Tone.js/Tone/effect/AutoWah.js

define(["Tone/core/Tone", "Tone/component/Follower", "Tone/signal/ScaleExp", 
"Tone/effect/Effect", "Tone/component/Filter"], 
function(Tone){

	"use strict";

	/**
	 *  @class  AutoWah connects an envelope follower to a bandpass filter.
	 *          Some inspiration from Tuna.js https://github.com/Dinahmoe/tuna
	 *
	 *  @constructor
	 *  @extends {Tone.Effect}
	 *  @param {number} [baseFrequency=100] the frequency the filter is set 
	 *                                       to at the low point of the wah
	 *  @param {number} [octaves=5] the number of octaves above the baseFrequency
	 *                               the filter will sweep to when fully open
	 *  @param {number} [sensitivity=0] the decibel threshold sensitivity for 
	 *                                   the incoming signal. Normal range of -40 to 0. 
	 *  @example
	 *  var autoWah = new Tone.AutoWah(100, 6, -20);
	 */
	Tone.AutoWah = function(){

		var options = this.optionsObject(arguments, ["baseFrequency", "octaves", "sensitivity"], Tone.AutoWah.defaults);
		Tone.Effect.call(this, options);

		/**
		 *  the envelope follower
		 *  @type {Tone.Follower}
		 *  @private
		 */
		this.follower = new Tone.Follower(options.follower);

		/**
		 *  scales the follower value to the frequency domain
		 *  @type {Tone}
		 *  @private
		 */
		this._sweepRange = new Tone.ScaleExp(0, 1, 0.5);

		/**
		 *  @type {number}
		 *  @private
		 */
		this._baseFrequency = options.baseFrequency;

		/**
		 *  @type {number}
		 *  @private
		 */
		this._octaves = options.octaves;

		/**
		 *  the input gain to adjust the sensitivity
		 *  @type {GainNode}
		 *  @private
		 */
		this._inputBoost = this.context.createGain();

		/**
		 *  @type {BiquadFilterNode}
		 *  @private
		 */
		this._bandpass = new Tone.Filter({
			"rolloff" : -48,
			"frequency" : 0,
			"Q" : options.Q,
		});
	
		/**
		 *  @type {Tone.Filter}
		 *  @private
		 */
		this._peaking = new Tone.Filter(0, "peaking");
		this._peaking.gain.value = options.gain;

		/**
		 * the gain of the filter.
		 * @type {Tone.Signal}
		 */
		this.gain = this._peaking.gain;

		/**
		 * The quality of the filter.
		 * @type {Tone.Signal}
		 */
		this.Q = this._bandpass.Q;

		//the control signal path
		this.effectSend.chain(this._inputBoost, this.follower, this._sweepRange);
		this._sweepRange.connect(this._bandpass.frequency);
		this._sweepRange.connect(this._peaking.frequency);
		//the filtered path
		this.effectSend.chain(this._bandpass, this._peaking, this.effectReturn);
		//set the initial value
		this._setSweepRange();
		this.sensitivity = options.sensitivity;

		this._readOnly(["gain", "Q"]);
	};

	Tone.extend(Tone.AutoWah, Tone.Effect);

	/**
	 *  @static
	 *  @type {Object}
	 */
	Tone.AutoWah.defaults = {
		"baseFrequency" : 100,
		"octaves" : 6,
		"sensitivity" : 0,
		"Q" : 2,
		"gain" : 2,
		"follower" : {
			"attack" : 0.3,
			"release" : 0.5
		}
	};

	/**
	 * The number of octaves that the filter will sweep.
	 * @memberOf Tone.AutoWah#
	 * @type {number}
	 * @name octaves
	 */
	Object.defineProperty(Tone.AutoWah.prototype, "octaves", {
		get : function(){
			return this._octaves;
		}, 
		set : function(octaves){
			this._octaves = octaves;
			this._setSweepRange();
		}
	});

	/**
	 * The base frequency from which the sweep will start from.
	 * @memberOf Tone.AutoWah#
	 * @type {Tone.Frequency}
	 * @name baseFrequency
	 */
	Object.defineProperty(Tone.AutoWah.prototype, "baseFrequency", {
		get : function(){
			return this._baseFrequency;
		}, 
		set : function(baseFreq){
			this._baseFrequency = baseFreq;
			this._setSweepRange();
		}
	});

	/**
	 * The sensitivity to control how responsive to the input signal the filter is. 
	 * in Decibels. 
	 * @memberOf Tone.AutoWah#
	 * @type {number}
	 * @name sensitivity
	 */
	Object.defineProperty(Tone.AutoWah.prototype, "sensitivity", {
		get : function(){
			return this.gainToDb(1 / this._inputBoost.gain.value);
		}, 
		set : function(sensitivy){
			this._inputBoost.gain.value = 1 / this.dbToGain(sensitivy);
		}
	});

	/**
	 *  sets the sweep range of the scaler
	 *  @private
	 */
	Tone.AutoWah.prototype._setSweepRange = function(){
		this._sweepRange.min = this._baseFrequency;
		this._sweepRange.max = Math.min(this._baseFrequency * Math.pow(2, this._octaves), this.context.sampleRate / 2);
	};

	/**
	 *  clean up
	 *  @returns {Tone.AutoWah} `this`
	 */
	Tone.AutoWah.prototype.dispose = function(){
		Tone.Effect.prototype.dispose.call(this);
		this.follower.dispose();
		this.follower = null;
		this._sweepRange.dispose();
		this._sweepRange = null;
		this._bandpass.dispose();
		this._bandpass = null;
		this._peaking.dispose();
		this._peaking = null;
		this._inputBoost.disconnect();
		this._inputBoost = null;
		this._writable(["gain", "Q"]);
		this.gain = null;
		this.Q = null;
		return this;
	};

	return Tone.AutoWah;
});