Tone.js/Tone/component/Meter.js

///////////////////////////////////////////////////////////////////////////////
//
//  METER
//
//	get the rms of the input signal with some averaging
//
//	inspired by https://github.com/cwilso/volume-meter/blob/master/volume-meter.js
//	The MIT License (MIT) Copyright (c) 2014 Chris Wilson
///////////////////////////////////////////////////////////////////////////////

define(["Tone/core/Tone", "Tone/core/Master"], function(Tone){

	//@param {number=} channels
	Tone.Meter = function(channels){
		//extends Unit
		Tone.call(this);

		this.channels = this.defaultArg(channels, 1);
		this.volume = new Array(this.channels);
		this.values = new Array(this.channels);
		//zero out the volume array
		for (var i = 0; i < this.channels; i++){
			this.volume[i] = 0;
			this.values[i] = 0;
		}
		this.clipTime = 0;
		
		//components
		this.jsNode = this.context.createScriptProcessor(this.bufferSize, this.channels, this.channels);
		this.jsNode.onaudioprocess = this.onprocess.bind(this);

		//signal just passes
		this.input.connect(this.output);
		this.input.connect(this.jsNode);
		//so it doesn't get garbage collected
		this.jsNode.toMaster();
	};

	Tone.extend(Tone.Meter, Tone);


	//@param {number=} channel
	//@returns {number}
	Tone.Meter.prototype.getLevel = function(channel){
		channel = this.defaultArg(channel, 0);
		var vol = this.volume[channel];
		if (vol < 0.00001){
			return 0;
		} else {
			return vol;
		}
	};

	//@param {number=} channel
	//@returns {number}
	Tone.Meter.prototype.getValue = function(channel){
		channel = this.defaultArg(channel, 0);
		return this.values[channel];
	};

	//@param {number=} channel
	//@returns {number} the channel volume in decibels
	Tone.Meter.prototype.getDb = function(channel){
		return this.gainToDb(this.getLevel(channel));
	};

	// @returns {boolean} if the audio has clipped in the last 500ms
	Tone.Meter.prototype.isClipped = function(){
		return Date.now() - this.clipTime < 500;
	};

	//get the max value
	Tone.Meter.prototype.onprocess = function(event){
		var bufferSize = this.jsNode.bufferSize;
		for (var channel = 0; channel < this.channels; channel++){
			var input = event.inputBuffer.getChannelData(channel);
			var sum = 0;
			var total = 0;
			var x;
			var clipped = false;
			for (var i = 0; i < bufferSize; i++){
				x = input[i];
				if (!clipped && x > 0.95){
					clipped = true;
					this.clipTime = Date.now();
				}
				total += x;
		    	sum += x * x;
			}
			var average = total / bufferSize;
			var rms = Math.sqrt(sum / bufferSize);
			this.volume[channel] = Math.max(rms, this.volume[channel] * 0.8);
			this.values[channel] = average;
		}
	};

	return Tone.Meter;
});