Day 26

I guess I am at it again. Today I was playing around with an idea for making a spectral centroid visual. I was thinking about FFT displays and I thought that having bars rise and fall isn’t all that visually stimulating, though it is accurate for display. So, what I did was map spectral centroid to the location of a directional light in OPENGL and had it point to a line of boxes whose size modulates with the amplitude of the incoming signal. I also reversed the amplitude mapping so that loud sounds create small boxes. It makes for some nice motion.

I also spent some time looking through the Processing.org bug list in reference to some glitchyness in OPENGL as implemented in Processing. There are varying reports about how to smooth out anti-aliasing and threading issues. It seems the best thing to do is to try out all solutions and see which one works for that particular patch. Although the simplest thing to do to avoid the anti-aliasing problem is to only draw vertical or horizontal lines, but who wants to do that?

import javax.media.opengl.*;
import processing.opengl.*;
import ddf.minim.*;
import ddf.minim.analysis.*;

Minim minim;
AudioInput in;
FFT fft;

float r;
float zr;

float lastlevel;
float[]  myspectrum;
float[] features;

void setup()
{
  size(720, 480, OPENGL);

  //http://code.google.com/p/processing/issues/detail?id=217&q=opengl&colspec=Stars%20ID%20Type%20Status%20Priority%20Owner%20Summary
  //http://code.google.com/p/processing/issues/detail?id=53&q=opengl&colspec=Stars%20ID%20Type%20Status%20Priority%20Owner%20Summary
  //noSmooth();
  hint( DISABLE_OPENGL_2X_SMOOTH );
  hint( ENABLE_OPENGL_4X_SMOOTH );
  //smooth();
  
  minim = new Minim(this);
  in = minim.getLineIn(Minim.STEREO, 512);
  
  fft = new FFT(in.bufferSize(), in.sampleRate());
  myspectrum = new float[ in.bufferSize() ];

  fill(200, 40);
  stroke(30,40);
}

void draw()
{
  background(30);
  lights();

  fft.forward(in.mix);
  for(int i= 0; i < fft.specSize(); i++)
    myspectrum[i] = fft.getBand(i);
  
  //==============================
  // SPECTRAL CENTROID
  //==============================
  float m1 = 0;
  float m0 = 0;

  for (int i = 0; i < myspectrum.length; i++){
    m1 += i * myspectrum[i];
    m0 += myspectrum[i]; 
  }

  float centroid = 0.5;
  if (m0 != 0.0)
  {
    centroid = (m1 / m0) / (float) myspectrum.length ;  
  }
  //==============================
  
  float level = in.mix.level();
  // lowpass filter to smooth out motion
  level += lastlevel;
  level *= 0.5;

  translate( width/2 , height/2 );
  rotateX ( zr++ / 50 );

  // set range of centroid to -1 -> 1
  directionalLight( 200,100,230, centroid * 2 -1 ,0,-1 );
  
  float spacing = (float)width / fft.specSize() ;
  float boxsize = 10;
  for ( int i = 0 ; i < fft.specSize() ; i++ )
  { 
    pushMatrix();
    translate( (i * spacing) - (width/2) + boxsize - 10 ,0,0);
    box(boxsize - 10*log(level) - 30);
    popMatrix();
  }
  
  lastlevel = level;
}

void stop()
{
  in.close();
  minim.stop();
  super.stop();
}

void mouseClicked()
{
   saveFrame(); 
}

View this code on GitHub