Hash :
2aeac2a6
Author :
Thomas de Grivel
Date :
2020-02-20T09:46:11
wip Butterworth second order 10 band equalizer
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/*
* Copyright 2020 Thomas de Grivel <thoxdg@gmail.com> +33614550127
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
/* Butterworth bandpass second order filter
s: 2*f*(1-z)/(1+z) $
B2: (q*(s/w+w/s))^2+sqrt(2)*(q*(s/w+w/s))+1 $
H: 1/B2 $
ratsimp(H);
2 2 4 2 2 2 2 2
(%o25) (4 f w z - 8 f w z + 4 f w )
2 4 3/2 3 2 2 2 2 7/2 3 4 2 4
/((q w - 2 f q w + (8 f q + 4 f ) w - 2 f q w + 16 f q ) z
2 4 5/2 3 9/2 3 4 2 3
+ (4 q w - 2 f q w + 2 f q w - 64 f q ) z
2 4 2 2 2 2 4 2 2
+ (6 q w + ((- 16 f q ) - 8 f ) w + 96 f q ) z
2 4 5/2 3 9/2 3 4 2 2 4 3/2 3
+ (4 q w + 2 f q w - 2 f q w - 64 f q ) z + q w + 2 f q w
2 2 2 2 7/2 3 4 2
+ (8 f q + 4 f ) w + 2 f q w + 16 f q )
a: q2 w4 + sqrt(2)^3 f q w3 + (8 f2 q2 + 4 f2) w2 + sqrt(2)^7 f3 q w + 16 f4 q2;
b: 4 q2 w4 + sqrt(2)^5 f q w3 - sqrt(2)^9 f3 q w - 64 f4 q2;
c: 6 q2 w4 - 2 (8 f2 q2 + 4 f2) w2 + 96 f4 q2;
d: 4 q2 w4 - sqrt(2)^5 f q w3 + sqrt(2)^9 f3 q w - 64 f4 q2;
e: q2 w4 - sqrt(2)^3 f q w3 + (8 f2 q2 + 4 f2) w2 - sqrt(2)^7 f3 q w + 16 f4 q2;
-----------------------------------------------------------------------------------
a: q2 w4 + sqrt(2)^3 f q w3 + (2 q2 + 1) 4 f2 w2 + sqrt(2)^7 f3 q w + 16 f4 q2;
b: 4 q2 w4 + sqrt(2)^5 f q w3 - sqrt(2)^9 f3 q w - 64 f4 q2;
c: 6 q2 w4 - 2 (2 q2 + 1) 4 f2 w2 + 96 f4 q2;
d: 4 q2 w4 - sqrt(2)^5 f q w3 + sqrt(2)^9 f3 q w - 64 f4 q2;
e: q2 w4 - sqrt(2)^3 f q w3 + (2 q2 + 1) 4 f2 w2 - sqrt(2)^7 f3 q w + 16 f4 q2;
-----------------------------------------------------------------------------------
y: (4 f2 w2 (x4 - 2 x2 + x) - (b y1 + c y2 + d y3 + e y4)) / a;
*/
#include <math.h>
#include "rtbuf.h"
#include "rtbuf_signal.h"
int rtbuf_signal_bandpass2_start (s_rtbuf *rtb)
{
s_rtbuf_signal_bandpass2_data *data;
assert(rtb->proc->out_bytes == sizeof(*data));
data = (s_rtbuf_signal_bandpass2_data*) rtb->data;
data->x1 = 0.0;
data->x2 = 0.0;
data->x3 = 0.0;
data->x4 = 0.0;
data->y1 = 0.0;
data->y2 = 0.0;
data->y3 = 0.0;
data->y4 = 0.0;
return 0;
}
int rtbuf_signal_bandpass2 (s_rtbuf *rtb)
{
s_rtbuf_signal_fun in;
s_rtbuf_signal_fun cutoff;
s_rtbuf_signal_fun qfactor;
s_rtbuf_signal_bandpass2_data *data;
unsigned int i = 0;
const double sqrt2_3 = sqrt2_2 * M_SQRT2;
const double sqrt2_5 = sqrt2_3 * sqrt2_2;
const double sqrt2_7 = sqrt2_5 * sqrt2_2;
const double sqrt2_9 = sqrt2_7 * sqrt2_2;
const double f = RTBUF_SIGNAL_SAMPLERATE;
const double f2 = f * f;
const double f3 = f2 * f;
const double f4 = f2 * f2;
rtbuf_signal_fun(rtb, RTBUF_SIGNAL_BANDPASS_IN_SIGNAL, &in);
rtbuf_signal_fun(rtb, RTBUF_SIGNAL_BANDPASS_IN_CUTOFF, &cutoff);
rtbuf_signal_fun(rtb, RTBUF_SIGNAL_BANDPASS_IN_QFACTOR, &qfactor);
data = (s_rtbuf_signal_bandpass2_data*) rtb->data;
while (i < RTBUF_SIGNAL_SAMPLES) {
const double x = in.sample_fun(in.signal, i);
const double fc = cutoff.sample_fun(cutoff.signal, i);
const double q = qfactor.sample_fun(qfactor.signal, i);
const double q2 = q * q;
const double f4q2 = f4 * q2;
const double _16f4q2 = 16.0 * f4q2;
const double _64f4q2 = 64.0 * f4q2;
const double w = 2.0 * M_PI * fc;
const double f3qw = f3 * q * w;
const double sqrt2_7f3qw = sqrt2_7 * f3qw;
const double sqrt2_9f3qw = sqrt2_9 * f3qw;
const double w2 = w * w;
const double _4f2w2 = 4.0 * f2 * w2;
const double _2q2_1_4f2w2 = (2.0 * q2 + 1.0) * _4f2w2;
const double w3 = w2 * w;
const double fqw3 = f * q * w3;
const double sqrt2_3fqw3 = sqrt2_3 * fqw3;
const double sqrt2_5fqw3 = sqrt2_5 * fqw3;
const double w4 = w2 * w2;
const double q2w4 = q2 * w4;
const double _4q2w4 = 4.0 * q2w4;
const double a = q2w4 + sqrt2_3fqw3 + _2q2_1_4f2w2 + sqrt2_7f3qw + _16f4q2;
const double b = _4q2w4 + sqrt2_5fqw3 - sqrt2_9f3qw - _64f4q2;
const double c = 6.0 * q2w4 - 2.0 * _2q2_1_4f2w2 + 96.0 * f4q2;
const double d = _4q2w4 - sqrt2_5fqw3 + sqrt2_9f3qw - _64f4q2;
const double e = q2w4 - sqrt2_3fqw3 + _2q2_1_4f2w2 - sqrt2_7f3qw + _16f4q2;
data->signal[i] = (_4f2w2 * (x
- 2.0 * data->x2
+ data->x4)
- (b * data->y1
+ c * data->y2
+ d * data->y3
+ e * data->y4)) / a;
data->x4 = data->x3;
data->x3 = data->x2;
data->x2 = data->x1;
data->x1 = x;
data->y4 = data->y3;
data->y3 = data->y2;
data->y2 = data->y1;
data->y1 = data->signal[i];
i++;
}
return 0;
}