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Update on Digital Cinema Support for Those with Disabilities: April 2013
by Michael Karagosian
Closed caption technology for digital cinema has rapidly moved 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. The wide-spread use of this protocol has allow multiple closed caption systems to proliferate.
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 mapping of media block outputs should follow that of Interop DCP. The Interop DCP audio channel mapping 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.
Interop DCP Audio Channel Mapping and Recommended Audio Output Assignment Table For SMPTE 429-2 Audio
A full specification is online, describing both Interop and SMPTE DCP and accessibility features.
On the device side, USL and Doremi each sell wireless, cup-holder-mounted closed caption displays. In addition, Sony and USL are selling 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 accessibile HI/VI-N audio and closed captions to any of its devices. Doremi’s RF-based wireless system (IEEE 802.15.4) supports both closed captions and accessible audio. Sony's Entertainment Access Glasses also utilize an RF delivery system for closed captions and accessible audio. Those with older Mopix Rear Window™ closed caption devices can get support from several digital cinema systems, including Doremi, GDC, and USL. Doremi, Sony, and USL products are compatible with the license-free SMPTE CSP/RPL protocol.
More information on closed caption systems for digital cinema can be found at these websites:
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