[opendtv] Re: New Thread: What becomes of Legacy Analog Equipment
- From: Craig Birkmaier <craig@xxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Fri, 30 Nov 2007 10:41:13 -0500
At 12:54 PM -0500 11/28/07, Manfredi, Albert E wrote:
Honestly, there's some sort of brick wall here that I can't fathom. You
and Craig make this same point, and I can't tell if you're referring to
personalities at the ATSC, or if you are missing the concept of layered
protocols.
When European DVB-T moves to HDTV, it is mandating that this
incompatible HD stream be sent using AVC compression. They are NOT at
the same time mandating a change to DVB-T2 or to DMBT. There's
absolutely no need to change the physical layer just because you want to
add something at the application layer. And also, they are mandating
that SDTV remain at MPEG-2 compression, so as not to obsolete all
existing receivers.
This is NORMAL evolution. They are adding a service that SOME will
find attractive enough to upgrade their receivers. They have NO
REASON to obsolete or update the modulation standard - it already
supports all of the potential modes of operation that people may be
interested in, except perhaps for time slicing to reduce battery
consumption in mobile/portable devices. If a broadcaster in Europe
wants to serve new applications like MPH (mobile portable and
hand-held), they just dial in some new parameters that are supported
by legacy receivers.
Thus your basic argument is correct, for those who have deployed DVB.
But we do not have DVB in the U.S. We cannot simply change a few
parameters of the modulation system to support MPH services. For that
we need to change the modulation standard, which means that only NEW
receivers will be able to use these bits.
While it is correct that we are using layered protocols, the problem
with your argument is that we built our system upon a limited
foundation...
In the US and in Australia, HDTV already exists. So there's no pressing
need to add HDTV, and no immediate opportunity to introduce AVC. But AVC
*could* be introduced just as "easily" as it is being in France and in
the UK.
Yup. If you subscribe to DirecTV or Dish...
Now how do I upgrade that integrated ATSC receiver that the
government forced me to buy?
Oh yeah, just add a new STB...
The mobile stream could use far less than half the capacity of the 6 MHz
band, leaving the rest to existing 8T-VSB television. Obviously, if the
mobile stream were to require an entire 6 MHz channel, you'd consider
moving it elsewhere perhaps, and then could use a different modulation.
But who wins here?
Do we maintain the status quo, protecting you and the shrinking
number of homes that rely upon NTSC/ATSC broadcasts?
Do we wait until there are more MPH users of the TV spectrum than
homes, and gradually starve the legacy fixed TV users?
It may not matter. The companies that win the 700 MHz auctions will
not be so foolish as to use 8T-VSB or any of the MPH proposals for
that matter. They will use the best technology available and they
will define an extensible platform where upgrades are the norm rather
than protection of legacy receivers.
Whatever the case may be, as of now, the FCC requires a TV broadcaster
using the TV spectrum to transmit at least one SDTV stream as MPEG-2
over 8T-VSB. This is very much in line with what is being done in Europe
with HDTV introduction. Over there, SD streams using MPEG-2 are to be
retained as well.
So again, I just don't understand the disconnect. You and Craig are
creating differences that simply don't exist. Everyone has exactly the
same problem with legacy. Lucky for us, we ALREADY have HDTV. And no
need to simulcast HDTV, either. That's good, not bad.
This is because you refuse to listen to reasoned arguments.
Those in Europe who have purchased wide-screen TVs (many of which are
HD capable), will simply need to buy an affordable receiver for the
new services. After a reasonable period of time they will likely get
rid of MPEG-2.
Meanwhile those who invested in HDTV here in the U.S. may see most of
the bandwidth used for MPH services, with a resulting decline in the
attractiveness of the legacy ATSC service. Not that it matters, as
the multi-channel systems are the ones that are driving the HD
transition, not broadcasters.
Which leads to the same conclusion that you refuse to embrace.
Why continue down a less efficient path with a service (ATSC) that is
going nowhere, when you will be competing with services that will use
superior technology.
The important difference is that broadcasters in the U.S. are using
the spectrum to protect a legacy that has little to do with DTV
broadcasting - it does not matter how well it works. Broadcasters in
Europe are using the spectrum to compete...
Successfully.
As to mobile, my personal preference is to focus on making 8T-VSB
receivers better for mobility, with better training, blind equalization,
and diversity antenna, rather than creating the new narrow stream. But
that's just me.
They tried that at NAB several years ago. It didn't work.
It's time to put DTV in the U.S. on a solid foundation. It ain't
gonna happen soon, but you can only keep building on a house of cards
for so long...
Regards
Craig
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