CanvasCaptureMediaStreamTrack.requestFrame()

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

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidiOS SafariSamsung Internet
Basic support
Experimental
Chrome ? Edge ? Firefox Full support 41
Disabled
Full support 41
Disabled
Disabled From version 41: this feature is behind the canvas.capturestream.enabled preference (needs to be set to true). To change preferences in Firefox, visit about:config.
IE No support NoOpera ? Safari ? WebView Android ? Chrome Android ? Edge Mobile ? Firefox Android ? Opera Android ? Safari iOS ? Samsung Internet Android ?

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

Document Tags and Contributors

Contributors to this page: fscholz, Sheppy, Sebastianz, tstrokes, teoli
Last updated by: fscholz,