body {
  margin: 0;
  background: #000; 
}
video { 
    position: fixed;
    top: 50%;
    left: 50%;

width: 100%;
height: 100%;
    z-index: -1;
    -webkit-transform: translateX(-50%) translateY(-50%);
 }

img
{
  position: absolute;
  display: block;
  max-width: 100%;
  max-height: 100%;
  left: 0;
  right: 0;
  top: 0;
  bottom: 0;
  margin: auto;
}