[opendtv] Re: Microsoft Exec: 1080p HDTV Is Meaningless

Craig Birkmaier wrote:

> Tom Barry wrote:
>
>> I'm still not sure why you single out non-nyquist filtered images as
>> being a special problem for non-square pixels.
>
> Because virtually all computer applications and web pages use the
> convention of non-Nyquist filtered square pixels to represent graphics
> on a display (computer or any entertainment display that also can
> display this type of images.

[ ... ]

> Any pxel geometry can be used with non-Nyquist filtered samples. You
> may recall that this was the case with early computer display formats
> like CGA and EGA. The problem is that when these samples are
> displayed at other pixel aspect ratios (without filtering) the image
> will be distorted. This is the reason that the computer industry
> quickly adoped square pixels as the lingua franca for non-Nyquist
> filtered samples.

Unfortunately, it looks like video drivers manage to mess up proportions
anyway, even if square pixels are used throughout.

Take the case of the oddball aspect ratio display, like square-pixel
1280 X 1024 (1.25:1), made to sync up to standard 4:3 resolution options
such as 1024 X 768. Since no one in PC-land would stand for permanent
black bars when using these standard resolution settings, these displays
will normally distort.

One might think one solution would be for the video drivers *not* to
offer any of the standard resolution options, but only offer something
close which has been modified to 1.25:1 aspect ratio. For example, don't
offer 1024 X 768, but rather 1024 X 819.

That would work, unless one wants to display to scale, full frame,
native 4:3 graphics.

So here is a case where square pixels don't help in preventing
distortion, and where non-standard display aspect ratios conspire to
create that distortion.

Bert
 
 
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