HOME

TheInfoList



The compact disc (CD) is a
digital Digital usually refers to something using digits, particularly binary digits. Technology and computing Hardware *Digital electronics Digital electronics is a field of electronics Electronics comprises the physics, engineering, technology a ...
optical disc drive. (CD-R), showing characteristic iridescence. In computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithmic processes and de ...
data storage On a reel-to-reel tape recorder (Sony TC-630), the recorder is data storage equipment and the magnetic tape is a data storage medium. Data storage is the recording (storing) of information Information can be thought of as the resoluti ...
format that was co-developed by
Philips Koninklijke Philips N.V. (literally ''Royal Philips'', commonly shortened to Philips, stylized in its logo as PHILIPS) is a Dutch multinational conglomerate corporation that was founded in Eindhoven. Since 1997, it has been mostly headquarte ...

Philips
and
Sony is a Japanese Multinational corporation, multinational conglomerate (company), conglomerate corporation headquartered in Kōnan, Minato, Tokyo. The company operates as one of the world's largest manufacturers of consumer and professional ...

Sony
to store and play
digital audio Digital audio is a representation of sound recorded in, or converted into, Digital signal (signal processing), digital form. In digital audio, the sound wave of the audio signal is typically encoded as numerical Sampling (signal processing), sa ...
recordings. In August 1982, the first compact disc was manufactured. It was then released in October 1982 and branded as '' Digital Audio Compact Disc''. The format was later adapted for storage of data (
CD-ROM A CD-ROM (, compact disc read-only memory) is a pre-pressed optical compact disc that contains data. Computers can read—but not write to or erase—CD-ROMs, i.e. it is a type of read-only memory. History During the 1990s, CD-ROMs were popul ...
). Several other formats were further derived from these, including write-once audio and data storage (
CD-R CD-R (COMPACT DISC – Recordable) is a digital optical disc storage format. A CD-R disc is a compact disc#REDIRECT Compact disc {{redirect category shell, {{R move {{R from other capitalization, printworthy {{R yes print ... that can be ...

CD-R
), rewritable media (
CD-RW CD-RW (Compact Disc-ReWritable) is a digital optical disc storage format introduced in 1997. A CD-RW compact disc (CD-RWs) can be written, read, erased, and re-written. CD-RWs, as opposed to CDs, require specialized readers that have sensitiv ...
),
Video CD Video CD (abbreviated as VCD, and also known as Compact Disc Digital Video) is a home video Home video is prerecorded video media sold or rented for home viewing. The term originates from the VHS/Betamax Betamax (also known as Beta, as ...
(VCD),
Super Video CD Super Video CD (Super Video Compact Disc or SVCD) is a digital format for storing video Video is an electronic medium for the recording, copying, playback, broadcasting Broadcasting is the distribution of sound, audio or video content ...
(SVCD),
Photo CD 330px, Kodak Photo CD and packaging Photo CD is a system designed by Kodak The Eastman Kodak Company (referred to simply as Kodak ) is an American public company that produces various products related to its historic basis in analogue ph ...

Photo CD
, Picture CD, Compact Disc-Interactive (
CD-i The Compact Disc-Interactive (CD-I, later CD-i) is a Digital media, digital optical disc data storage device, data storage format that was mostly developed and marketed by Dutch company Philips. It was created as an extension of Compact Disc Dig ...
) and Enhanced Music CD. Standard CDs have a diameter of and are designed to hold up to 74 minutes of uncompressed
stereo STEREO (Solar Terrestrial Relations Observatory) is a Sun, solar observation mission. Two nearly identical spacecraft were launched in 2006 into orbits around the Sun that cause them to respectively pull farther ahead of and fall gradually behind ...

stereo
digital audio or about 650  MB of data. Capacity is routinely extended to 80 minutes and 700  MB by arranging more data closely on the same sized disc. The
Mini CD 280px, Business card CD Mini CDs, or pocket CDs, are CDs with a smaller diameter and one-third the storage capacity of a standard 120 mm disc. Formats Amongst the various formats are the * Mini CD single, a small disc. The format is main ...
has various diameters ranging from ; they are sometimes used for CD singles, storing up to 24 minutes of audio, or delivering
device driver In computing, a device driver is a computer program that operates or controls a particular type of Peripheral, device that is attached to a computer or automaton. A driver provides a software Interface (computing), interface to Computer hardware, ...
s. At the time of the technology's introduction in 1982, a CD could store much more data than a
personal computer A personal computer (PC) is a multi-purpose computer A computer is a machine that can be programmed to carry out sequences of arithmetic or logical operations automatically. Modern computers can perform generic sets of operations known a ...
hard disk drive A hard disk drive (HDD), hard disk, hard drive, or fixed disk is an electro-mechanical data storage device File:Reel-to-reel recorder tc-630.jpg, On a reel-to-reel tape recorder (Sony TC-630), the recorder is data storage equipment an ...

hard disk drive
, which would typically hold 10 MB. By 2010, hard drives commonly offered as much storage space as a thousand CDs, while their prices had plummeted to commodity level. In 2004, worldwide sales of audio CDs, CD-ROMs, and CD-Rs reached about 30 billion discs. By 2007, 200 billion CDs had been sold worldwide.


