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Theora：修订间差异

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{{noteTA
{{noteTA
|G1=IT
|G1=IT
|1=zh-hant:智慧財產;zh-hans:知识财产;
}}
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{{Infobox file format
{{Infobox file format
| name = Theora
| name = Theora
| icon =
| logo = Theora logo 2007.svg
| extension = <code>.ogv, .ogg</code>
| extension = <code>.ogv, .ogg</code>
| mime = <code>video/ogg</code>
| mime = <code>video/ogg</code>
| owner = [[Xiph.Org基金會]]
| owner = [[Xiph.Org基金會]]
| released = {{start date|df=yes|2004|06|01}}<ref name= "theora-freeze">{{cite mailing list | url = http://lists.xiph.org/pipermail/theora-dev/2004-June/001112.html | title = Theora I bitstream freeze | mailinglist = theora-dev | date = 1 June 2004 | last = Giles |first = Ralph |accessdate= 25 September 2009}}</ref>
| released = {{start date|df=yes|2004|06|01}}<ref name= "theora-freeze">{{cite mailing list | url = http://lists.xiph.org/pipermail/theora-dev/2004-June/001112.html | title = Theora I bitstream freeze | mailinglist = theora-dev | date = 1 June 2004 | last = Giles | first = Ralph | accessdate = 25 September 2009 | archive-date = 2011-09-27 | archive-url = https://web.archive.org/web/20110927161643/http://lists.xiph.org/pipermail/theora-dev/2004-June/001112.html | dead-url = no }}</ref>
| type code =
| type code =
| genre = [[影像編碼]]
| genre = [[影像編碼]]
第16行： 第17行：
| extended from = [[VP3]]
| extended from = [[VP3]]
| extended to =
| extended to =
| free = 是<ref>{{cite web|url=http://www.fsf.org/campaigns/playogg/en/|title=PlayOgg! - FSF - Free Software Foundation |accessdate=2013-10-01|date=2010-03-17}}</ref>
| free = 是<ref>{{cite web|url=http://www.fsf.org/campaigns/playogg/en/|title=PlayOgg! - FSF - Free Software Foundation|accessdate=2013-10-01|date=2010-03-17|archive-date=2017-06-18|archive-url=https://web.archive.org/web/20170618131607/http://www.fsf.org/campaigns/playogg/en|dead-url=yes}}</ref>
| standard = [http://www.theora.org/doc/Theora.pdf Theora規格]
| standard = [http://www.theora.org/doc/Theora.pdf Theora規格]
}}
}}
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| discontinued =
| discontinued =
| latest_release_version = 1.1.1
| latest_release_version = 1.1.1
| latest_release_date = {{Release date and age|2009|10|01}}<ref>{{cite web| url = http://www.theora.org/news/#libtheora-1.1.1 | title = Theora 1.1.1 release |accessdate=6 October 2009 | publisher=Xiph.Org基金會}}</ref>
| latest_release_date = {{Release date and age|2009|10|01}}<ref>{{cite web | url = http://www.theora.org/news/#libtheora-1.1.1 | title = Theora 1.1.1 release | accessdate = 6 October 2009 | publisher = Xiph.Org基金會 | archive-date = 2010-01-18 | archive-url = https://web.archive.org/web/20100118134433/http://theora.org/news/#libtheora-1.1.1 | dead-url = no }}</ref>
| latest_preview_version = 1.2.0 Alpha 1
| latest_preview_version = 1.2.0 Alpha 1
| latest_preview_date = {{Release date and age|2010|09|24}}<ref>{{cite web| url = http://lists.xiph.org/pipermail/theora-dev/2010-September/004202.html | title = libtheora 1.2.0alpha1 release |accessdate=10 October 2010 | publisher=Xiph.Org基金會}}</ref>
| latest_preview_date = {{Release date and age|2010|09|24}}<ref>{{cite web | url = http://lists.xiph.org/pipermail/theora-dev/2010-September/004202.html | title = libtheora 1.2.0alpha1 release | accessdate = 10 October 2010 | publisher = Xiph.Org基金會 | archive-date = 2011-04-03 | archive-url = https://web.archive.org/web/20110403012129/http://lists.xiph.org/pipermail/theora-dev/2010-September/004202.html | dead-url = no }}</ref>
| frequently updated =
| frequently updated =
| programming language = [[C語言]]
| programming language = [[C語言]]
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}}
}}


'''Theora'''是一個免權利金、開放格式的[[破壞性資料壓縮|有損]][[影像壓縮]]技術，由[[Xiph.Org基金會]]開發，該基金會還開發了著名的聲音編碼技術[[Vorbis]]，以及多媒體容器檔案格式[[Ogg]]。'''libtheora'''則是Xiph.Org基金會針對Theora格式的實作。<ref name="libtheora-xiph">{{cite web | last = | first = | author=Xiph.Org基金會 | authorlink= | title = libtheora Documentation 1.1.0 | url = http://theora.org/doc/libtheora-1.1/ | format= | accessdate=25 September 2009 | date = | publisher=Xiph.Org基金會}}</ref><ref name="libtheora-ohloh">{{cite web | last = | first = | author=ohloh | authorlink= | title = libtheora | url = http://www.ohloh.net/p/libtheora | format= | accessdate=25 September 2009 | date = | publisher=ohloh}}</ref>
'''Theora'''是一個免權利金、開放格式的[[破壞性資料壓縮|有損]][[影像壓縮]]技術，由[[Xiph.Org基金會]]開發，該基金會還開發了著名的聲音編碼技術[[Vorbis]]，以及多媒體容器檔案格式[[Ogg]]。'''libtheora'''則是Xiph.Org基金會針對Theora格式的實作<ref name="libtheora-xiph">{{cite web | last= | first= | author=Xiph.Org基金會 | authorlink= | title=libtheora Documentation 1.1.0 | url=http://theora.org/doc/libtheora-1.1/ | format= | accessdate=25 September 2009 | date= | publisher=Xiph.Org基金會 | archive-date=2018-06-24 | archive-url=https://web.archive.org/web/20180624130203/https://www.theora.org/doc/libtheora-1.1/ | dead-url=no }}</ref><ref name="libtheora-ohloh">{{cite web | last= | first= | author=ohloh | authorlink= | title=libtheora | url=http://www.ohloh.net/p/libtheora | format= | accessdate=25 September 2009 | date= | publisher=ohloh | archive-date=2010-10-10 | archive-url=https://web.archive.org/web/20101010075905/http://www.ohloh.net/p/libtheora | dead-url=no }}</ref>。


Theora是由[[On2 Technologies]]公司專屬的[[VP3]]編碼器，經過開放原始碼後衍生而來，目標是達成比[[MPEG-4|MPEG-4 Part 2]]更好的編碼效率。Theora的命名來自於一個電視節目Max Headroom中的角色：Theora Jones<ref>{{cite website | publisher = Xiph.Org基金會| title = Theora FAQ
Theora是由[[On2 Technologies]]公司專屬的[[VP3]]編碼器，經過開放原始碼後衍生而來，目標是達成比[[MPEG-4|MPEG-4 Part 2]]更好的編碼效率。Theora的命名來自於一個電視節目Max Headroom中的角色：Theora Jones<ref>{{cite website| publisher = Xiph.Org基金會| title = Theora FAQ| url = http://theora.org/faq/#15| accessdate = 2009-08-06| archive-date = 2018-06-24| archive-url = https://web.archive.org/web/20180624130008/https://www.theora.org/faq/#15| dead-url = no}}</ref>。
| url = http://theora.org/faq/#15 | accessdate = 2009-08-06}}</ref>。


