[opendtv] Re: Kennard and Powell to the rescue
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Tue, 13 Jan 2009 11:08:33 -0500
Bob Miller wrote:
> Legacy receivers ignore the M/H streams and therefore
> can't take advantage of them. How's that?
Correct. This is exactly the same as DVB-H, in terms of what legacy
receivers can do with the signal. Meaning, the signal is transmitted
over the same Physical Layer, but the Link Layer makes it incompatible
with legacy receivers.
> Wouldn't be more correct to say that M/H can use both
> MPEG2 and MPEG4 but that legacy receivers cannot use MPEG4?
It could have been that way. I believe that A-VSB did allow that.
However, check out Figure 5.1 of Part 1, and you will see no MPEG-2
compression option for the M/H stream(s). Only AVC (H.264, or what you
call MPEG-4) is allowed.
> And since the rules say that the required SD program in the
> free and clear must be delivered with MPEG2 that Congress or
> the FCC cannot allow the required SD program to be delivered
> with MPEG4 without changing the rules? If they change the rules
> they are making all legacy receivers obsolete.
This is precisely the same as DVB-T is dealing with now. Not so much wrt
DVB-H, but wrt DVB-T2. Yes, of course, any incompatible change to the
standard will not work with legacy receivers.
> Think of it, if you go with M/H for the SD required program
> and are left with a bit starved non HD 8-VSB program why not
> just use all the 6 Mhz with M/H and MPEG4?
No one is talking about using M/H for everything, and for now it is
obviously not allowed by the FCC. Broadcasters have to transmit at least
one SD quality FOTA program, MPEG-2 compression, and that rule predates
any M/H standard.
> Of course everyone would need a new receiver and modulator
> and at that point why not just go with the BEST modulation
> instead of M/H?
Real engineers (no aspersion on you, Bob, since you never pretend any
such thing) come to realise, there is no absolute BEST. There is one
compromised solution vs another compromised solution.
Bert
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