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@2690: /* globals webkitOfflineAudioContext, navigator, audioContext, Float32Array */
nicholas@2224: var interval_cal_loudness_event = null;
nicholas@2224: 
nicholas@2538: if (typeof OfflineAudioContext == "undefined") {
nicholas@2538:     var OfflineAudioContext = webkitOfflineAudioContext;
nicholas@2224: }
nicholas@2224: 
nicholas@2538: function calculateLoudness(buffer, timescale, target, offlineContext) {
nicholas@2538:     // This function returns the EBU R 128 specification loudness model and sets the linear gain required to match -23 LUFS
nicholas@2538:     // buffer -> Web Audio API Buffer object
nicholas@2538:     // timescale -> M or Momentary (returns Array), S or Short (returns Array),
nicholas@2538:     //   I or Integrated (default, returns number)
nicholas@2538:     // target -> default is -23 LUFS but can be any LUFS measurement.
nicholas@2538:     if (navigator.platform == 'iPad' || navigator.platform == 'iPhone') {
n@2432:         buffer.ready();
n@2432:     }
nicholas@2690:     if (buffer === undefined) {
nicholas@2538:         return 0;
nicholas@2538:     }
nicholas@2690:     if (timescale === undefined) {
nicholas@2538:         timescale = "I";
nicholas@2538:     }
nicholas@2690:     if (target === undefined) {
nicholas@2538:         target = -23;
nicholas@2538:     }
nicholas@2690:     if (offlineContext === undefined) {
n@2925:         offlineContext = new OfflineAudioContext(audioContext.destination.channelCount, Math.max(0.4, buffer.buffer.duration) * audioContext.sampleRate, audioContext.sampleRate);
nicholas@2538:     }
nicholas@2538:     // Create the required filters
nicholas@2538:     var KFilter = offlineContext.createBiquadFilter();
nicholas@2538:     KFilter.type = "highshelf";
nicholas@2538:     KFilter.gain.value = 4;
nicholas@2538:     KFilter.frequency.value = 1500;
nicholas@2538: 
nicholas@2538:     var HPFilter = offlineContext.createBiquadFilter();
nicholas@2538:     HPFilter.type = "highpass";
nicholas@2538:     HPFilter.Q.value = 0.5;
nicholas@2538:     HPFilter.frequency.value = 38;
nicholas@2538:     // copy Data into the process buffer
nicholas@2538:     var processSource = offlineContext.createBufferSource();
nicholas@2538:     processSource.buffer = buffer.buffer;
nicholas@2538: 
nicholas@2538:     processSource.connect(KFilter);
nicholas@2538:     KFilter.connect(HPFilter);
nicholas@2538:     HPFilter.connect(offlineContext.destination);
nicholas@2538:     offlineContext.oncomplete = function (renderedBuffer) {
nicholas@2538:         // Have the renderedBuffer information, now continue processing
nicholas@2538:         if (typeof renderedBuffer.renderedBuffer == 'object') {
nicholas@2538:             renderedBuffer = renderedBuffer.renderedBuffer;
nicholas@2538:         }
nicholas@2538:         switch (timescale) {
nicholas@2538:             case "I":
nicholas@2538:                 // Calculate the Mean Squared of a signal
nicholas@2538:                 var MS = calculateMeanSquared(renderedBuffer, 0.4, 0.75);
nicholas@2538:                 // Calculate the Loudness of each block
nicholas@2538:                 var MSL = calculateLoudnessFromBlocks(MS);
nicholas@2538:                 // Get blocks from Absolute Gate
nicholas@2538:                 var LK = loudnessGate(MSL, MS, -70);
nicholas@2538:                 // Calculate Loudness
nicholas@2538:                 var LK_gate = loudnessOfBlocks(LK);
nicholas@2538:                 // Get blocks from Relative Gate
nicholas@2538:                 var RK = loudnessGate(MSL, MS, LK_gate - 10);
