[webrtc-stats] codec.sdpFmtpLine isn't clear about which SDP to use (#616)

jan-ivar has just created a new issue for https://github.com/w3c/webrtc-stats:

== codec.sdpFmtpLine isn't clear about which SDP to use ==
webrtc-stats [sdpFmtpLine](https://w3c.github.io/webrtc-stats/#dom-rtccodecstats-sdpfmtpline) says:
_"The a=fmtp line in the SDP corresponding to the codec, i.e., after the colon following the PT. This defined by [JSEP] in Section 5.7."_

This isn't very clear about which description this SDP is from.

webrtc-pc [sdpFmtpLine](https://w3c.github.io/webrtc-pc/#dom-rtcrtpcodecparameters-sdpfmtpline) parameter says:
_"The "format specific parameters" field from the a=fmtp line in the SDP corresponding to the codec, if one exists, as defined by [RFC8829] (section 5.8.). For an RTCRtpSender, these parameters come from the remote description, and for an RTCRtpReceiver, they come from the local description."_

The last one is newer and seems more helpful as it clarifies what description the SDP comes from, but see https://github.com/w3c/webrtc-pc/issues/2710 for clarifying this is sometimes the pending local description.

Should we update this spec to use that clarification as well? Or is stats supposed to return different codec information than getParameters when there is a pending local description?

A separate question is what _"the SDP corresponding to the codec"_ actually means, since `a=fmtp` is per m-line. But that's https://github.com/w3c/webrtc-stats/issues/614.

Please view or discuss this issue at https://github.com/w3c/webrtc-stats/issues/616 using your GitHub account


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Received on Thursday, 20 January 2022 04:11:21 UTC