movie2audio

#!/bin/sh
##
## Convert video file to audio file by FFmpeg
## Copyright (c) 2013 SATOH Fumiyasu @ OSS Technology Corp., Japan
##
## License: DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE Version 2
##

set -u

perr() {
  echo "$0: ERROR: $1" 1>&2
}

pdie() {
  perr "$1"
  exit "${2-1}"
}

ffprobe="ffprobe"
ffmpeg="ffmpeg"

video_fname="$1"; shift

if [ ! -f "$video_fname" ]; then
  pdie "No such file: $video_fname"
fi
if [ ! -r "$video_fname" ]; then
  pdie "Permission denied to read: $video_fname"
fi

audio_codec=`
  "$ffprobe" \
    -loglevel warning \
    -i "$video_fname" \
    -show_streams \
    -select_streams a:0 \
  |sed -n 's/^codec_name=//p' \
  ;
`
if [ -z "$audio_codec" ]; then
  pdie "Cannot detect audio codec from video file: $video_fname"
fi

audio_fname="${video_fname%.*}.$audio_codec"
if [ x"$video_fname" = x"$audio_fname" ]; then
  exit 0
fi

"$ffmpeg" \
  -loglevel warning \
  -i "$video_fname" \
  -y \
  -codec:a:0 copy \
  "$audio_fname" \
;

exit $?