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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

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.)

// 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

Specification
Web Audio API # dom-audioparam-setvalueattime

Browser compatibility