DTV Access
The Basics
Captioning | Description | DTV Issues | Legislation | DTV Home
How do viewers access captioning and description in the analog realm?
Viewers access captions via built-in decoder chips in television sets purchased since 1993, or, in older sets, via a set-top decoding device.
Viewers access video descriptions on broadcast programming via the Separate Audio Program (SAP) feature of stereo television. Blind and visually impaired viewers select the SAP option via the flip of a switch or the touch of a remote control button on their TVs or VCRs.
How will the transition from analog to digital affect captions and descriptions?
Digital television will allow many more services and an improved "look and feel" for both captions and descriptions. Caption text can be presented in a variety of styles and sizes, and descriptions will be available for the first time as stereo soundtracks. Additional caption services for beginning readers and in additional languages are possible, and descriptions can be broadcast side-by-side with Spanish and other language translation audio tracks.
Digital television presents an entirely new and different technical system for broadcasters. In the current analog system, caption data are contained in the video's Vertical Blanking Interval (VBI) and descriptions are carried in the Separate Audio Program (SAP) channel. Neither of these exists in the digital domain, although new approaches are outlined in the technical specifications. The challenge for broadcasters is to create digital signals that maintain current levels of service, while implementing new, advanced features.
What is the commercial broadcast industry's progress on implementing DTV access services?
Since the DTV broadcast standards include methods for supporting captions and descriptions, the DTV consumer equipment being sold today should have the technical ability to receive these services. Yet DTV is very much a work in progress. For access services, there are significant gaps in the implementation of the program distribution path from the network to the home. For instance, until recently, there was no accepted method for encoding caption data onto DTV videotape, and much of the "metadata" (control system) standards are still to be defined.
NCAM has been working within the major industry standards organizations (ATSC, SMPTE, CEA, etc.), with major equipment suppliers, and with the industry's DTV Model Station Project to refine these processes and provide solutions. NCAM efforts have resulted in a number of industry firsts, including the first captioned local DTV signal (November 1998) and the first nationally distributed DTV program with descriptions (April 1999). NCAM continues to provide test material for industry use in the further development of captioning and description services.
What is the timetable for rollout of the digital services for disabled viewers?
As of January 2000, more than 100 station had digital signals on the air. Most of the national networks have established regular DTV broadcast schedules. All television stations should have digital signals on the air by the end of 2003. According to the current FCC schedule, all analog stations will go of the air and broadcasting will be fully digital by the end of 2006, if a threshold level of DTV-equipped consumers is reached.
Why is NCAM working on these issues when relatively few DTV sets have been sold?
The time to integrate access features is now, when the DTV system is still under development, rather than trying to retrofit costly solutions once the system is fully established.
What funds does NCAM currently receive to support these DTV Access efforts?
- A three-year, $125,000 grant from the National Institute on Disability and Rehabilitation Research (U.S. Department of Education) which enables NCAM to work with television set manufacturers, participate in industry standards committees, and develop and disseminate data files to test the quality and accuracy in broadcast and reception of DTV captions in commercial and consumer equipment.
- A three-year, 370,000 grant from the Corporation for Public Broadcasting's Television Future Fund which enables NCAM to work closely with public television stations as they transition to digital facilities. The CPB funds build on the Department of Education funded-efforts to determine practical recommendations for costly equipment purchasing decisions during a transition when not all digital broadcast and receiver equipment will pass captions and descriptions. NCAM will also provide information on DTV access issues to national and local disability organizations via this Web site and a National DTV Consumer Advisory Board.
