FFT-based spectrum display from audio input

sketch_fft4.pde

// scrolling spectral display ala SpectrumLab
import processing.sound.*;

FFT fft; 
AudioIn in;
final int bands = 512;
float[] spectrum = new float[bands];
int leftEdge = 70 ;
int sampleRate = 44100 ;

HighPass highPass;

void setup() {
  colorMode( HSB, 100, 100, 100 ) ;
  size(1024, 600);
  background(0, 0, 0);
  
  // show available sound devices
  Sound.list() ;

  // Create an Input stream which is routed into the Amplitude analyzer
  fft = new FFT(this, bands);

  //highPass = new HighPass(this);

  // https://processing.github.io/processing-sound/processing/sound/Sound.html
  // https://processing.github.io/processing-sound/processing/sound/AudioDevice.html
  
  // get the audio input on Powerbook
  Sound s = new Sound(this);

  // Sabrent usb dongle
  s.inputDevice(3);
  
  // see if we can set the samplerate here
  s.sampleRate( sampleRate ) ;
  in = new AudioIn(this, 0);

  // start the Audio Input
  in.start();
  in.amp(1.0) ;

  //highPass.freq(1000);
  //highPass.process(in);

  // patch the AudioIn
  fft.input(in);
  
  //fft.analyze(spectrum);
}      

void draw() { 
  //background(0, 0, 0);

  // The result of the FFT is normalized
 fft.analyze(spectrum);

  // add to the display window
  renderSpectrum( ) ;
  
  // scroll window of previous spectra right (off screen)
  scrollRight( ) ;
  
  // (re)draw scale
  drawScale( 512, 100 ) ;
  
} // end draw
/*
void scrollRight( )
{
  loadPixels();
  for (int r = 0; r < height; r++)
  {
    arrayCopy(pixels, (width * r), pixels, width * r + 1, width - 1);
  }
  updatePixels();
}
*/

void scrollRight( )
{

  loadPixels();
  for (int r = 0; r < height; r++)
  {
    int start = ( width * r ) + leftEdge ;
    int dest = ( width * r )  + 1 + leftEdge ;
    //println ( start + "," + dest ) ;
    arrayCopy(pixels, start, pixels, dest, width - leftEdge - 1);
  }
  updatePixels();
}

void drawScale( int bins, int step )
{
  stroke( 57, 100, 100 ) ;
  for( int i = step ; i < bins ; i+= step )
  {
    float freq = (i * sampleRate) / bins / 2;
    freq = round( freq ) ;
    String yLabel = str( int( freq )) ;
    text( yLabel, 5, height - i );
  }
}

void renderSpectrum( ) {
  
  // Now loop through the bins, rendering
  //for ( int y = 0; y < spectrum.length / 2; y ++ ) {
    for ( int y = 0; y < bands ; y ++ ) {
    float binValue = spectrum[y] * 10000000 ;
    //println( binValue ) ;
    float hue = map( binValue, 0, 300,0, 100 ) ;
    stroke( hue, 100, binValue ) ;
    point( leftEdge, height - y ) ;
  } // end loop on bins
} // end render method