AudioParam: setValueCurveAtTime() method
The
setValueCurveAtTime()
method of the
AudioParam
interface schedules the parameter's value to change
following a curve defined by a list of values.
The curve is a linear
interpolation between the sequence of values defined in an array of floating-point
values, which are scaled to fit into the given interval starting at
startTime
and a specific duration.
Syntax
js
setValueCurveAtTime(values, startTime, duration)
Parameters
values
-
An array of floating-point numbers representing the value curve the
AudioParam
will change through along the specifiedduration
. Every value in the array must be a finite number; if any value isNaN
,Infinity
, or-Infinity
, aTypeError
exception is thrown. startTime
-
A double representing the time (in seconds) after the
AudioContext
was first created that the change in value will happen. If this value is lower thanAudioContext.currentTime
, it is clamped tocurrentTime
. duration
-
A double representing the total time (in seconds) over which the parameter's
value
will change following the specified curve. The specified values are spaced equally along this duration.
Return value
A reference to this AudioParam
object. Some older browser implementations
of this interface return undefined
.
Exceptions
InvalidStateError
DOMException
-
Thrown if the specified array of
values
has fewer than 2 items in it. RangeError
-
Thrown if the specified
startTime
is either negative or a non-finite value, orduration
is not a finite, strictly positive number. TypeError
-
Thrown if one or more of the values in the
values
array is non-finite. Non-finite values areNaN
,Infinity
, and-Infinity
.
Usage notes
When the parameter's value finishes following the curve, its value is guaranteed to
match the last value in the set of values specified in the values
parameter.
Note: Some early implementations of the Web Audio API did not ensure this to be the case, causing unexpected results.
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:
js
// create audio context
const audioCtx = new AudioContext();
// set basic variables for example
const myAudio = document.querySelector("audio");
const valueCurve = document.querySelector(".value-curve");
// 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;
const 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
const 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 = () => {
gainNode.gain.setValueCurveAtTime(waveArray, audioCtx.currentTime, 2);
};
Specifications
Specification |
---|
Web Audio API # dom-audioparam-setvaluecurveattime |
Browser compatibility
BCD tables only load in the browser
Versions before Chrome 46 use nearest neighbor instead of linear interpolation.