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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
In the software development process, a reference implementation (or, less frequently, sample implementation or model implementation) is a program that implements all requirements from a corresponding specification. The reference implementation o ...
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
The public domain (PD) consists of all the creative work to which no exclusive intellectual property rights apply. Those rights may have expired, been forfeited, expressly waived, or may be inapplicable. Because those rights have expired, ...
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 #REDIRECT BBC #REDIRECT BBC
Here i going to introduce about the best teacher of my life b BALAJI sir. He is the precious gift that I got befor 2yrs . How has helped and thought all the concept and made my success in the 10th board exam. ...
...
's
Dirac codec.
Theora is named after
Theora Jones,
Edison Carter's Controller on the ''
Max Headroom'' television program.
Technical details
Theora is a
variable-bitrate,
DCT-based video compression scheme. Like most common video codecs, Theora also uses
chroma subsampling
Chroma subsampling is the practice of encoding images by implementing less resolution for chroma information than for luma information, taking advantage of the human visual system's lower acuity for color differences than for luminance.
It is u ...
,
block
Block or blocked may refer to:
Arts, entertainment and media Broadcasting
* Block programming, the result of a programming strategy in broadcasting
* W242BX, a radio station licensed to Greenville, South Carolina, United States known as ''96.3 ...
-based motion compensation and an 8-by-8 DCT block. Pixels are grouped into various structures, namely blocks, super blocks, and
macroblocks The macroblock is a processing unit in image and video compression formats based on linear block transforms, typically the discrete cosine transform (DCT). A macroblock typically consists of 16×16 samples, and is further subdivided into transform ...
. Theora supports intra-coded frames and forward-predictive frames, but not
bi-predictive frames which are found in
H.264
Advanced Video Coding (AVC), also referred to as H.264 or MPEG-4 Part 10, is a video compression standard based on block-oriented, motion-compensated coding. It is by far the most commonly used format for the recording, compression, and distr ...
and
VC-1. Theora also does not support
interlacing, or bit-depths larger than 8 bits per component.
Theora video streams can be stored in any suitable
container format, but they are most commonly found in the
Ogg container with
Vorbis or
FLAC audio streams. This combination 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.
[Xiph.or]
FAQ – Theora and VP3
Retrieved 2 September 2009 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.
History
Theora's predecessor ''On2 TrueMotion VP3'' was originally a
proprietary and patent-encumbered
video codec developed by
On2 Technologies. VP3.1 was introduced in May 2000 and followed three months later by the VP3.2 release, which is the basis for Theora.
Move to free software
In August 2001, On2 Technologies announced that they would be releasing an open source version of their VP3.2 video compression algorithm. In September 2001, On2 Technologies published the
source code
In computing, source code, or simply code, is any collection of code, with or without comments, written using a human-readable programming language, usually as plain text. The source code of a program is specially designed to facilitate the w ...
of the VP3.2 codec under the VP3.2 Public License 0.1,
a custom open-source license. The license only granted the right to modify the source code if the resulting larger work continued to support playback of VP3.2 data.
In March 2002, On2 responded to the public's reception by relicensing the VP3 codec under the
GNU Lesser General Public License
The GNU Lesser General Public License (LGPL) is a free-software license published by the Free Software Foundation (FSF). The license allows developers and companies to use and integrate a software component released under the LGPL into their own ...
. In June 2002, On2 donated VP3 to the Xiph.Org Foundation and offered it under the Ogg Vorbis
BSD-style license.
[Linux.com (23 June 2002]
Ogg Vorbis, VP3 combining forces to create Open Source multimedia package
Retrieved on 2009-08-16 On2 also made an irrevocable,
royalty-free license grant for any patent claims it might have over the software and any derivatives,
allowing anyone to use any VP3-derived codec for any purpose.
