HTMLCanvasElement: captureStream() method
The HTMLCanvasElement
captureStream()
method returns a MediaStream
which includes a CanvasCaptureMediaStreamTrack
containing a real-time video capture of the canvas's contents.
Syntax
js
captureStream(frameRate)
Parameters
frameRate
Optional-
A double-precision floating-point value that indicates the rate of capture of each frame. If not set, a new frame will be captured each time the canvas changes; if set to
0
, frames will not be captured automatically; instead, they will only be captured when the returned track'srequestFrame()
method is called.
Return value
A reference to a MediaStream
object, which has a single
CanvasCaptureMediaStreamTrack
in it.
Exceptions
NotSupportedError
DOMException
-
Thrown if the value of
frameRate
is negative. SecurityError
DOMException
-
The canvas's bitmap is not origin clean; at least some of its contents have or may have been loaded from a site other than the one from which the document itself was loaded.
Example
js
// Find the canvas element to capture
const canvasElt = document.querySelector("canvas");
// Get the stream
const stream = canvasElt.captureStream(25); // 25 FPS
// Do things to the stream
// E.g. Send it to another computer using an RTCPeerConnection
// pc is an RTCPeerConnection created elsewhere
stream.getTracks().forEach((track) => pc.addTrack(track, stream));
Specifications
Specification |
---|
Media Capture from DOM Elements # dom-htmlcanvaselement-capturestream |
Browser compatibility
BCD tables only load in the browser
See also
-
HTMLMediaElement.captureStream()
, which allows capturing a stream from a media element. MediaStream
Media Capture and Streams API