Physical details

A CD is made from thick,
polycarbonate Polycarbonates (PC) are a group of thermoplastic polymers containing carbonate groups in their chemical structures. Polycarbonates used in engineering are strong, tough materials, and some grades are optically transparent. They are easily worke ...

polycarbonate
plastic and weighs 14–33 grams. From the center outward, components are: the center spindle hole (15 mm), the first-transition area (clamping ring), the clamping area (stacking ring), the second-transition area (mirror band), the program (data) area, and the rim. The inner program area occupies a radius from 25 to 58 mm. A thin layer of
aluminum Aluminium (aluminum in American American(s) may refer to: * American, something of, from, or related to the United States of America, commonly known as the United States The United States of America (USA), commonly known as the Unit ...
or, more rarely,
gold Gold is a chemical element with the Symbol (chemistry), symbol Au (from la, aurum) and atomic number 79, making it one of the higher atomic number elements that occur naturally. In a pure form, it is a brightness, bright, slightly reddish yel ...
is applied to the surface, making it reflective. The metal is protected by a film of lacquer normally
spin coated Spin coating is a procedure used to deposit uniform thin films onto flat Substrate (printing), substrates. Usually a small amount of coating material is applied on the center of the substrate, which is either spinning at low speed or not spinning a ...
directly on the reflective layer. The label is printed on the lacquer layer, usually by
screen printing Screen printing is a printing technique where a mesh is used to transfer ink onto a Substrate (printing), substrate, except in areas made impermeable to the ink by a blocking stencil. A blade or squeegee is moved across the screen to fill the ...
or
offset printing Offset printing is a common printing technique in which the ink Ink is a gel, sol, or solution Image:SaltInWaterSolutionLiquid.jpg, Making a saline water solution by dissolving Salt, table salt (sodium chloride, NaCl) in water. The sal ...
. CD data is represented as tiny indentations known as ''pits'', encoded in a spiral track moulded into the top of the polycarbonate layer. The areas between pits are known as ''lands''. Each pit is approximately 100  nm deep by 500 nm wide, and varies from 850 nm to 3.5  µm in length. The distance between the tracks (the ''pitch'') is 1.6 µm. When playing an audio CD, a motor within the CD player spins the disc to a scanning velocity of 1.2–1.4 m/s (
constant linear velocity In optical storage, constant linear velocity (CLV) is a qualifier for the rated speed of an optical disc drive In computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes ...
, CLV)—equivalent to approximately 500 RPM at the inside of the disc, and approximately 200 RPM at the outside edge. The track on the CD begins at the inside and spirals outward so a disc played from beginning to end slows its rotation rate during playback. The program area is 86.05 cm2 and the length of the recordable spiral is With a scanning speed of 1.2 m/s, the playing time is 74 minutes, or 650 MB of data on a CD-ROM. A disc with data packed slightly more densely is tolerated by most players (though some old ones fail). Using a linear velocity of 1.2 m/s and a narrower track pitch of 1.5 µm increases the playing time to 80 minutes, and data capacity to 700 MB. A CD is read by focusing a 780 nm
wavelength In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase (waves), phase on the wave, such as two adjac ...

wavelength
(
near infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natur ...
)
semiconductor laser file:Diode laser.jpg, A packaged laser diode shown with a penny for scale file:Laser diode chip.jpg, The laser diode chip removed and placed on the eye of a needle for scale A laser diode (LD, also injection laser diode or ILD, or diode laser) ...
through the bottom of the polycarbonate layer. The change in height between pits and lands results in a difference in the way the light is reflected. Because the pits are indented into the top layer of the disc and are read through the transparent polycarbonate base, the pits form bumps when read. The laser hits the disc, casting a circle of light wider than the modulated spiral track reflecting partially from the lands and partially from the top of any bumps where they are present. As the laser passes over a pit (bump), its height means that the part of the light reflected from its peak is 1/2 wavelength out of phase with the light reflected from the land around it. This causes partial cancellation of the laser's reflection from the surface. By measuring the reflected intensity change with a
photodiode A photodiode is a semiconductor p–n junction device that converts light into an electric current, electrical current. The current is generated when photons are absorbed in the photodiode. Photodiodes may contain optical filters, built-in lense ...

photodiode
, a modulated signal is read back from the disc. To accommodate the spiral pattern of data, the laser is placed on a mobile mechanism within the disc tray of any CD player. This mechanism typically takes the form of a sled that moves along a rail. The sled can be driven by a
worm gear A worm drive is a gear arrangement in which a worm (which is a gear in the form of a screw A screw and a Bolt (fastener), bolt (see ''#Differentiation between bolt and screw, Differentiation between bolt and screw'' below) are similar type ...

