Editing Dirac (video compression format) (section)

==Technology==

Dirac supports resolutions of [[HDTV]] (1920×1080) and greater, and is claimed to provide significant savings in data rate and improvements in quality over video compression formats such as [[MPEG-2 Part 2]], [[MPEG-4 Part 2]] and its competitors such as [[Theora]] and [[Windows Media Video|WMV]]. Dirac's implementers made a preliminary claim of "a two-fold reduction in bit rate over MPEG-2 for high definition video", which makes it comparable to [[VC-1]] and simpler profiles of [[H.264/MPEG-4 AVC|H.264]].<ref name="dirac-overview">{{cite web |url=http://www.bbc.co.uk/rd/projects/dirac/overview.shtml |title=Dirac Overview |publisher=[[BBC Research & Development]] |access-date=14 January 2009 |url-status=dead |archive-url=https://web.archive.org/web/20130109021949/http://www.bbc.co.uk/rd/projects/dirac/overview.shtml |archive-date=9 January 2013 }}</ref>

Dirac supports both [[constant bit rate]] and [[variable bit rate]] operation. When the low delay syntax is used, the bit rate will be constant for each area (Dirac slice) in a picture to ensure constant latency. Dirac supports [[lossy]] and [[lossless]] compression modes.<ref name="Dirac-2.2.3"/>

Dirac employs [[wavelet compression]], like the [[JPEG 2000]] and [[Progressive Graphics File|PGF]] image formats and the [[Cineform]] professional video codec, instead of the [[discrete cosine transform]]s used in [[MPEG]] compression formats. Two of the specific wavelets Dirac can use are nearly identical to JPEG 2000's (known as the [[Cohen-Daubechies-Feauveau wavelet|5/3 and 9/7 wavelets]]), as well as two more derived from them.<ref>{{cite web |url=http://dirac.sourceforge.net/documentation/algorithm/algorithm/wlt_transform.xht |title=Dirac: Wavelet transform |first=Thomas |last=Davies |date=6 February 2008 |access-date=9 September 2015 |archive-date=8 May 2015 |archive-url=https://web.archive.org/web/20150508094001/http://dirac.sourceforge.net/documentation/algorithm/algorithm/wlt_transform.xht |url-status=live }}</ref>

Dirac can be used in [[Ogg]] and [[Matroska]] [[container format (digital)|container formats]] and is also registered for use in the [[ISO base media file format|ISO base media (MP4)]] file format and [[MPEG transport stream]]s.<ref name="MP4RA-codecs">{{Cite web |url=https://mp4ra.org/#/codecs |work=MP4 Registration Authority |title=Codecs |publisher=[[International Standards Organisation]] |access-date=18 December 2023 |archive-date=7 October 2023 |archive-url=https://web.archive.org/web/20231007124717/https://mp4ra.org/#/codecs |url-status=live }}</ref><ref name="TS-ids">{{Cite web |title=List of Registered MPEG TS Identifiers |url= https://smpte-ra.org/registered-mpeg-ts-ids |work=SMPTE Registration Authority |publisher=[[Society of Motion Picture and Television Engineers]] |archive-url= https://web.archive.org/web/20090421041153/http://smpte-ra.org/mpegreg/drac.html |archive-date=21 April 2009 |access-date=18 December 2023 |url-status=live }}</ref>

===Patents===

The BBC does not own any patents on Dirac. They previously had some patent applications with plans to irrevocably grant a royalty-free licence for their Dirac-related patents to everyone, but they let the applications lapse. In addition, the developers have said they will try to ensure that Dirac does not infringe on any third party patents, enabling the public to use Dirac for any purpose.<ref name="FAQ"/>