No, it is a cat-and-mouse game, because I could start doing things like detecting the ad frames and blacking them out in the compositor. What if my browser had

No, it is a cat-and-mouse game, because I could start doing things like detecting the ad frames and blacking them out in the compositor. What if my browser had a plugin that did that? Think SponsorBlock that talks with the browser's rendering engine. As far as youtube could tell (unless they record my screen and process it to detect that I'm viewing an ad...but that would be a bridge too far for a lot of people I think) the ad is playing, but I'm not viewing. Audio can get similar processing.