Audio/Video Transport Core Maintenance (avtcore) Working Group

CHAIRS: Jonathan Lennox
Bernard Aboba

IETF 118 Agenda
Location: Prague, CZ
Session: Wednesday, Session I
Room: Berlin 1/2

Date: Wednesday, November 8, 2023
Time: 09:30 - 11:30 Prague time
00:30 - 02:30 Pacific time

IETF 118 info:
Meeting link:

Notetakers: Mo Zanaty, Spencer Dawkins

  1. Preliminaries (Chairs, 15 min)
    Note Well, Note Takers, Agenda Bashing, Draft status, Errata, IANA

Errata: #4873 verified, #4938 hold for doc update, #6752 verified

IANA Registry for RTP Payload Format Media Types:

  1. RTP Payload Format for sub-codestream J2K streaming (P. Lemieux, 10

  2. RTP Payload Format for the SCIP Codec (D. Hanson & M. Faller, 10

  3. RTP Payload Format for Visual Volumetric Video-based Coding (V3C)
    (L. Ilola, 10 min)

  4. RTP over QUIC (M. Engelbart, J. Ott, S. Dawkins, 15 min)

  1. HEVC Profile for WebRTC (B. Aboba, 10 min)

RPSI has been implemented for 1-1 use cases. But there are
implementation difficulties in supporting RPSI in conferencing

SFU forwards the RPSI to the encoder. No need to parse the RPSI, so SFU
doesn't need codec-specific knowledge.
Encoder generates a P-frame based on the LTR, includes info on
dependencies and chains in the Dependency Descriptor.

But how does the SFU know if the newly geerated P-frame can be decoded
by conference participants?
SFU can check if it forwarded the LTR to a participant. A participant
that recently joined may not have gotten it.
But even if it was sent, that doesn't necessarily imply that the LTR was
received, decoded and kept in the participant's buffer, available for
use in decoding the P-frame.

Proprietary LNTF RTCP message indicates last seqno received and decoded.
But that doesn't tell you whether the LTR is still in the buffer.

  1. RTP Payload Format for SFrame (P. Thatcher, 10 min)

  2. Viewport and Region-of-Interest-Dependent Delivery of Visual
    Volumetric Media (S. Gudumasu, 10 min)

  3. RTP Payload for Haptics (H. Yang, 10 min)

  4. RTP Payload Format for Geometry-based Point Cloud Compression (M.
    Engelbart, 10 min)

  5. Wrapup and Next Steps (Chairs, 10 min)