ISO/IEC 23090-4:2025

International
Standard
ISO/IEC 23090-4
First edition
Information technology — Coded
2025-11
representation of immersive media —
Part 4:
MPEG-I immersive audio
Technologies de l'information — Représentation codée de média
immersifs —
Partie 4: Audio immersif MPEG-I
Reference number
© ISO/IEC 2025
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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Published in Switzerland
© ISO/IEC 2025 – All rights reserved
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Contents
Foreword .vi
Introduction . vii
1 Scope . 1
2 Normative references . 1
3 Terms, definitions and abbreviated terms . 1
3.1 Terms and definitions . 1
3.2 Mnemonics . 5
3.3 Abbreviated terms . 6
4 Overview . 7
5 MPEG-I immersive audio transport . 10
5.1 Overview . 10
5.2 Definitions . 11
5.3 MHAS syntax . 11
5.3.1 Audio stream . 11
5.3.2 Audio stream packet . 12
5.4 Semantics . 21
6 MPEG-I Immersive audio renderer . 31
6.1 Definitions . 31
6.2 Syntax . 31
6.2.1 General . 31
6.2.2 Generic codebook . 31
6.2.3 Directivity payloads syntax . 33
6.2.4 Diffraction payload syntax . 36
6.2.5 Voxel payload syntax . 42
6.2.6 Early reflection payload syntax . 47
6.2.7 Portal payload syntax . 50
6.2.8 Reverberation payload syntax . 52
6.2.9 Audio plus payload syntax. 54
6.2.10 Dispersion payload syntax . 54
6.2.11 Scene plus payload syntax . 54
6.2.12 Airflow payload syntax . 71
6.2.13 Granular payload syntax . 72
6.2.14 RasterMap payload syntax . 75
6.2.15 Support elements . 76
6.3 Data structure . 82
6.3.1 General . 82
6.3.2 Renderer payloads data structure . 82
6.3.3 Generic codebook . 134
6.4 Renderer framework . 134
6.4.1 Control workflow . 134
6.4.2 Rendering workflow . 146
6.5 Geometry data decompression . 159
6.5.1 General . 159
6.5.2 Metadata extraction . 159
6.5.3 Geometry . 160
6.5.4 Materials . 163
6.6 Renderer stages . 164
6.6.1 Effect activator . 164
6.6.2 Acoustic environment assignment . 165
© ISO/IEC 2025 – All rights reserved
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6.6.3 Granular synthesis . 167
6.6.4 Reverberation . 181
6.6.5 Portals . 242
6.6.6 Early reflections . 256
6.6.7 Airflow simulation . 270
6.6.8 DiscoverSESS . 277
6.6.9 Occlusion . 279
6.6.10 Diffraction . 284
6.6.11 Voxel-based occlusion and diffraction . 301
6.6.12 Multi-Path voxel-based diffraction with RasterMaps . 326
6.6.13 Voxel-based early reflections . 332
6.6.14 Metadata culling . 340
6.6.15 Heterogeneous extent . 345
6.6.16 Directivity . 374
6.6.17 Distance . 380
6.6.18 Directional focus . 390
6.6.19 Consolidation of render items . 391
6.6.20 Equalizer (EQ) . 398
6.6.21 Low-complexity early reflections (LC-ERs) . 399
6.6.22 Fade . 408
6.6.23 Single point higher order ambisonics (SP-HOA) . 411
6.6.24 Homogeneous extent . 416
6.6.25 Panner . 421
6.6.26 Multi-point higher order ambisonics (MP-HOA) . 428
6.6.27 Low-complexity MP-HOA . 468
6.7 Spatializer . 475
6.7.1 Binaural spatializer . 475
6.7.2 Adaptive loudspeaker rendering . 494
6.8 Limiter . 528
6.8.1 General . 528
6.8.2 Data elements and variables . 528
6.8.3 Description . 528
6.9 Interface for audio utilization information . 530
6.9.1 General . 530
6.9.2 Syntax and semantics of an interface for renderer audio utilization . 530
Annex A (normative) Tables and additional algorithm details . 531
A.1 Panner default output positions . 531
A.2 Adaptive loudspeaker rendering calibration guide . 531
A.3 RIR analysis: loudspeaker source directivity factor . 535
A.4 Default acoustic environment presets . 535
A.5 VR filter design initialization vector .
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