Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!julius.cs.uiuc.edu!psuvax1!rutgers!cbmvax!cbmehq!cbmger!peterk
From: peterk@cbmger.UUCP (Peter Kittel GERMANY)
Newsgroups: comp.sys.amiga
Subject: Re: Commodore De-interlacer
Message-ID: <565@cbmger.UUCP>
Date: 6 Nov 90 08:48:54 GMT
References: <5463@crash.cts.com> <239@mohawk.cs.utexas.edu>
Reply-To: peterk@cbmger.UUCP (Peter Kittel GERMANY)
Organization: Commodore Bueromaschinen GmbH, West Germany
Lines: 31


  In article <239@mohawk.cs.utexas.edu> bryan@cs.utexas.edu writes:
> (about the flickering first half line)
>	Every time this subject comes up, I ask why the C-A deinterlacer can't
>handle the first scan line in whatever way the flickerFixer does.  I've never
>seen any answer to this.  I'd just like to know whether the problem is due to a
>design or manufacturing error, or is the deliberate result of some cos

>reduction measure.
  In either case, is it with us forever?

It has already been answered by one of the chip guys. The reason is the
definition of an interlaced TV screen where the Amiga sticks to. In this
norm one half picture starts in the upper left, but the other half picture
starts with a half line at the top in the middle. And they obviously did
their best to manage this also on the Amiga.
So the question arises: What does flickerFixer put in there?

To get an understanding for this half line, you must imagine that during
a horizontal scan the vertical scan already and also is running, but
much slower. So all lines are bent a little downwards (if you don't
twist the tube). So for the second half picture to match perfectly
inbetween the lines of the first half, they (TV norm definers) chose to
start at the very top but offset by half a line horizontally. When you
draw this on paper you will see, that this way you get a perfect
interlacing of the two half pictures. And Amiga is dedicated to follow
TV norms.

-- 
Best regards, Dr. Peter Kittel  // E-Mail to  \\  Only my personal opinions... 
Commodore Frankfurt, Germany  \X/ {uunet|pyramid|rutgers}!cbmvax!cbmger!peterk