Today I was working with analysis. This patch doesn’t have a lot of good looks but I have implemented a zero crossing rate function, an rms function for time domain analysis, spectral centroid, spectral rolloff, and spectral compactness. I coded up a spectral flatness measure but I keep getting zero as the output. I haven’t done thorough debugging job because I was trying to make sure I have something done for today!
I started out hoping that I could implement both the spectral features and time domain features as an AudioListener object but the FFT object doesn’t work that way. So, I made a method that is called every draw loop. This isn’t the nicest solution but it works. I am dreaming up a link between jAudio and MINIM. If I’m not careful I might be putting another thing on my plate :)
Today’s patch is really just an extension of MINIM’s spectral display patch but an overlay of the feature extraction output. My hope is to eventually do a MINIM version of sndpeek. Maybe tomorrow there will be text and waterfall plots... maybe.
import ddf.minim.analysis.*;
import ddf.minim.*;
Minim minim;
AudioPlayer jingle;
FFT fft;
DrawTime dt;
int w;
float[] myspectrum;
void setup()
{
size(512, 200, P3D);
minim = new Minim(this);
jingle = minim.loadFile("jingle.mp3", 2048);
jingle.loop();
fft = new FFT(jingle.bufferSize(), jingle.sampleRate());
// calculate averages based on a miminum octave width of 22 Hz
// split each octave into three bands
fft.logAverages(22, 3);
dt = new DrawTime();
jingle.addListener(dt);
myspectrum = new float[ jingle.bufferSize() ];
rectMode(CORNERS);
}
void draw()
{
background(0);
fill(255);
stroke(0);
fft.forward(jingle.mix);
// avgWidth() returns the number of frequency bands each average represents
// we'll use it as the width of our rectangles
w = int(width/fft.avgSize());
for(int i = 0; i < fft.avgSize(); i++)
{
rect(i*w, height, i*w + w, height - fft.getAvg(i)*5);
}
for(int i= 0; i < jingle.bufferSize(); i++)
myspectrum[i] = fft.getBand(i);
dt.draw();
drawSpectral(myspectrum);
}
void keyPressed(){
if (key == ' ')
saveFrame();
}
void stop()
{
jingle.close();
minim.stop();
super.stop();
}void drawSpectral(float[] spec)
{
//==============================
// SPECTRAL CENTROID
//==============================
float m1 = 0;
float m0 = 0;
for (int i = 0; i < spec.length; i++){
m1 += i * spec[i];
m0 += spec[i];
}
float centroid = 0.5;
if (m0 != 0.0)
{
centroid = (m1 / m0) / (float) spec.length ;
}
pushStyle();
stroke(90,255,90);
strokeWeight(3);
line(centroid * width, 0 , centroid * width, height);
popStyle();
//==============================
// SPECTRAL ROLLOFF
//==============================
float perc = 0.8;
float[] sumWindow = new float [ spec.length ];
float total = 0;
float sum = 0;
float specRolloff = 0;
boolean specdone = false;
for( int i = 0; i< spec.length; i++)
{
sum += spec[i];
sumWindow[i] = sum;
}
total = sumWindow[spec.length-1];
for ( int i = spec.length-1; i > 1 ; i--){
if (sumWindow[i] < 0.8 * total)
{
specRolloff = (float) i;
specdone = true;
break;
}
}
if ( !specdone )
specRolloff = float(spec.length - 1);
specRolloff /= spec.length;
pushStyle();
stroke(89, 169, 210);
line( specRolloff * width, 0, specRolloff * width, height);
popStyle();
//==============================
// SPECTRAL COMPATCTNESS
// code snippet from jAUDIO
//==============================
float[] mag_spec = new float[ spec.length ];
for (int i = 0; i < spec.length; i++)
{
mag_spec[i] = abs( spec[i] );
}
double compactness = 0.0;
for (int i = 1; i < mag_spec.length - 1; i++) {
if ((mag_spec[i - 1] > 0.0) && (mag_spec[i] > 0.0) && (mag_spec[i + 1] > 0.0))
{
compactness += Math .abs(
20.0 * Math.log(mag_spec[i])
- 20.0 * (Math.log(mag_spec[i - 1])
+ Math.log(mag_spec[i])
+ Math .log(mag_spec[i + 1]))
/ 3.0);
}
}
pushStyle();
stroke(12,48, 96);
// seems to evaluate between 2k and 9k so divide by 10000 as hack to normalize
line ( (float)compactness / 10000 * width, 0, (float)compactness / 10000 * width , height);
popStyle();
//==============================
// SPECTRAL FLATNESS
// DOESN'T WORK -- geometric mean always evaluates to zero :(
//==============================
float flatness = 0;
double geometricMean = spec[0];
float arithmeticMean = sum;
for ( int i = 1; i < spec.length; i++)
{
geometricMean *= (double) spec[i];
if (spec[i] == 0.0)
{
println("WARNING: ZERO DETECTED " +frameCount);
}
}
geometricMean = Math.pow(geometricMean , (1.0f / spec.length) );
arithmeticMean /= spec.length;
flatness = (float)geometricMean / arithmeticMean ;
println(flatness);
}class DrawTime implements AudioListener
{
private float[] left;
private float[] right;
synchronized void samples(float[] samp)
{
left = samp;
}
synchronized void samples(float[] sampL, float[] sampR)
{
left = sampL;
right = sampR;
}
synchronized void draw()
{
if (left != null && left.length > 0)
{
//RMS
float rms = 0.0;
for (int i = 0; i < left.length; i++)
rms += (left[i] * left[i] );
if (rms!= 0.0)
{
rms /= left.length;
rms = sqrt(rms);
}
pushStyle();
noFill();
stroke (255, 90,90);
line(0, height - rms*height, width, height - rms*height);
popStyle();
// ZERO-CROSSING RATE (normalized)
// detected / buffsize
float zcr = 0;
for (int i = 0; i < left.length - 1; i++)
{
if (left[i] > 0.0 && left[i + 1] < 0.0)
zcr++;
else if (left[i] < 0.0 && left[i + 1] > 0.0)
zcr++;
else if (left[i] == 0.0 && left[i + 1] != 0.0)
zcr++;
}
zcr = zcr / (float) left.length;
pushStyle();
noFill();
stroke (90, 90,255);
line(0, height - zcr*height, width, height - zcr*height);
popStyle();
}
}
}
