Hash :
1a898ff0
Author :
Thomas de Grivel
Date :
2020-02-11T15:30:47
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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 lowpass fifth order filter
a: (sqrt(5)-1)/2 $
b: (sqrt(5)+1)/2 $
s: 2*F*(1-z)/(1+z) $
B5:(s/w+1)*((s/w)^2+a*(s/w)+1)*((s/w)^2+b*s/w+1) $
H: 1/B5 $
ratsimp(H);
5 5 5 4 5 3 5 2 5 5
(w z + 5 w z + 10 w z + 10 w z + 5 w z + w )
5 4 2 3
/((w + ((- 2 sqrt(5)) - 2) F w + (4 sqrt(5) + 12) F w
3 2 4 5 5
+ ((- 8 sqrt(5)) - 24) F w + (16 sqrt(5) + 16) F w - 32 F ) z
5 4 2 3
+ (5 w + ((- 6 sqrt(5)) - 6) F w + (4 sqrt(5) + 12) F w
3 2 4 5 4
+ (8 sqrt(5) + 24) F w + ((- 48 sqrt(5)) - 48) F w + 160 F ) z
5 4 2 3
+ (10 w + ((- 4 sqrt(5)) - 4) F w + ((- 8 sqrt(5)) - 24) F w
3 2 4 5 3
+ (16 sqrt(5) + 48) F w + (32 sqrt(5) + 32) F w - 320 F ) z
5 4 2 3
+ (10 w + (4 sqrt(5) + 4) F w + ((- 8 sqrt(5)) - 24) F w
3 2 4 5 2
+ ((- 16 sqrt(5)) - 48) F w + (32 sqrt(5) + 32) F w + 320 F ) z
5 4 2 3
+ (5 w + (6 sqrt(5) + 6) F w + (4 sqrt(5) + 12) F w
3 2 4 5
+ ((- 8 sqrt(5)) - 24) F w + ((- 48 sqrt(5)) - 48) F w - 160 F ) z
5 4 2 3
+ w + (2 sqrt(5) + 2) F w + (4 sqrt(5) + 12) F w
3 2 4 5
+ (8 sqrt(5) + 24) F w + (16 sqrt(5) + 16) F w + 32 F )
a: w5 + (r5 + 1)( 2)(f w4 + 8 f4 w) + (4 r5 + 12) (f2 w3 + 2 f3 w2) + 32 f5; z
b: 5 w5 + (r5 + 1)( 6)(f w4 - 8 f4 w) + (4 r5 + 12) (f2 w3 - 2 f3 w2) - 160 f5; z1
c: 10 w5 + (r5 + 1)( 4)(f w4 + 8 f4 w) + (4 r5 + 12)(-2)(f2 w3 + 2 f3 w2) + 320 f5; z2
d: 10 w5 + (r5 + 1)(-4)(f w4 - 8 f4 w) + (4 r5 + 12)(-2)(f2 w3 - 2 f3 w2) - 320 f5; z3
e: 5 w5 + (r5 + 1)(-6)(f w4 + 8 f4 w) + (4 r5 + 12) (f2 w3 + 2 f3 w2) + 160 f5; z4
f: w5 + (r5 + 1)(-2)(f w4 - 8 f4 w) + (4 r5 + 12) (f2 w3 - 2 f3 w2) - 32 f5; z5
*/
#include <math.h>
#include "rtbuf.h"
#include "rtbuf_signal.h"
int rtbuf_signal_lowpass5_start (s_rtbuf *rtb)
{
s_rtbuf_signal_lowpass5_data *data;
assert(rtb->proc->out_bytes == sizeof(*data));
data = (s_rtbuf_signal_lowpass5_data*) rtb->data;
data->x1 = 0.0;
data->x2 = 0.0;
data->x3 = 0.0;
data->x4 = 0.0;
data->x5 = 0.0;
data->y1 = 0.0;
data->y2 = 0.0;
data->y3 = 0.0;
data->y4 = 0.0;
data->y5 = 0.0;
return 0;
}
int rtbuf_signal_lowpass5 (s_rtbuf *rtb)
{
s_rtbuf_signal_fun in;
s_rtbuf_signal_fun cutoff;
s_rtbuf_signal_lowpass5_data *data;
unsigned int i = 0;
const double r5_1 = sqrt(5.0) + 1.0;
const double _4r5_12 = 4.0 * sqrt(5.0) + 12.0;
const double f = RTBUF_SIGNAL_SAMPLERATE;
const double f2 = f * f;
const double f3 = f2 * f;
const double f4 = f2 * f2;
const double f5 = f2 * f3;
const double _32f5 = 32.0 * f5;
const double _160f5 = 160.0 * f5;
const double _320f5 = 320.0 * f5;
rtbuf_signal_fun(rtb, RTBUF_SIGNAL_LOWPASS_IN_SIGNAL, &in);
rtbuf_signal_fun(rtb, RTBUF_SIGNAL_LOWPASS_IN_CUTOFF, &cutoff);
data = (s_rtbuf_signal_lowpass5_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 w = 2.0 * M_PI * fc;
const double _8f4w = 8.0 * f4 * w;
const double w2 = w * w;
const double _2f3w2 = 2.0 * f3 * w2;
const double w3 = w2 * w;
const double f2w3 = f2 * w3;
const double f2w3p2f3w2 = f2w3 + _2f3w2;
const double f2w3m2f3w2 = f2w3 - _2f3w2;
const double w4 = w2 * w2;
const double fw4 = f * w4;
const double fw4p8f4w = (fw4 + _8f4w);
const double fw4m8f4w = (fw4 - _8f4w);
const double w5 = w2 * w3;
const double _5w5 = 5.0 * w5;
const double _10w5 = 10.0 * w5;
const double a = w5 + r5_1 * 2.0 * fw4p8f4w + _4r5_12 * f2w3p2f3w2 + _32f5;
const double b = _5w5 + r5_1 * 6.0 * fw4m8f4w + _4r5_12 * f2w3m2f3w2 - _160f5;
const double c = _10w5 + r5_1 * 4.0 * fw4p8f4w + _4r5_12 * -2.0 * f2w3p2f3w2 + _320f5;
const double d = _10w5 + r5_1 * -4.0 * fw4m8f4w + _4r5_12 * -2.0 * f2w3m2f3w2 - _320f5;
const double e = _5w5 + r5_1 * -6.0 * fw4p8f4w + _4r5_12 * f2w3p2f3w2 + _160f5;
const double f = w5 + r5_1 * -2.0 * fw4m8f4w + _4r5_12 * f2w3m2f3w2 - _32f5;
data->signal[i] = (w5 * (x
+ 5.0 * (data->x1
+ data->x4)
+ 10.0 * (data->x2
+ data->x3)
+ data->x5)
- (b * data->y1
+ c * data->y2
+ d * data->y3
+ e * data->y4
+ f * data->y5)) / a;
data->x5 = data->x4;
data->x4 = data->x3;
data->x3 = data->x2;
data->x2 = data->x1;
data->x1 = x;
data->y5 = data->y4;
data->y4 = data->y3;
data->y3 = data->y2;
data->y2 = data->y1;
data->y1 = data->signal[i];
i++;
}
return 0;
}