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https://github.com/thestk/stk
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81 lines
2.2 KiB
C++
81 lines
2.2 KiB
C++
/*******************************************/
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/* BiQuad (2-pole, 2-zero) Filter Class, */
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/* by Perry R. Cook, 1995-96 */
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/* See books on filters to understand */
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/* more about how this works. Nothing */
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/* out of the ordinary in this version. */
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/*******************************************/
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#include "BiQuad.h"
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BiQuad :: BiQuad() : Filter()
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{
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inputs = (MY_FLOAT *) malloc(2 * MY_FLOAT_SIZE);
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zeroCoeffs[0] = (MY_FLOAT) 0.0;
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zeroCoeffs[1] = (MY_FLOAT) 0.0;
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poleCoeffs[0] = (MY_FLOAT) 0.0;
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poleCoeffs[1] = (MY_FLOAT) 0.0;
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gain = (MY_FLOAT) 1.0;
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this->clear();
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}
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BiQuad :: ~BiQuad()
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{
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free(inputs);
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}
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void BiQuad :: clear()
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{
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inputs[0] = (MY_FLOAT) 0.0;
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inputs[1] = (MY_FLOAT) 0.0;
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lastOutput = (MY_FLOAT) 0.0;
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}
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void BiQuad :: setPoleCoeffs(MY_FLOAT *coeffs)
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{
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poleCoeffs[0] = coeffs[0];
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poleCoeffs[1] = coeffs[1];
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}
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void BiQuad :: setZeroCoeffs(MY_FLOAT *coeffs)
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{
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zeroCoeffs[0] = coeffs[0];
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zeroCoeffs[1] = coeffs[1];
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}
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void BiQuad :: setFreqAndReson(MY_FLOAT freq, MY_FLOAT reson)
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{
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poleCoeffs[1] = - (reson * reson);
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poleCoeffs[0] = (MY_FLOAT) 2.0 * reson * (MY_FLOAT) cos(TWO_PI * freq / SRATE);
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}
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void BiQuad :: setEqualGainZeroes()
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{
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zeroCoeffs[1] = (MY_FLOAT) -1.0;
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zeroCoeffs[0] = (MY_FLOAT) 0.0;
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}
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void BiQuad :: setGain(MY_FLOAT aValue)
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{
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gain = aValue;
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}
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MY_FLOAT BiQuad :: tick(MY_FLOAT sample) /* Perform Filter Operation */
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{ /* Biquad is two pole, two zero filter */
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MY_FLOAT temp; /* Look it up in your favorite DSP text */
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temp = sample * gain; /* Here's the math for the */
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temp += inputs[0] * poleCoeffs[0]; /* version which implements */
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temp += inputs[1] * poleCoeffs[1]; /* only 2 state variables. */
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lastOutput = temp; /* This form takes */
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lastOutput += (inputs[0] * zeroCoeffs[0]); /* 5 multiplies and */
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lastOutput += (inputs[1] * zeroCoeffs[1]); /* 4 adds */
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inputs[1] = inputs[0]; /* and 3 moves */
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inputs[0] = temp; /* like the 2 state-var form*/
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return lastOutput;
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}
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