worm gear
or
linear motor Synchronous linear motors are straightened versions of permanent magnet rotor motors A linear motor is an electric motor that has had its stator and rotor (electric), rotor "unrolled" thus instead of producing a torque (rotation) it produces a lin ...

linear motor
. Where a worm gear is used, a second shorter-throw linear motor, in the form of a coil and magnet, makes fine position adjustments to track eccentricities in the disk at high speed. Some CD drives (particularly those manufactured by Philips during the 1980s and early 1990s) use a swing arm similar to that seen on a gramophone. This mechanism allows the laser to read information from the center to the edge of a disc without having to interrupt the spinning of the disc itself. The pits and lands do ''not'' directly represent the 0's and 1's of
binary data Binary data is data Data are units of information Information can be thought of as the resolution of uncertainty; it answers the question of "What an entity is" and thus defines both its essence and the nature of its characteristics. Th ...
. Instead,
non-return-to-zero, inverted In telecommunication, a non-return-to-zero (NRZ) line code is a Binary coding, binary code in which ones are represented by one significant condition, usually a positive voltage, while zeros are represented by some other significant condition, usua ...
encoding is used: a change from either pit to land or land to pit indicates a 1, while no change indicates a series of 0's. There must be at least 2, and no more than 10 0's between each 1, which is defined by the length of the pit. This, in turn, is decoded by reversing the eight-to-fourteen modulation used in mastering the disc, and then reversing the cross-interleaved Reed–Solomon coding, finally revealing the raw data stored on the disc. These encoding techniques (defined in the '' Red Book'') were originally designed for CD Digital Audio, but they later became a standard for almost all CD formats (such as
CD-ROM A CD-ROM (, compact disc read-only memory) is a pre-pressed optical compact disc that contains data. Computers can read—but not write to or erase—CD-ROMs, i.e. it is a type of read-only memory. History During the 1990s, CD-ROMs were popul ...
).


Integrity

CDs are susceptible to damage during handling and from environmental exposure. Pits are much closer to the label side of a disc, enabling defects and contaminants on the clear side to be out of focus during playback. Consequently, CDs are more likely to suffer damage on the label side of the disc. Scratches on the clear side can be repaired by refilling them with similar refractive plastic or by careful polishing. The edges of CDs are sometimes incompletely sealed, allowing gases and liquids to enter the CD and corrode the metal reflective layer and/or interfere with the focus of the laser on the pits, a condition known as
disc rotDisc rot is the tendency of CD or DVD or other optical discs to become unreadable because of physical or chemical deterioration. The causes include oxidation of the reflective layer, physical scuffing and abrasion of disc, reactions with contaminant ...

disc rot
.Council on Library and Information Resources
Conditions that Affect CDs and DVDs
The fungus ''
Geotrichum candidum ''Geotrichum candidum'' is a fungus A fungus (plural: fungi or funguses) is any member of the group of Eukaryote, eukaryotic organisms that includes microorganisms such as yeasts and Mold (fungus), molds, as well as the more familiar mushroo ...
'' has been found—under conditions of high heat and humidity—to consume the polycarbonate plastic and aluminium found in CDs. The
data integrityData integrity is the maintenance of, and the assurance of, data accuracy and consistency over its entire life-cycle and is a critical aspect to the design, implementation, and usage of any system that stores, processes, or retrieves data. The term ...
of compact discs can be measured using surface error scanning, which is able to measure the rates of different types of data errors, known as ''C1'', '' C2'', ''CU'' and extended (finer-grain) error measurements known as ''E11'', ''E12'', ''E21'', ''E22'', ''E31'' and ''E32'', of which higher rates indicate a possibly damaged or unclean data surface, low media quality, and
recordable media On a reel-to-reel tape recorder (Sony TC-630), the recorder is data storage equipment and the magnetic tape is a data storage medium. Data Data are units of information Information can be thought of as the resolution of uncertaint ...

recordable media
written to by a malfunctioning CD writer. Error scanning can reliably predict data losses caused by media deteriorating. Support of error scanning varies among vendors and models of
optical disc drive In computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithmic processes and development of both computer hardware , hardware and ...
s, and ''extended'' error scanning (known as ''"advanced error scanning"'' in Nero DiscSpeed) has only been available on Plextor and some BenQ optical drives so far, as of 2020.


