[opendtv] Re: Why Europe should choose 720P for HDTV

  • From: Mark Schubin <tvmark@xxxxxxxxxxxxx>
  • To: opendtv@xxxxxxxxxxxxx
  • Date: Sat, 11 Dec 2004 10:11:38 -0500

Doug McDonald wrote:

>Discrete pixel displays change things.
They do, but not always in beneficial ways.

If we knew that every display was 1920 x 1080 -- or any other fixed set 
of numbers -- we could optimize camera, processing, and transmission 
parameters to match those displays.  But we have no such situation. 
 There are 1024 x 1024 displays, 1366 x 768, and others, in addition to 
720p's 1280 x 720.

Consider the unique case of 1920 alternating black and white vertical 
lines (960 of each).  In theory, they can  be displayed on a 
discrete-pixel display with 1920 pixels across.  Now shift them 1/2 
pixel horizontally.  The result is all grey.

If we knew that every TV set would have 1920 pixels across, we could 
make sure such a half-pixel horizontal shift would never occur.  But 
with multiple resolutions, there will be scaling, and scaling can 
effectively shift everything out of the discrete-pixel grid.

Consider this.  Which has more resolution?  A 440-line NTSC broadcast or 
an 852-pixel-wide plasma panel?  Due to the pixel-shift phenomenon, the 
852-pixel display can only display half as many TV lines of resolution 
as pixels with a guarantee that they will be actually black and white. 
 That's 426, slightly less than broadcast NTSC resolution.

I think that's what John Watkinson was driving at.

He may wear funny clothes and hurl hilarious insults, but the author of 
The Art of Digital Video is not unaware of discrete-pixel displays.


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