[DC LoCo] /. News: Apple's Lossless Audio Codec (ALAC) Now Open Source

[Greg Reagle]

I offer this explanation in the hope that anyone reading who does not know about the difference between lossless and lossy compression might gain more understanding.

Compression is reducing the size (i.e. number of bytes).

A lossless compression algorithm, such as zip, gzip, bzip2, png, flac, loses no data in the compression.  So to compress a file with a lossless algorithm and then uncompress it produces an exact duplicate (byte for byte) of the original.

A lossy compression algorithm, such as jpeg or mp3, does lose data in the compression.  So to compress a file with a lossy algorithm and then uncompress does not and cannot produces an exact duplicate of the original.  It will be different.

Lossy compression algorithms generally can achieve a much better reduction in size than lossless, and lossy algorithms are generally used for audio and video.  Lossless compression algorithms are generally used for other types of data, or audio and video when preserving the original exactly is essential.

-- 
Greg Reagle
System Administrator
Center for Economic and Policy Research
reagle at cepr.net
http://www.cepr.net/