XviD is an open-source research project focusing on video compression and is a collaborative development effort. All code is released under the terms of the GNU GPL license.
The Xvid video codec implements MPEG-4 Simple Profile and Advanced Simple Profile standards. It permits compressing and decompressing digital video in order to reduce the required bandwidth of video data for transmission over computer networks or efficient storage on CDs or DVDs. Due to its unrivalled quality Xvid has gained great popularity and is used in many other GPLed applications, like e.g. Transcode, MEncoder, MPlayer, Xine and many more.
Download: Xvid 1.2.2 Windows, Linux