AnalyserNode.getFloatFrequencyData()

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范例
规范
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getFloatFrequencyData() 方法在 AnalyserNode Interface copies the current frequency data into a Float32Array array passed into it.

Each item in the array represents the decibel value for a specific frequency. The frequencies are spread linearly from 0 to 1/2 of the sample rate. For example, for 48000 sample rate, the last item of the array will represent the decibel value for 24000 Hz.

If you need higher performance and don't care about precision, you can use AnalyserNode.getByteFrequencyData() instead, which works on a Uint8Array .

句法

var audioCtx = new AudioContext();
var analyser = audioCtx.createAnalyser();
var dataArray = new Float32Array(analyser.frequencyBinCount); // Float32Array should be the same length as the frequencyBinCount
void analyser.getFloatFrequencyData(dataArray); // fill the Float32Array with data returned from getFloatFrequencyData()

参数

array: Float32Array that the frequency domain data will be copied to. For any sample which is silent, the value is - Infinity .
If the array has fewer elements than the AnalyserNode.frequencyBinCount , excess elements are dropped. If it has more elements than needed, excess elements are ignored.

返回值

None.

范例

const audioCtx = new AudioContext();
const analyser = audioCtx.createAnalyser();
// Float32Array should be the same length as the frequencyBinCount
const myDataArray = new Float32Array(analyser.frequencyBinCount);
// fill the Float32Array with data returned from getFloatFrequencyData()
analyser.getFloatFrequencyData(myDataArray);

Drawing a spectrum

The following example shows basic usage of an AudioContext to connect a MediaElementAudioSourceNode to an AnalyserNode . While the audio is playing, we collect the frequency data repeatedly with requestAnimationFrame() and draw a "winamp bargraph style" to a <canvas> 元素。

For more complete applied examples/information, check out our Voice-change-O-matic-float-data demo (see the 源代码 too).

<!doctype html>
<body>
<script>
const audioCtx = new AudioContext();
//Create audio source
//Here, we use an audio file, but this could also be e.g. microphone input
const audioEle = new Audio();
audioEle.src = 'my-audio.mp3';//insert file name here
audioEle.autoplay = true;
audioEle.preload = 'auto';
const audioSourceNode = audioCtx.createMediaElementSource(audioEle);
//Create analyser node
const analyserNode = audioCtx.createAnalyser();
analyserNode.fftSize = 256;
const bufferLength = analyserNode.frequencyBinCount;
const dataArray = new Float32Array(bufferLength);
//Set up audio node network
audioSourceNode.connect(analyserNode);
analyserNode.connect(audioCtx.destination);
//Create 2D canvas
const canvas = document.createElement('canvas');
canvas.style.position = 'absolute';
canvas.style.top = 0;
canvas.style.left = 0;
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
document.body.appendChild(canvas);
const canvasCtx = canvas.getContext('2d');
canvasCtx.clearRect(0, 0, canvas.width, canvas.height);
function draw() {
  //Schedule next redraw
  requestAnimationFrame(draw);
  //Get spectrum data
  analyserNode.getFloatFrequencyData(dataArray);
  //Draw black background
  canvasCtx.fillStyle = 'rgb(0, 0, 0)';
  canvasCtx.fillRect(0, 0, canvas.width, canvas.height);
  //Draw spectrum
  const barWidth = (canvas.width / bufferLength) * 2.5;
  let posX = 0;
  for (let i = 0; i < bufferLength; i++) {
    const barHeight = (dataArray[i] + 140) * 2;
    canvasCtx.fillStyle = 'rgb(' + Math.floor(barHeight + 100) + ', 50, 50)';
    canvasCtx.fillRect(posX, canvas.height - barHeight / 2, barWidth, barHeight / 2);
    posX += barWidth + 1;
  }
};
draw();
</script>
</body>

规范

规范	状态	注释
Web 音频 API The definition of 'getFloatFrequencyData()' in that specification.	工作草案

浏览器兼容性

The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request. 更新 GitHub 上的兼容性数据

	桌面						移动
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`getFloatFrequencyData`	Chrome 14	Edge 12	Firefox 25	IE 不支持 No	Opera 15	Safari 6	WebView Android Yes	Chrome Android 18	Firefox Android 26	Opera Android 14	Safari iOS 6	Samsung Internet Android 1.0

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完整支持
不支持

另请参阅

使用 Web 音频 API

元数据

最后修改： Feb 23, 2020

Web 音频 API
AnalyserNode
构造函数
1. AnalyserNode()
特性
方法
1. getByteFrequencyData()
2. getByteTimeDomainData()
3. getFloatFrequencyData()
4. getFloatTimeDomainData()
继承：
1. AudioNode
2. EventTarget
Related pages for Web Audio API

在此页

句法

参数

返回值

范例

Drawing a spectrum

规范

浏览器兼容性

图例

另请参阅

相关话题