Can zp2sos be used in an audio plugin?

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Nathan Lively
Nathan Lively el 7 de Mayo de 2021
Respondida: Nathan Lively el 11 de Mayo de 2021
I'm getting this error:
Unable to perform assignment because dot indexing is not supported for
variables of this type.
Error in filterPlugin/reset (line 21)
p.sos = zp2sos(z,p,k);
Here's my plugin code. I'm trying to keep it super simple for testing.
classdef filterPlugin < audioPlugin
% Basic IIR Butterworth lowpass for testing
properties % Public interface
end
properties (Constant) % Define the plugin interface
PluginInterface = audioPluginInterface();
end
properties (Access = private) % Internal State
sos = zeros(1,6);
end
methods
function out = process(p, in)
[out] = sosfilt(p.sos,in);
end
function reset(p) % Initialize internal state
Fs = getSampleRate(p);
Fc = 1000; FcNormalized = Fc/(Fs/2);
[z,p,k] = butter(2,FcNormalized);
p.sos = zp2sos(z,p,k);
end
end
end
  2 comentarios
Nathan Lively
Nathan Lively el 7 de Mayo de 2021
Here's the console.
Nathan Lively
Nathan Lively el 7 de Mayo de 2021
And here's the original MATLAB code used to make the plugin.
Fs = 48000;
Fc = 1000;
FcNormalized = Fc/(Fs/2);
[z,p,k] = butter(2,FcNormalized);
sos = zp2sos(z,p,k);
% out = sosfilt(sos,y);
fvtool(sos)

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Respuesta aceptada

Nathan Lively
Nathan Lively el 11 de Mayo de 2021
Go to Digital and Analog Filters — Functions section and filter it by C/C++ code generation and you will find that zp2sos is not supported.

Más respuestas (1)

Asvin Kumar
Asvin Kumar el 10 de Mayo de 2021
The reason this error occurs is because you're using p as the "this" input argument and then overwriting it by the output of the butter function which is a column vector of complex numbers. Hence why the assignment fails. Use a modified version of the reset function to workaround this error.
function reset(this) % Initialize internal state
Fs = getSampleRate(this);
Fc = 1000;
FcNormalized = Fc/(Fs/2);
[z,p,k] = butter(2,FcNormalized);
this.sos = zp2sos(z,p,k);
end
  4 comentarios
Asvin Kumar
Asvin Kumar el 11 de Mayo de 2021
You can find details about functions that support code generation from the Signal Processing Toolbox here: Code Generation and GPU Support - MATLAB & Simulink (mathworks.com)
Nathan Lively
Nathan Lively el 11 de Mayo de 2021
Thanks so much Asvin!

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