#bgvidContainer{
    overflow: hidden;
    position: relative; /* or absolute or fixed */
}
#bgvid {
    min-height: 100vh;
    min-width:100vw;
    position: fixed;
    left:50%; /* % of surrounding element */
    top:0;
    z-index:-1;
    opacity:1;
    transform: translate(-50%, 0%);
    -webkit-transform: translate(-50%, 0%);
    -ms-transform: translate(-50%, 0%);
}
#bgvidBlack {
    min-height: 100vh;
    min-width:100vw;
    position: fixed;
    left:50%; /* % of surrounding element */
    top:0;
    z-index:-1;
    opacity:0.3;
    background-color:#000;
    transform: translate(-50%, 0%);
    -webkit-transform: translate(-50%, 0%);
    -ms-transform: translate(-50%, 0%);
}