Tone.js/Tone/effect/PitchShift.js

define(["Tone/core/Tone", "Tone/component/LFO", "Tone/component/CrossFade", "Tone/signal/Signal", "Tone/effect/Effect"], 
	function (Tone) {

	/**
	 *  @class Tone.PitchShift does near-realtime pitch shifting to the incoming signal. 
	 *         The effect is achieved by speeding up or slowing down the delayTime
	 *         of a DelayNode using a sawtooth wave. 
	 *         Algorithm found in [this pdf](http://dsp-book.narod.ru/soundproc.pdf).
	 *         Additional reference by [Miller Pucket](http://msp.ucsd.edu/techniques/v0.11/book-html/node115.html).
	 *         
	 *  @extends {Tone.Effect}
	 *  @param {Interval=} pitch The interval to transpose the incoming signal by. 
	 */
	Tone.PitchShift = function(){

		Tone.Effect.call(this);
		var options = this.optionsObject(arguments, ["pitch"], Tone.PitchShift.defaults);

		/**
		 *  The pitch signal
		 *  @type  {Tone.Signal}
		 *  @private
		 */
		this._frequency = new Tone.Signal(0);

		/**
		 *  Uses two DelayNodes to cover up the jump in
		 *  the sawtooth wave. 
		 *  @type  {DelayNode}
		 *  @private
		 */
		this._delayA = this.context.createDelay(1);

		/**
		 *  The first LFO.
		 *  @type  {Tone.LFO}
		 *  @private
		 */
		this._lfoA = new Tone.LFO({
			"min" : 0,
			"max" : 0.1,
			"type" : "sawtooth"
		}).connect(this._delayA.delayTime);


		/**
		 *  The second DelayNode
		 *  @type  {DelayNode}
		 *  @private
		 */
		this._delayB = this.context.createDelay(1);

		/**
		 *  The first LFO.
		 *  @type  {Tone.LFO}
		 *  @private
		 */
		this._lfoB = new Tone.LFO({
			"min" : 0,
			"max" : 0.1,
			"type" : "sawtooth",
			"phase" : 180
		}).connect(this._delayB.delayTime);

		/**
		 *  Crossfade quickly between the two delay lines
		 *  to cover up the jump in the sawtooth wave
		 *  @type  {Tone.CrossFade}
		 *  @private
		 */
		this._crossFade = new Tone.CrossFade().connect(this.effectReturn);

		/**
		 *  LFO which alternates between the two
		 *  delay lines to cover up the disparity in the
		 *  sawtooth wave. 
		 *  @type  {Tone.LFO}
		 */
		this._crossFadeLFO = new Tone.LFO({
			"min" : 0,
			"max" : 1,
			"type" : "triangle",
			"phase" : 90
		}).connect(this._crossFade.fade);

		/**
		 *  Hold the current pitch
		 *  @type {Number}
		 *  @private
		 */
		this._pitch = options.pitch;

		/**
		 *  Hold the current windowSize
		 *  @type {Number}
		 *  @private
		 */
		this._windowSize = options.windowSize;

		//connect the two delay lines up
		this._delayA.connect(this._crossFade.a);
		this._delayB.connect(this._crossFade.b);
		//connect the frequency
		this._frequency.fan(this._lfoA.frequency, this._lfoB.frequency, this._crossFadeLFO.frequency);
		//route the input
		this.effectSend.fan(this._delayA, this._delayB);
		//start the LFOs at the same time
		var now = this.now();
		this._lfoA.start(now);
		this._lfoB.start(now);
		this._crossFadeLFO.start(now);
		//set the initial value
		this.windowSize = this._windowSize;
	};

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

	/**
	 *  default values
	 *  @static
	 *  @type {Object}
	 *  @const
	 */
	Tone.PitchShift.defaults = {
		"pitch" : 0,
		"windowSize" : 0.1
	};

	/**
	 * Repitch the incoming signal by some interval (measured
	 * in semi-tones). 
	 * @memberOf Tone.PitchShift#
	 * @type {Interval}
	 * @name pitch
	 * @example
	 * pitchShift.pitch = -12; //down one octave
	 * pitchShift.pitch = 7; //up a fifth
	 */
	Object.defineProperty(Tone.PitchShift.prototype, "pitch", {
		get : function(){
			return this._pitch;
		},
		set : function(interval){
			this._pitch = interval;
			var factor = 0;
			if (interval < 0){
				this._lfoA.min = 0;
				this._lfoA.max = this._windowSize;
				this._lfoB.min = 0;
				this._lfoB.max = this._windowSize;
				factor = this.intervalToFrequencyRatio(interval - 1) + 1;
			} else {
				this._lfoA.min = this._windowSize;
				this._lfoA.max = 0;
				this._lfoB.min = this._windowSize;
				this._lfoB.max = 0;
				factor = this.intervalToFrequencyRatio(interval) - 1;
			}
			this._frequency.value = factor * (1.2 / this._windowSize);
		}
	});

	/**
	 * The window size corresponds roughly to the sample length in a looping sampler. 
	 * Smaller values are desirable for a less noticeable delay time of the pitch shifted
	 * signal, but larger values will result in smoother pitch shifting for larger intervals. 
	 * A nominal range of 0.03 to 0.1 is recommended. 
	 * @memberOf Tone.PitchShift#
	 * @type {Time}
	 * @name windowSize
	 * @example
	 * pitchShift.windowSize = 0.1;
	 */
	Object.defineProperty(Tone.PitchShift.prototype, "windowSize", {
		get : function(){
			return this._windowSize;
		},
		set : function(size){
			this._windowSize = this.toSeconds(size);
			this.pitch = this._pitch;
		}
	});

	/**
	 *  Clean up.
	 *  @return  {Tone.PitchShift}  this
	 */
	Tone.PitchShift.prototype.dispose = function(){
		Tone.Effect.prototype.dispose.call(this);
		this._frequency.dispose();
		this._frequency = null;
		this._delayA.disconnect();
		this._delayA = null;
		this._delayB.disconnect();
		this._delayB = null;
		this._lfoA.dispose();
		this._lfoA = null;
		this._lfoB.dispose();
		this._lfoB = null;
		this._crossFade.dispose();
		this._crossFade = null;
		this._crossFadeLFO.dispose();
		this._crossFadeLFO = null;
		return this;
	};

	return Tone.PitchShift;
});