如何为具有视频背景的移动设备添加背景图像？

Question

所以我为网站制作了这个视频背景。现在我真的不知道如何转换CSS，因此它为平板电脑和移动设备提供背景图像而不是视频。 我希望有人能帮助我解决这个问题。

提前致谢。

$( document ).ready(function() {

    // Resive video
    scaleVideoContainer();

    initBannerVideoSize('.video-container .poster img');
    initBannerVideoSize('.video-container .filter');
    initBannerVideoSize('.video-container video');
        
    $(window).on('resize', function() {
        scaleVideoContainer();
        scaleBannerVideoSize('.video-container .poster img');
        scaleBannerVideoSize('.video-container .filter');
        scaleBannerVideoSize('.video-container video');
    });

});

/** Reusable Functions **/
/********************************************************************/

function scaleVideoContainer() {

    var height = $(window).height();
    var unitHeight = parseInt(height) + 'px';
    $('.homepage-hero-module').css('height',unitHeight);

}

function initBannerVideoSize(element){
    
    $(element).each(function(){
        $(this).data('height', $(this).height());
        $(this).data('width', $(this).width());
    });

    scaleBannerVideoSize(element);

}

function scaleBannerVideoSize(element){

    var windowWidth = $(window).width(),
        windowHeight = $(window).height(),
        videoWidth,
        videoHeight;
    
    console.log(windowHeight);

    $(element).each(function(){
        var videoAspectRatio = $(this).data('height')/$(this).data('width'),
            windowAspectRatio = windowHeight/windowWidth;

        if (videoAspectRatio > windowAspectRatio) {
            videoWidth = windowWidth;
            videoHeight = videoWidth * videoAspectRatio;
            $(this).css({'top' : -(videoHeight - windowHeight) / 2 + 'px', 'margin-left' : 0});
        } else {
            videoHeight = windowHeight;
            videoWidth = videoHeight / videoAspectRatio;
            $(this).css({'margin-top' : 0, 'margin-left' : -(videoWidth - windowWidth) / 2 + 'px'});
        }

        $(this).width(videoWidth).height(videoHeight);

        $('.homepage-hero-module .video-container video').addClass('fadeIn animated');
        

    });
}

.homepage-hero-module {
  border-right: none;
  border-left: none;
  position: relative;
}
.no-video .video-container video,
.touch .video-container video {
  display: none;
}
.no-video .video-container .poster,
.touch .video-container .poster {
  display: block !important;
}
.video-container {
  position: relative;
  bottom: 0%;
  left: 0%;
  height: 100%;
  width: 100%;
  overflow: hidden;
  background: #000;
}
.video-container .poster img {
  width: 100%;
  bottom: 0;
  position: absolute;
}

.video-container .title-container {
  z-index: 1000;
  position: absolute;
  top: 35%;
  width: 100%;
  text-align: center;
  color: #fff;
}
.video-container .description .inner {
  font-size: 1em;
  width: 45%;
  margin: 0 auto;
}
.video-container .link {
  position: absolute;
  bottom: 3em;
  width: 100%;
  text-align: center;
  z-index: 1001;
  font-size: 2em;
  color: #fff;
}
.video-container .link a {
  color: #fff;
}
.video-container video {
  position: absolute;
  z-index: 0;
  bottom: 0;
  object-fit: cover;
}
.video-container video.fillWidth {
  width: 100%;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<section id="intro" class="parallax-section">
<!-- Main jumbotron for a primary marketing message or call to action -->
<div class="homepage-hero-module">
    <div class="video-container">
        <div class="title-container">
            <div class="headline">
                	<h1>Welcome to our Company</h1>

            </div>
            <div class="description">
                <div class="inner">Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s</div>
            </div>
        </div>
        <div class="filter"></div>
        <video autoplay class="fillWidth">
            <source src="http://video.blendertestbuilds.de/download.blender.org/peach/trailer_480p.mov" type="video/mp4" autoplay loop muted />Your browser does not support the video tag. I suggest you upgrade your browser.
           <source src="http://video.webmfiles.org/big-buck-bunny_trailer.webm" type="video/webm"  autoplay loop muted />Your browser does not support the video tag. I suggest you upgrade your browser.
            </video>
        <div class="poster hidden">
            <img src="images/background.jpg" alt="">
        </div>
    </div>
</div>
<div class="container" id="content">
    <!-- adding this soon -->
    </div>
</section>