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
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----- Original Message ---- From: Jason Plumb jason@noisybox.net To: pd-list pd-list@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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