[FFmpeg-user] ffmpeg mp4 encoding with cfr is not working

[Sangsu Baek]

I'm trying to capture camera input using v4l2.
My command line is like this:

ffmpeg -f v4l2 -input_format yuyv422 -r 15 -s 320x240 -i /dev/video0 -t 30 -y -vcodec mpeg4 -filter:v fps=15  /tmp/record.mp4

Problem is output fps is varying. I really want to get constant 15 fps output. Reason is,When I record 30 seconds, It takes not 30 seconds but 40 seconds or so under varying fsp. So I want to fixed 15fps output.

I'm using 1.2.1 version ffmpeg.

Direct Raw video capturing through /dev/video0 works well. (format is yuyv422, 15Hz).

thank you for reading.