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 Monday, 05 June 2006

ITU-T together with the Independent Joint Photographic Expert Group (IJG) is celebrating the twentieth anniversary of the formation of the CCITT/ITU-T and ISO Joint Photographic Expert Group (JPEG) with the release of an alpha version of software for a new more efficient compression scheme. The new ITU extension to JPEG known as ITU-T Recommendation T.851 means that compression is increased such that images will take-up less space on people’s hard drives or digital cameras.

The program available here allows users to input image files for compression at a more efficient rate than that currently offered. The group responsible for producing the open source software is inviting people to test and contribute to the development of the project.

Recently, and capitalizing on the ‘toolbox’ concept of the original JPEG design, ITU-T approved ITU-T Rec. T.851, a royalty-free extension that adds to T.81, more commonly known as JPEG, an alternative compression method using so-called Q15 arithmetic coding. Q15 provides not only higher compression ratios for stored and transmitted images, but - compared to the original arithmetic coding in JPEG - also lower latency for compressing and displaying images. T.851 also extends the color precision of JPEG to maximum 16 bits per color component, which is seen as essential in applications such as medical imaging, professional photography and high quality printing.

Founded in 1986 by its parent bodies, the then ITU CCITT Study Group VIII and the ISO/TC97/SC2/WG8 group, JPEG continues today under the auspices of ISO/IEC JTC1 SC29/WG1 and ITU-T Study Group 16. The most famous product of JPEG was ITU-T Recommendation T.81 | ISO/IEC 10918-1, which specifies a process for digital compression and coding of continuous-tone still images, and is more commonly known by the name of the group, JPEG. This is the most used format for storing and transmitting photographs on the Internet, in digital photography and in many other image compression applications, and it was approved in 1992 first by ITU-T (then CCITT) and later by ISO/IEC.

Work on the new compression algorithm was started in 2004 by ITU-T Study Group 16. The aim was to allow users to take advantage of recent technological advances, with the addition to the JPEG suite of an alternative, royalty free coder that would allow even better image compression efficiency and lower latency. The successful completion of this first phase of the work resulted in the publication of the specification ITU-T Rec. T.851 after approval in September 2005. Experts from SG 16 say to stay tuned for further developments.