[PD] Spectrum graphing amplitude problem

Ed Kelly morph_2016 at yahoo.co.uk
Sun Oct 21 21:31:38 CEST 2007

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,

Lone Shark "Aviation" out now on http://www.pyramidtransmissions.com

----- 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


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


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?



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