[PD] Spectrum graphing amplitude problem

[Ed Kelly]

It is really just the pixel-resolution of the graph. The graph size is 252, but the FFT size is 4096 ( giving 2049 points within the Nyquist frequency ).
So you will see magnitude peaks between the pixels as lower amplitude because the screen doesn't display pixels between pixels.
I hope this makes sense,

Ed
 
Lone Shark "Aviation" out now on http://www.pyramidtransmissions.com
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----- Original Message ----
From: Jason Plumb <jason at noisybox.net>
To: pd-list <pd-list at iem.at>
Sent: Sunday, 21 October, 2007 6:06:53 AM
Subject: [PD] Spectrum graphing amplitude problem

Hi.

I'm building a super simple but reconfigurable GOP spectrum graphing 
abstraction, but got some weird behavior early on.  Please see my
 example:

http://noisybox.net/computers/pd/questions/freq_graph_work3.pd

The magnitude computation and dividing by the block size I got from one
 
of the help examples.  It's almost doing the right thing -- if you drag
 
the slider around the single frequency peak moves around.  The problem 
is that the peak amplitude, as graphed, changes based on the frequency.
 
  It even seems to be periodic WRT frequency, which makes me think 
there's a kooky phase issue...

Any ideas?

Thanks,

-jason
http://noisybox.net

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