Re: Changing the frequency of games to sync to movie cameras...

On Sat, 02 May 2009 22:04:02 -0700, you wrote:

>Can the monitor adjust down enough to still show a picture without rolling?
>
>The horizontal frequency will also shift downwards of course... 24:30 =
>5/6ths as fast - about 1300kHz

        You're opening a huge can of worms here, really... :) The short and
simple answer, though, is "no, it probably will not work." Among the
pitfalls you're likely to encounter:

* Changing the CPU's clock crystal may not do anything to the video signal
at all. Many raster-video systems, especially older "classics" that use
the same H/V frequencies as NTSC television (or are, in fact, designed to
be connected to NTSC TVs!) derive the horizontal & vertical timing from a
separate crystal, because it's relatively easy to derive those frequencies
from the 3.579545MHz NTSC color-subcarrier frequency.

* Most, if not all, classic-era gaming monitors are fixed-frequency
designs; 15KHz horizontal, 60Hz vertical, and that's all they will ever do.
They're not like computer monitors; they can't "adjust down" (or up, for
that matter.) In fact, even a lot of modern games still use
fixed-frequency designs; they're simpler and more robust.

* Changing the CPU crystal might not just slow down the game; depending on
the design, it might also cause timing problems or "race" conditions
between different sections. (This is probably more likely on multi-CPU
designs.)

        The TV sets they use in film production are specially designed to
convert 30Hz NTSC to 24Hz film by, essentially, dropping one frame in 5 --
which isn't as simple as it sounds when you're dealing with a "live",
real-time video feed.

        How "WarGames" overcame this, I'm not sure. (Although I do seem to
recall they talked about it on the commentary track, so maybe you could try
renting the movie some weekend and see if they give you any helpful ideas.
:) ) Unless you've got the bucks to buy or rent some of that specialized
video-to-film gear, though, Chris's suggestion of sticking an LCD monitor
inside the cabinet may be your simplest "on-the-cheap" option.

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solarfox@removethis.triluminary.net (Gary Akins jr.)
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Received on Sun May 3 10:24:46 2009