[PD] Fractional Delay in PD

[katja]

Hello Aaron,

Tried your test patch and here it does not produce the noise you
describe. If delay is set to absolute values larger than 1 it produces
too large signal values leading to clipping and harmonics, but this is
to be expected considering the way the patch is built. I noticed that
resulting coefficients were not consistent because you did not use the
trigger object in the calculation subpatches to organize the order of
operations.

With the trigger objects inserted, the FIR calculator seems to work
well. I've added sliders in the subpatch to visually verify
coefficient values, see attached. Also if you check with white noise
as input signal, you can hear the spectrum is unaltered no matter what
fractional delay. So, very much OK. Thanks for the patch!

By the way I've once made a visualization of fractional delay with
sinc kernel, if you're interested I can try to find it.

Katja

On Mon, Oct 1, 2012 at 10:32 PM, Aaron Thompson
<aaron.thompson at live.co.uk> wrote:
>
> Hello community,
>
> Having trouble getting my lagrange 4-point interpolator to function properly. Harmonics are being generated from somewhere, possibly due to the amplitude exceeding FSD (DC offset?). When I then include it in my waveguide, as soon as DSP is enabled, pd beeps, and then leaves crackly noise/fuzz regardless of whether the patch is being fed an audio signal or not. Remove the FIR filters, and it functions again as normal.
>
> Interested to know how others have achieved fractional delay filters within pd, be it Lagrange or Thiran Allpass for example.
>
> Patch is attached, "FIRTest.pd" is the parent patch.
>
> Any help would be greatly appreciated.
>
> Aaron
>
> _______________________________________________
> Pd-list at iem.at mailing list
> UNSUBSCRIBE and account-management -> http://lists.puredata.info/listinfo/pd-list
>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: FIRTest2.zip
Type: application/zip
Size: 5503 bytes
Desc: not available
URL: <http://lists.puredata.info/pipermail/pd-list/attachments/20121002/0b39f629/attachment.zip>