Theora

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'''Theora''' is our 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 http://theora.org/ for more information.
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'''Theora''' is 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 http://theora.org/ for more information.
== Features ==
== Features ==
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Features available in the Theora format (and a comparison to VP3 and MPEG-4 ASP):
Features available in the Theora format (and a comparison to VP3 and MPEG-4 ASP):
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* 8x8 Type-II Discrete Cosine Transform
* block-based motion compensation
* block-based motion compensation
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* 8x8 Type-II Discrete Cosine Transform
 
* free-form variable bit rates (VBR)
* free-form variable bit rates (VBR)
* adaptive in-loop deblocking applied to the edges of the coded blocks (not existing in MPEG-4 ASP)
* adaptive in-loop deblocking applied to the edges of the coded blocks (not existing in MPEG-4 ASP)
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* non-multiple of 16 picture sizes (as possible in ASP, but not in VP3)
* 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)
* non-linear scaling of quants values (as done in MPEG-4 AVC)
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* adaptive quantisation down to the block level (as possible in MPEG-4 ASP/AVC, but not in VP3)
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* adaptive 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)
* 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)
* 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
* technologies used already in Vorbis (decoder setup configuration, bitstream headers...) not available in VP3
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Note that not all of these features are already implemented in the reference encoder/decoder.
 
== Status ==
== Status ==
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* Beta 2 is the latest stable release (2007-Okt-12).  
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* '''1.1.1''' is the latest stable release (2009-10-01).  
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* The bitstream format was frozen in Theora alpha 3: every file created with this encoder (and, of course, later encoders) will be playable by any compliant Theora decoder.
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* The bitstream format was frozen in 1.0 Alpha 3 on 2004-08-04: every file created with this encoder (and, of course, later encoders) will be playable by any compliant Theora decoder.
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* The decoder in 1.0 Alpha 8 implemented all features of the [http://theora.org/doc/Theora.pdf 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 ==
== Development ==
* [[OggTheora|Mapping in Ogg]]
* [[OggTheora|Mapping in Ogg]]
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* [[TheoraTodo|Todo list for development]]
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* [[TheoraTodo|ToDo list for development]]
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* [[Cortado/release|Release checklist for the Cortado java applet]]
==  More information ==
==  More information ==

Revision as of 23:12, 7 July 2010

Theora is 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 http://theora.org/ for more information.

Contents

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
  • free-form variable bit rates (VBR)
  • adaptive in-loop deblocking applied to the edges of the coded blocks (not existing in MPEG-4 ASP)
  • block sizes down to 8x8 (MPEG-4 ASP supports 8x8 only with 4MV)
  • 384 8x8 custom quantization matrices: intra/inter, luma/chroma and even each quant (more than VP3 and MPEG-4 ASP/AVC)
  • flexible entropy encoding (Theora supports 80 VLC tables selectable per-frame, MPEG-4 ASP has just one)
  • 4:2:0, 4:2:2, and 4:4:4 chroma subsampling formats (VP3 and MPEG-4 ASP only support 4:2:0)
  • 8 bits per pixel per color channel
  • multiple reference frames (not possible in MPEG-4 ASP)
  • pixel aspect ratio (eg for anamorphic signalling/playback)
  • 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 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

Status

  • 1.1.1 is the latest stable release (2009-10-01).
  • The bitstream format was frozen in 1.0 Alpha 3 on 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

More information

It's possible to convert VP3 video to Theora. See vp3toTheora.

External links

Retrieved from "http://wiki.xiph.org/Theora"
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