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• 句法
• 范例
• 规范
• 浏览器兼容性
• 另请参阅
• 相关话题

MediaTrackSupportedConstraints dictionary's autoGainControl property is a read-only Boolean value which is present (and set to true ) in the object returned by MediaDevices.getSupportedConstraints() if and only if the 用户代理 支持 autoGainControl constraint. If the constraint isn't supported, it's not included in the list, so this value will never be false .

You can access the supported constraints dictionary by calling navigator.mediaDevices.getSupportedConstraints() .

autoGainControl constraint indicates whether or not the browser offers the ability to automatically control the gain (volume) on media tracks; this obviously is contingent on whether or not the individual device supports automatic gain control as well; it's typically a feature provided by microphones.

句法

autoGainSupported = supportedConstraintsDictionary.autoGainControl;
					

值

This property is present in the dictionary (and its value is always true ) if the user agent supports the autoGainControl constraint. If the property isn't present, this property is missing from the supported constraints dictionary, and you'll get undefined if you try to look at its value.

范例

This example simply displays whether or not your browser supports the autoGainControl constraint.

HTML 内容

<div id="result">
</div>
					

CSS content

#result {
  font: 14px "Arial", sans-serif;
}
					

JavaScript 内容

let result = document.getElementById("result");
if (navigator.mediaDevices.getSupportedConstraints().autoGainControl) {
    result.innerHTML = "Supported!";
} else {
    result.innerHTML = "Not supported!";
}
					

结果

规范

规范	状态	注释
媒体捕获和流 The definition of 'autoGainControl' in that specification.	候选推荐	最初的规范。

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
autoGainControl	Chrome 69	Edge ≤79	Firefox 55 55 不支持 ? — 55 Prefixed Prefixed Implemented with the vendor prefix: moz	IE ?	Opera Yes	Safari ?	WebView Android 69	Chrome Android 69	Firefox Android 55 55 不支持 ? — 55 Prefixed Prefixed Implemented with the vendor prefix: moz	Opera Android Yes	Safari iOS ?	Samsung Internet Android 10.0

图例

完整支持

完整支持

兼容性未知 ?

兼容性未知

要求使用供应商前缀或不同名称。

要求使用供应商前缀或不同名称。

另请参阅

• Media Capture and Streams API
• MediaDevices.getSupportedConstraints()
• MediaTrackSupportedConstraints
• MediaStreamTrack

元数据

• 最后修改： 2020 年 1 月 22 日

相关话题

1. Media Streams API
2. MediaTrackSupportedConstraints
3. 特性

   1. aspectRatio
   2. autoGainControl
   3. channelCount
   4. cursor
   5. deviceId
   6. displaySurface
   7. echoCancellation
   8. facingMode
   9. frameRate
   10. groupId
   11. height
   12. latency
   13. noiseSuppression
   14. sampleRate
   15. sampleSize
   16. volume
4. Related pages for Media Capture and Streams

   1. AudioStreamTrack
   2. BlobEvent
   3. CanvasCaptureMediaStream
   4. ConstrainBoolean
   5. ConstrainDOMString
   6. ConstrainDouble
   7. ConstrainLong
   8. DoubleRange
   9. HTMLCanvasElement.captureStream()
   10. LongRange
   11. MediaDevices
   12. MediaStream
   13. MediaStreamTrack
   14. MediaStreamTrackEvent
   15. MediaTrackCapabilities
   16. MediaTrackConstraints
   17. MediaTrackSettings
   18. Navigator.mediaDevices
   19. NavigatorUserMedia
   20. NavigatorUserMediaError
   21. VideoStreamTrack
   22. navigator.mediaDevices.getUserMedia()