AnalyserNode.getFloatTimeDomainData()
The getFloatTimeDomainData()
method of the AnalyserNode
Interface copies the current waveform, or time-domain, data into a Float32Array
array passed into it.
Syntax
var audioCtx = new AudioContext();
var analyser = audioCtx.createAnalyser();
var dataArray = new Float32Array(analyser.fftSize); // Float32Array needs to be the same length as the fftSize
analyser.getFloatTimeDomainData(dataArray); // fill the Float32Array with data returned from getFloatTimeDomainData()
Parameters
array
-
The
Float32Array
that the time domain data will be copied to. If the array has fewer elements than theAnalyserNode.fftSize
, excess elements are dropped. If it has more elements than needed, excess elements are ignored.
Return value
None.
Example
The following example shows basic usage of an AudioContext
to create an AnalyserNode
, then requestAnimationFrame
and <canvas>
to collect time domain data repeatedly and draw an "oscilloscope style" output of the current audio input. For more complete applied examples/information, check out our Voice-change-O-matic-float-data demo (see the source code too).
var audioCtx = new (window.AudioContext || window.webkitAudioContext)();
var analyser = audioCtx.createAnalyser();
...
analyser.fftSize = 1024;
var bufferLength = analyser.fftSize;
console.log(bufferLength);
var dataArray = new Float32Array(bufferLength);
canvasCtx.clearRect(0, 0, WIDTH, HEIGHT);
function draw() {
drawVisual = requestAnimationFrame(draw);
analyser.getFloatTimeDomainData(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] * 200.0;
var y = HEIGHT/2 + v;
if(i === 0) {
canvasCtx.moveTo(x, y);
} else {
canvasCtx.lineTo(x, y);
}
x += sliceWidth;
}
canvasCtx.lineTo(canvas.width, canvas.height/2);
canvasCtx.stroke();
};
draw();
Specifications
Specification |
---|
Web Audio API # dom-analysernode-getfloattimedomaindata |
Browser compatibility
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