Audio/Video Transport Core Maintenance (avtcore) Working Group

CHAIRS: Jonathan Lennox
Bernard Aboba

Virtual Interim Agenda
Date: Thursday, December 15, 2022
Time: 08:00 - 10:00 Pacific Time


Meeting link:

Remote instructions:


Notes by: Mo Zanaty, Spencer Dawkins

1. Preliminaries (Chairs, 15 min)

Note Well, Note Takers, Agenda Bashing, Draft status, CfAs

2. RTP Control Protocol (RTCP) Messages for Green Metadata (Yong He, 10 min)

3. MAX_STREAMS and the Frame/Stream Model (B. Aboba, 10 min)

4. Scoping for RTP over QUIC (J. Ott, M. Engelbart, S. Dawkins, 20 min)

5. RTP over QUIC (J. Ott, M. Engelbart, 20 min)

6. Codec Agnostic Payload Format (Y. Fablet, 20 min)

7. Wrapup and Next Steps (Chairs, 15 min)

Zulip Logs

Roni Even10:04
I am on my phone

Stephan Wenger10:09
I'm juggling two calls. If you have anything specific for me and I don't
respond, please put it in the chat.

Jonathan Lennox10:10
Stephan, can you update the EVC draft?

Stephan Wenger10:11
I have no audio right now.

Lauri Ilola10:11
Seems you cant hear me


Stephan Wenger10:11
EVC draft will be revved as soon as RFC 9324 is published; any day now.
Mid Jan the latest, probably earlier

I get audio: 0 kbps. Anyone else?

Nils Ohlmeier10:14
I'm getting 10-20 kbps audio

Stephan Wenger10:16
Had to reboot my Mac. And I thought rebooting helps only with Windows

Youenn Fablet10:17
@Stephan, if you are using Safari, feel free to file a bug in and send me a sysdiagnose (

Stephan Wenger10:18
Green Metadata is Leonardo's sin, but it's known now

Rui Paulo10:32
max_streams is not about open streams

Joerg Ott10:33

Rui Paulo10:33
rfc9000 "A count of the cumulative number of streams of the
corresponding type that can be opened over the lifetime of the
connection. "

Jan-Ivar Bruaroey10:35
To clarify: the await/then issue isn't about a technical difference, but
about whether the JS sender blocks writing more bytes on the successful
queuing of bytes it just wrote. pipeTo() backpressure uses await
writer.ready for this reason which resolves ahead of writer.write(), for
better concurrency

Vidhi Goel10:37
Though max_streams is cumulative, quic implementation increases that
limit anytime streams are closed. So, it tries to maintain some number
of streams always open

Joerg Ott10:39


Mo Zanaty10:39
@Vidhi, any spec ref to justify such implementation? It sounds wrong
from a brief scan of RFC 9000.

Joerg Ott10:40
@Mo: It is treated as a sliding window according to some discussions on
the moq list, IIRC

Stephan Wenger10:46
can we PLEASE use zoom for future calls

Shuai Zhao10:49
I don’t think Stephan has audios

Stephan Wenger10:50
I'm going to shoot this computer!

Dale Worley10:50
Stephan: Nobody can hear you.

Stephan Wenger10:50
+1 to Peter's pont. ALso, the slide is overly standards-centric. Define
applications not be call control etc. standards.

I still want a drop-in replacement for RTP over UDP without standardized
call controls, as this is what large segments of the industry are using

can we PLEASE PLEASE PLEASE use zoom henceforth

Trying to clear my queue

Joerg Ott11:00
QUIC TS could be used as an improvement if available but certainly would
not be mandated

At the last IETF, Christian Huitema was trying to see how much interest
there was in QUIC TS

Rui Paulo11:00
would quic timestamps interact with rtp's timestamps ?

Joerg Ott11:01
within the QWUIC WG

there was limited response at this point

Rui Paulo11:01
@joerg, that may have been because of an application, but it seems like
RTP could be a motivating factor

we don't hear any echo, btw.

Joerg Ott11:05
lucky you, at least then I was intelligible

Harald Alvestrand11:14
Is QUIC over TCP even defined?

Rui Paulo11:14
I hope not :-)

Harald Alvestrand11:17
So QUIC over TCP is QUIC over UDP over MASQUE? Stack ALL the layers!

Sam Hurst11:19
HTTP/3 doesn't specify the congestion control, the QUIC transport layer

Rui Paulo11:21
@Sam, that is correct.

Vidhi Goel11:24
The examples of NADA and Scream shouldn’t be taken as the only options

Sam Hurst11:30
Is this multiplexing question more of a general topic, and possibly not
unique to running RTP over QUIC? Maybe it's more generally useful to
define some transport extension which specifies a generic stream type
like that defined by H3 for unidirectional stream types?

Sergio Garcia Murillo11:32
what's the use case of multiplexing multiple RTP sessions over the same
QUIC connection?

Jan-Ivar Bruaroey11:38
but allowPooling defaults to false?

So if I create two new WebTransport(url); in the same document, they
fail? Not sure that is correct

also iframes

A WebTransport session is a session of WebTransport over HTTP/3. There
may be multiple WebTransport sessions on one connection, when pooling is

Vidhi Goel11:45
I would argue against over webtransport or http as there are
applications that don’t do either.

If you want to just take the multiplexing logic from webtransport, then
I think it needs to very clear

Jonathan Lennox11:47
Bernard, I think you've lost audio

Mo Zanaty11:49
Are we ending in 10 min at 10am PST?

Spencer Dawkins11:59
Mo, I heard a chair say maybe we can run over a bit ...

Mo Zanaty12:00
Spencer, I have a conflicting meeting starting now, so thanks for taking
over the minutes.

Harald Alvestrand12:11
need to go!