JavaScript code:

// ==UserScript==
// @name        Fix videos better - somethingawful.com
// @namespace   https://forums.somethingawful.com/
// @match       https://forums.somethingawful.com/*
// @version     0.2
// @author      Wheany, BlankSystemDaemon
// @description Sets embedded video size caps, auto-enables controls, embeds webms, sets volume to 20%, and prevents videos from looping. Last edited: 6/19/2023, 15:00:42 UTC
// ==/UserScript==


function processVideos() {
	[...document.getElementsByTagName('video')].forEach((v) => {
		v.removeAttribute('loop');
		v.pause();
		Object.assign(v, {
			currentTime: 0,
            		controls: true,
			volume: 0.2,
			muted: false
		});
		Object.assign(v.style, {
			maxWidth: '100%',
			maxHeight: '500px'
		});
	})
}

// required for dynamic webapp pages that modify the page with javascript
const observer = new MutationObserver(processVideos);
observer.observe(document.body, {
	childList: true,
	subtree: true
});

// handles simple pages like SA forums where the page structure doesn't change dynamically after being loaded
if(document.readyState === "interactive") {
	processVideos();
} else {
	document.addEventListener('DOMContentLoaded', processVideos);
}