微信浏览器视频不自动全屏

<video controls="controls" preload="auto" poster="" x5-video-player-fullscreen="true" webkit-playsinline="true" x-webkit-airplay="true" playsinline="true" x5-playsinline class="video" id="playvideo" onended="showBanner()">  

<source src="@ViewBag.VideoUrl" type="video/mp4" />

</video>