U.S. DTV Broadcasting Implementation Issues
The progress of analog to digital television transition is coming along at an exponential rate. As more and more stations start to broadcast DTV signals, it is apparent that certain problems are starting to catch the broadcast industry’s attention. The implementation issues are being identified and possible solutions are proposed with experts from the broadcast industry and equipment manufacturers that include both broadcast and consumer devices. Participation in the standardization process and investigation of problems/solutions will greatly benefits advanced product development.
Background & Objective: As broadcast standards are approved, many implementation issues arise when actually trying making the system work. Some of those approved standards then go through a period of evolution before the actual deployment.
Technical Discussion: FCC has a deadline for consumer DTV manufacturers to include DTVCC (digital television closed caption) decoding circuitry, but there isn’t any test signals for the manufacturers to test the decoder. Meanwhile efforts in developing broadcast DTVCC encoders are slow in coming, given FCC also has a deadline for broadcasters to include DTVCC data in DTV broadcast. Ambiguities in the DTVCC standard also took some time to clear. Progress is slow in this area of work. Latency and timing: Digital signal has a different path than analog, and the end result is program starts and ends at different times compared to the announced times. This represents great inconveniences to the viewers particularly if one tries to record successive programs from different stations. From the broadcast standpoint, signal delay includes distribution, plant routing, conversion, switching, transmission, and encoding. DCC (directed channel change) has been approved as a standard for over 2 years. Implementation issues include seamless transition between channel changes that include both audio and video, and the triggering mechanism that initiates the actual channel change. Another area of study is the enhancements to the 8VSB modulation standard as adopted by the FCC. The possibility of changing the modulation scheme inspired investigation of the transport standard. A different transport standard must be developed before FCC’s decision. Other issues include advanced EPG (electronic program guide), RF link budget, and standard studio equipment interfaces.
Contacts:
Kent Wittenburg
Technology Area: Advanced Digital Television
Modification Date: January 23, 2007
