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):
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Features available in the Theora format (and a comparison to VP3 and MPEG-4 ASP):
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* block-based motion compensation
 
* 8x8 Type-II Discrete Cosine Transform
* 8x8 Type-II Discrete Cosine Transform
 +
* block-based motion compensation
* 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)
-
* block sizes down to 8x8 (MPEG-4 ASP supports normally only 16x16)
+
* 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)
* 384 8x8 custom quantization matrices: intra/inter, luma/chroma and even each quant (more than VP3 and MPEG-4 ASP/AVC)
-
* adaptive entropy encoding (MPEG-4 ASP does'nt support adaptivity)
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* 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)
* 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
* 8 bits per pixel per color channel
* multiple reference frames (not possible in MPEG-4 ASP)
* multiple reference frames (not possible in MPEG-4 ASP)
* pixel aspect ratio (eg for anamorphic signalling/playback)
* 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)
* 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)
+
* 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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* '''1.1.1''' is the latest stable release (2009-10-01).  
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Alpha 5 is the latest release. The bitstream format is frozen. Every file created with the alpha 3 encoder (and, of course, later encoders) will be playable with future decoders. Beta 1 will be the next release.
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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).
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* It would be nice if somewhere it could be explained if Theora is a format appropriate for editing video - such formats would not do frame to frame compression and the file size and processor load would be smaller.  On the other hand a distribution format would want to pack in a lot of compression which would mean using frame to for compression.
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== Development ==
== Development ==
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* [[Theora:Beta1ToDo|Todo for Beta1]]
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* [[OggTheora|Mapping in Ogg]]
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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 ==
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{{Template:Theora}}
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* [[TheoraHardware]]: List of hardware-players supporting Ogg Theora
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It's possible to convert VP3 video to Theora. See [[vp3toTheora]].
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* [[TheoraSoftwarePlayers]]: List of media players that can play Ogg Theora
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* [[TheoraDecoders]]: List of decoders
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* [[TheoraEncoders]]: List of encoders
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== External links ==
== External links ==
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* [[Wikipedia: Theora]]
* [[Wikipedia: Theora]]
* [http://www.vp3.com VP3 homepage]: The homepage of the codec Theora is based on
* [http://www.vp3.com VP3 homepage]: The homepage of the codec Theora is based on
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* [http://www.on2.com On2 Technologies]: The creators of VP3
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* [http://www.on2.com On2 Technologies]: The authors of VP3
* [http://forum.doom9.org/showthread.php?s=&threadid=77314 Ogg Theora Information on Doom9 Forum]
* [http://forum.doom9.org/showthread.php?s=&threadid=77314 Ogg Theora Information on Doom9 Forum]
 +
* [http://www.parrishtech.com/content/view/16/1/ HOWTO: Rip DVD to Theora using Linux]
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* [http://www.doom9.org/index.html?/codecs-quali-105-1.htm Codec shoot-out 2005] Comparison of many video codecs, including Theora
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 +
[[Category:Theora]]

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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