Software:Theora

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Short description: Free lossy video compression format
Theora
Theora logo 2007.svg
Filename extension.ogv, .ogg
Internet media typevideo/ogg
Developed byXiph.org
Initial release1 June 2004 (2004-06-01)[1]
Latest release
Theora I
(16 March 2011[2])
Type of formatVideo coding format
Contained byOgg, Matroska
Extended fromVP3
StandardSpecification
Open format?Yes[3]
Websitetheora.org
libtheora
Developer(s)Xiph.org
Initial release3 November 2008 (2008-11-03) (1.0)
Stable release
1.1.1 / 1 October 2009; 14 years ago (2009-10-01)[5]
Preview release
1.2.0 Alpha 1 / 24 September 2010; 13 years ago (2010-09-24)[6]
Written inC
Operating systemUnix-like (incl Linux, Mac OS X), Windows
TypeVideo codec, reference implementation
License3-clause BSD
Websitewww.theora.org

Theora is a free lossy video compression format.[7] It was developed by the Xiph.Org Foundation and distributed without licensing fees alongside their other free and open media projects, including the Vorbis audio format and the Ogg container.

The libtheora video codec is the reference implementation of the Theora video compression format developed by the Xiph.Org Foundation.[8][9]

Theora was derived from the formerly proprietary VP3 codec, released into the public domain by On2 Technologies. It is broadly comparable in design and bitrate efficiency to MPEG-4 Part 2, early versions of Windows Media Video, and RealVideo while it lacked some of the features present in some of these other codecs. It is comparable in open standards philosophy to the BBC's Dirac codec.

Theora was named after Theora Jones, Edison Carter's Controller on the Max Headroom television program.[10]

Technical details

Theora is a variable-bitrate, DCT-based video compression scheme. Like most common video codecs, Theora used chroma subsampling, block-based motion compensation and an 8-by-8 DCT block. Pixels are grouped into various structures, namely blocks, super blocks, and macroblocks. Theora supports intra-coded frames and forward-predictive frames, but not bi-predictive frames which are found in H.264 and VC-1. Theora also does not support interlacing, or bit-depths larger than 8 bits per component.[2]

Theora video streams can be stored in any suitable container format, but they are most commonly found in the Ogg container with Vorbis or FLAC audio streams. This combination provided a completely open, royalty-free multimedia format. It can also be used with the Matroska container.[11]

The Theora video-compression format is compatible with the VP3 video-compression format, which consisted of a backward-compatible superset.[12][13] Theora is a superset of VP3, and VP3 streams (with some minor syntactic modifications) can be converted into Theora streams without recompression (but not vice versa).[13] VP3 video compression can be decoded using Theora implementations, but Theora video compression usually cannot be decoded using old VP3 implementations.

History

Theora's predecessor On2 TrueMotion VP3 was originally a proprietary and patent-encumbered video codec developed by On2 Technologies. VP3.1 was introduced in May 2000[14] and followed three months later by the VP3.2 release,[15] which was the basis for Theora.

Move to free software

In August 2001, On2 Technologies announced that they would release an open source version of their VP3.2 video compression algorithm.[16][17] In September 2001, On2 Technologies published the source code of the VP3.2 codec under the VP3.2 Public License 0.1,[18] a custom open-source license.[19][20] The license only granted the right to modify the source code if the resultant larger work continued to support playback of VP3.2 data.[18][21]

In March 2002, On2 responded to the public's reception by relicensing the VP3 codec under the GNU Lesser General Public License.[22] In June 2002, On2 donated VP3 to the Xiph.Org Foundation and offered it under the Ogg Vorbis BSD-style license.[23][24][25][26] On2 also made an irrevocable, royalty-free license grant for any patent claims it might have over the software and any derivatives,[2] allowing anyone to use any VP3-derived codec for any purpose.[12][27] In August 2002, On2 entered into an agreement with the Xiph.Org Foundation to make VP3 the basis of a new, free video codec, called Theora.[28] On2 declared Theora to be VP3's successor.[citation needed] On 3 October 2002, On2 and Xiph announced the completion and availability of the initial alpha code release of libtheora, Theora's reference implementation.[29]

