DVD, also known as
Digital Versatile
Disc or
Digital Video Disc,
is an
optical disc storage media format, and was founded in
1995. Its main uses are
video and
data storage. DVDs are
of the same dimensions as compact discs (
CDs),
but store more than six times as much data.
Variations of the term
DVD often describe the way data is
stored on the discs: DVD-ROM (read only memory) has data that can
only be read and not written;
DVD-R and
DVD+R (recordable) can record data only once,
and then function as a DVD-ROM;
DVD-RW
(re-writable),
DVD+RW, and
DVD-RAM (random access memory) can all record and
erase data multiple times. The wavelength used by standard DVD
lasers is 650 nm; thus, the light has a
red
color.
DVD-Video and
DVD-Audio discs refer to properly formatted and
structured video and audio content, respectively. Other types of
DVDs, including those with video content, may be referred to as DVD
Data discs.
History
In
1993, two high-definition optical storage
formats were being developed. One was the MultiMedia
Compact Disc (MMCD), backed by
Philips and
Sony, and the other
was the Super Density (SD) disc, supported by
Toshiba,
Time Warner,
Matsushita Electric,
Hitachi,
Mitsubishi Electric,
Pioneer,
Thomson, and
JVC.
Representatives of the SD camp approached
IBM, asking for advice on
the file system to use for their disc as well as looking for
support for their format for storing computer data.
A researcher from
IBM's Almaden Research
Center
received that request and also learned of the MMCD
development project. Wary of being caught in a repeat of the
costly videotape format war
between VHS and Betamax
in the 1980s, he convened a group of computer industry experts,
including representatives from Apple
, Microsoft, Sun,
Dell, and many others. This group was
referred to as the Technical Working Group, or TWG. The TWG voted
to boycott both formats unless the two camps agreed on a single,
converged standard.
Lou Gerstner,
president of IBM, was recruited to apply pressure on the executives
of the warring factions. Eventually, the computer companies won the
day, and a single format, now called DVD, was agreed upon. The TWG
also collaborated with the
Optical Storage
Technology Association (OSTA) on the use of their
implementation of the ISO-13346 file system (known as
Universal Disc Format [UDF]) for use
on the new DVDs.
Philips and Sony decided it was in their best interest to avoid
another format war over their MultiMedia Compact Disc, and agreed
to unify with companies backing the Super Density Disc to release a
single format with technologies from both. The specification was
mostly similar to Toshiba and Matsushita's Super Density Disc,
except for the dual-layer option (MMCD was single-sided and
optionally dual-layer, whereas SD was single-layer but optionally
double-sided) and
EFMPlus modulation. EFMPlus was
chosen due to its 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. The DVD Video format was first introduced by Toshiba
in Japan in November 1996, in the United States in March 1997 (test
marketed), in Western Europe in May 1998, in Eastern Europe in
October that same year, and in Australia in February 1999. In May
1997, the
DVD Consortium was replaced
by the
DVD Forum, which is open to all
other companies. DVD specifications created and updated by DVD
Forum are published as so-called
DVD Books (e.g. DVD-ROM
Book, DVD-Audio Book, DVD-Video Book, DVD-R Book, DVD-RW Book,
DVD-RAM Book, DVD-AR Book,
DVD-VR Book, etc).
Some specifications for mechanical, physical and optical
characteristics of DVD optical discs can be downloaded as
freely available standards from
ISO
website. There is also
DVD+RW
Alliance, which publish competing DVD specifications such as
DVD+R, DVD+R DL, DVD+RW or
DVD+RW DL.
These DVD formats are also ISO standards. Some of DVD
specifications (e.g. for DVD-Video) are not publicly available and
can be obtained only from DVD Format/Logo Licensing Corporation for
a fee of $ 5000. Every subscriber must sign a
non-disclosure agreement as certain
information in the DVD Book is proprietary and confidential.
Etymology
The official DVD specification documents have never defined the
initialism DVD. Usage in the
present day varies, with
Digital Versatile
Disc,
Digital Video Disc,
and
DVD being the most common.
DVD was originally used as an initialism
for the unofficial term
digital
videodisk.
