Very noisy/grainy video on S20 Ultra 5G: Why and how to fix?

[jevm]

Hello,

I've noticed the video on my S20 Ultra 5G is extremely grainy, this definitely does not look good for a 2020 flagman... What could possibly be wrong with my settings, etc.? Is there a way to fix this? I am shooting at 4k@30fps.

For the sake of comparison, same environment with my old phone...

[Pugs1957]

I can't view the video but generally noise/grain is caused by inadequate light.