How Digital Cinema Works
The technology problem imposed by digital cinema are complex. The goal is to replace a very mature film presentation system,
upon which an entire industry is based, with a not-so-mature digital one. Obviously, if we want our ticket prices
to remain low, we want the digital system to be not-so-immature upon rollout of the technology. The technology for projecting
digital images onto screens, however, will not stand still once rollout is begun. Thus, the concept of
"system-level interoperability" is important, as it encapsulates an important aspect of the system that can be addressed up-front.
Interoperability can mean different things to different parties.
Let's take a look at the practical need for interoperability from an exhibitor's point-of-view:
Once a roll-out has begun, it will take many years, possibly as many as 10 years,
to build and install a digital cinema system for all 36,000 US auditoriums.
This estimate does not take into account the over 100,000 auditoriums around the world. An international
rollout of high-grade digital cinema could take a very long time.
The long rollout period places significant importance on the issue of interoperability.
For example, a system installed in Year 1 will have little resemblance component-wise to a system installed in
Year 10. This could be due to advancements in projection technology, data storage, networks, and/or the
digital link (if any) between storage and projector. In addition, we can expect there will be
clever and competitive ways of designing and building systems that we have not yet seen. The progress made
by these advances will likely out-pace the on-going work of standards-making.
Obviously, it is not desireable to impede advances in storage and projection technology, particularly if they have
a beneficial impact on cost. But equally so, it is not desireable to obsolete the investment in digital
infrastructure that will be made in the exhibition booth. To address this problem, a model for system-level interoperability
has been introduced, originally through work produced by the National Association of Theatre Owners. This model is
The model reduces the interoperability problem to only three Presentation system interfaces: Distribution Package,
Back Office, and Security. The Distribution Package requires a common file interchange format. The Back Office interface
suggests common APIs, data files, or protocols for managing the equipment in a multiplex theatre. Security also requires common
APIs or protocols for the delivery of security keys to the Presentation System.
If the focus for interoperability is placed on these three areas of theatre system infrastructure, then the Presentation
System is free to evolve, as it naturally will. This concept can focus the immediate work of standards committees, and
as importantly, it will bring confidence to the marketplace while allowing differentiation in the design of the Presentation system.
It also sets the stage for manufacturers of complete digital cinema presentation systems, much as there are
manufacturers of platter and 35mm projector presentation systems today.
Building from this concept of System-Level Interoperability, we'll explore some of the issues behind each point of interoperability:
Presentation, Back Office, Security, and Distribution Package.
Next: Presentation Systems: The Broadcast Server Model.