nickjillings@1318: /**
nickjillings@1318:  *  loundess.js
nickjillings@1318:  *  Loudness module for the Web Audio Evaluation Toolbox
nickjillings@1318:  *  Allows for automatic calculation of loudness of Web Audio API Buffer objects,
nickjillings@1318:  * 	return gain values to correct for a target loudness or match loudness between
nickjillings@1318:  *  multiple objects
nickjillings@1318:  */
nickjillings@1318: 
nickjillings@1318: var interval_cal_loudness_event = null;
nickjillings@1318: 
nickjillings@1318: if (typeof OfflineAudioContext == "undefined"){
nickjillings@1318: 	var OfflineAudioContext = webkitOfflineAudioContext;
nickjillings@1318: }
nickjillings@1318: 
nickjillings@1318: function calculateLoudness(buffer, timescale, target, offlineContext)
nickjillings@1318: {
nickjillings@1318: 	// This function returns the EBU R 128 specification loudness model and sets the linear gain required to match -23 LUFS
nickjillings@1318: 	// buffer -> Web Audio API Buffer object
nickjillings@1318: 	// timescale -> M or Momentary (returns Array), S or Short (returns Array),
nickjillings@1318: 	//   I or Integrated (default, returns number)
nickjillings@1318: 	// target -> default is -23 LUFS but can be any LUFS measurement.
nickjillings@1318: 	
nickjillings@1318: 	if (buffer == undefined)
nickjillings@1318: 	{
nickjillings@1318: 		return 0;
nickjillings@1318: 	}
nickjillings@1318: 	if (timescale == undefined)
nickjillings@1318: 	{
nickjillings@1318: 		timescale = "I";
nickjillings@1318: 	}
nickjillings@1318: 	if (target == undefined)
nickjillings@1318: 	{
nickjillings@1318: 		target = -23;
nickjillings@1318: 	}
nickjillings@1318: 	if (offlineContext == undefined)
nickjillings@1318: 	{
nickjillings@1318: 		offlineContext = new OfflineAudioContext(buffer.numberOfChannels, buffer.length, buffer.sampleRate);
nickjillings@1318: 	}
nickjillings@1318: 	// Create the required filters
nickjillings@1318: 	var KFilter = offlineContext.createBiquadFilter();
nickjillings@1318: 	KFilter.type = "highshelf";
nickjillings@1318: 	KFilter.gain.value = 4;
nickjillings@1318: 	KFilter.frequency.value = 1480;
nickjillings@1318: 	
nickjillings@1318: 	var HPFilter = offlineContext.createBiquadFilter();
nickjillings@1318: 	HPFilter.type = "highpass";
nickjillings@1318: 	HPFilter.Q.value = 0.707;
nickjillings@1318: 	HPFilter.frequency.value = 60;
nickjillings@1318: 	// copy Data into the process buffer
nickjillings@1318: 	var processSource = offlineContext.createBufferSource();
nickjillings@1318: 	processSource.buffer = buffer;
nickjillings@1318: 	
nickjillings@1318: 	processSource.connect(KFilter);
nickjillings@1318: 	KFilter.connect(HPFilter);
nickjillings@1318: 	HPFilter.connect(offlineContext.destination);
nickjillings@1318: 	processSource.start();
nickjillings@1318: 	offlineContext.oncomplete = function(renderedBuffer) {
nickjillings@1318: 		// Have the renderedBuffer information, now continue processing
nickjillings@1318: 		if (typeof renderedBuffer.renderedBuffer == 'object') {
nickjillings@1318: 			renderedBuffer = renderedBuffer.renderedBuffer;
nickjillings@1318: 		}
nickjillings@1318: 		switch(timescale)
nickjillings@1318: 		{
nickjillings@1318: 		case "I":
nickjillings@1318: 			var blockEnergy = calculateProcessedLoudness(renderedBuffer, 400, 0.75);
nickjillings@1318: 			// Apply the absolute gate
nickjillings@1318: 			var loudness = calculateLoudnessFromChannelBlocks(blockEnergy);
nickjillings@1318: 			var absgatedEnergy = new Array(blockEnergy.length);
nickjillings@1318: 			for (var c=0; c<blockEnergy.length; c++)
nickjillings@1318: 			{
nickjillings@1318: 				absgatedEnergy[c] = [];
nickjillings@1318: 			}
nickjillings@1318: 			for (var i=0; i<loudness.length; i++)
nickjillings@1318: 			{
nickjillings@1318: 				if (loudness[i] >= -70)
nickjillings@1318: 				{
nickjillings@1318: 					for (var c=0; c<blockEnergy.length; c++)
nickjillings@1318: 					{
nickjillings@1318: 						absgatedEnergy[c].push(blockEnergy[c][i]);
nickjillings@1318: 					}
nickjillings@1318: 				}
nickjillings@1318: 			}
nickjillings@1318: 			var overallAbsLoudness = calculateOverallLoudnessFromChannelBlocks(absgatedEnergy);
nickjillings@1318: 			
nickjillings@1318: 			//applying the relative gate 8 dB down from overallAbsLoudness
