ConstantSourceNode

この記事はまだボランティアによって 日本語 に翻訳されていません。ぜひ MDN に参加して翻訳を手伝ってください!
この記事を English (US) で読むこともできます。

The ConstantSourceNode interface—part of the Web Audio API—represents an audio source (based upon AudioScheduledSourceNode) whose output is single unchanging value. This makes it useful for cases in which you need a constant value coming in from an audio source. In addition, it can be used like a constructible AudioParam by automating the value of its offset or by connecting another node to it; see Controlling multiple parameters with ConstantSourceNode.

A ConstantSourceNode has no inputs and exactly one monaural (one-channel) output. The output's value is always the same as the value of the offset parameter.

Some implementations of this interface inherit from AudioSourceNode directly, implementing AudioScheduledSourceNode's properties and methods.

Number of inputs 0
Number of outputs 1
Channel count 1

Constructor

ConstantSourceNode()
Creates and returns a new ConstantSourceNode instance, optionally specifying an object which establishes initial values for the object's properties. You can also create a ConstantSourceNode whose properties are initialized to their default values by calling AudioContext.createConstantSource().

Properties

Inherits properties from its parent interface, AudioScheduledSourceNode, and adds the following properties:

offset
An AudioParam which specifies the value that this source continuously outputs. The default value is 1.0.

Event handlers

Inherits event handlers from its parent interface, AudioScheduledSourceNode.

Some browsers' implementations of this event handler are part of the  AudioScheduledSourceNode interface.

onended
Fired whenever the ConstantSourceNode data has stopped playing.

Methods

Inherits methods from its parent interface, AudioScheduledSourceNode.

Some browsers' implementations of these methods are part of the AudioScheduledSourceNode interface.

start()
Schedules a sound to playback at an exact time.
stop()
Schedules a sound to stop playback at an exact time.

Example

In the article Controlling multiple parameters with ConstantSourceNode, a ConstantSourceNode is created to allow one slider control to change the gain on two GainNodes. The three nodes are set up like this:

gainNode2 = context.createGain();
gainNode3 = context.createGain();
gainNode2.gain.value = gainNode3.gain.value = 0.5;
volumeSliderControl.value = gainNode2.gain.value;

constantNode = context.createConstantSource();
constantNode.connect(gainNode2.gain);
constantNode.connect(gainNode3.gain);
constantNode.start();

gainNode2.connect(context.destination);
gainNode3.connect(context.destination);

This code starts by creating the gain nodes and setting them and the volume control that will adjust their value all to 0.5. Then the ConstantSourceNode is created by calling AudioContext.createConstantSource(), and the gain parameters of each of the two gain nodes are connected to the ConstantSourceNode. After starting the constant source by calling its start() method. Finally, the two gain nodes are connected to the audio destination (typically speakers or headphones).

Now, whenever the value of constantNode.offset changes, the gain on both gainNode2 and gainNode3 will change to have that same value.

To see this example in action, as well as to read the rest of the code from which these snippets were derived, see Controlling multiple parameters with ConstantSourceNode.

Specification

Specification Status Comment
Web Audio API
The definition of 'ConstantSourceNode' in that specification.
Working Draft  

Browser compatibility

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support No ?521 No No No
ConstantSourceNode() constructor No ?52 No No No
offset56 No52 — 532 No No No
onended14 No52 — 532 No No No
start14 No52 — 532 No No No
stop14 No52 — 532 No No No
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidOpera AndroidiOS SafariSamsung Internet
Basic support No No ?521 No No No
ConstantSourceNode() constructor No No ?52 No No No
offset No No No52 — 532 No No No
onended1414 No52 — 532 No No No
start1414 No52 — 532 No No No
stop1414 No52 — 532 No No No

1. ConstantSourceNode inherited from AudioNode initially, but was changed in Firefox 53 to inherit from AudioScheduledSourceNode.

2. This property is still available, but via the inheritance of AudioScheduledSourceNode.

See also

ドキュメントのタグと貢献者

 このページの貢献者: raohmaru, fscholz, lukehorvat, Sheppy, jpmedley
 最終更新者: raohmaru,