Is There A Way To Send Video Data From A Video Tag/mediastream To An Offscreencanvas?

Basically I want to be able to perform effectively this same code: const video = document.getElementById('video'); const canvas = document.getElementById('canvas'); const context

Solution 1:

You can send frames of a video to an OffscreenCanvas in a Web Worker by modifying your script with the following changes:

const worker = new Worker('my-worker.js');
const video = document.getElementById('video');
const stream = video.captureStream();
const [track] = stream.getVideoTracks();
const imageCapture = new ImageCapture(track);
const canvas = document.getElementById('canvas');
const offscreen = canvas.transferControlToOffscreen();

worker.postMessage({ offscreen }, [offscreen]);

const draw = () => {
  imageCapture.grabFrame().then(imageBitmap => {
    worker.postMessage({ imageBitmap }, [imageBitmap]);
  });

  requestAnimationFrame(draw);
};

video.onplay = () => {
  requestAnimationFrame(draw);
};

my-worker.js

let canvas;
let context;

addEventListener('message', event => {
  if (event.data.offscreen) {
    canvas = event.data.offscreen;
    context = canvas.getContext('2d');
  } else if (event.data.imageBitmap && context) {
    context.drawImage(event.data.imageBitmap, 0, 0);
    // do something with frame
  }
});

References

• HTMLMediaElement.prototype.captureStream()
• MediaStream.prototype.getVideoTracks()
• new ImageCapture()
• ImageCapture.prototype.grabFrame()