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MOQT Streaming Format (MSF)

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draft-ietf-moq-msf-01 | Submitted 2026-06-02 | Datatracker draft-ietf-moq-msf-00 | 34 pages | Submitted 2026-01-19 | Expires 2026-07-23

Authors

Abstract

MSF defines the streaming format for delivering media over moq-transport. It enables delivery of moq-loc-compliant media through bitstream fragmentation into independently transmittable objects. Replaces the earlier draft-ietf-moq-warp.

MSF Packaging Extensions (Individual Drafts)

MSF defines an umbrella for codec/container packaging. As of May 2026, two extension drafts have been proposed:

  • [[moq-cmsf|CMSF (cmaf)]] (draft-ietf-moq-cmsf-00, WG) — CMAF-compliant packaging for MSF.
  • [[moq-msfts|MSFTS (m2ts)]] (draft-gregoire-moq-msfts-00, individual, submitted May 6 2026, 21 pages) — MPEG-2 Transport Stream Packaging for Media Over QUIC Transport. Authors: Paul Gregoire (Red5) and gwendal-simon (Synamedia). Registers the m2ts packaging value alongside CMSF; defines 10 m2ts-specific catalog fields including m2tsPacketSize (188 or 192 octets), m2tsProgramNumber, m2tsPmtPid, m2tsPcrPid, m2tsPsiInterval, m2tsRandomAccess, m2tsTimestampMode, m2tsScte35Pid, and initData (Base64-encoded init packets). First non-CMAF, non-LOC packaging extension — extends MSF to broadcast/contribution workflows where MPEG-2 TS remains the dominant container.

Key Features

  • Video and audio codec support: Compatible with LOC packaging
  • Catalog track: Describes content characteristics via catalog-format
  • Media and event timeline tracks: Temporal mapping for synchronization
  • Latency modes:
    • Real-time: <500ms
    • Interactive: 500-2500ms
    • Standard: >2500ms
  • adaptive-bitrate: ABR switching between time-synchronized tracks
  • Content encryption: Integration with moq-secure-objects

Structure

MSF defines how media is organized into MOQT tracks:

  1. Catalog track - JSON-based description of all available tracks
  2. Media tracks - Audio and video encoded with LOC
  3. Timeline tracks - Wall clock to media time mapping
  4. Event tracks - Timed metadata (SCTE-35, captions, etc.)

Incomplete Sections

The draft-00 marks several sections as ToDo:

  • Content protection details
  • Security considerations

Recent Highlights

Day-by-day WG/PR activity lives in the wiki log; this section keeps only durable milestones.

