quimbs

var findFundamentalFreq = function(buffer, sampleRate) {
	// We use Autocorrelation to find the fundamental frequency.
	
	// In order to correlate the signal with itself (hence the name of the algorithm), we will check two points 'k' frames away. 
	// The autocorrelation index will be the average of these products. At the same time, we normalize the values.
	// Source: http://www.phy.mty.edu/~suits/autocorrelation.html
	// Assuming the sample rate is 48000Hz, a 'k' equal to 1000 would correspond to a 48Hz signal (48000/1000 = 48), 
	// while a 'k' equal to 8 would correspond to a 6000Hz one, which is enough to cover most (if not all) 
	// the notes we have in the notes.json file.
	var n = 1024, bestR = 0, bestK = -1;

quimbs

var findCentsOffPitch = function(freq, refFreq) {
    // We need to find how far freq is from baseFreq in cents
    var log2 = 0.6931471805599453; // Math.log(2)
    var multiplicativeFactor = freq / refFreq;
    
    // We use Math.floor to get the integer part and ignore decimals
    var cents = Math.floor(1200 * (Math.log(multiplicativeFactor) / log2));
    return cents;
};

quimbs

// 'notes' is an array of objects like { note: 'A4', frequency: 440 }.
// See initialization in the source code of the demo
var findClosestNote = function(freq, notes) {
  // Use binary search to find the closest note
  var low = -1, high = notes.length;
  while (high - low > 1) {
      var pivot = Math.round((low + high) / 2);
      if (notes[pivot].frequency <= freq) {
          low = pivot;
      } else {

quimbs

var isGetUserMediaSupported = function(){
  navigator.getUserMedia = navigator.getUserMedia || navigator.webkitGetUserMedia || navigator.mozGetUserMedia;
  if((navigator.mediaDevices && navigator.mediaDevices.getUserMedia) || navigator.getUserMedia){
      return true;
  }
  
  return false;
};

if(isGetUserMediaSupported()){

quimbs

var analyserAudioNode, sourceAudioNode, micStream;
var streamReceived = function(stream) {
  micStream = stream;

  analyserAudioNode = audioContext.createAnalyser();
  analyserAudioNode.fftSize = 2048;

  sourceAudioNode = audioContext.createMediaStreamSource(micStream);
  sourceAudioNode.connect(analyserAudioNode);

quimbs

// micStream is the MediaStream object we get from the Media Stream API
var sourceAudioNode = audioContext.createMediaStreamSource(micStream);
sourceAudioNode.connect(analyserAudioNode); // See initialization in the AnalyserNode section of the demo.

quimbs

{
	"432": [
		{
			"note":"C0",
			"frequency":16.05
		},
		{
			"note":"C#0",
			"frequency":17.01
		},

quimbs

var isAudioContextSupported = function () {
    // This feature is still prefixed in Safari
    window.AudioContext = window.AudioContext || window.webkitAudioContext;
    if(window.AudioContext){
        return true;
    }
    else {
        return false;
    }
};