P3D Re: JPG and destruction

[roberts@xxxxxxxxxxxxxxxxx (John W Roberts)]

>Date: Tue, 21 Apr 1998 18:36:20 -0600
>From: Ole Hansen <oha@xxxxxxxxxx>
>Subject: P3D JPG and destruction

>> ....The effect of JPEG coding scheme on the perceived quality of 3-D
>> images was investigated by using the CCIR subjective assessment method.
>> Lossy compression affected the quality of 3-D image pairs less than
>> that of 2-D images of the same scene....

>So much for chineese science. 

I don't think it's appropriate to instantly dismiss something like this
without a fair hearing. This apparently instant dismissal of a claim has
the appearance of itself being *bad science*.

Ole wrote in a reply to Boris:
>I just commented on the scientific level of this particular mail. I guess, 
>that you are aware of the fact, that scientiest are employed to improve 
>their own, and later yours and my knowledge, and not to promote ignorance?

Unless you've read their paper or have direct knowledge of their work, I
don't see how you can be considered qualified to judge the scientific
level of the paper. If you are implying that we don't need to read the paper,
that we already know everything we need to know, it seems to me that you're
the one who is promoting ignorance (ignorance of the work of these 
researchers, which may or may not provide valuable insight). SID has a
stringent review process, and the acceptance of this paper indicates that
the authors were able to convince at least several people knowledgeable in
the field that the paper was worth presenting. I think it would be worthwhile
to find out what the authors have to say.

You are able to provide examples which you say indicate that there is a
problem with JPEG compression. Even supposing that's correct, it doesn't
automatically mean that anyone else using JPEG will have the same degree
of problems. Tom Deering noted possible causes for the problems you had.

One can imagine the announcement of the discovery of superconductivity, 
and a skeptical scientist saying "Nonsense! I have a piece of wire in 
my laboratory, and it has normal resistance, so zero-resistance 
is not possible!", without waiting to find out the conditions 
under which superconductivity was obtained. Similarly, I think 
it would be appropriate to wait to find out the conditions and
test methods of this experiment and read the full paper to find out
exactly what is being claimed, before making a judgement on this paper.

On the other hand, premature announcements several years ago on a 
breakthrough in low temperature hydrogen fusion illustrate that a research 
claim should not be automatically accepted - there is a proper balance 
between willingness to listen and need to be convinced, that is optimum for 
the progress of science.

In the case of the paper by the researchers from China, I would be
interested in knowing the methods used, particularly the subjective
evaluation technique that was mentioned in the abstract. Note that the
comparison was between compressed 2D images and compressed 3D images,
not between compressed 3D images and uncompressed 3D images.

>Anyone wanting to see the destructive
>habits of JPG to stereograms (anaglyphs) are invited to visit:
>http://hjem.get2net.dk/stereoskopklubben

I saw the images, but didn't have anaglyph glasses available, and I did
not see the PNG versions for comparison.

As we discussed a few days ago, if JPEG affects color, perhaps this is a
particular problem for anaglyphs, and perhaps side-by-side JPEG images
would not be as bad.

Again note: examples show that there *can be* a problem, but they don't
show that there *must always be* a problem.

>Is there a browser where you can import PNG ?

You might be able to get a "plug-in" program for the regular browsers.
But everybody who wanted to view them would have to get the plug-in.

John R


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