rtbuf/rtbuf/rtbuf_signal_lowpass3.c

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• Hash : 79f93abe
  Author : Thomas de Grivel
  Date : 2020-02-08T15:47:03
  

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• rtbuf_signal_lowpass3.c

• /*
   * Copyright 2020 Thomas de Grivel <thoxdg@gmail.com> +33614550127
   * Copyright 2020 Judy Najnudel
   *
   * 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_lowpass3_start (s_rtbuf *rtb)
  {
    s_rtbuf_signal_lowpass3_data *data;
    assert(rtb->proc->out_bytes == sizeof(*data));
    data = (s_rtbuf_signal_lowpass3_data*) rtb->data;
    data->x1 = 0.0;
    data->x2 = 0.0;
    data->x3 = 0.0;
    data->y1 = 0.0;
    data->y2 = 0.0;
    data->y3 = 0.0;
    return 0;
  }
  
  int rtbuf_signal_lowpass3 (s_rtbuf *rtb)
  {
    s_rtbuf_signal_fun in;
    s_rtbuf_signal_fun cutoff;
    s_rtbuf_signal_lowpass3_data *data;
    unsigned int i = 0;
    const double fs = RTBUF_SIGNAL_SAMPLERATE;
    const double fs2 = fs * fs;
    const double fs3 = fs2 * fs;
    const double _8fs3 = 8.0 * fs3;
    rtbuf_signal_fun(rtb, RTBUF_SIGNAL_LOWPASS_IN_SIGNAL, &in);
    rtbuf_signal_fun(rtb, RTBUF_SIGNAL_LOWPASS_IN_CUTOFF, &cutoff);
    data = (s_rtbuf_signal_lowpass3_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 wc = 2.0 * M_PI * fc;
      const double wc2 = wc * wc;
      const double wc3 = wc2 * wc;
      const double _4fs2wc = 4.0 * fs2 * wc;
      const double _8fs2wc = 2.0 * _4fs2wc;
      const double _4fswc2 = 4.0 * fs * wc2;
      const double _3wc3 = 3.0 * wc3;
      const double a = wc3 + _4fswc2 + _8fs2wc + _8fs3;
      const double b = _8fs2wc + 24.0 * fs3 - (_3wc3 + _4fswc2);
      const double c = _4fswc2 + _8fs2wc - (24.0 * fs3 + _3wc3);
      const double d = _8fs3 + _4fswc2 - (wc3 + _8fs2wc);
      data->signal[i] = (wc3 * (x
                                + 3.0 * (data->x1 +
                                         data->x2)
                                + data->x3)
                         + b * data->y1
                         + c * data->y2
                         + d * data->y3) / a;
      data->x3 = data->x2;
      data->x2 = data->x1;
      data->x1 = x;
      data->y3 = data->y2;
      data->y2 = data->y1;
      data->y1 = data->signal[i];
      i++;
    }
    return 0;
  }
  

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