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View topic - Streets Of Rage (GG) emulation glitch in ending sequence

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  • Joined: 12 Jan 2005
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Streets Of Rage (GG) emulation glitch in ending sequence
Post Posted: Sun May 28, 2017 2:38 am
I finished Streets Of Rage for the Game Gear in order to add the credits to the Credits section. I'm using Mekaw (v0.73) because it creates screenshots in the emulated system's native resolution (as opposted to Kega Fusion which creates scaled screenshots).

The problem is a few seconds after starting, one part of the credits shows a solid gray screen where some credits should be displayed. Tried two different ROM files, same result. I've checked a playthrough video and there are some additional credits where I see only a gray screen.

Then I ran the game in Kega Fusion 3.64 and the credits sequence looks fine.

I was unable to test the game with Meka 0.80 because it halts at startup with an error loading cursor_main.tga (the file is present, I downloaded the file from here and it extracted fine, no errors)

I'm attaching the saved state so you can check if the problem is still present with the latest build.

Compare it to the ending as seen in
this video.

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Post Posted: Sun May 28, 2017 10:21 am
Interesting thing, thanks for posting.
It looks like the display flag is disabled for some reason (the screen appears in the tilemap viewer).

> I was unable to test the game with Meka 0.80 because it halts at startup with an error loading cursor_main.tga (the file is present, I downloaded the file from here and it extracted fine, no errors)

Could it be a path related problem? Does your install folder contains accentued character?
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  • Joined: 08 Dec 2005
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Post Posted: Sun May 28, 2017 11:37 am
This is interesting. The grey screen is not being caused by a bug in MEKA, as such, but by the combination of a bug in the game itself and some unfortunate timing. It's quite possible that the grey screen sometimes appears on real hardware.

When the screen goes blank during the ending sequence, the game disables then re-enables the display. Doing each of these requires sending a 2-byte command to the VDP. Unfortunately, the game sends these commands with interrupts enabled. In your particular case, an interrupt occurs in between the 2 bytes of the re-enable command, causing it to be lost.

You can tweak MEKA slightly so that you can see (and take screenshots of) the full credits. Open "meka.nam" in a text editor and find the line:

GG  3d8bcf1d 5AD835BF116EC299   Streets of Rage/NAME_JP=Bare Knuckle/COUNTRY=JP,US,EU/PRODUCT_NO=G-3313,2417

Add "/EMU_IPERIOD=227" to the end, giving:

GG  3d8bcf1d 5AD835BF116EC299   Streets of Rage/NAME_JP=Bare Knuckle/COUNTRY=JP,US,EU/PRODUCT_NO=G-3313,2417/EMU_IPERIOD=227

This will cause interrupts to happen at slightly different times, allowing the "enable display" command to complete correctly.
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Post Posted: Mon May 29, 2017 12:16 pm
RetroSpark wrote
This is interesting. The grey screen is not being caused by a bug in MEKA, as such, but by the combination of a bug in the game itself and some unfortunate timing. It's quite possible that the grey screen sometimes appears on real hardware.

When the screen goes blank during the ending sequence, the game disables then re-enables the display. Doing each of these requires sending a 2-byte command to the VDP. Unfortunately, the game sends these commands with interrupts enabled. In your particular case, an interrupt occurs in between the 2 bytes of the re-enable command, causing it to be lost.


Thanks for the explnation.

RetroSpark wrote
You can tweak MEKA slightly so that you can see (and take screenshots of) the full credits. Open "meka.nam" in a text editor and find the line:

GG  3d8bcf1d 5AD835BF116EC299   Streets of Rage/NAME_JP=Bare Knuckle/COUNTRY=JP,US,EU/PRODUCT_NO=G-3313,2417

Add "/EMU_IPERIOD=227" to the end, giving:

GG  3d8bcf1d 5AD835BF116EC299   Streets of Rage/NAME_JP=Bare Knuckle/COUNTRY=JP,US,EU/PRODUCT_NO=G-3313,2417/EMU_IPERIOD=227

This will cause interrupts to happen at slightly different times, allowing the "enable display" command to complete correctly.


Worked like a charm! Thank you very much!

Bock wrote
Interesting thing, thanks for posting.
It looks like the display flag is disabled for some reason (the screen appears in the tilemap viewer).

> I was unable to test the game with Meka 0.80 because it halts at startup with an error loading cursor_main.tga (the file is present, I downloaded the file from here and it extracted fine, no errors)

Could it be a path related problem? Does your install folder contains accentued character?


Now that you mention it, the path didn't contain accents but it did contain a dot and a space. The path was C:\Meka 0.80.
I changed it to C:\Mekaw080 but still doesn't work.
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