Disc shapes and diameters

The digital data on a CD begins at the center of the disc and proceeds toward the edge, which allows adaptation to the different size formats available. Standard CDs are available in two sizes. By far, the most common is in diameter, with a 74- or 80-minute audio capacity and a 650 or 700 MB (737,280,000-byte) data capacity. Discs are thick, with a center hole. The size of the hole isnt random, but chosen by Joop Sinjou and based on a dutch 10 cent coin: a "
dubbeltje Image:Netherlands 10 cents 1942 reverse.jpg, 100px, Obverse 10 cent, 1942. A ''dubbeltje'' () is a small former Netherlands, Dutch coin, originally made of silver, with a value of a tenth of a Dutch guilder. The 10-euro-cent coin is currently als ...
". Philips/Sony were smart to patent the physical dimensions to claim copyright. Philips decided to have a 110 Hz ' eigentrilling' on the discs whilst Sony chose 90 Hz. The discrepancy caused later issues on the CD Walkman. The official Philips history says the capacity was specified by Sony executive
Norio Ohga , otherwise spelled ''Norio Oga'' (January 29, 1930 – April 23, 2011), was the former president and chairman of Sony Corporation, credited with spurring the development of the compact disc as a commercially viable audio format. Biography Early ...
to be able to contain the entirety of Beethoven's Ninth Symphony on one disc. This is a myth according to
Kees Immink Kornelis Antonie "Kees" Schouhamer Immink (born 18 December 1946) is a Netherlands, Dutch scientist, inventor, and entrepreneur, who pioneered and advanced the era of digital audio, video, and data recording, including popular digital media such a ...
, as the EFM code format had not yet been decided in December 1979, when the decision to adopt the 120 mm was made. The adoption of EFM in June 1980 allowed 30 percent more playing time that would have resulted in 97 minutes for 120 mm diameter or 74 minutes for a disc as small as . Instead, however, the information density was lowered by 30 percent to keep the playing time at 74 minutes. The 120 mm diameter has been adopted by subsequent formats, including
Super Audio CD Super Audio CD (SACD) is a read-only optical disc format for audio storage, introduced in 1999. It was developed jointly by Sony is a Japanese Multinational corporation, multinational conglomerate (company), conglomerate corporatio ...
,
DVD The DVD (common abbreviation for Digital Video Disc or Digital Versatile Disc) is a digital optical disc data storage format invented and developed in 1995 and released in late 1996. The medium can store any kind of digital data and was wide ...

DVD
,
HD DVD HD DVD (short for High Definition Digital Versatile Disc) is an obsolete high-density optical disc format for storing data and playback of high-definition video. Supported principally by Toshiba, HD DVD was envisioned to be the successor to the ...
, and
Blu-ray The Blu-ray Disc (BD), often known simply as Blu-ray, is a digital optical disc storage format. It is designed to supersede the DVD format, capable of storing several hours of video in high-definition video (HDTV 720p and 1080p). The main ap ...
Disc. The diameter discs ("
Mini CD 280px, Business card CD Mini CDs, or pocket CDs, are CDs with a smaller diameter and one-third the storage capacity of a standard 120 mm disc. Formats Amongst the various formats are the * Mini CD single, a small disc. The format is main ...
s") can hold up to 24 minutes of music or 210 MB.


Logical format


Audio CD

The logical format of an audio CD (officially Compact Disc Digital Audio or CD-DA) is described in a document produced in 1980 by the format's joint creators, Sony and Philips. The document is known colloquially as the ''Red Book''
CD-DA Compact Disc Digital Audio (CDDA or CD-DA), also known as Digital Audio Compact Disc or simply as Audio CD, is the standardization, standard format for audio compact discs. The standard is defined in the ''Red Book'', one of a series of Rainbow ...
after the color of its cover. The format is a two-channel 16-bit
PCM Pulse-code modulation (PCM) is a method used to digitally represent sampled analog signal An analog signal is any continuous signal for which the time-varying feature of the signal is a representation of some other time-varying quantity ...
encoding at a 44.1 kHz
sampling rate Image:Signal Sampling.svg, 300px, Signal sampling representation. The continuous signal S(t) is represented with a green colored line while the discrete samples are indicated by the blue vertical lines. In signal processing, sampling is the reducti ...
per channel. Four-channel sound was to be an allowable option within the ''Red Book'' format, but has never been implemented.
Monaural Monaural or monophonic sound reproduction (often shortened to mono) is sound intended to be heard as if it were emanating from one position. This contrasts with stereophonic sound or ''stereo'', which uses two separate audio channels to reproduce ...

Monaural
audio has no existing standard on a ''Red Book'' CD; thus, the mono source material is usually presented as two identical channels in a standard ''Red Book'' stereo track (i.e., mirrored mono); an
MP3 CD A compressed audio optical disc, MP3 CD, or MP3 CD-ROM or MP3 DVD is an optical disc drive. (CD-R), showing characteristic iridescence. In computing Computing is any goal-oriented activity requiring, benefiting from, or creating computi ...
, however, can have audio file formats with mono sound.
CD-Text 100px, Compact Disc Text CD-Text is an extension of the Red Book Compact Disc#REDIRECT Compact disc {{redirect category shell, {{R move {{R from other capitalization, printworthy {{R yes print ... specifications standard for audio CDs. It all ...
is an extension of the ''Red Book'' specification for an audio CD that allows for the storage of additional text information (e.g., album name, song name, artist) on a standards-compliant audio CD. The information is stored either in the lead-in area of the CD, where there are roughly five kilobytes of space available, or in the
subcode Subcode or subchannel data (called "control bytes" in the CD-ROM A CD-ROM (, compact disc read-only memory) is a pre-pressed optical compact disc that contains data. Computers can read—but not write to or erase—CD-ROMs, i.e. it is a type of ...
channels R to W on the disc, which can store about 31 megabytes. Compact Disc + Graphics is a special audio compact disc that contains graphics data in addition to the audio data on the disc. The disc can be played on a regular audio CD player, but when played on a special CD+G player, it can output a graphics signal (typically, the CD+G player is hooked up to a television set or a computer monitor); these graphics are almost exclusively used to display lyrics on a television set for
karaoke Karaoke (; ; , clipped compound of Japanese ''kara'' "empty" and ''ōkesutora'' "orchestra") is a type of interactive entertainment usually offered in clubs and bars, where people sing along to recorded music using a microphone A micro ...

