How to play local video file
============================
First, in html file we create a video component and a play button

<video id="video1" autoplay controls></video>
<button id="playbutton1">Play</button>

Then in javascript

const video1 = document.getElementById("video1");
const play1  = document.getElementById("playbutton1");
play1.onclick = async() => {
    console.log("play1");
    video1.setAttribute("src", "./video1.mp4");
    video1.load();
};

How to get the stream
=====================

video1.onplay = async() => {
    const stream = video1.captureStream();
}