ffmpeg command

1. make ogv file to mp4
ffmpeg -i demo.ogv \
       -c:v libx264 -preset veryslow -crf 22 \
       -c:a libmp3lame -qscale:a 2 -ac 2 -ar 44100 \
       demo.mp4

http://www.catswhocode.com/blog/19-ffmpeg-commands-for-all-needs