Theora is a video codec being developed by the Xiph.org Foundation as part of their Ogg project. Based upon the VP3 codec from On2 Technologies, and christened by On2 as the successor in VP3's lineage, Theora is targeted at competing with MPEG-4 video (e.g., XviD and DivX), RealVideo, Windows Media Video, and similar lower-bitrate video compression schemes. Theora is an 8x8 DCT-II transform codec like competing MPEG-4 video schemes, but differs in that it only uses I (intra) and P (inter) frames, with no corresponding B (bi-predictive) frames.
Theora is still in developmental stages with Xiph.org having made five alpha releases thus far.
- Alpha One was released on September 25, 2002
- Alpha Two was released half on December 16 and half on December 27, 2002
- Alpha Three was released on March 20, 2004
- Alpha Four was released on December 15, 2004.
- Alpha Five was released on August 20, 2005.
The first beta release Beta-1 is expected later in 2006. Theora is released under the terms of a BSD-style license.
While VP3 is patented technology, On2 has irrevocably given royalty-free license of the VP3 patents to all of mankind, enabling the public to utilize Theora and other VP3-derived codecs for any imaginable purpose.
Ralph Giles heads up the Theora project.
In the Ogg multimedia framework, Theora provides a video layer, while Vorbis acts as the audio layer.
Theora is named for Theora Jones, Edison Carter's Controller on the Max Headroom television program.