wayvr/uidev/assets/gui/video.xml

<layout>
  <elements>
    <rectangle position="absolute" width="10000" height="10000"/>
    <div margin="16" gap="8" flex_direction="column">
      <label text="aaa"/>
      <Video src="test.ivf" width="320" height="240"/>
    </div>
  </elements>
</layout>