AnalyserNode.maxDecibels

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句法
范例
规范
浏览器兼容性
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maxDecibels 特性为 AnalyserNode interface is a double value representing the maximum power value in the scaling range for the FFT analysis data, for conversion to unsigned byte/float values — basically, this specifies the maximum value for the range of results when using getFloatFrequencyData() or getByteFrequencyData() .

句法

var curValue = analyserNode.maxDecibels;
analyserNode.maxDecibels = newValue;

值

A double, representing the maximum decibel value for scaling the FFT analysis data, where 0 dB is the loudest possible sound, -10 dB is a 10th of that, etc. The default value is -30 dB.

When getting data from getFloatFrequencyData() or getByteFrequencyData() , any frequencies with an amplitude of maxDecibels or higher will be returned as +1.0 or 255 ，分别。

注意 : If a value less than or equal to AnalyserNode.minDecibels is set, an IndexSizeError 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).

var audioCtx = new (window.AudioContext || window.webkitAudioContext)();
var analyser = audioCtx.createAnalyser();
analyser.minDecibels = -90;
analyser.maxDecibels = -10;
  ...
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 'maxDecibels' 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
`maxDecibels`	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： Mar 29, 2019

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