Brian's Brain

Two days back, I reminded you of a common cost (memory)-driven shortcut that manufacturers of sub-1080-line native resolution DTVs were making when processing 1080-line video inputs; dropping every other line to create a 550-line frame, then up-scaling that frame to the desired end resolution. Now I have the unfortunate task of informing you, if what ATI Technologies told me at breakfast this morning is correct, of another shortcut that some TV suppliers are making. Unfortunately this is one you probably won't notice until you get the set home.

After an OTA (over-the-air) broadcast signal is received by the antenna and frequency-selected by the tuner (either 'can' or silicon), the demodulator processes the 8-VSB modulation (other common modulation schemes are 64 or 256 QAM for cable, QPSK for OpenCable, and proprietary alternatives) and outputs the MPEG-2 audio-plus-video transport stream. As ATI's foilset indicates, filtering out multipath distortion and other interference artifacts is one key demodulator function, along with controlling the tuner to ensure rapid acquisition of new signals in response to channel-change requests.

In distortion-free environments, with strong signal strength, it's relatively easy for any demodulator to output an error-free transport stream. In the real world, on the other hand ;-), all demodulators aren't created equal. Sub-optimal demodulator performance, for example, is why my wife grumbles and switches from the ATSC to NTSC broadcast of her favourite TV show, 24, every time it rains (and lately, in California, it's been raining a lot). This happens even though I have a roof-mount antenna, normally receive a solid signal, and live in a residential area with no tall nearby buildings.

ATI sells demodulators, the result of its mid-2002 acquisition of NxtWave Communications, and therefore has a vested interest in spreading FUD (fear, uncertainty and doubt) about alternative suppliers. Therefore, if the data the company shared with me came directly from ATI, I'd consider it highly suspect. Frankly, I'm somewhat skeptical of the some of the data they provided, from an 'ATI customer'. But the other data set they provided came from the FCC, which I consider to be a less bias-prone, and therefore much more credible, source.

Why isn't this problem already widely known? The vast majority of tuner-inclusive DTV sets sold to date have been large-screen, therefore have been very expensive, and therefore have been sold to early-adopter customers. Very few of these early adopters fed those sets with OTA signals (this OTA-employing early adopter is a rare exception); instead they viewed higher-quality video signals from subscription services such as cable, IPTV and satellite.

Now, however, the FCC digital tuner mandate has extended to 25"-to-35" sets (with all TVs required to contain digital tuners by March of next year) purchased by mainstream consumers. A higher percentage of those consumers get their television content from free OTA sources, either for financial or service-unavailability (in rural settings) reasons. And few of those consumers will tolerate sticking antennas on their roofs (if they even can; apartment and condominium owners, and home renters, won't have this option) when 'rabbit ears' have sufficed in the NTSC era.

If you're a consumer pondering a DTV purchase, don't rely only on how the showroom floor reception (from a signal that most assuredly will not be from an OTA source) looks. Instead, supplement your research with Internet user feedback, along with perusing more formal reviews undertaken in a variety of reception environments, to guide your purchase decision. And if you're a DTV manufacturer pondering demodulator alternatives, consider that a consumer who's unhappy with his or her purchase will cost-burden you with support calls or, more likely, a quick return to the retailer. A retailer whose business relationship with you will quickly sour. Don't be penny-wise, pound-foolish, as the saying goes.

*For the source of my admittedly really-bad pun, see here.