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microphone.js
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microphone.js
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(function() {
class MicrophoneSensor {
constructor() {
this._constraints = {
audio: true,
video: false
};
if (this.hasSensor()) {
this._audioContext = new (window.AudioContext || window.webkitAudioContext)();
}
}
hasSensor() {
return typeof window.AudioContext !== 'undefined' || typeof window.webkitAudioContext !== 'undefined';
}
async checkPermissions(fromButton) {
if (!this.hasSensor()) {
throw new Error('Microphone not present on this device');
}
if (this._recorder) {
return true;
}
if (!fromButton) {
return false;
}
if (this._audioContext?.state === "suspended") {
// Resume after user interaction
// https://developers.google.com/web/updates/2017/09/autoplay-policy-changes#webaudio
await this._audioContext.resume();
}
this._stream = await navigator.mediaDevices.getUserMedia(this._constraints);
return true;
}
takeSample(length, frequency, processing) {
return new Promise((resolve, reject) => {
if (!this._stream) {
return reject('No audio stream');
}
if (frequency !== 16000) {
return reject('Microphone only supports sampling at 16000Hz');
}
if (!this._audioContext) {
return reject('No audio context');
}
// use the stream
let input = this._audioContext.createMediaStreamSource(this._stream);
// Create the Recorder object and configure to record mono sound (1 channel)
// Recording 2 channels will double the file size
if (!this._recorder) {
this._recorder = new Recorder(input, {
numChannels: 1
});
this._recorder.record();
}
else {
this._recorder.clear();
}
setTimeout(() => {
if (!this._stream) return;
// tell the recorder to stop the recording
// this._stream.getAudioTracks()[0].stop();
processing();
if (!this._recorder) return;
// create the wav blob and pass it on to createDownloadLink
this._recorder.exportWAV(async (blob) => {
let buffer = await new Response(blob).arrayBuffer();
console.log('done recording', buffer.byteLength);
let wavFileItems = new Int16Array(buffer, 44);
let eiData = [];
for (let w of wavFileItems) {
eiData.push(w);
}
// this._stream = undefined;
resolve({
values: eiData.slice(0, length * 16),
intervalMs: 1000 / 16000,
sensors: [{
name: "audio",
units: "wav"
}
],
});
});
}, length + 50);
});
};
}
window.MicrophoneSensor = MicrophoneSensor;
})();