bandpassfilter.pde

This is processing for java examples.

/**
 * Band Pass Filter
 * by Damien Di Fede.
 *   
 * This sketch demonstrates how to use the BandPass effect.
 * Move the mouse left and right to change the frequency of the pass band.
 * Move the mouse up and down to change the band width of the pass band.
 */

import ddf.minim.*;
import ddf.minim.effects.*;

Minim minim;
AudioPlayer groove;
BandPass bpf;

void setup()
{
  size(512, 200, P2D);
  
  minim = new Minim(this);
  
  groove = minim.loadFile("groove.mp3");
  groove.loop();
  // make a band pass filter with a center frequency of 440 Hz and a bandwidth of 20 Hz
  // the third argument is the sample rate of the audio that will be filtered
  // it is required to correctly compute values used by the filter
  bpf = new BandPass(440, 20, groove.sampleRate());
  groove.addEffect(bpf);
}

void draw()
{
  background(0);
  stroke(255);
  // draw the waveforms
  // the values returned by left.get() and right.get() will be between -1 and 1,
  // so we need to scale them up to see the waveform
  for(int i = 0; i < groove.right.size()-1; i++)
  {
    float x1 = map(i, 0, groove.bufferSize(), 0, width);
    float x2 = map(i+1, 0, groove.bufferSize(), 0, width);
    line(x1, height/4 - groove.left.get(i)*50, x2, height/4 - groove.left.get(i+1)*50);
    line(x1, 3*height/4 - groove.right.get(i)*50, x2, 3*height/4 - groove.right.get(i+1)*50);
  }
  // draw a rectangle to represent the pass band
  noStroke();
  fill(255, 0, 0, 60);
  rect(mouseX - bpf.getBandWidth()/20, 0, bpf.getBandWidth()/10, height);
}

void mouseMoved()
{
  // map the mouse position to the range [100, 10000], an arbitrary range of passBand frequencies
  float passBand = map(mouseX, 0, width, 100, 2000);
  bpf.setFreq(passBand);
  float bandWidth = map(mouseY, 0, height, 50, 500);
  bpf.setBandWidth(bandWidth);
  // prints the new values of the coefficients in the console
  bpf.printCoeff();
}

void stop()
{
  // always close Minim audio classes when you finish with them
  groove.close();
  // always stop Minim before exiting
  minim.stop();
  
  super.stop();
}