131 lines
3.6 KiB
JavaScript
131 lines
3.6 KiB
JavaScript
/**
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* Provides statistics for the local stream.
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*/
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var LocalStatsCollector = (function() {
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/**
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* Size of the webaudio analizer buffer.
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* @type {number}
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*/
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var WEBAUDIO_ANALIZER_FFT_SIZE = 2048;
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/**
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* Value of the webaudio analizer smoothing time parameter.
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* @type {number}
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*/
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var WEBAUDIO_ANALIZER_SMOOTING_TIME = 0.8;
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/**
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* <tt>LocalStatsCollector</tt> calculates statistics for the local stream.
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*
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* @param stream the local stream
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* @param interval stats refresh interval given in ms.
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* @param {function(LocalStatsCollector)} updateCallback the callback called on stats
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* update.
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* @constructor
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*/
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function LocalStatsCollectorProto(stream, interval, updateCallback) {
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window.AudioContext = window.AudioContext || window.webkitAudioContext;
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this.stream = stream;
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this.intervalId = null;
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this.intervalMilis = interval;
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this.updateCallback = updateCallback;
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this.audioLevel = 0;
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}
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/**
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* Starts the collecting the statistics.
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*/
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LocalStatsCollectorProto.prototype.start = function () {
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if (!window.AudioContext)
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return;
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var context = new AudioContext();
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var analyser = context.createAnalyser();
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analyser.smoothingTimeConstant = WEBAUDIO_ANALIZER_SMOOTING_TIME;
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analyser.fftSize = WEBAUDIO_ANALIZER_FFT_SIZE;
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var source = context.createMediaStreamSource(this.stream);
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source.connect(analyser);
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var self = this;
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this.intervalId = setInterval(
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function () {
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var array = new Uint8Array(analyser.frequencyBinCount);
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analyser.getByteTimeDomainData(array);
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var audioLevel = TimeDomainDataToAudioLevel(array);
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if(audioLevel != self.audioLevel) {
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self.audioLevel = animateLevel(audioLevel, self.audioLevel);
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self.updateCallback(LocalStatsCollectorProto.LOCAL_JID, self.audioLevel);
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}
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},
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this.intervalMilis
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);
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};
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/**
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* Stops collecting the statistics.
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*/
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LocalStatsCollectorProto.prototype.stop = function () {
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if (this.intervalId) {
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clearInterval(this.intervalId);
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this.intervalId = null;
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}
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};
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/**
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* Converts time domain data array to audio level.
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* @param array the time domain data array.
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* @returns {number} the audio level
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*/
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var TimeDomainDataToAudioLevel = function (samples) {
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var maxVolume = 0;
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var length = samples.length;
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for (var i = 0; i < length; i++) {
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if (maxVolume < samples[i])
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maxVolume = samples[i];
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}
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return parseFloat(((maxVolume - 127) / 128).toFixed(3));
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};
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/**
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* Animates audio level change
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* @param newLevel the new audio level
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* @param lastLevel the last audio level
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* @returns {Number} the audio level to be set
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*/
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function animateLevel(newLevel, lastLevel)
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{
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var value = 0;
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var diff = lastLevel - newLevel;
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if(diff > 0.2)
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{
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value = lastLevel - 0.2;
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}
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else if(diff < -0.4)
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{
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value = lastLevel + 0.4;
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}
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else
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{
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value = newLevel;
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}
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return parseFloat(value.toFixed(3));
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}
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/**
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* Indicates that this audio level is for local jid.
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* @type {string}
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*/
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LocalStatsCollectorProto.LOCAL_JID = 'local';
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return LocalStatsCollectorProto;
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})(); |