Theora: Difference between revisions
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'''Theora''' is | '''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 == | ||
| Line 22: | Line 22: | ||
* 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 | ||
== Status == | == Status == | ||
* '''1. | * '''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 | * 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 | * 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 == | ||
| Line 34: | Line 32: | ||
* [[OggTheora|Mapping in Ogg]] | * [[OggTheora|Mapping in Ogg]] | ||
* [[TheoraTodo|ToDo list for development]] | * [[TheoraTodo|ToDo list for development]] | ||
* [[Cortado/release|Release checklist for the Cortado java applet]] | |||
== More information == | == More information == | ||
Latest revision as of 14:48, 8 August 2014
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
- VP3 homepage: The homepage of the codec Theora is based on
- On2 Technologies: The authors of VP3
- Ogg Theora Information on Doom9 Forum
- HOWTO: Rip DVD to Theora using Linux
- Codec shoot-out 2005 Comparison of many video codecs, including Theora