nicholas@2224: /**
nicholas@2224:  *  loundess.js
nicholas@2224:  *  Loudness module for the Web Audio Evaluation Toolbox
nicholas@2224:  *  Allows for automatic calculation of loudness of Web Audio API Buffer objects,
nicholas@2224:  * 	return gain values to correct for a target loudness or match loudness between
nicholas@2224:  *  multiple objects
nicholas@2224:  */
nicholas@2224: 
nicholas@2224: var interval_cal_loudness_event = null;
nicholas@2224: 
nicholas@2224: if (typeof OfflineAudioContext == "undefined"){
nicholas@2224: 	var OfflineAudioContext = webkitOfflineAudioContext;
nicholas@2224: }
nicholas@2224: 
nicholas@2224: function calculateLoudness(buffer, timescale, target, offlineContext)
nicholas@2224: {
nicholas@2224: 	// This function returns the EBU R 128 specification loudness model and sets the linear gain required to match -23 LUFS
nicholas@2224: 	// buffer -> Web Audio API Buffer object
nicholas@2224: 	// timescale -> M or Momentary (returns Array), S or Short (returns Array),
nicholas@2224: 	//   I or Integrated (default, returns number)
nicholas@2224: 	// target -> default is -23 LUFS but can be any LUFS measurement.
nicholas@2224: 	
nicholas@2224: 	if (buffer == undefined)
nicholas@2224: 	{
nicholas@2224: 		return 0;
nicholas@2224: 	}
nicholas@2224: 	if (timescale == undefined)
nicholas@2224: 	{
nicholas@2224: 		timescale = "I";
nicholas@2224: 	}
nicholas@2224: 	if (target == undefined)
nicholas@2224: 	{
nicholas@2224: 		target = -23;
nicholas@2224: 	}
nicholas@2224: 	if (offlineContext == undefined)
nicholas@2224: 	{
nicholas@2224: 		offlineContext = new OfflineAudioContext(audioContext.destination.channelCount, buffer.buffer.duration*audioContext.sampleRate, audioContext.sampleRate);
nicholas@2224: 	}
nicholas@2224: 	// Create the required filters
nicholas@2224: 	var KFilter = offlineContext.createBiquadFilter();
nicholas@2224: 	KFilter.type = "highshelf";
nicholas@2224: 	KFilter.gain.value = 4;
nicholas@2224: 	KFilter.frequency.value = 1500;
nicholas@2224: 	
nicholas@2224: 	var HPFilter = offlineContext.createBiquadFilter();
nicholas@2224: 	HPFilter.type = "highpass";
nicholas@2224: 	HPFilter.Q.value = 0.5;
nicholas@2224: 	HPFilter.frequency.value = 38;
nicholas@2224: 	// copy Data into the process buffer
nicholas@2224: 	var processSource = offlineContext.createBufferSource();
nicholas@2224: 	processSource.buffer = buffer.buffer;
nicholas@2224: 	
nicholas@2224: 	processSource.connect(KFilter);
nicholas@2224: 	KFilter.connect(HPFilter);
nicholas@2224: 	HPFilter.connect(offlineContext.destination);
nicholas@2224: 	offlineContext.oncomplete = function(renderedBuffer) {
nicholas@2224: 		// Have the renderedBuffer information, now continue processing
nicholas@2224: 		if (typeof renderedBuffer.renderedBuffer == 'object') {
nicholas@2224: 			renderedBuffer = renderedBuffer.renderedBuffer;
nicholas@2224: 		}
nicholas@2224: 		switch(timescale)
nicholas@2224: 		{
nicholas@2224: 		case "I":
nicholas@2224:             // Calculate the Mean Squared of a signal
nicholas@2224:             var MS = calculateMeanSquared(renderedBuffer,0.4,0.75);
nicholas@2224:             // Calculate the Loudness of each block
nicholas@2224:             var MSL = calculateLoudnessFromBlocks(MS);
nicholas@2224:             // Get blocks from Absolute Gate
nicholas@2224:             var LK = loudnessGate(MSL,MS,-70);
nicholas@2224:             // Calculate Loudness
nicholas@2224:             var LK_gate = loudnessOfBlocks(LK);
nicholas@2224:             // Get blocks from Relative Gate
nicholas@2224:             var RK = loudnessGate(MSL,MS,LK_gate-10);
nicholas@2224:             var RK_gate = loudnessOfBlocks(RK);
nicholas@2224:             buffer.buffer.lufs = RK_gate;
