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I have a folder full of .wav audio files.

Some are stereo, most are mono splits.

The mono split pairs are all named foo bar track.L.wav and foo bar track.R.wav

I can use the command line tool sox to combine a mono pair into 1 stereo track like this:

sox -M track1.L.wav track1.R.wav track1.Stereo.wav

where the first 2 files are the mono pairs, and the third is the output stereo file.

This is great, but I'd like to have a script that will automatically find all the mono pairs and combine them into stereo files.

I.e., I need it to find all files which have the same name except for the .L. and .R. before the extension, and run sox on them, outputting to a new file with the same name without the L/R suffix.

For example, if my folder contains these files:


I need to run these commands:

sox -M track1.L.wav track1.R.wav track1.Stereo.wav
sox -M track2.L.wav track2.R.wav track2.Stereo.wav
sox -M track3.L.wav track3.R.wav track3.Stereo.wav
sox -M track4.L.wav track4.R.wav track4.Stereo.wav

Here's where I am so far:

for file in ./*.L.wav;
    file2=`echo $file | sed 's_\(.*\).L.wav_\1.R.wav_'`;
    out=`echo $file | sed 's_\(.*\).L.wav_\1.STEREO.wav_'`;
    echo $file - $file2 - $out;

That works, but when I replace the echo line with

sox -M $file $file2 $out;

it doesn't work; spaces in the filenames cause it to fail.

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2 Answers 2

Going from sgmart's suggestion, I got it solved:

for file1 in ./*.L.wav; do 
  file2=`echo $file1 | sed 's_\(.*\).L.wav_\1.R.wav_'`;
  out=`echo $file1 | sed 's_\(.*\).L.wav_\1.STEREO.wav_'`;
  sox -MS "$file1" "$file2" "$out";
  mv "$file1" mono; mv "$file2" mono;

Needed "'s around the variables.

And I added a bit to move the processed files to a 'mono' subfolder.

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Try with this from a GNU/Linux console:

for file in ./*L*wav;
    for file2 in ./*R*wav;
        $out = "Stereo"
        sox -M $file $file2 $file-$out.wav;

NOTE: "./" represent the music directory where your files are.

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sox needs 3 args: the 2 files, plus the output file. I need the output file name to be the name of the first 2 without the L or R –  Ze'ev Oct 4 '12 at 22:52
Sorry, this does not work; it does not match up the matching files. It just returns every file with an "L", followed by every other file, recursively. –  Ze'ev Oct 4 '12 at 22:56
Yeah, I am sorry; I forgot the third argument –  sgmart Oct 4 '12 at 22:58
I updated the post to clarify; your code still doesn't line up matching pairs. Also, ./*.L.wav works better... –  Ze'ev Oct 4 '12 at 23:07
The second for statement needs to somehow find files that match the * from the first for –  Ze'ev Oct 4 '12 at 23:09

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