DVD Definition and Detailed Information

Part 1: What is DVD

DVD stands for Digital Versatile Disc or Digital Video Disc and was developed jointly by Philips, Sony, Toshiba and Panasonic in early 1990s. It's a kind of digital optical disc storage format with a higher resolution pictures and sound than VHS. Also, DVD offers a larger storage capacity over compact discs (CD) and can be used to store video, audio, and other data like documents, pictures, programs, etc. DVD has several disc types including DVD-R/RW, DVD+R/RW, DVD-RAM, and DVD ROM. Commercial DVDs employ encryption methods in order to protect contents from copying without authorizing. So it'll be pretty hard to rip DVD to computer.

DVD

Part 2: DVD Specifications

There are multiple DVD format types in use nowadays. Among them DVD-5 and DVD-9 are the most widely used DVD types.

DVD 5 VS DVD 9

DVD 5 adopts single-sided single-layer 12cm standard DVD disc with a capacity of 4.37 GiB / 4.7GB. DVD-5 is the most widely used DVD media.

DVD 9 uses single-sided dual-layer DVD disc with a size of 7.95 GiB / 8.5GB.

DVD Disc Types

DVD has various disc types, including DVD-R, DVD+R, DVD-RW, DVD+RW, DVD-RAM and DVD-ROM. The letter "R" refers to Recordable and can only be recorded once via DVD recorder. "RW" means Rewritable while "RAM" stands for Random Access Memory and these two kinds of discs can be recorded and erased many times. DVD-ROM (Read Only Memory) refers to the pre-recorded DVDs mass-produced by molding machines and can only be used for playing in DVD drive/players by customers.

DVD Resolution

The standard DVD has a resolution of 720*480 for NTSC and 720*576 for PAL.

Part 3: Structure of DVD

When accessing an internal or external DVD drive in a computer, you'll find 2 directories: AUDIO_TS and VIDEO_TS.

AUDIO_TS is used for storing DVD audio. The fact that this folder is always empty in a DVD Video disc doesn't mean there's no audio in the video. The directory only contains files on a DVD Audio disc.

VIDEO_TS is used for storing all data in the movie. Always there are two or more .IFO and .BUP files, and at least one VOB file in the folder. The BUP files are backup files of IFO files, which contain information like chapters, subtitles and audio tracks. And VOB files includes the video, audio, subtitle and menus of the DVD movie. The following is an example of DVD video structure:

DVD video structure

Part 4: Restrictions of DVD

DVD Encryption

Commercially produced DVDs employ a Digital Rights Management (DRM) mechanism and adopt several encryption methods to protect its content from copying without permission.

The Content Scramble System

The Content Scramble System (CSS) is an encryption of DVD Video. It prevents unauthorized copy of DVD MPEG stream videos. It makes sure only certified DVD Players can play CSS encrypted DVDs and contributes a lot to the protection of intellectual property right.

Content Protection for Prerecorded Media

Content Protection for Prerecorded Media (CPPM) is the encryption mechanism DVD Audio discs adopt.

DVD Region Codes

DVD releases are separated into several areas. And Global region codes identify DVDs can only be played in DVD Players sold in the specific area.

DVD Region Specifications

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