Editing Theora (section)

===Theora I specification===
[[File:I-15bis.ogg|thumb|Example of a Theora video used on [[Wikipedia]], showing a [[Polikarpov I-15]] biplane at an aerobatic display.]]
The Theora I bitstream format was [[Freeze (software engineering)|frozen]] in June 2004 after the libtheora 1.0alpha3 release.<ref name="theora-freeze"/> Videos encoded with any version of the libtheora since the alpha3 will be compatible with any future player.<ref name="theora-freeze" /><ref name="theora-news">{{citation
  | title = Theora.org : news | date = 24 September 2009
  | author = Xiph.Org Foundation  | publisher = Xiph.Org Foundation
  | url = https://theora.org/news/ | access-date = 19 May 2025
}}</ref> 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.<ref name="theoraspec-2004">{{Cite web | author=Xiph.Org Foundation | title = Theora I Specification, Xiph.org Foundation, September 17, 2004 | url = http://www.theora.org/doc/Theora_I_spec.pdf  | access-date=26 September 2009 | date = 17 September 2004 |archive-url = https://web.archive.org/web/20040928224506/www.theora.org/doc/Theora_I_spec.pdf |archive-date = 28 September 2004}}</ref> Any later changes in the specification are minor updates.

The Theora reference implementation libtheora spent several years in [[Software release life cycle#Alpha|alpha]] and beta status.<ref name="theora-news" /> The first alpha version was released on 25 September 2002 and the first beta version was released on 22 September 2007.<ref name="CHANGES">{{cite web |title=CHANGES file |url=https://gitlab.xiph.org/xiph/theora/-/blob/master/CHANGES |accessdate=19 May 2025 }}</ref> The first stable release of libtheora was made in November 2008.<ref>{{cite mailing list | url = http://lists.xiph.org/pipermail/theora-dev/2008-November/003736.html | title = Theora 1.0 final release! | mailing-list = theora-dev | date = 3 November 2008 | last = Giles |first = Ralph |access-date=4 November 2008}}</ref><ref>{{cite press release
  | title = The Xiph.Org Foundation announces the release of Theora 1.0
  | publisher = Xiph.Org Foundation | date = 3 November 2008
  | url = https://www.xiph.org/press/2008/theora-release-1.0/ | access-date = 19 May 2025
}}</ref> 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.<ref name="theora-news" /><ref>{{cite mailing list | url = https://lists.xiph.org/pipermail/theora-dev/2009-September/003985.html | title = libtheora 1.1 (Thusnelda) stable release | mailing-list = theora-dev | date = 24 September 2009 | last = Giles |first = Ralph |access-date=19 May 2025}}</ref> This release brought some technical improvements and new features, such as the new rate control module and the [[two-pass encoding|two-pass rate control]].

The codename for the next version of libtheora was ''Ptalarbvorm''.<ref name="ptalarbvorm">{{Cite web | author=Monty | title = Theora: Ptalarbvorm project update 20100518 | url = http://people.xiph.org/~xiphmont/demo/theora/demo9.html | access-date=1 July 2010 | date = 18 May 2010 }}</ref>

Theora was well established as a video format in [[open-source software|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 [[Use of Ogg formats in HTML5|resulted in controversy]].<ref>{{cite web
  | last = McLean | first = Prince | title = Ogg Theora, H.264 and the HTML 5 Browser Squabble
  | publisher = AppleInsider | date = 7 July 2009
  | url = https://appleinsider.com/articles/09/07/07/ogg_theora_h_264_and_the_html_5_browser_squabble | access-date = 1 November 2020
}}</ref>