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

Mark -

How much do you have to filter so that an image can move smoothly across 
or down a fixed pixel display 1/2 pixel at a time without aperture 
effect artifacts.  Is it just to the Nyquist limit, or more?

- Tom


Mark Schubin wrote:

> 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.
> 
> TTFN,
> Mark
> 
> 
> 
>  
>  
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