AudioContext.createAnalyser()
AudioContext
的createAnalyser()
方法能创建一个AnalyserNode
,可以用来获取音频时间和频率数据,以及实现数据可视化。
备注: 关于该节点的更多信息,请查看AnalyserNode
语法
js
var audioCtx = new AudioContext();
var analyser = audioCtx.createAnalyser();
返回值
例子
下面的例子展示了 AudioContext 创建分析器节点的基本用法,然后用 requestAnimationFrame() 来反复获取时域数据,并绘制出当前音频输入的“示波器风格”输出。更多完整例子请查看Voice-change-O-matic demo (中app.js 的 128–205 行代码)
js
var audioCtx = new (window.AudioContext || window.webkitAudioContext)();
var analyser = audioCtx.createAnalyser();
...
analyser.fftSize = 2048;
var bufferLength = analyser.fftSize;
var dataArray = new Uint8Array(bufferLength);
analyser.getByteTimeDomainData(dataArray);
// draw an oscilloscope of the current audio source
function draw() {
drawVisual = requestAnimationFrame(draw);
analyser.getByteTimeDomainData(dataArray);
canvasCtx.fillStyle = 'rgb(200, 200, 200)';
canvasCtx.fillRect(0, 0, WIDTH, HEIGHT);
canvasCtx.lineWidth = 2;
canvasCtx.strokeStyle = 'rgb(0, 0, 0)';
canvasCtx.beginPath();
var sliceWidth = WIDTH * 1.0 / bufferLength;
var x = 0;
for(var i = 0; i < bufferLength; i++) {
var v = dataArray[i] / 128.0;
var y = v * HEIGHT/2;
if(i === 0) {
canvasCtx.moveTo(x, y);
} else {
canvasCtx.lineTo(x, y);
}
x += sliceWidth;
}
canvasCtx.lineTo(canvas.width, canvas.height/2);
canvasCtx.stroke();
};
draw();
规范
Specification |
---|
Web Audio API # dom-baseaudiocontext-createanalyser |
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