webrtcbin: h.264 streams work with Chrome but not with Firefox

Submitted by Carlos Rafael Giani

Description

Created attachment 371158
webrtc h264 test program

I wrote a small test program to try out unidirectional transfers with WebRTC from GStreamer to an HTML5 page. It works well with Chrome. But with Firefox, it fails.

I noticed some oddities in the SDP. The SDP that is sent from webrtcbin to FF contains a=sendrecv, a=rtpmap:96 H264/90000, and also an ice-ufrag. The SDP that is sent back from FF to webrtcbin however does not contain an ice-ufrag, and instead has a=rtpmap:96 H264/90000 and a=inactive for the mid:video0 stream.

Now I do know that FF can handle h.264 over WebRTC, because h.264 works with this example: http://mozilla.github.io/webrtc-landing/pc_test.html but I do not know why, or why it doesn't work with my test.

I attached my test code. I do not know that much about SDP or WebRTC, so maybe I am missing something. Or perhaps this is an SDP related bug in webrtcbin / gstsdp?

The example comes with its own libsoup based HTTP server, and does the signaling by itself via websockets. Just open the link printed in stderr in Chrome, then in Firefox.

Attachment 371158, "webrtc h264 test program":
webrtc-h264-test.tar.xz