[PD] is this a spectral gate?

Tom Erbe tre at music.ucsd.edu
Thu Feb 22 16:42:56 CET 2007

Yes, this is true. For many FFT based effects (like spectral gates),  
you don't really need to convert completely to polar (this conversion  
can be more expensive than the FFT).

For a spectral gate, just calculate the amplitude from real and imag,  
make your gate decision based on the amplitude and threshold, and  
then apply the same gain reduction to both real and imag. Add attack  
and release to the gate-gain for smoother results.

Or even quicker, avoid the sqrt in amplitude calculation, and use a  
squared threshold to compare against the squared amplitude.

On Feb 21, 2007, at 11:33 PM, Frank Barknecht wrote:

> I also think, that the algorithm to
> calculate the Fourier transform, the Fast-FT or FFT, generates re/im
> pairs, so skipping the final conversion to polar unless necessary
> is faster.

- - - - -
tom erbe ~ tre at ucsd.edu ~ studio director ~ ucsd department of music

More information about the Pd-list mailing list