NAB and MSTV have selected LG Electronics and Thomson, SA, to each develop prototypes for what NAB says should be a "high quality, low-cost Terrestrial Digital Converter Box" (TDCB) that consumers can use to receive DTV signals on conventional analog sets. In notifying its TV membership of the choices this week, NAB said the performance of the prototypes will be evaluated based on a set of technical requirements developed by both NAB and MSTV.
"It is hoped that the TDCB will serve as a blueprint for future products from manufacturers to help ensure that the more than 70 million analog televisions relying exclusively on terrestrial broadcast signals will continue to receive free over-the-air television service when all-digital broadcasting begins," NAB reported in its weekly technical newsletter to its members.
NAB and the CEA strongly disagree on the total number of sets-in-use today that rely solely on off-air signals; CEA maintains that many of NAB's "70 million sets" are actually dedicated to DVD and VCR use only, and are not even hooked up to terrestrial antennas, much less cable to DBS.
Design goals for the TDCB focus on the performance of three major functions: "RF Tuning and Demodulation," "MPEG Decoding" and "Digital to Analog (D/A) Conversion." NAB engineers said the TDCB will tune the frequency bands from 54-72 MHz, 76-88 MHz, 176-216 MHz, and 470-806 MHz, decode the compressed bitstream, and convert the digital bitstream to an analog signal using a D/A converter.
NAB and MSTV say the produced analog signal should be able to be delivered to an NTSC-only receiver on ch. 3 or ch. 4, along with a baseband composite video output with stereo audio. Both trade groups also will insist that the final product be inexpensive to consumers, although they did not provide pricing parameters. When the prototypes are delivered, NAB and MSTV will conduct extensive lab and field tests.
