A UGen performing short-time forward fourier transformations. In order to
properly link the spectral ugens ( PV_... ), you should begin by using the
output of each UGen (which is just the fft buffer identifier), and use that as
buffer input of the next UGen. That way, the UGen graph is correctly sorted.
E.g. IFFT(PV_...(FFT(buf, in))) .
The UGen will initially output zero until the first FFT can be performed. This
is the case after hop * fftSize . Thus for a default fft buffer size of 1024
and a hop of 0.5, and for a default control block size of 64, for the first
1024*0.5/64 = 8 control blocks the UGen will output zero. This also implies that
the first FFT in this case if performed on the first 512 samples of the in
signal (prepended by 512 zeros). In other words, the first 'full' FFT of the
input happens after fftSize/controlBlockSize cycles, no matter what hop size was
chosen.
If you use FFT for performing signal analysis and not phase vocoder effects, make sure you change the window type accordingly.
- Value Params
- active
This parameter can be temporarily set to <= 0 to pause the FFT operation.
- buf
The buffer to use for writing the FFT to. The size must be a power of two. Since
FFToperates at control rate (also being a power of two), the buffer should probably be at least as long as the control block size. ''(init-time only)''- hop
A factor determining the step size between successive FFTs. That is, FFTs are performed every fftSize * hop sample frames. The default of 0.5 means thus a 50% overlap, while a hope of 1.0 means no overlapping. Choosing 0.0 will most likely crash the server! ''(init-time only)''
- in
The time domain signal to be transformed into the spectral domain.
- winSize
With the default value of zero, the window size equals the fft size. If you wish to perform zero padding, an explicit window size can be specified. ''(init-time only)''
- winType
The window function applied before each FFT is taken. The default of
0is a sine window which is good for phase vocoder applications (using thePV_...UGens). For analysis applications, you may want to use-1which is a rectangle window (effectively no windowing) or1which is a Hann window. A Hann window gives perfect overlap-add reconstruction for a hope size of 0.5 (or 0.25 etc.) ''(init-time only)''
- See also
- Companion
- object