Is there any free tool capable of doing the job?

3 Answers 3


You didn't supply very much information, such as your OS and your desired output format, so I can not give you a detailed answer.

CAF is a container format that can support several audio formats, but Apple Lossless (ALAC) is probably the most common.

ffmpeg can decode ALAC in CAF:

ffmpeg -i input.caf output.wav

This can be turned into a "batch" command with a Bash "for loop".

for f in *.caf; do ffmpeg -i "$f" "${f%.caf}.wav"; done

sox can be added to this example to normalize your audio:

for f in *.caf; do ffmpeg -i "$f" -f sox - | sox --norm=-3 -t sox - "${f%.caf}.wav"; done

As usual, using a recent ffmpeg is recommended since development is so active. See the FFmpeg download page for various methods to acquire it.

  • I think that is exactly what I needed. I did a little Googling, and it turns out that ffmpeg and sox are compatible with most platforms, included mine (Mac OS X), thanks very much
    – rraallvv
    Nov 18, 2012 at 7:56

Sox is great as some above mentioned, I'd check out Sample Manager by audiofile engineering though. It's cheap and awesome. I use it nearly every day.



AFCONVERT(1)              BSD General Commands Manual

     afconvert -- Audio File Convert

     afconvert [-h] src_audiofile dest_audiofile

     Audio File Convert will convert a source audio file to a new audio file 
     with the specified file and data types
  • hi georgi - this doesn't cover off the normalisation part of the question.
    – Rory Alsop
    Feb 28, 2014 at 11:54
  • true.. i didn't pay attention to the "normaliser" part of the question. that said, the accepted answer also uses another third party tool (sox) to normalise the sounds. i meant to point out that ffmpeg is overkill.
    – georgi
    Feb 28, 2014 at 16:44

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