[mythtv-users] Graphics card recomendation

stefan thomasson stefan.thomasson at home.se
Thu Aug 31 14:06:26 UTC 2006


> -----Original Message-----
> From: mythtv-users-bounces at mythtv.org 
> [mailto:mythtv-users-bounces at mythtv.org] On Behalf Of Michael T. Dean
> Sent: den 31 augusti 2006 03:00
> To: Discussion about mythtv
> Subject: Re: [mythtv-users] Graphics card recomendation
> 
> 
> Or, really somewhere around 3840x2160 would be an appropriate output 
> resolution for a 1080i/p input resolution...  In addition to the fact 
> that (as previously mentioned by Daniel) 3840x2160 is an integral 
> multiple of both 1280x720 and 1920x1080, sampling theory 
> (specifically, 
> the reconstruction theory part of it) says that an output resolution 
> must be greater than an input resolution to fully represent 
> the detail 
> in the image.  As a general rule of thumb, the output 
> resolution needs 
> to be at least 2x the number of pixels on each axis (i.e. 4x 
> the pixels 
> of the input signal).
> 

Could it be that you are thinking of the
Nyquist-Shannon sampling theorem?
http://en.wikipedia.org/wiki/Nyquist-Shannon_sampling_theorem

Not sure if that it should be used as you have described it though,
assuming we are speaking of a broadcast stream.

Your statement above would imply that a 256x100 would be more
fully represented (better quality) on a 768x300 than on a 256x300.


> Boiled down to basics, there's a difference between image 
> pixels (which 
> are truly "picture elements"--samples of a picture at a point 
> (of zero 
> size)) and display "pixels" (which are really "dots"--that have a 
> physical area).  The picture elements are created by sampling a 
> continuously-defined image function, and, although you can display an 
> image by painting pixels of the same value and at the same positions 
> used to generate the picture elements (i.e. "1:1 pixel mapping"), you 
> can create a much better image by recreating the image function and 
> taking more samples at different positions and incorporating the 
> additional information about the image function into the 
> final display 
> pixel values.

That is the problem, you cannot take more samples, only interpolate new
values.
What you are describing above is a 2:1 mapping. 

> 
> Unfortunately, there aren't many good sources on the 'net.  Why?  Who 
> knows?  Perhaps computer programmers are too smart to be 
> fooled by all 
> those complex mathematical formulae.  Fortunately, though, the ideas 
> have been incorporated into the algorithms we use everyday (in 
> image-processing libraries, in printers/printer drivers, and even in 
> graphics hardware).

Aren't they doing the opposite? More samples to create fewer dots?






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