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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

getFloatTimeDomainData(array)

Parameters

array

The Float32Array that the time domain data will be copied to. If the array has fewer elements than the AnalyserNode.fftSize, excess elements are dropped. If it has more elements than needed, excess elements are ignored.

Return value

None.

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-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

Browser compatibility

Desktop Mobile
Chrome Edge Firefox Internet Explorer Opera Safari WebView Android Chrome Android Firefox for Android Opera Android Safari on IOS Samsung Internet
getFloatTimeDomainData
35
12
30
No
22
14.1
37
35
30
22
14.5
3.0

See also

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Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/API/AnalyserNode/getFloatTimeDomainData