Re: [rtcweb] JSEP-bis and WebRTC-Extensions Section 5.2

[Christer Holmberg <[e-mail]>]

Hi,

I have issues with the proposed change.

First, AFAIK, "enabled" is not used in any other O/A specification.

Second, my reading of "supported" is that it is something that the endpoint is actually willing to/capable of using within the session.

Third, within the JSEP O/A procedures, "supported" is used for other features (e.g., FEC mechanisms). Using other terminology for one feature will only confuse the reader, in my opinion.

Fourth, if it is unclear what "supported" really means we should rather clarify that.

Regards,

Christer

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________________________________
From: rtcweb <[e-mail]> on behalf of Justin Uberti <[e-mail]>
Sent: Saturday, May 6, 2023 3:30:33 AM
To: [e-mail] <[e-mail]>; [e-mail] <[e-mail]>
Subject: [rtcweb] JSEP-bis and WebRTC-Extensions Section 5.2

The WebRTC W3C WG is working on an extension spec<https://w3c.github.io/webrtc-extensions/#rtp-header-extension-control-modifications> that suggests behavior for RTP header extension O/A that conflicts slightly with the current version of JSEP. Rather than have this sort of ad-hoc extensions extension to JSEP in the W3C spec, it was suggested that we could apply a tiny patch to JSEP before JSEP-bis is finalized (it's currently in the RFC Editor state). Murray was supportive of this but wanted to make sure the WG was fully behind this change first.

For context, Section 5.2 in the W3C extension spec basically says that WebRTC endpoints can control the extensions that are in use, and as a result O/A negotiation should a) use only the extensions that are enabled by the endpoint, and b) always reoffer all extensions, rather than the previously negotiated set.

I've made a PR that captures this request at https://github.com/rtcweb-wg/jsep/pull/1033/files<https://protect2.fireeye.com/v1/url?k=31323334-501d5122-313273af-454445555731-45f3175ddedc0fdc&q=1&e=d500064c-f63a-47ed-b1ec-2ff879fda6f4&u=https%3A%2F%2Fgithub.com%2Frtcweb-wg%2Fjsep%2Fpull%2F1033%2Ffiles>, and it basically makes two surgical changes:
1) replaces the use of "supported RTP header extensions" with "enabled RTP header extensions"
2) changes the text around "extensions... present in the most recent answer" to instead say "extensions... enabled on the associated transceiver" (similar to how codecs are handled in JSEP).

Please let me know if this sounds reasonable to you or you have concerns.

Thanks,
Justin