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Dirac is a prototype algorithm for the encoding and decoding of raw video. It was presented by the BBC in January 2004 as the basis of a new codec for the transmission of video over the Internet. The codec was finalised on January 21, 2008, and further developments will only be bug fixes and constraints^[1]. The immediate aim is to be able to decode standard digital PAL TV definition (720 x 576i pixels per frame at 25 frames per second) in real time; the reference implementation can decode around 17 frames per second on a 3 GHz PC but extensive optimisation is planned. This implementation is written in C++ and was released at SourceForge on 11 March 2004.

The codec is named in honour of the British scientist Paul Dirac.

Technology

Similar to common video codecs such as the ISO/IEC Moving Picture Experts Group (MPEG)'s MPEG-4 Part 2 or Microsoft's WMV 7, it can compress any size of picture from low-resolution QCIF (176x144 pixels) to HDTV (1920x1080) and beyond. However, it promises significant savings in bandwidth and improvements in quality over these codecs, by some claims even superior to those promised by the latest generation of codecs such as H.264/MPEG-4 AVC or SMPTE's VC-1 (which is based on Microsoft's WMV 9), by employing wavelet compression, instead of the discrete cosine transforms used in older codecs. Dirac's implementors make the preliminary claim of "a two-fold reduction in bit rate over MPEG-2 for high definition video"[1], an estimate which would put the design in about the same class of compression capability as the latest standardization efforts of H.264/MPEG-4 AVC and VC-1. MPEG-2 is the previous generation video codec used in the standard DVD format today.

Dirac is one of several projects attempting to apply wavelets to video compression. Others include Rududu [2], Snow and Tarkin. Wavelet compression has already proven its viability in the JPEG 2000 compression standard for photographic images.

The Schrödinger Project

A second implementation of the dirac codec called "Schrödinger" aims to provide portable libraries as well as accompanying GStreamer plugins. The project is written in C. It also hopes to allow embedding Dirac inside the Ogg container format. The project is named after Erwin Schrödinger.

On 22nd of February 2008, Schrödinger 1.0.0 was released. This release was able to decode HD720/25p in real-time on a Core Duo laptop.

License

The BBC is releasing the source to the reference implementation of Dirac under the free software and open source Mozilla Public License, the GNU GPL 2 and the GNU LGPL. This may accelerate its adoption and lower entry costs into the emerging industry of Internet television.

While the BBC own some patents on Dirac, they have irrevocably granted a royalty-free licence for their Dirac-related patents to everyone. In addition, the BBC have checked (by extensive patent search) that Dirac does not infringe any third party patents, enabling the public to use Dirac for any imaginable purpose.

External links

Dirac project page
Dirac project project page on SourceForge
BBC Research and Development the Department (largely) working on the codec
Schrödinger project
DirectShow filter binaries and howto

References

^ Dirac Specification

[1] Dirac Specification

[1]

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 Similar to common video [[codec]]s such as the [[International Organization for Standardization|ISO]]/[[International Electrotechnical Commission|IEC]] Moving Picture Experts Group ([[MPEG]])'s [[MPEG-4]] Part 2 or [[Microsoft|Microsoft's]] WMV 7, it can compress any size of picture from low-resolution [[QCIF]] (176x144 pixels) to [[HDTV]] (1920x1080) and beyond.  However, it promises significant savings in bandwidth and improvements in quality over these codecs, by some claims even superior to those promised by the latest generation of codecs such as [[H.264/MPEG-4 AVC]] or [[SMPTE]]'s [[VC-1]] (which is based on Microsoft's WMV 9), by employing [[wavelet compression]], instead of the [[discrete cosine transform]]s used in older codecs.  Dirac's implementors make the preliminary claim of "''a two-fold reduction in bit rate over MPEG-2 for high definition video''"[http://www.bbc.co.uk/rd/projects/dirac/overview.shtml], an estimate which would put the design in about the same class of compression capability as the latest standardization efforts of [[H.264/MPEG-4 AVC]] and [[VC-1]].  [[MPEG-2]] is the previous generation video codec used in the standard [[DVD]] format today.
+Dirac is one of several projects attempting to apply wavelets to video compression.  Others include [[Rududu]] [http://rududu.ifrance.com/rududu/], [[Snow (codec)|Snow]] and [[Tarkin (codec)|Tarkin]]. Wavelet compression has already proven its viability in the [[JPEG 2000]] compression standard for photographic images.
-Dirac is one of several projects attempting to apply wavelets to video compression.  Others include [[Rududu]] [http://rududu.ifrance.com/rududu/], [[Snow (codec)|Snow]] and [[Tarkin (codec)|Tarkin]]. Wavelet compression has already proven its viability in the [[JPEG 2000]] compression standard for photographic images. However, it has not been shown to provide substantially superior compression capability than other techniques based on more traditional block-based coding.  For example, [[H.264/MPEG-4 AVC]] is often as good or better in compression capability for still images, despite the wavelet-based design of JPEG-2000 <ref>Till Halbach. Performance comparison: H.26L intra coding vs. JPEG2000. Technical Report D039, ITU-T,Q15/SG16 and ISO/IEC,MPEG (JVT), July 2002</ref><ref>P. Topiwala, T. Tran, W. Dai, "Performance Comparison of JPEG2000 and H.264/AVC High Profile Intra–Frame Coding on HD Video Sequences", ''SPIE Annual Conference'', August 2006.</ref><ref>M. Ouaret, F. Dufaux, and T. Ebrahimi, "On comparing JPEG2000 and Intraframe AVC", ''SPIE annual conference'', August 2006</ref><ref>D. Marpe, V. George, and T. Wiegand, "Performance comparison of intra-only H.264/AVC HP and JPEG2000 for a set of monochrome ISO/IEC test images", [http://ftp3.itu.ch/av-arch/jvt-site/2004_10_Palma/JVT-M014.zip JVT-M014], 18-22 Oct., 2004</ref><ref>D. Marpe, V. George, H. L. Cycon, and K. U. Barthel, "Performance Evaluation of Motion-JPEG2000 in Comparison with H.264 / AVC Operated in Intra Coding Mode", [http://www.f4.fhtw-berlin.de/~barthel/paper/spie03_marpe_et_al.pdf MARPE03], ''Proc. SPIE'', Vol. 5266, pp. 129-137, Feb. 2004.</ref><ref>D. Marpe, S. Gordon, and T. Wiegand, "H.264/MPEG4-AVC Fidelity Range Extensions: Tools, Profiles, Performance, and Application Areas", ''IEEE Int'l. Conf. on Image Proc.'', Genova, Italy, Sept. 2005</ref>.  The primary benefits of JPEG-2000 relative to other codecs are functionality aspects, such as scalability features, rather than compression capability.
 == The Schrödinger Project ==