—The Speex codec has been obsoleted by Opus. It will continue to be available, but since Opus is better than Speex in all aspects, users are encouraged to switch—

Speex: A Free Codec For Free Speech


Speex is an Open Source/Free Software patent-free audio compression format designed for speech. The Speex Project aims to lower the barrier of entry for voice applications by providing a free alternative to expensive proprietary speech codecs. Moreover, Speex is well-adapted to Internet applications and provides useful features that are not present in most other codecs. Finally, Speex is part of the GNU Project and is available under the revised BSD license.

The Technology

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:

Note that Speex has a number of features that are not present in other codecs, such as intensity stereo encoding, integration of multiple sampling rates in the same bitstream (embedded coding), and a VBR mode; see our comparison page for more.

Getting Involved

One of the simplest things you can do to get involved in Speex is by using it in your application; Speex is well-suited to handle VoIP, internet audio streaming, data archival (like voice mail), and audio books. Currently, LinPhone, Ekiga, and Asterisk are some of the projects currently using Speex. For a list of projects with Speex support, visit our Plugins & Software page.

If you have questions or are interested in contributing to the project, have a look at our roadmap, join our mailing list, or send us money so we can keep working on Speex. You can also contact the Project Lead, Jean-Marc Valin (though the mailing is usually the best place to ask questions).

Patches can be sent to the mailing list, and should apply on the latest master branch.