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DVD (also known as "Digital Versatile Disc" or "Digital Video Disc") is an optical disc storage media format that can be used for data storage, including movies with high video and sound quality. DVDs resemble compact discs as their physical dimensions are the same (120 mm (4.72 inches) or occasionally 80 mm (3.15 inches) in diameter) but they are encoded in a different format and at a much higher density. The official DVD specification is maintained by the DVD Forum.
History
Format in video game consoles The Dreamcast, the first of the then "next generation" 128-bit video games consoles, was released by Sega in Japan in 1998, and in the U.S. and Europe in 1999. It did not play DVDs, which were still quite new and expensive and relatively unpopular at the time. Instead, it used a proprietary 1 Gb 4.75 inch disc known as a GD-ROM disc. By 2000, DVDs were getting more popular and a redesign was called in to add DVD capabilities. Instead, a free DVD player was offered with the machine in some regions, including Europe and Japan. In 2000, Sony released its PlayStation 2 (PS2) console in Japan. In addition to playing Video Games developed for the system, it was also able to play DVD movies. This proved to be a huge selling point and helped boost DVD sales, as the PS2 cost less than most DVD players in Japan. As a result, many electronic stores that normally did not carry video game consoles carried PS2s. Despite many reports of poor and bad playback and green screens, this proved popular and was often used as a primary DVD player until the prices of good standalone players went down. In keeping with this approach, Sony will incorporate Sony's competing successor to DVD, Blu-ray, into its next console, the PlayStation 3. Problems with implementing this and its Digital Rights Management are the official reason for the delay in launching the system. Microsoft's Xbox, released in 2001 in the U.S. and on March 13 2002 in Europe, had the capability to play DVD discs with an add-on remote control kit, cementing DVD's place in video game consoles. Nintendo's GameCube, released on May 3 2002 in Europe and on November 18 2001 in the US, cannot play DVDs but uses a proprietary 3-inch optical disc for its game media. However, a version of the GameCube known as the Panasonic Q (sold only in Japan) plays DVDs. With the Xbox 360, the successor to the Xbox, which was released worldwide in November 2005, DVD playback is built in. A HD-DVD Drive add-on is to be be released in late 2006 to play HD-DVD movies. There will be no games released in this format. DVD playback will be available on the upcoming PlayStation 3 as standard, but Nintendo's Wii console, which will use a proprietary 4.5 inch disc for its game media, has been confirmed to be incompatible with DVDs at launch. The Playstation 3 will launch in Japan and the U.S. in November 2006 and in Europe in March 2007, with the rest of the world to follow. DVD disc capacity Note: GB means here giga byte equal 109 (or 1,000,000,000) bytes. Many computers will displays gibibyte equal 230 (or 1,073,741,824) bytes. Example: Disc with 8.5 GB capacity will provide you: (8.5 x 1,000,000,000) / 1,073,741,824 ≈ 7.92 GiB. DVD recordable and rewriteable Main article: DVD recordable HP initially developed recordable DVD media from the need to store data for back-up and transport. DVD recordables are now also used for consumer audio and video recording. Three formats were developed: -R/RW (dash), +R/RW (plus), -RAM (random access memory). Dual layer recording Dual Layer recording allows DVD-R and DVD+R discs to store significantly more data, up to 8.5 Gigabytes per disc, compared with 4.7 Gigabytes for single-layer discs. DVD-R DL (dual layer — see figure) was developed for the DVD Forum by Pioneer Corporation, DVD+R DL (double layer — see figure) was developed for the DVD+RW Alliance by Sony. A Dual Layer disc differs from its usual DVD counterpart by employing a second physical layer within the disc itself; how the drive with Dual Layer capability accesses the second layer is that it could shine the laser through the first semi-transparent layer -- This is something that normal DVD recordable discs do not have. The layer change mechanism in some DVD players can show a noticeable pause, as long as two seconds by some accounts. More than a few viewers have worried that their dual layer discs were damaged or defective. DVD recordable discs supporting this technology are backward compatible with some existing DVD players and DVD-ROM drives. Many current DVD recorders support dual-layer technology, and the price point is comparable to that of single-layer drives, though the blank media remains significantly more expensive. DVD-Video DVD-Video discs 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 