  • MSF draft-01 published — the first revision since -00, authored by Will Law (Akamai) and Suhas Nandakumar (Cisco); it absorbed Will Law’s large May 2026 editorial sprint. MSF’s revision cadence runs at roughly four months, consistent with it being a packaging-format rather than a wire-protocol spec.
  • Init-data design settled toward static inits with a typed, extensible representation — and landed in the draft text 2026-07-14. Experimental initTrack support was reverted (Issue #153): MSF keeps statically declared inits, a track with no initData MUST be self-initializing, and mid-stream parameter re-init relies on AVC3 self-initializing segments — which do not work for Safari/FairPlay pipelines that require avc1/hvc1 parameter sets in the sample entry. Init data then moved to a typed initDataList (named {id, type, data} references) and on to a dual Track + Object initData design: a stable Track property for steady-state init plus an Object property for synchronized mid-track changes (period switches, DRM key rotation) — the machinery LOCMAF and the LOCMAF→CMSF packaging plan rely on. Will Law merged this into the repo on 2026-07-14 as a three-PR cluster — PR #186 adds the Track + Object init-data properties (retiring initTrack, closing #153), PR #187 clarifies track cloning + delta-update rules (closing #183), PR #189 fixes typos — closing 183 just before MSF’s IETF-126 (Vienna, Friday) slot.
  • IANA early review + registry cleanup (2026-07-16/17). IANA’s Amanda Baber filed an early review of msf-01 ([IANA #1456080], part of a coordinated five-document sweep across the MoQ set — see moq-transport): §14.2 is missing a registry-group name / Change Controller / RFC 8126 designated-expert guidance, §14.3 references registries whose names don’t line up with transport-19, and §14.4 needs the Private-Use range upper limit clarified. Will Law opened a four-PR cleanup batch July 17 — PR #192 update normative references + IANA registries (closing the issue #191 IANA tracker), PR #193 catalog-object publishing guidelines, PR #194 add a data reserved track role, PR #195 event-timeline JSON-example fixes — the pre-WGLC registry hygiene ahead of Vienna. Two of these merged 2026-07-28 — #194 landing the new data reserved track role (+14/−13) and #193 the updated catalog-object publishing guidelines (+8/−2) — the first MSF-repo merges since the July-14 init-data cluster.
  • Mandatory baseline fields added. Responding to kixelated’s objection that “everything is optional,” MSF made sampleRate+channels required for audio and codec+width+height required for video, added Maximum GOP Duration / Maximum Group Duration / Average Bitrate properties, and redefined bitrate as a maximum — moving MSF from an optional-hints catalog toward a subscribe-decision oracle with a mandatory baseline.
  • Wall-clock concern resolved via targetBuffer. kixelated’s long-open “wall clock is problematic” issue (#150) was closed not by removing the wall clock but by adding a per-track targetBuffer property that gives subscribers explicit end-to-end buffer-depth guidance independent of publisher-clock accuracy.
  • Catalog compression resolved as publisher-decides. Compression is signaled via Track/Object Properties chosen by the publisher rather than a subscriber-negotiated Accept-Encoding; Vasiliev ruled Accept-Encoding incompatible with MoQ’s publisher-to-subscriber fan-out (data cannot flow subscriber→publisher on a shared relay path).
  • Two open design questions from kixelated remain -02 backlog inputs: sequence-aligned groups across tracks are seen as too restrictive (Issue #155) — proposal is to require shared PTS but loosen group alignment, letting CMSF keep alignment for HLS/DASH back-compat; and static-vs-dynamic catalogs (Issue #188) — static-track container formats (fMP4/FLV/MPEG-TS/HLS) cannot add or remove tracks mid-stream while MSF lets tracks change at any time, causing a consumer race condition, so kixelated asks MSF for a way to signal that no more tracks will be added/removed/modified.
  • Event-timeline formats have been spun out of MSF as three individual drafts. The direction predicted from the May 2026 PR #133 discussion — SCTE-35, WebVTT, and IMSC1 each becoming separate individual drafts under an MSF Event-Timeline-Extensions umbrella (parallel to the MSF Packaging Extensions pattern), with CEA-608/708 accessibility metadata staying in MSF — was realized on 2026-07-06 when Will Law (Akamai) + Suhas Nandakumar (Cisco) submitted all three as -00 individual drafts: draft-wilaw-moq-scte35-event-timeline-00 (“SCTE35 transmission over MSF Event Timeline”, 9 pp — binary + XML SCTE-35 ad/event signals over MSF Event Timeline tracks), draft-wilaw-moq-webvtt-msf-00 (“WebVTT Packaging for MOQT Streaming Format”, 8 pp — WebVTT cues packaged as JSON records on the event timeline), and draft-law-moq-imsc1-msf-00 (“IMSC1 Packaging for MOQT Streaming Format”, 8 pp — IMSC1 captions with a simplified JSON cue mode and a full XML document mode). These surfaced quietly in the July-6 draft wave alongside transport-19 and the Cisco MOCHA/TEMPO suite.
  • First runtime and validation exercises. moq became the first implementation to land MSF-01 support in code (behind a version-agnostic snapshot); Tobbe’s CUE-schema catalog validator (Eyevinn/msf-catalog-validator) is the first machine-validation feedback loop into the MSF/CMSF specs, and surfaced example/version bugs since fixed.

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