Liaison statement
IETF MOQ WG intention to adopt work on a low-overhead packaging (LOCMAF) for CMAF media carried over Media Over QUIC Transport

Dear colleagues,

The IETF Media Over QUIC (MOQ) Working Group is developing transport and
packaging technologies for delivering media over QUIC with low latency. As part
of this effort, we are  considering adopting as a Working Group item an
Internet-Draft, "Low Overhead CMAF for Media over QUIC (LOCMAF)” [1].

We are writing to inform WG3 of this intention and to invite any comments, as
the work relates directly to MPEG media formats maintained by your group. We
greatly value the constructive relationship between our organizations and wish
to ensure WG3 has no concerns before we proceed.

The purpose and scope of LOCMAF is as follows:

  - LOCMAF defines a compact, low-overhead packaging for low-latency CMAF
  (ISO/IEC 23000-19) media carried end-to-end as MoQ Transport Object payloads
  [2]. It targets the case where CMAF chunk  headers (~100 bytes and up) can be
  as large as or larger than the coded frame itself, which is common for
  low-bitrate, low-latency audio.

  - LOCMAF carries the CMAF chunk head metadata from a single moof (movie
  fragment) as a small set of tagged fields and leaves the sample data (mdat)
  unchanged. Boxes surrounding the moof (styp, prft, emsg, uuid, and others)
  are carried verbatim. The first object of each transport group carries a full
  reference; subsequent objects carry only differences.

  - Critically, LOCMAF does not alter or redefine CMAF. The receiver
  reconstructs CMAF chunks that are decode-equivalent to the sender input,
  including the per-sample Common Encryption (ISO/IEC 23001-7) metadata
  required by CMAF DRM pipelines. A canonical, byte-identical reconstruction is
  defined for conformance testing. LOCMAF relies normatively on ISO/IEC
  23000-19 (CMAF), ISO/IEC 14496-12 (ISOBMFF), and ISO/IEC 23001-7 (CENC).

  - LOCMAF is a media packaging layer, not a transport and not a modification
  of the underlying file format. It is intended to be referenced normatively
  from the CMAF-compliant MOQT Streaming Format (CMSF) [3], which extends the
  allowed packaging values with a "locmaf" entry.

We would appreciate any feedback from WG3 by 30 October 2026, particularly on
whether you see concerns with the IETF defining a low-overhead
compression/packaging for CMAF media in this manner. We plan to await your
response before proceeding to a formal WG adoption call.

We look forward to continued collaboration.

Best regards,

Magnus Westerlund
Chair, IETF Media Over QUIC Working Group

References:
[1] Low Overhead CMAF for Media over QUIC (LOCMAF)
https://datatracker.ietf.org/doc/draft-einarsson-moq-locmaf/ [2] Media over
QUIC Transport https://datatracker.ietf.org/doc/draft-ietf-moq-transport/ [3]
Media CMSF- a CMAF compliant implementation of MOQT Streaming Format
https://datatracker.ietf.org/doc/draft-ietf-moq-cmsf/