I am not able to connect a call from Firefox to Firefox using VP9, allthough I have tried modifying the SDP in several different ways. I have a site similar to https://webrtc.github.io/samples/src/content/peerconnection/munge-sdp/, where I simply remove the unwanted codec. In Firefox, VP9 is not listed when I initiate the call. I have enabled VP9 on both sender and receiver, by setting media.mediasource.webm.enabled to true in about:config.
Does anybody know how to modify it correctly to get the call to go through, using VP9? I am running Firefox 47.0.1