ScaleValues property error in designing a filter with designParamEQ and dsp.BiquadFilter

Hello everyone,

I'm trying to design a filter with dsp.BiquadFilter and designParamEQ in MATLAB R2020a. I get the following error message:

Error using BiquadFilter/BiquadFilter.setParameters

The ScaleValues property value must be either a scalar or a vector of length one greater than the number of sections.

I'm designing twelve parametric equalizers for a certain frequency (FreqVector) and amplitude (GVector), which I want to cascade and apply to a stereo signal (two channels). Here's my current code:

rma = zeros(3,12);
rmb = zeros(2,12);

for ii=1:12
    [rma(:,ii), rmb(:,ii)] = designParamEQ(N1,GVector(ii,:),FreqVector(ii,:),BW);
end

BiquadFilter1 = dsp.BiquadFilter('SOSMatrix',[rma(1).',[1,rmb(1).']]);
BiquadFilter2 = dsp.BiquadFilter('SOSMatrix',[rma(2).',[1,rmb(2).']]);
% ...

[AllBiquads] = dsp.FilterCascade(BiquadFilter1, BiquadFilter2, BiquadFilter3, BiquadFilter4, BiquadFilter5, BiquadFilter6, BiquadFilter7, BiquadFilter8, BiquadFilter9, BiquadFilter10, BiquadFilter11, BiquadFilter12);

for ii=1:2
    y(ii,:) = AllBiquads(in(ii,:));
end

Here's the complete error message that I get:

Error using BiquadFilter/BiquadFilter.setParameters

The ScaleValues property value must be either a scalar or a vector of length one greater than the number of sections.

Error in dsp.BiquadFilter/setParameters

Error in dsp.FilterCascade/getNumInputsImpl (line 614)

n = getNumInputs(obj.Stage1);

Error in prototype_25012021 (line 207)

y(ii,:) = AllBiquads(in(ii)); - Show complete stack trace

What's wrong here? Any ideas how to solve my problem?

Answer 1

[jibrahim]

Hi Patrick,

I can't run your code because certain variables are missing (N1, GVector, in, out, etc), but in R2020a, this code should give you a dsp.BiquadFilter:

Fs    = 48e3;
N     = [2,   4];
G     = [6,  -4];
Noct  = [1.5, 1];
Q     = sqrt(2.^Noct)./(2.^Noct-1); % Q factors
Wo    = [100 5000]/(Fs/2);
BW    = Wo./Q;

[B,A] = designParamEQ(N,G,Wo,BW,'Orientation','row');

bqd = dsp.BiquadFilter('SOSMatrix',[B,A]);
bqd(1) % works

f = dsp.FilterCascade(bqd,bqd);
f(1) % works

[Patrick Boettcher]

Thanks! I found the mistake myself, I was adressed the wrong lines, because I have a vector matrix. It has to be:

BiquadFilter1 = dsp.BiquadFilter('SOSMatrix',[rma(:,1).',[1,rmb(:,1).']]);
BiquadFilter2 = dsp.BiquadFilter('SOSMatrix',[rma(:,2).',[1,rmb(:,2).']]);