https://wiki.xiph.org/api.php?action=feedcontributions&feedformat=atom&user=Sparrish 2026-05-02T02:48:05Z User contributions MediaWiki 1.45.1 https://wiki.xiph.org/index.php?title=Theora&diff=2240 2005-11-29T01:39:17Z

<p>Sparrish: /* External links */</p> <hr /> <div>'''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.<br /> <br /> == Features ==<br /> <br /> Features available in the Theora Format (and a comparison to VP3 and MPEG-4 ASP):<br /> <br /> * block-based motion compensation<br /> * 8x8 Type-II Discrete Cosine Transform<br /> * free-form variable bit rates (VBR)<br /> * adaptive in-loop deblocking applied to the edges of the coded blocks (not existing in MPEG-4 ASP)<br /> * block sizes down to 8x8 (MPEG-4 ASP supports normally only 16x16)<br /> * 384 8x8 custom quantization matrices: intra/inter, luma/chroma and even each quant (more than VP3 and MPEG-4 ASP/AVC)<br /> * adaptive entropy encoding (MPEG-4 ASP does'nt support adaptivity)<br /> * 4:2:0, 4:2:2, and 4:4:4 chroma subsampling formats (VP3 and MPEG-4 ASP only support 4:2:0)<br /> * 8 bits per pixel per color channel<br /> * multiple reference frames (not possible in MPEG-4 ASP)<br /> * pixel aspect ratio (eg for anamorphic signalling/playback)<br /> * non-linear scaling of quants values (as done in MPEG-4 AVC)<br /> * adaptive quantisation down to the block level (as possible in MPEG-4 ASP/AVC)<br /> * intra frames (I-Frames in MPEG), inter frames (P-Frames), but no B-Frames (as supported in MPEG-4 ASP/AVC)<br /> * HalfPixel Motion Search Precision (MPEG-4 ASP/AVC supports HalfPixel or QuarterPixel)<br /> * technologies used already in Vorbis (decoder setup configuration, bitstream headers...) not available in VP3<br /> <br /> Note that not all of these features are already implemented in the reference encoder/decoder.<br /> <br /> == Status ==<br /> <br /> 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.<br /> <br /> * 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.<br /> <br /> == Development ==<br /> <br /> * [[Theora:Beta1ToDo|Todo for Beta1]]<br /> <br /> == More information ==<br /> <br /> * [[TheoraHardware]]: List of hardware-players supporting Ogg Theora<br /> * [[TheoraSoftwarePlayers]]: List of media players that can play Ogg Theora<br /> * [[TheoraDecoders]]: List of decoders<br /> * [[TheoraEncoders]]: List of encoders<br /> <br /> == External links ==<br /> <br /> * [http://www.theora.org/ Theora homepage]<br /> * [http://www.annodex.net/software/theora/ Theora documentation daily builds]<br /> * [[Wikipedia: Theora]]<br /> * [http://www.vp3.com VP3 homepage]: The homepage of the codec Theora is based on<br /> * [http://www.on2.com On2 Technologies]: The creators of VP3<br /> * [http://forum.doom9.org/showthread.php?s=&amp;threadid=77314 Ogg Theora Information on Doom9 Forum]<br /> * [http://www.parrishtech.com/content/view/16/1/ HOWTO: Rip DVD to Theora using Linux]</div>

Sparrish