[PD] fourier transform of low-frequency signal

Johannes M Zmoelnig zmoelnig at iem.at
Mon Nov 22 15:52:02 CET 2004

" <f.bardet at voila.fr> wrote:
> Hi list,
> I need to analyse the low-frequency (1 to 5 Hz) content of a non-audio signal.
> So I'd like to proces Fourier Transform of my low-frequency, low sampled signal, within PD.
> As my incoming signal is low-sampled at 25Hz (coming from a camera), i think i can't use fft objects designed for audio processing.
> Do i have to rewrite an fft algorithm within pd, for low-frequency processing, or does this exist yet ?
> Has anyone built such a process in PD ?

there might be 2 ways of doing that:
1) signal-domain: you can downsample a signal with [block~] (see 
3.audio.examples/J09.up.downsampling.pd) and use the [rfft~]-object
2) message-domain: i think (but have no idea whether this has already 
been done by thomas; and i don't know whether he has released it yet) 
that the iemtab-library allows the fft of a table to be calculated. 
probably there are some other externals that allow fft's on tables (e.g. 
message data)


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