Enabling the Disabled in Digital Cinema

by Michael Karagosian

December 2009

Editor: You're probably not surprised to learn that the advent of digital cinema will not make all the captioning issues go away. The only thing we know for sure is that it will make them different. Here's Michael Karagosian of MKPE Consulting LLC with his thoughts on the subject. Please do visit them at http://www.mkpe.com/

This article was originally published in the Jan 15, 2009 issue of Digital Cinema Report and is reprinted with Michael's kind permission.

An update with additional information is available at http://tinyurl.com/ya6aoql

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One of the possible benefits of digital cinema is access for those with visual and auditory disabilities. Film technologies for access are proprietary and expensive. New technologies promise improved and lower cost methods for media access in public places. Digital cinema can provide the means to bring these new methods into the theatre environment, and much effort is being directed towards making this happen.

New technologies for increasing media accessibility are now being promoted for all forms of content, including that which is online. Readily available core technologies now exist that can provide the foundation for such methods. This includes, for example, the potential use of IEEE 802.11 wireless Ethernet (Wi-Fi) in the theatre space, as well as the potential use of handheld devices that receive such signals, including a new wave of cellular phones. There are a lot of moving parts in bringing such access solutions into practice, however. While it is difficult to implement competitive access solutions with film systems, the industry is in the process of building a foundation for accessibility into digital cinema such that uniform distributions can support competitive access systems.

The media types for aiding accessibility in the cinema are well defined. A hearing-impaired audio channel, known in the industry as HI audio, is a monophonic mix of that which is heard in the auditorium speakers, but with added emphasis on the dialog track. A descriptive narration channel, also known as visually impaired narrative, or VI-N, is a special track in which a recorded voice narrates what is happening on screen. Both of these audio channels can be transmitted to wireless headphones worn by the patron.

For those who need visual aids, captioning is offered. Captions consist of text that describes the dialog and sound track of the movie. Open captions in cinema are similar to captions in television, where text appears on screen, usually at the bottom of the picture, for all to see. Digital cinema projectors can display open captions, and a standard format exists for distributing these in digital cinema. However, studies show that hearing patrons prefer not to attend movie screenings with open captions.

A more acceptable method for presenting captions to cinema audiences is with the class of system called "closed captions." Closed caption methods present a personal display to the patron, such that the caption is visible only to the patron who wishes to see it. With closed captions installed, the caption can be available at all performances. (Assuming, of course, that the caption is delivered.) This provides enormous flexibility to moviegoers.

With film, presenting anything other than picture poses a problem. If a caption is printed directly on the film print, then the film print is no longer useful for non-caption showings. Worst case, for the studio, this approach doubles the number of prints that must be distributed. There are cost issues for the exhibitor, too. Closed caption display with film requires synchronization of an external display system to the projector. While methods exist for printing a synchronization signal on film, they are proprietary: no open standards exist. Even with the relatively recent (in terms of film history) advent of digital sound on film, none of the digital sound-on-film formats provide the means to include HI and VI-N audio. HI audio in film is typically generated live during the performance, by mixing Left, Center, and Right audio, with an emphasis on Center as the primary dialog track. With film systems, VI-N audio is only available through means of a synchronized CDROM, the player for which is available only from one manufacturer. While methods exist with film systems for increasing accessibility of the performance, they are all proprietary, making it difficult for competing systems to exist.

With digital cinema, the industry is able to take a much different approach. For sound, the native capacity of digital cinema distributions is 16 audio channels, providing more than enough capability to include HI and VI-N audio in standard distributions. SMPTE is close to standardizing audio formats in draft SMPTE 429-2 D-Cinema Packaging - DCP Operational Constraints, which will define how HI and VI-N audio is to be included in standardized distributions. Open caption and subtitling can also be included in standard distributions, and the capability to display these is built-in to digital cinema projectors.

To complete the offering, closed captions will also be included in the digital cinema suite. SMPTE has published two new standards:

* 428-10 D-Cinema Distribution Master - Closed Caption and Closed Subtitle

* 429-12 D-Cinema Packaging - Caption and Closed Subtitle

This pair of standards makes it possible for closed captions to be included in standardized distributions. However, these standards alone do not bring competitive closed caption systems into the cinema environment. SMPTE is currently engaged in the additional development of complementary digital cinema standards titled Content Synchronization Protocol (CSP) and Resource Presentation List (RPL). Together, CSP and RPL will provide the means for closed caption systems of different manufacture to plug into compliant digital cinema servers.

Of course, the publication of standards does not mean that competitive closed caption systems will instantly be available on the market. As manufacturers push ahead to meet the DCI specification, it is important to note that, as of this writing, DCI does not require compliance to SMPTE 429-2 for access audio, or SMPTE 428-10, 429-12, CSP, or RPL for closed captions. It will take more than DCI compliance to get these standards, once completed, incorporated into products. Recognizing this, NATO has begun working with manufacturers to help accelerate the process of closed caption implementation. While much work remains, the effort to create a full suite of accessibility standards for digital cinema is breaking new ground.