Can't Update Filter IIR::Coeffs In Plugin?

Audio Plugins
1

Hi there,

I know this may be a stupid question but i have been rooting around on this site for days and days now trying to find an answer to why i cant seem to update my IIR::filters mid session after opening my plugin. I think the problem lies within when and where im trying to update them but i cannot find a working way of doing it at all. So where and how would one update these filters?

Any help would be appreciated.

in Processor.h: (This is the type of filter etc that i am using)

private:
OwnedArray<dsp::IIR::Coefficients<float>>    m_Low_LoMid_XOArray;
OwnedArray<dsp::IIR::Coefficients<float>>    m_LoMid_Mid_XOArray;
OwnedArray<dsp::IIR::Coefficients<float>>    m_Mid_MidHi_XOArray;
OwnedArray<dsp::IIR::Coefficients<float>>    m_MidHi_High_XOArray;

dsp::ProcessorDuplicator<dsp::IIR::Filter<float>, dsp::IIR::Coefficients<float>>Low_LP;
dsp::ProcessorDuplicator<dsp::IIR::Filter<float>, dsp::IIR::Coefficients<float>>Low_LP2;

in Processor.cpp: (This function seems to work fine upon prepare to play etc)

void DistortionTest2AudioProcessor::UpdateFilters()
{
//Inbuilt, comment out to use GUI Update
_Low_MidLoXO = *TreeState.getRawParameterValue("F1");
_MidLo_MidXO = *TreeState.getRawParameterValue("F2");
_Mid_MidHiXO = *TreeState.getRawParameterValue("F3");
_MidHi_HighXO = *TreeState.getRawParameterValue("F4");

//Dont change
float f1 = _Low_MidLoXO;
float f2 = _MidLo_MidXO;
float f3 = _Mid_MidHiXO;
float f4 = _MidHi_HighXO;

if (bands >= 2) //Per band
{
	ReferenceCountedArray<dsp::IIR::Coefficients<float>> Low_LPCoeffs = dsp::FilterDesign<float>::designIIRLowpassHighOrderButterworthMethod(f1, SampRate, 1); //Create a butterworth filter coeff structure
	ReferenceCountedArray<dsp::IIR::Coefficients<float>> LoMid_HPCoeffs = dsp::FilterDesign<float>::designIIRHighpassHighOrderButterworthMethod(f1, SampRate, 1); //and the opposing highpass

	for (auto Coeff : Low_LPCoeffs)
		m_Low_LoMid_XOArray.add(new dsp::IIR::Coefficients<float>(*Coeff)); //Add those coeffs to an array per xo

	for (auto Coeff : LoMid_HPCoeffs)
		m_Low_LoMid_XOArray.add(new dsp::IIR::Coefficients<float>(*Coeff));

	*Low_LP.state = *m_Low_LoMid_XOArray[0]; //update the xo's filters with the new coeffs (one coeff per pair)
	*Low_LP2.state = *m_Low_LoMid_XOArray[0];
	*LoMid_HP.state = *m_Low_LoMid_XOArray[1];
	*LoMid_HP2.state = *m_Low_LoMid_XOArray[1];

Editor.cpp: (The issue i think is finding the right place for the call? But it doesnt work here which i thought it should.)

void DistortionTest2AudioProcessorEditor::FreqChange()
{
processor.UpdateFilters();
}

Like i say sorry for such a stupid question but if anyone knows where i am going wrong or can point me towards the correct resource i’d be appreciative.

Thanks again,
Sulkyoptimism

2

Hi! Did you ever get to the bottom of this? Also hitting this wall trying to change the coefficients of Butterworth filters!

3

I cant quite remember, it was a university project so its been long forgotten, but i think i ended up using other filter types in JUCE, i’ll have a look for the code now. But no promises i can find it.

4

Thanks! That would be amazing.