test.html

<!DOCTYPE html>
<html>
    <head>
        <meta charset="utf-8">
        <title></title>

        <style>

            .video-container {
                height: 500px;
                width: 500px;
                overflow: hidden;
                position: relative;
            }

            video {
              min-width: 100%;
              min-height: 100%;
              position: absolute;
              top: 50%;
              left: 50%;
              transform: translateX(-50%) translateY(-50%);
            }
        </style>

    </head>

    <body>

        <div class="video-container">
            <video autoplay muted loop>
                <source src="http://clips.vorwaerts-gmbh.de/VfE_html5.mp4" type="video/mp4">
            </video>
            <h2>Your caption here</h2>
        </div>

    </body>
</html>