nicholas@2538:                 var RK_gate = loudnessOfBlocks(RK);
nicholas@2538:                 buffer.buffer.lufs = RK_gate;
nicholas@2538:         }
nicholas@2224:         buffer.ready();
nicholas@2538:     };
nicholas@2224:     processSource.start(0);
nicholas@2538:     offlineContext.startRendering();
nicholas@2224: }
nicholas@2224: 
nicholas@2538: function calculateMeanSquared(buffer, frame_dur, frame_overlap) {
nicholas@2690:     var frame_size = Math.floor(buffer.sampleRate * frame_dur);
nicholas@2690:     var step_size = Math.floor(frame_size * (1.0 - frame_overlap));
nicholas@2690:     var num_frames = Math.floor((buffer.length - frame_size) / step_size);
n@2925:     num_frames = Math.max(num_frames, 1);
nicholas@2538: 
nicholas@2690:     var MS = Array(buffer.numberOfChannels);
nicholas@2538:     for (var c = 0; c < buffer.numberOfChannels; c++) {
nicholas@2224:         MS[c] = new Float32Array(num_frames);
nicholas@2224:         var data = buffer.getChannelData(c);
nicholas@2538:         for (var no = 0; no < num_frames; no++) {
nicholas@2224:             MS[c][no] = 0.0;
nicholas@2538:             for (var ptr = 0; ptr < frame_size; ptr++) {
nicholas@2672:                 var i = no * step_size + ptr;
nicholas@2672:                 if (i >= buffer.length) {
nicholas@2672:                     break;
nicholas@2672:                 }
nicholas@2672:                 var sample = data[i];
nicholas@2538:                 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@2538: function calculateLoudnessFromBlocks(blocks) {
nicholas@2224:     var num_frames = blocks[0].length;
nicholas@2224:     var num_channels = blocks.length;
nicholas@2224:     var MSL = Array(num_frames);
nicholas@2538:     for (var n = 0; n < num_frames; n++) {
nicholas@2224:         var sum = 0;
nicholas@2538:         for (var c = 0; c < num_channels; c++) {
nicholas@2224:             var G = 1.0;
nicholas@2538:             if (G >= 3) {
nicholas@2538:                 G = 1.41;
nicholas@2538:             }
nicholas@2538:             sum += blocks[c][n] * G;
nicholas@2224:         }
nicholas@2538:         MSL[n] = -0.691 + 10 * Math.log10(sum);
nicholas@2224:     }
nicholas@2224:     return MSL;
nicholas@2224: }
nicholas@2224: 
nicholas@2538: function loudnessGate(blocks, source, threshold) {
nicholas@2224:     var num_frames = source[0].length;
nicholas@2224:     var num_channels = source.length;
nicholas@2224:     var LK = Array(num_channels);
nicholas@2690:     var n, c;
nicholas@2690:     for (c = 0; c < num_channels; c++) {
nicholas@2224:         LK[c] = [];
nicholas@2224:     }
nicholas@2538: 
nicholas@2690:     for (n = 0; n < num_frames; n++) {
nicholas@2538:         if (blocks[n] > threshold) {
nicholas@2690:             for (c = 0; c < num_channels; c++) {
nicholas@2224:                 LK[c].push(source[c][n]);
nicholas@2224:             }
nicholas@2224:         }
nicholas@2224:     }
nicholas@2224:     return LK;
nicholas@2224: }
nicholas@2224: 
nicholas@2538: function loudnessOfBlocks(blocks) {
nicholas@2224:     var num_frames = blocks[0].length;
nicholas@2224:     var num_channels = blocks.length;
nicholas@2224:     var loudness = 0.0;
nicholas@2538:     for (var n = 0; n < num_frames; n++) {
nicholas@2224:         var sum = 0;
nicholas@2538:         for (var c = 0; c < num_channels; c++) {
nicholas@2224:             var G = 1.0;
nicholas@2538:             if (G >= 3) {
nicholas@2538:                 G = 1.41;
nicholas@2538:             }
nicholas@2538:             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@2538: }