The frequencyBinCount
read-only property of the AnalyserNode
interface is an unsigned integer half that of the AnalyserNode.fftSize
. This generally equates to the number of data values you will have to play with for the visualization.
Syntax
var arrayLength = analyserNode.frequencyBinCount;
Value
An unsigned integer, equal to the number of values that AnalyserNode.getByteFrequencyData()
and AnalyserNode.getFloatFrequencyData()
copy into the provided TypedArray
.
For technical reasons related to how the Fast Fourier transform is defined, it is always half the value of AnalyserNode.fftSize
. Therefore, it will be one of 16
, 32
, 64
, 128
, 256
, 512
, 1024
, 2048
, 4096
, 8192
, and 16384
.
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 demo (see app.js lines 128–205 for relevant code).
var audioCtx = new (window.AudioContext || window.webkitAudioContext)(); var analyser = audioCtx.createAnalyser(); analyser.minDecibels = -90; analyser.maxDecibels = -10; ... analyser.fftSize = 256; var bufferLength = analyser.frequencyBinCount; console.log(bufferLength); var dataArray = new Uint8Array(bufferLength); canvasCtx.clearRect(0, 0, WIDTH, HEIGHT); function draw() { drawVisual = requestAnimationFrame(draw); analyser.getByteFrequencyData(dataArray); canvasCtx.fillStyle = 'rgb(0, 0, 0)'; canvasCtx.fillRect(0, 0, WIDTH, HEIGHT); var barWidth = (WIDTH / bufferLength) * 2.5 - 1; var barHeight; var x = 0; for(var i = 0; i < bufferLength; i++) { barHeight = dataArray[i]; canvasCtx.fillStyle = 'rgb(' + (barHeight+100) + ',50,50)'; canvasCtx.fillRect(x,HEIGHT-barHeight/2,barWidth,barHeight/2); x += barWidth; } }; draw();
Specifications
Specification | Status | Comment |
---|---|---|
Web Audio API The definition of 'frequencyBinCount' in that specification. |
Working Draft |
Browser compatibility
Desktop | Mobile | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
frequencyBinCount | Chrome Full support 14 | Edge Full support 12 | Firefox Full support 25 | IE No support No | Opera Full support 15 | Safari Full support 6 | WebView Android Full support Yes | Chrome Android Full support 18 | Firefox Android Full support 26 | Opera Android Full support 14 | Safari iOS Full support 6 | Samsung Internet Android Full support 1.0 |
Legend
- Full support
- Full support
- No support
- No support