Re: [stella] PAL/NTSC issues

Subject: Re: [stella] PAL/NTSC issues
From: Piero Cavina <p.cavina@xxxxxxxxxxxxx>
Date: Sun, 17 May 1998 17:33:28 +0200
At 11.55 15/05/98 -0700, Chris Wilkson wrote:

>I think this was all discussed before, but I'll mention this one item.  If
>you want to include the option for any format, simply latch the value of
>a console switch.  You still use extra ROM and 2 bits of RAM
(PAL/NTSC/SECAM),
>but you don't lose a switch in the process.
>
>Piero, how did you do this in Oystron?  And how costly was it?

Easy... for vblank and overscan, I set the internal timer with the right
values taken from a table, according to the position of the switch. Also,
the kernel does about 36 extra scanlines when the switch is set to PAL.
As for the colors... I've choosen a set of colors that looks decent in both
versions... another solution in "2600 style" he he :)
Then there would be all the timings. This is the big problem for an
accurate conversion, which think it is almost impossible for most games,
unless you use 16-bith math for almost everything...

BTW, I haven't yet found a PAL tv which can't sync to the NTSC version of
Oystron, so this feature could be considered useless.. but it's great fun
to switch the mode on the fly, and see the TV lose sync for a couple of
seconds... :-)


Ciao,
 P.


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