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Job Notes/DivX & DivX Ultra

DivX

晴空 2009. 8. 10. 12:17

From Wikipedia, the free encyclopedia


This article is about the video codec. For the pay-per-view DVD system, see DIVX (Digital Video Express). For the company behind the codec, see DivX, Inc..

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 compression, 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.

Contents

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 History

The "DivX" brand is distinct from "DIVX" (Digital Video Express), an unrelated attempt by the now defunct U.S. retailer Circuit City to develop a video rental system requiring special discs and players.[1] The winking emoticon in the early "DivX ;-)" codec name was a tongue-in-cheek reference to the failed DIVX system.[2] 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.[3][4] It is pronounced DIV-ex.

 Early works

DivX ;-) (not DivX) 3.11 Alpha and later 3.xx versions refers to a hacked version of the Microsoft MPEG-4 Version 3 video codec (MPEG-4v3, Microsoft internal numbering scheme, unrelated to MPEG-4 parts) from Windows Media Tools 4 codecs.[5][6] The video codec, which was actually not MPEG-4 compliant, was extracted around 1998 by French hacker Jerome Rota (also known as Gej) at Montpellier. The Microsoft codec originally required that the compressed output be put in an ASF file. It 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".[7]

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.

 Later works

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." [7]). 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"[8] where he and Greenhall founded what would eventually become DivX, Inc. [7]

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.[9] Changes since then have tended to focus on speed, and encouraging wider hardware player support, while the company has also focused its time on the formats and next generation codecs.

 DivX formats

 DivX Media Format (DMF)

DivX Media Format
DivX media container icon
Filename extension .divx
Type code DIVX
Developed by DivX, Inc.
Type of format media container
Container for DivX encoded video and other media
Extended from Matroska, AVI

DivX 6 expanded 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. has, since DivX 6, added its own proprietary subtitle tracks that it calls "XSUB" (which has also been trademarked as XSUB)[citation needed]. 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.

 Features

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).

On the 6th of January 2009, DivX 7 was released, which added H.264 video, AAC audio and Matroska container support, surpassing the restrictions of their previous formats.[10] The DivX Converter 7 still supports DivX 6 profiles, but DivX Plus HD needs to be selected to make a file in the new format. When using DivX 7 in the converter the only option available is to limit filesize, but a more configurable CLI client is available from DivX Labs.[11] Since it can only create raw H.264 streams a Matroska muxer must be used.

 Web player

DivX has also released the DivX Web Player (formerly known as the DivX Browser Plug-In) demonstrating HD playback live inside major browsers for Windows and Mac OS.[12]

 Gaming system compatibility

On December 4, 2007, native MPEG-4 ASP playback support was added to the Xbox 360.[13] This means almost all video encoded with DivX and other MPEG-4 ASP codecs can be played back on Xbox 360.[14]

On December 17, 2007, the version 2.10 update for the Sony PlayStation 3 was released and included official DivX Certification. The PS3 also supports the DivX Video on Demand (DivX VOD) service as of firmware version 2.50 released on October 15, 2008.

On January 20, 2009, the version 2.60 update for the Sony PlayStation 3 was released and included official DivX Certification and updated Profile support to version 3.11.[15]

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

Profiles
Handheld (deprecated) Portable (deprecated) qMobile Mobile Home Theater High Def
Version 5+ 3.11 4+ 5+ 5+ 3.11+ 4+
Max. resolution (px×px×Hz) 176×144×15 352×240×30, 352×288×25 720×480×30, 720×576×25 177x144x15 320x240×30 720×480×30, 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 0.2 0.6 4 4
Max. peak bitrate (Mbit/s) 0.4 2 8 8 20
Min. VBV buffer size (KiB) 33 128 384 65 384 768

 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. An open source version has been made, which supports DivX 6. Dr. DivX offers greatly expanded features over the free DivX Converter application, that was bundled with the codec from version 6 onwards.[17]

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 the DivX codec has long been renowned for its excellent video quality, the free and open source Xvid codec offers comparable quality. Both the DivX encoder and the Xvid encoder are compliant with MPEG-4 Part 2 (MPEG-4 ASP). However, the most commonly used DivX encoding profile (Home Theater)[18] does not employ the same MPEG-4 ASP features enabled in the most commonly used Xvid encoding profile (home).[19] In a series of subjective quality tests at Doom9.org between 2003 and 2005, the DivX encoder was beaten by the Xvid encoder every year.[20] 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.

