The minDecibels
property of the AnalyserNode
interface Is a double value representing the minimum power value in the scaling range for the FFT analysis data, for conversion to unsigned byte/float values — basically, this specifies the minimum value for the range of results when using getFloatFrequencyData()
or getByteFrequencyData()
.
The minDecibels
property's default value is -100
.
Note: If a value greater than AnalyserNode.maxDecibels
is set, an INDEX_SIZE_ERR
exception is thrown.
var audioCtx = new AudioContext(); var analyser = audioCtx.createAnalyser(); analyser.minDecibels = -90;
A double.
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; 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();
Specification | Status | Comment |
---|---|---|
Web Audio API The definition of 'minDecibels' in that specification. | Working Draft |
Feature | Chrome | Edge | Firefox | Internet Explorer | Opera | Safari |
---|---|---|---|---|---|---|
Basic support | 14 | Yes | 25 | No | 15 | 6 |
Feature | Android webview | Chrome for Android | Edge mobile | Firefox for Android | IE mobile | Opera Android | iOS Safari |
---|---|---|---|---|---|---|---|
Basic support | Yes | 14 | Yes | 26 | No | 15 | ? |
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Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/API/AnalyserNode/minDecibels