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Theora is offered by the Xiph.org foundation as a free and open video compression format. As it is a Xiph.org multimedia technology, it can be used to distribute film and video online and on disc without the licensing and royalty fees or vendor lock-in associated with other formats. Theora can handle video right up to High-definition content. Theora is in full public release as of November 3, 2008. The bitstream format for Theora I was frozen Thursday, 2004 July 1. All bitstreams encoded since that date will remain compatible with future releases.
The Theora specification is in the public domain, its reference implementation is open source and subject to a license which permits inclusion in proprietary commercial products. On2, which owns patents that apply to the technical foundations of Theora, granted an unrevocable free license regarding those patents.
Theora is suitable for Internet streaming, like the OGG formats. It can be streamed from virtually any HTTP server, making it easy to provide static streams. On the technological side Theora is well engineered for low-bitrate streaming. Its in-loop deblocking filter is efficient at preventing a distracting, blocky look of the encoded content. Thus perceived video quality usually degrades gracefully as bitrate decreases, which is an essential property for any video codec targeting web video.
Theora is also available on all operating systems through software (it is supported by the VideoLAN Client software).