Extend the WebRTC RTCRtpTransceiver API to offer control over which RTP header extensions are negotiated.
With the number of RTP header extensions being proposed, experimented with or included in implementations, sending them all all the time will incur considerable overhead, and trying to negotiate too many of them has led to interoperability issues. A mechanism for negotiating them is available in SDP, but a control mechanism for this negotiation has not been available.
Explainers: https://docs.google.com/document/d/1y1hTsMeav5ijPvoqu1R6U4YC564i1QzgkMeIqWhgiis/edit