[stella] More on NTSC - PAL converting

Subject: [stella] More on NTSC - PAL converting
From: Eckhard_Stolberg@xxxxxxxxxxxxxxxxxxxxx (Eckhard Stolberg)
Date: Thu, 20 Mar 1997 16:55:29 +0100
Hello there, 

a while back I have written a little NTSC - PAL guide. I have checked this
subject a little further and I think it is a lot easyer than I thought.

This post should have attatched a ZIP file with three little test programs
in it. 

The first one, PALLINES.BIN, is for the loss of colour problem, some games
have in PAL. I thought it was because of a wrong overall lines/Vblank lines 
ratio, but I was wrong. It seems that a program looses its colour signal only
when it is doing an odd number of overall lines. It has no problem, if it
does a even number of lines. To test this the PALLINES program allows you
to change the number of overscan lines by moving the joystick up and down.
It should display a blue background when the number of lines is even and
loose the colour when the number is odd.

The second one, TIME.BIN, is for the different refresh rates in PAL and NTSC
which would cause the game to run at different speeds. The TIME program 
uses 262 lines, like a NTSC game and displays a clock. The seconds get 
increased every 60th frame. You can reset the timer by pressing the joystick
button. I ran it on my PAL VCS and is seems, that the clock almost runs 
acurately.

So to have your NTSC game display and play correctly on a PAL system it should:

produce 262 or any even number of lines,
make 3 of theese lines Vsync lines,
and turn Vblank on in the overscan lines, because they would be still visible 
on the screen on PAL TVs.

The only problem is the different colours. I asked you the last time to correct
my description of the PAL colours, but got no response. Therefore I wrote 
this little colour test program, COLOUR.BIN. It displays the current colour
and its hexvalue in white and in black on the top of the screen. On the bottom
of the screen it displays the current hue in all 8 luminances on the left
and the current luminance in all 16 hues on the right. By moving the stick
up and down you can change the hue, by moving it left and right you can change
the luminance. When the button is pressed all 128 colours are displayed on
the screen with the current colour in the background.

Can EVERYONE with a PAL system PLEASE run this program and send me discriptive
names for all of the 16 hues, so I can see if mine were correct?

BTW all programs use only 262 lines, so they can also be used on NTSC systems,
but I don't think they are very usefull there.


Thanks, Eckhard Stolberg

Attachment: PALTEST.ZIP
Description: Binary data

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