Xv format is a virtual format unique to Thunder, that is, cache file. When you watch it again with Thunder, you can watch it without buffering. This is the only advantage. You can't watch it offline because this video is digitally signed. If you want to play, you need to look it up online, let alone convert it into RMVB. This is what Thunder said about copyright protection.

It is not recommended to download such files. Go to the dog and search for the BT seed of the movie or TV series you want, or download it directly.

If not, just know to post and ask who has the seeds.