DVD authoring requires an extensive knowledge of the internal composition of DVD video and audio files. Unlike digital video files that can be played on your computer with a series of codecs and digital media players, DVDs use a standardized set of already rendered file types, called Video Title Sets, that can be identified on any DVD player.
The VTS_xx_0.IFO files are used to provide the basic operating and playback functions of your DVDs. Without these files, playback of DVDs on your DVD player would be impossible. The VTS_xx_0.IFO files determine the order in which root menus load and include the video codec for your DVD. The "xx" in the filename may include any number from one to 99 depending on the number of files on the disc. The contents of these files are duplicated on the VTS_xx_0.BUP files. In the event that a file is corrupted or damaged, your DVD player will defer to the .BUP file to load your DVD.
The VTS_xx_0.VOB files contain the root menus and other disc menus contained on your DVD. These files provide the the code for the internal navigation within your DVDs. While these files are not required on DVDs, those without these files will not have the ability to skip chapters during playback or select an alternative starting point for playback. The "xx" in these files can also range from one to 99, depending on the amount of files on the disc.
The actual video files are contained in the VTS_xx_n.VOB files. These files include the main movie, any bonus features and alternate video footage located on the disc. These files may also include multiple audio tracks and subtitle information for each track. When you back up or extract video information from a DVD, these VOB files what you will need to locate.
Using .VTS Files
Each VTS file type has a purpose in the final composition of the DVD. DVD authoring software will create these file types automatically when creating DVDs of your home movie projects. DVD ripping and copying software looks for each of these file types to copy and back up your DVD collection. Some ripping software will use the VTS_xx_n.VOB files and convert them to MPEG-2 or AVI file types.