Tutorials and Topics - Peabody Computer Music

Tutorial 26Frequency domain signalprocessing using pfft~displays the first sample in the signal vector, which in this case will always be 0. To see thecenter frequency values, you will need to use the capture~ object or record this signal intoa buffer~.Once you know the frequency of the bins being streamed out of fftin~, you can performoperations on the FFT data based on frequency. For example:A simple spectral crossover.The above pfft~ subpatch, called xover~, takes an input signal and sends the analysis datato one of two fftout~ objects based on a crossover frequency. The crossover frequency issent to the pfft~ subpatch by using the in object, which passes max messages throughfrom the parent patch via the pfft~ object’s right inlet. The center frequency of the currentbin — determined by the sync outlet in conjunction with fftinfo~ and dspstate~ as wementioned above — is compared with the crossover frequency.The result of this comparison flips a gate that sends the FFT data to one of the two fftout~objects: the part of the spectrum that is lower in pitch than the crossover frequency is sent208