AVTCORE

Summary

The AVTCORE Working Group held a virtual interim meeting to discuss current working group drafts and a proposal for standardizing RTP/SDP signaling for Opus Multistream. Marius Kleidl presented the chair updates on active drafts, and Sun Shin presented updates on the Opus Multistream draft.

Key Discussion Points

WG Status Update

Marius Kleidl presented the Chair slides summarizing the current draft status:

RFC Editor Queue: VP9 RTP payload format is currently in the RFC Editor queue.
With IESG: V3C, JPEG XS, and draft-ietf-avtcore-frame-acknowledgement (recently adopted and renamed) are with the IESG.
Adopted and Active Drafts:
- draft-ietf-avtcore-rtp-apv, draft-ietf-avtcore-hevc-webrtc, and draft-ietf-avtcore-rtp-vdmc are active but have seen quiet periods recently.
- Work on RTP over QUIC has slowed down.
- The absolute capture time draft may be parked due to Harald Alvestrand's retirement.
- draft-ietf-avtcore-rtp-sframe has active development, and a presentation is expected at the next IETF meeting.

RTP/SDP for Opus Multistream

Sun Shin presented RTP/SDP for Opus Multistream, detailing the proposal to standardize SDP signaling for multi-stream Opus:

Use Case: Cloud gaming (e.g., NVIDIA's services) requires high-quality multi-channel surround sound to deliver spatial audio experiences to players.
Current Limitations: Although libwebrtc already implements multi-stream Opus encoder/decoder capabilities, they are not advertised or negotiated at the SDP layer in Chromium. Currently, browsers reject multi-channel Opus in the SDP answer, forcing implementations to rely on local SDP munging as a workaround.
Addressing Feedback:
- Added a section clarifying Opus Family 1 mapping and extensibility to address feedback from Tim Bruylants.
- Added text to the introduction to align with the MMUSIC Working Group and explicitly state that the draft does not modify the underlying Opus codec specification, but only defines the signaling syntax (addressing feedback from Mo Zanaty).
- Improved overall offer/answer clarity.
Technical Discussion:
- Jonathan Lennox asked if the proposal aligns exactly with what is already implemented in Chromium, or if there were additions (such as channel mappings). Sun Shin confirmed that the proposal simply exposes the existing, unadvertised multi-Opus support in the browser without modifications to the codec layer.

Decisions and Action Items

Action Item: Erik Språng to coordinate moving the Git repository for draft-ietf-avtcore-frame-acknowledgement into the AVTCORE GitHub organization. Marius Kleidl has provided the setup instructions.
Decision: Based on the positive feedback and the addressed comments, the chairs will initiate a call for adoption for the Opus Multistream draft on the AVTCORE mailing list.

Next Steps

Initiate the mailing list adoption call for the Opus Multistream draft.
Prepare for the hybrid sessions at IETF 122 in Vienna.

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