Note: if you implement my GPU Hard Sync tweaks from https://retropie.org.uk/forum/topic/27431/howto-major-performance-boost-on-retroarch-based-emulators you'll need to keep both shaders and bilinear filtering disabled.

This is great info even for those of us who are not using standard HD video resolutions. Anyone building an arcade cabinet using dirt cheap 17 or 19-inch LCDs typically find them running 1280x1024 resolution, and although 1024p is not 1080p, it's certainly better than 720, and I can definitely attest to how nice the CRT-PI shader looks at 1024.

It's also handy to know that the shader looks best when it has 4x game resolution to render the scanline and shadow mask effects. This has come up in a few other threads over the past few months--people building hand-held devices that have tiny screens sometimes ask about using the CRT-PI shader. I had always thought you would need extra pixels to make the CRT effect look nice. I guess my advice was sound. Good info all around.

@Ashpool said in Can't get retropie 4.1 to boot in 720p:

. Is it possible to activate such a function here (please ignore if this forum actually is already warning the user about it) ?

It is activated, but the warning was probably shown to @RickyTan, your reply was later.

I have had to add the line video_shader_enable = "true" to the emulators I want the shader to work in as well. I may not be doing it right, but I don't use shaders on all emulators, so I just use the line in the individual configs to enable it. I did find out the other day that I need to configure the settings within the in-game retro arch config for scaling and nearest vs linear too or else the default to "don't care" and don't look the way I want them to.