#include "pt2_math.h"#include "pt2_rcfilters.h" #define SMALL_NUMBER (1E-4) /* 1-pole RC low-pass/high-pass filter, based on:** https://www.musicdsp.org/en/latest/Filters/116-one-pole-lp-and-hp.html*/ void setupOnePoleFilter(double audioRate, double cutOff, onePoleFilter_t *f){ if (cutOff >= audioRate/2.0) cutOff = (audioRate/2.0) - SMALL_NUMBER; const double a = 2.0 - pt2_cos((PT2_TWO_PI * cutOff) / audioRate); const double b = a - pt2_sqrt((a * a) - 1.0); f->a1 = 1.0 - b; f->a2 = b;} void clearOnePoleFilterState(onePoleFilter_t *f){ f->tmpL = f->tmpR = 0.0;} void onePoleLPFilter(onePoleFilter_t *f, const double in, double *out){ f->tmpL = (f->a1 * in) + (f->a2 * f->tmpL); *out = f->tmpL;} void onePoleLPFilterStereo(onePoleFilter_t *f, const double *in, double *out){ // left channel f->tmpL = (f->a1 * in[0]) + (f->a2 * f->tmpL); out[0] = f->tmpL; // right channel f->tmpR = (f->a1 * in[1]) + (f->a2 * f->tmpR); out[1] = f->tmpR;} void onePoleHPFilter(onePoleFilter_t *f, const double in, double *out){ f->tmpL = (f->a1 * in) + (f->a2 * f->tmpL); *out = in - f->tmpL;} void onePoleHPFilterStereo(onePoleFilter_t *f, const double *in, double *out){ // left channel f->tmpL = (f->a1 * in[0]) + (f->a2 * f->tmpL); out[0] = in[0] - f->tmpL; // right channel f->tmpR = (f->a1 * in[1]) + (f->a2 * f->tmpR); out[1] = in[1] - f->tmpR;} /* 2-pole RC low-pass filter with Q factor, based on:** https://www.musicdsp.org/en/latest/Filters/38-lp-and-hp-filter.html*/ void setupTwoPoleFilter(double audioRate, double cutOff, double qFactor, twoPoleFilter_t *f){ if (cutOff >= audioRate/2.0) cutOff = (audioRate/2.0) - SMALL_NUMBER; const double a = 1.0 / pt2_tan((PT2_PI * cutOff) / audioRate); const double b = 1.0 / qFactor; f->a1 = 1.0 / (1.0 + b * a + a * a); f->a2 = 2.0 * f->a1; f->b1 = 2.0 * (1.0 - a*a) * f->a1; f->b2 = (1.0 - b * a + a * a) * f->a1;} void clearTwoPoleFilterState(twoPoleFilter_t *f){ f->tmpL[0] = f->tmpL[1] = f->tmpL[2] = f->tmpL[3] = 0.0; f->tmpR[0] = f->tmpR[1] = f->tmpR[2] = f->tmpR[3] = 0.0;} void twoPoleLPFilter(twoPoleFilter_t *f, const double in, double *out){ const double LOut = (f->a1 * in) + (f->a2 * f->tmpL[0]) + (f->a1 * f->tmpL[1]) - (f->b1 * f->tmpL[2]) - (f->b2 * f->tmpL[3]); // shift states f->tmpL[1] = f->tmpL[0]; f->tmpL[0] = in; f->tmpL[3] = f->tmpL[2]; f->tmpL[2] = LOut; // set output *out = LOut;} void twoPoleLPFilterStereo(twoPoleFilter_t *f, const double *in, double *out){ const double LOut = (f->a1 * in[0]) + (f->a2 * f->tmpL[0]) + (f->a1 * f->tmpL[1]) - (f->b1 * f->tmpL[2]) - (f->b2 * f->tmpL[3]); const double ROut = (f->a1 * in[1]) + (f->a2 * f->tmpR[0]) + (f->a1 * f->tmpR[1]) - (f->b1 * f->tmpR[2]) - (f->b2 * f->tmpR[3]); // shift states f->tmpL[1] = f->tmpL[0]; f->tmpL[0] = in[0]; f->tmpL[3] = f->tmpL[2]; f->tmpL[2] = LOut; f->tmpR[1] = f->tmpR[0]; f->tmpR[0] = in[1]; f->tmpR[3] = f->tmpR[2]; f->tmpR[2] = ROut; // set output out[0] = LOut; out[1] = ROut;}
#include "pt2_math.h"
