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Title: Theora  
Author: World Heritage Encyclopedia
Language: English
Subject: Ogg, FLAC, Speex, Vorbis, Comparison of video codecs
Collection: Articles Containing Video Clips, Free Video Codecs, Software Using the Bsd License, Xiph.Org Projects
Publisher: World Heritage Encyclopedia


Filename extension .ogv, .ogg
Internet media type video/ogg
Developed by
Initial release 1 June 2004 (2004-06-01)[1]
Latest release
Theora I
(16 March 2011[2])
Type of format Compressed video
Contained by Ogg, Matroska
Extended from VP3
Standard Specification
Open format? Yes [3]
Initial release 3 November 2008 (2008-11-03) (1.0)
Stable release 1.1.1 / 1 October 2009 (2009-10-01)[4]
Preview release 1.2.0 Alpha 1 / 24 September 2010 (2010-09-24)[5]
Development status Inactive
Written in C
Operating system Unix-like (incl Linux, Mac OS X), Windows
Type Video codec, reference implementation
License 3-clause BSD

Theora is a Vorbis audio format and the Ogg container.

The libtheora

  • Examples of Theora-encoded videos
  • Why Theora Matters for Internet TV
  • Theora user manual
  • RTP Payload Format for Theora Encoded Video – Xiph.Org, IETF Internet-Draft
  • WorldHeritage's controversial video player coming soon
  • H.264 and Theora codecs comparison

