The setValueCurveAtTime()
method of the AudioParam
Interface schedules a transition between values defined by a Float32Array
, which are scaled to fit into the given interval starting at startTime
and having a specific duration. The transition between values was undefined in the original spec but has now been specified as linear. Chrome 46.0.2490 uses linear interpolation; earlier versions use nearest neighbor (no interpolation).
Syntax
var AudioParam = AudioParam.setValueCurveAtTime(values, startTime, duration)
Parameters
- values
- A
Float32Array
representing the value curve theAudioParam
will change through along theduration
. - 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 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. In some browsers older implementations of this interface return void.
Examples
In this example, we have a media source with a single button (see the audio-param 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
Specification | Status | Comment |
---|---|---|
Web Audio API The definition of 'setValueCurveAtTime' in that specification. |
Working Draft |
Browser compatibility
Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari (WebKit) |
---|---|---|---|---|---|
Basic support | 14 webkit | 23 | Not supported | 15 webkit 22 (unprefixed) |
6 webkit |
Unprefixed | (Yes) |
Feature | Android | Android Webview | Firefox Mobile (Gecko) | Firefox OS | IE Phone | Opera Mobile | Safari Mobile | Chrome for Android |
---|---|---|---|---|---|---|---|---|
Basic support | Not supported | ? | 25 | 1.2 | Not supported | Not supported | 6 webkit | 28 webkit |
Unprefixed | ? | (Yes) | (Yes) |