How Digital Cinema Works

Putting It All Together

Now we get to put it all together.

To depict how a real system might look, we present the block diagram below. (click to enlarge)

Our block diagram shows a SAN-based system, chosen for its ability to easily move shows from screen-to-screen. We also show the compression and decryption functions in the projector. As 4K technology advances, digital cinema systems will either need to accomodate the increase in bandwidth to the projector through encrypted links, or migrate to a "pull" architecture where the projector directly receives encrypted, compressed data. The natural system architecture then becomes the "pull" architecture of the SAN-based system.

We haven't said much about audio, and it deserves a little attention. "N+1" audio channels are shown in the diagram, a simple way of saying that N channels is never enough. If you're familiar with the history of film sound, N+1 says it all. However, in our constrained digital cinema system, the maximum number of channels has been set to 16. With luck, that'll get us through the next 50 years. In terms of interconnects, 16 uncompressed audio channels happen to fit nicely over off-the-shelf Ethernet, even when using 96KHz sampling and 24-bit audio.

A new block is shown in the diagram above: the Theatre Management System, or TMS. The Theatre Management System is a central place for operations-related tools. This could be a stand-alone TMS, or it could be part of the theatre's back office system. Not all installations may have a sophisticated TMS, however.

As you might expect, there's more to the digital cinema story than we have covered here. Digital cinema is not television -- it is much more complex, flexible, and quality-oriented. While not always visible to the public, many people are working to move this technology forward. In time, you'll be able to enjoy the fruits of their labor.

See also our pages on An Early History of Digital Cinema Technology.