daniellmb/VidBG

.vidbg {
  display: block;
  position: fixed;
  overflow: hidden;
  right: 0;
  bottom: 0;
  min-width: 100%;
  min-height: 100%;
  width: auto;
  height: auto;
  z-index: -101;
  background: url(demo/img/poster.jpg) no-repeat;
  background-size: cover;
}

.vidbg video {
  display: block;
  position: fixed;
  right: 0;
  bottom: 0;
  min-width: 100%;
  min-height: 100%;
  width: auto;
  height: auto;
  z-index: -100;
}

/* optional overlay on top of the video */
.vidbg .vidbg-overlay {
  display: block;
  position: fixed;
  right: 0;
  bottom: 0;
  min-width: 100%;
  min-height: 100%;
  width: auto;
  height: auto;
  z-index: -99;
  opacity: 0.6;
  background: url(demo/img/screen.png);
}