FFT-windowing applications: why does we use index~ ???

Feb 8, 2011 at 2:01pm

FFT-windowing applications: why does we use index~ ???

Hi all , thanks for your suggestions.

Two question please:

1) I know index~ doesn’t makes interpolation. Does it means interpolations between two samples?

2) Why we don’t need interpolation for FFT-windowing applications?

Thank you very much in advance…
fv

#54859
Feb 8, 2011 at 3:21pm

Hi Federico,

index~ just gives you the value that is in memory at the address specified by the index.
If you want to playback the content of an audio buffer with variable speed, you will probably desire some interpolation between samples, thus you wouldn’t use index~.

question 2 is not very clear… Do you refer to a specific patch / tutorial ? If you look in the [index~] help file, there is a use of index~ to access the content of a “buffer~”. Here, the data that’s in the buffer may be many things, like the envelope of a filter – see famous example “forbidden-planet”.

Jean-Francois.

#197561
Feb 8, 2011 at 4:39pm

Thank you Jean-Francois,
I do refer to the phase vocoder patch by Dudas and Lippe. Another question for you, pleae. I don’t understand why with an FFT overlap of 4 we get a velocity 4 time faster (the reason because we need an input coefficient of 0.25)…
I know what is the overlap but I don’t know why we get a velocity 4 time faster….
Could you please help me.
Thanks
fv

#197562

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