Vertical bands in Super Mario Kart with 5x and MG shadow mask

[Dafoof]

Hi,

I've found settings that I think look fantastic with the new video processing system, in 1080p. In addition to setting the cores (tested SNES, MD, TG16, NES, NeoGeo) to 5x scaling, here are the options I use:

mkart2.jpg (771.12 KiB) Viewed 5607 times

It looks glorious with all games I have tried so far... but one: with the SNES core and Mario Kart in particular, I have noticed a strange artifact, on the first track, in regions of the image that are supposed to be solid gray. Lighter vertical bands appear, and move across the screen following track rotation movement. Below is a screenshot of how the issue appears, within the red box, but it is probably easier to see it by yourself if you can reproduce it (and please ignore the Moire aliasing pattern, this is just due to rescaling of the screenshot).

mkart1.jpg (267.75 KiB) Viewed 5607 times

In my case, I use integer vertical scale (5x, as prev. mentioned) and not horizontal; but I checked, and even when forcing integer horizontal scale, the issue persists. I also tried default scanlines instead of the bright version, same thing. However, the problem doesn't appear with shadow masks other than the Magenta Green Stripes one (at least among the ones I have tried, including all from the root masks directory), so not sure what is specific to that mask that would cause such issues on constant color areas (look amazing otherwise, though!).

Thanks,

[daveo]

Sometimes your TV can be doing extra scaling that'll impact the picture. I found on my LG OLED C1 I had to turn on 'Just Scan' in the Aspect Ratio settings.

[NML32]

Sometimes your TV can be doing extra scaling that'll impact the picture. I found on my LG OLED C1 I had to turn on 'Just Scan' in the Aspect Ratio settings.

I thought I had to turn off "Just Scan" on my 1080p Samsung TV.
Are there any settings needed in the MiSTer.ini?

[Dafoof]

I tried changing the all potentially relevant picture settings of my 1080p Samsung TV (which was in game mode already), to no avail. I don't have anything that would correspond to this "Just Scan" option. But given in what conditions this artefact appears, I'd be surprised if it is caused by the TV.

Upon further investigation, I noticed that:
1/ The artefact appears with all (and only) magenta-green mask variants.
2/ It is visible no matter what horizontal and vertical filter you pick in video processing options, including none at all. As a matter of fact, it is at its most visible when you don't use horiz/vert filters and default to nearest neighbor filtering.
3/ The issue actually only appears when using the 5X vertical crop mode of the SNES core: when using "normal" scaling (which, given my .ini, stretches the image to the screen, with non-integer scaling), or vertical-integer scaling (4X), the artefact disappears. Could it be that the magenta-green family of masks doesn't upscale properly? What resolution has it been optimized for?

Btw, is there any other place where this issue could be reported? What would be the most relevant github repo?
Thanks,

[Yim]

Maybe it’s not the TV, but the menu option on my 1080p Samsung that I think corresponds to “just scan” is menu->picture->picture options->size->screen fit

If the size is set to screen fit then it will display the full 1080p signal. Otherwise it upscales slightly and part of the image gets cut off. Dunno if that’s your problem here, but I found it worth setting anyway if you haven’t got it already.

[Dafoof]

Oh I see, no, it'd definitely not that.

[Asteld]

Is it a 4K TV? Because no matter what, a TV will never use integer scaling. The Manufacturers don't like it. In addition, there are many many configurable and unconfigurable filters and whatnot used by the television in order to create the Good Looking image. It's a safe guess that most of those filter do not consider image 'deconstruction' filters such as scanlines or shadow masks. TV's definitely don't show an objective image, especially when first scaling the image to full screen. And of course, all those filters might create unexpected results such as the above.

Try setting the Shadow Mask to 2X, just to see if that still causes issues. You can also try RGB lines which are just 1 pixel wider then MG. You can also try the mask below, which is 2 pixels wide just like magenta green. Most likely it is scaling issues exclusive to your TV model and you'll have to ignore the artifcats or try another filter.

You can try this one:

Code: Select all

v2

2,1

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[Dafoof]

Thanks for the details, Asteld. I deactivated all options that would sound suspicious (those "consumer friendly" names like "magic black" and such nonsense are really annoying, wish they were more upfront about what those do...), but no dice.
After the latest update, the old masks are gone, and I noticed that the new line of MG masks do not generate such visible artefacts anymore (on the other hand, the new "Sony PVM" one generate massive ones, at 1x. At 2x, all masks I've tested seem to work fine.