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MAME work and other stuff
December 13, 2015 Haze Categories: General News. 6 Comments on The Value of Videos

One of the most important things we can do as a society is make videos of things, take photos of things, and share them for the world to see, you never quite know when what you’ve done might come in handy, or prove to be the only remaining reference that something once existed, it continues to amaze me how even things that were at one point popular are now difficult to find any visible trace of now.

This is true of arcade games as much as anything else, and I Know when looking at the fruit machine and other non-video games the situation is even worse, sometimes not a single photo of a machine anywhere.

While looking at Mega System 1 it was noted in the source that the game P47 sets some other bits during the Jaleco logo, effect unknown. Luckily, in this instance there was a video on YouTube of P47 booting up. It’s a terrible quality video, but it still gave us an idea of what was missing.

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some kind of trail effect…

I poked around with the code a bit, and have attempted to implement this in MAME.

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I don’t know if this is actually correct, at the point where they want the trails to vanish they adjust a parameter, the original video isn’t really clear enough to show how the trails are removed, so I’ve had to guess. If anybody has a P47 PCB and can record a better quality video it would be appreciated, the one on YouTube was more useful than the original poster probably ever thought it would be, but not really good enough to say my emulation is correct :-)


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Felt the need to join all the people giving you and Kale a big thanks for looking into Mega System 1 after all this time. I thought it was really hopeless at this point. And Kale even dare to fix a GX-System issue, no less. So thank you once and again. Too bad I can’t help you with the P-47 question, but after reading your previous post on the game and Shingen, I was wondering if the missing effect could be related to Rod-Land’s palette (?) issues, which are there from the beginning and are too ugly to be normal behaviour.

I’m meaning this: https://www.youtube.com/watch?v=IW-y2nHBZpU Check the color transitions at 4:06 (the background through the wall hole) and 4:53, for instance.

Not in MAME Testers I guess for not being too intrusive, but I don’t remember them being on the arcades and it’s similar to CPS2′ issues with Shadow over Mystara and Street Fighter Apha 2’s background transitions, for instance (pic of the latter: http://s27.postimg.org/pm86kb1wz/mamesfz2.png ), again, not in MAME Testers for some reason.

The color transitions are a timing thing, we’ve actually seen plenty of hardware where that DOES happen on the real PCBs due to shoddy programming tho, just because something looks ugly doesn’t mean it’s a bug..

I don’t know if
is a MAME vid of a PCB vid but you can see the exact same ‘ugly fade’ at around 2:14 in it
trying to find a more solid PCB reference..

has it too, again can’t say for sure it’s not emulation, but the video quality looks more like capture board than MAME to me.

all I can really say is that this kind of glitch is common on real games, as are one frame glitches like the D&D one you posted, without good evidence it’s hard to say either is bug.

Thanks for the answer. The Retronauts video is most likely from MAME but the Nico-Nico one seems indeed from capture hardware. I don’t know. Can’t find any video from the PCB even in Nico-Nico, either. Maybe if it were in MAME Testers as a possible bug someone with the PCB could verify; it’s a pretty common board after all.

As for the CPS2 glitches, those are easier since they’re more modern and well-known games:

Background transition glitch on MAME: https://youtu.be/cFZLsfhw4m0?t=91
Video of the PCB: https://youtu.be/tn1KM4GizRc?t=71
Another: https://www.youtube.com/watch?v=G49bbLkc2qE

It’s a one-frame glitch which happens in Street Fighter Alpha 2 (and clones) in every transition from the “next rival” screen to the stage screen.

Shadow over Mystara, transition from the title screen to the select player screen:

MAME: https://youtu.be/2qUJ8z57mDk?t=7
PCB: https://youtu.be/INiHPiPb8aU?t=71

The characters’ fade-in is not perfect on the PCB either but I’d say on MAME is much worse. The glitch also affected the background transitions when you pass through doors in the Tower (later stages), but can’t find a video with it right now. Most likely, other games are affected too, since never checked it too deeply.

Speaking of videos and title screens, Andy Welburn posted a video of his Tunnel Hunt PCB, with the title screen logo effect intact. It’d be neat to see this fixed in MAME, as small of a detail that it is…


just looks like the image should wrap around when compressed, while right now MAME only draws a single copy of it, not really sure why I’m credited in the driver tho, don’t recognize a single line of that code as my own.

“I don’t know if this is actually correct” — well, the effect still looks wrong compared to the video. On the video, the trails turn into the chains of diamond-shaped rectangles at the very last moment, then just disappear, while the emulation video doesn’t have the “chain effect” at all + the trails there disappear not immediately, but by shortening their lengths.

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