<div id="container">
    <video id="background_video" loop muted></video>
    <div id="video_cover"></div>
    <div id="overlay"></div>

    <div id="video_controls">
      <span id="play">
        <img src="play.png">
      </span>
      <span id="pause">
        <img src="pause.png">
      </span>
    </div>

    <section id="main_content">
      <div id="head">
        <h1>HTML5轻松实现全屏视频背景-Bideo.js</h1>
        <p class="sub_head">一个可以轻松添加页面全屏背景视频的Javscript库</p>
        <p class="info">(稍等片刻，视频加载需要一点点时间.)</p>
      </div>
    </section>
</div>

* {
  margin: 0; padding: 0;
}

html, body {
  width: 100%;
  height: 100%;
  overflow: hidden;
}

#container {
  overflow: hidden;
  position: absolute;
  top: 0; left: 0; right: 0; bottom: 0;
  height: 100%;
}

#background_video {
  position: absolute;

  top: 50%; left: 50%;
  transform: translate(-50%, -50%);

  object-fit: cover;
  height: 100%; width: 100%;
}

#video_cover {
  position: absolute;

  width: 100%; height: 100%;

  background: url('video_cover.jpeg') no-repeat;
  background-size: cover;
  background-position: center;
}

#overlay {
  position: absolute;
  top: 0; right: 0; left: 0; bottom: 0;
  background: rgba(0,0,0,0.5);
}

<script src="bideo.js"></script>

(function () {
  var bv = new Bideo();
  bv.init({
    // Video元素
    videoEl: document.querySelector('#background_video'),

    // 容器元素
    container: document.querySelector('body'),

    // 自适应调整
    resize: true,

    // autoplay: false,

    isMobile: window.matchMedia('(max-width: 768px)').matches,

    playButton: document.querySelector('#play'),
    pauseButton: document.querySelector('#pause'),

    // 加载视频源, 根据实际业务更换自己的视频源文件
    src: [
      {
        src: 'http://ak4.picdn.net/shutterstock/videos/4170274/preview/stock-footage-beautiful-girl-lying-on-the-meadow-and-dreaming-enjoy-nature-close-up-slow-motion-footage.mp4',
        type: 'video/mp4'
      },
      {
        src: 'night.webm',
        type: 'video/webm;codecs="vp8, vorbis"'
      }
    ],

    // 一旦视频加载后即将视频封面隐藏
    onLoad: function () {
      document.querySelector('#video_cover').style.display = 'none';
    }
  });
}());