Record screen capture with audio in FreeBSD with ffmpeg

This command can be used:
ffmpeg -video_size 1920x1080 -framerate 25 -f x11grab -i :0.0+0,0 -f oss -i /dev/dsp5.0 -filter:a "asetpts=N/SR/TB" output.mp4
Command above assumes that microphone is at /dev/dsp5.0 (you can check that with cat /dev/sndstat), and you can adjust microphone volume with mixer -f /dev/mixer5 mic 100.