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From: peterk@cbmger.UUCP (Peter Kittel GERMANY)
Newsgroups: comp.sys.amiga.misc
Subject: Re: The 1/2 line artifact (Was: CBM Support is GREAT!)
Message-ID: <976@cbmger.UUCP>
Date: 19 Mar 91 14:05:00 GMT
References: <1991Mar4.024723.4765@sugar.hackercorp.com> <13397@hubcap.clemson.edu> <19802@cbmvax.commodore.com> <1991Mar13.062558.1013@galois.mit.edu>
Reply-To: peterk@cbmger.UUCP (Peter Kittel GERMANY)
Organization: Commodore Bueromaschinen GmbH, West Germany
Lines: 34

In article <1991Mar13.062558.1013@galois.mit.edu> pselver@euler.mit.edu (Peter Selverstone) writes:
>In article <19802@cbmvax.commodore.com> daveh@cbmvax.commodore.com (Dave Haynie) writes:
>>In article <13397@hubcap.clemson.edu> ddyer@hubcap.clemson.edu (Doug Dyer) writes:
>>>
>>>Hmm.  Does anyone know what C= plans to do about the A3000 problems
>>>(specifically the deinterlacer's flickering black line)?  Is this a bug
>>>that they will fix or is it a feature? 
>>
>>Technically speaking, it's a feature.  Converting a full NTSC frame the way
>>the A3000's Amber chip does it is just guaranteed to give you that flickering
>>1/2 line.  That's an effect of the NTSC standard and the way its different
>>frames get displayed.
>
>No Dave, NTSC has nothing to do with it.  Don't believe everything
>you hear.  An interlaced field has 262.5 horizontal intervals which
>become 525 unique lines at twice frequency.  With a static image
>there is no reason for these lines to change.

Sorry to disagree. One of those fields (let's assume the odd one)
begins with *a half line starting in the middle of the screen*!
It starts at the same height as the 1st line of the other field, so
they interlace perfectly when you imagine them being a little slanted
to the right (vertical deflection causing this). So there is really
only one half line of video data to display. Now this is all valid
for a standard analog TV set.

Hmm, but how is it managed in the Amiga bitplanes? I think I remember
they are built of all full lines, also in interlace.

So, am I puzzled, or what am I?

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