[opendtv] Re: DVB considers SVC for 1080p and hierarchical modulation
- From: Tom Barry <trbarry@xxxxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Wed, 10 Dec 2008 23:25:22 -0500
inline ....
Albert Manfredi wrote:
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.
Yes, but is it possible (allowed) to use M/H without any extra FEC?
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 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.
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.
No idea and I can't even speculate on what they are liable to come up
with here.
- Tom
Bert
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