[opendtv] Re: Let the games begin

  • From: "Bob Miller" <robmxa@xxxxxxxxx>
  • To: opendtv@xxxxxxxxxxxxx
  • Date: Mon, 13 Nov 2006 16:39:03 -0500

On 11/13/06, Manfredi, Albert E <albert.e.manfredi@xxxxxxxxxx> wrote:
Bob Miller wrote:

> There is no argument in Europe over their modulation. Only
> discussion over how to get from SD to HD. The UK will
> upgrade from their 2K to 8K and most of their receivers
> are ready for that.

I think you are missing what has to happen in the UK.

Yes, the newer receivers should have no trouble going from 2K to 8K, the
older ones will go dark.

But why the move to 8K? 8K does not add spectral efficiency by itself.

The move to 8K is to tolerate more echo range. And the reason they need
to tolerate more echo range is to install SFNs. And the reason they need
to install SFNs is that they need to migrate from 16-QAM to 64-QAM to
support the HD bit rate, and don't want to go to high power big sticks
in doing so. They want to use low power big sticks instead.

So the move to HDTV is not so simple. And, besides that, they still need
to broadcast the SD simulcasts, assuming they want shows to be available
to SD and HD viewers alike, as we do here.

> For example the VSB modulation that the Chinese will not
> use is only another step up the ladder from A-VSB. The
> difference is that with A-VSB we have the argument that it
> could be used in such away that all legacy receivers could
> theoretically receive all broadcast while we know that in
> reality it will be used in such a way as to make all
> legacy receivers obsolete.

The Chinese VSB scheme is probably better at high spectral efficiency
settings than 8-VSB, although proper LG prototype-like receivers are
apparently very good anyway. And could be made better, e.g. by doing the
Viterbi and Reed Solomon FEC differently and by improving the way
training is done. But I doubt the Chinese system is any better at the
very robust modes than A-VSB. When you get close to the Shannon limit,
as A-VSB does with diversity antenna, the message is that you can't do a
whole lot better.

Why this apparent need to consider A-VSB to be a pointless kludge?


If we are saying that in the US broadcasters will enthusiastically
embrace and use A-VSB with MPEG2 then maybe it is not a pointless
kludge, just a pointless and inefficient one.

If, as i suspect however, broadcasters would only embrace A-VSB if
they plan on using it with all the bandwidth and with MPEG4 for all
but the required SD MPEG2 program then it is indeed an unnecessary
kludge and still inefficient.

And at that point, the point where all legacy receivers are for all
intents and purposes made obsolete, it would make all the sense in the
world to consider changing to a better modulation and codec.

Or you could argue that even if all broadcasters only sent the
required one SD program in MPEG2 that that alone would justify staying
the course with 8-VSB/A-VSB forever.

Forever is a long time. The way we do things in this country the next
correct time to chance modulations and codecs  will be the day that
87% of the public has legacy receivers a percentage of which can
benefit from A-VSB. We have to wait for that moment to screw the most
people the most.

More likely is that most of us will continue to pay little to no
attention to OTA. Everyone will have a receiver in their big DTV sets
and the fact that you can actually possibly receive something with it
will be a trivia question on Jeopardy. One which any one under 30
won't get.

Bob Miller

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