Fix keyframes i-frame type on hardware transcode

transcoder/src/stream.go

@@ -207,6 +207,12 @@ func (ts *Stream) run(start int32) error {
 		"-start_at_zero",
 		// for hls streams, -copyts is mandatory
 		"-copyts",
+		// this makes output file start at 0s instead of a random delay + the -ss value
+		// this also cancel -start_at_zero weird delay.
+		// this is not always respected but generally it gives better results.
+		// even when this is not respected, it does not result in a bugged experience but this is something
+		// to keep in mind when debugging
+		"-muxdelay", "0",
 	)
 	args = append(args, ts.handle.getTranscodeArgs(toSegmentStr(segments))...)
 	args = append(args,

transcoder/src/videostream.go

@@ -63,7 +63,11 @@ func (vs *VideoStream) getTranscodeArgs(segments string) []string {
 		"-b:v", fmt.Sprint(vs.quality.AverageBitrate()),
 		"-maxrate", fmt.Sprint(vs.quality.MaxBitrate()),
 		// Force segments to be split exactly on keyframes (only works when transcoding)
+		// forced-idr is needed to force keyframes to be an idr-frame (by default it can be any i frames)
+		// without this option, some hardware encoders uses others i-frames and the -f segment can't cut at them.
+		"-forced-idr", "1",
 		"-force_key_frames", segments,
+		// make ffmpeg globaly less buggy
 		"-strict", "-2",
 	)
 	return args