There is no formal specification for VP3's bitstream format beyond the VP3 source code published by On2 Technologies. In 2003, Mike Melanson created an incomplete description of the VP3 bitstream format and decoding process at a higher level than source code, with some help from On2 and Xiph.Org Foundation. The Theora specification adopted some portions of this VP3 description.[2][30]

A successor to Theora, Daala, was later merged into AV1.[31]

Theora I specification

File:I-15bis.ogg The Theora I bitstream format was frozen in June 2004 after the libtheora 1.0alpha3 release.[1] Videos encoded with any version of the libtheora since the alpha3 will be compatible with any future player.[1][32] This is also true for videos encoded with any implementation of the Theora I specification since the format freeze. The Theora I Specification was completely published in 2004.[33] Any later changes in the specification are minor updates.

The Theora reference implementation libtheora spent several years in alpha and beta status.[32] The first alpha version was released on 25 September 2002 and the first beta version was released on 22 September 2007.[34] The first stable release of libtheora was made in November 2008.[35][36] Work then focused on improving the codec's performance in the "Thusnelda" branch, which was released as version 1.1 in September 2009 as the second stable libtheora release.[32][37] This release brought some technical improvements and new features, such as the new rate control module and the two-pass rate control.

The codename for the next version of libtheora was Ptalarbvorm.[38]

Theora was well established as a video format in open-source applications, and became the format used for Wikipedia's video content before replaced by VP9. However, the proposed adoption of Theora as part of the baseline video support in HTML5 resulted in controversy.[39]

Legacy

In October 2023, Google announced intent to remove Theora support from Chromium (finalizing removal by Google Chrome 123),[40] with Firefox following suit. Google developers claimed that despite lack of adoption, Theora made a case for open and royalty-free codecs like AV1.[41][better source needed]

Performance

Encoding performance

Evaluations of the VP3[42] and early Theora encoders[43][44][45] found that their subjective visual quality was inferior to that of contemporary video codecs. The performance characteristics of the Theora 1.0 reference implementation are dominated mostly by implementation problems inherited from the original VP3 code base.[46] Work that lead up to the 1.1 stable release focused on improving on or eliminating these. A May 2009 review of this work by Xiph developer Chris Montgomery claimed a considerable improvement in quality, both subjectively and as measured by PSNR, by improving the forward DCT and quantisation matrices.[47] More recently however,[when?] Xiph developers compared the 1.1 Theora encoder to YouTube's H.264 and H.263+ encoders, in response to concerns raised in 2009 about Theora's inferior performance by Chris DiBona, a Google employee.[48] They found the results from Theora to be nearly the same as YouTube's H.264 output, and much better than the H.263+ output.[49][50]

The differences in quality, bitrate and file size between a YouTube H.264 video and a transcoded Ogg video file are very small.[51]

Playback performance

There was an open-source VHDL code base for a hardware Theora decoder in development.[52][needs update] It began as a 2006 Google Summer of Code project, and it has been developed on both the Nios II and LEON processors.[53] However, there are currently no Theora decoder chips in production, and portable media players, smartphones and similar devices with limited computing power rely on such chips to provide efficient playback.

Playback

Web browsers

Main page: Use of Ogg formats in HTML5

As originally recommended by HTML 5, these browsers support Theora when embedded by the video element:

  • Mozilla Firefox 3.5 and later versions[54][55] including Firefox for mobile (Fennec).[56] Theora support may be removed in the future due to low usage.[57][58]
  • Google Chrome as of version 3.0.182.2[59][60] including Chromium as of 14 July 2009.[61] Chrome 120 disabled support for Theora by default[62] and the complete removal is expected in version 123.[63]
  • Tizen browser
  • SeaMonkey as of version 2.0.[64]
  • Konqueror 4.4.2[65][66]
  • Opera as of version 10.50.[67][68] It was also supported in Opera 9.5 experimental video builds.[69][70]
  • GNOME Web uses WebKitGTK+ as its rendering engine. As WebKitGTK+ uses GStreamer to implement the HTML5 media player, and all the formats GStreamer supports (including Theora) are available in browser.
  • Midori is another example of a browser that supports Theora by using WebKitGTK+.

