MediaStreamConstraints.video

The MediaStreamConstraints dictionary's video property is used to indicate what kind of video track, if any, should be included in the MediaStream returned by a call to getUserMedia().

To learn more about how constraints work, see Capabilities, constraints, and settings.

Syntax

var videoConstraints = true | false | MediaTrackConstraints;

Value

The value of the video property can be specified as either of two types:

Boolean

If a Boolean value is specified, it simply indicates whether or not a video track should be included in the returned stream; if it's true, a video track is included; if no video source is available or if permission is not given to use the video source, the call to getUserMedia() will fail. If false, no video track is included.

MediaTrackConstraints

A constraints dictionary detailing the preferable and/or required values or ranges of values for the track's constrainable properties. If you specify constraints, a video track meeting these constraints is required.

Examples

Using a Boolean value

In this example, we provide a simple value of true for the video property. This tells getUserMedia() that we require a video track, but we don't care about any specifics beyond that.

document.getElementById("startButton").addEventListener("click", function() {
  navigator.mediaDevices.getUserMedia({
      video: true
  }).then(stream => videoElement.srcObject = stream)
    .catch(err => log(err.name + ": " + err.message));
}, false);

Here we see an event handler for a click event which uses getUserMedia() to obtain a video-only stream with no specific constraints, then attaches the resulting stream to a <video> element once the stream is returned.

Result

Using a MediaTrackConstraints object

Now let's look at a similar example that uses a set of constraints based on the MediaTrackConstraints dictionary:

document.getElementById("startButton").addEventListener("click", function() {
  navigator.mediaDevices.getUserMedia({
      video: {
        width: 160,
        height: 120,
        frameRate: 15
      }
  }).then(stream => videoElement.srcObject = stream)
    .catch(err => log(err.name + ": " + err.message));
}, false);

Here we see an event handler for a click event which calls getUserMedia(), specifying a set of video constraints that indicate a preference for a video track whose dimensions are as close as possible to 160x120 pixels, and whose frame rate is as close to 15 frames per second as possible. As long as a video input device is available and the user allows it to be used, a video track will be included in the resulting stream, and it will match the specified constraints as well as possible.

Result

Specifications

Specification	Status	Comment
Media Capture and Streams The definition of 'MediaStreamConstraints.video' in that specification.	Editor's Draft	Initial specification.

Browser compatibility

See also

• Media Capture and Streams API
• Capabilities, constraints, and settings
• MediaDevices.getUserMedia()
• MediaDevices.getSupportedConstraints()
• MediaTrackSupportedConstraints
• MediaTrackConstraints