[3] Xiph.Org now considers Speex obsolete; its successor is the more modern Opus codec, which uses the SILK format under license from Microsoft and surpasses its performance in most areas except at the lowest sample rates.

The design goals have been to make a codec that would be optimized for high quality speech and low bit rate.

Since Speex was designed for VoIP instead of cell phone use, the codec must be robust to lost packets, but not to corrupted ones.

All this led to the choice of code excited linear prediction (CELP) as the encoding technique to use for Speex.

The main characteristics can be summarized as follows: There are a large base of applications supporting the Speex codec.

ASL Safety & Security's[19] Linux based VIPA OS software[20] which is used in long line public address systems and voice alarm systems at major international air transport hubs and rail networks.

The Vernier LabQuest[21] handheld data acquisition device for science education uses Speex for voice annotations created by students and teachers using either the built-in or an external microphone.

This article uses material from the Speex Codec Manual which is copyright © Jean-Marc Valin and licensed under the terms of the GFDL.