Hello, I've made the movie watching world inside VRChat. Here's the link and overview.
https://vrchat.com/home/world/wrld_583ae9b6-e8f5-4806-a560-2b19782a1f83
It has audiolink and capable of 7.1 and 5.1 surround sound, Dolby Atmos 5.1.2, and normal Youtube video, VRCDN also support.
Some rant
VideoTXL and any other video players inside VRChat use AVpro, which rely on Windows Media Foundation. If you were asking what format it supports from the official documentaion, You'll find that it's kinda disappointing as windows didn't update their media component since Windows 7, and rely on Media extention plugin for newer codecs.