Ogg Vorbis is an open, free audio compression format.
Unlike the MP3 and WMA formats, it is not patent encumbered, which eliminates certain legal and practical barriers for its use in free software.
It also can achieve somewhat better audio quality with the same amount of compression, compared to MP3. It also achieves better audio quality than WMA at the same bitrate, however the differences are very slight and would not be noticed by most listeners.
- http://en.wikipedia.org/wiki/Vorbis - Wikipedia article on Vorbis
- http://www.hydrogenaudio.org/forums/index.php?showtopic=36465 - Hydrogenaudio listening tests