ISO/IEC 23091-2:2021

Overview

ISO/IEC 23091-2:2021 - Information technology - Coding‑independent code points - Part 2: Video - defines a centralized set of coding‑independent code points and fields that describe video (and still image) properties independently of compression formats and bit rates. The standard provides a uniform way to express metadata that characterizes how decoded (or pre‑encoded) video signals should be interpreted and presented, avoiding inconsistent or duplicated code‑point assignments across codec and container specifications.

Key technical topics and requirements

• Codec‑independent metadata: Code points are defined to express properties of video or still images without dependence on particular compression encodings or bit rates.
• Colour and appearance: Definitions include colour primaries, transfer characteristics (including corrections related to HLG/Rec. BT.2100), and matrix coefficients for converting between colour representations.
• Video geometry and sampling: Code points cover sample aspect ratio, chroma 4:2:0 sample location, chroma sampling grid alignment, and video frame packing types (for stereoscopic/packed formats).
• Content interpretation: Entries for packed video content interpretation and fields that indicate how decoded sample arrays should be treated or displayed.
• Formal conventions and referencing: The document specifies arithmetic, bit‑wise and assignment operator conventions, a reference format for identifiers and uniform resource name (URN) format, plus rules for application usage, encoding, defaults and externally defined values.
• Normative references: The standard references colorimetry and related documents (e.g., ISO/CIE 11664‑1) and aligns with companion international work (notably ITU‑T Rec. H.273).

Practical applications

• Ensuring consistent video metadata across codecs, containers, and transport formats for interoperable playback and processing.
• Enabling accurate color management and display mapping in broadcasting, streaming, post‑production, and digital cinema workflows.
• Helping encoder/decoder, container, and media player implementers unambiguously label content properties (colour space, transfer function, chroma layout, aspect ratio, packed formats).
• Facilitating content delivery platforms and AV systems to make automated rendering and transcoding decisions based on standardized, codec‑agnostic descriptors.

Who should use this standard

• Video codec and container developers
• Media player and display firmware engineers
• Broadcast and OTT system integrators
• Colorists, post‑production engineers, and mastering facilities
• Metadata schema designers and standards authors aiming for interoperable video metadata

Related standards

• ISO/IEC 23091 series (other parts covering image and related code points)
• ITU‑T Rec. H.273 (aligned drafting)
• Rec. ITU‑R BT.2100 (HDR transfer characteristics) and IEC 61966‑2‑1 (sYCC colour representations) - referenced in the document for transfer and colour definitions

Keywords: ISO/IEC 23091-2:2021, coding-independent code points, video metadata standard, color primaries, transfer characteristics, matrix coefficients, sample aspect ratio, chroma sampling.