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---
title: AnalyserNode.getByteFrequencyData()
slug: Web/API/AnalyserNode/getByteFrequencyData
translation_of: Web/API/AnalyserNode/getByteFrequencyData
---
<p>{{ APIRef("Web Audio API") }}</p>
<div>
<p>{{ domxref("AnalyserNode") }}接口的<strong><code>getByteFrequencyData()</code></strong>方法将当前频率数据复制到传入的Uint8Array（无符号字节数组）中。</p>
<p>如果数组的长度小于 {{domxref("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.</p>
</div>
<h2 id="语法">语法</h2>
<pre class="brush: js">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
</pre>
<h3 id="返回值">返回值</h3>
<p>一个 {{domxref("Uint8Array")}}（无符号字节数组）.</p>
<h2 id="例子">例子</h2>
<p>下面的例子展示了 {{domxref("AudioContext")}} 创建一个 <code>AnalyserNode</code>, 然后用 {{domxref("window.requestAnimationFrame()","requestAnimationFrame")}} 和 {{htmlelement("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).</p>
<p>更多的例子/信息, 查看 <a href="https://mdn.github.io/voice-change-o-matic/">Voice-change-O-matic</a> 演示 (相关代码在 <a href="https://github.com/mdn/voice-change-o-matic/blob/gh-pages/scripts/app.js#L128-L205">app.js 的 128行~205行</a>).</p>
<pre class="brush: js">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();</pre>
<h2 id="参数">参数</h2>
<dl>
<dt>array (数组)</dt>
<dd>必须为{{domxref("Uint8Array")}}, 频域数据将复制到该数组内.</dd>
</dl>
<h2 id="规范">规范</h2>
<table class="standard-table">
<tbody>
<tr>
<th scope="col">Specification</th>
<th scope="col">Status</th>
<th scope="col">Comment</th>
</tr>
<tr>
<td>{{SpecName('Web Audio API', '#widl-AnalyserNode-getByteFrequencyData-void-Uint8Array-array', 'getByteFrequencyData()')}}</td>
<td>{{Spec2('Web Audio API')}}</td>
<td> </td>
</tr>
</tbody>
</table>
<h2 id="浏览器兼容性">浏览器兼容性</h2>
{{Compat("api.AnalyserNode.getByteFrequencyData")}}
<h2 id="相关内容">相关内容</h2>
<ul>
<li><a href="/en-US/docs/Web_Audio_API/Using_Web_Audio_API">Using the Web Audio API</a></li>
</ul>
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