--- title: AnalyserNode.getByteFrequencyData() slug: Web/API/AnalyserNode/getByteFrequencyData translation_of: Web/API/AnalyserNode/getByteFrequencyData --- <p>{{ APIRef("Web Audio API") }}</p> <div> <p>{{ domxref("AnalyserNode") }} 介面的 <strong><code>getByteFrequencyData()</code></strong> 方法會將當前的頻率資料複製到 {{domxref("Uint8Array")}} (無號 byte 陣列)。</p> <p>如果陣列的元素數目比 {{domxref("AnalyserNode.frequencyBinCount")}} 少的話,多餘的元素會被 drop 掉。如果比需要的少的話,多餘的元素會被忽略。</p> </div> <h2 id="語法">語法</h2> <pre class="brush: js">var audioCtx = new AudioContext(); var analyser = audioCtx.createAnalyser(); var dataArray = new Uint8Array(analyser.frequencyBinCount); // Uint8Array 應該要和 frequencyBinCount 等長 analyser.getByteFrequencyData(dataArray); // 將 getByteFrequencyData() 回傳的資料放進 Uint8Array </pre> <h3 id="回傳值">回傳值</h3> <p>{{domxref("Uint8Array")}}。</p> <h2 id="範例">範例</h2> <p>下面的範例顯示出 {{domxref("AudioContext")}} 用於建立一個 <code>AnalyserNode</code> 的基本用法,然後 {{domxref("window.requestAnimationFrame()", "requestAnimationFrame")}} 以及 {{htmlelement("canvas")}} 用來重複收集當前聲音輸入的頻率資料並在 "winamp bargraph style" 畫出輸出。若要知道更完整的範例或是資訊,請參考 <a href="http://mdn.github.io/voice-change-o-matic/">Voice-change-O-matic</a> demo (看 <a href="https://github.com/mdn/voice-change-o-matic/blob/gh-pages/scripts/app.js#L128-L205">app.js 第 128–205 行</a> 會有相關的程式碼)。</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="參數">參數</h2> <dl> <dt>陣列</dt> <dd>頻率定義域會被複製進去的 {{domxref("Uint8Array")}} 。</dd> </dl> <h2 id="規範">規範</h2> <table class="standard-table" style="height: 105px; width: 593px;"> <tbody> <tr> <th scope="col">規範</th> <th scope="col">狀態</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="瀏覽器支援度">瀏覽器支援度</h2> {{Compat("api.AnalyserNode.getByteFrequencyData")}} <h2 id="參看">參看</h2> <ul> <li><a href="/en-US/docs/Web_Audio_API/Using_Web_Audio_API">使用 Web Audio API</a></li> </ul>