#include "pt2_rcfilters.h"
#define SMALL_NUMBER (1E-4)
/* 1-pole RC low-pass/high-pass filter, based on:
** https://www.musicdsp.org/en/latest/Filters/116-one-pole-lp-and-hp.html
*/
void setupOnePoleFilter(double audioRate, double cutOff, onePoleFilter_t *f)
{
if (cutOff >= audioRate/2.0)
cutOff = (audioRate/2.0) - SMALL_NUMBER;
const double a = 2.0 - pt2_cos((PT2_TWO_PI * cutOff) / audioRate);
const double b = a - pt2_sqrt((a * a) - 1.0);
f->a1 = 1.0 - b;
f->a2 = b;
}
void clearOnePoleFilterState(onePoleFilter_t *f)
{
f->tmpL = f->tmpR = 0.0;
}
void onePoleLPFilter(onePoleFilter_t *f, const double in, double *out)
{
f->tmpL = (f->a1 * in) + (f->a2 * f->tmpL);
*out = f->tmpL;
}
void onePoleLPFilterStereo(onePoleFilter_t *f, const double *in, double *out)
{
// left channel
f->tmpL = (f->a1 * in[0]) + (f->a2 * f->tmpL);
out[0] = f->tmpL;
// right channel
f->tmpR = (f->a1 * in[1]) + (f->a2 * f->tmpR);
out[1] = f->tmpR;
}
void onePoleHPFilter(onePoleFilter_t *f, const double in, double *out)
{
f->tmpL = (f->a1 * in) + (f->a2 * f->tmpL);
*out = in - f->tmpL;
}
void onePoleHPFilterStereo(onePoleFilter_t *f, const double *in, double *out)
{
// left channel
f->tmpL = (f->a1 * in[0]) + (f->a2 * f->tmpL);
out[0] = in[0] - f->tmpL;
// right channel
f->tmpR = (f->a1 * in[1]) + (f->a2 * f->tmpR);
out[1] = in[1] - f->tmpR;
}
/* 2-pole RC low-pass filter with Q factor, based on:
** https://www.musicdsp.org/en/latest/Filters/38-lp-and-hp-filter.html
*/
void setupTwoPoleFilter(double audioRate, double cutOff, double qFactor, twoPoleFilter_t *f)
{
if (cutOff >= audioRate/2.0)
cutOff = (audioRate/2.0) - SMALL_NUMBER;
const double a = 1.0 / pt2_tan((PT2_PI * cutOff) / audioRate);
const double b = 1.0 / qFactor;
f->a1 = 1.0 / (1.0 + b * a + a * a);
f->a2 = 2.0 * f->a1;
f->b1 = 2.0 * (1.0 - a*a) * f->a1;
f->b2 = (1.0 - b * a + a * a) * f->a1;
}
void clearTwoPoleFilterState(twoPoleFilter_t *f)
{
f->tmpL[0] = f->tmpL[1] = f->tmpL[2] = f->tmpL[3] = 0.0;
f->tmpR[0] = f->tmpR[1] = f->tmpR[2] = f->tmpR[3] = 0.0;
}
void twoPoleLPFilter(twoPoleFilter_t *f, const double in, double *out)
{
const double LOut = (f->a1 * in) + (f->a2 * f->tmpL[0]) + (f->a1 * f->tmpL[1]) - (f->b1 * f->tmpL[2]) - (f->b2 * f->tmpL[3]);
// shift states
f->tmpL[1] = f->tmpL[0];
f->tmpL[0] = in;
f->tmpL[3] = f->tmpL[2];
f->tmpL[2] = LOut;
// set output
*out = LOut;
}
void twoPoleLPFilterStereo(twoPoleFilter_t *f, const double *in, double *out)
{
const double LOut = (f->a1 * in[0]) + (f->a2 * f->tmpL[0]) + (f->a1 * f->tmpL[1]) - (f->b1 * f->tmpL[2]) - (f->b2 * f->tmpL[3]);
const double ROut = (f->a1 * in[1]) + (f->a2 * f->tmpR[0]) + (f->a1 * f->tmpR[1]) - (f->b1 * f->tmpR[2]) - (f->b2 * f->tmpR[3]);
// shift states
f->tmpL[1] = f->tmpL[0];
f->tmpL[0] = in[0];
f->tmpL[3] = f->tmpL[2];
f->tmpL[2] = LOut;
f->tmpR[1] = f->tmpR[0];
f->tmpR[0] = in[1];
f->tmpR[3] = f->tmpR[2];
f->tmpR[2] = ROut;
// set output
out[0] = LOut;
out[1] = ROut;
}