karaoke
performers to sing along with. The CD+G format takes advantage of the channels R through W. These six bits store the graphics information. CD + Extended Graphics (CD+EG, also known as CD+XG) is an improved variant of the Compact Disc + Graphics (CD+G) format. Like CD+G, CD+EG uses basic CD-ROM features to display text and video information in addition to the music being played. This extra data is stored in
subcode Subcode or subchannel data (called "control bytes" in the CD-ROM A CD-ROM (, compact disc read-only memory) is a pre-pressed optical compact disc that contains data. Computers can read—but not write to or erase—CD-ROMs, i.e. it is a type of ...
channels R-W. Very few, if any, CD+EG discs have been published.


Super Audio CD

Super Audio CD (SACD) is a high-resolution read-only
optical Optics is the branch of physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space and time, and the related entities ...
audio disc format that was designed to provide higher-fidelity digital audio reproduction than the ''Red Book''. Introduced in 1999, it was developed by Sony and Philips, the same companies that created the ''Red Book''. SACD was in a
format war A format war is a competition between similar but mutually incompatible technical standards that compete for the same market, such as for data storage device On a reel-to-reel tape recorder (Sony TC-630), the recorder is data storage equipme ...
with
DVD-Audio DVD-Audio (commonly abbreviated as DVD-A) is a digital format for delivering high-fidelity audio content on a DVD The DVD (common abbreviation for Digital Video Disc or Digital Versatile Disc) is a digital optical disc data storage for ...
, but neither has replaced audio CDs. The SACD standard is referred to as the ''Scarlet Book'' standard. Titles in the SACD format can be issued as hybrid discs; these discs contain the SACD audio stream as well as a standard audio CD layer which is playable in standard CD players, thus making them backward compatible.


CD-MIDI

CD-
MIDI File:Synth rack @ Choking Sun Studio.jpg, alt=Several rack-mounted synthesizers that share a single controller, Using MIDI, a single controller (often a musical keyboard, as pictured here) can play multiple electronic instruments, which incre ...
is a format used to store music-performance data, which upon playback is performed by electronic instruments that synthesize the audio. Hence, unlike the original ''Red Book'' CD-DA, these recordings are not digitally sampled audio recordings. The CD-MIDI format is defined as an extension of the original ''Red Book''.


CD-ROM

For the first few years of its existence, the CD was a medium used purely for audio. However, in 1988, the ''Yellow Book''
CD-ROM A CD-ROM (, compact disc read-only memory) is a pre-pressed optical compact disc that contains data. Computers can read—but not write to or erase—CD-ROMs, i.e. it is a type of read-only memory. History During the 1990s, CD-ROMs were popul ...
standard was established by Sony and Philips, which defined a non-volatile optical data
computer data storage File:Maxell DVD-RW 4.7GB crop 20051120.jpg, A spindle of DVD-RWs Computer data storage is a technology consisting of computer components and Data storage device, recording media that are used to retain digital data (computing), data. It is a ...
medium using the same physical format as audio compact discs, readable by a computer with a CD-ROM drive.


Video CD

Video CD (VCD, View CD, and Compact Disc digital video) is a standard digital format for storing video media on a CD. VCDs are playable in dedicated VCD players, most modern
DVD-Video DVD-Video is a consumer video format used to store digital video on DVD The DVD (common abbreviation for Digital Video Disc or Digital Versatile Disc) is a digital optical disc data storage format invented and developed in 1995 and release ...

DVD-Video
players, personal computers, and some video game consoles. The VCD standard was created in 1993 by Sony, Philips,
MatsushitaMatsushita (written: lit. "below the pine tree") is a Japanese surname. Notable people with the surname include: *Daisuke Matsushita (born 1981), a former Japanese football player *Hiroyuki Matsushita, Hiro Matsushita (born 1961), former Japanese C ...

Matsushita
, and
JVC The , usually referred to as JVC or the Japan Victor Company, is a Japanese brand owned by JVCKenwood corporation. Founded in 1927, the company is best known for introducing Japan's first televisions and for developing the Video Home System (VH ...

JVC
and is referred to as the ''White Book'' standard. Overall picture quality is intended to be comparable to
VHS VHS (Video Home System) is a standard Standard may refer to: Flags * Colours, standards and guidons * Standard (flag), a type of flag used for personal identification Norm, convention or requirement * Standard (metrology), an object t ...

