tests rms of the incoming signal

test/helper/Meter.js

@@ -0,0 +1,55 @@
+define(["Tone/core/Tone"], function (Tone) {
+
+	//hold onto the current context
+	var onlineContext = Tone.context;
+
+	/**
+	 *  OFFLINE TESTING
+	 */
+	var Meter = function(duration){
+		duration = duration || 1;
+		var sampleRate = 44100;
+		//dummy functions
+		this._before = Tone.noOp;
+		this._after = Tone.noOp;
+		this._test = Tone.noOp;
+		var rmsFrame = 256;
+		//offline rendering context
+		this.context = new OfflineAudioContext(1, sampleRate * duration, sampleRate);
+		this.context.oncomplete = function(e){
+			var buffer = e.renderedBuffer.getChannelData(0);
+			for (var j = 0; j < buffer.length; j++){
+				var sum = 0;
+				if (j >= rmsFrame){
+					for (var k = j - rmsFrame; k < j; k++){
+						sum += buffer[k] * buffer[k];
+					}
+					this._test(Math.sqrt(sum / rmsFrame), j / sampleRate);
+				}
+			}
+			this._after();
+			//reset the old context
+			Tone.setContext(onlineContext);
+		}.bind(this);
+	};
+
+	Meter.prototype.run = function(){
+		Tone.setContext(this.context);
+		this._before(this.context.destination);
+		this.context.startRendering();
+	};
+
+	Meter.prototype.before = function(cb){
+		this._before = cb;
+	};
+
+	Meter.prototype.after = function(cb){
+		this._after = cb;
+	};
+
+	Meter.prototype.test = function(cb){
+		this._test = cb;
+	};
+
+	return Meter;
+});