Beat Detection and Spectrum Viz

// beat detection code courtesy of https://discourse.processing.org/u/atagger/summary

// https://discourse.processing.org/t/beat-detection-algorithm-help-feedback/31588

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let sound;

let beatDetect;

let spectrumBg;

let spectrumX = 0;

​

function preload() {

  //put your sound file here

  sound = loadSound("https://www.paulwheeler.us/files/Dubstep%203.mp3");

}

​

function setup() {

  createCanvas(windowWidth, windowHeight);

  spectrumBg = createGraphics(width, height);

  spectrumBg.background(0);

  spectrumBg.noStroke();

  frameRate(60);

  beatDetect = new BeatDetect();

  sound.loop();

}

​

​

function draw() {

  background(0);

​

  let beat = beatDetect.detectBeat();

  if (spectrumX > 0) {

    image(spectrumBg, width - spectrumX, 0, spectrumX, height, 0, 0, spectrumX, height);

  }

  image(spectrumBg, 0, 0, width - spectrumX, height, spectrumX, 0, width - spectrumX, height);

  if (beat) {

    fill(255, 0, 0);

    //console.log(size);

    ellipse(width / 2, height / 2, 300 + beatDetect.size, 300 + beatDetect.size);

  }

}

​

//BeatDetect constructor

function BeatDetect() {

  //http://archive.gamedev.net/archive/reference/programming/features/beatdetection/

  //algorithm #2 - Frequency selected sound energy

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  let sampleBuffer = []; //sample history buffer

  let bandsAverage = []; //array of averages of the bands

  let energyBuffer = []; //array of current sound energy

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  let fourier = new p5.FFT();

  this.size = 0;

​

  this.detectBeat = function() {

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    //analyze fourier

    let spectrum = fourier.analyze();

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    let count = 0; //reset count every frame

    let isBeat = false; //reset isBeat every frame

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    let bandsEnergy = []; //start a new array each frame, so we don't pass in an array reference :)

    let bands_temp = []; //temp array to split the frequency bands

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    let h = height / spectrum.length;

    for (let i = 0; i < spectrum.length; i++) {

      spectrumBg.fill(spectrum[i]);

      spectrumBg.rect(spectrumX, map(i, 0, spectrum.length, 0, height), 1, Math.max(1, h));

​

      energyBuffer[i] = spectrum[i] * spectrum[i]; //calculate energy

      bands_temp.push(energyBuffer[i]); // temp array to split into grouped bands

​

      //collect 32 samples (one band of 1024 i.e. 1024/32 = 32 bands)

      if (bands_temp.length == 32) {

​

        let sum = 0; // init the sum to zero

        for (let j = 0; j < bands_temp.length; j++) {

          sum += bands_temp[j]; // get the sum of the band's samples

          bandsEnergy[count] = sum; // get average energy of band's grouping

        }

​

        bands_temp = []; //clear temp bands_sum array for next set of 32 samples;

        count++; //increment count index, reset this every frame;

      }

    }

    spectrumX = (spectrumX + 1) % width;

​

    sampleBuffer.push(bandsEnergy);

​

    //add +1 since we remove a value each frame

    if (sampleBuffer.length == 30 + (1)) {

      for (let j = 0; j < bandsEnergy.length; j++) {

​

        let bandSum = 0; //reset bandSum when we get to a new band

​

        //loop through all arrays in the history buffer

        for (let k = 0; k < sampleBuffer.length; k++) {

          bandSum += sampleBuffer[k][j]; // get the sum for each freq. band in the buffer

        }

        //calc avg from sum in each band of the buffer

        bandsAverage[j] = bandSum / sampleBuffer.length;

      }

​

      //remove the oldest sample from the array

      sampleBuffer.splice(0, 1);

    }

​

    for (let k = 0; k < sampleBuffer.length; k++) {

      let c = 1.095; //increase to lower sensitivity

​

      if (bandsEnergy[k] > bandsAverage[k] * c) {

        isBeat = true;

        this.size = (bandsEnergy[k]) * 0.0001;

        //this.size=300;

        return isBeat;

      }

    }

​

    //console.log(bandsEnergy.length);

    //console.log(sampleBuffer.length);

​

    //console.log( bandsAverage[14] + "bandAverage");

    //console.log( bandsEnergy[14] +  "bandEnergy");

  } // end DETECT

} // end CONSTRUCTOR