Bug#602034: (no subject)
Just FYI-- Fedora has scrapped its plans to update to the libjpeg v8
ABI, and further research
(http://www.libjpeg-turbo.org/About/SmartScale) has raised
questions/concerns regarding whether the features introduced in libjpeg
v7 and later really solve any problems that couldn't already be solved
via other means. Until or unless SmartScale is adopted as an official
standard or more compelling research comes to light regarding its
usefulness as a format, it is our (The libjpeg-turbo Project's) position
that supporting it will do more harm than good. To quote Tom Lane
(http://lists.fedoraproject.org/pipermail/devel/2013-January/176400.html),
"If there were a huge improvement in compression performance maybe
there'd be some chance of establishing a new de facto standard, but
there isn't --- so this will accomplish little except to fragment the
market."
The less controversial features of libjpeg v8 -- arithmetic coding
(which is part of the official JPEG spec, even though it isn't widely
used), the in-memory source/destination managers, support for additional
decompression scaling factors, etc. have all been back-ported as
extensions to libjpeg-turbo's API, thus allowing libjpeg-turbo to
support those features of libjpeg v8 without breaking backward ABI
compatibility for applications that don't use the features. It is safe
to assume that, for the forseeable future, the emulated libjpeg v8 API
in libjpeg-turbo will remain feature-incomplete and will not actually
support any features that can't also be accessed through our libjpeg
v6b-compatible API. Thus, the only compelling reason to use libjpeg v8
emulation in libjpeg-turbo is in situations where the platform or
application has already upgraded to libjpeg v8 and maintaining ABI
compatibility with previous releases of the application/platform is desired.
If there are any applications that actually use the SmartScale or
forward DCT scaling features, I would be very interested to hear about
them. We (myself and Fedora) have not been able to identify any at this
time.
I also need to clarify that Red Hat did not pay for the libjpeg v7 and
v8 API/ABI emulation feature. It was paid for by CamTrace
(http://www.libjpeg-turbo.org/About/Sponsors).
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