External links

  1. ^ a b c Giles, Ralph (1 June 2004). "Theora I bitstream freeze". theora-dev (Mailing list). Retrieved 25 September 2009. 
  2. ^ a b c d "Theora Specification" (PDF). Xiph.Org Foundation. 16 March 2011. Retrieved 31 January 2012. 
  3. ^ "PlayOgg! - FSF - Free Software Foundation". 2010-03-17. Retrieved 2013-10-01. 
  4. ^ "Theora 1.1.1 release". Xiph.Org Foundation. Retrieved 6 October 2009. 
  5. ^ "libtheora 1.2.0alpha1 release". Xiph.Org Foundation. Sep 2010. Retrieved 10 October 2010. 
  6. ^ Theora .
  7. ^ Xiph.Org Foundation. "libtheora Documentation 1.1.0". Xiph.Org Foundation. Retrieved 25 September 2009. 
  8. ^  
  9. ^ "Theora FAQ". Xiph.Org Foundation. Retrieved 6 August 2009. 
  10. ^ "Matroska Codec Specs". Matroska. Retrieved 6 August 2009. 
  11. ^ a b libtheora license (Subversion – Trunk), Retrieved on 16 August 2009
  12. ^ a b FAQ – Theora and VP3. Retrieved 2 September 2009
  13. ^ On2 (17 May 2000), Launches Next Generation of Revolutionary Broadband Video Technology, archived from the original on 3 December 2007 
  14. ^ On2 (16 August 2000), On2 Introduces TrueMotion VP3.2, archived from the original on 3 December 2007, retrieved 23 August 2010 
  15. ^ On2 (7 August 2001), On2 Technologies to Open Source VP3.2 Video Compression Technology (archived website), archived from the original on 3 December 2007 
  16. ^ Mariano, Gwendolyn (7 August 2001). "On2's video codec to go open-source". CNET. 
  17. ^ a b On2 Technologies (2001), VP3.2 Public License 0.1, Xiph.Org Foundation, retrieved 10 February 2008 
  18. ^ Bernat, Bill (7 September 2001). "On2 Offers Up VP3.2 Source Code". 
  19. ^ On2 (7 September 2001), On2 Technologies Makes Video Compression Technology Available to Open-Source Community, archived from the original on 7 December 2007 
  20. ^ Seibert, Stan (VP3.2 video codec open sourced). "VP3.2 video codec open sourced". vorbis (Mailing list). 
  21. ^ "On2 Alters Licensing Terms for VP3; Company Responds to Open Source Community Demands." (Press release). On2 Technologies. 28 March 2002. 
  22. ^ Xiph.Org Foundation (16 March 2011). "Theora Specification" (PDF). Xiph.Org Foundation. p. 1. 
  23. ^ On2 (24 June 2002), VP3 Combines with Vorbis to Create First Open-Source Multimedia Platform, archived from the original on 3 December 2007 
  24. ^ (23 June 2002) Ogg Vorbis, VP3 combining forces to create Open Source multimedia package, Retrieved on 2009-08-16
  25. ^ (24 June 2002) On2 Throws More Open-Source at MPEG-4, Retrieved on 16 August 2009
  26. ^ VP32 codec license (Subversion – Trunk), Retrieved on 16 August 2009
  27. ^ The Free Library (1 August 2002) On2 Signs Pact With to Develop/Support VP3, Retrieved on 16 August 2009
  28. ^ On2 (3 October 2002), On2 and Xiph Announce Alpha Code Release of Theora, VP3-Vorbis-Based Multimedia Solution, archived from the original on 4 December 2007 
  29. ^ Mike Melanson (mike at (8 December 2004), VP3 Bitstream Format and Decoding Process,, retrieved 27 September 2009 
  30. ^ a b c Xiph.Org Foundation (24 September 2009), : news, Xiph.Org Foundation, retrieved 25 September 2009 
  31. ^ Xiph.Org Foundation (17 September 2004). "Theora I Specification, Foundation, September 17, 2004" (PDF). Archived from the original (PDF) on 28 September 2004. Retrieved 26 September 2009. 
  32. ^
  33. ^ Giles, Ralph (3 November 2008). "Theora 1.0 final release!". theora-dev (Mailing list). Retrieved 4 November 2008. 
  34. ^ "The Xiph.Org Foundation announces the release of Theora 1.0" (Press release). Xiph.Org Foundation. 3 November 2008. Retrieved 6 August 2009. 
  35. ^ Giles, Ralph (24 September 2009). "libtheora 1.1 (Thusnelda) stable release". theora-dev (Mailing list). Retrieved 24 September 2009. 
  36. ^ Monty (18 May 2010). "Theora: Ptalarbvorm project update 20100518". Retrieved 1 July 2010. 
  37. ^ McLean, Prince (6 July 2009). "Ogg Theora, H.264 and the HTML 5 Browser Squabble". RoughlyDrafted Magazine. Retrieved 14 February 2010. 
  38. ^ "MPEG-4 Codec shoot-out 2002 – 1st installment".  
  39. ^ Codec shoot-out 2005 – Qualification,  
  40. ^ Loli-Queru, Eugenia (12 December 2007). "Theora vs. h.264".  
  41. ^ Halbach, Till (March 2009). "Dirac and Theora vs. H.264 and Motion JPEG2000". Retrieved 22 April 2008. 
  42. ^ DiBona, Chris (13 June 2009). "H.264-in- 
  43. ^ Maxwell, Greg (13 June 2009). "YouTube / Ogg/Theora comparison". Xiph.Org Foundation. Retrieved 10 August 2009. 
  44. ^ Maik, Merten (15 June 2009). "Another online-video comparison". Xiph.Org Foundation. Retrieved 10 August 2009. 
  45. ^ Montgomery, Chris. "Theora "the push for 1.0" update". Retrieved 19 December 2007. 
  46. ^ Blizzard, Christopher. "Theora Update 7 May 2009". Retrieved 10 May 2009. 
  47. ^ Richmond, Gary. "Firefogg: Transcoding videos to open web standards with Mozilla Firefox". Retrieved 14 February 2010. 
  48. ^ "Xiph Subversion repository: trunk/theora-fpga". Xiph.Org Foundation. Retrieved 10 August 2009. 
  49. ^ "XiphWiki: Theora Hardware". Xiph.Org Foundation. Retrieved 10 August 2009. 
  50. ^ MozillaWiki (18 March 2009), Firefox3.5/Features, MozillaWiki, retrieved 11 October 2009 
  51. ^ Mozilla Corporation (30 June 2009), Mozilla Firefox 3.5 Release Notes, Mozilla Corporation, retrieved 11 October 2009 
  52. ^ Mozilla Corporation (9 February 2010), Firefox Mobile Features, Mozilla Corporation, retrieved 9 February 2010 
  53. ^ Google Chrome to support HTML 5 video, SoftSailor, 28 May 2009, retrieved 11 October 2009 
  54. ^ Stephen Shankland (28 May 2009), Google Chrome gets HTML video support, cnet news, retrieved 11 October 2009 
  55. ^ Issue 16657: Ensure FFmpeg binaries end up in snapshots on all platforms, google chromium issues list, 14 July 2009, retrieved 6 February 2010 
  56. ^ Robert Kaiser (16 September 2009), What's New in SeaMonkey 2.0 Beta 2,, retrieved 11 October 2009 
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  58. ^ Plans for Konqueror 4.4, 26 November 2009, retrieved 2 December 2009 
  59. ^ Philip Jägenstedt (31 December 2009). "(re-)Introducing  
  60. ^ Arjan van Leeuwen (31 December 2009). "Happy New Year! – Official blog for Core developers at Opera". Opera. Archived from the original on 4 January 2010. Retrieved 2 January 2010. 
  61. ^ Experimental Opera-video build with native Ogg Theora support, Opera, 25 April 2007, archived from the original on 2 December 2007, retrieved 11 October 2009 
  62. ^ A call for video on the web – Opera , Opera, 7 November 2007, retrieved 11 October 2009 
  63. ^ alp (4 February 2010). "HTML5 Theora Video Codec for Silverlight". Alp Toker blog. Retrieved 14 February 2010. The Highgate media suite will bring installation-free support for HTML5 streaming video 
  64. ^ "ffdshow Summary". Retrieved 23 October 2009. 
  65. ^ Cutka, Milan (4 October 2002). "Theora support in ffdshow a ffvfw". theora-dev (Mailing list). 
  66. ^ "Theora in .ogg no only .avi – ffdshow tryouts Forum". 15 January 2008. Retrieved 23 October 2009. 
  67. ^ "GStreamer Base Plugins 0.10 (". Retrieved 23 October 2009. 
  68. ^ "GStreamer Base Plugins 0.10 Plugins Reference Manual – Theora plugin library". Retrieved 23 October 2009. 
  69. ^ Ogg Video Tools on SourceForge