== 發展歷史 ==
== 發展歷史 ==
=== 開發緣起 ===
=== 開發緣起 ===
Theora的前身是由On2 Technologies所開發的專屬影像編碼格式''On2 TrueMotion VP3''，VP3.1在2000年5月推出，三個月後推出的VP3.2則成為了Theora的基礎<ref>{{cite press release
Theora的前身是由On2 Technologies所開發的專屬影像編碼格式''On2 TrueMotion VP3''，VP3.1在2000年5月推出，三個月後推出的VP3.2則成為了Theora的基礎<ref>{{cite press release
| url = http://www.on2.com/index.php?id=486&news_id=401
|url = http://www.on2.com/index.php?id=486&news_id=401
| title = On2 Introduces TrueMotion VP3.2
|title = On2 Introduces TrueMotion VP3.2
| publisher = On2 | date = 16 August 2000 | accessdate = 11 August 2009
|publisher = On2
|date = 16 August 2000
|accessdate = 11 August 2009
|deadurl = yes
⚫
}}</ref><ref>{{cite |url=http://web.archive.org/web/20071203062255/www.on2.com/index.php?id=486&news_id=401 |title=On2 Introduces TrueMotion VP3.2（archived website）|author=On2 |date=2000-08-16 |accessdate=2010-08-23}}</ref><ref>{{cite press release
| url = http://www.on2.com/index.php?id=486&news_id=407
|archiveurl = https://web.archive.org/web/20071203062255/http://www.on2.com/index.php?id=486&news_id=401
|archivedate = 2007年12月3日
⚫
| title = On2.com Launches Next Generation of Revolutionary Broadband Video Technology
⚫
}}</ref><ref>{{cite |url=http://www.on2.com/index.php?id=486&news_id=401 |title=On2 Introduces TrueMotion VP3.2（archived website） |author=On2 |date=2000-08-16 |accessdate=2010-08-23 |deadurl=yes |archiveurl=https://web.archive.org/web/20071203062255/http://www.on2.com/index.php?id=486&news_id=401 |archivedate=2007-12-03 }}</ref><ref>{{cite press release
| publisher = On2 | date = 17 May 2000 | accessdate = 11 August 2009
|url = http://www.on2.com/index.php?id=486&news_id=407
⚫
}}</ref><ref>{{cite |url=http://web.archive.org/web/20071203064537/http://www.on2.com/index.php?id=486&news_id=407 |title=On2.com Launches Next Generation of Revolutionary Broadband Video Technology（archived website）|author=On2 |date=17 May 2000 |accessdate=2010-08-23}}</ref>。2001年8月，On2 Technologies宣佈將會釋出一個VP3.2的開放原始碼版本，同年9月在網站www.vp3.com上面釋出VP 3.2的原始碼以及演算法<ref name="vp32license-archive">{{cite
⚫
|title = On2.com Launches Next Generation of Revolutionary Broadband Video Technology
⚫
| title = VP3.2 Public License 0.1 | year = 2001
|publisher = On2
| author = On2 Technologies | publisher = Archive.org
|date = 17 May 2000
⚫
| url = http://web.archive.org/web/20011026032511/http://vp3.com/license/vp32_opensource_license_9-6-01.txt | accessdate = 22 September 2009
|accessdate = 11 August 2009
|deadurl = yes
|archiveurl = https://web.archive.org/web/20071203064537/http://www.on2.com/index.php?id=486&news_id=407
|archivedate = 2007年12月3日
⚫
}}</ref><ref>{{cite |url=http://www.on2.com/index.php?id=486&news_id=407 |title=On2.com Launches Next Generation of Revolutionary Broadband Video Technology（archived website） |author=On2 |date=17 May 2000 |accessdate=2010-08-23 |deadurl=yes |archiveurl=https://web.archive.org/web/20071203064537/http://www.on2.com/index.php?id=486&news_id=407 |archivedate=2007-12-03 }}</ref>。2001年8月，On2 Technologies宣佈將會釋出一個VP3.2的開放原始碼版本，同年9月在網站www.vp3.com上面釋出VP 3.2的原始碼以及演算法<ref name="vp32license-archive">{{cite
⚫
|title = VP3.2 Public License 0.1
|year = 2001
|author = On2 Technologies
|publisher = Archive.org
|url = http://vp3.com/license/vp32_opensource_license_9-6-01.txt
|accessdate = 22 September 2009
|deadurl = yes
⚫
|archiveurl = https://web.archive.org/web/20011026032511/http://vp3.com/license/vp32_opensource_license_9-6-01.txt
|archivedate = 2001年10月26日
}}</ref><ref name="vp32license-01">{{cite
}}</ref><ref name="vp32license-01">{{cite
| title = VP3.2 Public License 0.1 | year = 2001
| title = VP3.2 Public License 0.1
| year = 2001
| author = On2 Technologies
| author = On2 Technologies
| publisher = Xiph.Org基金會| url = http://trac.xiph.org/browser/branches/vp32/vp32/VP32_license.txt | accessdate = 10 February 2008
| publisher = Xiph.Org基金會
| url = http://trac.xiph.org/browser/branches/vp32/vp32/VP32_license.txt
| accessdate = 10 February 2008
| archive-url = https://web.archive.org/web/20160404101159/https://trac.xiph.org/browser/branches/vp32/vp32/VP32_license.txt
⚫
}}</ref><ref>StreamingMedia.com（2001-09-07）[http://www.streamingmedia.com/article.asp?id=7871 On2 Offers Up VP3.2 Source Code], Retrieved on 2009-08-16</ref><ref>On2（2001-09-07）[http://www.on2.com/index.php?id=486&news_id=364 On2 Technologies Makes Video Compression Technology Available to Open-Source Community], Retrieved on 2009-08-16</ref><ref>{{cite |url=http://web.archive.org/web/20071207021659/http://www.on2.com/index.php?id=486&news_id=364 |title=On2 Technologies Makes Video Compression Technology Available to Open-Source Community（archived website）|author=On2 |date=2001-09-07 |accessdate=2010-08-23}}</ref><ref>Linux.com（2001-09-06）[http://www.linux.com/archive/feature/16482 On2 Technologies Open-Sources VP3 video compression code], Retrieved on 2009-08-16</ref>。
| archive-date = 2016-04-04
| dead-url = yes
⚫
}}</ref><ref>StreamingMedia.com（2001-09-07）[http://www.streamingmedia.com/article.asp?id=7871 On2 Offers Up VP3.2 Source Code] {{Wayback|url=http://www.streamingmedia.com/article.asp?id=7871 |date=20070814141742 }}, Retrieved on 2009-08-16</ref><ref>On2（2001-09-07）[http://www.on2.com/index.php?id=486&news_id=364 On2 Technologies Makes Video Compression Technology Available to Open-Source Community] {{Wayback|url=http://www.on2.com/index.php?id=486&news_id=364 |date=20071207021659 }}, Retrieved on 2009-08-16</ref><ref>{{cite |url=http://www.on2.com/index.php?id=486&news_id=364 |title=On2 Technologies Makes Video Compression Technology Available to Open-Source Community（archived website） |author=On2 |date=2001-09-07 |accessdate=2010-08-23 |deadurl=yes |archiveurl=https://web.archive.org/web/20071207021659/http://www.on2.com/index.php?id=486&news_id=364 |archivedate=2007-12-07 }}</ref><ref>Linux.com（2001-09-06）[http://www.linux.com/archive/feature/16482 On2 Technologies Open-Sources VP3 video compression code], Retrieved on 2009-08-16</ref>。


