me@1936: /**
me@1936:  *  loundess.js
me@1936:  *  Loudness module for the Web Audio Evaluation Toolbox
me@1936:  *  Allows for automatic calculation of loudness of Web Audio API Buffer objects,
me@1936:  * 	return gain values to correct for a target loudness or match loudness between
me@1936:  *  multiple objects
me@1936:  */
me@1936: 
me@1936: var interval_cal_loudness_event = null;
me@1936: 
me@1936: if (typeof OfflineAudioContext == "undefined"){
me@1936: 	var OfflineAudioContext = webkitOfflineAudioContext;
me@1936: }
me@1936: 
me@1936: function calculateLoudness(buffer, timescale, target, offlineContext)
me@1936: {
me@1936: 	// This function returns the EBU R 128 specification loudness model and sets the linear gain required to match -23 LUFS
me@1936: 	// buffer -> Web Audio API Buffer object
me@1936: 	// timescale -> M or Momentary (returns Array), S or Short (returns Array),
me@1936: 	//   I or Integrated (default, returns number)
me@1936: 	// target -> default is -23 LUFS but can be any LUFS measurement.
me@1936: 	
me@1936: 	if (buffer == undefined)
me@1936: 	{
me@1936: 		return 0;
me@1936: 	}
me@1936: 	if (timescale == undefined)
me@1936: 	{
me@1936: 		timescale = "I";
me@1936: 	}
me@1936: 	if (target == undefined)
me@1936: 	{
me@1936: 		target = -23;
me@1936: 	}
me@1936: 	if (offlineContext == undefined)
me@1936: 	{
me@1936: 		offlineContext = new OfflineAudioContext(audioContext.destination.channelCount, buffer.buffer.duration*audioContext.sampleRate, audioContext.sampleRate);
me@1936: 	}
me@1936: 	// Create the required filters
me@1936: 	var KFilter = offlineContext.createBiquadFilter();
me@1936: 	KFilter.type = "highshelf";
me@1936: 	KFilter.gain.value = 4;
me@1936: 	KFilter.frequency.value = 1500;
me@1936: 	
me@1936: 	var HPFilter = offlineContext.createBiquadFilter();
me@1936: 	HPFilter.type = "highpass";
me@1936: 	HPFilter.Q.value = 0.5;
me@1936: 	HPFilter.frequency.value = 38;
me@1936: 	// copy Data into the process buffer
me@1936: 	var processSource = offlineContext.createBufferSource();
me@1936: 	processSource.buffer = buffer.buffer;
me@1936: 	
me@1936: 	processSource.connect(KFilter);
me@1936: 	KFilter.connect(HPFilter);
me@1936: 	HPFilter.connect(offlineContext.destination);
me@1936: 	offlineContext.oncomplete = function(renderedBuffer) {
me@1936: 		// Have the renderedBuffer information, now continue processing
me@1936: 		if (typeof renderedBuffer.renderedBuffer == 'object') {
me@1936: 			renderedBuffer = renderedBuffer.renderedBuffer;
me@1936: 		}
me@1936: 		switch(timescale)
me@1936: 		{
me@1936: 		case "I":
me@1936:             // Calculate the Mean Squared of a signal
me@1936:             var MS = calculateMeanSquared(renderedBuffer,0.4,0.75);
me@1936:             // Calculate the Loudness of each block
me@1936:             var MSL = calculateLoudnessFromBlocks(MS);
me@1936:             // Get blocks from Absolute Gate
me@1936:             var LK = loudnessGate(MSL,MS,-70);
me@1936:             // Calculate Loudness
me@1936:             var LK_gate = loudnessOfBlocks(LK);
me@1936:             // Get blocks from Relative Gate
me@1936:             var RK = loudnessGate(MSL,MS,LK_gate-10);
me@1936:             var RK_gate = loudnessOfBlocks(RK);
me@1936:             buffer.buffer.lufs = RK_gate;
me@1936: 		}
me@1936:         buffer.ready();
me@1936: 	};
nickjillings@1939:     processSource.start(0);
me@1936: 	offlineContext.startRendering();
me@1936: }
me@1936: 
me@1936: function calculateMeanSquared(buffer,frame_dur,frame_overlap)
me@1936: {
me@1936:     frame_size = Math.floor(buffer.sampleRate*frame_dur);
me@1936:     step_size = Math.floor(frame_size*(1.0-frame_overlap));
me@1936:     num_frames = Math.floor((buffer.length-frame_size)/step_size);
me@1936:     
me@1936:     MS = Array(buffer.numberOfChannels);
me@1936:     for (var c=0; c<buffer.numberOfChannels; c++)
me@1936:     {
me@1936:         MS[c] = new Float32Array(num_frames);
me@1936:         var data = buffer.getChannelData(c);
me@1936:         for (var no=0; no<num_frames; no++)
me@1936:         {
me@1936:             MS[c][no] = 0.0;
me@1936:             for (var ptr=0; ptr<frame_size; ptr++)
me@1936:             {
me@1936:                 var sample = data[no*step_size+ptr];
me@1936:                 MS[c][no] += sample*sample;
me@1936:             }
me@1936:             MS[c][no] /= frame_size;
me@1936:         }
me@1936:     }
me@1936:     return MS;
me@1936: }
me@1936: 
me@1936: function calculateLoudnessFromBlocks(blocks)
me@1936: {
me@1936:     var num_frames = blocks[0].length;
me@1936:     var num_channels = blocks.length;
me@1936:     var MSL = Array(num_frames);
me@1936:     for (var n=0; n<num_frames; n++)
me@1936:     {
me@1936:         var sum = 0;
me@1936:         for (var c=0; c<num_channels; c++)
me@1936:         {
me@1936:             var G = 1.0;
me@1936:             if(G >= 3){G = 1.41;}
me@1936:             sum += blocks[c][n]*G;
me@1936:         }
me@1936:         MSL[n] = -0.691 + 10*Math.log10(sum);
me@1936:     }
me@1936:     return MSL;
me@1936: }
me@1936: 
me@1936: function loudnessGate(blocks,source,threshold)
me@1936: {
me@1936:     var num_frames = source[0].length;
me@1936:     var num_channels = source.length;
me@1936:     var LK = Array(num_channels);
me@1936:     for (var c=0; c<num_channels; c++)
me@1936:     {
me@1936:         LK[c] = [];
me@1936:     }
me@1936:     
me@1936:     for (var n=0; n<num_frames; n++)
me@1936:     {
me@1936:         if (blocks[n] > threshold)
me@1936:         {
me@1936:             for (var c=0; c<num_channels; c++)
me@1936:             {
me@1936:                 LK[c].push(source[c][n]);
me@1936:             }
me@1936:         }
me@1936:     }
me@1936:     return LK;
me@1936: }
me@1936: 
me@1936: function loudnessOfBlocks(blocks)
me@1936: {
me@1936:     var num_frames = blocks[0].length;
me@1936:     var num_channels = blocks.length;
me@1936:     var loudness = 0.0;
me@1936:     for (var n=0; n<num_frames; n++)
me@1936:     {
me@1936:         var sum = 0;
me@1936:         for (var c=0; c<num_channels; c++)
me@1936:         {
me@1936:             var G = 1.0;
me@1936:             if(G >= 3){G = 1.41;}
me@1936:             sum += blocks[c][n]*G;
me@1936:         }
me@1936:         sum /= num_frames;
me@1936:         loudness += sum;
me@1936:     }
me@1936:     loudness = -0.691 + 10 * Math.log10(loudness);
me@1936:     return loudness;
me@1936: }