[Kst] extragear/graphics/kst/plugins

Barth Netterfield netterfield at physics.utoronto.ca
Tue Nov 22 19:23:17 CET 2005

Is this an IIR filter implementation?  Or FIR?  FIR can be pretty slow for 
large SR to cutoff ratios (though there are some special case exceptions, 
like sequential boxcars).  IIRs can quickly become unstable.

Can you provide a reference (pref online) for how this filter implementation 
works?  Over what range of coefficients is it stable?

On November 22, 2005 12:46 pm, Nicolas Brisset wrote:
> Yet another nice plugin. That one takes two strings containing the
> numerator and denominator filter coefficients (in continuous time),
> discretizes the filter and computes it step by step. You can input any kind
> of filter, even though once again it would be more convenient to be able to
> provide a more intelligent widget that would generate the coefficients
> according to filter type, family, and order... 
> [....]
> - should be extremely fast as they compute the result directly in the time
> domain without the need for a fft + computation + inverse fft - will be
> causal (which is not the case right now)

But will not be zero phase shift (which is the case right now).

You always have a choice: causal, with a phase shift (which can be fairly 
flat, eg, Bessel filter, or a symetric time domain FIR, or really whacky, 
like a Butterworth, or any IIR), or acausal, but zero phase, as with our 
current fourier implimentation.

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