See also

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


[2] Theora Streaming Studio is a complete client to connect to an Icecast server.

Name Description Operating Systems Supported
Unix-like OS X Windows
Yes Yes Yes
Yes ? Yes
Peer-to-peer streaming. Written in Java Yes ? Yes
Can stream ogg/theora/vorbis in realtime to a file or fifo. Yes Yes ?
Streaming media server. Yes ? ?

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


Name Description Operating Systems Supported
Unix-like OS X Windows
Video editing software for Linux. Can edit, encode and stream theora. Yes Yes ?
The KDE video editor. Yes ? ?
Yes ? ?
The GNOME video editor. Yes ? ?
CVS versions of the Cinelerra non-linear video editing system support Theora, as of August 2005. Yes Yes ?
oggz-tools by
Command line programs to examine and edit Ogg files. Yes ? Yes
Ogg Video Tools by yornstreamnik
Tools to resize, cut, split, join, and others[69] Yes Yes Yes
AVS Video Editor
? ? Yes


  • 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.[64][65][66] 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 aren't 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[67][68]

Also, several media frameworks have support for Theora.

The libtheora library contains the reference implementation of the Theora specification for encoding and decoding. libtheora is still under development by the BSD-style license.

Name Description Operating Systems Supported
Unix-like OS X Windows
A Firefox browser extension implementation of ffmpeg2theora Yes Yes Yes
A command-line program that transcodes video by decoding with FFmpeg and reencoding with libtheora to encode it Yes Yes Yes
Can transcode to single-pass Theora 1.0 and optionally stream it Yes Yes Yes
Transcodes supported media to Vorbis, Theora, or Dirac Yes ? Yes
"Video DJing" software that can encode to and stream Theora Yes Yes ?
The video editor supplied with KDE Yes ? ?
The video editor supplied with GNOME Yes ? ?
Video editing software for Linux. Can edit, encode and stream theora. Yes Yes ?
A GTK+ and GStreamer based DVD backup utility Yes ? ?
Can output to Theora only with the Matroska container Yes Yes Yes
Records the screen to Ogg Theora with optional Vorbis audio Yes ? ?

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


Supporting applications

Supporting media frameworks

Browser plugins

  • Mozilla Firefox 3.5 and later versions[50][51] including Firefox for mobile (Fennec).[52]
  • Google Chrome as of version[53][54] including Chromium as of 14 July 2009.[55]
  • Tizen browser
  • SeaMonkey as of version 2.0.[56]
  • Konqueror 4.4.2[57][58]
  • Opera as of version 10.50.[59][60] It was also supported in Opera 9.5 experimental video builds.[61][62]
  • 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+.

