在此页

• 句法
• 用法注意事项
• 范例
• 规范
• 浏览器兼容性
• 另请参阅
• 相关话题

CanvasCaptureMediaStreamTrack 方法 requestFrame() requests that a frame be captured from the canvas and sent to the stream. Applications that need to carefully control the timing of rendering and frame capture can use requestFrame() to directly specify when it's time to capture a frame.

To prevent automatic capture of frames, so that frames are only captured when requestFrame() is called, specify a value of 0 for the captureStream() method when creating the stream.

句法

stream.requestFrame();
					

返回值

undefined

用法注意事项

There is currently an issue flagged in the specification pointing out that at this time, no exceptions are being thrown if the canvas isn't origin-clean. This may change in the future, so it would be wise to plan ahead and watch for exceptions such as SecurityError (although the specific error that might be thrown is not mentioned in the spec, this is a likely candidate).

范例

// Find the canvas element to capture
var canvasElt = document.getElementsByTagName("canvas")[0];
// Get the stream
var stream = canvasElt.captureStream(25); // 25 FPS
// Send the current state of the canvas as a frame to the stream
stream.getVideoTracks()[0].requestFrame();
					

规范

规范	状态	注释
Media Capture from DOM Elements The definition of 'CanvasCaptureMediaStream.requestFrame()' in that specification.	工作草案	初始定义

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
requestFrame	Chrome 51	Edge ≤79	Firefox 41	IE No	Opera No	Safari No	WebView Android 51	Chrome Android 51	Firefox Android ?	Opera Android No	Safari iOS No	Samsung Internet Android 5.0

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

实验。期望将来行为有所改变。

实验。期望将来行为有所改变。

用户必须明确启用此特征。

用户必须明确启用此特征。

另请参阅

• CanvasCaptureMediaStream , the interface it belongs to.
• <canvas>

元数据

• 最后修改： Jan 30, 2020

相关话题

1. Media Streams API
2. CanvasCaptureMediaStreamTrack
3. 特性

   1. canvas
4. 方法

   1. requestFrame()
5. 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. MediaTrackSupportedConstraints
   19. Navigator.mediaDevices
   20. NavigatorUserMedia
   21. NavigatorUserMediaError
   22. VideoStreamTrack
   23. navigator.mediaDevices.getUserMedia()