[01天]HTML5 Audio音频频谱实现

心法 **01** 天

DEMO在线地址： [http://demo.ccued.com/HTML5\_Audio\_Spectrum/](http://demo.ccued.com/HTML5_Audio_Spectrum/ "http://demo.ccued.com/HTML5_Audio_Spectrum/")

完整的示例代码。代码不多，把音乐地址换一下，自己跑跑看吧

```html
<pre class="prism-highlight prism-language-markup"><!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>HTML5 Audio Spectrum</title>
  <style>
    .screen{
      height: 200px;
      width: 400px;
      box-shadow: 0 2px 5px rgba(0, 0, 0, 0.2);
      background-color: #000;
    }
    </style>
</head>
<body>
<div class="screen"></div>
<button onclick="play()">播放</button>
<script>
class AudioSpectrum{

// 显示频谱的DOM容器
  constructor(screenDom) {
    this.screenDom = screenDom
    this.interval = 0
    this.initRect()
    this.initContext()
  }

// 初始化画布
  initRect() {
    const { width, height } = this.screenDom.getBoundingClientRect()
    this.width = width
    this.height = height
    this.canvas = document.createElement('canvas')
    this.canvas.width = width
    this.canvas.height = height
    this.screenDom.appendChild(this.canvas)
    this.ctx = this.canvas.getContext('2d')
    this.ctx.fillStyle = '#00ff00'
  }

// 初始化音频分析器
  initContext() {
    this.context = new AudioContext()
    this.analyser = this.context.createAnalyser()
    this.analyser.fftSize = 1024
    this.source = this.context.createBufferSource()
    this.source.connect(this.analyser)
    this.analyser.connect(this.context.destination)
  }

// 播放HTTP音乐
  playHttpAudio(src) {
    if (this.source.buffer) {
      this.source.stop(0)
      this.initContext()
    }
    const request = new XMLHttpRequest()
    request.open('GET', src, true)
    request.responseType = 'arraybuffer'
    request.onload = () => {
      const data = request.response
      this.context.decodeAudioData(data, buffer => {
        this.source.buffer = buffer
        this.source.loop = true
        this.source.start(0)
        this.animate()
      })
    }
    request.send()
  }

// 画频谱
  render() {
    const length = this.analyser.frequencyBinCount*44100 / this.context.sampleRate|0
    const arrBuffer = new Uint8Array(length)
    this.analyser.getByteFrequencyData(arrBuffer)

const BAR_WIDTH = 10
    const BAR_SPACE = 2
    const BAR_COUNT = Math.floor((this.width + BAR_SPACE) / (BAR_WIDTH + BAR_SPACE))

this.ctx.clearRect(0, 0, this.width, this.height)
    for(let i = 0; i < BAR_COUNT; i++) {
      const index = Math.floor(arrBuffer.length / BAR_COUNT * i)
      const barHeight = arrBuffer[index] / 255 * this.height
      this.ctx.beginPath()
      this.ctx.rect(i * (BAR_WIDTH + BAR_SPACE), this.height - barHeight, BAR_WIDTH, barHeight)
      this.ctx.closePath()
      this.ctx.fill()
    }
  }

animate() {
    this.render()
    this.interval = requestAnimationFrame(() => {
      this.animate()
    })
  }

stop() {
    this.source.stop(0)
    cancelAnimationFrame(this.interval)
  }

}

const AS = new AudioSpectrum(document.querySelector('.screen'))
function play() {
  AS.playHttpAudio('./dgzc.mp3')
}
</script>
</body>
</html>
```

</body></html>

2022-05-17 16:33:17 694 0

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[01天]HTML5 Audio音频频谱实现

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