#video-bg {
    position: fixed;
    top: 0;
    right: 0;
    bottom: 0;
    left: 0;
    overflow: hidden;
    background-repeat: no-repeat;
    background-color: #091D23;
    z-index: -1;
    background-image: url(../images/poster.jpg);
    background-size: 50% 50%;
}
#video-bg > video {
    position: absolute;
    top: 0;
    left: 0;
    min-width: 100%; 
    min-height: 100%;
    width: auto;
    height: auto; 
}
 
@supports (object-fit: cover) {
     #video-bg > video {
         top: 0;
         left: 0;
         width: 100%;
         height: 100%;
         object-fit: cover;
     }
}