Ogg Theora
 |
|
| Filename extension | .ogv, .ogg |
|---|---|
| Internet media type | video/ogg |
| Developed by | Xiph.org |
| Initial release | 1 June 2004 |
| Latest release |
Theora I
(16 March 2011) |
| Type of format | Compressed video |
| Contained by | Ogg, Matroska |
| Extended from | VP3 |
| Standard | Specification |
| Open format? | Yes |
| Website | theora.org |
| Developer(s) | Xiph.org |
|---|---|
| Initial release | 3 November 2008 (1.0) |
| Stable release |
1.1.1 / 1 October 2009
|
| Preview release |
1.2.0 Alpha 1 / 24 September 2010
|
| Development status | Inactive |
| Written in | C |
| Operating system | Unix-like (incl Linux, Mac OS X), Windows |
| Type | Video codec, reference implementation |
| License | 3-clause BSD |
| Website | theora.org |
Theora is a free lossy video compression format. It is developed by the Xiph.Org Foundation and distributed without licensing fees alongside their other free and open media projects, including the Vorbis audio format and the Ogg container.
The libtheora video codec is the reference implementation of the Theora video compression format being developed by the Xiph.Org Foundation.
Theora is derived from the formerly proprietary VP3 codec, released into the public domain by On2 Technologies. It is broadly comparable in design and bitrate efficiency to MPEG-4 Part 2, early versions of Windows Media Video, and RealVideo while lacking some of the features present in some of these other codecs. It is comparable in open standards philosophy to the BBC's Dirac codec.
Theora is named after Theora Jones, Edison Carter's Controller on the Max Headroom television program.
Theora is a variable-bitrate, DCT-based video compression scheme. Like most common video codecs, Theora also uses chroma subsampling, block-based motion compensation and an 8-by-8 DCT block. Pixels are grouped into various structures, namely blocks, super blocks, and macroblocks. Theora supports intra-coded frames and forward-predictive frames, but not bi-predictive frames which are found in H.264 and VC-1. Theora also does not support interlacing, or bit-depths larger than 8 bits per component.
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