Can Quicktime record Comcast Video?

Mac Book Pro 10.15.6

Quicktime 10.5

I use Comcast. Have recorded a "video" specifically Mad Max - Fury Road, that was available for "free" on a Comcast channel. I can view it on my Mac Book Pro using the Comcast web site.

But when I try to use Quicktime to record a minute or so of the video, all I get is a totally dark image.

I have even diminished the screen size of the video and put it along side of my desktop - Quicktime records my desktop actions but the video pane remains dark.

Is there some sort of IP, copyright or whatever going on? If so, I understand but how does QT even know?