[opendtv] Re: DVB considers SVC for 1080p and hierarchical modulation

  • From: "John Willkie" <johnwillkie@xxxxxxxxxxxxx>
  • To: <opendtv@xxxxxxxxxxxxx>
  • Date: Wed, 10 Dec 2008 23:41:13 -0800

I'm reasonably confident that there are no artificial constraints on how
much 8-VSB physical layer bandwidth can be used in M/H.  Note the word
"artificial."  There are only so many "segments" that can be allocated to
M/H, due to the way that things are coded.  There's even a very interesting
chart that shows all the slots.  I'm not sure that will ever be made public.

There are several layers of constraints, and I think all but bert will see
soon enough that M/H cannot be used without the "extra FEC."  Indeed, all
but idiots can already see that the "extra FEC" is the REASON for M/H.

It's "possible" that a meteor will strike the pinnacle of the Washington
Monument within 30 minutes of me posting this and destroy the entire
structure.  Possible, but not likely.  

But, then if idle musing about possibilities, even illogical ones, was
forbidden here, bert would have very little to say.

One who reads standards, particularly ATSC ones, knows that they are
actually ALL about constraints.  

So, foolish Bert, how much money would you put behind your bet?  A week's
pay?


John Willkie

-----Mensaje original-----
De: opendtv-bounce@xxxxxxxxxxxxx [mailto:opendtv-bounce@xxxxxxxxxxxxx] En
nombre de Albert Manfredi
Enviado el: Wednesday, December 10, 2008 6:06 PM
Para: opendtv@xxxxxxxxxxxxx
Asunto: [opendtv] Re: DVB considers SVC for 1080p and hierarchical
modulation


Tom Barry wrote:
 
> Will ATSC M/H even have enough throughput for a single
> decent 720p stream after error correction?
 
That's a bit like asking whether ATSC can handle H.264. Lots of people swore
it couldn't, but they were wrong. Standards can always be amended, and
adding H.264 was a fairly obvious possibility right from the start.
 
One possibility here is if M/H can be used without the extra FEC. Just for
its extra training or for use with SFN towers, as A-VSB allowed. If it can
be made to do that, and you dedicate the entire channel to M/H, then in
principle you should be able to support HDTV without any trouble.
 
Another possibility is if you dedicate the entire channel to M/H and use 1/2
rate FEC. IN PRINCIPLE, that gives you approximately 9 Mb/s capacity, which
IN PRINCIPLE is enough for 720 at 24p, even with MPEG-2 compression.
 
I'll bet the standard will artifically limit how much of the channel can use
M/H, just like E-VSB does. That's just penmanship, though. It would be
inconceivable for receivers to police that rule, if there were such a rule.
So all it would take is someone to amend a paragraph or so, and that's that.
 
Bert
 
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