video {
  left: 50%;
  position: absolute;
  top: 50%;
  transform: translate(-50%, -50%);
  width: 30%;
  min-width: 300px;
  -webkit-mask-image: -webkit-radial-gradient(white, black);            /*This removes the grey border */
  -webkit-backface-visibility: hidden;
  -moz-backface-visibility: hidden;
}