DivX

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.

History

Name

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.

Early work

DivX ;-) 3.11 Alpha and later 3.xx versions refers to a hacked version of the Microsoft MPEG-4 Version 3 (MPEG-4v3, Microsoft internal numbering scheme, unrelated to MPEG-4 parts) video codec (which was actually not MPEG-4 compliant), extracted around 1998 by French hacker Jérome Rota (also known as Gej) in Montpellier. The Microsoft codec, which originally required that the compressed output be put in an ASF file, was altered to allow other containers such as Audio Video Interleave (AVI). Rota hacked the Microsoft codec because newer versions of the Windows Media Player wouldn't play his video portfolio and résumé that were encoded with it. Instead of re-encoding his portfolio, Rota and German hacker Max Morice decided to reverse engineer the codec, which "took about a week".

From 1998 through 2002, independent enthusiasts within the DVD-ripping community created software tools which dramatically enhanced the quality of video files that the DivX ;-) 3.11 Alpha and later 3.xx versions could produce. One notable tool is Nandub, a modification of the open-source VirtualDub, which features two-pass encoding (termed "Smart Bitrate Control" or SBC) as well as access to internal codec features.

DivXNetworks

In early 2000, Jordan Greenhall recruited Rota to form a company (originally called DivXNetworks, Inc., renamed to DivX, Inc. in 2005) to create clean-room DivX and steward its development. This effort resulted first in the release of the "OpenDivX" codec and source code on January 15, 2001. OpenDivX was hosted as an open-source project on the Project Mayo web site hosted at projectmayo.com (the name comes from "mayonnaise", because, according to Rota, DivX and mayonnaise are both "French and very hard to make." ). The company's internal developers and some external developers worked jointly on OpenDivX for the next several months, but the project eventually stagnated.

In early 2001, DivX employee "Sparky" wrote a new and improved version of the codec's encoding algorithm known as "encore2". This code was included in the OpenDivX public source repository for a brief time, but then was abruptly removed. The explanation from DivX at the time was that "the community really wants a Winamp, not a Linux." It was at this point that the project forked. That summer, Rota left the French Riviera and moved to San Diego "with nothing but a pack of cigarettes" where he and Greenhall founded what would eventually become DivX, Inc.

DivX took the encore2 code and developed it into DivX 4.0, initially released in July 2001. Other developers who had participated in OpenDivX took encore2 and started a new project—Xvid—that started with the same encoding core. DivX, Inc. has since continued to develop the DivX codec, releasing DivX 5.0 in March 2002. By the release of version 5.2.1 on September 8, 2004, the DivX codec was substantially feature-complete. Changes since then have tended to focus on speed, and encouraging wider hardware player support.

DivX formats

DivX Media Format (DMF)

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 DMF file contains 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 added 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.

Features

The current version of the DivX Community Codec for the Windows platform is version 6.8, and for Mac OS X is 6.7, both available from the DivX website. The latest version of the DivX package for Windows 2000/XP (which contains DivX Player 6.6, DivX Community Codec 6.8, and DivX Web Player 1.4) is version 6.8, released November, 2007. DivX Player 6.5 now fixes the problem of the player forcing Vista out of Aero mode (although the Web Player still has this problem as of version 1.3.1). The latest version of the DivX package for Mac OS X (which contains DivX Player 2.1, DivX Community Codec 6.6.0, DivX Converter 1.2 and DivX Web Player 1.3.1) is version 6.7, released Dec 12, 2007. In addition, an unofficial DivX for Linux codec update has also been released at version 6.1.1.

The DivX codec and DivX Player are available for free at the DivX website. Paying customers can access additional features of the DivX codec in the registered version, known as DivX Pro, and can also use DivX Converter, a one-click encoding application as a revamp of Dr.DivX and associated encoding tools (such as the Electrokompressiongraph, or EKG, which helped increase the viewability of highly compressed high-motion scenes). The latest version of DivX Converter for Windows is 6.5, and the latest version of DivX Converter for Mac is 1.2. Current versions however do access a domain name server.

Web player

Recently DivX has also released the DivX Web Player 1.0.1 (formerly known as the DivX Browser Plug-In Beta) via the DivX Labs website, demonstrating 720p HD playback live inside major browsers for Windows and Mac OS. Dr DivX 2 OSS, an Open Source DivX transcoding application, is available from SourceForge.

Gaming system compatibility

On December 4, 2007, native MPEG-4 ASP playback support was added to the Xbox 360. This means video encoded with DivX and other MPEG-4 ASP codecs can be played back on Xbox 360.