=== 轉變為自由軟體 ===
=== 轉變為自由軟體 ===
2002年3月，On2將VP3原始碼的許可認證更改為[[LGPL]]<ref>The Free Library（2002-03-28）[http://www.thefreelibrary.com/On2+Alters+Licensing+Terms+for+VP3%3b+Company+Responds+to+Open+Source...-a084233138 On2 Alters Licensing Terms for VP3; Company Responds to Open Source Community Demands.], Retrieved on 2009-08-16</ref>；同年6月，On2將VP3以BSD-like的許可認證方式捐贈給Xiph.Org基金會<ref>On2（2002-06-24）[http://www.on2.com/index.php?id=486&news_id=313 VP3 Combines with Vorbis to Create First Open-Source Multimedia Platform], Retrieved on 2009-08-16</ref><ref>{{cite |url=http://web.archive.org/web/20071203061350/www.on2.com/index.php?id=486&news_id=313 |title=VP3 Combines with Vorbis to Create First Open-Source Multimedia Platform（archived website）|author=On2 |date=2002-06-24 |accessdate=2010-08-23}}</ref><ref name="linux-com-ogg">Linux.com（2002-06-23）[http://www.linux.com/archive/articles/23630?tid=6 Ogg Vorbis, VP3 combining forces to create Open Source multimedia package], Retrieved on 2009-08-16</ref><ref>InternetNews.com（2002-06-24）[http://www.internetnews.com/bus-news/article.php/1370341 On2 Throws More Open-Source at MPEG-4], Retrieved on 2009-08-16</ref>，並且放棄VP3包含的智慧財產，允使任何人將VP3編碼作更動、衍生<ref name="theora-license">Xiph.org [http://svn.xiph.org/trunk/theora/LICENSE libtheora license (Subversion - Trunk)], Retrieved on 2009-08-16</ref><ref name="vp32-license">Xiph.org [http://svn.xiph.org/trunk/vp32/LICENSE VP32 codec license (Subversion - Trunk)], Retrieved on 2009-08-16</ref>。
2002年3月，On2將VP3原始碼的許可認證更改為[[LGPL]]<ref>The Free Library（2002-03-28）[http://www.thefreelibrary.com/On2+Alters+Licensing+Terms+for+VP3%3b+Company+Responds+to+Open+Source...-a084233138 On2 Alters Licensing Terms for VP3; Company Responds to Open Source Community Demands.] {{Wayback|url=http://www.thefreelibrary.com/On2+Alters+Licensing+Terms+for+VP3%3b+Company+Responds+to+Open+Source...-a084233138 |date=20101204092727 }}, Retrieved on 2009-08-16</ref>；同年6月，On2將VP3以BSD-like的許可認證方式捐贈給Xiph.Org基金會<ref>On2（2002-06-24）[http://www.on2.com/index.php?id=486&news_id=313 VP3 Combines with Vorbis to Create First Open-Source Multimedia Platform] {{Wayback|url=http://www.on2.com/index.php?id=486&news_id=313 |date=20071203061350 }}, Retrieved on 2009-08-16</ref><ref>{{cite |url=http://www.on2.com/index.php?id=486&news_id=313 |title=VP3 Combines with Vorbis to Create First Open-Source Multimedia Platform（archived website） |author=On2 |date=2002-06-24 |accessdate=2010-08-23 |deadurl=yes |archiveurl=https://web.archive.org/web/20071203061350/http://www.on2.com/index.php?id=486&news_id=313 |archivedate=2007-12-03 }}</ref><ref name="linux-com-ogg">Linux.com（2002-06-23）[http://www.linux.com/archive/articles/23630?tid=6 Ogg Vorbis, VP3 combining forces to create Open Source multimedia package], Retrieved on 2009-08-16</ref><ref>InternetNews.com（2002-06-24）[http://www.internetnews.com/bus-news/article.php/1370341 On2 Throws More Open-Source at MPEG-4] {{Wayback|url=http://www.internetnews.com/bus-news/article.php/1370341 |date=20110604093151 }}, Retrieved on 2009-08-16</ref>，並且放棄VP3包含的智慧財產，允使任何人將VP3編碼作更動、衍生<ref name="theora-license">Xiph.org [http://svn.xiph.org/trunk/theora/LICENSE libtheora license (Subversion - Trunk)] {{Wayback|url=http://svn.xiph.org/trunk/theora/LICENSE |date=20100207211310 }}, Retrieved on 2009-08-16</ref><ref name="vp32-license">Xiph.org [http://svn.xiph.org/trunk/vp32/LICENSE VP32 codec license (Subversion - Trunk)] {{Wayback|url=http://svn.xiph.org/trunk/vp32/LICENSE |date=20091003043553 }}, Retrieved on 2009-08-16</ref>。


2002年8月，On2宣佈和Xiph.Org基金會達成協議，將會以VP3編碼器為基礎，製作一個新的影音編碼格式：Theora。On2認可Theora為VP3的後繼者，在2002年10月3日，On2和Xiph.Org基金會共同完成了Theora的實作：libtheora的最初版本，2003年6月9日，完成了Alpha 2版本<ref name="libtheora-alpha2">{{cite mailing list | url = http://lists.xiph.org/pipermail/theora-dev/2003-June/000623.html | title = libtheora alpha 2 release | mailinglist = theora-dev | date = 9 June 2003 | last = Giles |first = Ralph |authorlink= |accessdate=26 September 2009}}</ref>；2004年3月20日推出了Alpha 3版本<ref name="libtheora-alpha3">{{cite mailing list | url = http://lists.xiph.org/pipermail/theora-dev/2004-March/000950.html | title = libtheora alpha 3 release | mailinglist = theora-dev | date = 19 March 2004 | last = Giles |first = Ralph |authorlink= |accessdate=26 September 2009}}</ref>。
2002年8月，On2宣佈和Xiph.Org基金會達成-{zh-hant:協議; zh-hans:协议}-，將會以VP3編碼器為基礎，製作一個新的影音編碼格式：Theora。On2認可Theora為VP3的後繼者，在2002年10月3日，On2和Xiph.Org基金會共同完成了Theora的實作：libtheora的最初版本，2003年6月9日，完成了Alpha 2版本<ref name="libtheora-alpha2">{{cite mailing list | url = http://lists.xiph.org/pipermail/theora-dev/2003-June/000623.html | title = libtheora alpha 2 release | mailinglist = theora-dev | date = 9 June 2003 | last = Giles | first = Ralph | authorlink = | accessdate = 26 September 2009 | archive-date = 2011-09-27 | archive-url = https://web.archive.org/web/20110927161649/http://lists.xiph.org/pipermail/theora-dev/2003-June/000623.html | dead-url = no }}</ref>；2004年3月20日推出了Alpha 3版本<ref name="libtheora-alpha3">{{cite mailing list | url = http://lists.xiph.org/pipermail/theora-dev/2004-March/000950.html | title = libtheora alpha 3 release | mailinglist = theora-dev | date = 19 March 2004 | last = Giles | first = Ralph | authorlink = | accessdate = 26 September 2009 | archive-date = 2011-09-27 | archive-url = https://web.archive.org/web/20110927161741/http://lists.xiph.org/pipermail/theora-dev/2004-March/000950.html | dead-url = no }}</ref>。


在VP3開放原始碼時，並沒有針對VP3的位元流格式做規範，2003年，Mike Melanson建立了一個不完整的VP3位元流描述，而後在Theora的規範中採用了部份VP3的位元流描述。<ref name="theoraspec" /><ref name="vp3-bitstream">{{cite
在VP3開放原始碼時，並沒有針對VP3的位元流格式做規範，2003年，Mike Melanson建立了一個不完整的VP3位元流描述，而後在Theora的規範中採用了部份VP3的位元流描述。<ref name="theoraspec" /><ref name="vp3-bitstream">{{cite
| title = VP3 Bitstream Format and Decoding Process | date = 8 December 2004
|title = VP3 Bitstream Format and Decoding Process
|date = 8 December 2004
| author = Mike Melanson（mike at multimedia.cx）
|author = Mike Melanson（mike at multimedia.cx）
| publisher = Multimedia.cx
|publisher = Multimedia.cx
| url = http://www.multimedia.cx/vp3-format.txt | accessdate = 27 September 2009
|url = http://www.multimedia.cx/vp3-format.txt
|accessdate = 27 September 2009
|deadurl = yes
|archiveurl = https://archive.today/20130106025121/http://www.multimedia.cx/vp3-format.txt
|archivedate = 2013年1月6日
}}</ref>
}}</ref>

Theora的繼任者為[[Daala]]<ref>{{cite news|url=http://www.tomshardware.com/news/ietf-standardizes-netvc-daala-codec,28821.html |author=Lucian Armasu |publisher=Tom's Hardware |title=IETF Begins Standardization Process For Next-Generation 'NETVC' Video Codec (Daala) |date=2015-03-25 |accessdate=2015-08-05}}</ref>。


=== Theora I規格 ===
=== Theora I規格 ===
[[File:I-15bis.ogg|thumb|320px|維基百科上使用Theora影像的範例：一台[[伊-15戰鬥機]]雙翼滑翔機正在表演特技飛行。]]
[[File:I-15bis.ogg|thumb|320px|維基百科上使用Theora影像的範例：一台[[伊-15戰鬥機]]雙翼滑翔機正在表演特技飛行。]]


