A patent-free audio codec designed especially for voice (unlike Vorbis which targets general audio) signals and providing good narrowband and wideband quality. This project aims to be complementary to the Ogg Vorbis codec.
Notes: The most important new feature is Varible Bit-Rate (VBR). It can be enabled by using the --vbr option to speexenc. When encoding in VBR, the --quality option can still be used. Note VBR implementation in this release is experimental and still requires lots of tuning.
http://speex.sourceforge.net (http://speex.sourceforge.net)