Camera [Q] Better quality for Slow Motion?

I just searched the forum for a Mod/Rom/Kernel/XPosed Module that allows better Quality on Slow Motion videos. I just found a few questions in this thread but they are all a few months old and maybe these things are different now. Does anybody know, if there is a way to increase the quality? Be it ROM, Mod, Kernel or XPosed Module.
If not: I would be interested in the reason why. Is it not possible because of the camera, the CPU, GPU, NAND? Or has just nobody worked on it yet?