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• 句法
• 范例
• 规范
• 浏览器兼容性
• 另请参阅
• 相关话题

MediaTrackConstraints dictionary's groupId 特性为 ConstrainDOMString describing the requested or mandatory constraints placed upon the value of the groupId constrainable property.

If needed, you can determine whether or not this constraint is supported by checking the value of MediaTrackSupportedConstraints.groupId as returned by a call to MediaDevices.getSupportedConstraints() . However, typically this is unnecessary since browsers will simply ignore any constraints they're unfamiliar with.

句法

var constraintsObject = { groupId: constraint };
constraintsObject.groupId = constraint;
					

值

An object based on ConstrainDOMString specifying one or more acceptable, ideal, and/or exact (mandatory) group IDs which are acceptable as the source of media content.

Group IDs are unique for a given origin for the duration of a single browsing session, and are shared by all media sources that come from the same physical device. For example, the microphone and speaker on the same headset would share a group ID. This makes it possible to use the group ID to ensure that the audio and input devices are on the same headset by retrieving the group ID of the input device and specifying it when asking for an output device, perhaps.

However, the value of the groupId is determined by the source of the track's content, and there's no particular format mandated by the specification (although some kind of GUID is recommended). That means that a given track will only return one value for the groupId when you call getCapabilities() , and keep in mind that this value will change for each browsing session.

Because of this, there's no use for the group ID when calling MediaStreamTrack.applyConstraints() , since there is only one possible value, and you can't use it to ensure the same group is used across multiple browsing sessions when calling getUserMedia() .

范例

见 Example: Constraint exerciser in Capabilities, constraints, and settings 范例。

规范

规范	状态	注释
媒体捕获和流 The definition of 'groupId' 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
groupId	Chrome 59	Edge ≤79	Firefox 70	IE No	Opera Yes	Safari ?	WebView Android 59	Chrome Android 59	Firefox Android No	Opera Android ?	Safari iOS ?	Samsung Internet Android 7.0

图例

完整支持

完整支持

不支持

不支持

兼容性未知 ?

兼容性未知

另请参阅

• Media Capture and Streams API
• Capabilities, constraints, and settings
• MediaTrackConstraints
• 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. MediaTrackConstraints
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. logicalSurface
   14. noiseSuppression
   15. sampleRate
   16. sampleSize
   17. volume
   18. width
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. MediaTrackSettings
   17. MediaTrackSupportedConstraints
   18. Navigator.mediaDevices
   19. NavigatorUserMedia
   20. NavigatorUserMediaError
   21. VideoStreamTrack
   22. navigator.mediaDevices.getUserMedia()