[PD] Weird Crazy Behaviour of Phase Vocoder Example in PD

Alexandre Torres Porres porres at gmail.com
Tue Jul 24 02:48:50 CEST 2012

Hi there, get this, there's something crazy going on with the Phase Vocoder
example in PD, and I have no idea why.

After years of building a super patch on top of the phase vocoder example
in PD, I stumbled upon a very/weird/crazy ugly bug. After struggling my
brain over days on it I went back to inumerous versions of my patch, even
back to 2008, and kept finding the same crazy behaviour I never had noticed
before. So I went to the very source and found it there too!

So here it is the original PD patch, that comes as an example with PD and
everything. I made just a couple of very *MINOR* adaptations to test the
bug. All I do is resize the sample array to 1 minute, then I start
recording an oscillator in it, and half a second later I start playing it
at normal speed (100).

Get the patch here

click on the collored bang and just wait for it.

Now check at the location atom box how - at around 47500 (47 seconds and a
half) - the whole thing gets ruined. I'm making a very big shift to 3
octaves below so it's clearer how it all gets screwed up and dropped even
lower all of a sudden so you cannot even hear it anymore.

This is an extremely crazy behaviour which I have no explanation
whatsoever, and keeps making me doubt about the very laws of physics
themselves. By the way, I was recording other stuff in my current patch
that I've been tweeking with over years and at around 47.5sec the same
thing happens... my patch can loop around the recorded buffer, and same
stuff happens when I read over it again... and also at diferent pitch
shifts... but somehow it sounds "ok" at 0 shift, so I can see that the
Phase Vocoder actually stops working somehow. Now it seems this has
something to do with some drawback and limitation of some of the objects
involved, such as [tabread4~] or something. But I just dont know them that
well to grasp the reason why.

I hope some enlightened soul sheds some light to this puzzle and restores
my faith in reality and the universe as we usually see it.

Thanks a lot.
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