index.js

/**
 * A whistle detector based on the research paper  --
 * "Human Whistle Detection and Frequency Estimation" by M. Nilsson and others.
 *
 * @author	   Shubham Jain (hi@shubhamjain.co)
 * @license    MIT License
 */

var SMQT = require('./lib/smqt'),
	  FFT = require('./lib/fft'),
	  dspFilter = require('./lib/dspFilter'),
	  jensenDiff = require('./lib/jensenDiff'),
	  raf = require('raf');


var defaultConfig = {
	sampleRate : 44100,  // Audio Input sample rate
	maxLevel : 8,        // Maximum level of SMQT
	freqBinCount: 512,   // Size of FFT

	jDiffThreshold : 0.45,   // Jensen Difference Threshold
	whistleBlockThreshold : 25, // Ratio of bandpass and bandstop blocks for 500-5000Hz

	sampleThreshold : 10 // Threshold for postive samples / 50 samples
};


module.exports = function whistlerr(whistleCallback, config) {

	// config argument is optional. set it to an empty object if not present
	if (typeof config === 'undefined' || config === null) {
  	config = {};
	}

	// fill in all omitted config parameters with default values
	config = Object.assign({}, defaultConfig, config)

	var audioContext

	// getUserMedia is prefixed a little differently in various browsers. handle these
	function getUserMedia(dictionary, callback, error)
	{
	  try {
	    navigator.getUserMedia = 
	    navigator.getUserMedia ||
	    navigator.webkitGetUserMedia ||
	    navigator.mozGetUserMedia;
	    navigator.getUserMedia(dictionary, callback, error);
	  } catch (e) {
	    alert('getUserMedia threw exception :' + e);
	  }
	}

	function gotStream(stream)
	{
		// Create an AudioNode from the stream.
		var mediaStreamSource = audioContext.createMediaStreamSource(stream);
		// Connect it to the destination.
		config.analyser = audioContext.createAnalyser();
		config.analyser.fftSize = config.freqBinCount;

		mediaStreamSource.connect( config.analyser );
		whistleFinder();
	}

	var timeBuf = new Uint8Array( config.freqBinCount ); //time domain data

	var totalSamples = 0, positiveSamples = 0,
		normData, fft, pbp,
		pbs, maxpbp, sumAmplitudes,
		minpbp, ratio, jDiff, i;

	if (!config.analyser) {
		audioContext = new AudioContext();
		getUserMedia({ audio: true, video: false }, gotStream, function(){
			alert('There was an error accessing audio input. Please check.');
		});
	} else {
		whistleFinder();
	}

	function whistleFinder() {
		config.analyser.getByteTimeDomainData(timeBuf);

		SMQT.init(timeBuf, config.maxLevel).calculate();

		// FFT calculation of nomralized data
		fft = new FFT(config.freqBinCount, config.sampleRate);

		fft.forward(SMQT.normalize());

		pbp = dspFilter.bandpass( fft.spectrum, {
			sampleRate : config.sampleRate,
			fLower : 500,
			fUpper : 5000
		});

		pbs = dspFilter.bandstop( fft.spectrum, {
			sampleRate : config.sampleRate,
			fLower : 500,
			fUpper : 5000
		});

		// Calculating mean(pbs) max(pbp)
		maxpbp = 0; sumAmplitudes = 0; minpbp = 100;

		for(i = 0; i < config.freqBinCount / 2; i++) {

			// Since it's a TypedArray, we can't use _Math._ operations
			if( pbp[i] > maxpbp)
				maxpbp = pbp[i];

			if( pbp[i] < minpbp)
				minpbp = pbp[i];

			sumAmplitudes += Math.abs(pbs[i]);
		}

		meanpbs = sumAmplitudes / (i - 1);

		// Forming data for Jensen Difference
		sumAmplitudes = 0;
		for( i = 0; i < config.freqBinCount / 2; i++) {
			pbp[i] = (pbp[i] - minpbp) + 2 / config.freqBinCount;
			sumAmplitudes += pbp[i];
		}

		for( i = 0; i < config.freqBinCount / 2; i++)
			pbp[i] /= sumAmplitudes;

		ratio = maxpbp / (meanpbs + 1);
		jDiff = jensenDiff(pbp, config.freqBinCount);

		if( ratio > config.whistleBlockThreshold && jDiff > config.jDiffThreshold) {
		 	positiveSamples++;

		 	if( positiveSamples > config.sampleThreshold ) {
				whistleCallback({
					ratio: ratio,
					jDiff: jDiff
				});
		 	}
		}

		if ( totalSamples === 50 ) {
			totalSamples = 0;
			positiveSamples = 0;
		} else {
			totalSamples += 1;
		}

		raf(whistleFinder); // cross platform requestAnimationFrame
	}
};