Coordinates | 52°24′″N16°55′″N |
---|---|
name | Theora |
extension | .ogv, .ogg |
mime | video/ogg |
owner | Xiph.org |
released | |
latest release version | Theora I |
latest release date | 5 August 2009 |
genre | Video compression format |
contained by | Ogg, Matroska |
extended from | VP3 |
standard | Specification |
url | }} |
name | libtheora |
---|---|
developer | Xiph.org |
released | (1.0) |
latest release version | 1.1.1 |
latest release date | |
latest preview version | 1.2.0 Alpha 1 |
latest preview date | |
programming language | C |
operating system | Unix-like (incl GNU/Linux, Mac OS X), Windows |
status | Active |
genre | Video codec, reference implementation |
license | 3-clause BSD |
website | www.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.
libtheora is a reference implementation of the Theora video compression format being developed by the Xiph.Org Foundation.
Theora is derived from the 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 video streams can be stored in any suitable container format. Most commonly it is found in the Ogg container with Vorbis or FLAC audio streams which provides a completely open, royalty-free multimedia format. It can also be used with the Matroska container.
The Theora video-compression format is essentially compatible with the VP3 video-compression format, consisting of a backward-compatible superset. Theora is a superset of VP3, and VP3 streams (with some minor syntactic modifications) can be converted into Theora streams without recompression (but not vice versa). VP3 video compression can be decoded using Theora implementations, but Theora video compression usually cannot be decoded using old VP3 implementations.
There is no formal specification for the VP3 bitstream format beyond the VP3 source code published by On2 Technologies. In 2003, Mike Melanson created an incomplete description of the VP3 bitstream format and decoding process at a higher level than source code, with some help from On2 and Xiph.Org Foundation. The Theora specification adopted some portions of this VP3 description.
The Theora reference implementation libtheora spent several years in alpha and beta status. The last alpha version was libtheora 1.0alpha7 released on June 20, 2006. It was followed by libtheora 1.0 beta1 on September 22, 2007. The last beta version was libtheora 1.0 beta3 released on April 16, 2008. The first stable release of libtheora as version 1.0 was made in November 2008. Work then focused on improving the codec performance in the ''"Thusnelda"'' branch, which was released as version 1.1 in September 2009 as the second stable libtheora release. This release brought some technical improvements and new features, e.g. the new rate control module and the new two-pass rate control.
The codename for the next version of Theora reference implementation (libtheora) is ''Ptalarbvorm''.
Theora is well established as a video format in open source applications, and is the format used for Wikipedia's video content. However, the proposed adoption of Theora as part of the baseline video support in HTML5 resulted in controversy.
The performance characteristics of the Theora 1.0 reference implementation are dominated mostly by implementation problems inherited from the original VP3 code base. Work leading up to the 1.1 stable release was focused on improving on or eliminating these. A May 2009 review of this work shows a considerable improvement in quality, both subjectively and as measured by PSNR, just by improving the forward DCT and quantisation matrices. A flaw in the version of FFmpeg used in the test initially led to incorrect reports of Theora PSNR surpassing that of H.264. Although not achieving this goal, the improvement in the measured PSNR and the perceived quality is considerable. In any case, the differences in quality, bitrate and file size between a YouTube H.264 video and a transcoded Ogg video file are negligible. Further work on adaptive quantization, as well as overall detailed subjective tuning of the codec, is still to come.
video
element:
Mozilla Firefox 3.5 and later versions including Firefox for mobile (Fennec). Google Chrome as of version 3.0.182.2 including Chromium as of 14 July 2009. SeaMonkey as of version 2.0. Konqueror 4.4.2 Opera as of version 10.50. It was also supported in Opera 9.5 experimental video builds.