Supporting media frameworks

  • DirectShow with use of OpenCodecs
  • Phonon
  • QuickTime (including but not limited to Safari) with use of Xiph QuickTime Components

Supporting applications

  • FFmpeg (own implementation)
  • Helix Player
  • Miro Media Player (formerly known as Democracy Player)
  • MPlayer and front-ends
  • Totem, Moovida and all GStreamer-based players
  • VLC (native support)
  • xine and all libxine-based players like Kaffeine
  • Dragon player and all Phonon-based players

Encoding

There are several third-party programs that support encoding through libtheora:

Name Description Operating Systems Supported
Unix-like OS X Windows
ffmpeg2theora[71]
 A command-line program that transcodes video by decoding with FFmpeg and reencoding with libtheora to encode it Yes Yes Yes
VLC
 Can transcode to single-pass Theora 1.0 and optionally stream it Yes Yes Yes
FreeJ
 "Video DJing" software that can encode to and stream Theora Yes Yes ?
Kdenlive
 The video editor supplied with KDE Yes ? ?
Pitivi
 The video editor supplied with GNOME Yes ? ?
LiVES
 Video editing software for Linux. Can edit, encode and stream theora. Yes Yes ?
HandBrake
 Can output to Theora only with the Matroska container Yes Yes Yes
RecordMyDesktop
 Records the screen to Ogg Theora with optional Vorbis audio Yes ? ?

The libtheora library contains the reference implementation of the Theora specification for encoding and decoding. libtheora was developed by the Xiph.Org Foundation. The library was released under the terms of a BSD-style license.

Also, several media frameworks have support for Theora.

  • The open-source ffdshow audio/video decoder is capable of encoding Theora videos using its Video for Windows (VFW) multi-codec interface within popular AVI editing programs.[72][73][74] It supports both encoding and decoding Theora video streams and uses Theora's alpha 4 libraries. However, many of the more refined features of Theora are not available to the user in ffdshow's interface.
  • The GStreamer framework has support for parsing raw Theora streams, encoding and decoding raw Theora streams to/from YUV video[75][76]

Editing

Name Description Operating Systems Supported
Unix-like OS X Windows
LiVES
 Video editing software for Linux. Can edit, encode and stream theora. Yes Yes ?
Kdenlive
 The KDE video editor. Yes ? ?
OpenShot
 Yes ? ?
Pitivi
 The GNOME video editor. Yes ? ?
Cinelerra
 CVS versions of the Cinelerra non-linear video editing system support Theora, as of August 2005. Yes Yes ?
oggz-tools by Xiph.org
 Command line programs to examine and edit Ogg files. Yes ? Yes
Ogg Video Tools by yornstreamnik
 Tools to resize, cut, split, join, and others[77] Yes Yes Yes
AVS Video Editor
 ? ? Yes

Streaming

The following streaming media servers are capable of streaming Theora video:

Name Description Operating Systems Supported
Unix-like OS X Windows
VLC
 Yes Yes Yes
Icecast
 Yes ? Yes
LiVES
 Can stream ogg/theora/vorbis in realtime to a file or fifo. Yes Yes ?

Makers

Elphel is the main maker of cameras that record in theora.

