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 thanAudioContext.currentTime
, the change happens immediately. ATypeError
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
Specification |
---|
Web Audio API # dom-audioparam-setvalueattime |
Browser compatibility
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