[opendtv] Re: PR: Enhanced AC-3 Audio Specifications Serve Multiple Applications
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Mon, 12 Apr 2004 18:39:15 -0400
John,
It's hard to make a comparison of bit rates without knowing
whether apples are being compared with apples.
The details you provide below are a good start, but for one
thing, we don't have the equivalent for E-VSB.
Anyway, what you provided agrees with ETSI EN 300 744. In
order to achieve 13.6 Mb/s, the LP channel has to go to a
short guard interval (1/32) and has to increase its C/N
margin (Gaussian channel) to close to 20 dB, if you want to
give the HP channel the 10 dB figure. If you recall, the
non-HM 20 Mb/s channel was good for 18 dB of C/N margin,
according to the same source.
So what if you wanted the LP channel to remain as robust
as it was before, in a non-HM channel? In other words, make
the LP channel good for 18 dB of C/N margin (Gaussian),
then see what kind of bit rate you're talking about?
There are a zillion different possibilities with COFDM, but
to give your HP channel the 10 dB margin, you'd have
to reduce the bit rate of the LP channel to about 11.7
Mb/s.
But again, we don't have the comparative numbers for E-VSB,
so it's pointless to split hairs here. I don't think the
difference in bit rates is valid as a comparison point,
yet. They're close enough as to be a wash, at this point.
Bert
> -----Original Message-----
> From: John Shutt [mailto:shuttj@xxxxxxxxx]
> Sent: Monday, April 12, 2004 10:55 AM
> To: opendtv@xxxxxxxxxxxxx
> Subject: [opendtv] Re: PR: Enhanced AC-3 Audio Specifications Serve
> Multiple Applications
>=20
>=20
> Terry,
>=20
> "Nebulous"?
>=20
> Am I wrong about the HP to LP data ratio with E-VSB? Am I=20
> wrong about the
> demos at the 2000 NAB?
>=20
> For the modes used at the 2000 NAB demo, see:
>=20
> <http://www.dvb.org/documents/white-papers/WP01%20(DVB-T%20Hie
> rarchical).pdf
> >
>=20
> Modulation: 64 QAM/QPSK
> Guard Interval 1/32
> LP code rate 3/4
> HP code rate 1/2
> LP bit rate 13.6 Mbps
> HP bit rate 4.5 Mbps
> LP Gaussian noise performance 19.6 dB
> SD Gaussian noise performance 10 dB (this number is on the=20
> document I point
> to on the link above, but was not on the original March 2000=20
> document which
> I still have.)
>=20
> However, it is a moot point, Terry, as E-VSB is as dead in=20
> the United States
> as DVB-T is no matter how well it may perform.
>=20
> Cheers,
>=20
> John Shutt
>=20
> ----- Original Message -----=20
> From: "Terry Harvey" <tjharvey@xxxxxxx>
> To: <opendtv@xxxxxxxxxxxxx>; <opendtv@xxxxxxxxxxxxx>
> Sent: Saturday, April 10, 2004 2:24 AM
> Subject: [opendtv] Re: PR: Enhanced AC-3 Audio Specifications=20
> Serve Multiple
> Applications
>=20
>=20
> > John,
> >
> > Your comparison between DVB-hierarchal modulation and E-VSB=20
> is nebulous.
> > You have no quantitative data to support your assertion.
> >
> > I recall the NAB demonstration. I was impressed but show me=20
> the direct C/N
> > ratio, BERs and bandwidths employed for a direct=20
> comparison. I suspect
> that
> > you will find that E-VSB is more robust under the=20
> comparison you describe.
> >
> > Terry Harvey
>=20
> =20
> =20
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