VHS
video. Poorly compressed VCD video can sometimes be of lower quality than VHS video, but VCD exhibits block artifacts rather than analog noise and does not deteriorate further with each use. 352×240 (or SIF) resolution was chosen because it is half the vertical and half the horizontal resolution of the NTSC video. 352×288 is similarly one-quarter PAL/SECAM resolution. This approximates the (overall) resolution of an analog VHS tape, which, although it has double the number of (vertical) scan lines, has a much lower horizontal resolution.


Super Video CD

Super Video CD (Super Video Compact Disc or SVCD) is a format used for storing video media on standard compact discs. SVCD was intended as a successor to VCD and an alternative to DVD-Video and falls somewhere between both in terms of technical capability and picture quality. SVCD has two-thirds the
resolution Resolution(s) may refer to: Common meanings * Resolution (debate), the statement which is debated in policy debate * Resolution (law), a written motion adopted by a deliberative body * New Year's resolution, a commitment that an individual make ...
of DVD, and over 2.7 times the resolution of VCD. One CD-R disc can hold up to 60 minutes of standard-quality SVCD-format video. While no specific limit on SVCD video length is mandated by the specification, one must lower the video bit rate, and therefore quality, to accommodate very long videos. It is usually difficult to fit much more than 100 minutes of video onto one SVCD without incurring a significant quality loss, and many hardware players are unable to play video with an instantaneous bit rate lower than 300 to 600
kilobit The kilobit is a multiple of the unit bit The bit is a basic unit of information in computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of ...
s per second.


Photo CD

Photo CD is a system designed by
Kodak The Eastman Kodak Company (referred to simply as Kodak ) is an American public company that produces various products related to its historic basis in analogue photography. The company is headquartered in Rochester, New York, and is incorpora ...

Kodak
for digitizing and storing photos on a CD. Launched in 1992, the discs were designed to hold nearly 100 high-quality images, scanned prints, and slides using special proprietary encoding. Photo CDs are defined in the ''Beige Book'' and conform to the
CD-ROM XA A CD-ROM (, compact disc read-only memory) is a pre-pressed optical compact disc#REDIRECT Compact disc {{redirect category shell, {{R move {{R from other capitalization, printworthy {{R yes print ... that contains data Data are units of in ...
and CD-i Bridge specifications as well. They are intended to play on CD-i players, Photo CD players, and any computer with suitable software (irrespective of
operating system An operating system (OS) is system software that manages computer hardware, computer software, software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), sch ...

operating system
). The images can also be printed out on photographic paper with a special Kodak machine. This format is not to be confused with Kodak Picture CD, which is a consumer product in CD-ROM format.


CD-i

The Philips '' Green Book'' specifies a standard for interactive multimedia compact discs designed for
CD-i The Compact Disc-Interactive (CD-I, later CD-i) is a digital Digital usually refers to something using digits, particularly binary digits. Technology and computing Hardware *Digital electronics Digital electronics is a field of electronics ...

CD-i
players (1993). CD-i discs can contain audio tracks that can be played on regular
CD player A CD player is an electronic device that plays audio compact discs, which are a digital audio, digital optical disc data storage device, data storage format. CD players were first sold to consumers in 1982. CDs typically contain recordings of au ...

CD player
s, but CD-i discs are not compatible with most
CD-ROM A CD-ROM (, compact disc read-only memory) is a pre-pressed optical compact disc that contains data. Computers can read—but not write to or erase—CD-ROMs, i.e. it is a type of read-only memory. History During the 1990s, CD-ROMs were popul ...
drives and software. The
CD-i ReadyCD-i Ready is a compact disc format for mixing audio and data content on a CD. It was developed by Phillips in 1991, based on the CD-i format. The CD-i Ready format uses a particular technique to get audio CD players to skip over the CD-i software ...
specification was later created to improve compatibility with audio CD players, and the
CD-i Bridge The White Book refers to a standard of compact disc that stores not only sound but also still pictures and motion video. It was released in 1993 by Sony, Philips Consumer Electronics, Philips, Matsushita Electric Industrial Co., Matsushita, and JV ...
specification was added to create CD-i compatible discs that can be accessed by regular CD-ROM drives.


CD-i Ready

Philips defined a format similar to CD-i called
CD-i ReadyCD-i Ready is a compact disc format for mixing audio and data content on a CD. It was developed by Phillips in 1991, based on the CD-i format. The CD-i Ready format uses a particular technique to get audio CD players to skip over the CD-i software ...
, which puts CD-i software and data into the
pregap The pregap on a Red Book audio CD is the portion of the audio track that precedes "index Index may refer to: Arts, entertainment, and media Fictional entities * Index (''A Certain Magical Index''), a character in the light novel series ''A Cert ...
of track 1. This format was supposed to be more compatible with older audio CD players.


