| ITU-T extensions to JPEG-1 |
| (T.85x Series) |
|
Background
The Joint Photographic Expert Group (JPEG) was founded in 1986 by its parent
bodies, the then ITU CCITT SG 8 and ISO/TC97/SC2/WG8 group. ITU-T Rec. T.81
| ISO/IEC 10918-1 specifies a process for digital compression and coding of
continuous-tone still images, and is known as the “JPEG image compression
scheme” that is pervasive today in the Internet, in digital photography and
in many other image compression applications. Originally approved in 1992
jointly first by ITU-T (then CCITT) and later by ISO/IEC, the JPEG Committee
went on after some years to define a newer family of image coding standards
that has a significantly broader application scope than the original JPEG
(namely still picture compression) and designed a broader “image
architecture” – which is known as “JPEG2000” and is published in the ITU-T
Rec. T.800 | ISO/IEC 15444 family of specifications. In the meantime, the
immensely popular JPEG suite was not updated over time to exploit advances
in image compression, even though it had been originally conceived as an
expandable “tool box” concept.
Starting in 2004, ITU-T Study Group 16 consulted with ISO/IEC JTC1 SC29/WG 1
(the full name of the JPEG committee in ISO/IEC) about bringing into the
original JPEG suite an alternative, royalty free arithmetic coder that would
allow much better image compression efficiency and lower latency. Eventually
it was decided by both groups that this would be an ITU-only extension of
the base algorithm, and in order to distinguish it clearly from the original
JPEG work, the specification was published after approval in September 2005
as ITU-T Rec. T.851 (“JPEG1-based still-image coding using an alternative
arithmetic coder”).
From the onset of the development, there was the desire to have a freely
available reference source code implementation of the alternative arithmetic
coder in T.851. This work is now being coordinated between various experts
aiming integration in the Independent JPEG Group distribution. Once stable,
the code for the T.851 alternative arithmetic coder is planned to be
formally approved as an Appendix to T.851, which could be easily updated as
the source code is updated .
Resources
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