AnalyserNode: maxDecibels property
Baseline Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since April 2021.
The maxDecibels
property of the AnalyserNode
interface is a double value representing the maximum power value in the scaling range for the FFT analysis data, for conversion to unsigned byte values — basically, this specifies the maximum value for the range of results when using getByteFrequencyData()
.
Value
A double, representing the maximum decibel value for scaling the FFT analysis data, where 0
dB is the loudest possible sound, -10
dB is a 10th of that, etc. The default value is -30
dB.
When getting data from getByteFrequencyData()
, any frequencies with an amplitude of maxDecibels
or higher will be returned as 255
.
Exceptions
IndexSizeError
DOMException
-
Thrown if a value less than or equal to
AnalyserNode.minDecibels
is set.
Examples
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 bar graph 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 108–193 for relevant code).
const audioCtx = new AudioContext();
const analyser = audioCtx.createAnalyser();
analyser.minDecibels = -90;
analyser.maxDecibels = -10;
// …
analyser.fftSize = 256;
const bufferLength = analyser.frequencyBinCount;
console.log(bufferLength);
const 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);
const barWidth = (WIDTH / bufferLength) * 2.5;
let barHeight;
let x = 0;
for (let 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();
Specifications
Specification |
---|
Web Audio API # dom-analysernode-maxdecibels |
Browser compatibility
BCD tables only load in the browser