Realtime FFT from the microphone with the minim processing library

minim_microphone_fft.pde

import ddf.minim.analysis.*;
import ddf.minim.*;

Minim minim;
AudioSource in;
FFT fft;

void setup() {
  size(512, 200);
  
  //handle audio input
  minim = new Minim(this);
  in = minim.getLineIn();
  fft = new FFT( in.bufferSize(), in.sampleRate() );
}

void draw() {
  background(0);
  stroke(255);
  
  // perform a forward FFT on the samples in jingle's mix buffer,
  // which contains the mix of both the left and right channels of the file
  fft.forward( in.mix );
  
  for(int i = 0; i < fft.specSize(); i++) {
    // draw the line for frequency band i, scaling it up a bit so we can see it
    line( i, height, i, height - fft.getBand(i)*8 );
  }
}