Re: [stella] PAL Conversion Preferences

Subject: Re: [stella] PAL Conversion Preferences
From: "Eckhard Stolberg" <Eckhard_Stolberg@xxxxxx>
Date: Fri, 15 Nov 2002 14:49:41 +0100
Hello Christopher,

> 99,99% of PAL conversions are done like that. Only issue 
> I think can think of is to get the balance as to *where* 
> adding the additional scannlines, so that the picture is 
> good centered. I'm sure Eckhard can help you with 
> testing that.

If you put 25 extra blank lines into the vertical blank
and 25 lines into the overscan, the picture would be
centered on the PAL TV. But that would also also slow
down the game speed, since your game is now running
with 50 fps instead of 60 fps.

In my experience the vast majority of PAL TVs can handle
a 60 Hz signal, as long as you do a proper sync signal.
Many multistandard TVs can even do a PAL60 mode, where
they use the PAL colours, but stretch the 60 Hz picture
to fill the whole screen. On such a TV the graphics will
have the same aspect ratio as on a NTSC TV. Therefore
I would prefer a PAL60 port of your game. You need to
do an even number of scanlines in every frame though,
or the PAL TV will show incorrect colours or even no
colours at all in the next frame.

As for your SECAM question, I think some of the EbiVision
games have an optional SECAM mode selectable through the
Colour / Black and White switch. The input of this switch
is hardwired to B/W on a SECAM console, although the switch
itself still turns off the colour generation in hardware.
Atari's PAL games also had the colours for B/W mode selected
in such a way that they would look good in SECAM. If you
still have the Colour / B-W switch unused in your game, you
could probably do that too. There aren't too many colours
in Space Invaders, so it should be possible to find usable
matches for SECAM.

I'm not sure how well SECAM handles 60 Hz signals though.
You might have to add the blank scanlines for this mode
to make it work. but if you have a free dificulty switch,
maybe you could add both, a %0 Hz and a 60 Hz mode, to the
PAL/SECAM version.

> (Though - don't go for any color suggestions from him - 
> pick the colors with Stella! :-) )

I'd agree with Manuel on not trusting me with colours,
but as long as you have to use an emulator to chose yourr
PAL colours there is no way to escape my choces. ;-)
The PAL palette in the old versions of Stella is the one
I did for PCAE, and the PAL palette in the current version
of Stella is based on the one we used in the old versions
of z26. So even all three emulators have different PAL
palettes at the moment, they all were partly created by

If Manuel (or anyone else out there) doesn't like the
palettes and thinks he can create a better one, PLEASE do
so. I'd really love to see a proper PAL palette used in
the 2600 emulators. ;-)

> Hm... it probably will look *exactly* the same. I think 
> if you add those 19%, they will rather look *stretched* 
> for us... :-)

No, Christopher is right. Both PAL and NTSC TVs have
an aspect ratio of 4:3. But NTSC displays only 200
scanlines in this area, while PAL display 240 lines.
So if you put a 200 line display centered on a 240
line screen, the picture will look vertically squeezed
compared to the original.

Ciao, Eckhard Stolberg

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