The Abduction of Oscar Z on a real CPC

Started by mikezt, 19:33, 02 May 21

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mikezt

Hello!
I'm trying to play Abduction of Oscar Z on a real CPC, but the picture is very wrong. Look at the attachment. Why is this happening? Is it because of the wrong CRCT type?
Cheers,mike/zeroteam

roudoudou

Quote from: mikezt on 19:33, 02 May 21
Hello!
I'm trying to play Abduction of Oscar Z on a real CPC, but the picture is very wrong. Look at the attachment. Why is this happening? Is it because of the wrong CRCT type?
Cheers,mike/zeroteam
because this is not a cathodic screen, there is sync issues
use RASM, the best assembler ever made :p

I will survive

XeNoMoRPH

yes, it is a bug already reported, @tulinmola promised to fix it, but the fix is ​​not posted yet

on the other side, @CyrilAmstrad , He also has a corrected version available, but it is not yet published:



https://youtu.be/kHq44o0-dg0
your amstrad news source in spanish language : https://auamstrad.es

tulinmola

Hi all, here Tulo!


Yes, I'm fully aware of the sync bug. As @XeNoMoRPH said there will be a fix for this (with other minor changes/fixes). And it will be available as soon as I can steal some time to my real life. I hope it to be sooner than later!


Cheers!

mikezt

Hi tulinmola!
That's good news and don't worry, I know the problem with free time. I'm looking forward to play it on a real hw.

jesusdelmas

Hello all!


Any news about the fix version??

Rhino

Quote from: tulinmola on 14:34, 03 May 21
Hi all, here Tulo!


Yes, I'm fully aware of the sync bug. As @XeNoMoRPH said there will be a fix for this (with other minor changes/fixes). And it will be available as soon as I can steal some time to my real life. I hope it to be sooner than later!


Cheers!
Hey @tulinmola , congrats on the game! It's really beautiful and a genre that doesn't have a lot of good games on CPC so it's even more appreciated.  :)

About the sync bug, I debugged the code and I think I found where you have the problem.

I saw that you use the same screen configuration of the Mario demo I made and the code you use to configure the screen is basically the same I wrote for that demo but with a modification that causes the desync:

In the third interrupt, when CRTC register 9 is set to 7 to make the character 8 pixels height again, it is done prematurely, when still VCC=#14 and VLC=#01, and as a consequence the character #14 becomes 8 pixels high instead of the 2 pixels it should be, because the rest of the code is set to generate a 50Hz signal (or 312 scanlines) only if that character is 2 pixels high. That little timing mismatch is producing extra scanlines and a signal a bit slower than the PAL standard and that's why it doesn't sync well on monitors with low tolerance to frequency mismatches. To fix it, just set register 9 to 7 about 20 cycles later, just like in the Mario demo.

Also keep in mind that fixing it will take a few hundred cycles per frame and if you're on the speed limit to keep the game's refresh rate you may need to do some additional speed optimisation, although I hope that's not the case.

Then, in the second interrupt I think there may be another possible issue because register 9 is set to 1 at the very beginning of the first line of the character and, although it may work, on not very accurate emulators it could fail unnecessarily. Although I don't know if you need this modification to have a bigger delay margin in the interrupt but, if this is not the case and you always have the interrupts enabled, it would be better to do it a few cycles later for better stability/compatibility.

And that's all! I hope this will help you to get the fix out soon, as I think there are many people waiting to have your great game fixed!

Regards!



TotO

Has the desync display bug on a real CPC has been fixed?
If yes, where it is possible to download it? Thank you!
"You make one mistake in your life and the internet will never let you live it down" (Keith Goodyer)

TotO

"You make one mistake in your life and the internet will never let you live it down" (Keith Goodyer)

XeNoMoRPH

With the resurgence of the post, I decided to talk to @tulinmola again, on November 14, he told me that he would answer all the messages as soon as he could.
your amstrad news source in spanish language : https://auamstrad.es

TotO

Thank you.

Can be nice, as this game is not playable on a real CPC since a year for some users. :)
"You make one mistake in your life and the internet will never let you live it down" (Keith Goodyer)

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