Web/API/AnalyserNode/getFloatTimeDomainData

The getFloatTimeDomainData() method of the AnalyserNode Interface copies the current waveform, or time-domain, data into a Float32Array array passed into it.

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.

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 the AnalyserNode.frequencyBinCount, 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 [[../../../../../../../mdn.github.io/voice-change-o-matic-float-data/index|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();

 

Parameters

array

The Float32Array that the time domain data will be copied to.

Specifications

Specification	Status	Comment
Web Audio APIThe definition of 'getFloatTimeDomainData()' in that specification.	Working Draft

Browser compatibility

The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.

Update compatibility data on GitHub

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
getFloatTimeDomainData	Chrome Full support 14	Edge Full support 12	Firefox Full support 25	IE No support No	Opera Full support 15	Safari No support No	WebView Android Full support Yes	Chrome Android Full support 18	Firefox Android Full support 26	Opera Android Full support 14	Safari iOS No support No	Samsung Internet Android Full support 1.0

Legend

Full support  

Full support

No support  

No support

See also

• Using the Web Audio API

AnalyserNode.getFloatTimeDomainData() by Mozilla Contributors is licensed under CC-BY-SA 2.5.