It was reported in 1995, at the time of the specification
finalization, that the letters officially stood for
Digital Versatile Disc (due to nonvideo
applications).
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.
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.
The
DVD Forum website has a section called
"DVD Primer" in which the answer to the question, "What does DVD
mean?" reads, "The keyword is 'versatile.' Digital Versatile Discs
provide superb video, audio and data storage and access—all on one
disc."
DVD capacity
Capacity and nomenclature
SS = single-sided, DS = double-sided, SL = single-layer, DL
= dual-layer
| Designation |
Sides |
Layers
(total) |
Diameter |
Capacity |
| (cm) |
(GB) |
(GiB) |
| DVD-1 |
SS SL |
1 |
1 |
8 |
1.46 |
1.36 |
| DVD-2 |
SS
DL |
1 |
2 |
8 |
2.66 |
2.47 |
| DVD-3 |
DS SL |
2 |
2 |
8 |
2.92 |
2.72
|
| DVD-4 |
DS DL |
2 |
4 |
8 |
5.32 |
4.95 |
| DVD-5 |
SS SL |
1 |
1 |
12 |
4.70 |
4.38 |
| DVD-9 |
SS DL |
1 |
2 |
12 |
8.54 |
7.95 |
| DVD-10 |
DS SL |
2 |
2 |
12 |
9.40 |
8.75 |
| DVD-14 |
DS DL/SL |
2 |
3 |
12 |
13.24 |
12.33 |
| DVD-18 |
DS DL |
2 |
4 |
12 |
17.08 |
15.90 |
Capacity and nomenclature of (re)writable discs
| Designation |
Sides |
Layers
(total) |
Diameter |
Capacity |
| (cm) |
(GB) |
(GiB) |
| DVD-R |
SS SL (1.0) |
1 |
1 |
12 |
3.95 |
3.68
|
| DVD-R |
SS SL (2.0) |
1 |
1 |
12 |
4.70 |
4.37 |
| DVD-RW |
SS SL |
1 |
1 |
12 |
4.70 |
4.37 |
| DVD+R |
SS SL |
1 |
1 |
12 |
4.70 |
4.37 |
| DVD+RW |
SS SL |
1 |
1 |
12 |
4.70 |
4.37
|
| DVD-R |
DS SL |
2 |
2 |
12 |
9.40 |
8.75 |
| DVD-RW |
DS SL |
2 |
2 |
12 |
9.40 |
8.75 |
| DVD+R |
DS SL |
2 |
2 |
12 |
9.40 |
8.75 |
| DVD+RW |
DS SL |
2 |
2 |
12 |
9.40 |
8.75 |
| DVD-RAM |
SS SL |
1 |
1 |
8 |
1.46 |
1.36* |
| DVD-RAM |
DS SL |
2 |
2 |
8 |
2.65 |
2.47* |
| DVD-RAM |
SS SL (1.0) |
1 |
1 |
12 |
2.58 |
2.40 |
| DVD-RAM |
SS SL (2.0) |
1 |
1 |
12 |
4.70 |
4.37 |
| DVD-RAM |
DS SL (1.0) |
2 |
2 |
12 |
5.16 |
4.80 |
| DVD-RAM |
DS SL (2.0) |
2 |
2 |
12 |
9.40 |
8.75* |
The basic types of DVD (12 cm diameter, single-sided or
homogenous double-sided) are referred to by a rough approximation
of their capacity in gigabytes. In draft versions of the
specification, DVD-5 indeed held five gigabytes, but some
parameters were changed later on as explained above, so the
capacity decreased. Other
formats, those
with 8 cm diameter and hybrid variants, acquired similar
numeric names with even larger deviation.
The 12 cm type is a standard DVD, and the 8 cm variety is
known as a
MiniDVD. These are the same sizes
as a standard CD and a
mini-CD,
respectively. The capacity by surface (MiB/cm
2) varies
from 6.92 MiB/cm
2 in the DVD-1 to 18.0
MiB/cm
2 in the DVD-18.
