Theora: Difference between revisions

Revision as of 06:00, 7 April 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.

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

Theora Hardware: List of hardware-players supporting Ogg Theora
TheoraSoftwarePlayers: List of media players that can play Ogg Theora
TheoraSoftwareEncoders: List of software that can encode to Ogg Theora
TheoraDecoders: List of decoder implementations
TheoraEncoders: List of encoder implementations
List of Theora videos: Get some files to see what the codec's like
Games that use Theora: List of known games that use Theora
TheoraTestsuite: Different samples to test player compliance

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

External links

Theora homepage
Theora documentation daily builds
Wikipedia: Theora
video to iPhone
VP3 homepage: The homepage of the codec Theora is based on
On2 Technologies: The authors of VP3
Ogg Theora Information on Doom9 Forum
video to 3gp
HOWTO: Rip DVD to Theora using Linux
iPod video converter
Codec shoot-out 2005 Comparison of many video codecs, including Theora

@@ Line 44: / Line 44: @@
 * [http://www.annodex.net/software/theora/ Theora documentation daily builds]
 * [[Wikipedia: Theora]]
+* [http://www.pavtube.com/video_to_iphone/ video to iPhone]
 * [http://www.vp3.com VP3 homepage]: The homepage of the codec Theora is based on
 * [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://www.pavtube.com/video_to_3gp/ video to 3gp]
 * [http://www.parrishtech.com/content/view/16/1/ HOWTO: Rip DVD to Theora using Linux]
+* [http://www.pavtube.com/video_to_ipod/ iPod video converter]
 * [http://www.doom9.org/index.html?/codecs-quali-105-1.htm Codec shoot-out 2005] Comparison of many video codecs, including Theora
 [[Category:Theora]]