Как я обычно перекодирую видеоконтент

mencoder -oac pcm -ovc copy -o "$1".mkv "$1"
mplayer -ao pcm:fast:file="$1".wav -vc null -vo null -benchmark "$1".mkv
sox "$1".wav -c 1 -r 44100 -e signed-integer -b 16 "$1".wav.wav
mv "$1".wav.wav "$1".wav
normalize --peak "$1".wav
opusenc "$1".wav "$1".opus
rm "$1".wav
opts="mbd=2:trell:dia=2:preme=2"
for vpass in 1 2; do
    mencoder \
        -nosound \
        -passlogfile "$1".log \
        -ovc lavc \
        -lavcopts vcodec=libvpx:$opts:autoaspect:vpass=$vpass \
        -vf scale=960:540 \
        -o "$1".vp8 "$1".mkv
done
mkvmerge --webm -o "$1".webm "$1".opus "$1".vp8
rm "$1".opus "$1".vp8 "$1".log "$1".mkv