Hash :
cae9c0ad
Author :
Thomas de Grivel
Date :
2020-02-03T21:21:13
hipass Butterworth first order filter
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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.
*/
#include <math.h>
#include "rtbuf.h"
#include "rtbuf_signal.h"
int rtbuf_signal_hipass_start (s_rtbuf *rtb)
{
s_rtbuf_signal_hipass_data *data;
assert(rtb->proc->out_bytes == sizeof(*data));
data = (s_rtbuf_signal_hipass_data*) rtb->data;
data->x1 = 0;
data->y1 = 0;
return 0;
}
int rtbuf_signal_hipass (s_rtbuf *rtb)
{
s_rtbuf_signal_fun in;
s_rtbuf_signal_fun cutoff;
s_rtbuf_signal_hipass_data *data;
unsigned int i = 0;
double k = 2.0 * RTBUF_SIGNAL_SAMPLERATE;
rtbuf_signal_fun(rtb, RTBUF_SIGNAL_HIPASS_IN_SIGNAL, &in);
rtbuf_signal_fun(rtb, RTBUF_SIGNAL_HIPASS_IN_CUTOFF, &cutoff);
data = (s_rtbuf_signal_hipass_data*) rtb->data;
while (i < RTBUF_SIGNAL_SAMPLES) {
double x = in.sample_fun(in.signal, i);
double fc = cutoff.sample_fun(cutoff.signal, i);
double wc = 2.0 * M_PI * fc;
data->signal[i] = (k * (x - data->x1) + (k - wc) * data->y1) / (k + wc);
data->x1 = x;
data->y1 = data->signal[i];
i++;
}
return 0;
}