The CanvasCaptureMediaStreamTrack
method 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.
Syntax
stream.requestFrame();
Return value
undefined
Usage notes
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).
Example
// 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();
Specifications
Specification | Status | Comment |
---|---|---|
Media Capture from DOM Elements The definition of 'CanvasCaptureMediaStream.requestFrame()' in that specification. |
Working Draft | Initial definition |
Browser compatibility
Desktop | Mobile | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
requestFrame | Chrome Full support 51 | Edge Full support ≤79 | Firefox
Full support
41
| IE No support No | Opera No support No | Safari No support No | WebView Android Full support 51 | Chrome Android Full support 51 | Firefox Android ? | Opera Android No support No | Safari iOS No support No | Samsung Internet Android Full support 5.0 |
Legend
- Full support
- Full support
- No support
- No support
- Compatibility unknown
- Compatibility unknown
- Experimental. Expect behavior to change in the future.
- Experimental. Expect behavior to change in the future.
- User must explicitly enable this feature.
- User must explicitly enable this feature.
See also
CanvasCaptureMediaStream
, the interface it belongs to.<canvas>