Enhanced Music CD (CD+)

Enhanced Music CD, also known as CD Extra or CD Plus, is a format which combines audio tracks and on the same disc by putting audio tracks in a first session and data in a second session. It was developed by Philips and Sony, and it is defined in the ''
Blue Book A blue book or bluebook is an almanac An almanac (also spelled ''almanack'' and ''almanach'') is an annual publicationAnnual publications, more often simply called annuals, are periodical publications appearing regularly once per year."Annuals", ...
''.


VinylDisc

VinylDisc is the hybrid of a standard audio CD and the
vinyl record A phonograph disc record (also known as a gramophone disc record, especially in British English British English (BrE) is the standard dialect of the English language English is a West Germanic languages, West Germanic language fi ...
. The vinyl layer on the disc's label side can hold approximately three minutes of music.


Manufacture

In 1995, material costs were 30 cents for the jewel case and 10 to 15 cents for the CD. Wholesale cost of CDs was $0.75 to $1.15, while the typical retail price of a prerecorded music CD was $16.98. On average, the store received 35 percent of the retail price, the record company 27 percent, the artist 16 percent, the manufacturer 13 percent, and the distributor 9 percent. When 8-track cartridges,
compact cassette The Compact Cassette or Musicassette (MC), also commonly called the tape cassette, cassette tape, audio cassette, or simply tape or cassette, is an analog magnetic tape Magnetic tape is a medium for magnetic recording, made of a thin, mag ...

compact cassette
s, and CDs were introduced, each was marketed at a higher price than the format they succeeded, even though the cost to produce the media was reduced. This was done because the apparent value increased. This continued from
phonograph record A phonograph disc record (also known as a gramophone disc record, especially in British English British English (BrE) is the standard dialect of the English language English is a West Germanic languages, West Germanic language fi ...
s to CDs, but was broken when
Apple An apple is an edible fruit produced by an apple tree (''Malus domestica''). Apple fruit tree, trees are agriculture, cultivated worldwide and are the most widely grown species in the genus ''Malus''. The tree originated in Central Asia, wher ...
marketed MP3s for $0.99, and albums for $9.99. The incremental cost, though, to produce an MP3 is negligible.


Writable compact discs


Recordable CD

Recordable Compact Discs,
CD-R CD-R (COMPACT DISC – Recordable) is a digital optical disc storage format. A CD-R disc is a compact disc#REDIRECT Compact disc {{redirect category shell, {{R move {{R from other capitalization, printworthy {{R yes print ... that can be ...

CD-R
s, are injection-molded with a "blank" data spiral. A photosensitive dye is then applied, after which the discs are metalized and lacquer-coated. The write laser of the
CD recorder In computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithmic processes and development of both computer hardware , hardware and ...
changes the color of the dye to allow the read laser of a standard
CD player A CD player is an electronic device that plays audio compact discs, which are a digital audio, digital optical disc data storage device, data storage format. CD players were first sold to consumers in 1982. CDs typically contain recordings of au ...

CD player
to see the data, just as it would with a standard stamped disc. The resulting discs can be read by most CD-ROM drives and played in most audio CD players. CD-Rs follow the ''Orange Book'' standard. CD-R recordings are designed to be permanent. Over time, the dye's physical characteristics may change causing read errors and data loss until the reading device cannot recover with error correction methods. Errors can be predicted using surface error scanning. The design life is from 20 to 100 years, depending on the quality of the discs, the quality of the writing drive, and storage conditions. However, testing has demonstrated such degradation of some discs in as little as 18 months under normal storage conditions. This failure is known as
disc rotDisc rot is the tendency of CD or DVD or other optical discs to become unreadable because of physical or chemical deterioration. The causes include oxidation of the reflective layer, physical scuffing and abrasion of disc, reactions with contaminant ...

disc rot
, for which there are several, mostly environmental, reasons. The recordable audio CD is designed to be used in a consumer audio CD recorder. These consumer audio CD recorders use SCMS (
Serial Copy Management SystemThe Serial Copy Management System (SCMS) is a copy protection Copy protection, also known as content protection, copy prevention and copy restriction, describes measures to enforce copyright by preventing the reproduction of software, films, music, ...
), an early form of
digital rights management Digital rights management (DRM) tools or technological protection measures (TPM) are a set of access control In the fields of physical security and information security, access control (AC) is the selective restriction of access to a place o ...
(DRM), to conform to the AHRA (
Audio Home Recording Act The Audio Home Recording Act of 1992 (AHRA) amended the United States copyright law by adding Chapter 10, "Digital Audio Recording Devices and Media". The act enabled the release of recordable digital formats such as Sony and Philips' Digital Audio ...
). The Recordable Audio CD is typically somewhat more expensive than CD-R due to lower production volume and a 3 percent AHRA royalty used to compensate the music industry for the making of a copy. High-capacity recordable CD is a higher-density recording format that can hold 20% more data than of conventional discs. The higher capacity is incompatible with some recorders and recording software.


