Digital Cinema Technology
Frequently Asked Questions (FAQs)

What is DCI?

DCI is the abbreviation for Digital Cinema Initiatives, an organization whose owners are the six major motion picture studios (the same six studios that also comprise the MPAA). In July of 2005, DCI issued version 1.0 of its Digital Cinema System Specification, representing the consensus of DCI's members in regards to many technical details of digital cinema. The DCI specification can be thought of the cinema equivalent to the consumer specification of the Blu-ray format. Note that the DCI specification is not a standard. Standards for digital cinema are the domain of the Society of Motion Picture and Television Engineers (SMPTE). A copy of the most recent DCI specification (v1.2) can be downloaded from the DCI website. The latest version incorporates over 200 errata issued since the original release of the specification in 2005.

What does "DCI compliant" mean, and which products are DCI compliant?

"DCI compliant" is a term used to describe products that conform to the DCI specification. Products that have been tested per the DCI Compliance Test Plan (CTP) are posted at the DCI compliance web site.

Notably, DCI compliance does not require compliance to the full set of SMPTE DCP standards. This means that products which pass CTP are not necessarily 100% SMPTE DCP compliant. The Inter-Society Digital Cinema Forum (ISDCF) conducts open "Plugfests" to test for full SMPTE DCP interoperability.

Are SMPTE standards used in distribution today? If not, then how is content distributed?

All digital cinema products are designed to meet an informal specification called "Interop." The Interop DCP (digital cinema package) is based on early draft standards to promote interoperability in the early phase of the digital cinema rollout. Interop DCP is similar to, but not compliant with, SMPTE DCP. It does not support many of the features incorporated in SMPTE DCP, most notably SMPTE audio specifications. The specifications for both Interop DCP and SMPTE DCP, as recommended by the ISDCF, are listed in the ISDCF SMPTE-DCP Transition Review.

Are the digital cinema standards finished?

A full suite of cinema distribution and security standards exist. But digital cinema is a technology that will continue to develop. This will result in new standards and recommendations over time. An example is a new standard currently in process for on-screen 3-D subtitling. Work is also underway to study the necessary compressed image bit rates required of high frame rates, up to 60fps per eye in 3-D. (This work is chaired by Michael Karagosian.)

Security key management is an area ripe for improvement, and new standards will eventually be implemented to promote interoperability.

How do I know if a product follows the latest SMPTE standards?

The short answer is that you don't. There is no formal test available that will tell you if a product meets all SMPTE standards. It is recommended that those buying equipment include detailed specifications in their equipment purchase agreements. Note that simply asking for "DCI compliance" does not guarantee that all SMPTE standards are met, and does not guarantee that the product is ready for use in the cinema.

How do I know if a product meets the High Frame Rate (HFR) requirements?

The DCI specification requires all projection systems to support 48fps at 2K resolution. Frame rate higher than 48fps are a feature of newer projection systems. Older TI Series-1 projectors, for example, cannot show pictures beyond the DCI spec. The high frame rates of interest today are associated with 3-D, at 48fps-per-eye and 60fps-per-eye. This equates to 96fps and 120fps in the total frame rate count. With the exception of Series 1 projectors, all manufacturers claim to support higher frame rates. The bottleneck is the media block and server. An in-projector media block (IMB) is required for HFR, and the media blocks available at the time of this writing claim to support up to 500 Mb/s bit rates, which should be sufficient for anticipated 48fps-per-eye (96fps) releases. However, other bottlenecks exist as well, such as storage transfer rates, and CPU processing power, that can introduce further limits in system performance.

Please note that there is sufficient evidence indicating that higher bit rates will be needed for frame rates higher than 48fps-per-eye, and that current products may not be designed to support these rates./p>

How do I know if a product meets accessibility requirements?

Closed captions and accessible audio are included in the SMPTE distribution standards. They are not specified by DCI, however. As such, DCI compliance testing does not guarantee the presence or behavior of accessiblity features. To insure that these capabilities are in products you purchase, you should specify compliance to the ISDCF SMPTE DCP transition review.

Where can I learn more about the Inter-Society Digital Cinema Forum (ISDCF)?

The Inter-Society's Digital Cinema Forum (ISDCF) is on the web at http://ISDCF.com. Inter-Society is an organization chartered to socialize issues across the industry. The ISDCF is not a standards body, nor is it a compliance or certification effort. However, it is an excellent organization for socializing the unique issues and solutions that pertain to digital cinema.

What is the difference between 4K and 2K projection?

"4K" is the term used to describe images that have approximately 4K vertical lines. In digital cinema, a 4K image with a 2.39:1 ("scope") aspect ratio is delivered having 4096 x 1716 pixels. A 4K image with a 1.85:1 ("flat") aspect ratio is delivered having 3996 x 2160 pixels.

