FLAC Compression Level Explained

April 8, 2014

FLAC, short for “Free Lossless Audio Codec”, is a popular lossless compression format for audio. The format offers varying levels of lossless compression from 1 through 8. These levels correspond to a number of different parameters that can be tweaked to optimize the codec’s performance for your particular situation. Check out the graph below.

The graph above represents file size data for two songs at varying compression levels. Song 1 (Blue) was a piano concerto and Song 2 (Green) was a modern Top 40 pop song. The original file sizes in AIFF format were 122.9 MB and 49.5 MB, respectively. As you can see, even FLAC Level 0 saves you a lot of hard drive space — approximately 54% for Song 1 and 31% for Song 2.

Let’s talk about why you might not want to use Level 8 to reduce the size of your music library. When music files are compressed, they have to be decompressed on the fly during playback. As the compression level increases, your computer or portable music player has to do more work to decompress the file. This means you’ll end up losing battery life for negligible space savings.

Here’s another piece of data. Converting Song 1 from AIFF to FLAC at Level 5 took approximately 6 seconds. The same conversion with Level 8 took approximately 18 seconds. Obviously compression and on the fly decompression are different, but it’s interesting to note that that Level 8 took three times as long as Level 5, while reducing file size by only .2 MB.

The default compression level for FLAC is Level 5, and this is where an optimal balance between file size reduction and playback performance is achieved. To read more about the FLAC compression codec, click here.


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