record webcam lip-syncing an mp3 played with cvlc and then mux the recorded audio with the selected audio stream

dub.fish

#!/usr/bin/env fish

set AUDIO $argv[1]

echo input: $AUDIO

rm /tmp/salida.mpg
set BIRTH_T (date +%s%N)
cvlc $AUDIO &
set START_T (date +%s%N)
set DIFF_T (math $START_T - $BIRTH_T)
echo $DIFF_T > DIFF

# I am assuming the webcam is at /dev/video0
ffmpeg -f v4l2 -framerate 25 -s 640x480 -i /dev/video0  /tmp/salida.mpg
ffmpeg -y -i /tmp/salida.mpg -ss 0:0:1 -i $AUDIO -shortest -f mp4 -pass 1 -passlogfile /tmp/passlogfile -vcodec mpeg4 -r 25 -b:v 512K -s 640x480 -an /dev/null
ffmpeg -y -i /tmp/salida.mpg -ss 0:0:1 -i $AUDIO -shortest -f mp4 -pass 2 -passlogfile /tmp/passlogfile -vcodec mpeg4 -r 25 -b:v 512K -s 640x480 -acodec libmp3lame -ar 44100 -b:a 96K salida.mp4