前端基础（四十一）：实时获取麦克风音量
let _mediaStream = null;
let _scriptProcessor = null;
document.querySelector('#open').onclick = () => {
navigator.mediaDevices.getUserMedia({ audio: true })
.then(mediaStream => {
_mediaStream = mediaStream;
const audioContext = new AudioContext();
const mediaStreamSource = audioContext.createMediaStreamSource(_mediaStream);
const analyser = audioContext.createAnalyser();
_scriptProcessor = audioContext.createScriptProcessor(2048, 1, 1);
mediaStreamSource.connect(analyser);
analyser.connect(_scriptProcessor);
_scriptProcessor.connect(audioContext.destination);
_scriptProcessor.onaudioprocess = audioProcessingEvent => {
const uint8Array = new Uint8Array(analyser.frequencyBinCount);
analyser.getByteFrequencyData(uint8Array);
let volumeTotal = 0;
uint8Array.forEach(d => volumeTotal += d);
document.getElementById('range').value = volumeTotal / uint8Array.length;
}
});
}
document.querySelector('#close').onclick = () => {
const audioTracks = _mediaStream.getAudioTracks();
audioTracks.forEach(audioTrack => audioTrack.stop());
_scriptProcessor.disconnect();
document.querySelector('#range').value = 0;
}