[jitsi-dev] H264 bugs and (possible) fixes


#1

Hello,

I've been using Jitsi for some time and have to say that it works very
well. One thing though is that when using H264, bitrate is not
respected. I had a look at JNIEncoder and found some problems:

- bitrate is fixed at 128000
- bitrate_tolerance is set which is useless for x264
- quantizer is set so CBR is not respected
- camera fps is not returned (from v4l2 and directshow) and framerate is
set to 15, however most cameras are at 30fps by default

Here is a patch that makes use of CRF that I find really efficient. It
removes qcompress, bitrate, bitrate_tolerance and defines crf and
buffer_size (vbv-bufsize). It also gets user defined bitrate and set
default framerate at 30.

Next thing is intra-refresh has changed in recent versions of ffmpeg, it
has to be defined in x264 private options (add "intra-refresh", "1").

Last thing is FFmpeg.CODEC_FLAG_LOOP_FILTER flag is, from what I
understand, to enable the loop filter. However, "ultrafast" preset
disables it. I think setting "deblock" at "0:0" enables it again but may
have an effect on sliced threads (I have to check).

Best regards,
BenoƮt

h264-crf.patch (2.96 KB)