How to addapt the crt-pi shader to 720x576@50 Hz resolution under XU4?

Libretro Lakka
#1

I have grabbed the crt-pi shader from this repo and it works very well on the XU4 under the RC3 of lakka compared to the version which was originally implemented in RC3.

Which parameters of the crt-pi shader do I have to play with in order to adapt this shader to my resolution of 720x576@50 Hz? The scanlines of the crt-pi shader @720x576 are not in regular intervals…

PS Here are my modifications of the boot.ini file for the XU4 SBC:

setenv video_output “video=HDMI-A-1:720x576@50”

setenv governor “performance”

setenv bootargs “${console} ${video_output} ${governor} ${bootrootfs} ${openelec} smsc95xx.macaddr=${macaddr}”

#2

576 isn’t enough to get good looking scanlines. crt-pi really needs about 4x the game’s vertical resolution to get good looking scanlines without integer scaling and below that I recommend integer scaling. Even with integer scaling 576 is an awkward height. It’s too low for 3x (if you try overscanning and clipping you likely cut too much of the game) but if you use 2x you will have huge borders.

Other shaders are better at scanlines with low resolutions - they can put more effort into it but crt-pi is limited by the need to be fast on Raspberry Pis.

#3

Thanks for your quick respond.

I"ve made today a custom scanlines overlay under Inkscape for the 720x576 resolution and it looks really good!!

#4

You can edit crt-pi.glsl file in text editor to turn off scanlines. Find line:

#define SCANLINES

add two slashes in front of it:

//#define SCANLINES

and save.

Now you can use this shader (which is very good) and your overlay with scanlines, and all will look very nice.

Works good to me on Android and without integer scale.