AnalyserNode.smoothingTimeConstant

在此页

句法
范例
规范
浏览器兼容性
另请参阅
相关话题

smoothingTimeConstant 特性为 AnalyserNode interface is a double value representing the averaging constant with the last analysis frame. It's basically an average between the current buffer and the last buffer the AnalyserNode processed, and results in a much smoother set of value changes over time.

句法

var smoothValue = analyserNode.smoothingTimeConstant;
analyserNode.smoothingTimeConstant = newValue;

值

A double within the range 0 to 1 ( 0 meaning no time averaging). The default value is 0.8 .

If 0 is set, there is no averaging done, whereas a value of 1 means "overlap the previous and current buffer quite a lot while computing the value", which essentially smoothes the changes across AnalyserNode.getFloatFrequencyData / AnalyserNode.getByteFrequencyData 调用。

In technical terms, we apply a Blackman window and smooth the values over time. The default value is good enough for most cases.

注意 : If a value outside the range 0–1 is set, an INDEX_SIZE_ERR exception is thrown.

范例

The following example shows basic usage of an AudioContext to create an AnalyserNode ，那么 requestAnimationFrame and <canvas> to collect frequency data repeatedly and draw a "winamp bargraph 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).

If you are curious about the effect the smoothingTimeConstant() has, try cloning the above example and setting analyser.smoothingTimeConstant = 0; instead. You'll notice that the value changes are much more jarring.

var audioCtx = new (window.AudioContext || window.webkitAudioContext)();
var analyser = audioCtx.createAnalyser();
analyser.minDecibels = -90;
analyser.maxDecibels = -10;
analyser.smoothingTimeConstant = 0.85;
  ...
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();

规范

规范	状态	注释
Web 音频 API The definition of 'smoothingTimeConstant' 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
`smoothingTimeConstant`	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： 2020 年 1 月 22 日

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

在此页

句法

值

范例

规范

浏览器兼容性

图例

另请参阅

相关话题