ISO/IEC 23090-4:2025

Overview

ISO/IEC 23090-4:2025 - MPEG‑I immersive audio - specifies technologies for real‑time, interactive rendering of immersive audio in virtual and augmented reality environments while allowing 6DoF (six degrees of freedom) movement. The standard defines metadata models and a bitstream syntax for efficient storage and streaming of immersive audio content, plus a renderer framework to realize spatial audio effects in real time.

Key Topics and Requirements

• Real‑time interactive rendering: Support for dynamic user movement and viewpoint changes within an audio scene (6DoF).
• Metadata and bitstream: Defined metadata elements and a transport syntax (including MHAS) to enable streaming and storage with efficient parsing and rendering.
• Renderer architecture: A modular renderer with defined payload types and data structures (e.g., directivity, diffraction, voxel, early reflections, reverberation, granular, RasterMap, portal, dispersion).
• Renderer stages and workflows: Comprehensive stages for effects activation, acoustic environment assignment, granular synthesis, reverberation, portals, occlusion/diffraction and early reflections, plus metadata culling and consolidation.
• Spatialization: Built‑in binaural spatializer and adaptive loudspeaker rendering methods for headphone and multichannel playback.
• Utilities and safeguards: Limiter specification, equalization, and interfaces for audio utilization reporting to manage loudness and resource use.
• Profiles and encoder guidance: Informative annexes describe encoder modules, scene configuration, metadata creation and recommended default presets for acoustic environments.

Applications

• VR/AR platforms and game engines that need realistic, interactive spatial audio with user movement.
• Streaming services and content creators delivering immersive audio experiences over networks (efficient bitstream and metadata).
• Audio middleware, SDKs and renderer implementations for headphones, headphones+head‑tracking, and adaptive loudspeaker arrays.
• Encoders and authoring tools producing immersive audio scenes with metadata for real‑time playback.
• Research and development in spatial audio, acoustic simulation and real‑time audio rendering.

Who Would Use This Standard

• Audio engine developers, VR/AR system architects, and game studios
• Codec and streaming implementers, broadcast engineers
• Headphone and loudspeaker manufacturers working on spatial rendering
• Standards bodies and interoperability testing labs

Related Standards

• Part of the ISO/IEC 23090 (MPEG‑I) series - complements other MPEG‑I parts that address coded representation of immersive media. Implementers should consider interoperability with other MPEG‑I components and transport/profile specifications.

Keywords: ISO/IEC 23090-4:2025, MPEG‑I immersive audio, immersive audio, 6DoF, spatial audio, metadata, bitstream, MHAS, renderer, binaural, adaptive loudspeaker, VR audio.