Your environment.

• github.com/pion/webrtc/v4 v4.0.14
• github.com/pion/interceptor v0.1.37
• Any browser with relative new version, desktop chromium and mobile safari in my case.

What did you do?

I use flexfec03 via the following code

	err = m.RegisterCodec(
		webrtc.RTPCodecParameters{
			RTPCodecCapability: webrtc.RTPCodecCapability{
				MimeType:     webrtc.MimeTypeFlexFEC + "-03",
				ClockRate:    9000,
				Channels:     0,
				SDPFmtpLine:  "repair-window=10000000",
				RTCPFeedback: nil,
			},
			PayloadType: 118,
		},
		webrtc.RTPCodecTypeVideo,
	)

// ...

	fecInterceptor, err := flexfec.NewFecInterceptor()
	if err != nil {
		panic(err)
	}
	i.Add(fecInterceptor)

Through logging in sender and observing receiver stats I'm pretty sure pion is sending encoded FEC packets correctly. But when I randomly drop some packets in a controlled network, the framerate in clientside didn't drop significantly, but the video tears apart from time to time. I think this perhaps means the browser can recover frames from FEC paload, but the recovered frame is incorrect.