User:Rcooley~enwiki/Theora
| Filename extension |
.ogv |
|---|---|
| Internet media type |
video/ogg |
| Developed by | Xiph.Org Foundation |
| Type of format | Video codec |
| Contained by | Ogg |
| Extended from | VP3 |
| Standard | Specification |
Theora is an open and royalty-free lossy video compression technology being developed by the Xiph.Org Foundation as part of their Ogg project. Based upon On2 Technologies' VP3 codec, Theora is targeted at competing with MPEG-4, WMV, and similar low-bitrate video compression schemes.
Theora is named for Theora Jones, Edison Carter's Controller on the Max Headroom television program.
History
[edit]VP3 was originally a proprietary and patented video codec developed by On2 Technologies. VP3.1 was launched June 1, 2000.[1] It's successor, VP3.2, was launched September 1, 2000.[2]
On September 7, 2001, VP3.2 was donated to the public as free and open source software,[3] and On2 disclaimed all rights to it, including their patents on the technology, letting anyone use Theora and other VP3-derived codecs for any purpose.[4]
On June 24th, 2002, On2 entered into an agreement with the Xiph.Org Foundation, with On2 partially funding the Xiph.org development work to make VP3 the basis of a new, free video codec fully integrated with the Ogg multimedia container framework, named Theora.[5]
Xiph.org estimated they would relase a final/1.0 version of Theora by June 2003,[6] [7] but Theora actually remained in alpha version stage into 2006, and is now (May 2008) in a beta stage (beta 3) before the release of 1.0. The bitstream format was frozen with alpha 3 (July 2004), however, so videos encoded with any version of the Theora encoder since that date will continue to be compatible with any standard player/decoder, well into the future.
Technical details
[edit]Theora is a lossy video compression method derived from On2's VP3 Codec. The compressed video can be stored in any suitable container format. Theora video is generally included in Ogg container format. It is frequently paired with Vorbis audio.
The combination of the Ogg container format, Theora video and Vorbis audio allows for a multimedia format that is both royalty-free, and open source. Other open standard multimedia formats, such as MPEG-4 video and MP3 audio, are patented and subject to license fees for commercial use in many countries around the world.
Like many other image and video formats, VP3.2 and Theora use Chroma subsampling, block based motion compensation and an 8×8 DCT block. This is comparable to MPEG-1/2/4. It supports intra coded frames and forward predictive frames but not bi-predictive frames that can be found in many other video codecs. Unlike MPEG-1/2/4, but much like H.263, Theora also includes a simple in-loop deblocking filter.[8]
Theora's (incompatible) architectural developments since VP3.2 include the ability to use a few different color spaces, instead of exclusively 4:2:0, independent quantization tables for intra- and inter- frames, and the ability to select different video quantization tables on a frame-by-frame basis.
Performance/Quality
[edit]Independent performance/quality evaluations have found VP3[9] and Theora[10] [11] substantially lacking compared to contemporary video codecs, being (both) far more computationally complex (slower) than contemporary codecs, and lower quality, having been called comparable to the much older H.261 codec in visual quality.[12]
Xiph.org reject the assertion that Theora isn't any better than H.261, but concede that previous versions of Theora have poor quality compared to contemporary (MPEG-4 ASP and H.264/AVC based) video codecs. They have stated that the poor quality of the current Theora reference implementation is mostly dominated by implementation issues inherited from the original VP3 code base. Current development work on Theora is focused on improving the encoder to improve quality.
Patent Controversy
[edit]It is believed that VP3/Theora is free of any (enforceable) patents, however, numerous individuals and organizations have expressed concern that VP3/Theora may infringe on unknown ("submarine") patents.[13]
There is some evidence to support the notion that the technology behind VP3.2 is, in fact, free of (enforceable) patented technology (unencumbered):
- On2 has been selling the VP3 video codec and it's successors since 1999. After nearly a decade, On2 has not faced any patent infringement lawsuits.
- With patent expiration in the US at 20 years, VP3 having been around for a decade, and its predecessor codec having been around since 1992[14] there is only a fairly small window for valid patents on Theora's underlying technology. Any filed after their technology was in-use are therefore invalid by virtue of prior art, while any filed a few years before that have already expired.
- In August 2002, AOL subsidiary Nullsoft integrated the VP3.2 codec into Winamp 3, as part of the Nullsoft Streaming Video (NSV) technology for Shoutcast broadcasting of video over the internet.[15] AOL stated that they employed a patent attorney to search for any patents for which they would be liable, and found none.[citation needed] Nullsoft and AOL has thus far not faced any legal challenges by any individuals or companies over the use of VP3.2.
Encoding
[edit]The libtheora library contains the reference implementations of both the Theora encoder and decoder. libtheora is still under development by the Xiph.Org Foundation, which has made eight alpha releases and 3 major beta release thus far which include a complete rewrite of the decoder. The library is released under the terms of a BSD-style license.
There are also several third-party programs that support encoding through libtheora.
See also
[edit]
References
[edit]- ^ http://www.on2.com/index.php?id=486&news_id=407
- ^ http://www.on2.com/index.php?id=486&news_id=401
- ^ http://www.on2.com/index.php?id=486&news_id=367
- ^ VP3.2 Public License 0.1, 2001, retrieved 2008-02-10
- ^ http://www.on2.com/index.php?id=486&news_id=313
- ^ http://www.on2.com/index.php?id=486&news_id=298
- ^ http://web.archive.org/web/20020704113158/www.theora.org/theorafaq.html
- ^ http://theora.org/doc/Theora_I_spec.pdf
- ^ Doom9 (2002), MPEG-4 Codec shoot-out 2002 - 1st installment, retrieved 2007-12-19
{{citation}}: CS1 maint: numeric names: authors list (link) - ^ Doom9 (2005), Codec shoot-out 2005 - Qualification, retrieved 2007-12-19
{{citation}}: CS1 maint: numeric names: authors list (link) - ^ Loli-Queru, Eugenia (December 12, 2007), Theora vs. h.264, OSNews, retrieved 2008-04-01
{{citation}}: Check date values in:|date=(help)CS1 maint: date and year (link) - ^ Wenger, Stephan (December 12, 2007), Web Architecture and Codec Considerations for Audio-Visual Services (PDF), p. 3, retrieved 2007-12-19
{{citation}}: Check date values in:|date=(help)CS1 maint: date and year (link) - ^ http://www.w3.org/QA/2007/12/when_will_html_5_support_soone.html
- ^ http://web.archive.org/web/19970209090219/www.duck.com/whyduck.html
- ^ http://www.on2.com/index.php?id=486&news_id=308