DVD-Video is a consumer video format used to store digital video on DVD (DVD-ROM) discs, and is currently the dominant form of consumer video formats in the United States, Canada, Europe and Australia. Discs using the DVD-Video specification require a DVD drive and an MPEG-2 decoder (e.g., 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 audio of varying formats (often multi-channel formats as described below). Typical data rates for DVD movies range from 3–10 Mbit/s, and the bit rate is usually adaptive.
The following formats are allowed for MPEG-2 video:
The following formats are allowed for MPEG-1 video:
DVD-Video discs have a raw bitrate of 11.08 Mbit/s, with a 1.0 Mbit/s overhead, leaving a payload bitrate of 10.08 Mbit/s. Of this, up to 3.36 megabits can be used for subtitles and a maximum of 9.80 megabits can be split amongst audio and video. In the case of multiple angles the data is stored interleaved, and so there's a bitrate penalty leading to a max bitrate of 8Mbit/s per angle to compensate for additional seek time. This limit is not cumulative, so each additional angle can still have up to 8Mbit/s of bitrate available.
Professionally encoded videos average a bitrate of 4.0-5.0 Mbit/s with a maximum of 7–8 Mbit/s in high-action scenes. This is typically done to allow greater compatibility amongst players, and to help prevent buffer underruns in the case of dirty or scratched discs.
Columbia TriStar Home Entertainment has created a line of DVDs (dubbed "Superbit") aiming to maximize picture quality by eliminating multiple languages, angles, and audio tracks. This allows average bitrates closer to 6 Mbit/s.
Some DVD hardware or software players may play discs whose MPEG files do not conform to the above standards; commonly this is used to support DVD discs authored with formats such as VCD and SVCD. While VCD and CVD video is supported by the DVD standard, neither SVCD video nor VCD, CVD, or SVCD audio is compatible with the DVD standard.
Some hardware players will also play DVD-ROMs or CD-ROMs containing "raw" .mpg MPEG video files; these are "unauthored" and lack the file and header structure that defines DVD-Video. Standard DVD-Video files contain extra information (such as the number of video tracks, chapters and links to extra features) that DVD players use to navigate the disc.
The audio data on a DVD movie can be PCM, DTS, MPEG-1 Audio Layer II (MP2), or Dolby Digital (AC-3) format. In countries using the PAL system standard DVD-Video releases must contain at least one audio track using the PCM, MP2, or AC-3 format, and all standard PAL players must support all three of these formats. A similar standard exists in countries using the NTSC system, though with no requirement mandating the use of or support for the MP2 format. DTS audio is optional for all players, as DTS was not part of the initial draft standard and was added later; thus, many early players are unable to play DTS audio tracks. The vast majority of commercial DVD-Video releases today employ AC-3 audio. The official allowed formats for the audio tracks on a DVD Video are:
DVDs can contain more than one channel of audio to go together with the video content, supporting a maximum of 8 simultaneous audio tracks per video. This is most commonly used for different audio formats—DTS 5.1, AC-3 2.0 etc.—as well as for commentary and audio tracks in different languages.
Video is another issue which continues to present most problems. Current players typically output analog video only, 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, to carry a form of component video, which keeps the three components of the video, one luminance signal and two color difference signal, as stored on the DVD itself, on fully separate wires (whereas S-Video uses two wires, uniting and degrading the two color signals, and composite only one, uniting and degrading all three signals). The connectors are further confused by using a number of different physical connectors on different player models, RCA or BNC, as well as using VGA cables in a non-standard way (VGA is normally analog RGB—a different, incompatible form of component video). Even worse, there are often two sets of component outputs, one carrying interlaced video, and the other progressive.
In Europe (but not most other PAL areas), SCART connectors are typically used, which can carry composite, Y/C (S-Video) and/or analog RGB interlaced video signals (RGB can be progressive, but not all DVD players and displays support this mode), as well as analog two-channel sound on a single convenient multiwire cable. The analog RGB component signal offers video quality which is superior to S-Video and identical to YPbPr component video. However, analog RGB and S-Video signals can not be carried simultaneously, due to each using the same pins for different uses, and displays often must be manually configured as to the input signal, since no switching mode exists for S-Video. (A switching mode does exist to indicate whether composite or RGB is being used.) Some DVD players and set-top boxes offer YPbPr component video signals over the wires in the SCART connector intended for RGB, though this violates the official specification and manual configuration is again necessary. (Hypothetically, unlike RGB component, YPbPr component signals and S-Video Y/C signals could both be sent over the wire simultaneously, since they share the luminance (Y) component.)
HDMI is a new digital connection similar to DVI; it carries High Definition, Enhanced Definition and Standard Definition video. Along with video HDMI also supports up to eight-channel digital audio. Some HDMI-equipped DVD players can upconvert the video to higher definition formats such as 720p and, to a lesser extent, 1080p.
The extra (or bonus) features are often popular with the audience as they add extra depth and understanding to the film. Games, bloopers and galleries provide extra entertainment, especially for younger ages. Deleted scenes and alternative endings further the imagination and allow the audience to form a personal judgement on whether the best scenes were selected.
Other extras that can be included on DVDs are motion menus, still pictures, up to 32 selectable subtitles, seamless branching for multiple storylines, up to 9 camera angles, and DVD-ROM / data files that can be accessed on a computer equipped with a DVD-ROM capable drive...
