I recently was wrestling with MediaSync on my side project to make a direct link generator for reddit videos. For those who don't know, reddit videos (https://v.redd.it/8ac6uk4bbxg51) play in reddit's custom video player. After some digging, it turns out that reddit hosts the audio and video streams separately and syncs them together on the client side. I eventually was able to implement media sync (though it doesn't cover all cases), and have tremendous respect for those trying to solve the same problem.
Here is a demo of my media sync implementation - https://vreddit.vercel.app/?vid=8ac6uk4bbxg51&q=2