.banner_area {
    position: relative;
    height: 1425px;
    overflow:hidden;
}
.banner_video {
    position: relative;
    padding-bottom: 56.25%; /* 16:9 */
    height: 0;
}
.banner_video iframe {
    position: absolute;
    top: -175px;
    left: 0;
    width: 100%;
    height: 100%;
}
@media screen and (max-width: 640px) {
  .banner_area {
      height: 200px;
  }
  .banner_video iframe {
      top: 0px;
  }
}