XviD

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XviD is a free and open source MPEG-4 video codec. XviD was created by a group of volunteer programmers after the OpenDivX source was closed in July 2001.

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 spelled backwards). While DivX is closed source and may only run on Windows, Mac OS and Linux, XviD is open source and can potentially run on any platform.

Contents

History

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, which 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".

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". 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. 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, all the openDivX code has been replaced and XviD has been published under the GPL license.

Legal issues

Some features of XviD are believed to be covered by software patents in a number of countries (notably United States and Japan). 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. (See mailing list discussions [1], [2], [3].)

Sigma Designs controversy

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 GPL'ed 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 [4]. 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 [5] and The Inquirer [6], in August 2002 Sigma Designs agreed to publish their source code [7].

Playing XviD encoded files

Due mostly to concern over patents, the official homepage does not provide binary versions of XviD. Codecs (DirectShow filters) for Microsoft's Windows are available at Koepi's XviD homepage. For Linux users, many distributions provide the XviD codec for use with media player software, such as MPlayer and VLC (however, all of them use built-in MPEG-4 decoder from FFmpeg by default and therefore don't require XviD, some of them don't even offer the option to use XviD at all).

Since XviD uses MPEG-4 Advanced Simple Profile (ASP) compression, video encoded with XviD can be decoded with other MPEG-4 compliant decoders as well. Many media players also support the MPEG-4 format used by XviD. See comparison of media players for a list of media players capable of playing XviD encoded content.

See also

External links

Retrieved from "http://mediacoder.sourceforge.net/wiki/index.php/XviD"

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