typical video resolution for an NTSC disc is 720 × 480, while a PAL disc is 720 × 576. The specifications for video files on a DVD can be any of the following: 720 × 576 pixels MPEG-2 (Called full D1) 704 × 576 pixels MPEG-2 352 × 576 pixels MPEG-2 (Called Half-D1, same as the China Video Disc standard) 352 × 288 pixels MPEG-2 352 × 288 pixels MPEG-1 (Same as the VCD Standard) 720 × 480 pixels MPEG-2 (Called full D1) 704 × 480 pixels MPEG-2 352 × 480 pixels MPEG-2 (Called Half-D1, same as the China Video Disc standard) 352 × 240 pixels MPEG-2 352 × 240 pixels MPEG-1 (Same as the VCD Standard) All MPEG video must be 25 frames per second on PAL DVDs. On NTSC DVDs MPEG-2 video can be either 29.97 frames per second or 23.976 frames per second, (with the player repeating frames via 3:2 pulldown to achieve NTSC's standard 29.97 frames per second) while MPEG-1 video can only be 29.97 frames per second. Interlacing is only supported for MPEG-2 video on both PAL and NTSC DVDs. 16:9 aspect ratio anamorphic video is only supported at 720x576/480, and all resolutions support 4:3 aspect ratio video. 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 MPEG video files; these are "unauthored" and lack the file and header structure that defines a DVD-video. (These files contain extra information, such as the number of video tracks, chapters and links to extra features, which DVD players use to navigate a DVD-video). A high number of audio tracks or a large amount of extra material on the disc will often result in a lower bit rate (and image quality) for the main feature. The total bitrate including video, audio and subtitles can be a maximum of 10.08 Mbit/s (10080 kbit/s). 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 or support for the MP2 format. 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 -- 5.1 DTS, 2.0 AC3, etc. -- as well as for commentary and audio tracks in different languages. 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 physical connection is typically RCA connectors or TOSLINK, which transmits a S/PDIF stream carrying either uncompressed digital audio (PCM) or the original compressed audio data (Dolby Digital (AC-3), DTS, MPEG audio) to be decoded by the audio equipment. Video is another issue which continues to most present 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, 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 (ignoring any conversion or noise issues). 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, more rarely, 1080p. DVD Video may also include up to 32 subtitle or subpicture tracks in various languages, including those made especially for the deaf and hearing impaired. They are stored as bitmap images with transparent background and are shown over the video during playback. The subtitle track is contained within the VOB file of the DVD. Subtitles are restricted to four colors (including transparency) and thus tend to look cruder than permanent subtitles on film. DVD Video may contain Chapters for easy navigation (and continuation of a partially watched film). If space permits, it is also possible to include several versions (called "angles") of certain scenes, though today this feature is mostly used—if at all—not to show different angles of the action, but as part of internationalization to e.g. show different language versions of images containing written text, if subtitles will not do (eg: the Queen's spell book in Snow White, and the scrolling text in the openings of the Star Wars films). Multiple angles have found a niche in markets such as yoga and erotica. 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, simple games and film shorts. Other extras that can be included on DVDs (extra to the main audio/visual programme) are motion menus, still pictures, up to 32 selectable subtitles, seamless branching for multiple storylines, 9 camera angles. And also additional DVD-ROM / data files that only can be read by computer DVD drives. Restrictions DVD-Video has four complementary systems designed to restrict the DVD user in various ways: Macrovision, Content Scramble System (CSS), region codes, and disabled user operations (UOPs). Content-scrambling system Many DVD-Video titles use content-scrambling system (CSS) encryption, which is intended to discourage people from copying the disc. Usually, users need to install software provided on the DVD or downloaded from the Internet such as WinDVD, PowerDVD, MPlayer, or VLC to be able to view the disc in a computer system. Without descrambling first, any digital copy of the disc will be ruined and unplayable everywhere, including computers. The 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 the patents involved in the 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, on the grounds that such software could