AnalyserNode.getByteFrequencyData()
The getByteFrequencyData()
method of the AnalyserNode
interface copies the current frequency data into a Uint8Array
(unsigned byte array) passed into it.
If the array has fewer elements than the AnalyserNode.frequencyBinCount
, excess elements are dropped. If it has more elements than needed, excess elements are ignored.
Syntax
var audioCtx = new AudioContext(); var analyser = audioCtx.createAnalyser(); var dataArray = new Uint8Array(analyser.frequencyBinCount); // Uint8Array should be the same length as the frequencyBinCount analyser.getByteFrequencyData(dataArray); // fill the Uint8Array with data returned from getByteFrequencyData()
Returns
A Uint8Array
.
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 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 = 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; 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 + 1; } }; draw();
Parameters
- array
- The
Uint8Array
that the frequency domain data will be copied to.
Specifications
Specification | Status | Comment |
---|---|---|
Web Audio API The definition of 'getByteFrequencyData()' in that specification. |
Working Draft |
Browser compatibility
Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari (WebKit) |
---|---|---|---|---|---|
Basic support | 10.0webkit | 25.0 (25.0) | No support | 15.0webkit 22 (unprefixed) |
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
License
© 2016 Mozilla Contributors
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-us/docs/web/api/analysernode/getbytefrequencydata