Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!elroy.jpl.nasa.gov!usc!ucselx!crash!hrlaser
From: hrlaser@crash.cts.com (Harv Laser)
Newsgroups: comp.sys.amiga.graphics
Subject: Re: DCTV
Message-ID: <8946@crash.cts.com>
Date: 30 Apr 91 17:05:29 GMT
References: <8909@crash.cts.com>
Organization: Crash TimeSharing, El Cajon, CA
Lines: 50

In article <8909@crash.cts.com> seanc@pro-party.cts.com (Sean Cunningham) writes:
>In-Reply-To: message from es1@cunixb.cc.columbia.edu
>
> 
>The output from the DCTV device is not 24bits, it's 22bits.  However, it
>uses a pallette of 24bits.
> 
>A 24bit image may be manipulated without any degradation to the color
>information stored in the file, and then saved as a full 24bit IFF-ILBM. 
>You just work on a 22bit display, the device doesn't truncate or remap the
>information in the file.

Hi, Sean.  I was hoping what you said in that paragraph above was
true, but up till now I was unable to verify it. Now I am able to verify
it, and it's NOT true, unfortunately.  DCTV *does* induce artifacts
into files, at times, depending on what the original file looked like
and it's relatively easy to prove providing you have some OTHER
extended or "deep color" hardware device on the same Amiga as your
DCTV.  In this case, I have a HAM-E box and DCTV hooked up at the same
time.  

I can create (via many methods - Vista Pro, Imagine, ES300C scanner,
whatever) a clean 24-bit IFF file.  Depending on what's in that file,
when it is brought into DCTV it will often develop a case of "color
crawl" - false rainbows on various small detail areas, like close
parallel lines, metallic clothing, very fine human hair, and etc.
I'm sure you've seen this artifacting. 

Now if I save that file OUT of DCTV as an IFF24-bit save, and look
at both the original save, and the DCTV save when loaded into HAM-E
the latter is most *definitely* not identical to the former.  The 
color crawl that DCTV displayed in its NTSC mode gets saved back
into the file when is saved out of DCTV as IFF24.  Since HAM-E isn't
NTSC it doesn't induce any color crawl of its own (although it does
have some other problems) and it's very easy to see what DCTV has done
to the file while saving it. 

A FireCracker would be a better testbed for the same two files and I
hope to be able to do it that way soon, although something tells me
I won't be able to have an FC, a DCTV and a HAM-E all hooked up to
my 2500 simultaneously.  So far, the latter two are working together
okay and aren't having a slug-fest on my desk :-)

>Sean
> 


  "Half of me wants to knock you out.                       Harv Laser
  Half of me wants to tell you that           {anywhere}!crash!hrlaser
  I'm sorry..."                         American People/Link: CBM*HARV