See also

References

  1. ↑ 1.0 1.1 1.2 Giles, Ralph (1 June 2004). "Theora I bitstream freeze". theora-dev (Mailing list). Retrieved 25 September 2009.
  2. ↑ 2.0 2.1 2.2 2.3 "Theora Specification". Xiph.Org Foundation. 16 March 2011. http://theora.org/doc/Theora.pdf. 
  3. ↑ "Theora FAQ". 2016. https://xiph.org/theora/faq/. 
  4. ↑ "PlayOgg! – FSF – Free Software Foundation". 2010-03-17. http://www.fsf.org/campaigns/playogg/en/. 
  5. ↑ "Theora 1.1.1 release". Xiph.Org Foundation. http://www.theora.org/news/#libtheora-1.1.1. 
  6. ↑ "libtheora 1.2.0alpha1 release". Xiph.Org Foundation. Sep 2010. http://lists.xiph.org/pipermail/theora-dev/2010-September/004202.html. 
  7. ↑ Theora, http://www.theora.org .
  8. ↑ Xiph.Org Foundation. "libtheora Documentation 1.1.0". Xiph.Org Foundation. http://theora.org/doc/libtheora-1.1/. 
  9. ↑ ohloh. "libtheora". ohloh. http://www.ohloh.net/p/libtheora. 
  10. ↑ "Theora FAQ". Xiph.Org Foundation. http://theora.org/faq/#15. 
  11. ↑ "Matroska Codec Specs". Matroska. http://www.matroska.org/technical/specs/codecid/index.html. 
  12. ↑ 12.0 12.1 Xiph.org libtheora license (Subversion – Trunk), Retrieved on 16 August 2009
  13. ↑ 13.0 13.1 Xiph.org FAQ – Theora and VP3. Retrieved 2 September 2009
  14. ↑ On2 (17 May 2000), On2.com Launches Next Generation of Revolutionary Broadband Video Technology, http://www.on2.com/index.php?id=486&news_id=407 
  15. ↑ On2 (16 August 2000), On2 Introduces TrueMotion VP3.2, http://www.on2.com/index.php?id=486&news_id=401, retrieved 23 August 2010 
  16. ↑ On2 (7 August 2001), On2 Technologies to Open Source VP3.2 Video Compression Technology (archived website), http://www.on2.com/index.php?id=486&news_id=365 
  17. ↑ Mariano, Gwendolyn (7 August 2001). "On2's video codec to go open-source". CNET. http://news.cnet.com/2100-1023-271254.html. 
  18. ↑ 18.0 18.1 On2 Technologies (2001), VP3.2 Public License 0.1, Xiph.Org Foundation, http://trac.xiph.org/browser/branches/vp32/vp32/VP32_license.txt, retrieved 10 February 2008 
  19. ↑ Bernat, Bill (7 September 2001). "On2 Offers Up VP3.2 Source Code". StreamingMedia.com. http://www.streamingmedia.com/Articles/ReadArticle.aspx?ArticleID=64360. 
  20. ↑ On2 (7 September 2001), On2 Technologies Makes Video Compression Technology Available to Open-Source Community, http://www.on2.com/index.php?id=486&news_id=364 
  21. ↑ Seibert, Stan (September 2001). "VP3.2 video codec open sourced". vorbis (Mailing list).
  22. ↑ "On2 Alters Licensing Terms for VP3; Company Responds to Open Source Community Demands" (Press release). On2 Technologies. 28 March 2002. Archived from the original on 4 December 2010. Retrieved 16 August 2009.
  23. ↑ Xiph.Org Foundation (16 March 2011). "Theora Specification". Xiph.Org Foundation. p. 1. http://theora.org/doc/Theora.pdf. 
  24. ↑ On2 (24 June 2002), VP3 Combines with Vorbis to Create First Open-Source Multimedia Platform, http://www.on2.com/index.php?id=486&news_id=313 
  25. ↑ Linux.com (23 June 2002) Ogg Vorbis, VP3 combining forces to create Open Source multimedia package, Retrieved on 2009-08-16
  26. ↑ InternetNews.com (24 June 2002) On2 Throws More Open-Source at MPEG-4, Retrieved on 16 August 2009
  27. ↑ Xiph.org VP32 codec license (Subversion – Trunk), Retrieved on 16 August 2009
  28. ↑ The Free Library (1 August 2002) On2 Signs Pact With Xiph.org to Develop/Support VP3, Retrieved on 16 August 2009
  29. ↑ On2 (3 October 2002), On2 and Xiph Announce Alpha Code Release of Theora, VP3-Vorbis-Based Multimedia Solution, http://www.on2.com/index.php?id=486&news_id=298 
