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Pixel Garbage in Wolfchild (Sega CD) #356

Closed GoogleCodeExporter closed 9 years ago

GoogleCodeExporter commented 9 years ago 
What steps will reproduce the problem?
1. at the beginning of level 1 just jump right at the beginning and you'll see 
a pixel garbage line at the top of the screen, which wasn't there before.

What version of the emulator are you using (official, SVN revision,...)?

the latest version that comes with retroarch 0.9.9.4

Please provide any additional information below (Emulator settings, Console
setting,...)

playing on OUYA, Game is NTSC

Original issue reported on code.google.com by gora.pat...@gmail.com on 9 Aug 2013 at 5:23

GoogleCodeExporter commented 9 years ago 
seems only to affect the US Version, as everything is fine with my PAL Version.

Original comment by gora.pat...@gmail.com on 10 Aug 2013 at 12:21

GoogleCodeExporter commented 9 years ago 
by "which wasn't there before", do you mean that the bug did not occur in a 
previous version of the emulator ?

Original comment by ekeeke31@gmail.com on 16 Aug 2013 at 12:29

GoogleCodeExporter commented 9 years ago 
yup, at least i didn't recognized it.

Original comment by gora.pat...@gmail.com on 16 Aug 2013 at 8:50

GoogleCodeExporter commented 9 years ago 
I just checked and :

1) it's not constantly happening when you jump, most of the time but not always 
so it's easy not to notice it

2) it only happens in that part, when standing on the top platform 

3) it happens in Fusion / Gens too 

From debugging, when jumping, the game do some VRAM updates during active 
screen, which is the cause of the pixel garbage. 

It's probably a bug in original game with the way scrolling is handled at the 
top of the screen (only seen when jumping from the top platform at the start) 
and most likely happens on real hardware as well (if it was caused by emlator 
inaccuracy, you would have an entire line of garbage, not a bunch of pixels).

It does not happen on PAL system because VBLANK has more time and those extra 
VRAM writes are completed before active display starts.

Original comment by ekeeke31@gmail.com on 20 Aug 2013 at 8:32