[opendtv] Re: MPs back Ofcom stance on spectrum sale

  • From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
  • To: <opendtv@xxxxxxxxxxxxx>
  • Date: Tue, 22 May 2007 15:16:32 -0400

Craig Birkmaier wrote:

> There are several flaws in this argument, that work both for and
> against you.
> First, you cannot equate pixel density and bandwidth requirements.
> bandwidth requirements are determined primarily by information
> content and entropy. The good news about higher resolution formats
> is that they are more highly correlated, thus typically can be
> compressed at a higher compression ratio for a given level of
> image quality. The bad news is that they typically have more
> noise, and may deliver more information, both of which requires
> more bits.

I already showed you how to determine the max bandwidth available for
sending baseband info to the display. If you use that same scheme, you
will find that the 2.25X factor exists for 720 at 60p compared with 1080
at 60p. It is the maximum possible, so you can avoid going around in
circles wondering about the detail content in the 720p vs the 1080p
images, entropy, etc. All of that is canceled out of the equation. In
the worst case, 1080p tranbsmission *is* indeed reasonable, if your
compression algorithm is 2:1, or slightly better, against H.262. Simple
statement, Craig.

> next, you are making an invalid assumption about the adequacy of
> 20 Mbps for 720P.

No. I am only saying that if it's adequate for 720p, it will be equally
adequate for 1080p, with the better compression algorithm. Again, *how*
adequate is canceled out, in the comparison.

> The U.S. broadcasters are protecting "their" spectrum and
> retransmission consent.
> Now the U.K broadcasters are are using HDTV to try to protect
> their spectrum.

They aren't. The spectrum they are asking for is not even as much as
they had in analog. Their SDTV programs take up less spectrum than they
used to need, and Ofcom is telling them they cannot have any of the
analog spectrum back for HDTV.

> The majority of deployed HD capable displays do not have
> access to HD content - just because there is an ATSC tuner
> in there does not mean it is being used.

I don't know the number of households actually viewing HDTV content, and
you haven't provided any numbers, but my bet is that the number is
rapidly growing. It's not for nothing that Verizon, DirecTV, and cable
companies are advertizing their HD content so heavily these days.

It probably helps that analog content looks pretty darned bad on LCDs
and plasmas. At the store, the image looked wonderful. Take it home, it
lokks crappy. Let's get the digital tier! Let's get HD! So it's a
completely different situation now than it was in the early 1990s, and
it is driven at least as much by consumer interest as it is by

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