Update on Digital Cinema Support for Those with Disabilities: December 2010

by Michael Karagosian
©2010 MKPE Consulting LLC All rights reserved worldwide

Closed caption technology for digital cinema is rapidly moving forward with the successful standardization of SMPTE 430-10 and 430-11 for the SMPTE CSP/RPL closed caption protocol, an Ethernet-based protocol designed for connecting closed caption systems with digital cinema servers. The SMPTE CSP/RPL communication protocol is license-free. Because of this, the National Association of Theatre Owners encourages all digital cinema server manufacturers to include the SMPTE CSP/RPL closed caption communication protocol in their products. Wide-spread use of this protocol will allow multiple closed caption systems to emerge.

Summarizing the standards effort for accessibility in digital cinema:

SMPTE 429-2 describes packaging for the 5.1, 6.1, and 7.1 SDDS sound formats in the SMPTE DCP (DCP = Digital Cinema Package). Soon, the standard is expected to also include the new 7.1 DS sound format.
Note: Each sound format prescribes how to package HI and VI-N accessibility audio, where HI = Hearing Impaired, and VI-N = Visually Impaired Narrative;
SMPTE 428-10 and 429-12 describe how to prepare and distribute closed caption content in the SMPTE DCP; and,
SMPTE 430-10 and 430-11 describe the SMPTE CSP/RPL closed caption protocol for use between server and closed caption system.

Implementers should be aware that the SMPTE standards for audio do not prescribe the media block outputs on which HI and VI-N should appear. The chart below details the recommended mapping of SMPTE 429-2 sound channels to the audio outputs of the media block. Note that HI and VI-N audio are recommended to always route to outputs 7 and 8. (This differs from an earlier rendition of this recommendation that prescribed outputs 15 and 16 for this purpose.)

Recommended Audio Output Assignment Table For SMPTE 429-2 Audio

In 2009, ISDCF produced a recommended timeline for the implementation of SMPTE DCP, including all accessibility features named above. The goal of the timeline was to upgrade Interop DCP-compliant equipment with SMPTE DCP capability by April 2011. That goal is unlikely to be met. However, the goal to achieve accessibility capability in digital cinema equipment by April 2011 is on track. Support for accessibility audio and closed captions is now available in Interop DCP. A full specification is online describing Interop and SMPTE DCP, including accessibility features.

On the device side, USL and Doremi are now selling wireless, cup-holder-mounted closed caption displays. In addition, USL and Intelligent Access have demonstrated closed caption glasses, which display closed caption text in front of the wearer’s eyes while watching the movie. USL’s closed caption system uses a single infrared transmitter for delivery of accessibility HI/VI-N audio and closed captions to any of its devices. Doremi’s RF-based wireless system (IEEE 802.15.4) only supports closed captions at the time of this writing. Intelligent Access utilizes an RF (WiFi) delivery system for closed captions, without support for accessiblity audio. Mopix Rear Window™ closed caption devices are supported by several digital cinema systems, including Doremi, GDC, and USL. Of the available closed caption systems, USL and Intelligent Access utilize the license-free SMPTE CSP/RPL protocol. Server manufacturers that wish to employ the Doremi closed caption system should contact Doremi for licensing information.

For more information on closed caption systems for digital cinema: