forked from PaulStoffregen/Audio
/
filter_biquad.h
156 lines (149 loc) · 6.26 KB
/
filter_biquad.h
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/* Audio Library for Teensy 3.X
* Copyright (c) 2014, Paul Stoffregen, paul@pjrc.com
*
* Development of this audio library was funded by PJRC.COM, LLC by sales of
* Teensy and Audio Adaptor boards. Please support PJRC's efforts to develop
* open source software by purchasing Teensy or other PJRC products.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice, development funding notice, and this permission
* notice shall be included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#ifndef filter_biquad_h_
#define filter_biquad_h_
#include "Arduino.h"
#include "AudioStream.h"
class AudioFilterBiquad : public AudioStream
{
public:
AudioFilterBiquad(void) : AudioStream(1, inputQueueArray) {
// by default, the filter will not pass anything
for (int i=0; i<32; i++) definition[i] = 0;
}
virtual void update(void);
// Set the biquad coefficients directly
void setCoefficients(uint32_t stage, const int *coefficients);
void setCoefficients(uint32_t stage, const double *coefficients) {
int coef[5];
coef[0] = coefficients[0] * 1073741824.0;
coef[1] = coefficients[1] * 1073741824.0;
coef[2] = coefficients[2] * 1073741824.0;
coef[3] = coefficients[3] * 1073741824.0;
coef[4] = coefficients[4] * 1073741824.0;
setCoefficients(stage, coef);
}
// Compute common filter functions
// http://www.musicdsp.org/files/Audio-EQ-Cookbook.txt
void setLowpass(uint32_t stage, float frequency, float q = 0.7071) {
int coef[5];
double w0 = frequency * (2 * 3.141592654 / AUDIO_SAMPLE_RATE_EXACT);
double sinW0 = sin(w0);
double alpha = sinW0 / ((double)q * 2.0);
double cosW0 = cos(w0);
double scale = 1073741824.0 / (1.0 + alpha);
/* b0 */ coef[0] = ((1.0 - cosW0) / 2.0) * scale;
/* b1 */ coef[1] = (1.0 - cosW0) * scale;
/* b2 */ coef[2] = coef[0];
/* a1 */ coef[3] = (-2.0 * cosW0) * scale;
/* a2 */ coef[4] = (1.0 - alpha) * scale;
setCoefficients(stage, coef);
}
void setHighpass(uint32_t stage, float frequency, float q = 0.7071) {
int coef[5];
double w0 = frequency * (2 * 3.141592654 / AUDIO_SAMPLE_RATE_EXACT);
double sinW0 = sin(w0);
double alpha = sinW0 / ((double)q * 2.0);
double cosW0 = cos(w0);
double scale = 1073741824.0 / (1.0 + alpha);
/* b0 */ coef[0] = ((1.0 + cosW0) / 2.0) * scale;
/* b1 */ coef[1] = -(1.0 + cosW0) * scale;
/* b2 */ coef[2] = coef[0];
/* a1 */ coef[3] = (-2.0 * cosW0) * scale;
/* a2 */ coef[4] = (1.0 - alpha) * scale;
setCoefficients(stage, coef);
}
void setBandpass(uint32_t stage, float frequency, float q = 1.0) {
int coef[5];
double w0 = frequency * (2 * 3.141592654 / AUDIO_SAMPLE_RATE_EXACT);
double sinW0 = sin(w0);
double alpha = sinW0 / ((double)q * 2.0);
double cosW0 = cos(w0);
double scale = 1073741824.0 / (1.0 + alpha);
/* b0 */ coef[0] = alpha * scale;
/* b1 */ coef[1] = 0;
/* b2 */ coef[2] = (-alpha) * scale;
/* a1 */ coef[3] = (-2.0 * cosW0) * scale;
/* a2 */ coef[4] = (1.0 - alpha) * scale;
setCoefficients(stage, coef);
}
void setNotch(uint32_t stage, float frequency, float q = 1.0) {
int coef[5];
double w0 = frequency * (2 * 3.141592654 / AUDIO_SAMPLE_RATE_EXACT);
double sinW0 = sin(w0);
double alpha = sinW0 / ((double)q * 2.0);
double cosW0 = cos(w0);
double scale = 1073741824.0 / (1.0 + alpha);
/* b0 */ coef[0] = scale;
/* b1 */ coef[1] = (-2.0 * cosW0) * scale;
/* b2 */ coef[2] = coef[0];
/* a1 */ coef[3] = (-2.0 * cosW0) * scale;
/* a2 */ coef[4] = (1.0 - alpha) * scale;
setCoefficients(stage, coef);
}
void setLowShelf(uint32_t stage, float frequency, float gain, float slope = 1.0f) {
int coef[5];
double a = pow(10.0, gain/40.0);
double w0 = frequency * (2 * 3.141592654 / AUDIO_SAMPLE_RATE_EXACT);
double sinW0 = sin(w0);
//double alpha = (sinW0 * sqrt((a+1/a)*(1/slope-1)+2) ) / 2.0;
double cosW0 = cos(w0);
//generate three helper-values (intermediate results):
double sinsq = sinW0 * sqrt( (pow(a,2.0)+1.0)*(1.0/slope-1.0)+2.0*a );
double aMinus = (a-1.0)*cosW0;
double aPlus = (a+1.0)*cosW0;
double scale = 1073741824.0 / ( (a+1.0) + aMinus + sinsq);
/* b0 */ coef[0] = a * ( (a+1.0) - aMinus + sinsq ) * scale;
/* b1 */ coef[1] = 2.0*a * ( (a-1.0) - aPlus ) * scale;
/* b2 */ coef[2] = a * ( (a+1.0) - aMinus - sinsq ) * scale;
/* a1 */ coef[3] = -2.0* ( (a-1.0) + aPlus ) * scale;
/* a2 */ coef[4] = ( (a+1.0) + aMinus - sinsq ) * scale;
setCoefficients(stage, coef);
}
void setHighShelf(uint32_t stage, float frequency, float gain, float slope = 1.0f) {
int coef[5];
double a = pow(10.0, gain/40.0);
double w0 = frequency * (2 * 3.141592654 / AUDIO_SAMPLE_RATE_EXACT);
double sinW0 = sin(w0);
//double alpha = (sinW0 * sqrt((a+1/a)*(1/slope-1)+2) ) / 2.0;
double cosW0 = cos(w0);
//generate three helper-values (intermediate results):
double sinsq = sinW0 * sqrt( (pow(a,2.0)+1.0)*(1.0/slope-1.0)+2.0*a );
double aMinus = (a-1.0)*cosW0;
double aPlus = (a+1.0)*cosW0;
double scale = 1073741824.0 / ( (a+1.0) - aMinus + sinsq);
/* b0 */ coef[0] = a * ( (a+1.0) + aMinus + sinsq ) * scale;
/* b1 */ coef[1] = -2.0*a * ( (a-1.0) + aPlus ) * scale;
/* b2 */ coef[2] = a * ( (a+1.0) + aMinus - sinsq ) * scale;
/* a1 */ coef[3] = 2.0* ( (a-1.0) - aPlus ) * scale;
/* a2 */ coef[4] = ( (a+1.0) - aMinus - sinsq ) * scale;
setCoefficients(stage, coef);
}
private:
int32_t definition[32]; // up to 4 cascaded biquads
audio_block_t *inputQueueArray[1];
};
#endif