130 lines
3.7 KiB
JavaScript
130 lines
3.7 KiB
JavaScript
'use strict';
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// From https://github.com/johni0702/voice-activity-detection
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var analyserFrequency = require('analyser-frequency-average');
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module.exports = function(audioContext, stream, opts) {
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opts = opts || {};
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var defaults = {
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fftSize: 1024,
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bufferLen: 1024,
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smoothingTimeConstant: 0.2,
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minCaptureFreq: 85, // in Hz
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maxCaptureFreq: 255, // in Hz
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noiseCaptureDuration: 1000, // in ms
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minNoiseLevel: 0.3, // from 0 to 1
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maxNoiseLevel: 0.7, // from 0 to 1
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avgNoiseMultiplier: 1.2,
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onVoiceStart: function() {
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},
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onVoiceStop: function() {
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},
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onUpdate: function(val) {
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}
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};
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var options = {};
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for (var key in defaults) {
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options[key] = opts.hasOwnProperty(key) ? opts[key] : defaults[key];
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}
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var baseLevel = 0;
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var voiceScale = 1;
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var activityCounter = 0;
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var activityCounterMin = 0;
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var activityCounterMax = 60;
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var activityCounterThresh = 5;
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var envFreqRange = [];
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var isNoiseCapturing = true;
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var prevVadState = undefined;
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var vadState = false;
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var captureTimeout = null;
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var source = audioContext.createMediaStreamSource(stream);
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var analyser = audioContext.createAnalyser();
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analyser.smoothingTimeConstant = options.smoothingTimeConstant;
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analyser.fftSize = options.fftSize;
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var scriptProcessorNode = audioContext.createScriptProcessor(options.bufferLen, 1, 1);
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connect();
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scriptProcessorNode.onaudioprocess = monitor;
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if (isNoiseCapturing) {
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//console.log('VAD: start noise capturing');
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captureTimeout = setTimeout(init, options.noiseCaptureDuration);
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}
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function init() {
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//console.log('VAD: stop noise capturing');
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isNoiseCapturing = false;
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envFreqRange = envFreqRange.filter(function(val) {
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return val;
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}).sort();
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var averageEnvFreq = envFreqRange.length ? envFreqRange.reduce(function (p, c) { return Math.min(p, c) }, 1) : (options.minNoiseLevel || 0.1);
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baseLevel = averageEnvFreq * options.avgNoiseMultiplier;
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if (options.minNoiseLevel && baseLevel < options.minNoiseLevel) baseLevel = options.minNoiseLevel;
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if (options.maxNoiseLevel && baseLevel > options.maxNoiseLevel) baseLevel = options.maxNoiseLevel;
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voiceScale = 1 - baseLevel;
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//console.log('VAD: base level:', baseLevel);
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}
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function connect() {
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source.connect(analyser);
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analyser.connect(scriptProcessorNode);
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scriptProcessorNode.connect(audioContext.destination);
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}
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function disconnect() {
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scriptProcessorNode.disconnect();
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}
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function destroy() {
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captureTimeout && clearTimeout(captureTimeout);
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disconnect();
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analyser.disconnect();
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source.disconnect();
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source.mediaStream.getTracks().forEach(track => track.stop());
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}
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function monitor() {
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var frequencies = new Uint8Array(analyser.frequencyBinCount);
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analyser.getByteFrequencyData(frequencies);
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var average = analyserFrequency(analyser, frequencies, options.minCaptureFreq, options.maxCaptureFreq);
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if (isNoiseCapturing) {
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envFreqRange.push(average);
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return;
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}
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if (average >= baseLevel && activityCounter < activityCounterMax) {
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activityCounter++;
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} else if (average < baseLevel && activityCounter > activityCounterMin) {
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activityCounter--;
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}
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vadState = activityCounter > activityCounterThresh;
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if (prevVadState !== vadState) {
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vadState ? onVoiceStart() : onVoiceStop();
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prevVadState = vadState;
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}
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options.onUpdate(Math.max(0, average - baseLevel) / voiceScale);
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}
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function onVoiceStart() {
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options.onVoiceStart();
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}
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function onVoiceStop() {
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options.onVoiceStop();
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}
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return {connect: connect, disconnect: disconnect, destroy: destroy};
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};
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