Editing Theora (section)

===Encoding performance===
Evaluations of the VP3<ref>{{cite web | publisher = [[Doom9]] | title = MPEG-4 Codec shoot-out 2002 – 1st installment | year = 2002 | url = https://www.doom9.org/codec-comparisons.htm | access-date = 19 May 2025 | url-status = dead | archive-url = https://web.archive.org/web/20080223010804/http://www.doom9.org/codec-comparisons.htm | archive-date = 23 February 2008 }}</ref>
and early Theora encoders<ref>{{citation | publisher = [[Doom9]] | title = Codec shoot-out 2005 – Qualification | year = 2005 | url = https://www.doom9.org/index.html?/codecs-quali-105-3.htm | access-date = 19 December 2007 | url-status = dead | archive-url = https://web.archive.org/web/20071231133347/www.doom9.org/codecs-quali-105-3.htm | archive-date = 31 December 2007 }}</ref><ref>{{cite web
  | publisher = [[OSNews]] | first = Eugenia | last = Loli-Queru | title = Theora vs. h.264
  | date=12 December 2007 | url = https://www.osnews.com/story/19019/theora-vs-h264/ | access-date =19 May 2025 }}</ref><ref>{{cite web | last = Halbach, Till | title = Dirac and Theora vs. H.264 and Motion JPEG2000 | date = March 2009 | url = http://etill.net/projects/dirac_theora_evaluation/ | access-date = 22 April 2008 | url-status = dead | archive-url = https://archive.today/20120707194336/etill.net/projects/dirac_theora_evaluation/ | archive-date = 7 July 2012 }}</ref>
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.<ref>{{cite web
  | last = Montgomery | first = Chris
  | title = Theora "the push for 1.0" update
  | url = http://web.mit.edu/xiphmont/Public/theora/demo.html | access-date =19 December 2007
}}</ref> 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 [[Discrete cosine transform|DCT]] and quantisation matrices.<ref>{{cite web
  | last = Blizzard |first = Christopher
  | title = Theora Update 7 May 2009
  | url = http://web.mit.edu/xiphmont/Public/theora/demo7.html | access-date =10 May 2009
}}</ref>  More recently however,{{when|date=June 2021}} 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.<ref>{{cite mailing list
  | last = DiBona |first = Chris
  | title = H.264-in-&lt;video&gt; vs plugin APIs | mailing-list = whatwg | date = 13 June 2009
  | url = https://lists.whatwg.org/pipermail/whatwg-whatwg.org/2009-June/020380.html | access-date =19 May 2025
}}</ref> 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.<ref>{{cite web | last = Maxwell | first = Greg | title = YouTube / Ogg/Theora comparison | publisher = Xiph.Org Foundation | date = 13 June 2009 | url = http://people.xiph.org/~greg/video/ytcompare/comparison.html | access-date = 10 August 2009 | archive-date = 9 July 2009 | archive-url = https://web.archive.org/web/20090709062345/http://people.xiph.org//~greg//video//ytcompare//comparison.html | url-status = dead }}</ref><ref>{{cite web | last = Merten | first = Maik | title = Another online-video comparison | publisher = Xiph.Org Foundation | date = 15 June 2009 | url = http://people.xiph.org/~maikmerten/youtube/ | access-date = 10 August 2009 | archive-date = 9 July 2009 | archive-url = https://web.archive.org/web/20090709062338/http://people.xiph.org//~maikmerten//youtube// | url-status = dead }}</ref>

The differences in quality, bitrate and file size between a YouTube H.264 video and a transcoded Ogg video file are very small.<ref>{{cite web
  | last = Richmond |first = Gary
  | title = Firefogg: Transcoding videos to open web standards with Mozilla Firefox
  | url = http://freesoftwaremagazine.com/articles/firefogg_transcoding_videos_open_web_standards_mozilla_firefox/ | access-date =19 May 2025
}}</ref>