[opendtv] Re: Let the games begin
- From: Craig Birkmaier <craig@xxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Tue, 14 Nov 2006 09:27:01 -0500
At 11:23 AM -0500 11/13/06, Manfredi, Albert E wrote:
What leads to to labor under this misconception, Craig? What is
"completely new" about A-VSB?
The "modulation" is IDENTICAL to 8-VSB. It *is* 8-VSB. You may have
missed the fact that A-VSB, just like E8-VSB, does NOT add any different
modulation types. There is no 2-VSB or 4-VSB, QAM, or anything else.
Instead, the difference is in how some of the payload is being used to
assist in training. And the addition of turbo codes as an extra add-on
convolutional FEC scheme.
I repeat: much like the Chinese did when they modified COFDM.
OK, you are correct that the modulation has not changed. What has
changed is that to make the modulation scheme work better, these new
tools give up payload capacity as a trade-off for bits that help
equalizers track dynamically changing signals and to improve the
robustness of payloads intended for portable/mobile applications. You
COULD say that this is similar to DVB, however, with DVB additional
training signals are not needed, and you DO CHANGE the modulation
parameters to deal with robustness, but these configuration changes
are fully compatible with legacy receivers. Thus it was possible for
Great Britain to move to a more robust constellation to extend the
reach of the DTV network when they switched from OnDigital to
Freeview.
The important point here is that the E-VSB and A-VSb proposals give
up payload capacity to deal with applications that were never
intended for the ATSC standard, and to improve reception in
NON-BACKWARD COMPATIBLE WAYS. We still do not know the real payload
implications, however, I am fairly certain that there are better ways
to achieve robust service than putting band-aids on something that
did not work well.
As to the way DTT is evolving here vs in Europe, it doesn't much matter
whether you think that starting with SD and adding HD after the fact is
better than what we did here. The simple fact is, both systems are
adding features that are USELESS to legacy receivers.
Extensibility. We called for this from day one and the call was
ignored. And, as i recall, we have exchanged oceans of bits arguing
about the relative merits of an extensible infrastructure (especially
the STBs) versus another 40 year standard.
Bottom line, a very large percentage of viewers in Europe have found
that the first generation SD boxes are a viable way to receive a
multi-channel service. If and when they want to upgrade to HD, they
can buy an HD set with integrated receiver or a new STB to feed HD to
both new and legacy displays. And they can buy DVB-H devices that can
be fed from THE SAME transmission infrastructure.
In the U.S. only a very small percentage of viewers bought first
generation boxes, and only a fraction of those people are happy with
them. Yet some, having made that purchase, seem to believe that we
must stick with a lemon, because they made a poor purchase decision.
As a result we are not only stuck with a Rube Golberg first
generation standard, but we are adding more tools to that cumbersome
Swiss Army Knife to try to make it useful.
I'm glad you are happy with the service Bert, but the reality is that
you are part of a very small percentage of viewers in the U.S. that
are benefiting from the service. Asking the rest of us to keep
supporting your investment, rather than using the spectrum to provide
services that will be used by the vast majority of people in the U.S.
is an absurd waste of a valuable resource.
I guess you can take some comfort in the fact that by maintaining the
status quo, once again, Americans will be forced to pay a premium for
subscription services, that otherwise could be provided in the free
and clear.
In Europe, that includes DVB-H, HDTV, AVC. Over here, that includes
A-VSB and possibly AVC. You are making a distinction where there is no
difference.
There is one important difference...
What they are doing is working and is supported by a large audience.
Regards
Craig
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