also be used to facilitate unauthorized copying of the data on the discs. These laws currently affect only the United States; most other countries can 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 RipGuard, as well as US and international copyright law, may be used to prevent making unauthorized copies of DVDs. CSS decrypting software (such as DVD Decrypter, AnyDVD, and DVD Shrink) allows a disc to be copied to hard disk unscrambled and (as an extra feature) region-specific DVD to be copied as an all-region DVD. It also removes Macrovision, CSS, region codes, and disabled user operations (UOPs). Disabled user operations DVD-Video allows the disc to specify whether or not the user may perform any operation, such as selecting a menu, skipping chapters, forwarding or rewinding—essentially any function on the remote control. This is known as User Operation Prohibitions, or Prohibited User Operations (UOPs or PUOs). Most DVD players respect these commands (e.g. by preventing fast-forwarding through a copyright message or an advertisement at the beginning of a disc), although some can be configured to ignore them, particularly open-source player software. Many grey market players ignore UOPs. Many popular DVD "reauthoring" software packages allow the user to strip out UOPs, and burn a new copy without the restrictions. While this may be illegal in some countries, it is commonly argued in online forums that, having legally purchased the DVD and its content, users are ethically entitled to view 'their' content the way they prefer. See the fair use provision. Many feel that being forced to watch UOP-protected content, and having functions on their playback equipment disabled, is an unfair imposition by the distributor, particularly due to the fact that UOP-protected content is almost inevitably commercial content (previews and/or advertising of other films or products), meaning that they are forced to view commercials on what they have purchased. Furthermore, ironically a greater percentage of those who do not pirate DVDs are likely to see the UOP controlled anti-piracy warnings than those who do, as the aforementioned ability of authoring software to strip such restrictions ensures that pirated DVDs need not place restrictions on, or even display, such messages. Menu programming interface DVD players use special programming code to display special effects on the menus. It is unclear what programming language is used for this operation. However, some speculate that it may use machine language. As a result of a moderately flexible programming interface, educational DVD player games have been developed along with advanced trivia games such as Scene It; and even sophisticated games which use standard DVD players. Along with that, some console emulators may be released on DVD player images soon. Region codes Each DVD-Video disc contains one or more region codes, denoting the areas 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 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. To many, this is no more than an objectionable barrier to trade. As a result many websites offer methods with which consumers can by-pass such restrictions. 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 (New Zealand is one prominent example) 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. In the US, most low-cost DVD players that are sold in supermarkets or other cheap outlets are not multi-region. Some of the more expensive players (e.g. Sony) are multi-region. 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-Audio DVD-Audio is a format for delivering high-fidelity audio content on a DVD. It offers many channel configuration options (from mono to 5.1 surround sound) at various sampling frequencies and sample rates. Compared with the CD format, the much higher capacity DVD format enables the inclusion of either considerably more music (with respect to total running time and quantity of songs) or far higher audio quality (reflected by higher linear sampling rates and higher vertical bit-rates, and/or additional channels for spatial sound reproduction). Despite DVD-Audio's superior technical specifications, there is debate as to whether or not the resulting audio enhancements are distinguishable to typical human ears. DVD-Audio currently forms a niche market, probably due to its dependency upon new and relatively expensive equipment. Security DVD-Audio discs employ a robust copy prevention mechanism, called Content Protection for Prerecorded Media (CPPM) developed by the 4C group (IBM, Intel, Matsushita, and Toshiba). CPPM can be circumvented on a PC by capturing decoded audio streams in PCM format, but the underlying protection mechanism, encryption algorithms, and keys have not yet been cracked. Players and recorders Modern DVD recorders often support additional formats, including DVD+/-R/RW, CD-R/RW, MP3, WMA, SVCD, JPEG, PNG, SVG, KAR and MPEG-4 (DivX/XviD). Some also include USB ports or flash memory readers. Many players are priced from under $/€ 25 and recorders from $/€ 50. 