AnalyserNode.getFloatFrequencyData

Syntax

var audioCtx = new AudioContext();
var analyser = audioCtx.createAnalyser();
var myDataArray = new Float32Array(analyser.frequencyBinCount); // Float32Array should be the same length as the frequencyBinCount 
analyser.getFloatFrequencyData(myDataArray); // fill the Float32Array with data returned from getFloatFrequencyData() 

Returns

A Float32Array.

Example

The following example shows basic usage of an AudioContext to create an AnalyserNode, then requestAnimationFrame and <canvas> to collect frequency data repeatedly and draw a "winamp bargraph 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 = 256;
var bufferLength = analyser.frequencyBinCount;
console.log(bufferLength);
var dataArray = new Float32Array(bufferLength);

canvasCtx.clearRect(0, 0, WIDTH, HEIGHT);

function draw() {
  drawVisual = requestAnimationFrame(draw);
  analyser.getFloatFrequencyData(dataArray);
  canvasCtx.fillStyle = 'rgb(0, 0, 0)';
  canvasCtx.fillRect(0, 0, WIDTH, HEIGHT);
  
  var barWidth = (WIDTH / bufferLength) * 2.5;
  var barHeight;
  var x = 0;

  for(var i = 0; i < bufferLength; i++) {
    barHeight = (dataArray[i] + 140)*2;
    canvasCtx.fillStyle = 'rgb(' + Math.floor(barHeight+100) + ',50,50)';
    canvasCtx.fillRect(x,HEIGHT-barHeight/2,barWidth,barHeight/2);
    x += barWidth + 1;
  }
};

draw();

Parameters

array

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

Specifications

Specification	Status	Comment
Web Audio API The definition of 'getFloatFrequencyData()' in that specification.	Working Draft

Browser compatibility

See also

• Using the Web Audio API