This video shown was put through a program called Topaz Video AI. It uses artificial intelligence to upscale resolution and increase the framerate of the video. An average 3-minute music video can take up to 2 and a half hours to render and requires powerful hardware to maximize render times. My computer setup is currently:
AMD RYZEN 5 4600G
NVIDIA RTX 3060 12GB
32GB DDR4 RAM 4000MHZ
1TB SSD
The quality of the 4K is entirely dependent on the quality of the video you feed into Video AI. A low-resolution video with minimal bitrate and video artifacts will only increase the obviousness of poor quality. I have tried to upscale these older type videos using the highest quality lower resolution video(s).