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sound_meter.js
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sound_meter.js
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/*
* Copyright (c) 2015 The WebRTC project authors. All Rights Reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree.
*/
'use strict';
// Meter class that generates a number correlated to audio volume.
// The meter class itself displays nothing, but it makes the
// instantaneous and time-decaying volumes available for inspection.
// It also reports on the fraction of samples that were at or near
// the top of the measurement range.
function SoundMeter(context) {
this.context = context;
this.instant = 0.0;
this.slow = 0.0;
this.clip = 0.0;
this.script = context.createScriptProcessor(2048, 1, 1);
const that = this;
this.script.onaudioprocess = function(event) {
const input = event.inputBuffer.getChannelData(0);
let i;
let sum = 0.0;
let clipcount = 0;
for (i = 0; i < input.length; ++i) {
sum += input[i] * input[i];
if (Math.abs(input[i]) > 0.99) {
clipcount += 1;
}
}
that.instant = Math.sqrt(sum / input.length)*10;
that.slow = 0.95 * that.slow + 0.05 * that.instant*100;
that.clip = clipcount / input.length;
};
}
SoundMeter.prototype.connectToSource = function(stream, callback) {
console.log('SoundMeter connecting');
try {
this.mic = this.context.createMediaStreamSource(stream);
this.mic.connect(this.script);
// necessary to make sample run, but should not be.
this.script.connect(this.context.destination);
if (typeof callback !== 'undefined') {
callback(null);
}
} catch (e) {
console.error(e);
if (typeof callback !== 'undefined') {
callback(e);
}
}
};
SoundMeter.prototype.stop = function() {
console.log('SoundMeter stopping');
this.mic.disconnect();
this.script.disconnect();
};