Reply To: Gen PhaseVocoder Sound Quality issues
Strictly speaking the @interp none/step shouldn’t change the sound, so long as the delay times coming in are integers (should be). But @interp none/step will probably be more efficient; I’ll change the gen examples accordingly. (For anyone reading, @interp none and @interp step are synonyms, they have the same effect.)
I’m not sure if @feedback 1 is really needed either; this is the default for [delay]. Specifying [delay @feedback 0] has two effects: 1) it does not allow direct signal feedback in the patcher, and 2) it allows delay times less than 1 sample. In a pfft context however, 1 sample delay equates to a frequency shift by 1 bin. If no frequency shifting is desired, the minimum practical delay time is depends on the FFT frame size.
I’ve found that using framedelta/frameaccum is ‘sharp’ as long as there is no time/freq shift, but once shifted it becomes blurry, and removing the shift does not remove the blurriness. Presumably this is because although the phase derivatives (angular momenta?) of the bins agree, the absolute phases are no longer in sync. I confess I don’t totally understand it though…