• From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
  • To: "OpenDTV (E-mail)" <opendtv@xxxxxxxxxxxxx>
  • Date: Tue, 14 Dec 2004 16:35:56 -0500

Craig Birkmaier wrote:
> For ANY given raster, the images will be sharper from
> a progressive scan camera versus an interlaced camera.
> Where we get into trouble is trying to equate different
> formats with similar pixel clocks, such as 720@60P
> versus 1080@60i.
> Clearly, the 1080 line format has more spatial
> resolution along each line, but the vertical resolution
> is subjective. ... the general consensus is that an
> interlace factor of 0.60 should be applied, bringing
> down the 1080 to 648, which is below the vertical
> resolution of 720P, but above 540, ...

Tom Barry:

> I think with proper deinterlacing maybe you could get
> slightly better than .6.

I've seen .65 and .7 mentioned in the past, on many

But one thing that seems to get lost in this is that
even a 720p signal has to be filtered down some. I
think Mark Schubin has mentioned a factor of .9 or so,
to avoid aliasing. If we go around comparing properly
filtered interlaced displays to unfiltered progressive
scan images, we would only be talking with non-nyquist
filtered computer graphics people. Not the TV

So in fact, even using the existing 1080i line standard
rather than going to Tom's suggested 1440 X 1280i, the
comparions is between an achieved:

1080 * .65 equals 702 vertical lines, and
720 * .9 equals 648 vertical lines of resolution.

Whether today's displays can make use of the full
1920 horizontal pixels of 1080i is perhaps a matter of
debate, but certainly more than the 1280 available
with the 720p standard are usable already, in the best

If there's so much controversy as to what format
provides the best images, it's probably because the
competition is tight. The interesting part of this
is that even without CRTs in the picture any longer,
the competition might continue to be tight, for
1080 at 60i vs 720 at 60p.

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