The open-source voice chat program, Mumble, has updated to version 1.2.4 and now features the Opus codec:
This new codec will allow Mumble to perform better at even lower bitrates then previously possible. It incorporates technology from Skype’s SILK codec and Xiph.Org’s CELT codec, previously the main codec for Mumble.
Mumble’s announcement post also mentions gaining support from Valve:
We are also happy to see our positional audio technology seeing wider adoption in the gaming world with Valve including support in many of their source engine games. Namely Team Fortress 2, Half-Life 2: Deathmatch, Counter-Strike: Source and Day of Defeat: Source on all supported platforms including Linux and Mac OS X.
Positional audio allows you to hear your teammates from the position they are in-game without any changes to your Mumble server. On any game server.
For more information and downloads visit the Mumble homepage.