"2K" is the term used to describe images that have approximately 2K vertical lines. In digital cinema, a 2K image with a 2.39:1 ("scope") aspect ratio is delivered having 2048 x 858 pixels. A 2K image with a 1.85:1 ("flat") aspect ratio is delivered having 1998 x 1080 pixels.

Do I need a 4K projection system to play a 4K movie?

No. 4K movies can be played on 2K projection systems with no modifications. Through the use of JPEG 2000 image compression technology, a 2K projection system will extract a 2K image from a 4K digital movie. Likewise, a 4K system will automatically scale the resolution of a 2K image for projection on a 4K projector. This capability results in the ability to share content between 2K and 4K systems, allowing a studio to deliver "single inventory" distributions (i.e., either 2K or 4K).

Can I use a single lens to project both scope and flat images?

According to NATO's System Requirements 2.1, yes. But some studios interpret the DCI specification as opposing the use of a single lens for scope and flat images. A different interpretation of the DCI specification is that it prefers, but does not require, the use of separate lensing to project scope and flat images. If your systems are financed in part through VPF subsidies, then you should have this discussion with your deployment entity.

Can I use an anamorphic lens on my projector?

While anamorphic lenses are the best way to make efficient use of the light available to the projector, not all studios may accept their use. (See the discussion on Single Lens above.)

Note that an anamorphic lens in digital cinema does not rely on the distribution of anamorphically squeezed images, as with film. In digital cinema, the projector can electronically perform an anamorphic re-mapping of the image onto its electronic imaging device, requiring an anamorphic lens to correctly display the image. The benefit of this projection technique is that it utilizes the full imaging array, utilizing the maximum lamp power available. Images projected with an anamorphic lens can light up larger screens than in non-anamorphic installations. The anamorphic projection technique has proven useful for large screen 3-D presentations.

How are security keys (KDMs) delivered?

KDM is the acronym for Key Delivery Message. The security key for each movie is delivered in a unique KDM, one KDM per per digital cinema server. The security key is encrypted within the KDM, which means that the delivery of a KDM to the wrong server or wrong location will not work, and thus such errors cannot compromise the security of the movie.

The KDM is a small file, and is typically emailed to the exhibitor. Most TMS manufacturers can deliver KDMs more efficiently within their ecosystem. In addition, techniques that utilize secure web delivery are now being proposed.

To create the correct set of KDMs for a site requires knowledge of the digital certificate in the projection system´s media block. See the discussion on Facility List Message below.

How are KDMs controlled?

KDMs have only a few conditions associated with their use:

• A KDM will only work for one movie title on one server.
  
• A KDM will only work within the prescribed engagement time period.
  
• The server will only work if connected to a projector that is listed in the Authorized Device List of the KDM. Note that not all studios utilize the Authorized Device List.
  
  

To play a movie on two servers requires two KDMs for the movie. This means that to move a movie to a 2nd server requires a 2nd KDM. The engagement time window of the KDM is set per the business requirements of the studio distributing the movie. If your KDM expires and you don't have a new KDM to continue the engagement, then you cannot play the movie.

To create the KDM, the public key contained in the digital security certificate for the media block must be known. If the studio requires use of the Authorized Device List, then the public keys contained in the projector certificates must also be known.

Certificates are digitally signed by the manufacturer. In this way, those who make KDMs know that they're encrypting keys for trusted equipment.

What other conditions will cause a movie to not play?

One of the "dark screen rules" of the DCI specification is that equipment will fail to function when a security sub-system is tampered with. To a theatre operator, this means that the security components of your equipment must be maintained by others who are certified to repair the security components. You will have to check with the equipment manufacturer to learn who is qualified for this role.

The DCI specification also requires the playout of a movie to fail if the forensic marking capability of the server is not functioning correctly. The server's forensic marking system will mark the image and audio of the movie such that camcordered copies can be traced to the location of theft. If the marking system fails, then the server will fail to playout the movie. However, the studio can enable a flag in the security key to disable the marking system, which will also allow the movie to play with a failed marking system.

What is a Facility List Message?

The Facility List Message (FLM) is designed to carry the collection of digital certificates and related security information that exists in the secure playback equipment of a digital cinema. The FLM is sent to those who create KDMs, so that an accurate set of KDMs can be created. The FLM should be assembled by the theatre owner's equipment, digitally signed by the equipment, and transmitted by the theatre owner's system to those entities authorized to create KDMs. This information in the FLM is also used to populate the Authorized Device List of the KDM. The diagram below illustrates the relationship of the FLM to the KDM.

For those cases where only a single screen is to receive a KDM, such as special authorization for a sneak preview, an "partial" FLM can be created containing the security information for only the desired auditoriums. In this case, the FLM is tagged as "partial," and the purpose of the partial FLM is described in prose inside the message.

