dsp::IIR::Filter: noise/glitches when automating frequency via (slow) LFO

[zsliu98]

@dfilaretti

Yeah my CPU goes from 1% (which is already a lot I guess) if I update the filter every 100 samples, to about 7% if I update the filter at each sample. Definitely something wrong there

In my processBlock I actually use juce::dsp::IIR::Coefficients<float>::makePeakFilter to generate the new coefficients every time, could that be part of the problem? But if I’m not supposed to use makePeakFilter inside processBlock, what should I use instead?

That CPU usage is abnormal. Never use juce::dsp::IIR::Coefficients<float>::makePeakFilter in processBlock. Use ArrayCoefficients instead. See more info at:

Non-allocating alternatives for the IIR::Coefficients::make... functions

Yes, the ArrayCoefficients functions are designed so that they do not need to allocate.

BTW, I see about 5~10% reduction in CPU usage if I use my own IIR filter (basically copy most code from juce::dsp::IIR and remove some redundant checks).