Files in VOB format have a .vob filename extension and are typically stored in the VIDEO_TS directory at the root of a DVD.
In addition, a VOB file can contain linear PCM, AC-3 or DTS audio and subpictures (subtitles).
[7][9][10] VOB files cannot contain AAC audio (MPEG-2 Part 7), MPEG-4 compression formats and others, which are allowed in the MPEG program stream standard.
Almost all commercially produced DVD-Video titles use some restriction or copy protection method, which also affects VOB files.
If the copied undecrypted VOB files are opened in a player, they will request the keys from the DVD-ROM drive and will fail.
[14][15] There are many CSS-decrypting programs, or ripping software, such as libdvdcss, DeCSS, DVD Decrypter, AnyDVD or DVD Shrink which allow a protected DVD-Video disc to be played without access to the original key or copied to hard disk unscrambled.
Some DVD Recorders use DVD-VR format and store multiplexed audiovisual content in VRO containers.