[mythtv-users] Graphics card recomendation

George Roberts gr at gr5.org
Thu Aug 31 18:34:52 UTC 2006

>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).

I suspect you are confusing this with nyquist sampling theory.  If you want to
sample a signal and want to be able to detect signals up to 1MHz
then you need to take 2 million samples per second - double
the frequency that you want to get up to.  This is so you get the
high and low of each wave.

After you take the samples, you don't need to play it back at 4 million
samples per second, you can play it back at 2 million samples per
second to be able to show signals up to 1MHz.  This applies to audio,
video, and other types of signals.

In other words, if you have an image that is 1920 pixels wide then
a display that is 1920 pixels wide is no worse than a display that
is 3840 pixels wide.

Or maybe you are confusing this with signal processing?  If you want to
do certain image manipulation with a digitized photo it is occasionally
better to double up the pixels before doing the processing.

- George Roberts

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