# 麦克风
主要使用：
- navigator.mediaDevices.getUserMedia
- AudioContext
- createMediaStreamSource
- createScriptProcessor
# 效果
# 代码
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>麦克风</title>
<style>
#box {
height: 100px;
display: flex;
align-items: center;
background-color: #efefef;
}
#box>span {
/* flex: 1; */
width: 10px;
min-height: 1px;
border-radius: 2px;
background-color: #000000;
}
</style>
</head>
<!-- https://dev.eztest.org/monitor/session/3458/#/ -->
<body>
<h2>麦克风 声波曲线</h2>
<button onclick="detectDevice()">授权 & 采集</button>
<button onclick="closeMicro()">关闭</button>
<br>
<br>
<!-- <canvas id="oscilloscope" style="width: 600px; height: 200px;"></canvas> -->
<div id="box"></div>
<script>
let logIng = false;
const box = document.getElementById('box');
// let audioContext = new (window.AudioContext || window.webkitAudioContext)();
let audioContext = null;
let mediaStreamSource = null;
let scriptProcessor = null;
// console.log(audioContext);
function detectDevice() {
audioContext = new AudioContext();
if (navigator.mediaDevices && navigator.mediaDevices.getUserMedia) {
// 获取用户的 media 信息
navigator.mediaDevices.getUserMedia({ audio: true })
.then((stream) => {
console.log(stream);
// 将麦克风的声音输入这个对象
mediaStreamSource = audioContext.createMediaStreamSource(stream);
// 创建一个音频分析对象，采样的缓冲区大小为4096，输入和输出都是单声道
scriptProcessor = audioContext.createScriptProcessor(2048,1,1); // 0, 256, 512, 1024, 2048, 4069, 8192, 16384
// 将该分析对象与麦克风音频进行连接
mediaStreamSource.connect(scriptProcessor);
// 此举无甚效果，仅仅是因为解决 Chrome 自身的 bug
scriptProcessor.connect(audioContext.destination);
console.log(scriptProcessor);
logIng = true;
// 开始处理音频
scriptProcessor.onaudioprocess = function(e) {
// 获得缓冲区的输入音频，转换为包含了PCM通道数据的32位浮点数组
let buffer = e.inputBuffer.getChannelData(0);
// 获取缓冲区中最大的音量值
let maxVal = Math.max.apply(Math, buffer);
// console.log(e, buffer, maxVal);
const height = Math.round(maxVal*100);
// console.log(logIng, height);
if(logIng) {
const span = document.createElement('span');
// console.log(height);
span.style.height = `${height}px`;
box.appendChild(span)
}
};
})
.catch((err) => {
const tip = '麦克风授权失败！';
alert(tip);
throw Error(tip);
});
} else {
alert('麦克风已禁用，或浏览器不支持此功能，请到浏览器设置中查看。');
throw Error('浏览器不支持此功能！');
}
}
function closeMicro() {
// console.log('close =>>>>');
if(audioContext!== null) {
audioContext.close()
.then(() => {
console.log('close =>>>>');
logIng = false;
mediaStreamSource.disconnect();
scriptProcessor.disconnect();
audioContext = null;
});
}
}
</script>
</body>
</html>
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