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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

js

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 (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).

js

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

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

© 2005–2023 MDN contributors.
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/API/AnalyserNode/getFloatTimeDomainData