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Speex: A Free Codec For Free Speech

Overview

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 Xiph.org variant of the 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)
  • In-progress fixed-point port
  • Acoustic echo canceller

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; 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, OpenH323, and GnomeMeeting are some of the projects currently using Speex. For a list of projects with Speex support, visit our Plugins & Software page.

If you are interested in participating in the project, have a look at our roadmap, contact the Project Lead, Jean-Marc Valin, or join our mailing list. Or send us money so we can keep working on Speex.

Headlines

  • Speex 1.2beta1: Better, smaller, faster and more

    September 4, 2006

    This new release brings many significant improvements. The quality has been improved, both at the encoder level and the decoder level. These include enhancer improvements (now on by default), input/output high-pass filters, as well as fixing minor regressions in previous 1.1.x releases. A strange and rare instability problem with pure sinusoids has also been fixed. On top of that, memory use has been greatly reduced, especially for fixed-point and narrowband. The fixed-point narrowband encoder+decoder memory use has been cut by more than half, making it possible to fit both in less than 6 kB of RAM. In general, CPU requirement had gone down, especially for the fixed-point port. The Blackfin port has been speeded up significantly, thanks to David Rowe. There are also a few fixes for the TI C5X DSPs, as well as better support for C++ compilers and crappy MS compilers. Oh, and before anyone starts worrying, the format (bit-stream) itself has not changed, so Speex is still compatible with version 1.0 and will continue to be in the future.

    Non-codec improvements include a extension (easier to use) to the echo canceller API and a Speex-independent version of the jitter buffer. The echo canceller should also be more robust to saturation in the capture path. Last, but not least, the documentation has been updated.

  • How the Echo Canceller works

    August 7, 2006

    Always wanted to know how the Speex echo canceller works? On Adjusting the Learning Rate in Frequency Domain Echo Cancellation With Double-Talk has just been accepted for IEEE Trans. on Audio, Speech and Language Processing.

  • New website design

    August 6, 2006

    We have a new website design. There may be a few problems, so please report them and be patient.

  • On How Speex Works

    March 19, 2006

    Interested in how Speex works? Have a look at "Improved Noise Weighting in CELP Coding of Speech - Applying the Vorbis Psychoacoustic Model To Speex", authored by Jean-Marc Valin and Christopher Montgomery.

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