代码示例：（标识：bs_utility_aspect_ratio）
<!DOCTYPE html>
<html lang="en">
<head>
<title>Bootstrap Example</title>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<link href="https://cdn.bootcdn.net/ajax/libs/twitter-bootstrap/5.1.2/css/bootstrap.min.css" rel="stylesheet">
<script src="https://cdn.bootcdn.net/ajax/libs/twitter-bootstrap/5.1.2/js/bootstrap.bundle.js"></script>
</head>
<body>
<div class="p-4">
<h2>Aspect Ratio</h2>
<p>Create a responsive video and scale it nicely to the parent element.</p>
<h2>Aspect ratio 1:1</h2>
<div class="ratio ratio-1x1">
<iframe src="/static/demo/video/shanghai.mp4"></iframe>
</div>
<br>
<h2>Aspect ratio 4:3</h2>
<div class="ratio ratio-4x3">
<iframe src="/static/demo/video/shanghai.mp4"></iframe>
</div>
<br>
<h2>Aspect ratio 16:9</h2>
<div class="ratio ratio-16x9">
<iframe src="/static/demo/video/shanghai.mp4"></iframe>
</div>
<br>
<h2>Aspect ratio 21:9</h2>
<div class="ratio ratio-21x9">
<iframe src="/static/demo/video/shanghai.mp4"></iframe>
</div>
</div>
</body>
</html>
