A 25Mb download as an example. You have to be kidding!!! Be reasonable! There are plenty of people here who like to help but you must help us to help you.

But now I have that rant off my chest...

Easy enough to do. You just need a video of the flickery bit at the bottom. It's not obvious how that was made. It might be random noise or maybe a flame flickering. Anyway, just use that clip as a luma key for the clip you play.

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I'm not young enough to know everything!