[opendtv] Re: (No Date: Tue, 28 Sep 2004 10:30:37 -0400

  • From: Craig Birkmaier <craig@xxxxxxxxx>
  • To: opendtv@xxxxxxxxxxxxx
  • Date: Tue, 19 Oct 2004 16:27:39 -0400

At 12:50 PM -0400 10/19/04, Manfredi, Albert E wrote:
>
>First, I can't adjust the vertical height: this is an
>LCD screen.

You didn't say that it is an LCD display. Please tell us who makes it 
so we can avoid buying such a lame product. Then again, it could just 
be Windows, and not the display at all.

LCD displays have ONLY one resolution. At least we can make a safe 
assumption that your screen has 1280 x 1024 pixels that are in fact 
square. When you tell Windows that your display is 1280 x 1024, it 
will happily accommodate you, as this is (was) one of the common 
rasters that are used on larger "workstation" displays.

When you tell Windows to use a raster that is not native to your 
display, most of which are used with 1.33:1 NOT 1.25:1 aspect ratio 
screens, you must do the SAME thing as any HDTV display would do. You 
must scale the raster that is being generated by the computer to the 
best it can to fill the entire display raster, OR you can illuminate 
only the subset of samples that are being used. Thus, for example, 
the display could scale 1024 x 768 up to 1280 x 1024, adding the 
distortions you described, or it could simply use the central 1024 x 
768 display samples putting black or some color in the unused areas 
of the screen.

There is a third alternative, which would be the best approach for 
the display. That would be to scale the output of the graphics card 
up to 1280 x 960, leaving only 64 unused lines at the top and/or 
bottom of the display. I suspect that there are some graphics cards 
that can do this as well, IF they know that the output is ALWAYS 1280 
x 1024, and that other rasters must be scaled appropriately adding 
some throw away areas to deal with the aspect ratio differences. The 
reason I suspect this, is that ALL Apple LCD displays and notebook 
computers do this properly, and they all use the same graphics cards 
as used in PCs. As tyou may be aware, Apple has a number of products 
that offer widescreens in several aspect ratios (none use 16:9, but 
several use 16:10).

In short, it appears that your observations are suffering because of 
a poor product implementation, or that you don't know how to get the 
graphics board to provide the right output.


>Secondly, I don't necessarily want a solution that
>creates black bars, for burn-in issues with other
>display types (e.g. CRT or plasma).

A good implementation will not cause burn-in. This appears to be a 
concern for Plasma, but not a big deal with LCD, and virtually 
irrelevant for DLP.

>
>So the reality is, an aspect ratio standard such as
>16:9 makes a lot of sense, and is becoming the new
>global standard for TV. That's good.

Perhaps for the TV displays built by CE manufacturers. As I said, 
there will likely be a few conformance points for displays. But a 
properly designed system does not care about the display aspect ratio.

>I don't know that it's realistic to even let the pixel
>count used in transmission go completely unrestricted,
>in practice, because I keep hearing about receivers
>having problems locking into certain modes. But I
>frankly don't see a big problem in any of this. The
>problems with sensible standards are politically
>motivated by those with an agenda, not real.

Again, this is due to poor implementations and lack of conformance 
with standard like MPEG-2.

There is nothing magical about any particular raster or aspect ratio 
in a properly designed digital system. In order to do more than one 
properly you can do them all.

Regards
Craig
 
 
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