[opendtv] Re: News: If There's a High-Definition TV in Your Future, Wait Till After the Holidays

  • From: Craig Birkmaier <craig@xxxxxxxxx>
  • To: opendtv@xxxxxxxxxxxxx
  • Date: Tue, 28 Aug 2007 23:51:04 -0400

At 9:51 AM -0400 8/28/07, John Golitsis wrote:
"Physics and the human visual system" as applied to what? Where? When??
What the heck does a "good 480@60P" source have to do with the number of pixels a display offers? I would guess that my computer is a "good 480@60P source", yet the image on the 42" plasma screen in our boardroom looks a heck of a lot better when driven at it's native resolution of 1024x768. Weird, huh? 

Who's weird?

;-)
Let's start with driving that plasma display with a computer. If you input good old 640 x 490 VGA to the display it would need to do one of two things to present the source.
1. Use only a 640 x 480 subset of the native 1024 x 768 display to present the samples in a 1 to1 relationship between source and screen;
2. Scale the non-Nyquist limited sample from the computer from 640 x 480 to 1024 x 768. This would create an ugly mess on the screen as you would be adding filtering to an unfiltered source. Some of the early LCD panels for computers did allow simple pixel repeat modes - e.g. a 1280 x 960 display could simply repeat pixels horizontally and vertically which would double the width of lines etc.
Now let's talk about a good 480P source. A 640 x 480 progressive raster can look very good, especially at higher frame rates like 60P or 72P. But 640 is only enough samples to properly represent a 4:3 source (the square pixel or equal H & V resolution approach). To properly represent a progressive 16:9 source you would need 854 x 480 samples. Unfortunately we only get 704 or 720 samples per line, not 854 with SDTV. It's even worse for the 576 line folks, as they need 1024 samples per line to achieve equal H & V resolution at 576 lines progressive.
Chances are that John may never have seen either of these formats on a good quality big screen display. I am not aware of any products that output 1024 x 576 video, and only a few that operated at 854 or 960 samples per line at 480P. NTV in Japan began to broadcast in 960 x 480P in 1995 and it was very close to HDTV quality.
I have seen these formats and have been involved in tests that created them from higher resolution HD capture gear. The quality can be outstanding, especially if the bandwidth for proper presentation of the full HD version is not available. 

Regards
Craig



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