DCP? What is that?

When I studied film, "film" meant celluloid—actual film stock—and everything else was just video. Or at least that's what some of my professors taught me. There was one, though, Antonio Cuevas, who—knowing that making movies was very expensive—taught us to tell stories using video cameras and make them look like cinema. The year was 2004; I still had collagen, and movie theaters had enormous projectors.

In 2009 I was lucky enough to earn my master's in Digital Cinema at the Escuela de Cine de Madrid (ECAM), and as part of a course they took us to Yelmo Cineplex, a theater chain where they showed us a brand-new, incredible auditorium with digital projectors. For me it was a revelation. But when I got home, I ran into the fact that seeing the technology in action is one thing, and understanding it well enough to hand something off to a theater without the screening falling apart is another thing entirely.

The world we were leaving behind

To understand why the DCP changed everything, you have to remember how things used to be done.
Back then—and for a bit longer than you'd think—movies played on celluloid. Picture Bill pulling up to the theater in a van loaded with reels of film that weighed dozens of kilos. Bill would carry them up in batches to Frank, the projectionist, who'd mount those reels on a big platter and splice the film reel by reel so it could be projected. Literally, the film passed physically in front of a light and was projected onto the screen.
Those of us who are a little older remember that projector sound very clearly: qrrrrrrrrrrr. And if you had bad luck, you also remember the exact moment that film snapped and the screen went blank. A lot of disappointment in the auditorium, and poor Frank sweating buckets to splice the film back together and keep the screening going.
It was a fragile, heavy, expensive system. Every copy sent to every theater was physical. Every screening wore the film down a little more.

The idea that changed everything: the DCP

That began to change in the late 2000s. A group of Hollywood studios—Disney, Warner, Universal, Paramount, Sony, Fox, and MGM—formed a consortium in 2002 called DCI (Digital Cinema Initiatives). In July 2005 they published the first version of their standard, the Digital Cinema System Specification, which is basically the manual that defines what a digital cinema copy has to look like so it works the same way in any theater in the world.
What was the idea behind all of this? On one hand, to prevent piracy; on the other, to modernize the entire film distribution process.

The result was that Bill no longer showed up in that van with dozens of incredibly heavy reels. Now Frank was handed a hard drive. Just like that. And that's what made digital projection take off all over the world.
What's that copy that arrives on the hard drive called? It's called a DCP, or Digital Cinema Package, and it's the way movies are distributed for theatrical screening today.
The triangle that makes the movie play

Now, here's the part that was hard for me to grasp at first—and that, once you understand it, saves you a world of headaches: a DCP isn't the only thing you need for a movie to play. There's a triangle of three elements that all have to match up, and the whole thing revolves around preventing piracy.
The theater's certificates. Every projector and every server in every theater has its own digital certificate, like a unique fingerprint.

The copy—that is, the DCP. Inside, the DCP contains something called a CPL (Composition Playlist), which has a unique number that identifies that exact version of the film. If that DCP is encrypted, it won't run unless someone issues a key for it.

The KDM (Key Delivery Message). This is the key. And here's the magic: if the KDM matches the theater's certificate and the DCP's unique number, then—and only then—the movie can be projected. On top of that, the KDM can be restricted to a set time window or to a specific number of screenings.

When all three sides of the triangle fit together, the movie plays. If even one doesn't line up, there's no screening. It sounds strict, but that's exactly what protects the copy.

Why this was wonderful for cinema

This was a marvel for our world. Bill no longer broke his back with reel after heavy reel: now you sent a hard drive and, by way of a simple email, the KDM arrived.

Today you don't even need the physical shipment—Bill has retired anyway. The copy can be transferred digitally, and many theaters already receive it that way, without a hard drive having to cross the city or the country. Sometimes Frank dozes off and nothing happens.

And there's another advantage that, for me as a filmmaker, is the most important of all: a DCP maintains consistent quality no matter the auditorium. Before, with celluloid, every time you ran the film you lost a little quality; it got dirty, it got scratched, and in the end what you saw on screen wasn't really what you'd shot. With a DCP, what you deliver is what gets projected—the same in auditorium one as in auditorium fifty.

Today it's easy

It has never been easier to deliver high-quality films for theatrical projection. The tools are there, the standard is written, and the path is already open.
So my invitation is simple: experiment, create your own DCP, and play your movie in the theater.