* {
  margin: 0px;
  padding: 0px;
  font-family: arial;
}
.container {
  width: 100%;
  height: 100%;
  display: flex;
  flex-direction: column;
}
.container > * {
  width: 100%;
  padding: 20px;
  border: solid 1px red;
}

video, img {
  max-width: 300px;
  vertical-align: text-top;
}