Theora I位元流格式最終在2004年6月libtheora 1.0alpha3版本釋出後確立<ref name="theora-freeze"/>，之後只要用libtheora編碼的影像都能夠正確無誤的播放<ref name="theora-freeze" /><ref name="theora-news">{{cite
Theora I位元流格式最終在2004年6月libtheora 1.0alpha3版本釋出後確立<ref name="theora-freeze"/>，之後只要用libtheora編碼的影像都能夠正確無誤的播放<ref name="theora-freeze" /><ref name="theora-news">{{cite | title = Theora.org : news | date = 24 September 2009 | author = Xiph.Org基金會 | publisher = Xiph.Org基金會 | url = http://theora.org/news/ | accessdate = 25 September 2009 | archive-date = 2010-10-10 | archive-url = https://web.archive.org/web/20101010214814/http://theora.org/news/ | dead-url = yes }}</ref>，最終''Theora I規格''在2004年正式推出<ref name="theoraspec-2004">{{Cite web | last= | first= | author=Xiph.Org基金會 | authorlink= | title=Theora I Specification, Xiph.org基金會, September 17, 2004 | url=http://www.theora.org/doc/Theora_I_spec.pdf | format=PDF | accessdate=26 September 2009 | date=17 September 2004 | publisher=Archive.org | postscript=<!--None--> | deadurl=yes | archiveurl=https://web.archive.org/web/20040928224506/http://www.theora.org/doc/Theora_I_spec.pdf | archivedate=2004年9月28日 }}</ref>。
| title = Theora.org : news | date = 24 September 2009
| author = Xiph.Org基金會 | publisher = Xiph.Org基金會 | url = http://theora.org/news/ | accessdate = 25 September 2009
}}</ref>，最終''Theora I規格''在2004年正式推出<ref name="theoraspec-2004">{{Cite web | last = | first = | author=Xiph.Org基金會 | authorlink= | title = Theora I Specification, Xiph.org基金會, September 17, 2004 | url = http://web.archive.org/web/20040928224506/http://www.theora.org/doc/Theora_I_spec.pdf | format= PDF | accessdate=26 September 2009 | date = 17 September 2004 | publisher=Archive.org | postscript = <!--None-->}}</ref>。


Theora影像的實作libtheora花了數年的時間在測試版狀態，最終正式版1.0版本在2008年11月釋出<ref>{{cite mailing list | url = http://lists.xiph.org/pipermail/theora-dev/2008-November/003736.html | title = Theora 1.0 final release! | mailinglist = theora-dev | date = 3 November 2008 | last = Giles |first = Ralph |authorlink= |accessdate=4 November 2008}}</ref><ref>{{cite press release
Theora影像的實作libtheora花了數年的時間在測試版狀態，最終正式版1.0版本在2008年11月釋出<ref>{{cite mailing list | url =
| title = Theora 1.0 final release! | mailinglist = theora-dev | date = 3 November 2008 | last = Giles |first = Ralph |authorlink= |accessdate=4 November 2008}}</ref><ref>{{cite press release
| title = The Xiph.Org基金會announces the release of Theora 1.0
| title = The Xiph.Org基金會announces the release of Theora 1.0
| publisher = Xiph.Org基金會 | date = 3 November 2008
| publisher = Xiph.Org基金會
| date = 3 November 2008
| url = http://www.xiph.org/press/2008/theora-release-1.0/ | accessdate = 6 August 2009
| url = http://www.xiph.org/press/2008/theora-release-1.0/
| accessdate = 6 August 2009
| archive-date = 2009-02-17
⚫
}}</ref>，隨後針對libtheora 1.0版本的作改進的1.1版（代號''"Thusnelda"''）也在在2009年11月釋出<ref>{{cite mailing list | url = http://lists.xiph.org/pipermail/theora-dev/2009-September/003985.html | title = libtheora 1.1（Thusnelda）stable release | mailinglist = theora-dev | date = 24 September 2009 | last = Giles |first = Ralph | authorlink= |accessdate=24 September 2009}}</ref>，1.1版本帶來了許多新特性和改進，像是位元率控制以及[[二次編碼]]。下個版本的 libtheora 也正在開發中，代號為''Ptalarbvorm''<ref name="ptalarbvorm">{{Cite web | last = | first = | author=Monty | authorlink= | title = Theora: Ptalarbvorm project update 20100518 | url = http://people.xiph.org/~xiphmont/demo/theora/demo9.html | accessdate=1 July 2010 | date = 18 May 2010 | publisher= | postscript = <!--None--> }}</ref>，不過目前Theora的程式碼已經近3年沒有重大更新，開發呈現停滯狀態<ref>https://github.com/aptana/studio3/pull/211</ref>。
| archive-url = https://web.archive.org/web/20090217223620/http://xiph.org/press/2008/theora-release-1.0/
| dead-url = no
⚫
}}</ref>，隨後針對libtheora 1.0版本的作改進的1.1版（代號''"Thusnelda"''）也在在2009年11月釋出<ref>{{cite mailing list | url = http://lists.xiph.org/pipermail/theora-dev/2009-September/003985.html | title = libtheora 1.1（Thusnelda）stable release | mailinglist = theora-dev | date = 24 September 2009 | last = Giles | first = Ralph | authorlink = | accessdate = 24 September 2009 | archive-date = 2010-05-13 | archive-url = https://web.archive.org/web/20100513194452/http://lists.xiph.org/pipermail/theora-dev/2009-September/003985.html | dead-url = no }}</ref>，1.1版本帶來了許多新特性和改進，像是位元率控制以及[[二次{{}}編碼]]。下個版本的 libtheora 也正在開發中，代號為''Ptalarbvorm''<ref name="ptalarbvorm">{{Cite web | last = | first = | author = Monty | authorlink = | title = Theora: Ptalarbvorm project update 20100518 | url = http://people.xiph.org/~xiphmont/demo/theora/demo9.html | accessdate = 1 July 2010 | date = 18 May 2010 | publisher = | postscript = <!--None--> | archive-url = https://web.archive.org/web/20100521172638/http://people.xiph.org/~xiphmont/demo/theora/demo9.html | archive-date = 2010-05-21 | dead-url = yes }}</ref>，不過目前Theora的程式碼已經近3年沒有重大更新，開發呈現停滯狀態<ref>{{Cite web |url=https://github.com/aptana/studio3/pull/211 |title=存档副本 |accessdate=2014-06-30 |archive-date=2019-02-18 |archive-url=https://web.archive.org/web/20190218044120/https://github.com/aptana/studio3/pull/211 |dead-url=no }}</ref>。


隨著Theora逐漸成熟，使用Theora編碼的軟體也逐漸增加，例如維基百科就以Theora作為影片的編碼格式。Theora也曾經被確認為HTML5影像編碼的標準格式，但是在一些爭論之後被撤銷<ref>{{cite web
隨著Theora逐漸成熟，使用Theora編碼的軟體也逐漸增加，例如維基百科就以Theora作為影片的編碼格式。Theora也曾經被確認為HTML5影像編碼的標準格式，但是在一些爭論之後被撤銷<ref>{{cite web | last = McLean | first = Prince | title = Ogg Theora, H.264 and the HTML 5 Browser Squabble | publisher = RoughlyDrafted Magazine | date = 6 July 2009 | url = http://www.roughlydrafted.com/2009/07/06/ogg-theora-h-264-and-the-html-5-browser-squabble/ | accessdate =2010-02-14| archive-url = https://web.archive.org/web/20101203202243/http://www.roughlydrafted.com/2009/07/06/ogg-theora-h-264-and-the-html-5-browser-squabble/ | archive-date = 2010-12-03 | dead-url = yes }}</ref>。
| last = McLean | first = Prince | title = Ogg Theora, H.264 and the HTML 5 Browser Squabble
| publisher = RoughlyDrafted Magazine | date = 6 July 2009
| url = http://www.roughlydrafted.com/2009/07/06/ogg-theora-h-264-and-the-html-5-browser-squabble/ | accessdate = 14 Februari 2010
}}</ref>。


== 技術細節 ==
== 技術細節 ==
Theora是一個[[可變位元速率|變動位元率]]、以[[DCT]]為基礎的影像壓縮格式。和多數的影像編碼格式一樣，Theora使用了[[色度抽樣]]、block based motion compensation和8×8 DCT block，也支援[[intra-coded frames（I-frames）|視訊壓縮圖像類型]]和[[forward predictive frames（P-frames）|視訊壓縮圖像類型]]，但是不支援使用在[[H.264]]和[[VC-1]]的[[視訊壓縮圖像類型|bi-predictive frames（B-frame）]]，Theora也不支援[[隔行掃描]]、可变帧率，或8位以上原色色深。<ref name="theoraspec">{{cite website
Theora是一個[[可變位元速率|變動位元率]]、以[[DCT]]為基礎的影像壓縮格式。和多數的影像編碼格式一樣，Theora使用了[[色度抽樣]]、block based motion compensation和8×8 DCT block，也支援[[intra-coded frames（I-frames）|視訊壓縮圖像類型]]和[[forward predictive frames（P-frames）|視訊壓縮圖像類型]]，但是不支援使用在[[H.264]]和[[VC-1]]的[[視訊壓縮圖像類型|bi-predictive frames（B-frame）]]，Theora也不支援[[隔行掃描]]、可变帧率，或8位以上原色色深。<ref name="theoraspec">{{cite website
| title = Theora Specification | year = 2007
| title = Theora Specification
| year = 2007
| publisher = Xiph.Org基金會| url = http://theora.org/doc/Theora.pdf
| publisher = Xiph.Org基金會
| url = http://theora.org/doc/Theora.pdf
| accessdate = 2009-09-07
| archive-date = 2012-02-20
| archive-url = https://www.webcitation.org/65arXwqO2?url=http://theora.org/doc/Theora.pdf
| dead-url = no
}}</ref>。
}}</ref>。


