.OL {
   display: block;
   margin-left: auto;
   margin-right: auto;
}
.containertube {
    position: relative;
    width: 100%;
    height: 0;
    padding-bottom: 56.25%;
}
.videotube {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
}