[PD] object name and anti aliasing technique : WAS : Re: better tabread4~

Charles Henry czhenry at gmail.com
Fri Jun 27 06:53:04 CEST 2008

On Thu, Jun 26, 2008 at 12:36 PM, cyrille henry
<cyrille.henry at la-kitchen.fr> wrote:

> then, it's possibile to have interpolation using more points, and also
> interpolation that offer antialiasing.
> BTW : i just commited a tabosc4aa~ (aa is for anti aliasing).
> this is also just a test.
> it's far from perfect, but lot's better than the original tabread4~ when
> dealing with high pitch transposition.
> for now, i did this with a classic 8x upsampling + biquad filter inside the
> tabread4aa~ (ok, this is more cpu intensive : about 1 to 1.5 % cpu)
> before i'm doing more work on this, did anyone have experience with this?

To me, the upsampling is not a good approach for anti-aliasing.  This
means, you have to interpolate, then filter, then sample again.

But you will wind up applying your filter at a lot of points, which
will just be discarded.

In fewer steps, (I think) we can modify the interpolation function
continuously as the speed changes.  Rather than filtering on a long
signal, just filter it in place.  The part that gets tricky is that
the DFT is a lot less relevant, and you have to rely upon continuous
functions instead.

I didn't make any progress today... and friday is gone for sure :)  I
will calculate the spectrum for tabread4c~ on Saturday, I think.

I'm down with the project, but I can't really see the big picture for
a tabread/vd/tabosc lib yet.


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