126 lines
3.2 KiB
JavaScript
126 lines
3.2 KiB
JavaScript
/* global config */
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/**
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* Provides statistics for the local stream.
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*/
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var RTCBrowserType = require('../RTC/RTCBrowserType');
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/**
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* Size of the webaudio analyzer buffer.
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* @type {number}
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*/
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var WEBAUDIO_ANALYZER_FFT_SIZE = 2048;
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/**
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* Value of the webaudio analyzer smoothing time parameter.
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* @type {number}
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*/
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var WEBAUDIO_ANALYZER_SMOOTING_TIME = 0.8;
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/**
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* Converts time domain data array to audio level.
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* @param samples the time domain data array.
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* @returns {number} the audio level
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*/
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function timeDomainDataToAudioLevel(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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var value = 0;
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var diff = lastLevel - newLevel;
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if(diff > 0.2) {
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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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value = lastLevel + 0.4;
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}
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else {
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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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* <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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* @constructor
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*/
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function LocalStatsCollector(stream, interval, statisticsService, eventEmitter) {
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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.eventEmitter = eventEmitter;
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this.audioLevel = 0;
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this.statisticsService = statisticsService;
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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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LocalStatsCollector.prototype.start = function () {
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if (config.disableAudioLevels || !window.AudioContext ||
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RTCBrowserType.isTemasysPluginUsed())
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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_ANALYZER_SMOOTING_TIME;
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analyser.fftSize = WEBAUDIO_ANALYZER_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.eventEmitter.emit(
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"statistics.audioLevel",
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self.statisticsService.LOCAL_JID,
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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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LocalStatsCollector.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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module.exports = LocalStatsCollector; |