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As of 2012, around 60% of all cinema screens worldwide have been converted from film to digital projectors. Over half of those digital screens are outfitted with stereoscopic (3D) projectors. By 2015, it is expected that almost every cinema screen will be digital and that film projection will all but die out.

Digital cinema is a lot more than just a digital projector, however — the film industry, as I’m sure you’re aware, is a multi-billion-dollar behemoth, and digital cinema is probably the biggest shake-up since the advent of 35mm film itself. There’s a whole framework behind digital cinema, from filming, to digitization, to distribution and projection, with some seriously cool tech along the way — which, of course, we’re going to dig into.

Filming

For the most part, movies are still predominantly shot using 35mm film stock. Cinematography is certainly moving towards digital cameras, but the legacy of film is so great — the equipment, the process, the human expertise — that it won’t disappear for a long time. With the rest of the movie making process being almost entirely digital — from editing, to distribution, to exhibition — digital footage is a lot easier and quicker to work with. Just as digital photography usurped film photography, digital video cameras are destined to replace film video cameras, with digital cameras from the likes of Canon and Red leading the way.

Digital intermediate

The irony of using film cameras, though, is that they’re all scanned into a digital intermediate anyway. Almost every big film of the 2000s was converted from film to a 2K (~2048×1080) digital intermediate — so even if you think that film has a higher resolution than 2K, or if the grain is somehow more attractive than pixels, tough luck. If the film is shot with a digital camera, then this scanning stage (which is quite expensive) can be skipped.

Once you have a digital intermediate, talented artists take care of the editing, color grading, and CGI (computer generated imagery).

Distribution

In 40% of cases (conventional projection cinema screens), the digital intermediate is then transferred back onto film, and copies are made (at a cost of thousands of dollars each) for each cinema that will be screening the movie. For digital screening, the digital intermediate is exported as a digital master, which includes all of the video, sound, and data required to project the movie correctly.

Now we get onto the techie bit of digital cinema. Before distribution to cinemas, the digital master is encrypted and compressed into a Digital Cinema Package (DCP), which is a standard format defined by Digital Cinema Initiatives (a joint venture by the major movie studios).

A DCP contains a bunch of multi-gigabyte MXF (Material eXchange Format) files and playlist/index XML files (very similar to the way a DVD contains VOB and IFO files). MXF stores video in JPEG 2000 format (an updated version of JPEG), at 2K resolution up to 60 fps, 4K resolution up to 30 fps, and 2K 3D at 48 fps. XYZ color space is used, with 12 bits per pixel precision (36-bit color). The max bitrate of MXF video files is 250Mbps, or around 30MB/sec. This means a single movie in DCP format is around 200GB. (By comparison, Blu-ray movies generally have a bitrate of around 30Mbps, or 3.8MB/sec.)

The audio MXF files use a standard WAV container with a 24-bit sampling rate of 48 or 96KHz. Up to 12 separate, concurrent audio channels can be used.

Most importantly, these MXF files are encrypted using 128-bit AES — if they fall into the wrong hands (those of a pirate, say) it is virtually impossible to decrypt them.

Finally, the DCP is copied onto a hard drive, which is protected by a rugged enclosure (usually a CRU DX115). These hard drives are then distributed to cinemas via courier. It is also possible to deliver the DCP directly to the cinema via high-speed internet connections, though this isn’t usually done.

Next page: Digital cinema servers, and digital projectors