs . 75
5.7.2.3 Controls . 75
5.7.3 Processing . 75
5.7.3.1 Parameter band to QMF subband mapping . 75
5.7.3.2 Differential decoding . 76
5.7.3.3 Dequantization . 77
5.7.3.4 Parameter time interpolation . 82
5.7.3.5 Decorrelator and transient ducker . 83
5.7.3.6 Signal reconstruction using matrices . 83
5.7.3.6.1 Processing . 83
5.7.3.6.2 Decorrelation input matrix. 86
5.8 Dialogue enhancement for immersive audio . 87
5.8.1 Introduction. 87
5.8.2 Processing . 87
5.8.2.1 Dialogue enhancement for core decoding of A-JCC coded 9.X.4 content . 87
5.8.2.2 Dialogue enhancement for core decoding of parametric A-CPL coded 9.X.4 content . 90
5.8.2.3 Dialogue enhancement for full decoding of A-JOC coded content . 91
5.8.2.4 Dialogue enhancement for core decoding of A-JOC coded content . 92
5.8.2.5 Dialogue enhancement for non A-JOC coded object audio content . 93
5.9 Object audio metadata timing . 93
5.9.1 Introduction. 93
5.9.2 Synchronization of object properties . 93
5.10 Rendering . 94
5.10.1 Introduction. 94
5.10.2 Channel audio renderer . 95
5.10.2.1 Introduction . 95
5.10.2.2 General rendering matrix . 96
5.10.2.3 Panning of a stereo or mono signal . 96
5.10.2.4 Substream downmix or upmix for full decoding . 97
5.10.2.5 Matrix coefficients for channel-based renderer for full decoding . 98
5.10.2.6 Substream downmix or upmix for core decoding . 101
5.10.2.7 Matrix coefficients for channel-based renderer for core decoding . 101
5.10.3 Intermediate spatial format rendering . 102
5.10.3.1 Introduction . 102
5.10.3.2 Conventions . 102
5.10.3.3 Interface . 103
5.10.3.3.1 Inputs . 103
5.10.3.3.2 Outputs . 103
5.10.3.3.3 Controls . 103
5.10.3.4 Processing . 103
5.11 Accurate frame rate control . 103
6 Bitstream syntax . 104
6.1 Introduction . 104
6.2 Syntax specification . 107
6.2.1 AC-4 frame info . 107
6.2.1.1 ac4_toc . 107
6.2.1.2 ac4_presentation_info . 108
6.2.1.3 ac4_presentation_v1_info . 109
6.2.1.4 frame_rate_fractions_info .
...