Speex

Speex is a legacy Open Source/Free Software patent-free audio codec designed for speech. It is obsoleted by Opus.

Technical Information

Speex is based on CELP and is designed to compress voice at bitrates ranging from 2 to 44 kbps. Some of Speex’s features include:

• Narrowband (8 kHz), wideband (16 kHz), and ultra-wideband (32 kHz) compression in the same bitstream
• Intensity stereo encoding
• Packet loss concealment
• Variable bitrate operation (VBR)
• Voice Activity Detection (VAD)
• Discontinuous Transmission (DTX)
• In-progress fixed-point port
• Echo Cancellation (experimental)
• Vorbis psychoacoustics model (experimental)

Note that Speex has a number of features that aren’t in other codecs such as Intensity stereo encoding, integration of multiple sampling rates in the same bitstream, and a VBR mode.

References

The above information was copied from the Speex home page.