Apple first introduced its own lossless audio compression format, Apple Lossless Audio Codec (ALAC), in 2004 with iTunes 4.5. This Thursday—seven years later—the company made the code for its encoder and decoder available under an Apache 2.0 open source license.

ALAC is similar to another common open lossless format know as FLAC (Free Lossless Audio Codec), but uses an MPEG 4-compliant QuickTime container. ALAC is supported in iTunes as well as Apple's popular iPod and all iOS devices. For audiophiles who can't stand lossy formats like AAC or MP3, it offers a better sounding alternative. Unlike AAC or MP3, though, which tends to compress files around 10:1, lossless ALAC files only save about 50 percent of your disk space.

In addition to offering the format as an option in iTunes, Apple uses ALAC to transmit audio from iTunes or an iPhone to devices like an Airport Express or Apple TV for playback via AirPlay.

Why Apple decided to open source its ALAC code at this point in time is unclear. Independent developers had reverse engineered the codec and included support in libavcodec six years ago, and thus, popular open source media playback apps like VLC and Boxee have supported the format ever since. Still, if you want Apple's reference implementation of the format, the code is available for the taking.