{| style="text-align: center; width: 95%" class="wikitable" ! rowspan="2" | Name ! rowspan="2" | Description ! colspan="3" | Operating Systems Supported |- | style="width: 10%;" | Unix-like | style="width: 10%;" | Mac OS X | style="width: 10%;" | Windows |- | style="text-align: left;" | ; Firefogg | style="text-align: left;" | A Firefox browser extension implementation of ffmpeg2theora | | | |- | style="text-align: left;" | ; ffmpeg2theora | style="text-align: left;" | A command-line program that transcodes video by decoding with FFmpeg and reencoding with libtheora to encode it | | | |- | style="text-align: left;" | ; VLC | style="text-align: left;" | Can transcode to single-pass Theora 1.0 and optionally stream it | | | |- | style="text-align: left;" | ; OggConvert | style="text-align: left;" | Transcodes supported media to Vorbis, Theora, or Dirac | | ? | |- | style="text-align: left;" | ; FreeJ | style="text-align: left;" | "Video DJing" software that can encode to and stream Theora | | | ? |- | style="text-align: left;" | ; Kdenlive''' | style="text-align: left;" | The video editor supplied with KDE | | ? | ? |- | style="text-align: left;" | ; PiTiVi | style="text-align: left;" | The video editor supplied with GNOME | | ? | ? |- | style="text-align: left;" | ; LiVES | style="text-align: left;" | Video editing software for Linux. Can edit, encode and stream theora. | | | ? |- | style="text-align: left;" | ; Thoggen | style="text-align: left;" | A GTK+ and GStreamer based DVD backup utility | | ? | ? |- | style="text-align: left;" | ; HandBrake | style="text-align: left;" | Can output to Theora only with the Matroska container | | | |- | style="text-align: left;" | ; Recordmydesktop | style="text-align: left;" | Records the screen to Ogg Theora with optional Vorbis audio | | ? | ? |}
The libtheora library contains the reference implementation of the Theora specification for encoding and decoding. libtheora is still under development by the Xiph.Org Foundation. The library is released under the terms of a BSD-style license.
Also, several media frameworks have support for Theora.
The open-source ffdshow audio/video decoder is capable of encoding Theora videos using its Video for Windows (VFW) multi-codec interface within popular AVI editing programs. It supports both encoding and decoding Theora video streams and uses Theora's alpha 4 libraries. However, many of the more refined features of Theora aren't available to the user in ffdshow's interface. The GStreamer framework has support for parsing raw Theora streams, encoding and decoding raw Theora streams to/from YUV video
{| style="text-align: center; width: 95%" class="wikitable" ! rowspan="2" | Name ! rowspan="2" | Description ! colspan="3" | Operating Systems Supported |- | style="width: 10%;" | Unix-like | style="width: 10%;" | Mac OS X | style="width: 10%;" | Windows |- | style="text-align: left;" | ; VLC | | | | |- | style="text-align: left;" | ; Icecast | | | ? | |- | style="text-align: left;" | ; FreeCast | style="text-align: left;" | Peer-to-peer streaming. Written in Java | | ? | |- | style="text-align: left;" | ; LiVES | style="text-align: left;" | Can stream ogg/theora/vorbis in realtime to a file or fifo. | | | ? |- | style="text-align: left;" | ; Flumotion | style="text-align: left;" | Streaming media server. | | ? | ? |}
Theora Streaming Studio is a complete client to connect to an Icecast server.
Category:Video codecs Category:Xiph.Org projects Category:Free multimedia codecs, containers, and splitters
als:Theora ar:ثيورا ca:Theora cs:Theora da:Theora de:Theora es:Theora eo:Theora fr:Theora ko:테오라 id:Theora it:Theora hu:Theora ml:തിയോറ nl:Theora (compressieformaat) ja:Theora no:Theora pl:Theora pt:Theora ru:Theora sk:Theora fi:Theora sv:Ogg Theora tr:Theora uk:Theora yo:Theora zh:TheoraThis text is licensed under the Creative Commons CC-BY-SA License. This text was originally published on Wikipedia and was developed by the Wikipedia community.
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