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() 

Parameters

array

The Float32Array that the frequency domain data will be copied to. For any sample which is silent, the value is -Infinity.

Return value

undefined.

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();

Specifications

Browser compatibility

See also

• Using the Web Audio API