[PD] Smooth looping

Frank Barknecht fbar at footils.org
Sun Apr 25 10:52:11 CEST 2010


On Sat, Apr 24, 2010 at 12:12:08PM -0400, Matt Barber wrote:
> I don't do very much looping, but if intuition serves I think you need
> to find loop points that share both the same value and the same first
> derivative (if your source is more or less periodic you can think of
> this as looping several sine waves and then mixing the results, and
> though I haven't thought it through it seems like the value and
> derivative would match best in places where the phase is similar for
> each constituent at the loop points).  When I've tried to do looping,
> I've found it a little easier to find peaks with similar values,
> because I know that the derivative is the same at those peaks, while
> it's much harder to estimate the rate of change on zero-crossings.
> Anyway, for the sample you posted the best loop-point I could find was
> 2931-6153.

What irritates me is this "knocking" sound when the phasor loops back to
the beginning, which happens even with your settings, although they set
the loop to happen at places where the sample data is almost the same
over the 256 samples that lie 128 samples before and after the loop
start and end points as the overlaid arrays indicate. I'd assume that
the derivatives are sufficiently similar there, and tdditionally he
knocking doesn't sound like a click coming from a discontinuity. 

OTOH the same sound is heard when using for example the [susloop~]
external, so maybe it's indeed in the sample data.


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