DVD-Video
DVD-Video discs require a DVD-drive with a MPEG-2 decoder (eg. a DVD-player or a DVD computer drive with a software DVD player). Commercial DVD movies are encoded using a combination of MPEG-2 compressed video and Dolby Digital audio (often in multi-channel formats.) Typical data rates for DVD movies range from 3-10 Mbit/s, and the bitrate is usually adaptive.
The audio data on a DVD movie can be of the format PCM, DTS, MPEG audio, or Dolby Digital (AC-3). In countries using the NTSC standard any movie should contain a sound track in PCM or Dolby AC-3 format, and any NTSC player must support these two, all the others are optional. This ensures any standard compatible disc can be played on any standard compatible player.
Initially, in countries using the PAL standard (most of Europe) the sound of DVD was supposed to be standardized on PCM and MPEG-2 audio, but apparently against the wishes of Philips, under public pressure on December 5, 1997, the DVD Forum accepted the addition of Dolby AC-3 to the optional formats on discs and mandatory formats in players.
With several channels of audio from the DVD, the cabling needed to carry the signal to an amplifier or TV can occasionally be somewhat frustrating. Most systems include an optional digital connector for this task, which is then paired with a similar input on the amplifier. The selected audio signal is sent over the connection, typically over RCA jacks or TOSLINK, in its original format to be decoded by the audio equipment. When playing compact discs, the signal is sent in S/PDIF format instead.
Video is another issue which continues to present problems. Current systems typically include both composite video on an RCA jack, as well as S-Video in the standard connector. However neither of these connectors were intended to be used for progressive video, so yet another set of connectors has started to appear in the form of component video, which fully separates the signal into its three components (whereas s-video has two, and composite only one). Additionally, the connectors are further confused by using a number of physical connectors, RCA or BNC, as well as using VGA cables in a non-standard way (VGA is normally RGB). Even worse, there are often two sets of component outputs, one carrying interlaced video, and the other progressive.
DVD Video may also include subtitles in various languages. They are stored as images with transparent background.
DVD Video may contain Chapters for easy navigation (and continuation of a partially watched film).
A major selling point of DVD Video is that its storage capacity allows for a wide variety of extra features in addition to the feature film itself. This can include audio commentary that is timed to the film sequence, documentary features, unused footage, trivia text commentary, games and film shorts.
Security
Most DVD-Video titles use Content Scrambling System (CSS) encryption, which is intended to discourage people from making perfect digital copies to another medium or from bypassing the region control mechanism (see below). Discs can also specify that the player use Macrovision, an analog anti-copying mechanism that prevents the consumer from copying the video onto a VCR tape. This alone would not prevent the duplication of DVD discs in their entirety without decrypting the data, given suitable equipment, although "consumer-grade" DVD writers deny this ability by refusing to duplicate the tracks on the disc which contain the decryption keys.
The CSS system has caused problems for the inclusion of DVD players in strictly open source operating systems, since open source player implementations can not officially obtain access to the decryption keys or license the patents involved in the CSS system. Proprietary software players may also be difficult to find on some platforms. However at least one successful effort has been made to write a decoder by reverse engineering, resulting in DeCSS. This has led to long-running legal battles and the arrest of some of those involved in creating or distributing the DeCSS code, through the use of the U.S. Digital Millennium Copyright Act, on the grounds that such software could also be used to facilitate unauthorized copying of the data on the discs.
Region codes
DVD movies can contain a region code, denoting which area of the world it is targeted at, which is completely independent of encryption. The commercial DVD-video player specification dictates that players must only play discs that contain their region code. This allows the film studios to set different retail prices in different markets and extract the maximum possible price from consumers. With region coding, studios can dictate release schedules and prices around the world. However, many DVD players allow playback of any disc, or can be modified to do so. Region coding pertains to regional lockout, which originated from the video game industry.
CD and DVD release of 