DivX

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This article is about the video codec DivX. For the pay-per-view DVD system, see DIVX.

DivX

Developer:	DivX, Inc.
Latest release:	6.5.1 / January 27, 2007
OS:	Cross-platform
Use:	Media player / Codec / Media format
License:	proprietary
Website:	www.divx.com

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, where audio and video multimedia are transferred to a hard disk and transcoded. As a result, DivX has been a center of controversy because of its use in the replication and distribution of copyrighted DVDs. Many newer "DivX Certified" DVD players are able to play DivX encoded movies, although the Qpel and GMC features are often omitted to reduce processing requirements. They are also excluded from the base DivX encoding profiles for compatibility reasons.

[edit] Name

"DivX" should not be confused with "DIVX", an unrelated and unsuccessful attempt by the US retailer Circuit City to develop a new DVD rental system. This system eliminated the need to return rented DVDs through the use of a dedicated DIVX player that restricted the period of time during which the rented DVD could be viewed, but consumer response to this type of control was not favorable. 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, dropped the smiley and released DivX 4.0, which was actually the first DivX version. The DivX name is their trademark.

[edit] Early work

DivX ;-) 3.11 Alpha and later 3.xx versions refers to a hacked version of the Microsoft MPEG-4 Version 3 video codec (which was actually not MPEG-4 compliant), extracted around 1998 by French hacker Jérome Rota (also known as Gej). The Microsoft codec, which originally required that the compressed output be put in an ASF file, was altered to allow other containers such as 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 ^[1] decided to reverse engineer the codec, which "took about a week". ^[2]

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.

[edit] DivXNetworks

In early 2000, Jordan Greenhall recruited Rota to form a company (originally called DivXNetworks, Inc., renamed to DivX, Inc. in 2005) to create 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." ^[2]). 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"^[3] where he and Greenhall founded what would eventually become DivX, Inc. ^[2]

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. The company released a clean room version of the codec as DivX 4.0 in July 2001. 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 2004-09-08, the DivX codec was substantially feature complete. [2] Changes since then have tended to focus on speed, and encouraging wider hardware player support.

[edit] Stage6

Stage6 is a website that was created in 2006. It is similar to sites like YouTube in the fact that it allows streaming videos to be uploaded freely by anyone who is willing to register. The difference between Stage6 and other streaming video sites is that due to the higher upload limit the video quality is substantially greater.

[edit] 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" (or "DMF" for short) (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 basicaly the AVI file format by another name. 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) they 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.

[edit] 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 subtitles for DVD-Video are suppose to, 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 VubSub subtitles inside DVD-Video). A .divx container can contain multiple XSUB subtitles, like for example subtiles in several languages.

[edit] DivX metadata (XTAG)

DivX, Inc. have since DivX 6 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, (which can be created with Dr.DivX). 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.

[edit] Competing container formats

Matroska open source (uses .mkv as extension) includes support for DVD-Video like menus
NUT patent-free and open source extensible multimedia container
MP4 (MPEG-4 Part 14) container format standard specified as a part of MPEG-4
VOB the container format used in DVD-Video (uses .VOB .IFO and .BUP combined as extensions)
ratDVD closed source proprietary format based on VOB (the DVD-Video container format)
OGM ("Ogg Media", open source container from Xiph.org for their codecs)

[edit] Spyware 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 adverts in question were delivered by the notorious Gator adware software. While this attracted much criticism at the time, it should be noted that 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. Unfortunately, the Gator software would still install parts of itself without the user agreeing to this installation, and was notoriously difficult to remove after installation; this raised considerable consternation amongst DivX users, causing many to turn to its Open Source 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 below).

Due to the generally hostile opinion towards spyware on the Internet, DivXNetworks announced on the DivX.com web site that, from July 15, 2004, no further DivX software would incorporate any adware [3]. 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 March 2006, the Professional version of DivX was only available in the form of a paid release or a 6-month free trial with no adware included.

