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

  • From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
  • To: <opendtv@xxxxxxxxxxxxx>
  • Date: Thu, 11 Dec 2008 11:00:17 -0500

Tom Barry wrote:

> Yes, but is it possible (allowed) to use M/H without any
> extra FEC?

We'll see when the standard comes out. A-VSB did allow this, as I
recall.

Also the other way around is a possibility. FEC without the extra
training. Which would sort of collapse M/H into E-VSB, functionally.

If you remember when E-VSB came out, test results showed that extra FEC
available with E-VSB, when used with 5th gen receivers, did not help for
mobile reception at all, but it did help lower the C/N margin required
for reception. So that would be a good way to make the M/H standard also
useful for cases where you want a more robust stream for fixed
receivers, without paying the penalty for the extra training needed for
mobility.

To me, it would be really STUPID to limit the usefulness of the new
standard only to small handheld devices. When standards bodies do dumb
things like that, the marketplace has a way of correcting the
foolishness, though. So, no worries.

> I got the impression there was other FEC and other extra
> overhead such that, say, 1/2 rate FEC didn't really leave you
> with half of the 19.39 mbps of payload left for data. But I
> have seen no authoritative figures.

Yes, there's some extra overhead for the additional training sequences.

Bert
 
 
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