jiti-meet/local_sts.js

131 lines
3.6 KiB
JavaScript

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