FEC for video and webrtcbin

Application Development
1

Does webrtcbin support forward error correction (FEC) for video? If, how do you use it?

I’ve tried the following pipeline:

h264parse ! rtph264pay pt=96 ! rtpulpfecenc pt=122 percentage=100 ! webrtcbin

I only see pt=96 in the SDP offer. For example:

m=video 9 UDP/TLS/RTP/SAVPF 96
c=IN IP4 0.0.0.0
a=setup:actpass
a=ice-ufrag:/p3YyDhsTioWXTxIVHy32Dt0VHdCT8Dp
a=ice-pwd:APnX6kXOQCMOCW3NMiNNlWchYYNQ/v8p
a=rtcp-mux
a=rtcp-rsize
a=sendrecv
a=rtpmap:96 H264/90000
a=rtcp-fb:96 nack pli
a=rtcp-fb:96 ccm fir
a=rtcp-fb:96 transport-cc
a=framerate:10
a=fmtp:96 packetization-mode=1;sprop-parameter-sets=Z2QAKKwbGoB4AiflwFuAgICgAAB9AAAJxB0MAHoQAAL68F3lxoYAPQgAAX14LvLhQA==,aO44MA==;profile-level-id=640028;level-asymmetry-allowed=1
a=ssrc:1337454587 msid:user2287511883@host-926001c1 webrtctransceiver2
a=ssrc:1337454587 cname:user2287511883@host-926001c1
a=mid:video0
a=fingerprint:sha-256 43:A2:89:07:FE:22:80:17:CB:6B:61:E0:4B:E6:D1:3A:1A:76:16:60:E3:47:0C:20:25:11:56:CF:00:99:1C:FD
a=rtcp-mux-only

I don’t see any FEC packets on the receive side (Google chrome). In fact, I just get keyframes

I also tried adding in the rtpredenc, but that didn’t do anything

2

You need to change the fec-type property on the transceiver to something other than the default (none).

See subprojects/gst-plugins-bad/ext/webrtc/webrtctransceiver.c · main · GStreamer / gstreamer · GitLab for the property.

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