Will A-VSB starve HDTV?
January 16th, 2007Mobile digital TV transmissions using A-VSB technology, demonstrated by Samsung at the Consumer Electronics Show, won mostly favorable press coverage last week. The proposed A-VSB standard shows real promise for delivering ATSC digital TV broadcasts—over the public airwaves—to mobile devices. Here’s a big question, though, about A-VSB:
What about HDTV?
While A-VSB really isn’t envisioned for HD broadcasts, a station using the technology might be in a position to shortchange its high-definition programming for home viewers. Doug Lung, in another indispensable “RF Report” post, quantifies the problem:
For broadcasters, the cost in terms of bandwidth for transmitting a signal like the one transmitted on Channel 22 by KVMY for the demonstration may be more than they can afford. The demonstration used quarter rate coding, which meant 3 Mbps were needed to transmit a 750 Kbps media stream. In addition to that, an additional 2.8 Mbps was used by the supplemental reference signal (SRS). This barely leaves enough room to transmit one HDTV program.
To support mobile TV, a station that multicasts could choose to degrade its HD broadcasts. Lung notes, however, that the Advanced Television Systems Committee
will be conducting tests of the proposed A-VSB standard, and acceptable reception may be possible with less error correction and less data devoted to the SRS.
HDTV enthusiasts are already on guard against cable and satellite firms, and broadcasters, too, who shortchange the HD signal. As for me, I welcome A-VSB. Free, on-the-go TV via your cell phone or laptop is a deal I simply wouldn’t want to pass up.
Earlier:
• Samsung to demo A-VSB mobile TV at CES
• Local channels on mobile TV: Test shows promise
• Mobile TV signals for free? Maybe, with A-VSB
• Link: TV Technology