Video Ad Link Locker?

I have seen a few sites using video ads as link lockers. They play a video, then it either lists a phrase to type or just asks a question, then the download link appears. I've been looking into this out of curiosity on how much they are making....but so far I am not finding any answers. I was wondering if anyone here has ever used one of these and which company you use? Or if not video...a way to use a link locker that does not have those surveys

I'm still hunting info, so if anyone knows it will be very much appreciated!