[Ardour-Users] 4-channel stereo

[Ralf Mardorf]

On Sat, 21 May 2016 12:15:42 +0200, Alex Rodriguez Lopez wrote:
>The way I do it, I split them before hand using sox (very handy command
>line utility), so then you would have 4mono files you can use one per
>channel in ardour. Its even fairly easy to write a script that will
>split to mono all files of a certain extension in a folder using Sox.

I'm using a script to split stereo files based on ffmpeg and added it as
tool to spacefm, so just selecting a file and a shortcut is needed. This
could be done using sox or ffmpeg with any number of channels.

Perhaps not a beautiful script, but it does the job ;).

$ cat /usr/local/bin/s2m
#!/bin/dash

version="2016-04-28"

usage()
{
  cat<<EOF

  s2m version $version rocketmouse

  stereo.wav > mono.wav:
    s2m input_file.wav
  stereo.wav > left.wav:      
    s2l input_file.wav
  stereo.wav > right.wav:
    s2r input_file.wav
  stereo.wav > dual {left,right}.wav:
    s2d input_file.wav
  stereo.wav > all {mono,left,right}.wav:
    s2a input_file.wav

EOF
  exit $1
}

outfile()
{
  outfile="$(echo "$infile" | sed 's/\(.*\).wav/\1_'$1.$suffix/I)"
  if [ -f "$outfile" ]; then
    echo "$outfile already exists"
    usage 1
  fi
}

ex2file()
{
  outfile $1
  echo "Export to $outfile"
  case $1 in
    mono)
      ffmpeg -i "$infile" -ac 1 "$outfile"
    ;;
    left)
      ffmpeg -i "$infile" -map_channel 0.0.0 "$outfile"
    ;;
    right)
      ffmpeg -i "$infile" -map_channel 0.0.1 "$outfile"
    ;;
  esac
}

case $1 in
  -h|--help)
    usage 0
  ;;
esac

infile="$1"
if [ ! -f "$infile" ]; then
  echo "No file $infile"
  usage 1
fi

num_ch=$(exiftool "$infile" | grep -v "File Name" | grep -v "Directory" | grep "Num Channels" | cut -d: -f2 | sed s/\ //)
plural=""
if [ "$num_ch" = "" ]; then
  num_ch="No"
else 
  if [ "$num_ch" -ge "2" ]; then
    plural="s"
  fi
fi
if [ "$num_ch" != "2" ]; then
  echo "$num_ch channel$plural, not a stereo file"
  usage 1
fi

suffix=$(echo "$infile" | rev | cut -d. -f1 | rev)
if [ "$(echo "$suffix" | tr [:upper:] [:lower:])" != "wav" ]; then
  echo "Suffix is \"$suffix\", must be \"wav\", case sensitivity is not required"
  usage 1
fi

case $(basename $0) in
  s2m)
    ex2file mono
  ;;
  s2l)
    ex2file left
  ;;
  s2r)
    ex2file right
  ;;
  s2d)
    outfile right
    ex2file left
    ex2file right
  ;;
  s2a)
    outfile left
    outfile right
    ex2file mono
    ex2file left
    ex2file right
  ;;
esac

exit