I was under the impression they are OGV videos; I'd check but I have no Starcraft II access right now. Just open up the SCII MPQs and have a look, there's an article on the wiki about MPQ editing.
Red classic.
"In short, their absurdities are so extreme that it is painful even to quote them."
Vrael shouted: I almost had a heart attack just thinking about calculating all the offsets it would take to do that kind of stuff
With the modern EUD editors, I don't think they're calculating nearly as many offsets as you might imagine. Still some fancy ass work that I'm sure took a ton of effort