Theora的影像流可以儲存在任何的容器檔案格式中，最常用的是和聲音編碼[[Vorbis]]一起儲存在[[Ogg]]檔案格式中，這種方式可以提供完全開放、免權利金的多媒體檔案。此外Theora影像也可以儲存在[[Matroska]]檔案中<ref>{{cite web
Theora的影像流可以儲存在任何的容器檔案格式中，最常用的是和聲音編碼[[Vorbis]]一起儲存在[[Ogg]]檔案格式中，這種方式可以提供完全開放、免權利金的多媒體檔案。此外Theora影像也可以儲存在[[Matroska]]檔案中<ref>{{cite web | publisher = Matroska | title = Matroska Codec Specs | url = http://www.matroska.org/technical/specs/codecid/index.html | accessdate = 2009-08-06 | archive-date = 2009-08-31 | archive-url = https://web.archive.org/web/20090831164352/http://www.matroska.org/technical/specs/codecid/index.html | dead-url = no }}</ref>。
| publisher = Matroska | title = Matroska Codec Specs
| url = http://www.matroska.org/technical/specs/codecid/index.html | accessdate = 2009-08-06
}}</ref>。


== 影像表現 ==
== 影像表現 ==


=== 編碼表現 ===
=== 編碼表現 ===
早期的VP3<ref>{{cite web | publisher = Doom9 | title = MPEG-4 Codec shoot-out 2002 - 1st installment | year = 2002 | url = http://www.doom9.org/codec-comparisons.htm | accessdate = 19 December 2007 | deadurl = yes | archiveurl = https://web.archive.org/web/20080223010804/http://www.doom9.org/codec-comparisons.htm | archivedate = 2008年2月23日 }}</ref>和Theora<ref>{{cite | publisher = Doom9 | title = Codec shoot-out 2005 - Qualification | year = 2005 | url = http://www.doom9.org/codecs-quali-105-3.htm | accessdate = 19 December 2007 | deadurl = yes | archiveurl = https://web.archive.org/web/20071231133347/http://www.doom9.org/codecs-quali-105-3.htm | archivedate = 2007年12月31日 }}</ref>
早期的VP3<ref>{{cite web
<ref>{{cite web | publisher = OSNews | first = Eugenia | last = Loli-Queru | title = Theora vs. h.264 | date = 12 December 2007 | url = http://www.osnews.com/story/19019/Theora-vs-h.264/ | accessdate = 1 April 2008 | archive-date = 2009-02-17 | archive-url = https://web.archive.org/web/20090217222748/http://osnews.com/story/19019/Theora-vs-h.264 | dead-url = no }}</ref>
| publisher = Doom9 | title = MPEG-4 Codec shoot-out 2002 - 1st installment
<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/ | accessdate = 22 April 2008 | deadurl = yes | archiveurl = https://archive.today/20120707194336/http://etill.net/projects/dirac_theora_evaluation/ | archivedate = 2012年7月7日 }}</ref>編碼器在編碼結果上明顯不如同時期的其他編碼器。Google公司的員工Chris DiBona也在2009年宣稱Theora的編碼品質不佳<ref>{{cite mailing list | last = DiBona | first = Chris | title = H.264-in-<video> vs plugin APIs | mailinglist = whatwg | date = 13 June 2009 | url = http://lists.whatwg.org/htdig.cgi/whatwg-whatwg.org/2009-June/020380.html | accessdate = 10 August 2009 | archive-date = 2011-04-27 | archive-url = https://web.archive.org/web/20110427134540/http://lists.whatwg.org/htdig.cgi/whatwg-whatwg.org/2009-June/020380.html | dead-url = no }}</ref>，為了回應這個論點，Xiph基金會的開發者用Theora 1.1版本的編碼器和[[YouTube]]上的[[H.264]]以及[[H.263|H.263+]]編碼器做比較，結果發現Theora的編碼畫質可以比擬H.264，且更勝於H.263+<ref>{{cite web | last = Maxwell | first = Greg | title = YouTube / Ogg/Theora comparison | publisher = Xiph.Org基金會 | date = 13 June 2009 | url = http://people.xiph.org/~greg/video/ytcompare/comparison.html | accessdate = 10 August 2009 | archive-url = https://web.archive.org/web/20090709062345/http://people.xiph.org//~greg//video//ytcompare//comparison.html | archive-date = 2009-07-09 | dead-url = yes }}</ref><ref>{{cite web | last = Maik | first = Merten | title = Another online-video comparison | publisher = Xiph.Org基金會 | date = 15 June 2009 | url = http://people.xiph.org/~maikmerten/youtube/ | accessdate = 10 August 2009 | archive-url = https://web.archive.org/web/20090709062338/http://people.xiph.org//~maikmerten//youtube// | archive-date = 2009-07-09 | dead-url = yes }}</ref>。
| year = 2002 | url = http://www.doom9.org/codec-comparisons.htm | accessdate = 19 December 2007
}}</ref>和Theora<ref>{{cite
| publisher = Doom9 | title = Codec shoot-out 2005 - Qualification
| year = 2005 | url = http://www.doom9.org/codecs-quali-105-3.htm | accessdate = 19 December 2007 }}</ref>
<ref>{{cite web
| publisher = OSNews | first = Eugenia | last = Loli-Queru | title = Theora vs. h.264
| date=12 December 2007 | url = http://www.osnews.com/story/19019/Theora-vs-h.264/ | accessdate = 1 April 2008 }}</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/ | accessdate = 22 April 2008 }}</ref>編碼器在編碼結果上明顯不如同時期的其他編碼器。Google公司的員工Chris DiBona也在2009年宣稱Theora的編碼品質不佳<ref>{{cite mailing list
| last = DiBona |first = Chris
| title = H.264-in-<video> vs plugin APIs | mailinglist = whatwg | date = 13 June 2009
| url = http://lists.whatwg.org/htdig.cgi/whatwg-whatwg.org/2009-June/020380.html | accessdate = 10 August 2009
}}</ref>，為了回應這個論點，Xiph基金會的開發者用Theora 1.1版本的編碼器和[[YouTube]]上的[[H.264]]以及[[H.263|H.263+]]編碼器做比較，結果發現Theora的編碼畫質可以比擬H.264，且更勝於H.263+<ref>{{cite web
| last = Maxwell | first = Greg | title = YouTube / Ogg/Theora comparison
| publisher = Xiph.Org基金會 | date = 13 June 2009
| url = http://people.xiph.org/~greg/video/ytcompare/comparison.html | accessdate = 10 August 2009
}}</ref><ref>{{cite web
| last = Maik | first = Merten | title = Another online-video comparison
| publisher = Xiph.Org基金會 | date = 15 June 2009
| url = http://people.xiph.org/~maikmerten/youtube/ | accessdate = 10 August 2009
}}</ref>。


=== 播放表現 ===
=== 播放表現 ===
針對Theora的硬體解碼器，目前有開放原始碼的[[VHDL]]程式正在開發中<ref>{{cite web | url = http://svn.xiph.org/trunk/theora-fpga/ | publisher = Xiph.Org基金會 | title = Xiph Subversion repository: trunk/theora-fpga | accessdate =2009-08-10 }}</ref>。而2006年開始也有針對[[Nios II]]以及[[LEON]]處理器做為解碼器的開發計畫<ref>{{cite web | url = http://wiki.xiph.org/Theora_Hardware | title = XiphWiki: Theora Hardware | accessdate = 10 August 2009 | publisher = Xiph.Org基金會}}</ref>，不過目前並沒有任何可以針對Theora影像做硬體解碼的產品出現在市面上。
針對Theora的硬體解碼器，目前有開放原始碼的[[VHDL]]程式正在開發中<ref>{{cite web | url = http://svn.xiph.org/trunk/theora-fpga/ | publisher = Xiph.Org基金會 | title = Xiph Subversion repository: trunk/theora-fpga | accessdate = 2009-08-10 | archive-date = 2009-07-31 | archive-url = https://web.archive.org/web/20090731190443/http://svn.xiph.org/trunk/theora-fpga/ | dead-url = no }}</ref>。而2006年開始也有針對[[Nios II]]以及[[LEON]]處理器做為解碼器的開發計畫<ref>{{cite web | url = http://wiki.xiph.org/Theora_Hardware | title = XiphWiki: Theora Hardware | accessdate = 10 August 2009 | publisher = Xiph.Org基金會 | archive-date = 2009-09-17 | archive-url = https://web.archive.org/web/20090917120819/http://wiki.xiph.org/Theora_Hardware | dead-url = no }}</ref>，不過目前並沒有任何可以針對Theora影像做硬體解碼的產品出現在市面上。


