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AudioParam: setValueAtTime() method

The setValueAtTime() method of the AudioParam interface schedules an instant change to the AudioParam value at a precise time, as measured against AudioContext.currentTime. The new value is given in the value parameter.

Syntax

js

setValueAtTime(value, startTime)

Parameters

value

A floating point number representing the value the AudioParam will change to at the given time.

startTime

A double representing the time (in seconds) after the AudioContext was first created that the change in value will happen. If the time is less than AudioContext.currentTime, the change happens immediately. A TypeError is thrown if this value is negative.

Return value

A reference to this AudioParam object. In some browsers older implementations of this interface return undefined.

Examples

This simple example features a media element source with two control buttons (see our webaudio-examples repo for the source code, or view the example live). When the buttons are pressed, the currGain variable is incremented/decremented by 0.25, then the setValueAtTime() method is used to set the gain value equal to currGain, one second from now (audioCtx.currentTime + 1.)

js

// create audio context
const AudioContext = window.AudioContext || window.webkitAudioContext;
const audioCtx = new AudioContext();

// set basic variables for example
const myAudio = document.querySelector("audio");
const pre = document.querySelector("pre");
const myScript = document.querySelector("script");

pre.innerHTML = myScript.innerHTML;

const targetAtTimePlus = document.querySelector(".set-target-at-time-plus");
const targetAtTimeMinus = document.querySelector(".set-target-at-time-minus");

// Create a MediaElementAudioSourceNode
// Feed the HTMLMediaElement into it
const source = audioCtx.createMediaElementSource(myAudio);

// Create a gain node and set it's gain value to 0.5
const gainNode = audioCtx.createGain();
gainNode.gain.value = 0.5;
let currGain = gainNode.gain.value;

// connect the AudioBufferSourceNode to the gainNode
// and the gainNode to the destination
source.connect(gainNode);
gainNode.connect(audioCtx.destination);

// set buttons to do something onclick
targetAtTimePlus.onclick = () => {
  currGain += 0.25;
  gainNode.gain.setValueAtTime(currGain, audioCtx.currentTime + 1);
};

targetAtTimeMinus.onclick = () => {
  currGain -= 0.25;
  gainNode.gain.setValueAtTime(currGain, audioCtx.currentTime + 1);
};

Specifications

Browser compatibility

Desktop Mobile
Chrome Edge Firefox Internet Explorer Opera Safari WebView Android Chrome Android Firefox for Android Opera Android Safari on IOS Samsung Internet
setValueAtTime 14 12 25 No 15 6 ≤37 18 25 14 6 1.0

See also

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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/AudioParam/setValueAtTime