Tone.js/Tone/effect/Freeverb.js

define(["Tone/core/Tone", "Tone/component/LowpassCombFilter", "Tone/effect/StereoEffect", 
	"Tone/signal/Signal", "Tone/component/Split", "Tone/component/Merge", "Tone/signal/ScaleExp"], 
function(Tone){

	"use strict";

	/**
	 *  an array of comb filter delay values from Freeverb implementation
	 *  @static
	 *  @private
	 *  @type {Array}
	 */
	var combFilterTunings = [1557 / 44100, 1617 / 44100, 1491 / 44100, 1422 / 44100, 1277 / 44100, 1356 / 44100, 1188 / 44100, 1116 / 44100];

	/**
	 *  an array of allpass filter frequency values from Freeverb implementation
	 *  @private
	 *  @static
	 *  @type {Array}
	 */
	var allpassFilterFrequencies = [225, 556, 441, 341];

	/**
	 *  @class Tone.Freeverb is a reverb based on [Freeverb](https://ccrma.stanford.edu/~jos/pasp/Freeverb.html).
	 *         Read more on reverb on [SoundOnSound](http://www.soundonsound.com/sos/may00/articles/reverb.htm).
	 *
	 *  @extends {Tone.Effect}
	 *  @constructor
	 *  @param {NormalRange|Object} [roomSize] Correlated to the decay time. 
	 *  @param {Frequency} [dampening] The cutoff frequency of a lowpass filter as part 
	 *                                 of the reverb. 
	 *  @example
	 * var freeverb = new Tone.Freeverb().toMaster();
	 * freeverb.dampening.value = 1000;
	 * //routing synth through the reverb
	 * var synth = new Tone.AMSynth().connect(freeverb);
	 */
	Tone.Freeverb = function(){

		var options = this.optionsObject(arguments, ["roomSize", "dampening"], Tone.Freeverb.defaults);
		Tone.StereoEffect.call(this, options);

		/**
		 *  The roomSize value between. A larger roomSize
		 *  will result in a longer decay. 
		 *  @type {NormalRange}
		 *  @signal
		 */
		this.roomSize = new Tone.Signal(options.roomSize, Tone.Type.NormalRange);

		/**
		 *  The amount of dampening of the reverberant signal. 
		 *  @type {Frequency}
		 *  @signal
		 */
		this.dampening = new Tone.Signal(options.dampening, Tone.Type.Frequency);

		/**
		 *  the comb filters
		 *  @type {Array}
		 *  @private
		 */
		this._combFilters = [];

		/**
		 *  the allpass filters on the left
		 *  @type {Array}
		 *  @private
		 */
		this._allpassFiltersL = [];

		/**
		 *  the allpass filters on the right
		 *  @type {Array}
		 *  @private
		 */
		this._allpassFiltersR = [];

		//make the allpass filters on teh right
		for (var l = 0; l < allpassFilterFrequencies.length; l++){
			var allpassL = this.context.createBiquadFilter();
			allpassL.type = "allpass";
			allpassL.frequency.value = allpassFilterFrequencies[l];
			this._allpassFiltersL.push(allpassL);
		}

		//make the allpass filters on the left
		for (var r = 0; r < allpassFilterFrequencies.length; r++){
			var allpassR = this.context.createBiquadFilter();
			allpassR.type = "allpass";
			allpassR.frequency.value = allpassFilterFrequencies[r];
			this._allpassFiltersR.push(allpassR);
		}

		//make the comb filters
		for (var c = 0; c < combFilterTunings.length; c++){
			var lfpf = new Tone.LowpassCombFilter(combFilterTunings[c]);
			if (c < combFilterTunings.length / 2){
				this.effectSendL.chain(lfpf, this._allpassFiltersL[0]);
			} else {
				this.effectSendR.chain(lfpf, this._allpassFiltersR[0]);
			}
			this.roomSize.connect(lfpf.resonance);
			this.dampening.connect(lfpf.dampening);
			this._combFilters.push(lfpf);
		}

		//chain the allpass filters togetehr
		this.connectSeries.apply(this, this._allpassFiltersL);
		this.connectSeries.apply(this, this._allpassFiltersR);
		this._allpassFiltersL[this._allpassFiltersL.length - 1].connect(this.effectReturnL);
		this._allpassFiltersR[this._allpassFiltersR.length - 1].connect(this.effectReturnR);
		this._readOnly(["roomSize", "dampening"]);
	};

	Tone.extend(Tone.Freeverb, Tone.StereoEffect);

	/**
	 *  @static
	 *  @type {Object}
	 */
	Tone.Freeverb.defaults = {
		"roomSize" : 0.7, 
		"dampening" : 3000
	};

	/**
	 *  Clean up. 
	 *  @returns {Tone.Freeverb} this
	 */
	Tone.Freeverb.prototype.dispose = function(){
		Tone.StereoEffect.prototype.dispose.call(this);
		for (var al = 0; al < this._allpassFiltersL.length; al++) {
			this._allpassFiltersL[al].disconnect();
			this._allpassFiltersL[al] = null;
		}
		this._allpassFiltersL = null;
		for (var ar = 0; ar < this._allpassFiltersR.length; ar++) {
			this._allpassFiltersR[ar].disconnect();
			this._allpassFiltersR[ar] = null;
		}
		this._allpassFiltersR = null;
		for (var cf = 0; cf < this._combFilters.length; cf++) {
			this._combFilters[cf].dispose();
			this._combFilters[cf] = null;
		}
		this._combFilters = null;
		this._writable(["roomSize", "dampening"]);
		this.roomSize.dispose();
		this.roomSize = null;
		this.dampening.dispose();
		this.dampening = null;
		return this;
	};

	return Tone.Freeverb;
});