VideoTrackGenerator

Limited availability

This feature is not Baseline because it does not work in some of the most widely-used browsers.

Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

The VideoTrackGenerator interface of the Insertable Streams for MediaStreamTrack API has a WritableStream property that acts as a MediaStreamTrack source, by consuming a stream of VideoFrames as input.

This interface is only available in dedicated workers.

Constructor

VideoTrackGenerator()

Creates a new VideoTrackGenerator object which accepts VideoFrame objects.

Instance properties

VideoTrackGenerator.muted

A Boolean property to temporarily halt or resume the generation of video frames in the output track.

VideoTrackGenerator.track

The output MediaStreamTrack.

VideoTrackGenerator.writable

The input WritableStream.

Examples

The following example is from the article Unbundling MediaStreamTrackProcessor and VideoTrackGenerator. It transfers a camera MediaStreamTrack to a worker for processing. The worker creates a pipeline that applies a sepia tone filter to the video frames and mirrors them. The pipeline culminates in a VideoTrackGenerator whose MediaStreamTrack is transferred back and played. The media now flows in real time through the transform off the main thread.

js
const stream = await navigator.mediaDevices.getUserMedia({ video: true });
const [track] = stream.getVideoTracks();
const worker = new Worker("worker.js");
worker.postMessage({ track }, [track]);
const { data } = await new Promise((r) => (worker.onmessage = r));
video.srcObject = new MediaStream([data.track]);

worker.js:

js
onmessage = async ({ data: { track } }) => {
  const vtg = new VideoTrackGenerator();
  self.postMessage({ track: vtg.track }, [vtg.track]);
  const { readable } = new MediaStreamTrackProcessor({ track });
  await readable
    .pipeThrough(new TransformStream({ transform }))
    .pipeTo(vtg.writable);
};

See also

Specifications

Specification
MediaStreamTrack Insertable Media Processing using Streams
# videotrackgenerator

Browser compatibility