pinafore/routes/_components/AutoplayVideo.html

<video
  class="autoplay-video {{className || ''}}"
  aria-label="{{ariaLabel || ''}}"
  style="background-image: url({{poster}});"
  :poster
  :width
  :height
  :src
  autoplay
  muted
  loop
  webkit-playsinline
  playsinline
/>
<style>
  .autoplay-video {
    background-repeat: no-repeat;
    background-position: center;
    background-size: contain;
  }
</style>