预加载音频和视频

如果我们设置 autoplay 或者我们设置 preload="auto"，音频和视频资产将仅阻止场景：

<a-scene>
  <a-assets>
    <!-- These will not block. -->
    <audio src="blockus.mp3"></audio>
    <video src="loadofblocks.mp4"></video>

    <!-- These will block. -->
    <audio src="blocky.mp3" autoplay></audio>
    <video src="blockiscooking.mp4" preload="auto"></video>
  </a-assets>
</a-scene>