== 播放 ==
== 播放 ==


=== 瀏覽器原生支援 ===
=== 瀏覽器原生支援 ===
* [[Firefox|Mozilla Firefox]]在3.5之後的版本<ref name="gecko191">{{cite | title = Firefox3.5/Features | date = 18 March 2009 | author = MozillaWiki | publisher = MozillaWiki | url = https://wiki.mozilla.org/Firefox3.5/Features | accessdate = 11 October 2009}}</ref><ref name="firefox35">{{cite | title = Mozilla Firefox 3.5 Release Notes | date = 30 June 2009 | author = Mozilla Corporation | publisher = Mozilla Corporation | url = http://www.mozilla.com/en-US/firefox/3.5/releasenotes/ | accessdate = 11 October 2009}}</ref>包括了[[Firefox Mobile]]（Fennec）<ref name="firefox_mobile">{{cite | title = Firefox Mobile Features | date = 9 February 2010 | author = Mozilla Corporation | publisher = Mozilla Corporation | url = http://www.mozilla.com/en-US/mobile/features/#cutting-edge | accessdate = 9 February 2010}}</ref>。
* [[Firefox|Mozilla Firefox]]在3.5之後的版本<ref name="gecko191">{{cite | title = Firefox3.5/Features | date = 18 March 2009 | author = MozillaWiki | publisher = MozillaWiki | url = https://wiki.mozilla.org/Firefox3.5/Features | accessdate = 11 October 2009 | archive-date = 2010-07-06 | archive-url = https://web.archive.org/web/20100706104327/https://wiki.mozilla.org/Firefox3.5/Features | dead-url = no }}</ref><ref name="firefox35">{{cite | title = Mozilla Firefox 3.5 Release Notes | date = 30 June 2009 | author = Mozilla Corporation | publisher = Mozilla Corporation | url = http://www.mozilla.com/en-US/firefox/3.5/releasenotes/ | accessdate = 11 October 2009 | archive-date = 2010-11-30 | archive-url = https://web.archive.org/web/20101130202934/http://www.mozilla.com/en-US/firefox/3.5/releasenotes/ | dead-url = yes }}</ref>包括了[[Firefox Mobile]]（Fennec）<ref name="firefox_mobile">{{cite | title = Firefox Mobile Features | date = 9 February 2010 | author = Mozilla Corporation | publisher = Mozilla Corporation | url = http://www.mozilla.com/en-US/mobile/features/#cutting-edge | accessdate = 9 February 2010 | archive-date = 2010-12-01 | archive-url = https://web.archive.org/web/20101201024634/http://www.mozilla.com/en-US/mobile/features/#cutting-edge | dead-url = no }}</ref>。


* [[Google Chrome]]在3.0.182.2之後的版本<ref name="chrome3">{{cite | title = Google Chrome to support HTML 5 video | date = 28 May 2009 | author = | publisher = SoftSailor | url = http://www.softsailor.com/news/3787-3787.html | accessdate = 11 October 2009}}</ref><ref name="chrome3-video-cnet">{{cite | title = Google Chrome gets HTML video support | date = 28 May 2009 | author = Stephen Shankland | publisher = cnet news | url = http://news.cnet.com/8301-17939_109-10250958-2.html | accessdate = 11 October 2009}}</ref> including [[Chromium]] as of 14 July 2009.<ref name="chromium">{{cite | title = Issue 16657: Ensure FFmpeg binaries end up in snapshots on all platforms | date = 14 July 2009 | author = | publisher = google chromium issues list | url = http://code.google.com/p/chromium/issues/detail?id=16657 | accessdate = 6 Februari 2010}}</ref>。
* [[Google Chrome]]在3.0.182.2之後的版本<ref name="chrome3">{{cite | title = Google Chrome to support HTML 5 video | date = 28 May 2009 | author = | publisher = SoftSailor | url = http://www.softsailor.com/news/3787-3787.html | accessdate = 11 October 2009 | deadurl = yes | archiveurl = https://web.archive.org/web/20091003194653/http://www.softsailor.com/news/3787-3787.html | archivedate = 2009年10月3日 }}</ref><ref name="chrome3-video-cnet">{{cite | title = Google Chrome gets HTML video support | date = 28 May 2009 | author = Stephen Shankland | publisher = cnet news | url = http://news.cnet.com/8301-17939_109-10250958-2.html | accessdate = 11 October 2009 | archive-date = 2011-07-19 | archive-url = https://web.archive.org/web/20110719142947/http://news.cnet.com/8301-17939_109-10250958-2.html | dead-url = no }}</ref> ，自2009年7月起也包括[[Chromium]]<ref name="chromium">{{cite | title = Issue 16657: Ensure FFmpeg binaries end up in snapshots on all platforms | date = 14 July 2009 | author = | publisher = google chromium issues list | url = http://code.google.com/p/chromium/issues/detail?id=16657 | accessdate =2010-02-06| archive-date = 2012-11-04 | archive-url = https://web.archive.org/web/20121104222015/http://code.google.com/p/chromium/issues/detail?id=16657 | dead-url = no }}</ref>。


* [[SeaMonkey]]在2.0之後的版本<ref name="seamonkey2">{{cite | title = What's New in SeaMonkey 2.0 Beta 2 | date = 16 September 2009 | author = Robert Kaiser | publisher = seamonkey-project.org | url = http://www.seamonkey-project.org/releases/seamonkey2.0b2/changes | accessdate = 11 October 2009}}</ref>。
* [[SeaMonkey]]在2.0之後的版本<ref name="seamonkey2">{{cite | title = What's New in SeaMonkey 2.0 Beta 2 | date = 16 September 2009 | author = Robert Kaiser | publisher = seamonkey-project.org | url = http://www.seamonkey-project.org/releases/seamonkey2.0b2/changes | accessdate = 11 October 2009 | archive-date = 2010-06-26 | archive-url = https://web.archive.org/web/20100626224538/http://www.seamonkey-project.org/releases/seamonkey2.0b2/changes | dead-url = no }}</ref>。


* [[Konqueror]]在4.4.2之後的版本<ref name="konqueror">{{cite |title=Bugreport: Wish for audio/video element support in Konqueror |date=13 May 2007 |url=https://bugs.kde.org/show_bug.cgi?id=145380 |accessdate=2 December 2009}}</ref><ref name="konqueror44">{{cite |title=Plans for Konqueror 4.4 |date=26 November 2009 |url=http://forum.kde.org/viewtopic.php?f=18&t=83851 |accessdate=2 December 2009}}</ref>。
* [[Konqueror]]在4.4.2之後的版本<ref name="konqueror">{{cite |title=Bugreport: Wish for audio/video element support in Konqueror |date=13 May 2007 |url=https://bugs.kde.org/show_bug.cgi?id=145380 |accessdate=2 December 2009 |deadurl=yes |archiveurl=https://archive.today/20121228020255/https://bugs.kde.org/show_bug.cgi?id=145380 |archivedate=2012年12月28日 }}</ref><ref name="konqueror44">{{cite |title=Plans for Konqueror 4.4 |date=26 November 2009 |url=http://forum.kde.org/viewtopic.php?f=18&t=83851 |accessdate=2 December 2009 |archive-date=2011-07-17 |archive-url=https://web.archive.org/web/20110717175111/http://forum.kde.org/viewtopic.php?f=18&t=83851 |dead-url=no }}</ref>。


