The VOB files contain the body of the movie if you will. The data contains both video, audio as well as subtitle information data streams - all interleaved together. All video by standard, is compressed MPEG-2, while the standard audio format is normally AC3 (also known as Dolby Digital). AC3 streams may have a bit-rates between 192 and 448kbit/sec. 192kbit/sec is used for standard 2 channel stereo, while 384-448kbit/sec is used for 5.1channel surround sound.
A VOB contains one primary video stream but may also contain several multi-angle streams for example, thus allowing the selection of different perspectives. The only limitation, is that the maximum bit-rate of the video streams is 9.8mbits/sec while combined video & audio must always be below 10 mbits/sec. Up to 9 different audio streams and up to 32 different subtitle streams are also supported.
Also, any single VOB file must never be greater than 1 GB in size for compatibility with set top players (The 1 GB max file size is not a hardware limitation, but rather is the maximum agreed on VOB file size set forth by the DVD standards committee). Thus many movies may contain & span several VOB's - as a single 1gb VOB file will hold only approximately 27 minutes of material if recorded in the SP mode. VOB files larger than 1gb may play ok on your computer, but playback on most standalone players is doubtful.
VOB Files are further broken down by their purpose and how structured by the authoring software.
For example: The VIDEO_TS.VOB files contain the initial DVD opening "splash" screen and menu options. The large VOB files are normally those containing the body of the program.
A DVD may have multiple chapters: Each chapter is designated by a file name of VTS_X. Thus Chapter 1 would be in VTS_01_0.VOB, Chapter 2 in VTS_02_0.VOB etc etc..... The VTS_01_0.VOB and the VTS_01_1.VOB files for example, contain the audio/video that will play for the first chapter.
