1708813 - Asymmetric payload type negotiation is still not working quite right when we are the offerer

Status: RESOLVED FIXED

(Core :: WebRTC: Signaling, defect, P2)

Description

[Byron Campen [:bwc]]

When an answer contains an asymmetric payload type, we attempt to remember it so we can put it in reoffers:

https://searchfox.org/mozilla-central/rev/92be70819506d269df7c192bfbddc8c6ce581990/dom/media/webrtc/jsep/JsepTrack.cpp#412-413

Unfortunately, this does not always work appropriately. If we are the offerer, the payload type is updated for the send track only (because the answerer is not allowed to override our recv track's payload type on that negotiation).

https://searchfox.org/mozilla-central/rev/92be70819506d269df7c192bfbddc8c6ce581990/dom/media/webrtc/jsep/JsepCodecDescription.h#72-74

This means that for the recv track, the prototype codec is not updated, leaving the send/recv codecs out of sync with one another. I think we need to be updating the prototype codec's payload type to match |fmt|, not |clone->mDefaultPt|.

When these are out of sync, reoffers will use the old payload type in the rtpmap/m-line, but we will observe the new payload type in fmtp if the send track has format params (since the send track has switched over to the new payload type).

Comment 1

[Byron Campen [:bwc]]

I've observed this on MS Teams, and it may impact interop there.

Comment 2

[Byron Campen [:bwc]]

Baseline:
https://treeherder.mozilla.org/#/jobs?repo=try&revision=0dcf6bb2c5cbc04537210d3377f60a8789bf142b
https://treeherder.mozilla.org/#/jobs?repo=try&revision=0e646654d3ecef2dbaa597660177e2668c90bb2e
https://treeherder.mozilla.org/#/jobs?repo=try&revision=450cf439f75e4ce9b2669299ac6bba38c7782f1d

Comment 3

[Byron Campen [:bwc]]

Patched:
https://treeherder.mozilla.org/#/jobs?repo=try&revision=92f5954ecf08caf66eaa7483d550fc4e9c7a0454
https://treeherder.mozilla.org/#/jobs?repo=try&revision=b442ecbd181e340ab52a09e3c902117f79e76b61
https://treeherder.mozilla.org/#/jobs?repo=try&revision=e1d49a27c7d6702742c29adf391ceee5fb323837

Comment 4

[Byron Campen [:bwc]]

Attachment: Bug 1708813: Test-case for bug. r?mjf

Comment 5

[Byron Campen [:bwc]]

Attachment: Bug 1708813: Remember remote side's payload type on recv tracks when we were the offerer. r?mjf

Depends on D114039

Comment 6

[Byron Campen [:bwc]]

Try looks fine.

Comment 7

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/1678b35bed45
Test-case for bug. r=mjf
https://hg.mozilla.org/integration/autoland/rev/a0f39c1b8c5d
Remember remote side's payload type on recv tracks when we were the offerer. r=mjf

Comment 8

[Alexandru Michis [:malexandru]]

https://hg.mozilla.org/mozilla-central/rev/1678b35bed45
https://hg.mozilla.org/mozilla-central/rev/a0f39c1b8c5d