Overview
ISO/IEC 23001-18:2022 specifies the event message track format for the ISO base media file format (ISO‑BMFF). Part of the MPEG systems technologies family, this standard defines how aperiodic, timed metadata “events” are represented inside ISO‑BMFF tracks so they can be efficiently carried, multiplexed, de‑fragmented and accessed by media players and packagers.
Key keywords: ISO/IEC 23001-18:2022, event message track, ISO base media file format, MPEG, timed metadata, ISO‑BMFF.
Key topics and technical requirements
- EventMessageInstanceBox: New box type (emib) carried inside track samples. Contains fields such as presentation_time_delta (start relative to enclosing sample), event_duration, id, scheme_id_uri, value and message_data. This box maps DASH-style event semantics into track timeline.
- EventMessageEmptyBox: Empty box (emeb) used to signal intervals when no event is active; avoids zero‑length samples.
- Track and sample formats:
- Event message tracks use the 'meta' media handler and a null media header (timed metadata track).
- Samples use the EventMessageSampleEntry (four‑character code 'evte') and may include optional BitRateBox and SchemeIdListBox.
- Composition time offsets are disallowed (composition and decoding times are identical).
- SchemeIdListBox: Optional box listing event schemes present in the track, indicating completeness or “at least once” presence of schemes.
- Timing and processing constraints: Defines timing semantics (timescale from MediaHeaderBox), conversion procedures from DASHEventMessageBox to EventMessageInstanceBox, and guidance for client processing, multiplexing/de‑multiplexing, fragmentation and de‑fragmentation.
Practical applications and who uses it
- Streaming platform engineers and packager developers: to implement ISO‑BMFF/CMAF files containing timed events (e.g., ad markers, captions, interactive triggers).
- Player and client implementers: to parse event message tracks efficiently, seek to active events, and synchronize metadata with media timeline.
- Content distribution and CDN tooling: to support multiplexing, conversion and de‑fragmentation while preserving event timing and scheme metadata.
- Use cases include DASH/CMAF packaging workflows, interactive media triggers, timed metadata distribution, server‑side ad insertion signaling and analytics markers.
Related standards
ISO/IEC 23001-18:2022 enables interoperable carriage of event messages in ISO‑BMFF tracks, improving accessibility and processing for modern streaming and media applications.