[opendtv] Re: Mediaflo Technology

  • From: Craig Birkmaier <craig@xxxxxxxxx>
  • To: opendtv@xxxxxxxxxxxxx
  • Date: Sun, 12 Nov 2006 07:21:22 -0500

At 2:31 PM -0500 11/11/06, Tom Barry wrote:
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.

Exactly right. Any image display system design needs to take into consideration the designed viewing characteristics of the environment. We need to know the viewing distance and the field of view that is to be covered, in order to create a display system that can reproduce highly detailed images and smooth motion without the perception of aliasing.

The design criteria requires that the human observer NOT be able to perceive the raster in the display. This is the primary determinant of the sample density, along with the desired frequency response - i.e. the highest level of detail that the observer can resolve. Having more samples than needed - display oversampling - can be highly advantageous, as long as the cost is not outrageous, and the system operator maintains sample integrity.

A good example today are all of these 1080P displays that are popping up everywhere. They really do help reduce the perception of the raster. But we need to get the system operators to understand that it is NOT NECESSARY to deliver 1080P rasters to take full advantage of these displays. What is needed is very clean 720P, without all of the compression artifacts and "digital filtering" (quantization) that is common with DTV signals today. The other major benefit of display oversampling is that we can reduce the perception of aliasing in non- Nyquist applications such as local graphics and viewing web content. When we get the DPI of a computer display up above 100 samples per inch, most of the aliasing in computer applications goes away.


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