Do I need a Theatre Management System (TMS)?

A TMS provides a multi-screen complex with centralized management of all screens. As to whether or not you'll need one, the answer is both yes and no. If the TMS vendor offers a stand-alone Data and Key Management System (DKMS) component, then this should be sufficient for sites having one or two screens.

What do I need to know about digital 3-D?

Digital 3-D bears some discussion. The term "3-D" is used in digital cinema to describe stereoscopic images, where left and right images are displayed on a 2-D screen, and a method for viewing these images is employed such that each eye only sees the intended images. The result is that the left eye sees a different image from the right eye, providing the stereoscopic effect.

The distribution of digital 3-D content is intended to be single inventory, where a single distribution works for all 3-D display methods. However, this is not quite true today. The majority of Real D installations require a "ghost-busted" version of the 3-D distribution.

While there are many techniques for creating 3-D images, there are only three "add-on" technologies available for viewing them when projected by a single digital projector. The add-on technologies can be classified as those using polarized glasses, those using active "shutter" glasses, and those using spectral division glasses. See the article Choice in 3-D for an explanation of how the various 3-D add-on technologies work. Notably, all methods for projecting 3-D can display any form of digital 3-D content, regardless of how it was created.

Four questions can be asked of each method in differentiating the methods:

• What is the cost of the glasses?
  
• Do the glasses require washing?
  
• Does the method require use of a silver screen?
  
• How much additional cost is involved to move a 3-D movie to a 2nd or 3rd auditorium?
  

A fourth method for projecting 3-D images is dual-projection. Dual projection is often used to light up big screens. If dual projectors are used, the exhibitor should be prepared to regularly align them for 3-D presentation.

Can a single projector display 3-D images with full (4:4:4) color representation?

No. Single projector 3-D images are displayed in 10-bit 4:2:2 color representation. While it's true that the DCI specification calls for 12-bit color with 4:4:4 color representation for 2-D images, the specification for 3-D distribution allows 4:2:2 color representation when displaying 3-D images. However, some servers support 4:4:4 color with dual 3-D projection.

What questions should I ask of digital cinema system providers?

Digital cinema has matured, and you'll find that most system providers offer equivalent capabilities. However, it is still useful to ask the following questions of your systems provider:

• Moving the Movie
  How long does it take to move a movie from one auditorium to another?
• Central Office Reporting
  Will the system report to your central office the arrival of content and KDMs? Will it report when KDMs are only days away from expiration? (Note that more exceptions regarding content and KDM delivery are listed in NATO's System Requirements.)
• Maintenance
  Who maintains the system? What Service Level Agreements are offered?
• Security Log Data
  The security policy in the DCI specification is "control lightly, audit tightly." A security log will likely be requested by the movie distributor. The DCI specification and SMPTE standards allows the exhibitor to remove a certain level of sensitive information from the security log. Does your system give you this ability, as well as the ability to view and approve your security logs before they're sent?
• Security of Exhibitor Networks
  The digital cinema system should not compromise the security of the theatre owner's network. The transmission of security log data to suppliers should be under the exhibitor's control. Is this how the system you are considering behaves?
• Review NATO's Digital Cinema System Requirements
  Download NATO's Requirements from NATO's web site. A lot more information resides in that document.

What is the anticipated lifespan of DLP projectors?

When digital cinema began rolling out, it was common to estimate a 10 year lifespan for DLP projectors, as the technology was new and conservative figures were best. Sufficient experience has now been gained, however, to consider an estimated lifespan of 15 years. These figures are provided only as rough estimates, without any warranty of actual equipment performance.

What work remains in digital cinema?

Issues such as NIST-imposed changes in the FIPS security specification, security key management, content delivery tracking, handling of 3-D text for on-screen and off-screen applications, and frame rates higher than those specified by DCI for 2-D and 3-D, are all subject matter of our monthly publication mkpeReport.

What is the status of digital cinema today?

By the end of 2012, some 90,000 digital cinema systems were installed worldwide. Some countries have approached or are rapidly approaching 100% conversion. The US reached the 85% conversion end end of 2012. An analysis of the growth of digital cinema worldwide is in our presentation at SMPTE TSC in April 2013.

Technology adoption cycles have been studied for over 20 years. Stagnant sales and lack of major market uptake following a successful early adopter period is indicative of what author-consultant Geoffrey Moore calls the chasm. However, we're well past that point. While some regions have still to begin a solid transition phase, the worldwide digital cinema installation rate is now reaching its peak, and the worldwide marketplace is now in the Late Adopter stage. The illustration below maps US digital cinema conversion onto the technology adoption curve of Geoffrey Moore.