Overview
ISO/IEC 23091-2:2025 - "Information technology - Coding‑independent code points - Part 2: Video" defines a centralized set of code points and fields that describe properties of video and still‑image representations independent of compression formats and bit rates. Intended as a universal reference, this third edition harmonizes metadata used across codecs, containers, encoders and decoders so that interpretation of decoded samples (or the characteristics of pre‑encoded signals) is consistent and unambiguous.
Key Topics and Requirements
The standard specifies code points and conventions for video signal description, including:
- Colour primaries - identification of colour reproduction primaries used for a signal.
- Transfer characteristics - transfer functions / electro‑optical/optical‑electrical mappings for correct display.
- Matrix coefficients - definitions for YCbCr / RGB conversion matrices.
- Video frame packing type - how frames and fields are arranged (including top/bottom field semantics).
- Packed video content interpretation - semantics for multi‑plane and packed sample layouts.
- Sample aspect ratio (SAR) - numeric descriptions of pixel aspect ratio.
- Chroma 4:2:0 sample location type - chroma sample placement rules and conventions.
Additional normative references and conventions (e.g., ISO/CIE 11664‑1 Colorimetry) and coding conventions (arithmetic, bit‑wise operators, numbering starting at 0) are included to ensure unambiguous implementation. The document also defines principles for code‑point assignment, referencing, and the use of reserved/unspecified values.
Notable editorial and technical updates in this edition include corrections and additions to colour representations and newly specified identifiers (for example, additions from SMPTE and YCoCg‑R variants), and alignment with ITU‑T Recommendation H.273.
Practical Applications and Users
ISO/IEC 23091-2:2025 is used to:
- Ensure interoperability between codecs, containers, players and displays by providing canonical metadata values.
- Provide consistent metadata for streaming platforms, broadcast systems, and content distribution chains.
- Guide encoder and decoder implementers and file format designers on how to represent signal properties independently of codec specifics.
- Support color scientists, imaging software developers, device manufacturers, and standards authors who need a stable, central registry of video code points.
Typical users:
- Codec implementers and codec spec authors
- Container/transport format designers (MP4, ISOBMFF, MPEG container profiles)
- Broadcasters and OTT streaming engineers
- Video processing and color management software vendors
Related Standards
- ISO/IEC 23091 (series) - other parts addressing coding‑independent code points
- ITU‑T Rec. H.273 - collaborative reference for this part
- ISO/CIE 11664‑1 - Colorimetry (normative reference)
- IEC 61966‑2‑1 - referenced colour representation material
By centralizing video code points, ISO/IEC 23091-2:2025 reduces conflicting assignments, simplifies maintenance across specifications, and improves robust, long‑term interoperability for video metadata and signal interpretation.
