are encrypted with Content Scramble System (CSS). This is a data encryption and communications authentication method designed to prevent copying video and audio data directly from the DVD-Video discs. Decryption and authentication keys needed for playing back encrypted VOB files are stored in the normally inaccessible lead-in area of the DVD and are used only by CSS decryption software (e.g., in a DVD player or software player). If someone is trying to copy the contents of an encrypted DVD-Video (e.g., VOB files) to a hard drive, an error can occur, because the DVD was not authenticated in the drive by CSS decryption software. Authentication of the disc allows the copying of individual VOB files without error, but the encryption keys will not be copied. If the copied undecrypted VOB files are opened in a player, they will request the keys from the DVD-ROM drive and will fail. 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. In some countries, their usage can be a violation of law (e.g. for non-personal use). Playback A player of generic MPEG-2 files can usually play unencrypted VOB files, which contain MPEG-1 Audio Layer II audio. Other audio compression formats such as AC-3 or DTS are less widely supported. KMPlayer, VLC media player, GOM player, Media Player Classic and more platform-specific players like ALLPlayer play VOB files. Other DVD containers Some DVD Recorders use DVD-VR format and store multiplexed audiovisual content in VRO containers. A VRO file is equivalent to a collection of DVD-Video VOB files. The VRO files can be played directly like a VOB if no editing is intended. Fragmented VRO files are not widely supported by software players and video editing software. Enhanced VOB (EVO) is also an extension to VOB, originally meant for the now-discontinued HD DVD video. It can contain additional video and audio formats such H.264 and AAC. See also Comparison of video container formats List of video editing software References External links doom9.org - What is on a DVD? DVD Digital container formats Filename extensions