FLAC Compression
High quality audio files take a lot of space, for example, a 1 minute stereo sound at CD-quality (44.1 kHz) will take about 10-11 Mb. A large collection of sound files will fill hard drives really fast. The usual solution to this problem is to compress the files, however each compression system has its limitations.
The common zip compression format works well for text but does not compress audio in any significant degree. Encoding the file to mp3 will destroy a lot of information that will be necessary to analyze the audio.
FLAC (Free Lossless Audio Codec) is optimized for wav audio files, and can compress a wav to 30-50% of its original size. It appears that the amount of compression will depend on the complexity of the sound recorded. The decoding back to wav is very fast and it is an exact copy of the original file.
Following are some examples of using FLAC:
To compress a wav file (test.wav) to flac:
-
flac test.wav
To compress a wav file (test.wav) to flac, verify the compression, and delete the original wav if compression went well:
-
flac –verify –delete-input-file test.wav
Easy enough, to compress a bunch of files in a directory:
-
flac *.wav
To recover the wav file from a flac:
-
flac -d test.flac
How much compression?
Tested using 11280 wav files, each one approximately 60 sec, mono, sampling rate of 48 kHz:
- Total size in wav: 67 GB
- Total size in flac: 24 GB
- Compressed to 36%Â !
Getting FLAC
FLAC is free and open source.
- Ubuntu: sudo apt-get install flac
- Windows, Mac OS X, and others: Download the Installer
Libraries for C and C++ are also available with the source code.
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