VOB is short for DVD Video Object. It is a container file format. It is an important file type used in DVD video disc. There are three types of files in a DVD disc: IFO(.ifo), VOB(.vob) and BUP(.bup). Video and audio data of a DVD disc stores in VOB files. IFO (Info) files contain all the information a DVD player needs to know about a DVD so that the user can navigate and play all DVD content properly. BUP (Backup) files are an exact copy and backup of IFO files in case of corruption.
So VOB files are the movie files, which form the main content of a DVD disc. IFO files are very important for a DVD disc as they contain the navigation and playback content of the disc. So IFO files need backup copies, which are BUP files.
VOB file usually contain multiplexed Dolby Digital audio and MPEG-2 video. It also can contain subtitle, menu and navigation contents, which are multiplexed with the video and audio data. According to Wikipedia, VOB is based on the MPEG program stream format, but with additional limitations and specifications in the private streams. Analogous to the MPEG program stream, VOB file can contain H.262/MPEG-2 Part 2 or MPEG-1 Part 2 video, MPEG-1 Audio Layer II or MPEG-2 Audio Layer II audio. In addition, VOB can contain Linear PCM, AC-3 or DTS audio and subpictures (subtitles). VOB file cannot contain AAC audio (MPEG-2 Part 7), MPEG-4 compression formats and others, which are allowed in MPEG program stream standard.
We know that in most cases we can't copy the movie from DVD disc directly to hard drive, as it's forbidden and illegal. If someone is trying to do this, he or she will get an error and the copying will automatically fail. Why? Because files in DVD disc are encrypted with Content Scramble System (CSS), which is is a data encryption and communications *********ation method designed to prevent copying video and audio data directly from the DVD-Video discs. There are many CSS-decrypting programs, or ripping software out there on the Internet, I will recommend Leawo DVD Ripper, which is a professional DVD to Video converter for you to rip, backup, edit and convert DVD to video in variety of formats.
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