Overview
ISO/IEC 23001-12:2018 - Sample variants defines a framework for representing and transporting sample variants in two pervasive container/system formats: the ISO Base Media File Format (ISOBMFF, ISO/IEC 14496-12) and the MPEG-2 Transport Stream (MPEG-2 TS, ISO/IEC 13818-1). A sample variant is an assembled media sample that replaces an original sample and can include alternate samples or alternate protection schemes. The standard specifies metadata, carriage mechanisms, and processing models to enable interoperable creation, delivery and extraction of these variants.
Key technical topics and requirements
- Variant data model: Definitions for variant constructors, variant byte ranges, variant media data, and variant data stream that describe how sample variants are assembled and described.
- Carriage in ISOBMFF and MPEG-2 TS: Rules for mapping variant streams and metadata into ISOBMFF tracks and MPEG-2 TS packetized streams, including associations between variant metadata and media data.
- Metadata syntax and semantics: Structures for variant constructor lists and variant constructor metadata; includes syntax/semantics requirements for conveying how to build sample variants.
- Encryption and protection: Support for encryption scenarios including Common Encryption (CENC) and MPEG-2 TS common encryption (CETS), handling of media keys, KIDs, and double-encrypted byte ranges.
- Processor and extractor models: Logical models for variant processors and sample-variant media data stream extractors that specify how implementations should assemble and output compliant media streams.
- Support for multiple alternates: Provisions for representing multiple alternate samples and multiple alternate protection schemes (notable enhancements in the 2018 edition).
Practical applications and who uses this standard
ISO/IEC 23001-12 is targeted at implementers and stakeholders in digital media workflows that require flexible sample substitution or alternate content delivery:
- Media packagers and content preparation tools - to create files/streams that carry alternate samples or protection schemes.
- DRM providers and encryption modules - to manage keys, KIDs, and encrypted variant byte ranges in both file and TS environments.
- Streaming platforms and CDNs - to deliver bitstream variants for compatibility, backward compatibility, or targeted protection strategies.
- Broadcasters and cable/satellite system integrators - to carry variant metadata in MPEG-2 TS for legacy and hybrid delivery environments.
- Player and decoder developers - to implement variant processors and extractor logic to present the appropriate sample variant at playback.
Related standards
Keywords: ISO/IEC 23001-12, sample variants, ISOBMFF, MPEG-2 TS, variant data stream, variant constructor, variant byte range, CENC, CETS, media packaging, DRM, adaptive streaming.
