[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.
Regards
Craig
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