nicholas@2224: 		}
nicholas@2224:         buffer.ready();
nicholas@2224: 	};
nicholas@2224:     processSource.start(0);
nicholas@2224: 	offlineContext.startRendering();
nicholas@2224: }
nicholas@2224: 
nicholas@2224: function calculateMeanSquared(buffer,frame_dur,frame_overlap)
nicholas@2224: {
nicholas@2224:     frame_size = Math.floor(buffer.sampleRate*frame_dur);
nicholas@2224:     step_size = Math.floor(frame_size*(1.0-frame_overlap));
nicholas@2224:     num_frames = Math.floor((buffer.length-frame_size)/step_size);
nicholas@2224:     
nicholas@2224:     MS = Array(buffer.numberOfChannels);
nicholas@2224:     for (var c=0; c<buffer.numberOfChannels; c++)
nicholas@2224:     {
nicholas@2224:         MS[c] = new Float32Array(num_frames);
nicholas@2224:         var data = buffer.getChannelData(c);
nicholas@2224:         for (var no=0; no<num_frames; no++)
nicholas@2224:         {
nicholas@2224:             MS[c][no] = 0.0;
nicholas@2224:             for (var ptr=0; ptr<frame_size; ptr++)
nicholas@2224:             {
nicholas@2224:                 var sample = data[no*step_size+ptr];
nicholas@2224:                 MS[c][no] += sample*sample;
nicholas@2224:             }
nicholas@2224:             MS[c][no] /= frame_size;
nicholas@2224:         }
nicholas@2224:     }
nicholas@2224:     return MS;
nicholas@2224: }
nicholas@2224: 
nicholas@2224: function calculateLoudnessFromBlocks(blocks)
nicholas@2224: {
nicholas@2224:     var num_frames = blocks[0].length;
nicholas@2224:     var num_channels = blocks.length;
nicholas@2224:     var MSL = Array(num_frames);
nicholas@2224:     for (var n=0; n<num_frames; n++)
nicholas@2224:     {
nicholas@2224:         var sum = 0;
nicholas@2224:         for (var c=0; c<num_channels; c++)
nicholas@2224:         {
nicholas@2224:             var G = 1.0;
nicholas@2224:             if(G >= 3){G = 1.41;}
nicholas@2224:             sum += blocks[c][n]*G;
nicholas@2224:         }
nicholas@2224:         MSL[n] = -0.691 + 10*Math.log10(sum);
nicholas@2224:     }
nicholas@2224:     return MSL;
nicholas@2224: }
nicholas@2224: 
nicholas@2224: function loudnessGate(blocks,source,threshold)
nicholas@2224: {
nicholas@2224:     var num_frames = source[0].length;
nicholas@2224:     var num_channels = source.length;
nicholas@2224:     var LK = Array(num_channels);
nicholas@2224:     for (var c=0; c<num_channels; c++)
nicholas@2224:     {
nicholas@2224:         LK[c] = [];
nicholas@2224:     }
nicholas@2224:     
nicholas@2224:     for (var n=0; n<num_frames; n++)
nicholas@2224:     {
nicholas@2224:         if (blocks[n] > threshold)
nicholas@2224:         {
nicholas@2224:             for (var c=0; c<num_channels; c++)
nicholas@2224:             {
nicholas@2224:                 LK[c].push(source[c][n]);
nicholas@2224:             }
nicholas@2224:         }
nicholas@2224:     }
nicholas@2224:     return LK;
nicholas@2224: }
nicholas@2224: 
nicholas@2224: function loudnessOfBlocks(blocks)
nicholas@2224: {
nicholas@2224:     var num_frames = blocks[0].length;
nicholas@2224:     var num_channels = blocks.length;
nicholas@2224:     var loudness = 0.0;
nicholas@2224:     for (var n=0; n<num_frames; n++)
nicholas@2224:     {
nicholas@2224:         var sum = 0;
nicholas@2224:         for (var c=0; c<num_channels; c++)
nicholas@2224:         {
nicholas@2224:             var G = 1.0;
nicholas@2224:             if(G >= 3){G = 1.41;}
nicholas@2224:             sum += blocks[c][n]*G;
nicholas@2224:         }
nicholas@2224:         sum /= num_frames;
nicholas@2224:         loudness += sum;
nicholas@2224:     }
nicholas@2224:     loudness = -0.691 + 10 * Math.log10(loudness);
nicholas@2224:     return loudness;
nicholas@2224: }