ReWritable CD

CD-RW CD-RW (Compact Disc-ReWritable) is a digital optical disc storage format introduced in 1997. A CD-RW compact disc (CD-RWs) can be written, read, erased, and re-written. CD-RWs, as opposed to CDs, require specialized readers that have sensitiv ...
is a re-recordable medium that uses a metallic alloy instead of a dye. The write laser, in this case, is used to heat and alter the properties (amorphous vs. crystalline) of the alloy, and hence change its reflectivity. A CD-RW does not have as great a difference in reflectivity as a pressed CD or a CD-R, and so many earlier CD audio players ''cannot'' read CD-RW discs, although ''most'' later CD audio players and stand-alone
DVD The DVD (common abbreviation for Digital Video Disc or Digital Versatile Disc) is a digital optical disc data storage format invented and developed in 1995 and released in late 1996. The medium can store any kind of digital data and was wide ...

DVD
players can. CD-RWs follow the ''Orange Book'' standard. The ReWritable Audio CD is designed to be used in a consumer audio CD recorder, which will not (without modification) accept standard CD-RW discs. These consumer audio CD recorders use the
Serial Copy Management SystemThe Serial Copy Management System (SCMS) is a copy protection Copy protection, also known as content protection, copy prevention and copy restriction, describes measures to enforce copyright by preventing the reproduction of software, films, music, ...
(SCMS), an early form of
digital rights management Digital rights management (DRM) tools or technological protection measures (TPM) are a set of access control In the fields of physical security and information security, access control (AC) is the selective restriction of access to a place o ...
(DRM), to conform to the United States'
Audio Home Recording Act The Audio Home Recording Act of 1992 (AHRA) amended the United States copyright law by adding Chapter 10, "Digital Audio Recording Devices and Media". The act enabled the release of recordable digital formats such as Sony and Philips' Digital Audio ...
(AHRA). The ReWritable Audio CD is typically somewhat more expensive than CD-R due to (a) lower volume and (b) a 3 percent AHRA royalty used to compensate the music industry for the making of a copy.


Copy protection

The ''Red Book'' audio specification, except for a simple "anti-copy" statement in the subcode, does not include any copy protection mechanism. Known at least as early as 2001, attempts were made by record companies to market "copy-protected" non-standard compact discs, which cannot be Ripping, ripped, or copied, to hard drives or easily converted to other formats (like FLAC, MP3 or Vorbis). One major drawback to these copy-protected discs is that most will not play on either computer CD-ROM drives or some standalone CD players that use CD-ROM mechanisms. Philips has stated that such discs are not permitted to bear the trademarked ''Compact Disc Digital Audio'' logo because they violate the ''Red Book'' specifications. Numerous copy-protection systems have been countered by readily available, often free, software, or even by simply turning off automatic AutoPlay to prevent the running of the DRM executable program.


See also


References


Further reading

* Ecma International
''Standard ECMA-130: Data Interchange on Read-only 120 mm Optical Data Disks (CD-ROM)''
2nd edition (June 1996). * Pohlmann, Kenneth C. (1992)
''The Compact Disc Handbook''
Middleton, Wisconsin: A-R Editions. . * Peek, Hans et al. (2009
''Origins and Successors of the Compact Disc''
Springer Science+Business Media B.V. . * Peek, Hans B.
''The emergence of the compact disc''
IEEE Communications Magazine, Jan. 2010, pp. 10–17. * Heitaro Nakajima, Nakajima, Heitaro; Ogawa, Hiroshi (1992
Disc Technology''
Tokyo, Ohmsha Ltd. . * Barry, Robert (2020). ''Compact Disc (Object Lessons)''. New York: Bloomsbury. .


External links


Video
How Compact Discs are Manufactured
CD-Recordable FAQ
Exhaustive basics on CD-Recordable's



nbsp;– published by
Philips Koninklijke Philips N.V. (literally ''Royal Philips'', commonly shortened to Philips, stylized in its logo as PHILIPS) is a Dutch multinational conglomerate corporation that was founded in Eindhoven. Since 1997, it has been mostly headquarte ...

Philips
in 2005
Patent History CD Disc
nbsp;– published by
Philips Koninklijke Philips N.V. (literally ''Royal Philips'', commonly shortened to Philips, stylized in its logo as PHILIPS) is a Dutch multinational conglomerate corporation that was founded in Eindhoven. Since 1997, it has been mostly headquarte ...

Philips
in 2003
Sony History, Chapter 8, This is the replacement of Gramophone record ! (第8章 レコードに代わるものはこれだ)
nbsp;–
Sony is a Japanese Multinational corporation, multinational conglomerate (company), conglomerate corporation headquartered in Kōnan, Minato, Tokyo. The company operates as one of the world's largest manufacturers of consumer and professional ...

Sony
website in Japanese
Popularized History on Soundfountain

A Media History of the Compact Disc
(1-hour podcast interview) {{Authority control Compact disc, 120 mm discs Rotating disc computer storage media Audio storage Digital audio storage Video storage Consumer electronics Audiovisual introductions in 1982 Joint ventures Dutch inventions Japanese inventions Information technology in the Netherlands Science and technology in the Netherlands Science and technology in Japan Objects with holes Home video