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. Competitors and successors There are several possible successors to DVD being developed by different consortiums: Sony/Panasonic's Blu-ray Disc (BD), Toshiba's HD DVD and Maxell's Holographic Versatile Disc (HVD). The first generation of holographic media with 300 GB of storage capacity and a 160 Mbit/s transfer rate is scheduled for release in late 2006 by Maxell and its partner, InPhase. On November 18, 2003, the Chinese news agency Xinhua reported the final standard of the Chinese government-sponsored Enhanced Versatile Disc (EVD), and several patents for it. However, since then the format has generally failed to live up to expectations. On November 19, 2003, the DVD Forum decided by a vote of eight to six that HD DVD will be its official HDTV successor to DVD. This had no effect on the competing Blu-ray Disc Association's (BDA) determination that its format would succeed DVD, especially since most of the voters belonged to both groups. On April 15, 2004, in a co-op project with TOPPAN Printing Co., the electronics giant Sony Corp. successfully developed the paper disc, a storage medium that is made out of 51% paper and offers up to 25 GB of storage, about five times more than the standard 4.7 GB DVD. The disc can be easily cut with scissors and recycled, offering foolproof data security and an environment-friendly storage media. As reported in a mid 2005 issue of Popular Mechanics, it is not yet clear which technology will win the format war over DVD. HD DVD discs have a lower capacity than Blu-ray discs (15 GB vs. 25 GB for single layer, 30 GB vs. 50 GB for dual layer), but Blu-ray requires changes in manufacturing machinery and techniques and is thus more expensive. In April, 2000, Sonic Solutions and Ravisent announced hDVD, an HDTV extension to DVD that presaged the HD formats that debuted 6 years later. This situation—multiple new formats fighting as the successor to a format approaching purported obsolescence—previously appeared as the "war of the speeds" in the record industry of the 1950s. It is also, of course, similar to the VHS/Betamax war in consumer video recorders in the late 1980s. It is possible that neither Blu-ray, HD DVD, nor a next-generation optical recording products will succeed. The storage capacities of hard disk drives and solid-state memory have grown faster than those of optical discs (since CD's introduction year, 1983, storage capacity of HDDs grew by a factor of about 150,000, from 5 MB to 750 GB, while the capacity of Blu-ray is only 90 times larger than CD), and all three are much more capable of storing general consumer content —such as photos, music, and video— than in the past. Hard disk drives having a few terabytes of storage capacity will be on the market before 2008. A terabyte is equivalent to about 2000 CD-ROMs, 130 DVD-9s, or 20 dual-layer BDs. However, hard disk drives and memory cards are at the moment hundreds of times more expensive than optical discs (US$50 or more compared to $0.50). The price per gigabyte of a hard disk drive, $0.40 ($200/500 GB), is growing closer to that of a DVD-ROM, $0.06 ($0.50/8.5 GB); BD-ROM, $0.03 ($1.50/50 GB); recordable DVD-5, $0.10 ($0.50/4.7 GB); or recordable DVD-9, $0.30 ($2.50/8.5 GB); and is lower than the cost of a BD-RE25, $1.20 ($30/25 GB). Direct access to large amounts of information is much more convenient with a hard disk drive. As broadband becomes fast enough (40 Mbit/s and higher) and more widely available, physical media will become less important as a distribution format. One last possibility is that DVD will not be replaced in terms of Home Theatre by any format currently developed. People may not be so keen to upgrade their DVD collection so (relatively) soon. DVD may remain the format of choice for many more years, which may lead to the creation of a better technology that will replace it. The new generations of optical formats have restricted access (anti-copy mechanisms), and it is therefore possible that consumers may ignore them. Direct-to-DVD The popularity of DVDs has caused the term "direct-to-DVD" to widely replace "direct-to-video" (see main article). However, the lucrative market for DVDs has resulted in less stigma for direct-to-DVD releases as compared to direct-to-video releases. Some minor films can be made with a small budget and turn a profit on DVD sales alone, and some are made specifically for this purpose. See also Official Forum Quality guide Knowledge | |||||||||||||||||||||
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