Skip to main content
MSF (MOQT Streaming Format, draft-ietf-moq-msf-01) defines how media content is organized, described, and delivered over the MoQ transport protocol. While MoQ itself provides the transport primitives — broadcasts, tracks, groups, and frames — MSF defines the standard format for describing what media is available and how to consume it.

​
Catalog

A catalog is a JSON document that describes the complete set of tracks available in a broadcast. Subscribers read the catalog to discover available media before opening individual subscriptions. A catalog describes:
  • Track identities — namespace and name for each track
  • Media parameters — codec, bitrate, resolution, sample rate, etc.
  • Packaging mode — how media data is packed into MoQ groups and frames (LOC, CMAF, media timeline, event timeline)
  • Content roles — video, audio, caption, subtitle, etc.
  • Dependencies — which tracks depend on other tracks (e.g., enhancement layers)
Catalogs are delivered as a reserved track (typically named "catalog") within the broadcast, so they can be subscribed to like any other track.

Catalog

Parse, validate, and inspect catalog snapshots

Catalog Delta

Incremental catalog updates

​
Timeline

MSF defines timeline records that map media timestamps to MoQ group/object locations:
  • Media Timeline — maps media presentation timestamps to [groupID, objectID] locations with wallclock times
  • Event Timeline — records events indexed by wallclock time, object location, or media time, carrying arbitrary JSON payloads

Timeline

Location, media timeline, and event timeline records

​
Broadcast

msf.Broadcast is an optional helper that integrates an MSF catalog with moqt.TrackHandler routing, managing the catalog snapshot and per-track handlers together.

Broadcast

Catalog-aware track handler routing