video {
  text-align: left;
  margin: 1em auto;
  padding: 0;
  border-width: 1px;
  border-style: solid;
  border-color: #c4c4c4;
  max-width: 100%;
  width: 640px;
  height: calc(640px * 0.5625);;
  background-color: #ffffff; 
}

iframe.videoframe {
  width: 320px;
  height: calc(320px * 0.5625);
  border-width: 1px;
  border-style: solid;
  border-color: #c4c4c4;
  box-sizing: border-box;
  margin: 1em; 
}