  30. ↑ Mike Melanson (mike at multimedia.cx) (8 December 2004), VP3 Bitstream Format and Decoding Process, Multimedia.cx, http://www.multimedia.cx/vp3-format.txt, retrieved 27 September 2009 
  31. ↑ Stephen Shankland (2015-09-01). "Tech giants join forces to hasten high-quality online video". CNET. http://www.cnet.com/news/tech-giants-join-forces-to-hasten-high-quality-online-video/. 
  32. ↑ 32.0 32.1 32.2 Xiph.Org Foundation (24 September 2009), Theora.org : news, Xiph.Org Foundation, http://theora.org/news/, retrieved 25 September 2009 
  33. ↑ Xiph.Org Foundation (17 September 2004). "Theora I Specification, Xiph.org Foundation, September 17, 2004". http://www.theora.org/doc/Theora_I_spec.pdf. 
  34. ↑ "CHANGES file". https://gitlab.xiph.org/xiph/theora/-/blob/master/CHANGES. Retrieved 31 December 2022. 
  35. ↑ Giles, Ralph (3 November 2008). "Theora 1.0 final release!". theora-dev (Mailing list). Retrieved 4 November 2008.
  36. ↑ "The Xiph.Org Foundation announces the release of Theora 1.0" (Press release). Xiph.Org Foundation. 3 November 2008. Retrieved 6 August 2009.
  37. ↑ Giles, Ralph (24 September 2009). "libtheora 1.1 (Thusnelda) stable release". theora-dev (Mailing list). Retrieved 24 September 2009.
  38. ↑ Monty (18 May 2010). "Theora: Ptalarbvorm project update 20100518". http://people.xiph.org/~xiphmont/demo/theora/demo9.html. 
  39. ↑ McLean, Prince (7 July 2009). "Ogg Theora, H.264 and the HTML 5 Browser Squabble". AppleInsider. https://appleinsider.com/articles/09/07/07/ogg_theora_h_264_and_the_html_5_browser_squabble. 
  40. ↑ Larabel, Michael (2023-10-29). "Google Chrome To Remove Theora Video Codec Support" (in en). https://www.phoronix.com/news/Google-Chrome-Dropping-Theora. 
  41. ↑ "Intent to Ship: Deprecate and remove Theora support.". https://groups.google.com/a/chromium.org/g/blink-dev/c/qqDdLkeyk7Y/m/ajHePzglAwAJ. 
  42. ↑ "MPEG-4 Codec shoot-out 2002 – 1st installment". Doom9. 2002. http://www.doom9.org/codec-comparisons.htm. 
  43. ↑ Codec shoot-out 2005 – Qualification, Doom9, 2005, http://www.doom9.org/codecs-quali-105-3.htm, retrieved 19 December 2007 
  44. ↑ Loli-Queru, Eugenia (12 December 2007). "Theora vs. h.264". OSNews. http://www.osnews.com/story/19019/Theora-vs-h.264/. 
  45. ↑ Halbach, Till (March 2009). "Dirac and Theora vs. H.264 and Motion JPEG2000". http://etill.net/projects/dirac_theora_evaluation/. 
  46. ↑ Montgomery, Chris. "Theora "the push for 1.0" update". http://web.mit.edu/xiphmont/Public/theora/demo.html. 
  47. ↑ Blizzard, Christopher. "Theora Update 7 May 2009". http://web.mit.edu/xiphmont/Public/theora/demo7.html. 
  48. ↑ DiBona, Chris (13 June 2009). "H.264-in-<video> vs plugin APIs". whatwg (Mailing list). Retrieved 10 August 2009.
  49. ↑ Maxwell, Greg (13 June 2009). "YouTube / Ogg/Theora comparison". Xiph.Org Foundation. http://people.xiph.org/~greg/video/ytcompare/comparison.html. 
  50. ↑ Merten, Maik (15 June 2009). "Another online-video comparison". Xiph.Org Foundation. http://people.xiph.org/~maikmerten/youtube/. 
  51. ↑ Richmond, Gary. "Firefogg: Transcoding videos to open web standards with Mozilla Firefox". http://freesoftwaremagazine.com/articles/firefogg_transcoding_videos_open_web_standards_mozilla_firefox/. 
  52. ↑ "Xiph Subversion repository: trunk/theora-fpga". Xiph.Org Foundation. http://svn.xiph.org/trunk/theora-fpga/. 
  53. ↑ "XiphWiki: Theora Hardware". Xiph.Org Foundation. http://wiki.xiph.org/Theora_Hardware. 
  54. ↑ MozillaWiki (18 March 2009), Firefox3.5/Features, MozillaWiki, https://wiki.mozilla.org/Firefox3.5/Features, retrieved 11 October 2009 
