AudioParam: setValueAtTime() method
Baseline Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.
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
AudioContextwas first created that the change in value will happen. If the time is less thanAudioContext.currentTime, the change happens immediately. ATypeErroris 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 audioCtx = new AudioContext(); // set basic variables for example const myAudio = document.querySelector("audio"); const pre = document.querySelector("pre"); const myScript = document.querySelector("script"); pre.textContent = myScript.textContent; 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 its 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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