The OP is a more advanced technology. But as to whether you've already seen this on live video, if you've ever watched a baseball game, live coverage of home p

The OP is a more advanced technology. But as to whether you've already seen this on live video, if you've ever watched a baseball game, live coverage of home plate usually replaces the advertisement behind the batter. You'll see that newer stadiums facilitate this by painting blocks of solid color in the spots where the ads appear on TV.