Cheapest (CPU-wise) way to get scanlines

I am running retroarch on a Pandora’s box which uses an Allwinner A13-based board. That is a single 1GHz core arm CPU.

While emulation runs fine on it - I get 60 fps on most platform and games - whenever I try to use any CRT shader, that drops dramatically… to an unplayable “below 15” .

That also happens with the “crt-pi” shader, that as far as know is one of the least taxing shaders.

I wonder if there is any way to get any scanlines on my system or if I am condemned to see the game that ugly on my screen.

Thanks for any clues!

if it can’t even handle crt-pi, you might be stuck using overlay-based effects.

Thank you for your reply.

I am having an hard time realizing how a shader can be more expensive in terms of CPU cycles that emulating a system.

Is there any overlay that you could please recommend to get a scanline effect? Thank you very much,

Shaders run on the GPU rather than the CPU. Overlays are very cheap because they’re just an image that gets drawn over the top.

Look in effects > scanlines. There are quite a few in there for different resolutions and effects, some of which are fancier than just gray/black lines, if that’s what you’re looking for.


Thank you very much for pointing me in this direction.

1 Like

You can also try lowering the resolution. 720p is enough in my opinion.

1 Like

On my GPD XD +, I use the “scanline-fract.glsl” shader which is located in the Scanlines folder. It gets good results on screen and is not heavy at all.

Thanks, but that’s a quad-core 1.4GHz system. Mine is single-core and its clock speed is 1GHz, thus I am afraid it won’t be enough for that either. But I’ll try ASAP.

Scanlines-sine-abs, it’s in scanlines folder. No preset, you will have to pick it in pass 0, and linear, no care.