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

Native browser playback


There is an open source VHDL code base for a hardware Theora decoder in development.[48] It began as a 2006 Google Summer of Code project, and it has been developed on both the Nios II and LEON processors.[49] 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. But since decoding Theora is less CPU intensive than decoding H.264, the need for hardware-accelerated Theora decoding may be somewhat less.

Playback performance

The performance characteristics of the Theora 1.0 reference implementation are dominated mostly by implementation problems inherited from the original VP3 code base.[45] Work leading up to the 1.1 stable release was focused on improving on or eliminating these. A May 2009 review of this work shows a considerable improvement in quality, both subjectively and as measured by PSNR, just by improving the forward DCT and quantisation matrices.[46] A flaw in the version of FFmpeg used in the test initially led to incorrect reports of Theora PSNR surpassing that of H.264. Although not achieving this goal, the improvement in the measured PSNR and the perceived quality is considerable. In any case, the differences in quality, bitrate and file size between a YouTube H.264 video and a transcoded Ogg video file are negligible.[47] Further work on adaptive quantization, as well as overall detailed subjective tuning of the codec, is still to come.

Evaluations of the VP3[38] and early Theora encoders[39] [40] [41] found that their subjective visual quality was inferior to that of contemporary video codecs. More recently however, Xiph developers have 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.[42] 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.[43][44]

Encoding performance


Theora is well established as a video format in open source applications, and is the format used for WorldHeritage's video content. However, the proposed adoption of Theora as part of the baseline video support in HTML5 resulted in controversy.[37]

The codename for the next version of libtheora is Ptalarbvorm.[36]

The Theora reference implementation libtheora spent several years in alpha and beta status.[30] The first alpha version was released on 25 September 2002[32] and the first beta version was released on 22 September 2007. The first stable release of libtheora was made in November 2008.[33][34] 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.[30][35] This release brought some technical improvements and new features, such as the new rate control module and the two-pass rate control.

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][30] 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.[31] Any later changes in the specification are minor updates.

Example of a Theora video used on WorldHeritage, showing a Polikarpov I-15 biplane at an aerobatic display.

Theora I specification

Project Daala is working on the successor to Theora.

[29][2] There is no formal specification for VP3's

[28], Theora's reference implementation.libtheora On2 declared Theora to be VP3's successor. On 3 October 2002, On2 and Xiph announced the completion and availability of the initial alpha code release of [27] In March 2002, On2 responded to the public's reception by relicensing the VP3 codec under the

In August 2001, On2 Technologies announced that they would be releasing an open source version of their VP3.2 video compression algorithm.[15][16] In September 2001, On2 Technologies published the source code of the VP3.2 codec under the VP3.2 Public License 0.1,[17] a custom open-source license.[18][19] The license only granted the right to modify the source code if the resulting larger work continued to support playback of VP3.2 data.[17][20]

Move to free software

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[13] and followed three months later by the VP3.2 release,[14] which is the basis for Theora.


The Theora video-compression format is essentially compatible with the VP3 video-compression format, consisting of a backward-compatible superset.[11][12] 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).[12] VP3 video compression can be decoded using Theora implementations, but Theora video compression usually cannot be decoded using old VP3 implementations.

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 provides a completely open, royalty-free multimedia format. It can also be used with the Matroska container.[10]

Theora is a variable-bitrate, DCT-based video compression scheme. Like most common video codecs, Theora also uses 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]

Technical details


  • Technical details 1
  • History 2
    • Move to free software 2.1
    • Theora I specification 2.2
  • Performance 3
    • Encoding performance 3.1
    • Playback performance 3.2
  • Playback 4
    • Native browser playback 4.1
    • Browser plugins 4.2
    • Supporting media frameworks 4.3
    • Supporting applications 4.4
  • Encoding 5
  • Editing 6
  • Streaming 7
  • Makers 8
  • See also 9
  • References 10
  • External links 11

Theora is named after Theora Jones, Edison Carter's Controller on the Max Headroom television program.[9]

Theora is 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 lacking some of the features present in some of these other codecs. It is comparable in open standards philosophy to the BBC's Dirac codec.


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