CSS does not make it more difficult to copy the digital content, nor possible to distinguish between legal and illegal copies of a work, but it does restrict the playback software that may be used.
CSS has caused major problems for the inclusion of DVD players in any open source operating systems, since open source player implementations are not officially given access to the decryption keys or license to the patents involved in CSS. Proprietary software players were also difficult to find on some platforms. However, a 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 controversial U.S. Digital Millennium Copyright Act (DMCA), on the grounds that such software could also be used to facilitate unauthorized copying of the data on the discs.
The DMCA currently affects only the United States, however many other countries are signatories to the similar WIPO Treaty. In some countries it is not illegal to use de-scrambling software to bypass the DVD restrictions. A number of software programs have since appeared on the Web to view DVDs on a number of different platforms.
Other measures such as anti-ripping, as well as U.S. and non-U.S. copyright law, may be used to prevent making unauthorized copies of DVDs. CSS decrypting software, or ripping software, such as DVD Decrypter, AnyDVD, and DVD Shrink allows a disc to be copied to hard disk unscrambled. Some DeCSS applications also remove Macrovision, region codes, and disabled user operations (UOPs).
Each DVD-Video disc contains one or more region codes, denoting the area(s) of the world in which distribution and playback are intended. The commercial DVD player specification dictates that a player must only play discs that contain its region code. In theory, this allows the motion picture studios to control the various aspects of a release (including content, date and price) on a region-by-region basis, or ensure the success of "staggered" or late theatrical releases from country to country. For example, the British movie 28 Days Later was released on DVD in Europe several months prior to the film's theatrical release in North America. Regional coding kept the European DVD unplayable for most North American consumers, thereby ensuring that ticket sales would be relatively unaffected by the late theatrical release.
In practice, many DVD players allow playback of any disc, or can be modified to do so. Entirely independent of encryption, region coding pertains to regional lockout, which originated in the video game industry.
From a worldwide perspective regional coding may be seen as a failure. A huge percentage of players outside of North America can be easily modified (and are even sold pre-modified by mainstream stores such as Amazon.co.uk) to ignore the regional codes on a disc. This, coupled with the fact that almost all televisions in Europe and Australasia are capable of displaying NTSC video, means that consumers in these regions have a huge choice of discs. Contrary to popular belief, this practice is not illegal and in some countries that strongly support free trade it is encouraged.
A normal DVD player can only play region-coded discs designated for the player's own particular region. However, a code-free or region-free DVD player is capable of playing DVD discs from any of the six regions around the world.
The CSS license prohibits manufacturing of DVD players that are not set to a single region by default. While the same license prohibits manufacturers from including prominent interfaces to change the region setting it does not clearly prevent them from including "hidden" menus that enable the player's region to be changed; as such, many high-end models in the U.S. include password-protected or otherwise hidden methods to enable multi-region playback. Conversely in the UK and Ireland many cheap DVD players are multi-region while more expensive systems, including the majority of home cinema systems, are preset to play only region 2 discs.
DVD drives for computers usually come with one of two kinds of Regional Playback Control (RPC), either RPC-1 or RPC-2. This is used to enforce the publisher's restrictions on what regions of the world the DVD can be played. (See Regional lockout and DVD region codes.) Most DVD players (both standalone models and software players) come further encumbered with restrictions forbidding the viewer from skipping (or in some cases fast-forwarding) certain content such as copyright warnings or advertisements. (See User operation prohibition.)
Video game systems with DVD-Video playback functionality are PlayStation 2, PlayStation 3, Xbox (additional remote required), Xbox 360, and Panasonic Q. Nintendo's console, the Wii, does not currently have DVD-Video playback functionality, but it was rumored that a new, DVD-Video capable, revision of the console was forthcoming. An interview with Reggie Fils-Aime where he points out that a future version of the Wii will be able to play DVD-Video confirmed this rumor.
On November 18, 2003, the Chinese news agency Xinhua reported the final standard of the Chinese government-sponsored Enhanced Versatile Disc (EVD) which is another extension of standard DVD. Shortly thereafter the development of the format was halted by a licensing dispute between Chinese companies and On2 Technologies, but on December 6, 2006, 20 Chinese electronic firms unveiled 54 prototype EVD players and announced their intention for the format to completely replace DVDs in China by 2008. However, due to a lack of sales, support for EVD has recently been dropped by the Xinhua Bookstore in Wuhan, which was a major supporter of the format.
The first serious contenders to replace DVD were HD DVD and Blu-ray. HD DVD was backed by the DVD Forum which voted to make it the official successor to DVD. Blu-ray is backed by the Blu-ray Disc Association which shares many of the same members. The first HD DVD player was released in March 2006, with the first Blu-ray player following in June 2006. They were engaged in a format war up until February 2008, to determine which of the two formats will become the leading carrier for high-definition content to consumers. This situation was similar to the VHS/Betamax format war in consumer video recorders in the late 1980s. The manufacturers of HD DVD, Toshiba, announced in February 2008 that they were ceasing production of their HD DVD players indefinitely, citing low demand for HD DVD and the growing use of Blu-ray, which had become popular due to its inclusion as part of the PlayStation 3 among other things.
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