[Xiph.or]
libtheora license (Subversion – Trunk)
Retrieved on 16 August 2009[Xiph.or]
VP32 codec license (Subversion – Trunk)
Retrieved on 16 August 2009 In August 2002, On2 entered into an agreement with the Xiph.Org Foundation to make VP3 the basis of a new, free video codec, called Theora. On2 declared Theora to be VP3's successor. On 3 October 2002, On2 and Xiph announced the completion and availability of the initial alpha code release of ''libtheora'', Theora's reference implementation.
There is no formal specification for VP3's
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.
A successor to Theora,
Daala
Daala is a video coding format under development by the Xiph.Org Foundation under the lead of Timothy B. Terriberry mainly sponsored by the Mozilla Corporation. Like Theora and Opus, Daala is available free of any royalties and its reference im ...
, was later merged into
AV1
AOMedia Video 1 (AV1) is an open, royalty-free video coding format initially designed for video transmissions over the Internet. It was developed as a successor to VP9 by the Alliance for Open Media (AOMedia), a consortium founded in 2015 th ...
.
Theora I specification
The Theora I bitstream format was
frozen in June 2004 after the libtheora 1.0alpha3 release.
Videos encoded with any version of the libtheora since the alpha3 will be compatible with any future player.
This is also true for videos encoded with any implementation of the Theora I specification since the format freeze. The ''Theora I Specification'' was completely published in 2004.
Any later changes in the specification are minor updates.
The Theora reference implementation libtheora spent several years in
alpha and beta status.
The first alpha version was released on 25 September 2002 and the first beta version was released on 22 September 2007. The first stable release of libtheora was made in November 2008. Work then focused on improving the codec's 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, such as the new rate control module and the
two-pass rate control.
The codename for the next version of libtheora is ''Ptalarbvorm''.
Theora is well established as a video format in
open-source applications, and became the format used for
Wikipedia
Wikipedia is a multilingual free online encyclopedia written and maintained by a community of volunteers, known as Wikipedians, through open collaboration and using a wiki-based editing system. Wikipedia is the largest and most-read refer ...
's video content before being mostly replaced by
VP9. However, the proposed adoption of Theora as part of the baseline video support in HTML5
resulted in controversy.
Performance
Encoding performance
Evaluations of the VP3
and early Theora encoders
found that their subjective visual quality was inferior to that of contemporary video codecs. More recently however, Xiph developers compared the 1.1 Theora encoder to
YouTube
YouTube is a global online video sharing and social media platform headquartered in San Bruno, California. It was launched on February 14, 2005, by Steve Chen, Chad Hurley, and Jawed Karim. It is owned by Google, and is the second mo ...
's H.264 and
H.263+ encoders, in response to concerns raised in 2009 about Theora's inferior performance by
Chris DiBona, a
Google
Google LLC () is an American Multinational corporation, multinational technology company focusing on Search Engine, search engine technology, online advertising, cloud computing, software, computer software, quantum computing, e-commerce, ar ...
employee. They found the results from Theora to be nearly the same as YouTube's H.264 output, and much better than the H.263+ output.
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 claimed a considerable improvement in quality, both subjectively and as measured by
PSNR
Peak signal-to-noise ratio (PSNR) is an engineering term for the ratio between the maximum possible power of a Signal (information theory), signal and the power of corrupting noise that affects the fidelity of its representation. Because many sign ...
, just by improving the forward
DCT and quantisation matrices. A flaw in the version of
FFmpeg
FFmpeg is a free and open-source software project consisting of a suite of libraries and programs for handling video, audio, and other multimedia files and streams. At its core is the command-line ffmpeg tool itself, designed for processing of vid ...
used in the test initially led to incorrect reports of Theora PSNR surpassing that of
H.264
Advanced Video Coding (AVC), also referred to as H.264 or MPEG-4 Part 10, is a video compression standard based on block-oriented, motion-compensated coding. It is by far the most commonly used format for the recording, compression, and distr ...
. The differences in quality, bitrate and file size between a YouTube H.264 video and a transcoded Ogg video file are very small. Further work on adaptive quantization, as well as overall detailed subjective tuning of the codec, is still to come.
