Interlace question.

Thorham · 24 November 2007, 08:37

Good day folks,

Does anyone know how to setup an interlace screen using only the hardware registers? I currently have a 1280x256 ham8 screen up and running, and I want to make this 1280x512. Just setting the interlace bit in bplcon0 seems to be only one step, one would think it would be enough...

Any help is greatly appreciated.

thomas · 24 November 2007, 09:28

You have to double the modulo so that only every second line is displayed and then you have to alternate the memory address every frame. Use the first line for a long frame and the second line for a short frame. I don't remember how to identify a long frame, though.

To do this with the copper only, you can use two copper lists and set the address of the second list at the end of the first one and vice versa.

Thorham · 24 November 2007, 10:14

Sounds good. Thanks

I seem to remember something about this, but only very vaguely.

StrategyGamer · 24 November 2007, 10:27

Are you coding an interlace demo?

Thorham · 24 November 2007, 10:52

It works! Hurray!! There are still some issues, though. But I guess I can fix them (hopefully).

Major thanks to thomas

Thorham · 24 November 2007, 11:00

Quote:

Originally Posted by StrategyGamer

Are you coding an interlace demo?

It's for a bmp viewer example I've coded. I wanted to see how fast a 3x1 pixel shires ham8 24 bit bmp viewer with scaling would be. The program scales down a 24bit bmp to 33%x50% in good quality. I just needed the interlace mode to get the aspect ratio of the display right. It's a good idea, though, however I'm not really a graphics/music guy, so any demo I would make wouldn't really be very cool. Also, my current c2p routine is quite unoptimized so I wouldn't be able to code up anything impressive!

24 November 2007, 08:37	#1
Thorham Computer Nerd Join Date: Sep 2007 Location: Rotterdam/Netherlands Age: 47 Posts: 3,770	Interlace question. Solved! Good day folks, Does anyone know how to setup an interlace screen using only the hardware registers? I currently have a 1280x256 ham8 screen up and running, and I want to make this 1280x512. Just setting the interlace bit in bplcon0 seems to be only one step, one would think it would be enough... Any help is greatly appreciated. Last edited by Thorham; 24 November 2007 at 16:01.

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24 November 2007, 09:28	#2
thomas Registered User Join Date: Jan 2002 Location: Germany Posts: 7,002	You have to double the modulo so that only every second line is displayed and then you have to alternate the memory address every frame. Use the first line for a long frame and the second line for a short frame. I don't remember how to identify a long frame, though. To do this with the copper only, you can use two copper lists and set the address of the second list at the end of the first one and vice versa.

24 November 2007, 10:14	#3
Thorham Computer Nerd Join Date: Sep 2007 Location: Rotterdam/Netherlands Age: 47 Posts: 3,770	Sounds good. Thanks I seem to remember something about this, but only very vaguely.

24 November 2007, 10:27	#4
StrategyGamer Total Chaos AGA is fun! Join Date: Jun 2005 Location: USA Posts: 873	Are you coding an interlace demo?

24 November 2007, 10:52	#5
Thorham Computer Nerd Join Date: Sep 2007 Location: Rotterdam/Netherlands Age: 47 Posts: 3,770	It works! Hurray!! There are still some issues, though. But I guess I can fix them (hopefully). Major thanks to thomas

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