[edit] Current version

The current version of the DivX Community Codec, which is the same for all platforms, is version 6.4, available from DivX.com. The latest version of the DivX package for Windows 2000/XP (which contains DivX Player 6.4.0.13, DivX Community Codec 6.5.1, and DivX Web Player 1.3.0) is version 6.5, and the latest version of the DivX package for Mac OS X (which contains DivX Player 1.0.4, DivX Community Codec 6.4.0, and DivX Web Player 1.2.0) is version 6.6, released November 30, 2006. 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 6.2.1, and the latest version of DivX Converter for Mac is 1.1.2. Current versions however do access a domain name server.

[edit] Web player

Recently DivX have 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.

[edit] DivX 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. ^[4] DivX's profiles differ from the standardized profiles of the ISO/IEC MPEG-4 international standard.

Profiles
	Handheld	Portable	Home Theater	High Def
Supports all resolutions up to maximum of	DivX 5.xx only 176x144 @ 15 fps	DivX 4.xx & 5.xx 720x480 @ 30 fps; 720x576 @ 25 fps DivX 3.11 352x240 @ 30 fps; 352x288 @ 25 fps	DivX 3.11, 4.xx & 5.xx 720x480 @ 30 fps 720x576 @ 25 fps	DivX 4.xx & 5.xx 1280x720 @ 30 fps DivX 6.5x & later 1920x1080 @ 60 fps
Macroblocks per second	1485	DivX 4.xx & 5.xx 40500 DivX 3.11 9900	40500	108000
Maximum average bitrate	200 kbps	DivX 4.xx & 5.xx 4000 kbps DivX 3.11 768 kbps	4000 kbps	4000 kbps
Maximum peak bitrate during any 1 second of video	400 kbps	DivX 4.xx & 5.xx 8000 kbps DivX 3.11 2000 kbps	8000 kbps	20000 kbps
Minimum VBV buffer size	32 KiB	DivX 4.xx & 5.xx 384 KiB DivX 3.11 128 KiB	384 KiB	768 KiB

[edit] Encoding applications

The original closed source Dr.DivX terminated at version 1.06 for DivX 5.21. 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 and DVDx.

[edit] Open source

An open source version of the codec—called OpenDivX®—was released by DivX in early 2001, and this version served as the basis for the open source Xvid codec, the source code of which is largely maintained by Xvid Solutions.

[edit] Competitors

The main competitors in the for-license commercial video compression software market are Adobe's Flash 8 (using ON2's VP6), Microsoft's Windows Media Video series, Apple Computer'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). Xvid is funnily enough spelled like "DivX" backwards. In a series of subjective quality tests at Doom9.org, the DivX codec has been successively beaten by Xvid every year since 2003; 2003, 2004 2005

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 and reportedly achieves higher image quality on playback while generating less CPU load than the DivX decoder^[5].

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. 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: they are two to three times more CPU intensive than the relatively lightweight algorithms used in the DivX codec. It remains to be seen whether DivX will release a new codec based on the newer specification, like the Xvid team did with their Xvid AVC codec (not yet released to the public).

[edit] References

^ DVD & Internet Piracy - What is the Truth Behind It?. Retrieved on December 9, 2006.
^ ^a ^b ^c Escaping the Napster trap. Retrieved on March 15, 2001.
^ DivX CEO on Video, YouTube, iPod. Retrieved on December 8, 2006.
^ [1] DivX Profiles from support forums
^ ffdshow review from afterdawn.com, accessed 17 August 2006

[edit] See also

[edit] Competing technologies

[edit] Compatible software

Dr.DivX

[edit] Compatible Hardware

Hardware DivX players
Xbox running XBMC

[edit] External links

DivX.com The official DivX website
DivX Labs Community DivX website, with betas and ongoing projects
DivX Media Format The page where you can download the "DivX Media Format File SDK" (aka .divx file format)
DivX resources at the Open Directory Project (suggest site)