Eyeballs are auctioned to the highest bidder in real time, as I understand it. And don't forget geo and language ad targeting constraints, no point showing Amer

Eyeballs are auctioned to the highest bidder in real time, as I understand it. And don't forget geo and language ad targeting constraints, no point showing American ads to viewers in Germany, or vice versa. Even if you splice on a geo & language basis, there are two basic kinds of interest-based audience targeting: content and users. Putting ads on topic-specific content is OK for brand advertising, but you got to watch out for saturation - you're wasting money if you show the same ads over and over again to the same person. So you want to stop showing a brand ad if someone has seen it too many times already. Showing ads based on user interests has better performance for action campaigns. It relies on some way of tracking the user and / or their interests, but it leads to better conversion as part of a marketing / sales funnel. So you need to select the ad dynamically based on the interests of the user. All this adds up to making it hard to avoid dynamically choosing the ads to show. I think it's still probably possible with careful I/O to do the media stream concatenation server-side, and I expect it's probably the direction things will eventually go, as long as latency etc. works out.