WGBH develops DTV captioning

Broadcasting & Cable
by Glen Dickson
January 4, 1999

Noncommercial WGBH Boston and ABC affiliate WCVB-DT Boston are testing a closed-captioning system for DTV that they hope will become an industry standard.

The system uses a software protocol developed by WGBH and a closed-captioning data server from Ultech Corporation to convert NTSC closed-captioning (the 608 protocol) to the DTV captioning standard (the 708 protocol).

"Ultech came out with a box that inserts captions into 601 [digital] video," says Gerry Field, manager for WGBH's DTV Access Project, a program run by the Corporation for Public Broadcasting and the WGBH National Center for Accessible Media. "We asked them to design the box for DTV, so we could take existing NTSC programming with the captioning already encoded, strip the data off, and reinsert it in the MPEG stream."

The 708 data is then fed into the Harris/Lucent Flexicoder high-definition encoder used by Hearst-Argyle station WCVB-DT Boston to generate its digital content for broadcast. WGBH has been handling WCVB-TV's NTSC closed-captioning for years and has a data line to the station to transfer the information. The two stations are working with consumer electronics manufacturers such as Sharp to test the reception of the closed-captioning data through DTV receivers and prototype DTV closed-captioning decoders.

WGBH's Field hopes that closed-captioning encoder suppliers and consumer electronics manufacturers adopt WGBH's software protocol, which it is openly publishing along with Ultech and Lucent. "Our hope is that there will be one unified protocol."