Class VideoReader

const video = document.querySelector<HTMLVideoElement>('video')!
const canvas = document.querySelector<HTMLCanvasElement>('canvas')!;
try {
const FPS = 30
await loadOpencv()
const c = new VideoReader(video, canvas)
await c.canPlay()
const src = c.mat // read only!
const dst = new cv.Mat(src.rows, src.cols, cv.CV_8UC1)
const process = () => {
let t0 = now()
c.read() // reads video frame on src
cv.cvtColor(src, dst, cv.COLOR_RGBA2GRAY)
cv.imshow(canvas, dst)
let delay = 1000 / FPS - msFrom(t0)
setTimeout(process, delay)
}
process()
} catch (error) {
console.log('navigator.MediaDevices.getUserMedia error: ', error.message, error.name);
console.trace(error)
}