不幸的是，Chrome不支持对视频html 5标签的媒体查询。解决这个问题的一个方法是使用普通的Javascript或Jquery。它不漂亮，但即使在Chrome中也能工作。

var video = $('#myvideo');

var WindowWidth = $(window).width();

if (WindowWidth < 1200) {
    //It is a small screen
    video.append("<source src='/img/homepage/640/splash.m4v' type='video/mp4' >");
} else {
    //It is a big screen or desktop
    video.append("<source src='/img/homepage/1080/uimain-1080.mp4' type='video/mp4' >");
}

我在Vanilla JS上的实现。
在video标签中，指定默认视频的路径作为data-src属性，在video标签中，在source标签中，指定data-src和data-mw两个属性的值。
data-src-是视频文件的路径。
data-mw-显示此视频的最大屏幕宽度。
当屏幕宽度改变时，此解决方案会自动工作。这是通过resize()函数完成的。

<video id="intro-video" data-src="/path/default.mp4" poster="img/poster.png" controls>
    <source data-src="/path/1600.mp4" data-mw="1600">
    <source data-src="/path/900.mp4" data-mw="900">
    <source data-src="/path/480.mp4" data-mw="480">
</video>

class VideoResponser {
    constructor(selector) {
        const $video = document.querySelector(selector);
        this.options = { 
            selector, 
            breakpoints: { default: { src: $video.getAttribute('data-src') } } 
        };

        // get a list of video switching points and links to the videos themselves 
        $video.querySelectorAll('[data-src]').forEach(element => this.options.breakpoints[element.getAttribute('data-mw')] = { src: element.getAttribute('data-src') });
        $video.innerHTML = ''; // we clean up so that there is nothing superfluous 
        
        // run the handler and track the change in screen width
        this.responseVideo(this.options);
        this.resizer();
    }

    /** Function runs on resize  */
    resizer() {
        window.addEventListener("resize", () => this.responseVideo(this.options));
    }

    /** 
     * Change src value of video link to fit screen width 
     * 
     * @param {Object} options object with options 
     */
    responseVideo(options) {
        const {selector, breakpoints} = options; // get options
        let $video = document.querySelector(selector);
        const widthNow = $video.getAttribute('data-width-now') || null;
        const maxBreakpoint = Math.max.apply(Math, Object.keys(breakpoints).filter(key => key <= document.body.clientWidth).map(Number));
        const nowBreakpoint = maxBreakpoint || 'default'; // choose either the maximum value, if not, then the default 

        if(widthNow && widthNow == nowBreakpoint) return; // check if the video needs to be changed 

        $video.setAttribute('data-width-now', nowBreakpoint);
        $video.src = breakpoints[nowBreakpoint].src;
    }
}

new VideoResponser("#intro-video");

<video class="desktop-video" autoplay playsinline preload="auto" muted loop width="100%">
    <source src="${pdict.desktop_video}" type="video/mp4">
    <source src="${pdict.desktop_video}" type="video/mov">
    Sorry, your browser doesn't support embedded videos.
</video>
<video class="mobile-video" autoplay playsinline preload="auto" muted loop width="100%">
    <source src="${pdict.mobile_video}" type="video/mp4">
    <source src="${pdict.mobile_video}" type="video/mov">
    Sorry, your browser doesn't support embedded videos.
</video>

可以在CSS中完成

.desktop-video {
    display: grid;

    @include media-breakpoint-down(lg) {
        display: none;
    }
}

.mobile-video {
    display: none;

    @include media-breakpoint-down(lg) {
        display: grid;
    }
}

我的解决方案显示不同的视频取决于屏幕大小：

<video autoplay="" loop="" muted="" preload="auto">
    <source src="/video/1920x1080.mp4" type="video/mp4" />
</video>

<script>
(function(){
  var w = window.innerWidth || document.documentElement.clientWidth || document.body.clientWidth;
  var h = window.innerHeight || document.documentElement.clientHeight || document.body.clientHeight;
  if (414 >= w && 916 >= h)
    document.querySelector("video source").setAttribute('src', '/video/414x916.mp4');
  else if (1280 >= w && 720 >= h)
    document.querySelector("video source").setAttribute('src', '/video/1280x720.mp4');
})();</script>

我使用了object-fit: cover;的解决方案

.video-wrapper {
    position: relative;
    max-width: 100%;
    height: auto;
    overflow: hidden;
    margin-bottom: 0;
    padding-top: 100%;
}

@media (min-width: 768px) {
        .video-wrapper {
                padding-top: 50%;
        }
    }

.video-item {
    position: absolute;
    top: 0;
    left: 0;
    height: 100%;
    width: 100%;
    object-fit: cover;
}

编码笔here