AnalyserNode: getFloatTimeDomainData() method
The getFloatTimeDomainData()
method of the AnalyserNode
Interface copies the current waveform, or time-domain, data into a Float32Array
array passed into it. Each array value is a sample, the magnitude of the signal at a particular time.
Syntax
getFloatTimeDomainData(array)
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 (undefined
).
Examples
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 demo (see app.js lines 108–193 for relevant code).
const audioCtx = new (window.AudioContext || window.webkitAudioContext)();
const analyser = audioCtx.createAnalyser();
// …
analyser.fftSize = 1024;
const bufferLength = analyser.fftSize;
console.log(bufferLength);
const 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();
const sliceWidth = (WIDTH * 1.0) / bufferLength;
let x = 0;
for (let i = 0; i < bufferLength; i++) {
const v = dataArray[i] * 200.0;
const 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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