Dvd

Information about Dvd

**DVD**
DVD-R read/write side
Media type:	Optical disc
Capacity:	4.7 GB (single layer), 8.5 GB (dual layer)
Usage:	Data storage, audio, video, games

Optical disc authoring

Optical disc Optical disc image Recorder hardware Authoring software Recording technologies Recording modes Packet writing
Optical media types
Laserdisc Compact disc/CD-ROM: CD-R, CD-RW MiniDisc DVD: DVD-R, DVD-D, DVD-R DL, DVD+R, DVD+R DL, DVD-RW, DVD+RW, DVD-RW DL, DVD+RW DL, DVD-RAM Blu-ray Disc: BD-R, BD-RE HD DVD: HD DVD-R: HD DVD-RAM UDO UMD Holographic data storage 3D optical data storage History of optical storage media
Standards
Rainbow Books File systems ISO 9660 Joliet Rock Ridge Amiga Rock Ridge extensions El Torito Apple ISO9660 Extensions Universal Disk Format Mount Rainier

DVD (also known as "Digital Versatile Disc" and "Digital Video Disc") is a popular optical disc storage media format used for data storage. Its main uses are for movies, software, and data archiving. Most DVDs are of the same dimensions as compact discs (CDs) but store more than 6 times the data.

The term DVD is used in describing three ways that data is stored on the disks — DVD-ROM has data which can only be read and not written, DVD-R can be written once and then functions as a DVD-ROM, and DVD-RAM holds data that can be re-written multiple times.

DVD-Video and DVD-Audio discs respectively refer to properly formatted and structured video and audio content. Everything else, including other types of DVD discs with video content, is referred to as a DVD-Data disc. DVD is also used generically to refer to HD (High Density) video disc formats Blu-ray and HD DVD.

History

In the early 1990s two high-density optical storage standards were being developed; one was the MultiMedia Compact Disc, backed by Philips and Sony, and the other was the Super Density disc, supported by Toshiba, Time Warner, Matsushita Electric, Hitachi, Mitsubishi Electric, Pioneer, Thomson, and JVC. IBM's president, Lou Gerstner, acting as a matchmaker, led an effort to unite the two camps behind a single standard, anticipating a repeat of the costly videotape format war between VHS, Betamax and Video 2000 in the 1980s.

Philips and Sony abandoned their MultiMedia Compact Disc and fully agreed upon Toshiba's SuperDensity Disc with only one modification, namely changing to EFMPlus modulation. EFMPlus was chosen as it has a great resilience against disc damage such as scratches and fingerprints. EFMPlus, created by Kees Immink, who also designed EFM, is 6% less efficient than the modulation technique originally used by Toshiba, which resulted in a capacity of 4.7 GB as opposed to the original 5 GB. The result was the DVD specification, finalized for the DVD movie player and DVD-ROM computer applications in December 1995.^[1] In May 1997, the DVD Consortium was replaced by the DVD Forum, which is open to all other companies.

Etymology

"DVD" was originally used as an initialism for the unofficial term "digital videodisk".^[2] It was reported in 1995, at the time of the specification finalization, that the letters officially stood for "digital versatile disc" (due to non-video applications),^[3] however, the text of the press release announcing the specification finalization only refers to the technology as "DVD", making no mention of what (if anything) the letters stood for.^[1] A newsgroup FAQ written by Jim Taylor (a prominent figure in the industry) claims that four years later, in 1999, the DVD Forum stated that the format name was simply the three letters "DVD" and did not stand for anything.^[4] The official DVD specification documents have never defined DVD. Usage in the present day varies, with "DVD", "Digital Video Disc", and "Digital Versatile Disc" all being common.

DVD disc capacity

	Single layer capacity		Dual/Double layer capacity
Physical size	GB	GiB	GB	GiB
12 cm, single sided	4.7	4.38	8.5	7.96
12 cm, double sided	9.4	8.75	17.1	15.93
8 cm, single sided	1.4	1.30	2.6	2.42
8 cm, double sided	2.8	2.61	5.2	4.84

The 12 cm type is a standard DVD, and the 8 cm variety is known as a mini-DVD. These are the same sizes as a standard CD and a mini-CD, respectively.

Note: GB here means gigabyte, equal to 10⁹ (or 1,000,000,000) bytes. Many programs will display gibibyte (GiB), equal to 2³⁰ (or 1,073,741,824) bytes.

Example: A disc with 8.5 GB capacity is equivalent to: (8.5 × 1,000,000,000) / 1,073,741,824 ≈ 7.92 GiB.

Capacity Note: There is a difference in capacity (storage space) between + and - DL DVD formats. For example, the 12 cm single sided disk has capacities:

Disk Type	Sectors	bytes	GB	GiB
DVD-R SL	2,298,496	4,707,319,808	4.7	4.384
DVD+R SL	2,295,104	4,700,372,992	4.7	4.378
DVD-R DL	4,171,712	8,543,666,176	8.5	7.957
DVD+R DL	4,173,824	8,547,991,552	8.5	7.961

Capacity nomenclature

The five basic types of DVD are referred to by their approximate capacity in gigabytes.

DVD type	Name
Single sided, single layer	DVD-5
Single sided, dual layer	DVD-9
Double sided, single layer	DVD-10
Double sided, dual layer on one side, single on other	DVD-14^[5]
Double sided, dual layer on both sides	DVD-18

Technology

Internal mechanism of a DVD-ROM Drive

DVD uses 650 nm wavelength laser diode light as opposed to 780 nm for CD. This permits a smaller spot on the media surface that is 1.32 µm for DVD while it was 2.11 µm for CD.

Writing speeds for DVD were 1x, that is 1350 kB/s (1318 KiB/s), in first drives and media models. More recent models at 18x or 20x will have 18 or 20 times that speed. Note that for CD drives, 1x means 153.6 kB/s (150 KiB/s), 9 times slower. DVD FAQ

DVD recordable and rewritable

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 (minus/dash), +R/RW (plus), -RAM.

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 was developed for the DVD Forum by Pioneer Corporation, DVD+R DL was developed for the DVD+RW Alliance by Philips and Mitsubishi Kagaku Media (MKM).^[6]

A Dual Layer disc differs from its usual DVD counterpart by employing a second physical layer within the disc itself. The drive with Dual Layer capability accesses the second layer by shining the laser through the first semi-transparent layer. The layer change mechanism in some DVD players can show a noticeable pause, as long as two seconds by some accounts. This caused more than a few viewers to worry that their dual layer discs were damaged or defective, with the end result that studios began listing a standard message explaining the dual layer pausing effect on all dual layer disc packaging.

DVD recordable discs supporting this technology are backward compatible with some existing DVD players and DVD-ROM drives.^[7] Many current DVD recorders support dual-layer technology, and the price is comparable to that of single-layer drives, though the blank media remain more expensive.

DVD-Video

Main article: DVD-Video

DVD-Video is a standard for storing video content on DVD media. In the U.S., weekly DVD-Video rentals first out-numbered weekly VHS cassette rentals in June 2003, illustrating the rapid adoption rate of the technology in the marketplace.^[8]

Though many resolutions and formats are supported, most consumer DVD-Video disks use either 4:3 or 16:9 aspect ratio MPEG-2 video, stored at a resolution of 720×480 (NTSC) or 720×576 (PAL). Audio is commonly stored using the Dolby Digital (AC-3), Digital Theater System (DTS) formats, ranging from monaural to 5.1 channel "Surround Sound" presentations, and/or MPEG-1 Layer 2. Although the specifications for video and audio requirements vary by global region and television system, many DVD players support all possible formats. DVD-Video also supports features like menus, selectable subtitles, multiple camera angles, and multiple audio tracks.

DVD-Audio

Main article: 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. 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 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

Main article: CPRM

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).

To date, CPPM has not been "broken" in the sense that DVD-Video's CSS has been broken, but ways to circumvent it have been developed.^[9] By modifying commercial DVD(-Audio) playback software to write the decrypted and decoded audio streams to the hard disk, users can, essentially, extract content from DVD-Audio discs much in the same way they can from DVD-Video discs.

Competitors and successors

There are several possible successors to DVD being developed by different consortia. Sony/Panasonic's Blu-ray Disc (BD) and Toshiba's HD DVD began to gain traction in 2007, and next-generation technologies such as Maxell's Holographic Versatile Disc (HVD) and 3D optical data storage are being actively developed.