As with hard disk drives, in the DVD realm,
gigabyte and the symbol GB are usually used in the
SI sense (i.e., 10
9, or 1,000,000,000
bytes). For distinction,
gibibyte (with
symbol GiB) is used (i.e., 2
30, or 1,073,741,824 bytes).
Most computer operating systems display file sizes in gibibytes,
mebibytes, and
kibibytes, labeled as gigabyte, megabyte, and
kilobyte, respectively.
Each DVD sector contains 2,418 bytes of data, 2,048 bytes of which
are user data. There is a small difference in storage space between
+ and
- (hyphen) formats:
Capacity differences of writable DVD formats
| Type |
Sectors |
Bytes |
MB |
MiB |
GB |
GiB |
| DVD−R SL |
2,298,496 |
4,707,319,808 |
4,707.320 |
4,489.250 |
4.707 |
4.384 |
| DVD+R SL |
2,295,104 |
4,700,372,992 |
4,700.373 |
4,482.625 |
4.700 |
4.378 |
| DVD−R DL |
4,171,712 |
8,543,666,176 |
8,543.666 |
8,147.875 |
8.544 |
7.957 |
| DVD+R DL |
4,173,824 |
8,547,991,552 |
8,547.992 |
8,152.000 |
8.548 |
7.961 |
Technology
Internal mechanism of a DVD-ROM
Drive.
DVD-RW Drive operating with the
protective cover removed.
DVD uses 650 nm wavelength
laser
diode light as opposed to 780 nm for CD. This permits a
smaller pit to be etched on the media surface compared to CDs
(0.74 µm for DVD versus 1.6 µm for
CD),
allowing for a DVD's increased storage capacity.
In comparison,
Blu-ray, the successor to the
DVD format, uses a wavelength of 405 nm, and one dual-layer
disc has a 50 GB storage capacity.
Writing speeds for DVD were 1×, that is, 1350
kB/s (1,318
KiB/s), in the first drives and media models.
More recent models, at 18× or 20×, have 18 or 20 times that speed.
Note that for CD drives, 1× means 150
KiB/s (153.6 kB/s), approximately 9 times
slower.
DVD drive speeds
| Drive speed |
Data rate |
~Write time (min) |
| (Mbit/s) |
(MB/s) |
(MiB/s) |
SL |
DL |
| 1× |
10.80 |
1.35 |
1.29 |
61 |
107 |
| 2× |
21.60 |
2.70 |
2.57 |
31 |
54 |
| 2.4× |
25.92 |
3.24 |
3.09 |
25 |
45 |
| 2.6× |
28.08 |
3.51 |
3.35 |
23 |
41 |
| 4× |
43.20 |
5.40 |
5.15 |
15 |
27 |
| 6× |
64.80 |
8.10 |
7.72 |
10 |
18 |
| 8× |
86.40 |
10.80 |
10.30 |
8 |
13 |
| 10× |
108.00 |
13.50 |
12.87 |
6 |
11 |
| 12× |
129.60 |
16.20 |
15.45 |
5 |
9 |
| 16× |
172.80 |
21.60 |
20.60 |
4 |
7 |
| 18× |
194.40 |
24.30 |
23.17 |
3 |
6 |
| 20× |
216.00 |
27.00 |
25.75 |
3 |
5 |
| 22× |
237.60 |
29.70 |
28.32 |
3 |
5 |
| 24× |
259.20 |
32.40 |
30.90 |
3 |
4 |
DVD recordable and rewritable
HP initially developed recordable
DVD media from the need to store data for backup and
transport.
DVD recordables are now also used for consumer audio and video
recording. Three formats were developed: DVD-
R/
RW (hyphen), DVD+
R/
RW (plus), and
DVD-RAM.
Dual-layer recording
Dual-layer recording (sometimes also known as
double-layer
recording) allows
DVD-R and
DVD+R discs to store significantly more data—up to
8.54
gigabytes per disc, compared with 4.7
gigabytes for single-layer discs. Along with this, DVD-DL's have
slower write speeds as compared to ordinary DVD's and when played
on a DVD player, a slight transition can be seen between the
layers.
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).
