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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 frameRate 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 frameRate constraint. If the constraint isn't supported, it's not included in the list, so this value will never be false .

frameRate constraint can be used to establish acceptable upper and lower bounds on the video frame rate for a new video track, or to specify an exact frame rate that must be provided for the request to succeed. Checking the value of this property lets you determine if the user agent allows constraining the video track configuration by frame rate. See the 范例 to see how this can be used.

句法

frameRateConstraintSupported = supportedConstraintsDictionary.frameRate;
					

值

This property is present in the dictionary if the user agent supports the frameRate constraint. If the property isn't present, the user agent doesn't allow specifying limits on the frame rate for video tracks.

If this property is present, its value is always true .

范例

This simple example looks to see if your browser supports constraining the frame rate when requesting video tracks.

JavaScript

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

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

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

结果

The output, showing if your browser supports the frameRate constraint, is:

While this example is trivial, you can replace the simple output of "Supported" vs. "Not supported" with code to provide alternative methods for presenting the audiovisual information you want to share with the user or otherwise work with.

规范

浏览器兼容性

图例

完整支持

完整支持

兼容性未知 ?

兼容性未知

另请参阅

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

• 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()