AnalyserNode.fftSize

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句法
范例
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fftSize 特性为 AnalyserNode interface is an unsigned long value and represents the window size in samples that is used when performing a Fast Fourier Transform (FFT) to get frequency domain data.

句法

var curValue = analyserNode.fftSize;
analyserNode.fftSize = newValue;

值

An unsigned integer, representing the window size of the FFT, given in number of samples. A higher value will result in more details in the frequency domain but fewer details in the time domain.

Must be a power of 2 between $2^5$ and $2^15$ , so one of: 32 , 64 , 128 , 256 , 512 , 1024 , 2048 , 4096 , 8192 , 16384 ，和 32768 。默认为 2048 .

注意 : If its value is not a power of 2, or it is outside the specified range, a DOMException with the name IndexSizeError is thrown.

范例

The following example shows basic usage of an AudioContext to create an AnalyserNode ，那么 requestAnimationFrame and <canvas> to collect time domain data repeatedly and draw an "oscilloscope style" output of the current audio input. For more complete applied examples/information, check out our Voice-change-O-matic demo (see app.js lines 128–205 for relevant code).

var audioCtx = new (window.AudioContext || window.webkitAudioContext)();
var analyser = audioCtx.createAnalyser();
  ...
analyser.fftSize = 2048;
var bufferLength = analyser.frequencyBinCount ;
var dataArray = new Uint8Array(bufferLength);
analyser.getByteTimeDomainData(dataArray);
// draw an oscilloscope of the current audio source
function draw() {
      drawVisual = requestAnimationFrame(draw);
      analyser.getByteTimeDomainData(dataArray);
      canvasCtx.fillStyle = 'rgb(200, 200, 200)';
      canvasCtx.fillRect(0, 0, WIDTH, HEIGHT);
      canvasCtx.lineWidth = 2;
      canvasCtx.strokeStyle = 'rgb(0, 0, 0)';
      canvasCtx.beginPath();
      var sliceWidth = WIDTH * 1.0 / bufferLength;
      var x = 0;
      for(var i = 0; i < bufferLength; i++) {
        var v = dataArray[i] / 128.0;
        var y = v * HEIGHT/2;
        if(i === 0) {
          canvasCtx.moveTo(x, y);
        } else {
          canvasCtx.lineTo(x, y);
        }
        x += sliceWidth;
      }
      canvasCtx.lineTo(canvas.width, canvas.height/2);
      canvasCtx.stroke();
    };
    draw();

规范

规范	状态	注释
Web 音频 API The definition of 'fftSize' 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
`fftSize`	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

图例

完整支持
不支持

另请参阅

使用 Web 音频 API

元数据

最后修改： Aug 10, 2020

Web 音频 API
AnalyserNode
构造函数
1. AnalyserNode()
特性
1. fftSize
2. frequencyBinCount
3. maxDecibels
4. minDecibels
5. smoothingTimeConstant
方法
继承：
1. AudioNode
2. EventTarget
Related pages for Web Audio API

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句法

值

范例

规范

浏览器兼容性

图例

另请参阅

相关话题