Xvid

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Xvid

Latest release:	1.1.2 / November 1, 2006
OS:	Cross-platform
Use:	Video codec
License:	GNU General Public License
Website:	http://www.xvid.org/

Xvid (formerly "XviD") is a video codec library following the MPEG-4 standard. Xvid features MPEG-4 Advanced Simple Profile features such as b-frames, global and quarter pixel motion compensation, lumi masking, trellis quantization, and H.263, MPEG and custom quantization matrices.

Xvid is a primary competitor of DivX (Xvid being DivX spelled backwards). While DivX is proprietary software, Xvid is free and open source software and, unlike DivX, can be used on many different platforms and operating systems.

1 History
2 Legal issues
3 Sigma Designs controversy
4 Playing Xvid encoded files
5 Encoding applications
6 References
7 See also
8 External links

In January 2001, DivXNetworks founded OpenDivX as part of Project Mayo which was intended to be a home for open source multimedia projects. OpenDivX was an open-source MPEG-4 video codec based on a stripped down version of the MoMuSys reference MPEG-4 encoder. The source code, however, was placed under a restrictive license and only members of the DivX Advanced Research Centre (DARC) had write access to the project CVS. In early 2001, DARC member Sparky wrote an improved version of the encoding core called encore2. This was updated several times before, in April, it was removed from CVS without warning. The explanation given by Sparky was "We (our bosses) decided that we are not ready to have it in public yet."^{[citation needed]}

In July 2001, developers started complaining about a lack of activity in the project; the last CVS commit was several months before, bugfixes were being ignored, and promised documentation had not been written. Soon after, DARC released a beta version of their closed-source commercial DivX 4 codec, which was based on encore2, saying that "what the community really wants is a Winamp, not a Linux."^{[citation needed]} Many accused DivXNetworks of starting OpenDivX for the sole purpose of harvesting other people's ideas to use in their DivX 4 codec, some were disappointed that the codec had stagnated and wanted to continue working on it, while others were angry at the way DivXNetworks handled a so-called open source project.^{[citation needed]} It was after this that a fork of OpenDivX was created, using the latest version of encore2 that was downloaded before it was removed. Since then, all the OpenDivX code has been replaced and Xvid has been published under the GNU General Public License.

Some features of Xvid are believed to be covered by software patents in a number of countries (notably United States and Japan).^{[citation needed]} For this reason, Xvid 0.9.x versions were not licensed in countries where these types of patents are enforceable. With the 1.0.x releases, a GNU GPL v2 license is used with no explicit geographical restriction. However, the legal usage of Xvid may still be restricted by local laws.^[1]

In July 2002, Sigma Designs released an MPEG-4 video codec called the REALmagic MPEG-4 Video Codec. Before long, people testing this new codec found that it contained considerable portions of Xvid code. Sigma Designs was contacted and confirmed that a programmer had based REALmagic on Xvid, but assured that all GPL code would be replaced to avoid copyright infringement. When Sigma Designs released the supposedly rewritten REALmagic codec, the Xvid developers immediately disassembled it and concluded that it still contained Xvid code, only rearranged in an attempt to disguise its presence. The Xvid developers decided to stop work and go public to force Sigma Designs to respect the terms of the GPL. After articles were published in Slashdot^[2] and The Inquirer,^[3] in August 2002 Sigma Designs agreed to publish their source code.^[4]

Due primarily to concerns over patents, the official Xvid homepage does not provide binary versions of the Xvid codec. Video for Windows codecs (and DirectShow decoding-only filters) for Microsoft Windows are, however, made available at supporting websites. For Linux users, many distributions provide an Xvid codec for use with media players such as MPlayer and VLC. However, all these players use the FFmpeg MPEG-4 decoder by default and therefore don't require (or don't support) decoding with the Xvid codec.

Since Xvid uses MPEG-4 Advanced Simple Profile (ASP) compression, video encoded with Xvid is MPEG-4 ASP video and can therefore be decoded with all MPEG-4 ASP compliant decoders. This includes a large number of media players, in particular all the ones based on the free/open source libavcodec library.

Xvid encoded files can be written to a CD or DVD and played in a DivX compatible DVD player. However, since Xvid specifies three warp points for its implementation of Global Motion Compensation as opposed to the one of DivX, enabling some of the more advanced encoding features can compromise player compatibility. Some issues exist with the default Quantization Matrix used in tools such as AutoGK that create an MPEG-4 stream with Xvid. These produce videos that have unstable playback and artifacts on DivX compatible DVD players.

A QuickTime Xvid component is available for Mac OS X.^[5]

See also: Comparison of media players#Video format support

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Two popular applications used to encode video using Xvid are DVDx and VirtualDub.