[PD] convolution weirdness

Charles Henry czhenry at gmail.com
Sun Nov 5 23:17:38 CET 2006


Hi, list,
  I have practically abandoned the idea of making a subband adaptive
filter scheme using externals, but have not given up on making a
Newton-method, rather than a gradient descent method (Fourier
deconvolution is a Newton method, for instance, LMS and NLMS is a
gradient descent method).

So, I've written the convolution routine and it works mostly.  There
is a high frequency component of the error that doesn't make sense to
me.  All I did was the complex multiplication of two fft's, and it
seems like it's not handling the Nyquist frequency well.  Any ideas?

Also, I wondered if there would be a way to move a block of samples
(in this patch length 2*L) within a block of samples length 2*N, from
the end of the block to the beginning of the block.  This would reduce
latency of the filter patch (currently 2*N-L) to L (samples).  N is
the filter length, and L is the intended latency.

I've attached the patch, as is, where you can see the high-freq.
weirdness that goes on.  Just turn on the filter using the toggle box
above [s f_on$0] and hit the message [256 64], in that order.

Any suggestions would be gratefully recieved!
Chuck




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