HTMLCanvasElement.captureStream()

The HTMLCanvasElement captureStream() method returns a MediaStream which includes a CanvasCaptureMediaStreamTrack containing a real-time video capture of the canvas's contents.

Syntax

MediaStream = canvas.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's requestFrame() method is called.

Return value

A reference to a MediaStream object, which has a single CanvasCaptureMediaStreamTrack in it.

Exceptions

NotSupportedError

The value of frameRate is negative.

Example

// Find the canvas element to capture
var canvasElt = document.querySelector('canvas');

// Get the stream
var 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
pc.addStream(stream);

Specifications

Browser compatibility

See also

• HTMLMediaElement.captureStream(), which allows capturing a stream from a media element.
• MediaStream
• Media Capture and Streams API