AudioParam.setValueCurveAtTime

The setValueCurveAtTime() method of the AudioParam interface schedules the start of a linear interpolation between the sequence of values defined in a Float32Array, which are scaled to fit into the given interval starting at startTime and having a specific duration.

Syntax

var paramRef = param.setValueCurveAtTime(values, startTime, duration);

Parameters

values

A Float32Array representing the value curve the AudioParam will change through along the duration. Every value in the array must be a finite number; if any value is NaN, Infinity, or -Infinity, a TypeError exception is thrown.

startTime

A double representing the time (in seconds) after the AudioContext was first created that the change in value will happen.

duration

A double representing the total time (in seconds) the values will be changed between. The values are spaced equally along this duration.

Return value

A reference to this AudioParam object. Some older browser implementations of this interface return void.

Exceptions

TypeError

One or more of the values in the values array is non-finite. Non-finite values are NaN, Infinity, and -Infinity.

Examples

In this example, we have a media source with a single button (see the webaudio-examples repo for the source code, or view the example live.) When this button is pressed, setValueCurveAtTime() is used to change the gain value between the values contained in the waveArray array:

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

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

pre.innerHTML = myScript.innerHTML;

var valueCurve = document.querySelector('.value-curve');

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

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

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

// set button to do something onclick

var waveArray = new Float32Array(9);
waveArray[0] = 0.5;
waveArray[1] = 1;
waveArray[2] = 0.5;
waveArray[3] = 0;
waveArray[4] = 0.5;
waveArray[5] = 1;
waveArray[6] = 0.5;
waveArray[7] = 0;
waveArray[8] = 0.5;

valueCurve.onclick = function() {
  gainNode.gain.setValueCurveAtTime(waveArray, audioCtx.currentTime, 2);
}

Specifications

Browser compatibility

Versions before Chrome 46 use nearest neighbor instead of linear interpolation.

See also

• Using the Web Audio API