On December 17, 2007, the version 2.10 update for the Sony PlayStation 3 was released and included official DivX Certification.

Profiles

DivX has defined many profiles, which are sets of MPEG-4 features as determined by DivX. Because the grouping is different from what is specified in the MPEG-4 standard, there is a DivX-specific device certification process for device manufacturers. DivX's profiles differ from the standardized profiles of the ISO/IEC MPEG-4 international standard.

Profiles
Handheld Portable Home Theater High Def
Version 5+ 3.11 4+ 3.11+ 4+
Max. resolution (px×px×Hz) 176×144×15 352×240×30, 352×288×25 720×480×30, 720×576×25 720×480×30, 720×576×25 1280×720×30; 6.5: 1920×1080×30
Macroblocks (kHz) 1.485 9.9 40.5 40.5 108
Max. average bitrate (Mbit/s) 0.2 0.768 4 4 4
Max. peak bitrate (Mbit/s) 0.4 2 8 8 20
Min. VBV buffer size (KiB) 33 128 384 384 768

Encoding applications

Dr.DivX is an application created by DivX, Inc. that is capable of transcoding many video formats to DivX encoded video. The original closed source Dr.DivX terminated at version 1.06 for DivX 5.21, that was the last version of DivX capable of running under Windows 9x/Me. Work on an open source version has begun. Dr.DivX OSS offers greatly expanded features over the free DivX Converter application, that was bundled with the codec from version 6 onwards.

Other applications exist, such as AutoGK, VirtualDub, TMPGEnc and DVDx.

Competitors

The main competitors in the proprietary commercial video compression software market are Microsoft's Windows Media Video series, Apple Inc.'s QuickTime, and the RealNetworks RealVideo series.

While DivX has long been renowned for its excellent video quality, its free and open source equivalent Xvid today offers comparable quality, also based on MPEG-4 Part 2 (MPEG-4 ASP). In a series of subjective quality tests at Doom9.org between 2003 and 2005, the DivX codec was beaten by Xvid every year. Similar tests were not undertaken for newer versions.

The open source library libavcodec can decode and encode MPEG-4 video that can be encoded and decoded with DivX (and other MPEG-4 codecs, such as Xvid or libavcodec MPEG-4). Combined with image postprocessing code from the MPlayer project, it has been packaged into a DirectShow filter called ffdshow, which can be used for playback with most Windows video players. This library is highly customizable and offers a great variety of features to advanced users.

Since the standardization of H.264/MPEG-4 AVC, also known as MPEG-4 Part 10, a new generation of codecs has arisen, such as x264 and Nero AG's Nero Digital AVC codec. Despite being at a relatively early stage of development, these codecs out-performed DivX in Doom9's 2005 quality test, thanks to the more advanced features of MPEG-4 Part 10. Part 10's advanced features come at a cost: AVC decoding is two to three times more CPU intensive compared to MPEG-4 ASP; lightweight algorithms used in faster modes of DivX (or Xvid) codec allow one to achieve reasonable quality in a small fraction of time required to take advantage of all features of AVC. So far, DivX Labs has released a new alpha of a new codec based on the H.264 specification.

Adware in prior versions

At one point, DivXNetworks offered for download an "ad supported" version of their DivX Professional product free of charge to users who were willing to view advertisements. The ads were delivered by the GAIN ad server software. While this attracted much criticism at the time, users had to manually select the "ad supported" download rather than the for-pay professional version or the free version. Additionally, users were informed during installation of the ad-supported version that the Gator software would be installed on their PC and were presented with a license agreement to which they had to consent in order to continue the installation. Regardless, the Gator software would still install parts of itself without the user agreeing to this installation, and was difficult to remove after installation. This raised considerable consternation amongst DivX users, causing many to turn to its free software rival, Xvid. The latter is freely available without installing adware and has been demonstrated in independent comparisons to produce better quality output (see section on competitors above).

Due to the generally hostile opinion towards adware on the Internet, DivXNetworks announced on the DivX web site that, from July 15, 2004, no further DivX software would incorporate any adware. Free versions of DivX Pro before 5.2 typically contained spyware. From 5.2 onwards, including version 6, no spyware was included. When accessed in April 2007, the Professional version of DivX was only available in the form of a paid release or a 15-day free trial with no adware included. The DivX Player remains available in a long-term free license.

See also

References

External links

  • DivX Labs Community DivX website, with betas and ongoing projects

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