[opendtv] Re: Why Europe should choose 720P for HDTV
- From: Tom Barry <trbarry@xxxxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Sat, 11 Dec 2004 11:32:44 -0500
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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