n@792: /**
n@792:  *  loundess.js
n@792:  *  Loudness module for the Web Audio Evaluation Toolbox
n@792:  *  Allows for automatic calculation of loudness of Web Audio API Buffer objects,
n@792:  * 	return gain values to correct for a target loudness or match loudness between
n@792:  *  multiple objects
n@792:  */
n@792: 
n@792: function getLoudness(buffer, result, timescale, offlineContext)
n@792: {
n@792: 	// This function returns the EBU R 128 specification loudness model
n@792: 	// buffer -> Web Audio API Buffer object
n@792: 	// timescale -> M or Momentary (returns Array), S or Short (returns Array),
n@792: 	//   I or Integrated (default, returns number)
n@792: 	
n@792: 	// Create the required filters
n@792: 	if (buffer == undefined || result == undefined)
n@792: 	{
n@792: 		return 0;
n@792: 	}
n@792: 	if (timescale == undefined)
n@792: 	{
n@792: 		timescale = "I";
n@792: 	}
n@792: 	if (offlineContext == undefined)
n@792: 	{
n@792: 		offlineContext = new OfflineAudioContext(buffer.numberOfChannels, buffer.length, buffer.sampleRate);
n@792: 	}
n@792: 	var KFilter = offlineContext.createBiquadFilter();
n@792: 	KFilter.type = "highshelf";
n@792: 	KFilter.gain.value = 4;
n@792: 	KFilter.frequency.value = 1480;
n@792: 	
n@792: 	var HPFilter = offlineContext.createBiquadFilter();
n@792: 	HPFilter.type = "highpass";
n@792: 	HPFilter.Q.value = 0.707;
n@792: 	HPFilter.frequency.value = 60;
n@792: 	// copy Data into the process buffer
n@792: 	var processSource = offlineContext.createBufferSource();
n@792: 	processSource.buffer = buffer;
n@792: 	
n@792: 	processSource.connect(KFilter);
n@792: 	KFilter.connect(HPFilter);
n@792: 	HPFilter.connect(offlineContext.destination);
n@792: 	processSource.start();
n@792: 	offlineContext.startRendering().then(function(renderedBuffer) {
n@792: 		// Have the renderedBuffer information, now continue processing
n@792: 		console.log(renderedBuffer);
n@792: 		switch(timescale)
n@792: 		{
n@792: 		case "I":
n@792: 			var blockEnergy = calculateProcessedLoudness(renderedBuffer, 400, 0.75);
n@792: 			// Apply the absolute gate
n@792: 			var loudness = calculateLoudnessFromChannelBlocks(blockEnergy);
n@792: 			var absgatedEnergy = new Array(blockEnergy.length);
n@792: 			for (var c=0; c<blockEnergy.length; c++)
n@792: 			{
n@792: 				absgatedEnergy[c] = [];
n@792: 			}
n@792: 			for (var i=0; i<loudness.length; i++)
n@792: 			{
n@792: 				if (loudness[i] >= -70)
n@792: 				{
n@792: 					for (var c=0; c<blockEnergy.length; c++)
n@792: 					{
n@792: 						absgatedEnergy[c].push(blockEnergy[c][i]);
n@792: 					}
n@792: 				}
n@792: 			}
n@792: 			var overallAbsLoudness = calculateOverallLoudnessFromChannelBlocks(absgatedEnergy);
n@792: 			
n@792: 			//applying the relative gate 8 dB down from overallAbsLoudness
n@792: 			var relGateLevel = overallAbsLoudness - 8;
n@792: 			var relgateEnergy = new Array(blockEnergy.length);
n@792: 			for (var c=0; c<blockEnergy.length; c++)
