Tutorials and Topics - Peabody Computer Music

Tutorial 26Frequency domain signalprocessing using pfft~This analysis/resynthesis scheme (using overlapping, windowed slices of time with theFFT and IFFT) is usually referred to as a Short Term (or Short Time) Fourier Transform(STFT). An STFT can be designed in MSP by creating a patch that uses one or more pairsof fft~/ifft~ objects with the input signal “windowed” into and out of the frequencydomain. While this approach works fairly well, it is somewhat cumbersome to programsince every operation performed in the frequency domain needs to be duplicatedcorrectly for each fft~/ifft~ pair. The following subpatch illustrates how one wouldwindow incoming FFT data in this manner:How to properly window audio for use with the fft~ objectIn addition to the fact that this approach can often be a challenge to program, there is alsothe difficulty of generalizing the patch for multiple combinations of FFT size and overlap.Since the arguments to fft~/ifft~ for FFT frame size and overlap can’t be changed,202