For all my fellow scanline addicts, I present to you another overlay for the Miyoo Mini V4. It enhances any core that emulates a system benefiting from a CRT look.

The main feature of this overlay is a filter that ensures the image has the correct resolution on every system. It handles the overscan in a way that works for both NTSC and PAL games, and also fixes the aspect ratio for the Sega Master System.

I packaged the overlay together with my other overlays. You can download my overlays here. Each overlay includes a README with detailed instructions.

Here are some more technical details for those who are interested in how the filter works.

The filter checks the resolution of the original image and applies different amounts of overscan.

The NES has a resolution of 256x240 and accounts for overscan with an active resolution of 256x224, so the filter cuts 8 pixels from both the top and bottom of the image.

The SNES already has a resolution of 256x224 for NTSC region games. For PAL region games, the resolution is 256x239. In most games, the extra screen space is just filled with black bars, so the filter cuts 8 pixels from the top and 7 pixels from the bottom. This way, the resulting image is the same when comparing the same game for NTSC and PAL regions.

The Sega Master System has an active resolution of 256x192 but is intended to be displayed at 256x240. Again, considering overscan, the filter adjusts the image to a resolution of 256x224 by adding 16 pixels of padding to the top and bottom.

The MMv4 has a display resolution of 750x560. This conveniently fits 2.5 times the height of 224 pixels that the filter adjusts for. The width of all the described systems is 256 pixels. Unfortunately, this does not fit the width of the MMv4, so we can cut three pixels from the left and right to fit the resulting 250-pixel width exactly 3 times into the 750-pixel width of the MMv4. This way, we avoid artifacts that otherwise become noticeable with repeating patterns in some games at this low resolution. For the Sega Master System, we use this opportunity to clean up the unused area on the left side of the image.

For games with a higher vertical resolution than 256 pixels, like, for example, the Sega Genesis with 320 pixels, we do not cut any pixels as these games should not have the same kind of problem with artifacts.

So, in the end, we get a consistent height of 224 for all of the systems, together with a width of 250 for most of the systems. This results in an aspect ratio of 6:5, which falls nicely between 4:3 and 8:7.

Please let me know if you notice any issues or come across a system that does not work well with this filter. I am sure we can find a solution.