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.

References

1. ^ DVD Format Unification (press release). TOSHIBA (December 8, 1995). Retrieved on 2007-07-12.
2. ^ A Battle for Influence Over Insatiable Disks. New York Times (1995-01-11). Retrieved on 2007-04-09.
3. ^ DVD designers go with AC-3 Final specs for 'digital versatile disc'.... The Hollywood Reporter (1995-12-11). Retrieved on 2007-04-16.
4. ^ DVD FAQ. DVD Demystified (2006-09-12).
5. ^ DVD-14. AfterDawn Ltd.. Retrieved on 2007-02-06.
6. ^ Dual Layer Recording burnworld.com. Retrieved on 2007-07-06.
7. ^ Backwards Compatible burnworld.com. Retrieved on 2007-07-06.
8. ^ Bakalis, Anna (2003-06-20). It's unreel: DVD rentals overtake videocassettes. Washington Times.
9. ^ DVD-Audio's CPPM can be got around with a WinDVD patch. Retrieved on 2007-07-06.

Bennett, Hugh (April 2004). Understanding Recordable & Rewritable DVD. Optical Storage Technology Association. Retrieved on 2006-12-17.
Labarge, Ralph. DVD Authoring and Production. Gilroy, Calif.: CMP Books, 2001. ISBN 1-57820-082-2.
Taylor, Jim. DVD Demystified, 2nd edition. New York: McGraw-Hill Professional, 2000. ISBN 0-07-135026-8.

External links

Official

Quality guide

Dual Layer Explained – Informational Guide to the Dual Layer Recording Process

Knowledge

optical disc is a flat, circular, usually polycarbonate disc where data is stored in the form of pits (or bumps) within a flat surface, usually along a single spiral groove that covers the entire recorded surface of the disc.
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gigabyte or Gbyte (derived from the SI prefix giga-) is a unit of information or computer storage meaning either 1000³ bytes or 1024³ bytes (1000³ = one billion). The usage of the word "gigabyte" is ambiguous, depending on the context.
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optical disc authoring, including DVD authoring, known often as burning, is the process of recording source material—video, audio or other data—onto an optical disc (compact disc or DVD).
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disk image is a computer file containing the complete contents and structure of a data storage medium or device, such as a Hard drive, CD or DVD. The term has been generalized to cover any such file, whether originated from an actual physical storage device or not.
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optical disk drive (ODD) is a disk drive that uses electromagnetic waves as part of the process of reading and writing data. It is a computer's peripheral device, that stores data on optical discs.
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Optical disc authoring software is computer software for authoring optical discs including CD-ROMs and DVDs. They are also known by synonyms such as CD burning application or DVD authoring software. Such software is required to use an optical disc recorder.
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Disc At Once, Track At Once, Session at Once (i.e. multiple burning sessions for one disc), or packet writing modes. Each mode serves different purposes:

Disc At Once: writes the entire disc in one pass; preferred for duplication masters

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Disc-At-Once, Track-At-Once, and Session-At-Once.

CD Disc-At-Once

Disc-At-Once or DAO for CD-R media is a mode that masters the disc contents in one pass, rather than a track at a time as in Track At Once.
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Packet writing is an optical disc recording technology used to allow writeable CD and DVD media to be used in a similar manner to a floppy disk. Packet writing allows the user to access the contents of a CD-R or CD-RW disc directly through a mounted filesystem (Unix, Linux, Mac OS
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Laserdisc

Laserdisc (left) compared to a DVD (right).
Media type: Optical disc
Encoding: Various
Developed by: MCA
Usage: Video storage

Optical disc authoring

Optical disc
Optical disc image
Recorder hardware
Authoring software

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Compact Disc

The closely spaced tracks on the readable surface of a Compact Disc cause light to diffract into a full visible colour spectrum
Media type: Optical disc
Encoding: Various
Capacity: Typically up to 700 MB
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CD-ROM (an abbreviation of "Compact Disc read-only media") is a Compact Disc that contains data accessible by a computer. While the Compact Disc format was originally designed for music storage and playback, the format was later adapted to hold any form of binary data.
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CD-R (Compact Disc-Recordable) is a variation of the Compact Disc invented by Philips and Sony. CD-R is a Write Once, Read Many optical medium (though the whole disk does not have to be entirely written in the same session) and retains a high level of
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Compact Disc ReWritable (CD-RW) is a rewritable optical disc format. Known as CD-Erasable (CD-E) during its development, CD-RW was introduced in 1997, and was preceded by the never officially released CD-MO in 1988.
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MiniDisc