 Adware in versions before 5.2

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 This article contains weasel words, vague phrasing that often accompanies biased or unverifiable information. Such statements should be clarified or removed. (August 2009)

At one point[when?], DivXNetworks offered for download an "ad supported" version of their DivX Professional product free of charge to users who were willing to view advertisements.[citation needed] The ads were delivered by the GAIN ad server software.[citation needed] While this attracted[by whom?] much criticism at the time[citation needed], users were free to voluntarily select the "ad supported" download rather than the commercial 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.[citation needed][original research?] This raised considerable consternation amongst DivX users[weasel words], causing many[weasel words] to turn to its freeware rival, Xvid.[citation needed] 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[citation needed], DivXNetworks announced on the DivX web site that, from July 15, 2004, no further DivX software would incorporate any adware.[21] Free versions of DivX Pro before 5.2 typically contained spyware.[citation needed][neutrality disputed][original research?] From 5.2 onwards, 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.[citation needed] The DivX Player remains available in a long-term free license.[vague][citation needed]

 See also

DivX, Inc.
Other DivX Products
Related technologies
General Topics

 References

  1. ^ "The 25 Worst Tech Products of All Time". http://www.pcworld.com/article/125772-7/the_25_worst_tech_products_of_all_time.html. 
  2. ^ "DivX support coming to PlayStation 3". http://arstechnica.com/news.ars/post/20071113-divx-support-coming-to-playstation-3-xbox-360-support-in-the-works.html. 
  3. ^ "DivX Trademarks". http://www.divx.com/en/company/press/trademarks. 
  4. ^ "An Intellectual Property Case Study" (PDF). http://davidgrossman.name/Publications-Patents/DIVX%20IP%20Case%20Study.pdf. 
  5. ^ VirtualDub VirtualDub documentation: codecs, Retrieved on 2009-08-08
  6. ^ FOURCC.orgVideo Codecs - Compressed Formats, Retrieved on 2009-08-08
  7. ^ a b c "Escaping the Napster trap". http://archive.salon.com/tech/feature/2001/03/15/divx_part1/index.html. Retrieved on March 15 2001. 
  8. ^ "DivX CEO on Video, YouTube, iPod". http://www.redherring.com/Home/20135. Retrieved on December 8 2006. 
  9. ^ Answer
  10. ^ http://investors.divx.com/releasedetail.cfm?releaseid=357661
  11. ^ http://labs.divx.com/node/6992
  12. ^ labs.divx.com: Web Player's blog.
  13. ^ Xbox.com | Personalities - A Fistful of Features in the December 2007 System Update
  14. ^ "Xbox 360 DivX/XviD Playback Tested (Verdict: It's Almost Perfect)". Gizmodo. http://gizmodo.com/gadgets/xbox-360-divx%5Cxvid-test/xbox-360-divxxvid-tested-it-plays-almost-everything-329769.php. Retrieved on 2007-12-19. 
  15. ^ "Firmware 2.60 brings photo gallery, Divx 3.11". PS3Fanboy. http://www.ps3fanboy.com/2009/01/20/firmware-2-60-brings-photo-gallery-divx-3-11/. Retrieved on 2009-01-20. 
  16. ^ "DivX Profiles from support forums". http://support.divx.com/cgi-bin/divx.cfg/php/enduser/std_adp.php?p_faqid=1709. 
  17. ^ DivX Video Converter - Free Movie Converter Trial - Convert Video Files
  18. ^ DivX Home Theater Profile FAQs
  19. ^ Xvid Solutions Product Certification
  20. ^ Codec comparisons
  21. ^ [1][dead link]

 External links

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