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@793: var interval_cal_loudness_event = null;
n@793: 
nicholas@752: if (typeof OfflineAudioContext == "undefined"){
nicholas@752: 	var OfflineAudioContext = webkitOfflineAudioContext;
nicholas@752: }
nicholas@752: 
n@793: function calculateLoudness(buffer, timescale, target, offlineContext)
n@792: {
n@793: 	// This function returns the EBU R 128 specification loudness model and sets the linear gain required to match -23 LUFS
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@793: 	// target -> default is -23 LUFS but can be any LUFS measurement.
n@792: 	
n@793: 	if (buffer == undefined)
n@792: 	{
n@792: 		return 0;
n@792: 	}
n@792: 	if (timescale == undefined)
n@792: 	{
n@792: 		timescale = "I";
n@792: 	}
n@793: 	if (target == undefined)
n@793: 	{
n@793: 		target = -23;
n@793: 	}
n@792: 	if (offlineContext == undefined)
n@792: 	{
n@1158: 		offlineContext = new OfflineAudioContext(audioContext.destination.channelCount, buffer.buffer.duration*audioContext.sampleRate, audioContext.sampleRate);
n@792: 	}
n@793: 	// Create the required filters
n@792: 	var KFilter = offlineContext.createBiquadFilter();
n@792: 	KFilter.type = "highshelf";
n@792: 	KFilter.gain.value = 4;
n@1166: 	KFilter.frequency.value = 1500;
n@792: 	
n@792: 	var HPFilter = offlineContext.createBiquadFilter();
n@792: 	HPFilter.type = "highpass";
n@1166: 	HPFilter.Q.value = 0.5;
n@1166: 	HPFilter.frequency.value = 38;
n@792: 	// copy Data into the process buffer
n@792: 	var processSource = offlineContext.createBufferSource();
n@1142: 	processSource.buffer = buffer.buffer;
n@792: 	
n@792: 	processSource.connect(KFilter);
n@792: 	KFilter.connect(HPFilter);
n@792: 	HPFilter.connect(offlineContext.destination);
nicholas@752: 	offlineContext.oncomplete = function(renderedBuffer) {
n@792: 		// Have the renderedBuffer information, now continue processing
nicholas@752: 		if (typeof renderedBuffer.renderedBuffer == 'object') {
nicholas@752: 			renderedBuffer = renderedBuffer.renderedBuffer;
nicholas@752: 		}
n@792: 		switch(timescale)
n@792: 		{
n@792: 		case "I":
n@1157:             // Calculate the Mean Squared of a signal
n@1157:             var MS = calculateMeanSquared(renderedBuffer,0.4,0.75);
n@1157:             // Calculate the Loudness of each block
n@1157:             var MSL = calculateLoudnessFromBlocks(MS);
n@1157:             // Get blocks from Absolute Gate
n@1157:             var LK = loudnessGate(MSL,MS,-70);
n@1157:             // Calculate Loudness
n@1157:             var LK_gate = loudnessOfBlocks(LK);
n@1157:             // Get blocks from Relative Gate
n@1157:             var RK = loudnessGate(MSL,MS,LK_gate-10);
n@1157:             var RK_gate = loudnessOfBlocks(RK);
n@1157:             buffer.buffer.lufs = RK_gate;
n@792: 		}
n@1159:         buffer.ready();
nicholas@752: 	};
n@1211:     processSource.start(0);
nicholas@752: 	offlineContext.startRendering();
n@792: }
n@792: 
n@1157: function calculateMeanSquared(buffer,frame_dur,frame_overlap)
n@792: {
n@1157:     frame_size = Math.floor(buffer.sampleRate*frame_dur);
n@1157:     step_size = Math.floor(frame_size*(1.0-frame_overlap));
n@1157:     num_frames = Math.floor((buffer.length-frame_size)/step_size);
n@1157:     
n@1157:     MS = Array(buffer.numberOfChannels);
n@1157:     for (var c=0; c<buffer.numberOfChannels; c++)
n@1157:     {
n@1157:         MS[c] = new Float32Array(num_frames);
n@1157:         var data = buffer.getChannelData(c);
n@1157:         for (var no=0; no<num_frames; no++)
n@1157:         {
n@1157:             MS[c][no] = 0.0;
n@1157:             for (var ptr=0; ptr<frame_size; ptr++)
n@1157:             {
n@1157:                 var sample = data[no*step_size+ptr];
n@1157:                 MS[c][no] += sample*sample;
n@1157:             }
n@1157:             MS[c][no] /= frame_size;
n@1157:         }
n@1157:     }
n@1157:     return MS;
n@792: }
n@1157: 
n@1157: function calculateLoudnessFromBlocks(blocks)
n@792: {
n@1157:     var num_frames = blocks[0].length;
n@1157:     var num_channels = blocks.length;
n@1157:     var MSL = Array(num_frames);
n@1157:     for (var n=0; n<num_frames; n++)
n@1157:     {
n@1157:         var sum = 0;
n@1157:         for (var c=0; c<num_channels; c++)
n@1157:         {
n@1157:             var G = 1.0;
n@1157:             if(G >= 3){G = 1.41;}
n@1157:             sum += blocks[c][n]*G;
n@1157:         }
n@1157:         MSL[n] = -0.691 + 10*Math.log10(sum);
n@1157:     }
n@1157:     return MSL;
n@792: }
n@1157: 
n@1157: function loudnessGate(blocks,source,threshold)
n@792: {
n@1157:     var num_frames = source[0].length;
n@1157:     var num_channels = source.length;
n@1157:     var LK = Array(num_channels);
n@1157:     for (var c=0; c<num_channels; c++)
n@1157:     {
n@1157:         LK[c] = [];
n@1157:     }
n@1157:     
n@1157:     for (var n=0; n<num_frames; n++)
n@1157:     {
n@1157:         if (blocks[n] > threshold)
n@1157:         {
n@1157:             for (var c=0; c<num_channels; c++)
n@1157:             {
n@1157:                 LK[c].push(source[c][n]);
n@1157:             }
n@1157:         }
n@1157:     }
n@1157:     return LK;
n@792: }
n@1157: 
n@1157: function loudnessOfBlocks(blocks)
n@1157: {
n@1157:     var num_frames = blocks[0].length;
n@1157:     var num_channels = blocks.length;
n@1157:     var loudness = 0.0;
n@1157:     for (var n=0; n<num_frames; n++)
n@1157:     {
n@1157:         var sum = 0;
n@1157:         for (var c=0; c<num_channels; c++)
n@1157:         {
n@1157:             var G = 1.0;
n@1157:             if(G >= 3){G = 1.41;}
n@1157:             sum += blocks[c][n]*G;
n@1157:         }
n@1157:         sum /= num_frames;
n@1157:         loudness += sum;
n@1157:     }
n@1157:     loudness = -0.691 + 10 * Math.log10(loudness);
n@1157:     return loudness;
n@1157: }