I'm doing a research project involving phase vocoders and looking at 09.pvoc.pd in the example patches as a reference implementation. I was wondering if anyone could help me to understand it. Specifically, how is the "instantaneous frequency", obtained by comparing phases in successive frames, used? What is the relationship between the two segments of the source array that are read at the same time and the phase-real, phase-imag arrays?
I basically understand the procedure outlined in Computer Music Tutorial (Roads) on pages 1105-6:
instantaneous frequency 6. apply any modifications (time-stretch, pitch-shift, etc) 7. IFFT 8. window again if phase spectrum was altered 9. overlap-add the output frames
but step 6 is sketchy, and I don't understand how the instantaneous frequency is actually *used* in resynthesis. Any help would be appreciated.
Thanks, Ben