Description says it's made by Microsoft, but I haven't seen it anywhere (can't find it on their YouTube or press site).
Questionable whether it's real-time, or whether loading between apps is that quick, considering they're using Gamescom footage of Titanfall, etc.
Interesting video nonetheless. No idea if it was leaked or anything like that, so here's a backup just in case: https://cdn.anonfiles.com/1382913506517.rar
"Xbox, close thread" if old.
Download it here if you want: http://compass.xbox.com/assets/06/69...f30dfa93f5.mp4
They've got a page dedicated to this video