[CentOS] System Time

Sun Mar 8 18:55:08 UTC 2020
Frank Cox <theatre at sasktel.net>

On Sun, 8 Mar 2020 17:59:16 +0000 (UTC)
Chris Olson via CentOS wrote:

> why computer motherboards were not just
> equipped with a chip like the ones in the RCC so that their
> system time would always be correct.

Digital cinema servers (the gadgets that feed the movie to the projector and sound systems) run on Linux.  The movies are shipped to the theatre in an encrypted form and a key is emailed to the theatre that allows the movie to be played from date-and-time to next-date-and-time.  Some keys are valid for one day, most are valid for a week, some are valid for six months.

As you can see, the system time on a cinema server is very important.  If a key is valid at 11:00am for a movie that's to be shown at 11:00am (which can happen even though it's not a good practice) then if your system time is five or ten minutes slow your showtime gets screwed up because you can't play the movie yet.

And cinema server clocks are notoriously inaccurate.  It's one of those ironies that a twenty-thousand dollar server is built with a fifteen cent clock chip in it.  And because the showtimes are an important element of the digital cinema key system, the servers all have a "secure clock" in them that can't be adjusted by more than six minutes per year.

(Yes, they're built that way.  Cinema servers are the most locked down awful-to-deal-with things that you can possibly imagine outside of digital cinema projectors which are also locked down with the additional feature of anti-tamper devices, and a lot of "hidden stuff" in both servers and projectors.  Digital cinema equipment is the only commercial electronic equipment that I know of that is deliberately designed to not do what it's intended to do, i.e. play a movie.)

After learning the pitfalls of this the hard way, most theatres (including mine) now have a computer dedicated to acting as an ntp server in the projection booth to tell the equipment what time it is.

MELVILLE THEATRE ~ Real D 3D Digital Cinema ~ www.melvilletheatre.com