Overlay distortion on Raspberry Pi

Libretro Lakka
#1

Hello all.

I have been trying to use a grid overlay I put together for Game Boy. It consists of a grid of gray lines with transparency to simulate the LCD effect. The way it appears on Retroarch PC (Linux and Windows) is this, if you zoom in it is pixel perfect and the lines blend perfectly with the background:

PC
PC.png800×720 19.9 KB

However, on the Raspberry Pi there is some unnecessary scaling being done for some reason (resolution and overlay are both 1280x720) and it introduces distortion, which can be seen here (notice the diagonal line, also grid is not perfectly 1 px and it is visible in the background):

Raspberry%20Pi
Raspberry Pi.png800×720 54.5 KB

Is there any way to fix this? I think it is GPU related, I have tested with overscan disabled and the result is the same.

#2

Yeah, there’s definitely something weird going on with overlays on RPi. We had to have separate scanline overlays just for RPi for that reason.

#3

Thanks for the reply.

I also noticed weirdness with the ‘sharp-bilinear-simple’ shader on the Pi. With integer scale ON and aspect ratio 1:1 the shader should not have an effect, however on the Pi with the shader on there is blurriness added to the image. On PC the image stays sharp (as expected).