Re: [stella] Overscan
Subject: Re: [stella] Overscan|
From: Glenn Saunders <cybpunks@xxxxxxxxxxxxx>
Date: Wed, 21 Jun 2000 18:01:33 -0700
At 07:28 PM 6/21/2000 -0500, you wrote:
I had wondered about that. NTSC is 525 lines, which means 1 frame of 262,
and one frame of _263_.(because of interlacing) I wonder why the atari
manual doesn't recommend doing every other frame with 262 and 263 lines...
The 2600 (as with most game systems until recently) fool the TV into
displaying full-width fields instead of true interlacing. This results in
half the effective vertical resolution but without the interlace
flicker. It doesn't really just display duplicate fields becaue the net
effect is no black space inbetween fields. It's turned into 60fps
I don't understand how it manages to do this, though.
I have noticed that some game architectures did implement full interlace in
their signals, even though they may not have used all the available
resolution. For instance, Popeye in the arcades is pretty flickery. Isn't
that the MIdway system? I think Rampage and others are also flickery.
Anyway, this noninterlaced signal is not standard broadcast NTSC. You
can't (or shouldn't be able to) directly record this to tape or broadcast
it. It needs to go through a frame synchronizer or a time base corrector
to clean it up and resynthesize the interlace. That's what I had to do to
get the screenshots of the 2600 for the documentary, but unfortunately the
TBC interpreted certain fields as "bad video" and held the other fields
which wound up making certain games with flicker never display certain
sprites because these always fell on those fields.
Glenn Saunders - Producer - Cyberpunks Entertainment
Personal homepage: http://www.geocities.com/Hollywood/1698
Cyberpunks Entertainment: http://cyberpunks.uni.cc
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