[opendtv] Re: U.S. mobile TV spec in the works
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Tue, 10 Apr 2007 17:30:29 -0400
John Shutt wrote:
> Exactly what I said, Bert. A scheme that doesn't break existing
receivers,
> but doesn't confer any new robust receive capabilities to existing
> receivers. Just reduces the amount of payload existing receivers can
see
> and decode.
Two different interpretations of "backward compatible."
One is where the robust stream is completely invisible to legacy
receivers, even though it may coexist in the same band with other
standard streams. That would describe E-VSB, A-VSB, DVB-H.
Another is where the robust stream is decodable by all receivers, even
if legacy receivers don't benefit from any extra robustness. That is
what I would describe as "backward compatible."
If this MPH scheme was described as being "in band" and "backward
compatible," my expectation would be that the description differentiated
MPH from other proposals. My point was to say, maybe it does not.
Here's what I was wondering about:
"From the description, what makes this MPH scheme different from A-VSB
and DVB-H is that MPH is supposed to be 'backward compatible.' That
might mean that the more robust MPH stream is also receivable by
standard 8-VSB receivers, even if not with the extra robustness or power
saving features.
"But I may be wrong with that interpretation. 'Backward compatible' can
also mean that MPH streams can coexist with standard 8-VSB, just like
A-VSB can, and just like DVB-H can coexist with DVB-T."
To this, you said there could be no magic. But not magic was ever needed
for either approach.
Bert
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