nickjillings@1318: 			var relGateLevel = overallAbsLoudness - 8;
nickjillings@1318: 			var relgateEnergy = new Array(blockEnergy.length);
nickjillings@1318: 			for (var c=0; c<blockEnergy.length; c++)
nickjillings@1318: 			{
nickjillings@1318: 				relgateEnergy[c] = [];
nickjillings@1318: 			}
nickjillings@1318: 			for (var i=0; i<loudness.length; i++)
nickjillings@1318: 			{
nickjillings@1318: 				if (loudness[i] >= relGateLevel)
nickjillings@1318: 				{
nickjillings@1318: 					for (var c=0; c<blockEnergy.length; c++)
nickjillings@1318: 					{
nickjillings@1318: 						relgateEnergy[c].push(blockEnergy[c][i]);
nickjillings@1318: 					}
nickjillings@1318: 				}
nickjillings@1318: 			}
nickjillings@1318: 			var overallRelLoudness = calculateOverallLoudnessFromChannelBlocks(relgateEnergy);
nickjillings@1318: 			buffer.lufs =  overallRelLoudness;
nickjillings@1318: 		}
nickjillings@1318: 	};
nickjillings@1318: 	offlineContext.startRendering();
nickjillings@1318: }
nickjillings@1318: 
nickjillings@1318: function calculateProcessedLoudness(buffer, winDur, overlap)
nickjillings@1318: {
nickjillings@1318: 	// Buffer		Web Audio buffer node
nickjillings@1318: 	// winDur		Window Duration in milliseconds
nickjillings@1318: 	// overlap		Window overlap as normalised (0.5 = 50% overlap);
nickjillings@1318: 	if (buffer == undefined)
nickjillings@1318: 	{
nickjillings@1318: 		return 0;
nickjillings@1318: 	}
nickjillings@1318: 	if (winDur == undefined)
nickjillings@1318: 	{
nickjillings@1318: 		winDur = 400;
nickjillings@1318: 	}
nickjillings@1318: 	if (overlap == undefined)
nickjillings@1318: 	{
nickjillings@1318: 		overlap = 0.5;
nickjillings@1318: 	}
nickjillings@1318: 	var winSize = buffer.sampleRate*winDur/1000;
nickjillings@1318: 	var olapSize = (1-overlap)*winSize;
nickjillings@1318: 	var numberOfFrames = Math.floor(buffer.length/olapSize - winSize/olapSize + 1);
nickjillings@1318: 	var blockEnergy = new Array(buffer.numberOfChannels);
nickjillings@1318: 	for (var channel = 0; channel < buffer.numberOfChannels; channel++)
nickjillings@1318: 	{
nickjillings@1318: 		blockEnergy[channel] = new Float32Array(numberOfFrames);
nickjillings@1318: 		var data = buffer.getChannelData(channel);
nickjillings@1318: 		for (var i=0; i<numberOfFrames; i++)
nickjillings@1318: 		{
nickjillings@1318: 			var sigma = 0;
nickjillings@1318: 			for (var n=i*olapSize; n < i*olapSize+winSize; n++)
nickjillings@1318: 			{
nickjillings@1318: 				sigma += Math.pow(data[n],2);
nickjillings@1318: 			}
nickjillings@1318: 			blockEnergy[channel][i] = sigma/winSize;
nickjillings@1318: 		}
nickjillings@1318: 	}
nickjillings@1318: 	return blockEnergy;
nickjillings@1318: }
nickjillings@1318: function calculateLoudnessFromChannelBlocks(blockEnergy)
nickjillings@1318: {
nickjillings@1318: 	// Loudness
nickjillings@1318: 	var loudness = new Float32Array(blockEnergy[0].length);
nickjillings@1318: 	for (var i=0; i<blockEnergy[0].length; i++)
nickjillings@1318: 	{
nickjillings@1318: 		var sigma = 0;
nickjillings@1318: 		for (var channel = 0; channel < blockEnergy.length; channel++)
nickjillings@1318: 		{
nickjillings@1318: 			var G = 1.0;
nickjillings@1318: 			if (channel >= 4) {G = 1.41;}
nickjillings@1318: 			sigma += blockEnergy[channel][i]*G;
nickjillings@1318: 		}
nickjillings@1318: 		loudness[i] = -0.691 + 10*Math.log10(sigma);
nickjillings@1318: 	}
nickjillings@1318: 	return loudness;
nickjillings@1318: }
nickjillings@1318: function calculateOverallLoudnessFromChannelBlocks(blockEnergy)
nickjillings@1318: {
nickjillings@1318: 	// Loudness
nickjillings@1318: 	var summation = 0;
nickjillings@1318: 	for (var channel = 0; channel < blockEnergy.length; channel++)
nickjillings@1318: 	{
nickjillings@1318: 		var G = 1.0;
nickjillings@1318: 		if (channel >= 4) {G = 1.41;}
nickjillings@1318: 		var sigma = 0;
nickjillings@1318: 		for (var i=0; i<blockEnergy[0].length; i++)
nickjillings@1318: 		{
nickjillings@1318: 			blockEnergy[channel][i] *= G;
nickjillings@1318: 			sigma += blockEnergy[channel][i];
nickjillings@1318: 		}
nickjillings@1318: 		sigma /= blockEnergy.length;
nickjillings@1318: 		summation+= sigma;
nickjillings@1318: 	}
nickjillings@1318: 	return -0.691 + 10*Math.log10(summation);;
nickjillings@1318: }