[opendtv] Re: New Thread: What becomes of Legacy Analog Equipment
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Wed, 28 Nov 2007 12:54:56 -0500
Bob Miller wrote:
> Do what you will with receivers. You can't make legacy
> recievers work with MPEG4 and when you come to the point
> that you want to dump all current receivers to implement
> a better codec it only makes sense to switch to the best
> modulation also.
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.
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.
> At the moment broadcasters are contemplating going with a
> mobile variant of 8-VSB that could use most of the 6 MHz
> channel and I would think they would use MPEG4. While
> technically and legally OK it is not in the spirit of
> maintaining compatibility with legacy receivers.
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.
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.
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.
Bert
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