[opendtv] Re: Mediaflo Technology

  • From: Tom Barry <trbarry@xxxxxxxxxxx>
  • To: opendtv@xxxxxxxxxxxxx
  • Date: Sat, 11 Nov 2006 14:31:50 -0500

While I would love to 'count coup' on Mark (for probably the first time) I don't think I quite managed it here.


My response was really considering the entire analog vs digital TV system. I hadn't considered just the totally fixed pixel displays. For those I think we've had other discussions here about whether the lack of built-in Gaussian filtering means a bit lower effective resolution. I still consider that an open question.

I think we've also touched on the subject about whether it might be better with projectors to get some of that filtering simply by having them slightly unfocused. And I also point out our eyes will likely provide some of that filtering if we are sitting more than maybe 3 screen heights from the display. It all goes back to whether we can actually see the pixel/raster structure.

As a humorous note, anyone trying to read the "A Pixel is Not a Little Square" paper in Mark's link below should note that you can't click on the title, only on the following little red square. That confused me at first and I thought he had only pointed me at an abstract. ;-)

- Tom



Mark Schubin wrote:


Craig Birkmaier wrote:

Looks like Tom caught you here Mark.

You can't compare apples with oranges. We are talking about Nyquist limited images in both cases - i.e. video.

As I pointed out, the edges of the smallest elements of a display violate Nyquist.

I refer you to the title of Dr. Alvy Ray Smith's Technical Memo "/A Pixel is /Not/ a Little Square, a Pixel is /Not/ a Little Square, a Pixel is /Not/ a Little Square! (and a Voxel is /Not/ a Little Cube)."/
http://alvyray.com/Memos/default.htm

The fact remains that in an analog system of ANY bandwidth, the peak (or trough) of a sine wave is infinitely positionable (though the precision and repeatability could be difficult). In a digital system of ANY number of samples, the position of a white (or black) sample is limited by the number of samples.

As a practical matter, low-bandwidth analog spread, high sample numbers, and Nyquist violations make calculations difficult.

TTFN,
Mark



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--
Tom Barry                       trbarry@xxxxxxxxxxx     
Find my resume and video filters at www.trbarry.com


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