[Feature Request] Super Resolution

Hello,

Any chance you'd implement a super resolution option in RetroArch?

Basically, allowing to use a bigger framebuffer than the native display resolution, for instance 2x ect. that would be then downscaled to native using a simple bilinear filter.

This would greatly improve the CRT shaders quality. For instance on a 4K TV the CRT Royale shader looks great for sources around 320x240, but for sources around 640x480 you'd need a 8K TV - or super resolution 2x on a 4K TV.

I've done testing of super resolution and found that the shaders actually looks way better: Streaming my 4K PC to a 1080p screen result in a image quality way superior than native 1080p using CRT Royale for 320x240 content. I only imagine it would work for 8K to 4K too - for 640x480 content.

This would also allow for better integer scaling as it will result in sharp pixels yet using less borders.

I think it would be very simple to implement: Just adding an option for a scaling factor (1x = off, 2x etc.), initializing the framebuffer taking into account this factor, and finally displaying the framebuffer fullscreen with a bilinear downscale.

I'm aware that you could do the same system wide with NVidia DSR, but for many users it's completely broken - including on my setup: DSR 4x = 8192x4320 instead of 7680x4320 and results in a cropped image - no fix found and I've tried many options.

Thanks!

No files or tests are named. Start by tracing RetroArch's framebuffer allocation and fullscreen presentation paths, then determine where a scaling factor and bilinear downscale would fit. Done means supporting a larger framebuffer that is downscaled to the native display resolution while preserving the requested shader and integer-scaling benefits.