[opendtv] Re: Let the games begin

  • From: "Bob Miller" <robmxa@xxxxxxxxx>
  • To: opendtv@xxxxxxxxxxxxx
  • Date: Sun, 12 Nov 2006 19:41:19 -0500

On 11/12/06, Manfredi, Albert E <albert.e.manfredi@xxxxxxxxxx> wrote:
Bob Miller wrote:

> I didn't spell it out but all the conversations I have been
> privey to suggest that broadcasters would be using MPEG4
> with any A-VSB robust mode which makes all current receivers
> incompatible.

Well, then that's a completely different discussion, isn't it. We were
talking about the technical aspects of A-VSB, not how some particular
broadcasters might want to use it.

Anything I am saying about compatibility is only addressed to the
simple fact that if you are going to use the broadcast spectrum with
any change to the modulation or codec so as to make current receivers
obsolete you open the door to the discussion of changing everything.

That is if you allow A-VSB which could be used on 90% of the spectrum
and could be used with MPEG4/AVC you beg the question why don't we
consider OTHER modulations and codecs as well.

The reality is that if A-VSB is allowed that over some period of time
market pressures will dictate that it be used as much as possible and
with the most efficient codec. Over that period of time all current
receivers will become 90% obsolete receiving only that which
broadcasters are compelled to broadcast in MPEG2 with A-VSB or 8-VSB.

So it is hypocritical to pretend that A-VSB is backward compatible
when it will not IMO be used that way. Instead we should be saying, if
we are honest, that A-VSB represents in reality a non compatible
modulation that will be used with a non compatible codec. And if we
say that then we should also say that all modulations and codecs
should be on the table for comparison to A-VSB. The the false argument
of protecting legacy receivers is just that, a false argument.

Clearly, as we've discussed for many years, there is nothing that makes
8-VSB incompatible with MPEG-4/AVC. These are only implementation
issues, not technical ones. Anyone can make life difficult for TV
viewers, no matter what modulation standard is used.

Who said that anything makes 8-VSB incompatible with MPEG-4? We are
talking about incompatibility with current 8-VSB receivers. Only
implementations issues? Implementing MPEG4 with current receivers
would cost more than a brand new DVB-T receiver and we would still be
stuck with 8-VSB. Not a bargain.

Here's the way I look at it. In the US, we can all enjoy HDTV today. In
Europe, what HDTV there is OTA is incompatible with virtually all
receivers in consumers' homes. By contrast, in Europe, the DTT stream
can be adjusted for robustness compatibly, whereas in the US it cannot

Very strange argument. What does Europe have to do with the US
modulation? They made a choice for SD instead of HD. A choice. Here in
the US we are talking about upgrading a miserable modulation with a
patch that is incompatible with current receivers if used as it will
be used.

So compatibility issues are by no means the sole province of ATSC.

> If you have all of 1.5 Mbps who is going to use MPEG2 with
> that?

For Moviebeam? These are file transfers not meant to be consumed in real
time. That is what we were talking about. Besides which, a Moviebeam
service is perfectly capable of using AVC in its files, since they also
provide the receiver box.

Any spectrum they use will not be receivable by any current receiver
if they use A-VSB and MPEG-4. And to that extent they make all current
receivers incompatible. If that is OK then lets make it OK to use any
part of the spectrum with DVB-T COFDM. Same thing. Lets let 6
broadcasters all put their required SD MPEG2 on one common channel and
use their full 6 MHz channels with DVB-T. In fact if we are being
creative I can think of a hundred other ways to play this game.

As soon as you let A-VSB be used with MPEG-4 you open the pandora's
box. Why can't we use other modulations and codecs if we also supply
our own receiver? Whether it is received in real time or like
Moviebeam in non real time makes no difference.

I want to use DVB-T COFDM and MPEG-4 with my own receivers and I will
make sure that the consumer can still receive one SD channel for free
in MPEG2 on legacy receivers for every channel I so use.

Any problems with that?

I'm saying, that 1.5 Mb/s, using let's say A-VSB in 1/4 rate STS mode,
does not in any way make the remaining 13 Mb/s less robust or
incompatible with all existing receivers. And, of course, that is only
the worst case example.

Again whoever ever said anything like this? Who are you arguing with?

Bob Miller


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