[PD] Nerdy Phase Vocoder question or remark
Alexandre Torres Porres
porres at gmail.com
Sun Dec 11 04:55:59 CET 2011
Hi there. I've been opening the guts of the phase vocoder patches for a
while now, and rewriting them, having it in new forms, etc...
And... today I had this doubr. You see, lets have the regular I07 example.
Now, we feed [line~] objects with where to start and where to go in a time
specified as the FFT analysis Hop size in ms.
I was wondering if that wasn't just too fast. And why wasn't the time for
[line~] the actual window size in ms. That is because I assumed this
[line~] controlled somehow the speed playback we hear.
So I put a number box and started messing around with it, making it a
bigger time lenght and hoped to listen to some sound change (maybe speed),
just for fun. To my surprise, nothing happened!!! That is until I reached
two overlaps (1024 points instead of 512).
So instead of making anything clearer than it was, it got pretty much more
weird. I decreased the values until reaching a supidly small time inteval
of micro ms, something like 2.26e-07, and it still worked!!!
I now have the clear idea that this length in ms is not that important at
all. But that it has to be fast just to make line output the audio so it
gets in the FFT. If it takes to long (2 overlaps or longer) it ruins
everything. But what really controls the thing is the time interval defined
by the counter which is controlled by the speed parameter.
[line~] needs to feed the [tabread4~] output at a rather free way.
Anyway, some nerdy remark. I'd like to understand this better, and explain
this better in my rewriting of the patches.
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