* [[Opera]]在10.50之後的版本<ref>{{cite web |url=http://my.opera.com/core/blog/2009/12/31/re-introducing-video |title=(re-)Introducing <video> - Official blog for Core developers at Opera |author=Philip Jägenstedt |publisher=Opera |date=2009-12-31 |accessdate=2010-01-02|archiveurl=http://web.archive.org/web/20100104205648/http://my.opera.com/core/blog/2009/12/31/re-introducing-video|archivedate=2010-01-04}}</ref><ref>{{cite web |url=http://my.opera.com/desktopteam/blog/happy-new-year |title=Happy New Year! - Official blog for Core developers at Opera |author=Arjan van Leeuwen |publisher=Opera |date=2009-12-31 |accessdate=2010-01-02|archiveurl=http://web.archive.org/web/20100104201911/http://my.opera.com/desktopteam/blog/happy-new-year|archivedate=2010-01-04}}</ref>，在Opera 9.5的實驗版本中也有支援<ref name="opera">{{cite | title = Experimental Opera-video build with native Ogg Theora support | date = 25 April 2007 | author = | publisher = Opera | url = http://my.opera.com/ResearchWizard/blog/experimental-opera-video-build-with-native-ogg-theora-support | accessdate = 11 October 2009}}</ref><ref name="opera-dev">{{cite | title = A call for video on the web - Opera <video> release on Labs | date = 7 November 2007 | author = | publisher = Opera | url = http://dev.opera.com/articles/view/a-call-for-video-on-the-web-opera-vid/ | accessdate = 11 October 2009}}</ref>。
* [[Opera]]在10.50之後的版本<ref>{{cite web |url=http://my.opera.com/core/blog/2009/12/31/re-introducing-video |title=(re-)Introducing <video> - Official blog for Core developers at Opera |author=Philip Jägenstedt |publisher=Opera |date=2009-12-31 |accessdate=2010-01-02 |archiveurl=https://web.archive.org/web/20100104205648/http://my.opera.com/core/blog/2009/12/31/re-introducing-video |archivedate=2010-01-04 |deadurl=yes }}</ref><ref>{{cite web |url=http://my.opera.com/desktopteam/blog/happy-new-year |title=Happy New Year! - Official blog for Core developers at Opera |author=Arjan van Leeuwen |publisher=Opera |date=2009-12-31 |accessdate=2010-01-02 |archiveurl=https://web.archive.org/web/20100104201911/http://my.opera.com/desktopteam/blog/happy-new-year |archivedate=2010-01-04 |deadurl=yes }}</ref>，在Opera 9.5的實驗版本中也有支援<ref name="opera">{{cite | title = Experimental Opera-video build with native Ogg Theora support | date = 25 April 2007 | author = | publisher = Opera | url = http://my.opera.com/ResearchWizard/blog/experimental-opera-video-build-with-native-ogg-theora-support | accessdate = 11 October 2009 | archive-date = 2007-12-02 | archive-url = https://web.archive.org/web/20071202032052/http://my.opera.com/ResearchWizard/blog/experimental-opera-video-build-with-native-ogg-theora-support | dead-url = yes }}</ref><ref name="opera-dev">{{cite | title = A call for video on the web - Opera <video> release on Labs | date = 7 November 2007 | author = | publisher = Opera | url = http://dev.opera.com/articles/view/a-call-for-video-on-the-web-opera-vid/ | accessdate = 11 October 2009 | archive-date = 2010-10-22 | archive-url = https://web.archive.org/web/20101022140811/http://dev.opera.com/articles/view/a-call-for-video-on-the-web-opera-vid/ | dead-url = no }}</ref>。


=== 瀏覽器外掛程式（Plug-in）===
=== 瀏覽器外掛程式（Plug-in）===
可以透過下列的[[外掛程式]]讓瀏覽器播放Theora影像
可以透過下列的[[外掛程式]]讓瀏覽器播放Theora影像


* [[Annodex]]的外掛程式（透過[http://wiki.xiph.org/index.php/OggPlay OggPlay]）
* [[Annodex]]的外掛程式（透過[http://wiki.xiph.org/index.php/OggPlay OggPlay]{{Wayback|url=http://wiki.xiph.org/index.php/OggPlay |date=20090228201554 }}）
* [[Cortado (software)|Cortado]]，一個以[[Java|Java語言]]開發的播放器應用程式（applet）
* [[Cortado (software)|Cortado]]，一個以[[Java|Java語言]]開發的播放器應用程式（applet）
* [[VLC media player|VLC媒體播放器]]針對IE以及Firefox的瀏覽器外掛程式
* [[VLC media player|VLC媒體播放器]]針對IE以及Firefox的瀏覽器外掛程式
第167行： 第178行：
=== 支援的應用程式 ===
=== 支援的應用程式 ===


* [[FFmpeg]]（有自己的實做）
* [[FFmpeg]]（有自己的实现）
* [[Helix project|Helix Player]]
* [[Helix project|Helix Player]]
* [[Miro Media Player]]（舊名Democracy Player）
* [[Miro Media Player]]（舊名Democracy Player）

2023年9月16日 (六) 08:31的最新版本

Theora
扩展名
.ogv, .ogg
互联网媒体类型
video/ogg
开发者Xiph.Org基金會
首次发布2004年6月1日 (2004-06-01)[1]
格式类型影像編碼
使用容器Ogg、Matroska
扩展自VP3
标准Theora規格
免费格式？是[2]
libtheora
開發者Xiph.Org基金會
首次发布2008年11月3日 (2008-11-03) (1.0)
当前版本1.1.1（2009年10月1日，​15年前​（2009-10-01）[3]）
预览版本1.2.0 Alpha 1（2010年9月24日，​14年前​（2010-09-24）[4]）
编程语言C語言
操作系统Unix-like（包含GNU/Linux、Mac OS X），Windows
类型影像編碼
许可协议3-clause BSD
网站theora.org

Theora是一個免權利金、開放格式的有損影像壓縮技術，由Xiph.Org基金會開發，該基金會還開發了著名的聲音編碼技術Vorbis，以及多媒體容器檔案格式Ogg。libtheora則是Xiph.Org基金會針對Theora格式的實作[5][6]。

Theora是由On2 Technologies公司專屬的VP3編碼器，經過開放原始碼後衍生而來，目標是達成比MPEG-4 Part 2更好的編碼效率。Theora的命名來自於一個電視節目Max Headroom中的角色：Theora Jones[7]。

發展歷史

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開發緣起

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Theora的前身是由On2 Technologies所開發的專屬影像編碼格式On2 TrueMotion VP3，VP3.1在2000年5月推出，三個月後推出的VP3.2則成為了Theora的基礎[8][9][10][11]。2001年8月，On2 Technologies宣佈將會釋出一個VP3.2的開放原始碼版本，同年9月在網站www.vp3.com上面釋出VP 3.2的原始碼以及演算法[12][13][14][15][16][17]。

轉變為自由軟體

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2002年3月，On2將VP3原始碼的許可認證更改為LGPL[18]；同年6月，On2將VP3以BSD-like的許可認證方式捐贈給Xiph.Org基金會[19][20][21][22]，並且放棄VP3包含的智慧財產，允使任何人將VP3編碼作更動、衍生[23][24]。

2002年8月，On2宣佈和Xiph.Org基金會達成协议，將會以VP3編碼器為基礎，製作一個新的影音編碼格式：Theora。On2認可Theora為VP3的後繼者，在2002年10月3日，On2和Xiph.Org基金會共同完成了Theora的實作：libtheora的最初版本，2003年6月9日，完成了Alpha 2版本[25]；2004年3月20日推出了Alpha 3版本[26]。

在VP3開放原始碼時，並沒有針對VP3的位元流格式做規範，2003年，Mike Melanson建立了一個不完整的VP3位元流描述，而後在Theora的規範中採用了部份VP3的位元流描述。[27][28]

Theora的繼任者為Daala[29]。

Theora I規格

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維基百科上使用Theora影像的範例：一台伊-15戰鬥機雙翼滑翔機正在表演特技飛行。

Theora I位元流格式最終在2004年6月libtheora 1.0alpha3版本釋出後確立[1]，之後只要用libtheora編碼的影像都能夠正確無誤的播放[1][30]，最終Theora I規格在2004年正式推出[31]。

Theora影像的實作libtheora花了數年的時間在測試版狀態，最終正式版1.0版本在2008年11月釋出[32][33]，隨後針對libtheora 1.0版本的作改進的1.1版（代號"Thusnelda"）也在在2009年11月釋出[34]，1.1版本帶來了許多新特性和改進，像是位元率控制以及[[二次{{}}編碼]]。下個版本的 libtheora 也正在開發中，代號為Ptalarbvorm[35]，不過目前Theora的程式碼已經近3年沒有重大更新，開發呈現停滯狀態[36]。

