[opendtv] Re: PR: Enhanced AC-3 Audio Specifications Serve Multiple Applications
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Tue, 13 Apr 2004 10:18:01 -0400
John Shutt wrote:
> The Robust portion of E-VSB is claimed to have a S/N of 9 dB,=20
> so that is a
> wash with DVB-T HM. The LP portion of E-VSB is 15 dB vs.=20
> DVB-T HM's 19.6
> dB.
Okay, so the comparison was not apples to apples.
By the way, I'll say again that there's *nothing* magic about
the 14.9 dB C/N margin requirement for 8-VSB. It is merely
the threshold of visibility of errors given the way the
overall FEC is implemented. Meaning, independent trellis and
RS decoding. This can change, as we get a better integrated
FEC decoding techniques in place.
> However, as walking around in my bosses office will=20
> easily demonstrate,
> there is more to receivability than carrier to noise figures.
This is no doubt a dynamic echo problem, then, and I don't
think your boss is using a Linx Casper chip yet (not that
dynamic echo is its forte, but then again, it ahould be
fine for just people walking about).
> At the 2000
> NAB, the LP portion of the DVB-T HM stream was received on=20
> the convention
> floor, where no 8-VSB could be received at any booth by any vendor.
Yeah, we know that early receivers sucked.
Bert
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