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384 bytes added, 15:12, 7 July 2010
Reverted edits by ArcangelaGallo (Talk) to last revision by Ogg.k.ogg.k
'''Theora''' is our a video codec, based on the [[VP3]] codec donated by [[On2 Technologies]]. We've refined and extended it, giving it the same future scope for encoder improvement [[Vorbis]] has. See for more information.
== Features ==
Features available in the Theora format (and a comparison to VP3 and MPEG-4 ASP):
* 8x8 Type-II Discrete Cosine Transform
* block-based motion compensation
* 8x8 Type-II Discrete Cosine Transform
* free-form variable bit rates (VBR)
* adaptive in-loop deblocking applied to the edges of the coded blocks (not existing in MPEG-4 ASP)
* non-multiple of 16 picture sizes (as possible in ASP, but not in VP3)
* non-linear scaling of quants values (as done in MPEG-4 AVC)
* adaptive quantisation quantization down to the block level (as possible in MPEG-4 ASP/AVC, but not in VP3)
* intra frames (I-Frames in MPEG), inter frames (P-Frames), but no B-Frames (as supported in MPEG-4 ASP/AVC)
* HalfPixel Motion Search Precision (MPEG-4 ASP/AVC supports HalfPixel or QuarterPixel)
* technologies used already in Vorbis (decoder setup configuration, bitstream headers...) not available in VP3
Note that not all of these features are already implemented in the reference encoder/decoder.
== Status ==
* Beta '''1 .1.1''' is the latest stable release(2009-10-01).* The bitstream format was frozen in Theora alpha 1.0 Alpha 3on 2004-08-04: every file created with this encoder (and, of course, later encoders) will be playable by any compliant Theora decoder.* The decoder in 1.0 Alpha 8 implemented all features of the [ Theora Format Specification]: every file created by any compliant Theora encoder will be playable by the decoder in 1.0 Alpha 8 (and, of course, later decoders).
== Development ==
* [[Theora:Beta1ToDoOggTheora|Todo Mapping in Ogg]]* [[TheoraTodo|ToDo list for development]]* [[Cortado/release|Release checklist for Beta1the Cortado java applet]]
== More information ==
It's possible to convert VP3 video to Theora. See [[vp3toTheora]].
== External links ==
* [ Ogg Theora Information on Doom9 Forum]
* [ HOWTO: Rip DVD to Theora using Linux]
* [ Codec shoot-out 2005] Comparison of many video codeccodecs, including theoraTheora [[Category:Theora]]

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