AnalyserNode
介面的 getByteFrequencyData()
方法會將當前的頻率資料複製到 Uint8Array
(無號 byte 陣列)。
如果陣列的元素數目比 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。
語法
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
回傳值
範例
下面的範例顯示出 AudioContext
用於建立一個 AnalyserNode
的基本用法,然後 requestAnimationFrame
以及 <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 Voice-change-O-matic demo (看 app.js 第 128–205 行 會有相關的程式碼)。
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();
參數
- 陣列
- 頻率定義域會被複製進去的
Uint8Array
。
規範
規範 | 狀態 | Comment |
---|---|---|
Web Audio API The definition of 'getByteFrequencyData()' in that specification. |
Working Draft |
瀏覽器支援度
We're converting our compatibility data into a machine-readable JSON format.
This compatibility table still uses the old format,
because we haven't yet converted the data it contains.
Find out how you can help!
Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari (WebKit) |
---|---|---|---|---|---|
Basic support | 10.0webkit | 25.0 (25.0) | No support | 15.0webkit 22 (unprefixed) |
6.0webkit |
Feature | Android | Firefox Mobile (Gecko) | Firefox OS | IE Mobile | Opera Mobile | Safari Mobile | Chrome for Android |
---|---|---|---|---|---|---|---|
Basic support | ? | 26.0 | 1.2 | ? | ? | ? | 33.0 |