P3D Re: JPS format images

[Brian Reynolds <reynolds@xxxxxxxxx>]

I'd like to thank Jon for graciously answers some of my points.  Just
so there are no mistakes, this is based on a pet peeve of mine, and I
don't expect others to find it rational or "right".

jon siragusa wrote:
> Brian Reynolds wrote:
> >
> >This runs into a (non-stereo) pet peeve of mine.  Has whoever created
> >the JPS *proposal* submitted it to the JPEG standards committee (or
> >any of the other relevant committees, perhaps the W3 Consortium) and
> >had it approved as part of the JPEG standard?  Just because a company
> >comes up with a product that uses a new file format does not make that
> >file format a standard.  Standards must be openly available and openly
> >agreed upon.  (Yuck!  I hate the word "open" since the marketdriods
> >started abusing it.)
> >
> 
> No, the JPS information has not been submitted to the JPEG standards
> committee.  JPS is not really a new image format.  As you know its
> simply an extension of JPEG (an extension of which the JPEG committee
> probably wouldn't care about).  However, the JPEG standard clearly 
> defines user defined fields (called markers) by which a 3rd party can 
> store information. This is where the Stereo Descriptor is stored.  
> Adobe Photoshop stores some of its information in a marker when it 
> saves a JPEG.
> 

Good.  I hadn't realized that JPEG bother to allow for extensions.

> The documentation for the Stereoscopic Descriptor is freely (can't 
> exactly say that for the JPEG spec.) downloadable from:
> 
>         http://www.vrex.com/developer/sterdesc.zip
> 

Cool.  Unfortunately it is a MS Word document.  An ASCII, HTML,
Postscript or Acrobat version would be greatly appreciated.

When I said "freely available" I did not mean "available for no fee".
Many of the standards bodies fund their work by selling printed copies
of their standards.  That's OK.  TANSTAAFL

By the way, the README file for the Independent JPEG Group's libjpeg
sources has a list of files online and books documenting JPEG, and
gives the ITU/ISO document number for those who want and officially
sanctioned version.

> While the specifications for the Descriptor were not openly discussed,
> they were discussed with people from VRex, NuVision, Stereographics
> and Chasm Graphics (i.e. a group quite knowledgable with respects to
> digital 3D).  What resulted is a specification that is quite general
> (perhaps too general?) and does the job with room to expand to any 
> future needs.  If, after reading the Stereoscopic Descriptor spec,
> you feel there is something that should be changed or added please let
> know via private email.
> 

That seems to be pretty heavy on the PC hardware side of things.  It
would have been nice if folks like the IJG had been consulted.  It
can't hurt to have a widely available implementation of JPEG handle at
least some of the features of JPS.

> >Until this [open standards] happens I don't think we'll ever see JPS
> > support on other platforms, or in mainstream (e.g., Photoshop) software.
> >
> 
> There is nothing stopping anyone who is knowledgable in any programming
> language to write a JPS reader/writer for other platforms.  JPEG is
> a cross-platform file format.  The Stereoscopic Descriptor, being 
> basically a set of flags, is cross-platform.  There is no "standard" 
> for an anaglyph or interleaved JPEG is there?  
> 

Depending on how hard it is (and if I can get a readable version of
the JPS specification), I might try such an implementation (probably
only for reading a JPS file and outputting anaglyph, and parallel and
cross eyed pairs).

By the way, the JPEG standard doesn't specify a file format.  That's
one of its short comings.  An upcoming version will specify SPIFF,
which is supposed to be interoperable with JFIF (the current de facto
standard).

> Hope this helps,
> jon

Yeap.  Thanks.

-- 
Brian Reynolds     | "Dee Dee!  Don't touch that button!"
reynolds@xxxxxxxxx | "Oooh!"
NAR# 54438         |    -- Dexter and Dee Dee
                   |       "Dexter's Laboratory"


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