IMSC

IMSC stands for Interoperable Master Format. It is a standards-based approach for the interchange and delivery of high-quality media masters used in film, television, and streaming. The goal is to enable efficient exchange of completed programs and their variants across different regions and platforms by providing a common packaging and metadata model.

IMSC was developed within the broader IMF ecosystem with involvement from SMPTE and industry participants. It defines constrained profiles that specify how video, audio, subtitles, caption data, and related assets are packaged, versioned, and delivered as interoperable masters. The subtitle portion relies on TTML-based Timed Text, with profiles that support multiple languages, styling, region-specific rules, and synchronization with the associated media.

A key concept is the use of variants and versions to accommodate localization, edits, or different delivery requirements without duplicating entire masters. Metadata elements describe the composition, timing, languages, and conformance information to enable automated conforming, quality control, and playout.

IMSC is adopted in professional workflows across cinema, broadcast, and streaming ecosystems and is supported by tooling from post-production houses, distributors, and some hardware decoders. It complements IMF standards by providing a practical, interoperable approach to subtitle and caption exchange within a master package and is anchored to TTML and related SMPTE and ISO/IEC specifications.

See also IMF, TTML, SMPTE, and related ISO/IEC standards.