The getByteTimeDomainData()
method of the AnalyserNode
Interface copies the current waveform, or time-domain, data into a Uint8Array
(unsigned byte array) passed into it.
If the array has fewer elements than the AnalyserNode.fftSize
, 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.fftSize); // Uint8Array should be the same length as the fftSize analyser.getByteTimeDomainData(dataArray); // fill the Uint8Array with data returned from getByteTimeDomainData()
Returns
A Uint8Array
.
Example
The following example shows basic usage of an AudioContext
to create an AnalyserNode
, then requestAnimationFrame
and <canvas>
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.frequencyBinCount; 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();
Parameters
- array
- The
Uint8Array
that the time domain data will be copied to.
Specifications
Specification | Status | Comment |
---|---|---|
Web Audio API The definition of 'getByteTimeDomainData()' 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 |