ConstantSourceNode

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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 参数。

输入数	`0`
输出数	`1`

构造函数

ConstantSourceNode(): 创建并返回新 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() .

特性

继承来自其父级接口的特性， AudioScheduledSourceNode , and adds the following properties:

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

事件处理程序

Inherits event handlers from its parent interface, AudioScheduledSourceNode .

Some browsers' implementations of this event handler are part of the AudioScheduledSourceNode 接口。

onended: Fired whenever the ConstantSourceNode data has stopped playing.

方法

Inherits methods from its parent interface, AudioScheduledSourceNode .

Some browsers' implementations of these methods are part of the AudioScheduledSourceNode 接口。

start()
stop()

范例

In the article Controlling multiple parameters with ConstantSourceNode ， ConstantSourceNode is created to allow one slider control to change the gain on two GainNode s. 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.

规范

规范	状态	注释
Web 音频 API The definition of 'ConstantSourceNode' in that specification.	工作草案

浏览器兼容性

The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request. 更新 GitHub 上的兼容性数据

	桌面						移动
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`ConstantSourceNode`	Chrome 56	Edge ≤79	Firefox 52 注意事项 52 注意事项 `ConstantSourceNode` inherited from `AudioNode` initially, but was changed in Firefox 53 to inherit from `AudioScheduledSourceNode` .	IE 不支持 No	Opera 43	Safari 不支持 No	WebView Android 56	Chrome Android 56	Firefox Android 52 注意事项 52 注意事项 `ConstantSourceNode` inherited from `AudioNode` initially, but was changed in Firefox 53 to inherit from `AudioScheduledSourceNode` .	Opera Android 43	Safari iOS 不支持 No	Samsung Internet Android 6.0
`ConstantSourceNode()` 构造函数	Chrome 56	Edge ≤79	Firefox 52	IE 不支持 No	Opera 43	Safari 不支持 No	WebView Android 56	Chrome Android 56	Firefox Android 52	Opera Android 43	Safari iOS 不支持 No	Samsung Internet Android 6.0
`offset`	Chrome 56	Edge 79	Firefox 不支持 52 — 53 注意事项 52 — 53 注意事项 This property is still available, but via the inheritance of `AudioScheduledSourceNode` .	IE 不支持 No	Opera 不支持 No	Safari 不支持 No	WebView Android 不支持 No	Chrome Android 不支持 No	Firefox Android 不支持 52 — 53 注意事项 52 — 53 注意事项 This property is still available, but via the inheritance of `AudioScheduledSourceNode` .	Opera Android 不支持 No	Safari iOS 不支持 No	Samsung Internet Android 不支持 No
`onended`	Chrome 56	Edge 79	Firefox 不支持 52 — 53 注意事项 52 — 53 注意事项 This property is still available, but via the inheritance of `AudioScheduledSourceNode` .	IE 不支持 No	Opera 不支持 No	Safari 不支持 No	WebView Android 56	Chrome Android 56	Firefox Android 不支持 52 — 53 注意事项 52 — 53 注意事项 This property is still available, but via the inheritance of `AudioScheduledSourceNode` .	Opera Android 不支持 No	Safari iOS 不支持 No	Samsung Internet Android 6.0
`start`	Chrome 56	Edge 79	Firefox 不支持 52 — 53 注意事项 52 — 53 注意事项 This property is still available, but via the inheritance of `AudioScheduledSourceNode` .	IE 不支持 No	Opera 不支持 No	Safari 不支持 No	WebView Android 56	Chrome Android 56	Firefox Android 不支持 52 — 53 注意事项 52 — 53 注意事项 This property is still available, but via the inheritance of `AudioScheduledSourceNode` .	Opera Android 不支持 No	Safari iOS 不支持 No	Samsung Internet Android 6.0
`stop`	Chrome 56	Edge 79	Firefox 不支持 52 — 53 注意事项 52 — 53 注意事项 This property is still available, but via the inheritance of `AudioScheduledSourceNode` .	IE 不支持 No	Opera 不支持 No	Safari 不支持 No	WebView Android 56	Chrome Android 56	Firefox Android 不支持 52 — 53 注意事项 52 — 53 注意事项 This property is still available, but via the inheritance of `AudioScheduledSourceNode` .	Opera Android 不支持 No	Safari iOS 不支持 No	Samsung Internet Android 6.0

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构造函数

特性

事件处理程序

方法

范例

规范

浏览器兼容性

图例

另请参阅

元数据

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