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BaseAudioContext: createAnalyser() method

The createAnalyser() method of the BaseAudioContext interface creates an AnalyserNode, which can be used to expose audio time and frequency data and create data visualizations.

Note: The AnalyserNode() constructor is the recommended way to create an AnalyserNode; see Creating an AudioNode.

Note: For more on using this node, see the AnalyserNode page.

Syntax

js

createAnalyser()

Parameters

None.

Return value

Examples

The following example shows basic usage of an AudioContext to create an Analyser node, then use requestAnimationFrame() 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 = 2048;
const bufferLength = analyser.frequencyBinCount;
const dataArray = new Uint8Array(bufferLength);
analyser.getByteTimeDomainData(dataArray);

// draw an oscilloscope of the current audio source

function draw() {
  drawVisual = requestAnimationFrame(draw);

  analyser.getByteTimeDomainData(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] / 128.0;
    const y = (v * HEIGHT) / 2;

    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
createAnalyser 14 12 25 No 15 6 4.4.3 18 25 14 6 1.0

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/BaseAudioContext/createAnalyser