[Pd] Complex audio signals

[Piotr Majdak]

Hi chucck,

Chuckk Hubbard wrote:

> On 6/20/06, Piotr Majdak <piotr at majdak.com> wrote:
> 
> If I understand you correctly, this is similar to what Miller's book
> talks about.  Pairing every complex filter with another with the
> conjugate of its coefficient, so that the real signal can be treated
> as the sum of two complex signals which are conjugates of each other.
> Hallelujah, I just made it work.  Not so hard.  Far easier than trying
> to make a real signal complex.

Glad to hear it!

> Writing the original signal and the real and imaginary parts of the
> output to graphs shows lots of alterations.  It is fine with a block
> containing an integer number of cycles, but otherwise gets weird
> results.  See attached.

Every time you write the signals to the tables, the phase of the original signal 
changes. Because of the windowing effects the processed signal (FT->Re{}->IFT) 
changes dramatically: the real part of the FT result contains the information 
about the symmetric part of the original signal (=cosines), which changes with 
its phase.

Thanks for the nice example - it took me a while to analyze what happens here.

br, Piotr


-- 
Piotr Majdak
Institut für Schallforschung
Österreichische Akademie der Wissenschaften
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E-Mail: piotr at majdak.com
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