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Is there any free tool capable of doing the job?

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4 Answers

up vote 4 down vote accepted

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.

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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 '12 at 7:56
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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.

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CAF(Core Audio Format) is an audio file format developed by Apple in 2005, and is supported by Mac OS X 10.4 and higher, and iOS 5.0 and higher. This format is designed to overcome limitations of some older audio file formats, such as AIFF and WAV. CAF format uses 64-bit file offsets to break the 4GB file size limitation, so it can save hundreds of years of audio in one file. CAF supports compressed audio codec like AAC, MP3 and ALAC, so it uses less disk space than AIFF. What's more, CAF supports unlimited channels and metadata.

Some people recommend renaming the caf file and this way nearly doesn't work.

I know a way to batch convert caf to other audio formats like mp3/wav etc, but not sure if it applies to convert other audio formats to caf file. Give it a try to make sure that.

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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
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hi georgi - this doesn't cover off the normalisation part of the question. –  Rory Alsop Feb 28 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 at 16:44
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