[opendtv] Re: Which Modulation Would You Choose on a really bad day?
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Thu, 21 Sep 2006 11:21:06 -0400
Cliff Benham wrote:
> What arguments would I be reading about if there were no ATSC, but
> instead we were all watching Sarnoff Advanced Compatible
> Television?
Looks like an all-analog approach to 6 MHz EDTV (not HDTV), where 4 more
analog components are added to the existing NTSC signal.
> Would there be the current problem of co- and adjacent channel
> interference? Would the picture freeze at a critical point in the
> ball game as it does now? Would I miss the critical information
> about the tornado because the weather is blocking my reception?
Clearly, you don't get something for nothing. The patent doesn't say,
but I'd expect that TV transmitters would either have to increase their
power above what's already very high power analog, or the coverage area
of the EDTV signal would be less than the coverage area of NTSC.
> Would broadcasters need to buy, build and pay for power for two
> completely separate transmission systems?
This is only during the transition, with DTT. Whereas with this Sarnoff
analog scheme, it would be a permanent requirement for more power, or
EDTV available over a smaller area than NTSC.
> Would I have to spend $500 bucks for a roof top TV antenna just
> to get a "weak signal" screen message on my $4300 dollar TV?
You mean, if you wanted to receive the EDTV quality? Yes. But if you
were content with NTSC, probably not. Although it's not clear just how
"imperceptible" the extra 4 signals are to the NTSC viewer. Remember
that you're comparing a paper description on a patent with a real,
deployed system.
This is sort of like stereo FM. Compared to mono FM, coverage is reduced
and noise (hiss) is increased. If you're content with occasionally
shifting to mono FM, or putting up with hiss, the existing stereo FM is
fine. This analog EDTV scheme would doubtless behave the same way. On
the other hand, you can get higher definition at much lower transmitter
power with more clever digital techniques.
Over cable, I don't see the advantage at all. Whether converting from
8-VSB to 16-VSB, as originally planned, or 8-VSB to 256-QAM as the cable
industry imposed on itself, is sort of the same thing, isn't it? And you
get room for two or more true 60p HDTV streams in each 6 MHz band, or
many more SD or 24p HD streams, vs barely enough room for one EDTV
stream.
Bert
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