DivX

DivX is a brand name of products created by DivX, Inc. (formerly DivXNetworks, Inc.), including the DivX Codec which has become popular due to its ability to compress lengthy video segments into small sizes while maintaining relatively high visual quality. The DivX codec uses lossy MPEG-4 Part 2 compression, also known as MPEG-4 ASP, where quality is balanced against file size for utility. It is one of several codecs commonly associated with "ripping", whereby audio and video multimedia are transferred to a hard disk and transcoded. Many newer "DivX Certified" DVD players are able to play DivX encoded movies, although the Qpel and global motion compensation features are often omitted to reduce processing requirements. They are also excluded from the base DivX encoding profiles for compatibility reasons.

The "DivX" brand is distinct from "DIVX" (Digital Video Express), an unrelated attempt by the U.S. retailer Circuit City to develop a DVD rental system requiring special discs and players. The winking emoticon in the early "DivX ;-)" codec name was a tongue-in-cheek reference to the failed DIVX system. The DivX company then adopted the name of the popular DivX ;-) codec (which was not created by them), dropped the smiley and released DivX 4.0, which was actually the first DivX version (that is, DivX ;-) and DivX are two different things created by different people, the former is not an older version of the latter). The DivX name is its trademark. It is pronounced div-ex.

The latest generation, DivX 6, was released on June 15, 2005 and expands the scope of DivX from including just a codec and a player by adding a media container format. This optional new file format introduced with DivX 6 is called "DivX Media Format" ("DMF") (with a .divx extension) that includes support for the following DVD-Video and VOB container like features.

DivX Media Format (DMF) features:

• Interactive video menus
• Multiple subtitles (XSUB)
• Multiple audio tracks
• Multiple video streams (for special features like bonus/extra content, just like on DVD-Video movies)
• Chapter points
• Other metadata (XTAG)
• Multiple format
• Partial backwards compatibility with AVI

This new "DivX Media Format" also came with a "DivX Ultra Certified" profile, and all "Ultra" certified players must support all "DivX Media Format" features. While video encoded with the DivX codec is an MPEG-4 video stream, the DivX Media Format is analogous to media container formats such as Apple's QuickTime. In much the same way that media formats such as DVD specify MPEG-2 video as a part of their specification, the DivX Media Format specifies MPEG-4-compatible video as a part of its specification. However, despite the use of the ".divx" extension, this format is an extension to the AVI file format. The methods of including multiple audio and even subtitle tracks involve storing the data in RIFF headers and other such AVI hacks which have been known for quite a while, such that even VirtualDubMod supports them. DivX, Inc. did this on purpose to keep at least partial backwards compatibility with AVI, so that players that do not support the new features available to the .divx container format (like interactive menus, chapter points and XSUB subtitles) can at least play that primary video stream (usually the main movie if the .divx contain multiple video streams like special features like bonus materials). Of course, the DivX codec and tools like Dr.DivX still support the traditional method of creating standard AVI files.

DivX Subtitles (XSUB)

DivX, Inc. have since DivX 6 their own proprietary subtitle tracks that they call "XSUB" (which they also trademarked as XSUB). These subtitles are not text-based like many other subtitles, instead they are bitmap (digital image) based like vobsub subtitles for DVD-Video are. And like vobsubs for DVD-Video are supposed to be, XSUB does not come in standalone files but are only embedded in .divx containers, which can be created with Dr.DivX, (Dr.DivX can actually convert/encode XSUB from vobsubs inside DVD-Video). A .divx container can contain multiple XSUB subtitles in several languages.

DivX metadata (XTAG)

DivX, Inc. have since DivX 6 used their own proprietary metadata tags, for information tagging, that they call "XTAG" (which they also trademarked as XTAG). These tags are only supposed to be embedded into .divx containers. Most other containers have their own metadata format and the players usually use them, the most used tags on music files are probably ID3 (ID3v1/ID3v2) and APEv2.