AudioContext.createAnalyser()

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

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

Syntax

var audioCtx = new AudioContext();
var analyser = audioCtx.createAnalyser();

Returns

An AnalyserNode.

Example

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 128–205 for relevant code).

var audioCtx = new (window.AudioContext || window.webkitAudioContext)();
var analyser = audioCtx.createAnalyser();

  ...

analyser.fftSize = 2048;
var bufferLength = analyser.fftSize;
var 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();

      var sliceWidth = WIDTH * 1.0 / bufferLength;
      var x = 0;

      for(var i = 0; i < bufferLength; i++) {
   
        var v = dataArray[i] / 128.0;
        var 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

Specification Status Comment
Web Audio API
Die Definition von 'createAnalyser()' in dieser Spezifikation.
Arbeitsentwurf  

Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support 10.0webkit 25.0 (25.0)  Nicht unterstützt 15.0webkit
22
6.0webkit
Feature Android Firefox Mobile (Gecko) Firefox OS IE Mobile Opera Mobile Safari Mobile Chrome for Android
Basic support ? 26.0 1.2 ? ? ? 33.0

See also

Schlagwörter des Dokuments und Mitwirkende

 Mitwirkende an dieser Seite: meldron
 Zuletzt aktualisiert von: meldron,