CPU starts using its 100% power while playing high quality videos

I had no problem when I was playing HD videos (greater than 720P, even 4K too) in Ubuntu 19.10.
I have just Installed Ubuntu 20.04 and trying to play HD videos, but video starts lagging and CPU uses goes to 100% while playing HD videos. I always use mpv video player to play all kind of videos
I am using Dell Inspiron 5559 Intel core i3 6th gen, RAM 4GB, Inbuilt skylake graphics.
(I think my laptop's information isn't neccessary for this question because in previous versions of Ubuntu, upto 4K videos was playing smoothly).
What's in my mind for this problem -
I think it is due to the high CPU uses.