purezen 0.0.2

Runtime for the Pure Data (Pd) audio programming language, implemented as an extensible audio library allowing full control over signal processing, message passing, and graph manipulation. Pure Data is a graph-based programming language environment creating interactive music and multimedia works.
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/*
 *  Copyright 2009,2010,2011,2012 Reality Jockey, Ltd.
 *                 info@rjdj.me
 *                 http://rjdj.me/
 *
 *  This file is part of ZenGarden.
 *
 *  ZenGarden is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU Lesser General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  ZenGarden is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU Lesser General Public License for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public License
 *  along with ZenGarden.  If not, see <http://www.gnu.org/licenses/>.
 *
 */

#include "DspBandpassFilter.h"
#include "PdGraph.h"

message::Object *DspBandpassFilter::new_object(pd::Message *init_message, PdGraph *graph) {
  return new DspBandpassFilter(init_message, graph);
}

DspBandpassFilter::DspBandpassFilter(pd::Message *init_message, PdGraph *graph) : DspFilter(3, graph) {
  fc = init_message->is_float(0) ? init_message->get_float(0) : graph->get_sample_rate()/2.0f;
  q = init_message->is_float(1) ? init_message->get_float(1) : 1.0f;
  calcFiltCoeff(fc, q);
}

DspBandpassFilter::~DspBandpassFilter() {
  // nothing to do
}

// http://www.musicdsp.org/files/Audio-EQ-Cookbook.txt
void DspBandpassFilter::calcFiltCoeff(float fc, float q) {
  if (fc > 0.5f * graph->get_sample_rate()) fc = 0.5f * graph->get_sample_rate();
  else if (fc < 0.0f) fc = 0.0f;
  if (q < 0.0f) q = 0.0f;

  float wc = 2.0f*M_PI*fc/graph->get_sample_rate();
  float alpha = sinf(wc)/(2.0f*q);

  b[0] = alpha/(1.0f+alpha);
  b[1] = 0.0f;
  b[2] = -alpha/(1.0f+alpha);
  b[3] = -2.0f*cosf(wc)/(1.0f+alpha);
  b[4] = (1.0f-alpha)/(1.0f+alpha);
}

void DspBandpassFilter::process_message(int inlet_index, pd::Message *message) {
  switch (inlet_index) {
    case 0: {
      if (message->is_symbol_str(0, "clear")) {
        x1 = x2 = dspBufferAtOutlet[0][0] = dspBufferAtOutlet[0][1] = 0.0f;
      }
      break;
    }
    case 1: {
      if (message->is_float(0)) calcFiltCoeff(message->get_float(0), q);
      break;
    }
    case 2: {
      if (message->is_float(0)) calcFiltCoeff(fc, message->get_float(0));
      break;
    }
    default: break;
  }
}