[PD] Some VASP questions

Larry Troxler lt at westnet.com
Mon Nov 10 00:11:33 CET 2003

Hi, I have some questions about, guess what? - VASP!

I'm trying to put together a simple FFT scope.

Here are some things I'm not sure about.

First, How should I use the "detach" message, assuming that i want my scope to 
run always in a seperate thread (so that there's no issues in switching it 
back and forth)? Should I send the "detach" message first, before starting 

Next, "vasp.window" apparently doesn't handle the "to" message, so how do I 
deal with that? I thought the approach would be to chain all the objects to 
gether and send the first one a "to" message to set the source and 
destination arrays, and everything would be well.

Now about the fft stuff - I am not sure what vasp.rfft does actually. It seems 
like that's what I want to use, becuase I'm dealing with an audio signal. But 
what does it output, and how does that map into a PD array? Is it generating 
the full complex FFT, including the redundant conjugates? And are only the 
real compenents of this making it to the arrary, or is there a mag operation 
done before writing to the array? And if so, is there a way that I can write 
only the magnitudes of the first half of the output to my array?

IOW basically, for an FFT of a real signal, I only want the first half, so my 
output array should be half the length of the input array. And for simple 
energy plot, each point in the array should be the magnitude vector of the 
corresponding point in the FFT.

Is this somehow what is already done, or do I need to do something else to 
accomplish this?

Thanks in advance!


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