MediaTrackSettings.groupId

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MediaTrackSettings dictionary's groupId property is a browsing-session unique DOMString which identifies the group of devices which includes the source for the MediaStreamTrack . This lets you determine what value was selected to comply with your specified constraints for this property's value as described in the MediaTrackConstraints.groupId property you provided when calling either getUserMedia() .

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.

因为 RTP doesn't include this information, tracks associated with a WebRTC RTCPeerConnection will never include this property.

句法

var groupId = MediaTrackSettings.groupId;

值

A DOMString whose value is a browsing-session unique identifier for a group of devices which includes the source of the track's contents. Two devices share the same group ID if they belong to the same physical hardware device. For example, a headset has two devices on it: a microphone which can serve as a source for audio tracks and a speaker which can serve as an output for audio.

The group ID is not usable across multiple browsing sessions. However, it can be used to ensure that audio input and output are both being performed on the same headset, for example, or to ensure that the built-in camera and microphone on a phone are being used for video conferencing purposes.

The actual value of the string, however, is determined by the source of the track, and there is no guarantee what form it will take, although the specification does recommend it be a GUID.

Since this property isn't stable across browsing sessions, its usefulness when calling getUserMedia() is generally limited to ensuring that tasks performed during the same browsing session use devices from the same group (or that they don't use devices from the same group). There is no situation in which the groupId is useful when calling applyConstraints() , since the value can't be changed.

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 Yes	Edge ≤79	Firefox 69	IE ?	Opera Yes	Safari ?	WebView Android Yes	Chrome Android Yes	Firefox Android No	Opera Android Yes	Safari iOS ?	Samsung Internet Android Yes

图例

完整支持
不支持
兼容性未知 ?

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元数据

最后修改： 2020 年 1 月 22 日

Media Streams API
MediaTrackSettings
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
17. width
Related pages for Media Capture and Streams

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