Go to VIDEO_TS, this directory contains 3 types of files: .vob files, .ifo files, and .bup files. .vob files are used to save all MPEG-2 format audio and video data, which contain not only the movie itself, but also screens for menus and buttons, and sub-screen streams for multiple subtitles. .ifo files are used to control the playback of VOB files, information on how to control the playback of data in .vob files can be found in this file. Because .ifo files are critical to proper playback of the disc, copies of all .ifo files are saved as .bup files with the same name. There is a Video Manager (VMG) on each DVD disc, which is stored in the VIDEO_TS.ifo file and holds global information about the disc, such as the playback area of ??the disc. The disc also saves the data used to display the menu in the VIDEO_TS.vob file, which the player displays first when the disc is inserted into the CD-ROM drive. Most menus allow viewers to specify scenes, select subtitle language, etc.
Vob and IFO can be opened with PowerDVD software, but BUP files cannot be opened, and it is supposed to be a DVD video disc system
Use Format Factory to convert it to the format you want. rmvb or mp4 you want