The Sony MZ1 MiniDisc player, the first to hit the market in 1992.
Media type: Magneto-optical disc
Encoding: ATRAC, linear PCM (with Hi-MD)
Capacity: 80 min (standard MiniDisc), up to 45 hours of audio (1 GB capacity) (with Hi-MD)
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DVD-R is a DVD recordable format. A DVD-R has a larger storage capacity than its optical predecessor, the 700 MB CD-R, typically storing 4.71 GB (or 4.382 GiB), although the capacity of the original standard developed by Pioneer was 3.95 GB (3.68 GiB).
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DVD-D is a self-destructing disposable DVD format. Like the EZ-D, it is sold in a cardboard sleeve, and begins to destroy itself after several hours.

DVD-D now exists as one time play only for movies, limited time play for video games, and recordable DVD-D.
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DVD-R DL (DL stands for Dual Layer), also called DVD-R9, is a derivative of the DVD-R format standard. DVD-R DL discs employ two recordable dye layers, each capable of storing nearly the 4.7 GB (4.
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DVD+R is a once-writable optical disc with 4.7 GB (4.377 GiB) of storage capacity (more precisely, 2295104 sectors of 2048 bytes each). It has slightly less storage capacity than the DVD-R (4.382 GiB).
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DVD+R DL (DL stands for Dual Layer, commonly mistaken as Double Layer), also called DVD+R9, is a derivative of the DVD+R format created by the DVD+RW Alliance. Its use was first demonstrated in October 2003.
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DVD-RW disc ("DVD dash RW", sometimes nicknamed "DVD minus RW") is a rewritable optical disc with equal storage capacity to a DVD-R, typically 4.7 GB. The format was developed by Pioneer in November 1999 and has been approved by the DVD Forum.
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DVD+RW is the name of a standard for optical discs: one of several types of DVD, which hold up to about 4.7GB per disc (interpreted as approximately 4.7 × 10⁹ bytes; actually 2295104 sectors of 2048 bytes each) and are used for storing films, music or other data.
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DVD-RW DL is a rewritable optical disc standard with storage capacity of 8.5 GB. DVD-RW DL discs employ two rewritable dye layers. It's approved by DVD Forum as "DVD Specifications for Re-recordable Disc for Dual Layer (DVD-RW for DL) Physical Specifications, Version 2.0".
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DVD+RW DL is a rewritable optical disc with storage capacity of 8.5 GB. DVD+RW DL discs employ two rewritable dye layers.

In March 2006, the DVD+RW Alliance approved DVD+RW part 2: Dual Layer, volume 1; DVD+RW 8.5 Gbytes, Basic Format Specifications, version 1.
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DVD-RAM (DVD–Random Access Memory) is a disc specification presented in 1996 by the DVD Forum, which specifies rewritable DVD-RAM media and the appropriate DVD writers. DVD-RAM media have been used in computers as well as camcorders and personal video recorders since 1998.
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Blu-ray Disc

Media type: High-density optical disc
Encoding: MPEG-2, MPEG-4 AVC (H.264), and VC-1
Capacity: 25 GB (single layer), 50 GB (dual layer)
Read mechanism: 1x@36 Mbit/s & 2x@72 Mbit/s
Developed by: Blu-ray Disc Association
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Blu-ray Disc recordable refers to two optical disc formats that can be recorded with an optical disc recorder. BD-R discs can be written to once, whereas BD-RE can be erased and re-recorded multiple times.
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HD DVD

Media type: High-density optical disc
Encoding: VC-1, H.264, and MPEG-2
Capacity: 15 GB (single layer) 30 GB (dual layer)
Read mechanism: 1x@36 Mbit/s & 2x@72 Mbit/s
Developed by: DVD Forum
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