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 semitransparent layer. In some DVD players,
the layer change can exhibit a noticeable pause, up to several
seconds. This caused some 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. Many current DVD recorders support dual-layer technology,
and the price is now comparable to that of single-layer drives,
although the blank media remain more expensive. The recording
speeds reached by dual-layer media are still well below those of
single-layer media.
There are two modes for dual-layer orientation. With
Parallel
Track Path (PTP), used on DVD-ROM, both layers start at the
inside diameter (ID) and end at the outside diameter (OD) with the
lead-out. With
Opposite Track
Path (OTP), used on many DVD Video discs, the lower layer
starts at the ID and the upper layer starts at the OD, where the
other layer ends; they share one
lead-in and one lead-out. However, some
DVD Video discs also use a parallel track, such as those authored
episodically, as in a disc with several separate episodes of a TV
series—where more often than not, the layer change is in-between
titles and therefore would not need to be authored in the opposite
track path fashion.
DVD Video
DVD Video is a standard for content on DVD media.
In the U.S., mass retailer sales of DVD Video titles and players
began in August 1997. By June 2003, weekly DVD Video rentals began
outnumbering weekly VHS cassette rentals, reflecting the rapid
adoption rate of the technology in the U.S. marketplace.Currently,
DVD Video is the dominant form of home video distribution
worldwide.
Although many resolutions and formats are supported, most consumer
DVD Video discs use either 4:3 or
anamorphic 16:9
aspect ratio MPEG-2
video, stored at a resolution of 720/704×480 (
NTSC) or 720/704×576 (
PAL) at 29.97,
25, or
23.976 FPS. Audio is commonly stored using the
Dolby Digital (AC-3) or
Digital Theater System (DTS) formats,
ranging from 16-bits/48 kHz to 24-bits/96 kHz format with
monaural to 6.1-channel "
Surround Sound" presentation, and/or
MPEG-1 Layer 2 and/or LPCM Stereophonic. 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 such as menus, selectable
subtitles, multiple camera angles, and multiple audio tracks.
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 (up to 24-bits/192 kHz versus
CDDA's 16-bits/44.1 kHz).
Compared with the CD format, the much higher-capacity DVD format
enables the inclusion of considerably more music (with respect to
total running time and quantity of songs) and/or far higher audio
quality (reflected by higher
sampling
rates and greater sample resolution, 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 in typical listening environments. DVD Audio
currently forms a niche market, probably due to the very sort of
format war with rival standard
SACD
that DVD Video avoided.
Security
DVD Audio discs employ a
DRM 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. 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.
Improvements and succession
In 2006, a new format called
Blu-ray
Disc (BD), designed by
Sony,
Philips, and
Panasonic, was
released as the successor to DVD. Another format,
HD DVD, competed unsuccessfully with this format in
the
format war of 2006–08. A dual
layer Blu-ray Disc can store 50 GB.
However, unlike previous format changes (e.g., audio tape to
compact disc, VHS videotape to DVD), there is no immediate
indication that production of the standard DVD will gradually wind
down, as they still dominate, with around 87% of video sales and
approximately one billion DVD player sales worldwide. In fact
experts claim that the DVD will remain the dominant medium for at
least another five years as Blu-Ray technology is still in its
introductory phase, write and read speeds being poor as well as the
fact of necessary hardware being expensive and not readily
available. Blu-ray players have struggled partly because the MPEG
I-frames stored on DVD discs were based on
JPEG, which carries
DCT information that can be
exploited to improve interpolation for higher resolutions.
Consumers initially were also slow to adopt Blu-ray due to the cost
. By 2009, 85% of stores were selling
Blu-ray Discs. A high-definition TV and
appropriate connection cables are also required to take advantage
of Blu-ray disc. Some analysts suggest that the biggest obstacle to
replacing DVD is due to its installed base; a large majority of
consumers are satisfied with DVDs. The DVD succeeded because it
offered a compelling alternative to VHS. In addition, Blu-ray
players are designed to be
backward-compatible, allowing older DVDs
to be played since the media are physically identical; this
differed from the change from vinyl to CD and from tape to DVD,
which involved a complete change in physical medium.
