forked from PaulStoffregen/Audio
-
Notifications
You must be signed in to change notification settings - Fork 0
/
filter_biquad.h
156 lines (149 loc) · 6.3 KB
/
filter_biquad.h
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
/* 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 = 0.7071f) {
int coef[5];
double w0 = frequency * (2.0f * 3.141592654f / 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 * (2.0f * 3.141592654f / 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 * (2.0f * 3.141592654f / 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 * (2.0f * 3.141592654f / 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/40.0f);
double w0 = frequency * (2.0f * 3.141592654f / 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/(double)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/40.0f);
double w0 = frequency * (2.0f * 3.141592654f / 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/(double)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