Documentation

Class: VideoTrack

VideoTrack

A VideoTrack is a Track representing video.

Properties:
Name Type Argument Description
isStarted boolean

Whether or not the VideoTrack has started; if the VideoTrack started, there is enough video data to begin playback
isEnabled boolean

Whether or not the VideoTrack is enabled; if the VideoTrack is not enabled, it is "paused"
dimensions VideoTrack.Dimensions

The VideoTrack's VideoTrack.Dimensions
kind Track.Kind

"video"
mediaStreamTrack MediaStreamTrack

A video MediaStreamTrack
processedTrack MediaStreamTrack <nullable>

The source of processed video frames. It is null if no VideoProcessor has been added.
processor VideoProcessor <nullable>

A VideoProcessor that is currently processing video frames. It is null if video frames are not being processed.
Fires:

Extends

Methods

addProcessor(processor)

Add a VideoProcessor to allow for custom processing of video frames belonging to a VideoTrack. Only Chrome supports this as of now. Calling this API from a non-supported browser will result in a log warning.

Parameters:
Name Type Description
processor VideoProcessor

The VideoProcessor to use.
Returns:
Type
this
Example
class GrayScaleProcessor {
  constructor(percentage) {
    this.outputFrame = new OffscreenCanvas(0, 0);
    this.percentage = percentage;
  }
  processFrame(inputFrame) {
    this.outputFrame.width = inputFrame.width;
    this.outputFrame.height = inputFrame.height;

    const context = this.outputFrame.getContext('2d');
    context.filter = `grayscale(${this.percentage}%)`;
    context.drawImage(inputFrame, 0, 0, inputFrame.width, inputFrame.height);
    return this.outputFrame;
  }
}

Video.createLocalVideoTrack().then(function(videoTrack) {
  videoTrack.addProcessor(new GrayScaleProcessor(100));
});

attach()

Create an HTMLVideoElement and attach the VideoTrack to it.

The HTMLVideoElement's srcObject will be set to a new MediaStream containing the VideoTrack's MediaStreamTrack.

Returns:

videoElement

Type
HTMLVideoElement
Example
const Video = require('twilio-video');

Video.createLocalVideoTrack().then(function(videoTrack) {
  const videoElement = videoTrack.attach();
  document.body.appendChild(videoElement);
});

attach(mediaElement)

Attach the VideoTrack to an existing HTMLMediaElement. The HTMLMediaElement could be an HTMLAudioElement or an HTMLVideoElement.

If the HTMLMediaElement's srcObject is not set to a MediaStream, this method sets it to a new MediaStream containing the VideoTrack's MediaStreamTrack; otherwise, it adds the MediaTrack's MediaStreamTrack to the existing MediaStream. Finally, if there are any other MediaStreamTracks of the same kind on the MediaStream, this method removes them.

Parameters:
Name Type Description
mediaElement HTMLMediaElement

The HTMLMediaElement to attach to
Returns:

mediaElement

Type
HTMLMediaElement
Example
const Video = require('twilio-video');

const videoElement = document.createElement('video');
document.body.appendChild(videoElement);

Video.createLocalVideoTrack().then(function(videoTrack) {
  videoTrack.attach(videoElement);
});

attach(selector)

Attach the VideoTrack to an HTMLMediaElement selected by document.querySelector. The HTMLMediaElement could be an HTMLAudioElement or an HTMLVideoElement.

If the HTMLMediaElement's srcObject is not set to a MediaStream, this method sets it to a new MediaStream containing the VideoTrack's MediaStreamTrack; otherwise, it adds the VideoTrack's MediaStreamTrack to the existing MediaStream. Finally, if there are any other MediaStreamTracks of the same kind on the MediaStream, this method removes them.

Parameters:
Name Type Description
selector string

A query selector for the HTMLMediaElement to attach to
Returns:

mediaElement

Type
HTMLMediaElement
Example
const Video = require('twilio-video');

const videoElement = document.createElement('video');
videoElement.id = 'my-video-element';
document.body.appendChild(videoElement);

Video.createLocalVideoTrack().then(function(track) {
  track.attach('#my-video-element');
});

detach()

Detach the VideoTrack from all previously attached HTMLMediaElements.

Returns:

mediaElements

Type
Array.<HTMLMediaElement>
Example
const mediaElements = videoTrack.detach();
mediaElements.forEach(mediaElement => mediaElement.remove());

detach(mediaElement)

Detach the VideoTrack from a previously attached HTMLMediaElement.

Parameters:
Name Type Description
mediaElement HTMLMediaElement

One of the HTMLMediaElements to which the VideoTrack is attached
Returns:

mediaElement

Type
HTMLMediaElement
Example
const videoElement = document.getElementById('my-video-element');
videoTrack.detach(videoElement).remove();

detach(selector)

Detach the VideoTrack from a previously attached HTMLMediaElement specified by document.querySelector.

Parameters:
Name Type Description
selector string

The query selector of HTMLMediaElement to which the VideoTrack is attached
Returns:

mediaElement

Type
HTMLMediaElement
Example
videoTrack.detach('#my-video-element').remove();

removeProcessor(processor)

Remove the previously added VideoProcessor using addProcessor API.

Parameters:
Name Type Description
processor VideoProcessor

The VideoProcessor to remove.
Returns:
Type
this
Example
class GrayScaleProcessor {
  constructor(percentage) {
    this.outputFrame = new OffscreenCanvas(0, 0);
    this.percentage = percentage;
  }
  processFrame(inputFrame) {
    this.outputFrame.width = inputFrame.width;
    this.outputFrame.height = inputFrame.height;

    const context = this.outputFrame.getContext('2d');
    context.filter = `grayscale(${this.percentage}%)`;
    context.drawImage(inputFrame, 0, 0, inputFrame.width, inputFrame.height);
    return this.outputFrame;
  }
}

Video.createLocalVideoTrack().then(function(videoTrack) {
  const grayScaleProcessor = new GrayScaleProcessor(100);
  videoTrack.addProcessor(grayScaleProcessor);
  document.getElementById('remove-button').onclick = () => videoTrack.removeProcessor(grayScaleProcessor);
});

Type Definitions

Dimensions

A VideoTrack's width and height.

Type:
  • object
Properties:
Name Type Argument Description
width number <nullable>

The VideoTrack's width or null if the VideoTrack has not yet started
height number <nullable>

The VideoTrack's height or null if the VideoTrack has not yet started

Events

dimensionsChanged

The VideoTrack's dimensions changed.

Parameters:
Name Type Description
track VideoTrack

The VideoTrack whose dimensions changed

disabled

The VideoTrack was disabled, i.e. "paused".

Parameters:
Name Type Description
track VideoTrack

The VideoTrack that was disabled

enabled

The VideoTrack was enabled, i.e. "unpaused".

Parameters:
Name Type Description
track VideoTrack

The VideoTrack that was enabled

started

The VideoTrack started. This means there is enough video data to begin playback.

Parameters:
Name Type Description
track VideoTrack

The VideoTrack that started