[nSLUG] jpeg7: "you are in delusion"

George N. White III gnwiii at gmail.com
Sat Aug 8 16:53:00 ADT 2009


On Sat, Aug 8, 2009 at 2:52 PM, Daniel Morrison<draker at gmail.com> wrote:
> Hey George,
>
> A little bit "stream of consciousness" writing here... not quite sure
> what you're getting at!
>
> 2009/8/8 George N. White III <gnwiii at gmail.com>:
>>  From the README for jpeg7:
>> If you think that you know about DCT-based JPEG after reading this book,
>> then you are in delusion.  The real fundamentals and corresponding potential
>> of DCT-based JPEG are not publicly known so far, and that is the reason for
>> all the mistaken developments taking place in the image coding domain.
>
> I don't have any reason to disrespect these folks, but... the
> fundamentals of DCT-based JPEG are not publicly known? Really? After
> almost 20 years of a phenomenally successful published standard? And
> these free-software coders are keeping the knowledge secret
> because...? Sounds to me like the README author has a little chip on
> his/her shoulder...

Well, the information at jpegclub.org indicates the IJC people will be adding
support for images that don't compress well or have artifacts using jpeg6 or 7.

>> Why was I looking at the jpeg7 README?
>
> Yes indeed, why?
>
>> I use hdfview, which is a java app that uses hdf-java.  For some combinations
>> of hdf files and linux distros, the program throws an exception in libc.  The
>> developers at hdfgroup.org have not been able to reproduce the problem,
>> but have complaints from two users working with files from different NASA
>> sponsors, and hdfgroup.org is largely funded by NASA.
>>
>> To build hdf-java, I need PIC code in libjava.a, but Ubuntu does not build
>> the .a library with PIC.  I did try linking with the .so files, but
>> then I get the
>> error even on Ubuntu 9.04 amd_64, which is a platform that works with the
>> hdfgroup.org binaries (I think they are built on RHEL).
>
> Disconnect here -- hdf-java needs PIC libjava.a, and so... you start
> with jpeg6b sources.

I did, but the "official" sources don't have linux amd_64 configs, so it was
easier to use jpeg7.

> I confess I have no idea what hdf-java is, but you might help us
> establish the link... how are you getting to the jpeg sources based on
> a need for libjava.a?

HDF is a standard format used by NASA.  There is a Java JNI version,
called hdf-java, that uses a libjhdf.so.  The Makefile for libjhdf.so
links to explicit libXX.a for a wack of XX's, which requires that all the
libXX.a's be built with PIC.

>> I started with the official jpeg6b sources, but the available configurations
>> predate amd_64, so it would be a non-trivial task to prepare a new
>> config, so now I looking at jpeg7.
>>
>> And just which developments might those be?  Inquiring minds want to know.
>
> What developments are you talking about? You're losing me here... From
> jpeg6b -> jpeg7? Well, there are a number of new features listed on
> the page that you referenced in your previous email...
> http://jpegclub.org/
>
> Hope this helps,

Well, it was simple to build jpeg7, and it is supposed to be "not worse" than
jpeg6.  My new version of hdf-java still doesn't work.  The problem files don't
use any compression, so even if there are bugs in jpeg7 I doubt that is the
reason hdf-java is failing.

-- 
George N. White III <aa056 at chebucto.ns.ca>
Head of St. Margarets Bay, Nova Scotia



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