n@792: 			{
n@792: 				relgateEnergy[c] = [];
n@792: 			}
n@792: 			for (var i=0; i<loudness.length; i++)
n@792: 			{
n@792: 				if (loudness[i] >= relGateLevel)
n@792: 				{
n@792: 					for (var c=0; c<blockEnergy.length; c++)
n@792: 					{
n@792: 						relgateEnergy[c].push(blockEnergy[c][i]);
n@792: 					}
n@792: 				}
n@792: 			}
n@792: 			var overallRelLoudness = calculateOverallLoudnessFromChannelBlocks(relgateEnergy);
n@792: 			result[0] =  overallRelLoudness;
n@792: 		}
n@792: 	}).catch(function(err) {
n@792: 		console.log(err);
n@792: 		result[0] = 1;
n@792: 	});
n@792: }
n@792: 
n@792: function calculateProcessedLoudness(buffer, winDur, overlap)
n@792: {
n@792: 	// Buffer		Web Audio buffer node
n@792: 	// winDur		Window Duration in milliseconds
n@792: 	// overlap		Window overlap as normalised (0.5 = 50% overlap);
n@792: 	if (buffer == undefined)
n@792: 	{
n@792: 		return 0;
n@792: 	}
n@792: 	if (winDur == undefined)
n@792: 	{
n@792: 		winDur = 400;
n@792: 	}
n@792: 	if (overlap == undefined)
n@792: 	{
n@792: 		overlap = 0.5;
n@792: 	}
n@792: 	var winSize = buffer.sampleRate*winDur/1000;
n@792: 	var olapSize = overlap*winSize;
n@792: 	var numberOfFrames = Math.floor(buffer.length/olapSize - winSize/olapSize + 1);
n@792: 	var blockEnergy = new Array(buffer.numberOfChannels);
n@792: 	for (var channel = 0; channel < buffer.numberOfChannels; channel++)
n@792: 	{
n@792: 		blockEnergy[channel] = new Float32Array(numberOfFrames);
n@792: 		var data = buffer.getChannelData(channel);
n@792: 		for (var i=0; i<numberOfFrames; i++)
n@792: 		{
n@792: 			var sigma = 0;
n@792: 			for (var n=i*olapSize; n < i*olapSize+winSize; n++)
n@792: 			{
n@792: 				sigma += Math.pow(data[n],2);
n@792: 			}
n@792: 			blockEnergy[channel][i] = sigma/winSize;
n@792: 		}
n@792: 	}
n@792: 	return blockEnergy;
n@792: }
n@792: function calculateLoudnessFromChannelBlocks(blockEnergy)
n@792: {
n@792: 	// Loudness
n@792: 	var loudness = new Float32Array(blockEnergy[0].length);
n@792: 	for (var i=0; i<blockEnergy[0].length; i++)
n@792: 	{
n@792: 		var sigma = 0;
n@792: 		for (var channel = 0; channel < blockEnergy.length; channel++)
n@792: 		{
n@792: 			var G = 1.0;
n@792: 			if (channel >= 4) {G = 1.41;}
n@792: 			sigma += blockEnergy[channel][i]*G;
n@792: 		}
n@792: 		loudness[i] = -0.691 + 10*Math.log10(sigma);
n@792: 	}
n@792: 	return loudness;
n@792: }
n@792: function calculateOverallLoudnessFromChannelBlocks(blockEnergy)
n@792: {
n@792: 	// Loudness
n@792: 	var summation = 0;
n@792: 	for (var channel = 0; channel < blockEnergy.length; channel++)
n@792: 	{
n@792: 		var G = 1.0;
n@792: 		if (channel >= 4) {G = 1.41;}
n@792: 		var sigma = 0;
n@792: 		for (var i=0; i<blockEnergy[0].length; i++)
n@792: 		{
n@792: 			blockEnergy[channel][i] *= G;
n@792: 			sigma += blockEnergy[channel][i];
n@792: 		}
n@792: 		sigma /= blockEnergy.length;
n@792: 		summation+= sigma;
n@792: 	}
n@792: 	return -0.691 + 10*Math.log10(summation);;
n@792: }