That would be very, very, very interesting. But it wouldn’t surprise me since COD has an endless list of in-game “bugs” ;D
Programmatically i don’t see any difference? Record -> Replay.
The server is aware of everything. What if you’re optimizing very hardly, and you simply don’t send info about the player movement if they can’t see each other? It can have many reasons why it should be on the server. (Save the killcams to file and watch them later? It is very good for server admins=])
If you’re developing an FPS game you may want your server to take snapshots of the world (For lag compensation purposes). I took it as a starting point so basically you already have the data to work with. You just have to optimize it out and send the important data to the clients.
(Look at lag compensation:
Source Multiplayer Networking - Valve Developer Community)
It’s my approach but i’d like to hear if you have a better idea 