This situation can be best compared to the changeover from
78 rpm shellac recordings to 45 rpm and 33⅓ rpm vinyl
recordings; because the medium used for the earlier format was
virtually the same as the latter version (a disc on a turntable,
played using a needle),
phonographs
continued to be built to play obsolete 78s for decades after the
format was discontinued. Manufacturers have announced standard DVD
releases well into 2009, and the format remains the preferred one
for the release of older television programs and films, with some
programs such as
Star
Trek: The Original Series requiring remastering and
replacement of certain elements such as special effects in order to
be better received in high-definition viewing.
The
Holographic Versatile
Disc (HVD) is an optical disc technology that may one day hold
up to 3.9 terabytes (TB) of information, albeit the current maximum
is 500GB. It employs a technique known as collinear
holography.
The
5D DVD, being developed at the Swinburne University of
Technology in Melbourne
, Australia, uses a
multilaser system to encode and read data on multiple
layers. Disc capacities are estimated at up to 10 terabytes,
and the technology could be commercially ready within ten
years.
DVD as an archival medium
There are two considerations for an archival medium:
obsolescence and durability. If there is no
device that can read the medium, it is obsolete and the data is
unavailable and thus lost.
Durability of DVDs is measured by how long the data may be read
from the disc, assuming compatible devices exist that can read it:
that is, how long the disc can be stored until data is lost. Five
factors affect durability: sealing method, reflective layer,
organic dye makeup, where it was manufactured, and storage
practices.
According to the
Optical Storage
Technology Association (OSTA), "manufacturers claim life spans
ranging from 30 to 100 years for DVD, DVD-R and DVD+R discs and up
to 30 years for DVD-RW, DVD+RW and DVD-RAM", although a
manufacturer of 24-karat gold-based DVDs claims lifespans of up to
300 years. Of more conventional manufacturing processes,
Taiyo Yuden is frequently recommended for longer
durability.
DVD consumer rights
DVDs that have commercial movies and television content recorded on
them are subject to
copyright. The rise of
filesharing and "piracy" has prompted
many copyright owners to display notices on DVD packaging or
displayed on screen when the content is played that warn consumers
of the illegality of certain uses of the DVD.
Such notices do not always offer a reliable summary of DVD owners'
rights.
Generally, retail buyers of commercial prerecorded DVDs are free to
sell or exchange their property. Arrangements for renting and
lending differ more by geography. In the U.S., the right to rent or
lend out bought DVDs is protected by the
first-sale doctrine under the
Copyright Act of 1976. In Europe,
rental and lending rights are more limited, under a 1992 European
Directive that gives copyright holders broader powers to restrict
the commercial renting and public lending of DVD copies of their
work.
See also
References
- ISO ISO Freely Available Standards, Retrieved on
2009-07-24
- ISO ISO/IEC 17344:2009, Data interchange on 120 mm and
80 mm optical disc using +R format -- Capacity: 4,7 Gbytes and 1,46
Gbytes per side (recording speed up to 16X), Retrieved on
2009-07-26
- ISO ISO/IEC 25434:2008, Data interchange on 120 mm and
80 mm optical disc using +R DL format -- Capacity: 8,55 Gbytes and
2,66 Gbytes per side (recording speed up to 16X), Retrieved on
2009-07-26
- ISO ISO/IEC 17341:2009, Data interchange on 120 mm and
80 mm optical disc using +RW format -- Capacity: 4,7 Gbytes and
1,46 Gbytes per side (recording speed up to 4X), Retrieved on
2009-07-26
- ISO ISO/IEC 26925:2009, Data interchange on 120 mm and
80 mm optical disc using +RW HS format -- Capacity: 4,7 Gbytes and
1,46 Gbytes per side (recording speed 8X), Retrieved on
2009-07-26
- DVD FLLC (2009) DVD
Format Book, Retrieved on 2009-08-14
- DVD FLLC (2009) How
To Obtain DVD Format/Logo License (2005-2009), Retrieved on
2009-08-14
- DVD Primer at DVDForum.org
- Cinram: DVD in Detail
- The write time is wildly optimistic for higher (>4x) write
speeds, due to being calculated from the maximum drive write speed
instead of the average drive write speed.
DVD Manufacturing
Further reading
- 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.
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