隨著Theora逐漸成熟，使用Theora編碼的軟體也逐漸增加，例如維基百科就以Theora作為影片的編碼格式。Theora也曾經被確認為HTML5影像編碼的標準格式，但是在一些爭論之後被撤銷[37]。

技術細節

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Theora是一個變動位元率、以DCT為基礎的影像壓縮格式。和多數的影像編碼格式一樣，Theora使用了色度抽樣、block based motion compensation和8×8 DCT block，也支援視訊壓縮圖像類型和視訊壓縮圖像類型，但是不支援使用在H.264和VC-1的bi-predictive frames（B-frame），Theora也不支援隔行掃描、可变帧率，或8位以上原色色深。[27]。

Theora的影像流可以儲存在任何的容器檔案格式中，最常用的是和聲音編碼Vorbis一起儲存在Ogg檔案格式中，這種方式可以提供完全開放、免權利金的多媒體檔案。此外Theora影像也可以儲存在Matroska檔案中[38]。

影像表現

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編碼表現

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早期的VP3[39]和Theora[40] [41] [42]編碼器在編碼結果上明顯不如同時期的其他編碼器。Google公司的員工Chris DiBona也在2009年宣稱Theora的編碼品質不佳[43]，為了回應這個論點，Xiph基金會的開發者用Theora 1.1版本的編碼器和YouTube上的H.264以及H.263+編碼器做比較，結果發現Theora的編碼畫質可以比擬H.264，且更勝於H.263+[44][45]。

播放表現

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針對Theora的硬體解碼器，目前有開放原始碼的VHDL程式正在開發中[46]。而2006年開始也有針對Nios II以及LEON處理器做為解碼器的開發計畫[47]，不過目前並沒有任何可以針對Theora影像做硬體解碼的產品出現在市面上。

播放

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瀏覽器原生支援

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瀏覽器外掛程式（Plug-in）

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可以透過下列的外掛程式讓瀏覽器播放Theora影像

支援的應用程式

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參見

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参考资料

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  1. ^ 1.0 1.1 1.2 Giles, Ralph. Theora I bitstream freeze. theora-dev (邮件列表). 1 June 2004 [25 September 2009]. （原始内容存档于2011-09-27）. 
  2. ^ PlayOgg! - FSF - Free Software Foundation. 2010-03-17 [2013-10-01]. （原始内容存档于2017-06-18）. 
  3. ^ Theora 1.1.1 release. Xiph.Org基金會. [6 October 2009]. （原始内容存档于2010-01-18）. 
  4. ^ libtheora 1.2.0alpha1 release. Xiph.Org基金會. [10 October 2010]. （原始内容存档于2011-04-03）. 
  5. ^ Xiph.Org基金會. libtheora Documentation 1.1.0. Xiph.Org基金會. [25 September 2009]. （原始内容存档于2018-06-24）. 
  6. ^ ohloh. libtheora. ohloh. [25 September 2009]. （原始内容存档于2010-10-10）. 
  7. ^ Theora FAQ. Xiph.Org基金會. [2009-08-06]. （原始内容存档于2018-06-24）. 
  8. ^ On2 Introduces TrueMotion VP3.2 (新闻稿). On2. 16 August 2000 [11 August 2009]. （原始内容存档于2007年12月3日）. 
  9. ^ On2, On2 Introduces TrueMotion VP3.2（archived website）, 2000-08-16 [2010-08-23], （原始内容存档于2007-12-03） 
  10. ^ On2.com Launches Next Generation of Revolutionary Broadband Video Technology (新闻稿). On2. 17 May 2000 [11 August 2009]. （原始内容存档于2007年12月3日）. 
  11. ^ On2, On2.com Launches Next Generation of Revolutionary Broadband Video Technology（archived website）, 17 May 2000 [2010-08-23], （原始内容存档于2007-12-03） 
  12. ^ On2 Technologies, VP3.2 Public License 0.1, Archive.org, 2001 [22 September 2009], （原始内容存档于2001年10月26日） 
  13. ^ On2 Technologies, VP3.2 Public License 0.1, Xiph.Org基金會, 2001 [10 February 2008], （原始内容存档于2016-04-04） 
  14. ^ StreamingMedia.com（2001-09-07）On2 Offers Up VP3.2 Source Code （页面存档备份，存于互联网档案馆）, Retrieved on 2009-08-16
  15. ^ On2（2001-09-07）On2 Technologies Makes Video Compression Technology Available to Open-Source Community （页面存档备份，存于互联网档案馆）, Retrieved on 2009-08-16
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  17. ^ Linux.com（2001-09-06）On2 Technologies Open-Sources VP3 video compression code, Retrieved on 2009-08-16
  18. ^ The Free Library（2002-03-28）On2 Alters Licensing Terms for VP3; Company Responds to Open Source Community Demands. （页面存档备份，存于互联网档案馆）, Retrieved on 2009-08-16
  19. ^ On2（2002-06-24）VP3 Combines with Vorbis to Create First Open-Source Multimedia Platform （页面存档备份，存于互联网档案馆）, Retrieved on 2009-08-16
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  21. ^ Linux.com（2002-06-23）Ogg Vorbis, VP3 combining forces to create Open Source multimedia package, Retrieved on 2009-08-16
  22. ^ InternetNews.com（2002-06-24）On2 Throws More Open-Source at MPEG-4 （页面存档备份，存于互联网档案馆）, Retrieved on 2009-08-16
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  24. ^ Xiph.org VP32 codec license (Subversion - Trunk) （页面存档备份，存于互联网档案馆）, Retrieved on 2009-08-16
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  27. ^ 27.0 27.1 Theora Specification (PDF). Xiph.Org基金會. 2007 [2009-09-07]. （原始内容存档 (PDF)于2012-02-20）. 
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  36. ^ 存档副本. [2014-06-30]. （原始内容存档于2019-02-18）. 
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  45. ^ Maik, Merten. Another online-video comparison. Xiph.Org基金會. 15 June 2009 [10 August 2009]. （原始内容存档于2009-07-09）. 
  46. ^ Xiph Subversion repository: trunk/theora-fpga. Xiph.Org基金會. [2009-08-10]. （原始内容存档于2009-07-31）. 
  47. ^ XiphWiki: Theora Hardware. Xiph.Org基金會. [10 August 2009]. （原始内容存档于2009-09-17）. 
  48. ^ MozillaWiki, Firefox3.5/Features, MozillaWiki, 18 March 2009 [11 October 2009], （原始内容存档于2010-07-06） 
  49. ^ Mozilla Corporation, Mozilla Firefox 3.5 Release Notes, Mozilla Corporation, 30 June 2009 [11 October 2009], （原始内容存档于2010-11-30） 
  50. ^ Mozilla Corporation, Firefox Mobile Features, Mozilla Corporation, 9 February 2010 [9 February 2010], （原始内容存档于2010-12-01） 
  51. ^ Google Chrome to support HTML 5 video, SoftSailor, 28 May 2009 [11 October 2009], （原始内容存档于2009年10月3日） 
  52. ^ Stephen Shankland, Google Chrome gets HTML video support, cnet news, 28 May 2009 [11 October 2009], （原始内容存档于2011-07-19） 
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  54. ^ Robert Kaiser, What's New in SeaMonkey 2.0 Beta 2, seamonkey-project.org, 16 September 2009 [11 October 2009], （原始内容存档于2010-06-26） 
  55. ^ Bugreport: Wish for audio/video element support in Konqueror, 13 May 2007 [2 December 2009], （原始内容存档于2012年12月28日） 
  56. ^ Plans for Konqueror 4.4, 26 November 2009 [2 December 2009], （原始内容存档于2011-07-17） 
  57. ^ Philip Jägenstedt. (re-)Introducing <video> - Official blog for Core developers at Opera. Opera. 2009-12-31 [2010-01-02]. （原始内容存档于2010-01-04）. 
  58. ^ Arjan van Leeuwen. Happy New Year! - Official blog for Core developers at Opera. Opera. 2009-12-31 [2010-01-02]. （原始内容存档于2010-01-04）. 
  59. ^ Experimental Opera-video build with native Ogg Theora support, Opera, 25 April 2007 [11 October 2009], （原始内容存档于2007-12-02） 
  60. ^ A call for video on the web - Opera <video> release on Labs, Opera, 7 November 2007 [11 October 2009], （原始内容存档于2010-10-22） 
检索自“https://zh.wikipedia.org/w/index.php?title=Theora&oldid=78946622”