ISO IEC 23091-3-2018 PDF

Full title and description

Information technology — Coding-independent code points — Part 3: Audio. This international standard defines codec‑agnostic code points and fields to describe properties of audio signals (for example loudspeaker positions, loudness and peak levels, dynamic range compressor characteristics and related metadata) so that audio streams can be interpreted consistently across codecs, containers and delivery systems.

Abstract

ISO/IEC 23091-3:2018 specifies a set of coding‑independent code points for audio that describe signal characteristics both before encoding and after decoding. The standard covers definitions and encodings for loudspeaker indices and layouts, loudness metrics (e.g., LKFS/K-weighted measures), peak levels (sample and true peak), loudness ranges, and indices for dynamic range compressor (DRC) characteristics, together with rules for referencing and encoding these descriptors. These descriptors are intended to improve interoperability of metadata across codecs and systems and to support consistent loudness management and immersive audio rendering.

General information

• Status: Published.
• Publication date: April 2018 (first edition).
• Publisher: ISO/IEC (ISO and IEC joint standard, prepared by ISO/IEC JTC 1/SC 29).
• ICS / categories: 35.040.40 (audio, video and multimedia information coding).
• Edition / version: Edition 1 (2018). An amendment (ISO/IEC 23091-3:2018/Amd 1) providing additional content such as headphone support was published in 2022.
• Number of pages: 22 pages (main document).

Scope

Defines audio‑related coding‑independent code points and their usage and reference formats so that audio signal properties can be signalled independently of the codec or bit rate. The scope includes loudspeaker indices and positions, loudspeaker layout and channel configuration, loudness descriptors (program, anchor, momentary and short‑term values and ranges), sample and true peak levels, and DRC characteristic indices, together with principles for encoding, defaults and referencing of externally defined values. The intent is to provide interoperable metadata for broadcast, streaming, immersive audio and other workflows.

Key topics and requirements

• Definition of loudspeaker index and 3D loudspeaker positioning descriptors for multichannel and object‑based rendering.
• Specification of loudspeaker layout indices and channel configuration values to describe common playback setups.
• Standardized loudness descriptors (program loudness, anchor loudness, loudness range, short‑term and momentary loudness) using K‑weighted/LKFS conventions.
• Definitions for peak levels (sample peak and true peak) and metadata to support loudness/peak management workflows.
• Indexing of dynamic range compressor (DRC) characteristics and references to externally defined values and URN formats for stable referencing.
• Principles for code point encoding, defaults and applicability both pre‑encoder (source descriptors) and post‑decoder (rendering/processing descriptors).

Typical use and users

Used by audio codec designers, container and file format authors, broadcast and streaming engineers for loudness normalization, immersive audio system integrators and game audio engine developers, metadata and middleware vendors, and standards bodies implementing interoperable audio metadata. Typical applications include consistent loudness management, automated downmixing and level control, immersive rendering mapping, and providing a stable registry for audio descriptors referenced across specifications.

Related standards

This part (23091‑3) is one element of the Coding‑Independent Code Points (CICP) family (ISO/IEC 23091). It follows and complements other parts: Part 1 (systems) and Part 2 (video). The work continues and relates to ITU‑T H.273 for video signal type identification and to earlier MPEG system work such as ISO/IEC 23001‑8 (which was replaced by the 23091 parts). Implementers often use 23091 parts together when describing mixed audio/video workflows.

Keywords

Coding‑independent code points, CICP, audio metadata, loudness, LKFS, K‑weighted, true peak, sample peak, loudness range, loudspeaker layout, DRC, immersive audio, interoperability.

FAQ

Q: What is this standard?

A: ISO/IEC 23091-3:2018 is an international standard that defines codec‑agnostic code points and descriptors for audio signal properties, enabling consistent interpretation of audio metadata across codecs and systems.

Q: What does it cover?

A: It covers definitions and encodings for loudspeaker indices and positions, loudspeaker layouts and channel configurations, loudness metrics (program/anchor/short‑term/momentary), loudness range, peak (sample and true peak) levels, DRC characteristic indexing, and principles for encoding and referencing these code points.

Q: Who typically uses it?

A: Audio codec and container spec authors, broadcast/streaming engineers, immersive audio integrators, game and audio engine developers, metadata tool vendors and standards implementers who need format‑agnostic audio descriptors.

Q: Is it current or superseded?

A: The standard was published in April 2018 (first edition) and is published/active; it was amended in 2022 (ISO/IEC 23091-3:2018/Amd 1) to add material such as headphone support. It replaced earlier material in ISO/IEC 23001-8:2016 as part of the reorganization into the 23091 series. It is not listed as withdrawn or superseded as of the referenced publications.

Q: Is it part of a series?

A: Yes — ISO/IEC 23091 is a multi‑part suite (Coding‑independent code points). Part 1 addresses systems, Part 2 addresses video, Part 3 addresses audio (this document), and Part 4 provides guidance on usage for video signal type combinations. Implementers commonly use multiple parts together.

Q: What are the key keywords?

A: Key keywords include coding‑independent code points (CICP), audio metadata, loudness, LKFS, true peak, loudspeaker layout, DRC, immersive audio, interoperability.