AnalyserNode.getByteFrequencyData()

AnalyserNode接口的getByteFrequencyData()方法将当前频率数据复制到传入的Uint8Array(无符号字节数组)中。

如果数组的长度小于 AnalyserNode.frequencyBinCount, 那么Analyser多出的元素会被删除. 如果是大于, 那么数组多余的元素会被忽略.

语法

var audioCtx = new AudioContext();
var analyser = audioCtx.createAnalyser();
var dataArray = new Uint8Array(analyser.frequencyBinCount); // Uint8Array 的长度应该和 frequencyBinCount 相等
analyser.getByteFrequencyData(dataArray); // 调用 getByteFrequencyData 方法填充 Uint8Array

返回值

一个 Uint8Array (en-US)(无符号字节数组).

例子

下面的例子展示了 AudioContext 创建一个 AnalyserNode, 然后用 requestAnimationFrame<canvas> 去反复收集当前音频的频率数据, 并绘制为一个柱状风格的输出(频谱).

更多的例子/信息, 查看 Voice-change-O-matic 演示 (相关代码在 app.js 的 128行~205行).

var audioCtx = new (window.AudioContext || window.webkitAudioContext)();
var analyser = audioCtx.createAnalyser();

  ...

analyser.fftSize = 256;
var bufferLength = analyser.frequencyBinCount;
console.log(bufferLength);
var dataArray = new Uint8Array(bufferLength);

canvasCtx.clearRect(0, 0, WIDTH, HEIGHT);

function draw() {
  drawVisual = requestAnimationFrame(draw);

  analyser.getByteFrequencyData(dataArray);

  canvasCtx.fillStyle = 'rgb(0, 0, 0)';
  canvasCtx.fillRect(0, 0, WIDTH, HEIGHT);

  var barWidth = (WIDTH / bufferLength) * 2.5;
  var barHeight;
  var x = 0;

  for(var i = 0; i < bufferLength; i++) {
    barHeight = dataArray[i];

    canvasCtx.fillStyle = 'rgb(' + (barHeight+100) + ',50,50)';
    canvasCtx.fillRect(x,HEIGHT-barHeight/2,barWidth,barHeight/2);

    x += barWidth + 1;
  }
};

draw();

参数

array (数组)
必须为Uint8Array (en-US), 频域数据将复制到该数组内.

规范

Specification Status Comment
Web Audio API
getByteFrequencyData()
Recommendation  

浏览器兼容性

We're converting our compatibility data into a machine-readable JSON format. This compatibility table still uses the old format, because we haven't yet converted the data it contains. Find out how you can help! (en-US)
Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support 10.0webkit (en-US) 25.0 (25.0)  未实现 15.0webkit (en-US)
22 (unprefixed)
6.0webkit (en-US)
Feature Android Firefox Mobile (Gecko) Firefox OS IE Mobile Opera Mobile Safari Mobile Chrome for Android
Basic support ? 26.0 1.2 ? ? ? 33.0

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