A student in my graduate seminar wants to write a paper on cap codes. What's a cap code, you ask? Well, that's the problem. Very few people seem to be talking about them, at least publicly. Here's a link to a short entry on cap codes on Wikipedia.
Apparently cap codes are small, unique, visible sets of symbols that the Hollywood movie studios now encode onto film prints. They're sort of like the flashes that used to indicate upcoming reel changes to projectionists. In this case, however, the codes identify which cinema a specific print has been sent to. The point of cap coding is to forestall movie piracy--or, at the very least, to help the studios identify which exhibition hall is responsible for letting an illicit duplicate leave the theather and thus to track down alleged "pirates."
My student tells me that the phenomenon of cap coding is fairly widespread, but most everyone involved--the theaters, the trade magazines, the studios, etc.--are pretty hush-hush about the practice. Anyone out there know anything about this or have any leads? Conspiracy theorists are, of course, welcome to chime in, too.