  55. ↑ Mozilla Corporation (30 June 2009), Mozilla Firefox 3.5 Release Notes, Mozilla Corporation, http://www.mozilla.com/en-US/firefox/3.5/releasenotes/, retrieved 11 October 2009 
  56. ↑ Mozilla Corporation (9 February 2010), Firefox Mobile Features, Mozilla Corporation, http://www.mozilla.com/en-US/mobile/features/#cutting-edge, retrieved 9 February 2010 
  57. ↑ "Mozilla Eyes Removal Of Theora Support In Firefox" (in en). https://www.phoronix.com/news/Mozilla-Eyes-Dropping-Theora. 
  58. ↑ "1860492 – Investigate removing Theora support" (in en). https://bugzilla.mozilla.org/show_bug.cgi?id=1860492. 
  59. ↑ Google Chrome to support HTML 5 video, SoftSailor, 28 May 2009, http://www.softsailor.com/news/3787-3787.html, retrieved 11 October 2009 
  60. ↑ Shankland, Stephen (28 May 2009), Google Chrome gets HTML video support, cnet news, http://news.cnet.com/8301-17939_109-10250958-2.html, retrieved 11 October 2009 
  61. ↑ Issue 16657: Ensure FFmpeg binaries end up in snapshots on all platforms, Google Chromium, 14 July 2009, https://code.google.com/p/chromium/issues/detail?id=16657, retrieved 6 February 2010 
  62. ↑ Larabel, Michael (2023-12-07). "Chrome 120 Released With Theora Support Evaporating, Adds WebGPU & CSS Improvements" (in en). https://www.phoronix.com/news/Google-Chrome-120. 
  63. ↑ "Deprecate and remove Theora support. – Chrome Platform Status". https://chromestatus.com/feature/5158654475239424. 
  64. ↑ Kaiser, Robert (16 September 2009), What's New in SeaMonkey 2.0 Beta 2, seamonkey-project.org, http://www.seamonkey-project.org/releases/seamonkey2.0b2/changes, retrieved 11 October 2009 
  65. ↑ Bugreport: Wish for audio/video element support in Konqueror, 13 May 2007, https://bugs.kde.org/show_bug.cgi?id=145380, retrieved 2 December 2009 
  66. ↑ Plans for Konqueror 4.4, 26 November 2009, http://forum.kde.org/viewtopic.php?f=18&t=83851, retrieved 2 December 2009 
  67. ↑ Jägenstedt, Philip (31 December 2009). "(re-)Introducing <video> – Official blog for Core developers at Opera". Opera. http://my.opera.com/core/blog/2009/12/31/re-introducing-video. 
  68. ↑ Arjan van Leeuwen (31 December 2009). "Happy New Year! – Official blog for Core developers at Opera". Opera. http://my.opera.com/desktopteam/blog/happy-new-year. 
  69. ↑ Experimental Opera-video build with native Ogg Theora support, Opera, 25 April 2007, http://my.opera.com/ResearchWizard/blog/experimental-opera-video-build-with-native-ogg-theora-support, retrieved 11 October 2009 
  70. ↑ A call for video on the web – Opera <video> release on Labs, Opera, 7 November 2007, http://dev.opera.com/articles/view/a-call-for-video-on-the-web-opera-vid/, retrieved 11 October 2009 
  71. ↑ "ffmpeg2theora". http://v2v.cc/~j/ffmpeg2theora/. 
  72. ↑ "ffdshow Summary". http://sourceforge.net/projects/ffdshow-tryout/. 
  73. ↑ Cutka, Milan (4 October 2002). "Theora support in ffdshow a ffvfw". theora-dev (Mailing list).
  74. ↑ "Theora in .ogg no only .avi – ffdshow tryouts Forum". 15 January 2008. http://ffdshow-tryout.sourceforge.net/phpBB2/viewtopic.php?p=2459&sid=6a8a488dd3aebb9e35764e950de65d60. 
  75. ↑ gstreamer.freedesktop.org. "GStreamer Base Plugins 0.10 (0.10.24.1)". http://gstreamer.freedesktop.org/data/doc/gstreamer/head/gst-plugins-base-plugins/html/. 
  76. ↑ gstreamer.freedesktop.org. "GStreamer Base Plugins 0.10 Plugins Reference Manual – Theora plugin library". http://gstreamer.freedesktop.org/data/doc/gstreamer/head/gst-plugins-base-plugins/html/gst-plugins-base-plugins-plugin-theora.html. 
  77. ↑ "Ogg Video Tools - Browse Files at SourceForge.net". https://sourceforge.net/projects/oggvideotools/files/. 

External links



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