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.
getByteTimeDomainData(array)
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).
const audioCtx = new (window.AudioContext || window.webkitAudioContext)();
const analyser = audioCtx.createAnalyser();
...
analyser.fftSize = 2048;
const bufferLength = analyser.fftSize;
const dataArray = new Uint8Array(bufferLength);
analyser.getByteTimeDomainData(dataArray);
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)';
const sliceWidth = WIDTH * 1.0 / bufferLength;
let x = 0;
canvasCtx.beginPath();
for(var i = 0; i < bufferLength; i++) {
const v = dataArray[i]/128.0;
const y = v * HEIGHT/2;
if(i === 0)
canvasCtx.moveTo(x, y);
else
canvasCtx.lineTo(x, y);
x += sliceWidth;
}
canvasCtx.lineTo(WIDTH, HEIGHT/2);
canvasCtx.stroke();
};
draw();