This was solved in broadcast a long time ago, I'd imagine similar could be done for videos delivered to web browsers, but you'd still be able to detect the inse

This was solved in broadcast a long time ago, I'd imagine similar could be done for videos delivered to web browsers, but you'd still be able to detect the insertion then I guess, so it wouldn't be very useful (unless its WideVine/HDCP or similar so it couldn't easily be seen, but eh)