Tone.js/Tone/source/Noise.js

import Tone from "../core/Tone";
import "../source/Source";
import "../core/Buffer";
import "../source/BufferSource";

/**
 *  @class  Tone.Noise is a noise generator. It uses looped noise buffers to save on performance.
 *          Tone.Noise supports the noise types: "pink", "white", and "brown". Read more about
 *          colors of noise on [Wikipedia](https://en.wikipedia.org/wiki/Colors_of_noise).
 *
 *  @constructor
 *  @extends {Tone.Source}
 *  @param {string} type the noise type (white|pink|brown)
 *  @example
 * //initialize the noise and start
 * var noise = new Tone.Noise("pink").start();
 *
 * //make an autofilter to shape the noise
 * var autoFilter = new Tone.AutoFilter({
 * 	"frequency" : "8m",
 * 	"min" : 800,
 * 	"max" : 15000
 * }).connect(Tone.Master);
 *
 * //connect the noise
 * noise.connect(autoFilter);
 * //start the autofilter LFO
 * autoFilter.start()
 */
Tone.Noise = function(){

	var options = Tone.defaults(arguments, ["type"], Tone.Noise);
	Tone.Source.call(this, options);

	/**
	 *  @private
	 *  @type {AudioBufferSourceNode}
	 */
	this._source = null;

	/**
	 *  the buffer
	 *  @private
	 *  @type {AudioBuffer}
	 */
	this._type = options.type;

	/**
	 *  The playback rate of the noise. Affects
	 *  the "frequency" of the noise.
	 *  @type {Positive}
	 *  @signal
	 */
	this._playbackRate = options.playbackRate;
};

Tone.extend(Tone.Noise, Tone.Source);

/**
 *  the default parameters
 *
 *  @static
 *  @const
 *  @type {Object}
 */
Tone.Noise.defaults = {
	"type" : "white",
	"playbackRate" : 1
};

/**
 * The type of the noise. Can be "white", "brown", or "pink".
 * @memberOf Tone.Noise#
 * @type {string}
 * @name type
 * @example
 * noise.type = "white";
 */
Object.defineProperty(Tone.Noise.prototype, "type", {
	get : function(){
		return this._type;
	},
	set : function(type){
		if (this._type !== type){
			if (type in _noiseBuffers){
				this._type = type;
				//if it's playing, stop and restart it
				if (this.state === Tone.State.Started){
					var now = this.now();
					this._stop(now);
					this._start(now);
				}
			} else {
				throw new TypeError("Tone.Noise: invalid type: "+type);
			}
		}
	}
});

/**
 *  The playback rate of the noise. Affects
 *  the "frequency" of the noise.
 *  @type {Positive}
 *  @signal
 */
Object.defineProperty(Tone.Noise.prototype, "playbackRate", {
	get : function(){
		return this._playbackRate;
	},
	set : function(rate){
		this._playbackRate = rate;
		if (this._source){
			this._source.playbackRate.value = rate;
		}
	}
});

/**
 *  internal start method
 *
 *  @param {Time} time
 *  @private
 */
Tone.Noise.prototype._start = function(time){
	var buffer = _noiseBuffers[this._type];
	this._source = new Tone.BufferSource(buffer).connect(this.output);
	this._source.loop = true;
	this._source.playbackRate.value = this._playbackRate;
	this._source.start(this.toSeconds(time), Math.random() * (buffer.duration - 0.001));
};

/**
 *  internal stop method
 *
 *  @param {Time} time
 *  @private
 */
Tone.Noise.prototype._stop = function(time){
	if (this._source){
		this._source.stop(this.toSeconds(time));
		this._source = null;
	}
};

/**
 * Restarts the noise.
 * @param  {Time} time When to restart the noise.
 * @return {Tone.Noise}      this
 */
Tone.Noise.prototype.restart = function(time){
	//TODO could be optimized by cancelling the buffer source 'stop'
	//stop and restart
	this._stop(time);
	this._start(time);
	return this;
};

/**
 *  Clean up.
 *  @returns {Tone.Noise} this
 */
Tone.Noise.prototype.dispose = function(){
	Tone.Source.prototype.dispose.call(this);
	if (this._source !== null){
		this._source.disconnect();
		this._source = null;
	}
	this._buffer = null;
	return this;
};

///////////////////////////////////////////////////////////////////////////
// THE BUFFERS
///////////////////////////////////////////////////////////////////////////

//Noise buffer stats
var bufferLength = 44100 * 5;
var channels = 2;

/**
 *	The noise arrays. Generated on initialization.
 *  borrowed heavily from https://github.com/zacharydenton/noise.js
 *  (c) 2013 Zach Denton (MIT)
 *  @static
 *  @private
 *  @type {Array}
 */
var _noiseBuffers = {};
var _noiseCache = {};

Object.defineProperty(_noiseBuffers, "pink", {
	get : function(){
		if (!_noiseCache.pink){
			var buffer = [];
			for (var channelNum = 0; channelNum < channels; channelNum++){
				var channel = new Float32Array(bufferLength);
				buffer[channelNum] = channel;
				var b0, b1, b2, b3, b4, b5, b6;
				b0 = b1 = b2 = b3 = b4 = b5 = b6 = 0.0;
				for (var i = 0; i < bufferLength; i++){
					var white = Math.random() * 2 - 1;
					b0 = 0.99886 * b0 + white * 0.0555179;
					b1 = 0.99332 * b1 + white * 0.0750759;
					b2 = 0.96900 * b2 + white * 0.1538520;
					b3 = 0.86650 * b3 + white * 0.3104856;
					b4 = 0.55000 * b4 + white * 0.5329522;
					b5 = -0.7616 * b5 - white * 0.0168980;
					channel[i] = b0 + b1 + b2 + b3 + b4 + b5 + b6 + white * 0.5362;
					channel[i] *= 0.11; // (roughly) compensate for gain
					b6 = white * 0.115926;
				}
			}
			_noiseCache.pink = new Tone.Buffer().fromArray(buffer);
		}
		return _noiseCache.pink;
	}
});

Object.defineProperty(_noiseBuffers, "brown", {
	get : function(){
		if (!_noiseCache.brown){
			var buffer = [];
			for (var channelNum = 0; channelNum < channels; channelNum++){
				var channel = new Float32Array(bufferLength);
				buffer[channelNum] = channel;
				var lastOut = 0.0;
				for (var i = 0; i < bufferLength; i++){
					var white = Math.random() * 2 - 1;
					channel[i] = (lastOut + (0.02 * white)) / 1.02;
					lastOut = channel[i];
					channel[i] *= 3.5; // (roughly) compensate for gain
				}
			}
			_noiseCache.brown = new Tone.Buffer().fromArray(buffer);
		}
		return _noiseCache.brown;
	}
});

Object.defineProperty(_noiseBuffers, "white", {
	get : function(){
		if (!_noiseCache.white){
			var buffer = [];
			for (var channelNum = 0; channelNum < channels; channelNum++){
				var channel = new Float32Array(bufferLength);
				buffer[channelNum] = channel;
				for (var i = 0; i < bufferLength; i++){
					channel[i] = Math.random() * 2 - 1;
				}
			}
			_noiseCache.white = new Tone.Buffer().fromArray(buffer);
		}
		return _noiseCache.white;
	}
});

export default Tone.Noise;