Playback performance
There is an
open-source VHDL
The VHSIC Hardware Description Language (VHDL) is a hardware description language (HDL) that can model the behavior and structure of digital systems at multiple levels of abstraction, ranging from the system level down to that of logic gate ...
code base for a hardware Theora decoder in development. It began as a 2006
Google
Google LLC () is an American Multinational corporation, multinational technology company focusing on Search Engine, search engine technology, online advertising, cloud computing, software, computer software, quantum computing, e-commerce, ar ...
Summer of Code project, and it has been developed on both the
Nios II
Nios II is a 32-bit embedded processor architecture designed specifically for the Altera family of field-programmable gate array (FPGA) integrated circuits. Nios II incorporates many enhancements over the original Nios architecture, making it mo ...
and
LEON processors. However, there are currently no Theora decoder chips in production, and
portable media players,
smartphone
A smartphone is a portable computer device that combines mobile telephone and computing functions into one unit. They are distinguished from feature phones by their stronger hardware capabilities and extensive mobile operating systems, whic ...
s and similar devices with limited computing power rely on such chips to provide efficient playback.
Playback
Native browser playback
As originally recommended by
HTML 5
HTML5 is a markup language used for structuring and presenting content on the World Wide Web. It is the fifth and final major HTML version that is a World Wide Web Consortium (W3C) recommendation. The current specification is known as the HTML L ...
, these browsers support Theora when embedded by the
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.
*
Tizen browser
*
SeaMonkey
SeaMonkey is a free and open-source Internet suite. It is the continuation of the former Mozilla Application Suite, based on the same source code, which itself grew out of Netscape Communicator and formed the base of Netscape 6 and Netscape ...
as of version 2.0.
*
Konqueror
Konqueror is a free and open-source web browser and file manager that provides web access and file-viewer functionality for file systems (such as local files, files on a remote FTP server and files in a disk image). It forms a core part of t ...
4.4.2
*
Opera
Opera is a form of theatre in which music is a fundamental component and dramatic roles are taken by singers. Such a "work" (the literal translation of the Italian word "opera") is typically a collaboration between a composer and a libr ...
as of version
10.50. It was also supported in
Opera 9.5 experimental video builds.
*
Web uses WebKitGTK+ as its rendering engine. As WebKitGTK+ uses
GStreamer
GStreamer is a pipeline-based multimedia framework that links together a wide variety of media processing systems to complete complex workflows. For instance, GStreamer can be used to build a system that reads files in one format, processes the ...
to implement the HTML5 media player, and all the formats GStreamer supports (including Theora) are available in browser.
*
Midori is another example of a browser that supports Theora by using WebKitGTK+.
Browser plugins
*
Annodex plugin via OggPlay
*
Cortado, a
Java
Java (; id, Jawa, ; jv, ꦗꦮ; su, ) is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea to the north. With a population of 151.6 million people, Java is the world's mos ...
based
applet
In computing, an applet is any small application that performs one specific task that runs within the scope of a dedicated widget engine or a larger program, often as a plug-in. The term is frequently used to refer to a Java applet, a program ...
**
Itheora, a PHP wrapper for Cortado
* Mv Embed HTML 5 video tag wrapper for numerous plugin types
*
VLC media player
VLC media player (previously the VideoLAN Client and commonly known as simply VLC) is a free and open-source, portable, cross-platform media player software and streaming media server developed by the VideoLAN project. VLC is available for desk ...
browser plugin for IE or Firefox
*
Microsoft Edge
Microsoft Edge is a proprietary, cross-platform web browser created by Microsoft. It was first released in 2015 as part of Windows 10 and Xbox One and later ported to other platforms as a fork of Google's Chromium open-source project: Android ...
, via the Web Media Extensions add-on
Supporting media frameworks
*
DirectShow with use of
OpenCodecs
*
GStreamer
GStreamer is a pipeline-based multimedia framework that links together a wide variety of media processing systems to complete complex workflows. For instance, GStreamer can be used to build a system that reads files in one format, processes the ...
supported via Theora or FFmpeg module, supports
GStreamer based applications e.g.
