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—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: 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:

  • 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)
  • Fixed-point port
  • Acoustic echo canceller
  • Noise suppression

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.


  • Speex 1.2.1 and SpeexDSP are out!

    June 16, 2022

    This is the latest stable release of the Speex codec and the Speex DSP library.

  • Speex 1.2.0 is out

    December 7, 2016

    This is the latest stable release of the Speex codec library.

  • SpeexDSP 1.2rc3 is out

    January 3, 2015

    This brown-paper-bag release adds two headers that should have been included with SpeexDSP 1.2rc2. These are needed to build the resampler with NEON optimizations and to build SpeexDSP without the Speex codec library.

  • Speex 1.2rc2 and SpeexDSP 1.2rc2 are out

    December 6, 2014

    This release splits the speex codec library and the speex DSP library into separate source trees. Both projects received build-system improvements, bugfixes, and cleanup. The speex codec's VBR tuning was improved, while the speexdsp resampler got some NEON optimizations.

  • Speex 1.2rc1 is out

    July 23, 2008

    This release adds support for acoustic echo cancellation with multiple microphones and multiple loudspeakers. It also adds an API to decorrelate loudspeaker signals to improve multi-channel performance. In the bugfix department, there are fixes for a few bugs in the echo canceller, jitter buffer and preprocessor. At this point, the API for 1.2 should be stable and only a few very minor additions are planned.

  • Speex 1.2beta3 is out

    December 11, 2007

    The most obvious change in this release is that all the non-codec components (preprocessor, echo cancellation, jitter buffer) have been moved to a new libspeexdsp library. Other changes include a new jitter buffer algorithm and resampler improvements/fixes. This is also the first release where libspeex can be built without any floating point support. To do this, the float compatibility API must be disabled (--disable-float-api or DISABLE_FLOAT_API) and the VBR feature must be disabled (--disable-vbr or DISABLE_VBR).