Video does not show in viewport

Sorry but it's not because I'm embedding. It's because you're putting your video in the background with "autoplay."  That simply won't work on most web devices due to "autoplay" blocking.  Read more about it below.

https://developer.mozilla.org/en-US/docs/Web/Media/Autoplay_guide

Try this code instead of what you have.  Add your own Poster image and Video to the code where <!--commented-->.

<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Full Page Video Background</title>
<meta name="viewport" content="width=device-width, initial-scale=1">
<style>
* {
    box-sizing: border-box;
}

body {
    margin: 0;
    font-family: Arial;
    font-size: 17px;
}


#myVideo {
    position: fixed;
    right: 0;
    bottom: 0;
    min-width: 100%; 
    min-height: 100%;
}

.content {
    position: fixed;
    bottom: 0;
    background: rgba(0, 0, 0, 0.5);
    color: #f1f1f1;
    width: 100%;
    padding: 20px;
}

#myBtn {
    width: 200px;
    font-size: 18px;
    padding: 10px;
    border: none;
    background: #000;
    color: #fff;
    cursor: pointer;
}

#myBtn:hover {
    background: #ddd;
    color: black;
}
</style>
</head>
<body>
<!--ADD YOUR POSTER IMAGE AND VIDEO FILE BELOW-->
<video 
poster="path/YOUR_POSTER_IMAGE.jpg" muted="muted" autoplay="autoplay" >
<source src="path/YOUR_VIDEO.mp4" type="video/mp4">
</video>

<div class="content">
<h1>Heading</h1>
<p>Lorem ipsum dolor sit amet, an his etiam torquatos. Tollit soleat phaedrum te duo, eum cu recteque expetendis neglegentur. Cu mentitum maiestatis persequeris pro, pri ponderum tractatos ei. Id qui nemore latine molestiae, ad mutat oblique delicatissimi pro.</p>
<button id="myBtn" onclick="myFunction()">Play/Pause</button>
</div>

<!--play/pause button-->
<script>
var video = document.getElementById("myVideo");
var btn = document.getElementById("myBtn");

function myFunction() {
  if (video.paused) {
    video.play();
    btn.innerHTML = "Pause";
  } else {
    video.pause();
    btn.innerHTML = "Play";
  }
}
</script>
</body>
</html>

Good luck with your project!