Totem and
Songbird
A songbird is a bird belonging to the suborder Passeri of the perching birds (Passeriformes). Another name that is sometimes seen as the scientific or vernacular name is Oscines, from Latin ''oscen'', "songbird". The Passeriformes contains 5000 ...
*
Phonon
*
QuickTime (including but not limited to Safari) with use of
Xiph QuickTime Components
*
Silverlight Highgate media suite is going to bring an Open Source Theora/Vorbis implementation in
Silverlight. It will enable installation-free support for HTML5 streaming video.
Supporting applications
*
FFmpeg
FFmpeg is a free and open-source software project consisting of a suite of libraries and programs for handling video, audio, and other multimedia files and streams. At its core is the command-line ffmpeg tool itself, designed for processing of vid ...
(own implementation)
*
Helix Player
*
Miro Media Player
Miro (formerly named Democracy Player or DTV) was an audio, video player and Internet television application developed by the Participatory Culture Foundation. It runs on Microsoft Windows, macOS, FreeBSD and Linux and supports most known video f ...
(formerly known as
Democracy Player)
*
MPlayer
MPlayer is a free and open-source media player software application. It is available for Linux, OS X and Microsoft Windows. Versions for OS/2, Syllable, AmigaOS, MorphOS and AROS Research Operating System are also available. A port for DOS using ...
and front-ends
*
Songbird
A songbird is a bird belonging to the suborder Passeri of the perching birds (Passeriformes). Another name that is sometimes seen as the scientific or vernacular name is Oscines, from Latin ''oscen'', "songbird". The Passeriformes contains 5000 ...
,
Totem,
Moovida and all
GStreamer
GStreamer is a pipeline-based multimedia framework that links together a wide variety of media processing systems to complete complex workflows. For instance, GStreamer can be used to build a system that reads files in one format, processes the ...
-based players
*
VLC (native support)
*
xine
xine is a multimedia playback engine for Unix-like operating systems released under the GNU General Public License. xine is built around a shared library (xine-lib) that supports different frontend player applications. xine uses libraries ...
and all libxine-based players like
Kaffeine
*
Dragon player
Dragon Player is a simple media player (application software), media player for the KDE desktop environment. It is the renamed continuation of a video player for KDE 3 called Codeine, which was originally created and developed by Max Howell, and ...
and all Phonon-based players
Encoding
There are several third-party programs that support encoding through libtheora:
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
BSD licenses are a family of permissive free software licenses, imposing minimal restrictions on the use and distribution of covered software. This is in contrast to copyleft licenses, which have share-alike requirements. The original BSD lice ...
.
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
GStreamer is a pipeline-based multimedia framework that links together a wide variety of media processing systems to complete complex workflows. For instance, GStreamer can be used to build a system that reads files in one format, processes the ...
framework has support for parsing raw Theora streams, encoding and decoding raw Theora streams to/from YUV video
Editing
Streaming
The following streaming media servers are capable of streaming Theora video:
Makers
Elphel
Elphel, Inc. designs and manufactures open hardware and free software cameras. The company was founded in 2001 by Russian physicist Andrey Filippov, who emigrated to the US in 1995.
Elphel cameras have been used to capture images for Google St ...
is the main maker of cameras that record in theora.
See also
*
Video editing software
Video editing software, or a video editor is software used performing the post-production video editing of digital video sequences on a non-linear editing system. It has replaced traditional flatbed celluloid film editing tools and analog video ...
*
Comparison of video codecs
*
Comparison of video encoders
Α video codec is software or a device that provides encoding and decoding for digital video, and which may or may not include the use of video compression and/or decompression. Most codecs are typically implementations of video coding formats. ...
References
External links
Theora.orgExamples of Theora-encoded videosWhy Theora Matters for Internet TVTheora user manualRTP Payload Format for Theora Encoded Video – Xiph.OrgIETF Internet Draft
H.264 and Theora codecs comparison
{{Xiph.org
Articles containing video clips
Free video codecs
Open formats
Software using the BSD license
Xiph.Org projects