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The compact disc (CD) is a digital
optical disc In computing and optical disc recording technologies, an optical disc (OD) is a flat, usually circular disc that encodes binary data (bits) in the form of pits and lands on a special material, often aluminum, on one of its flat surfaces. ...
data storage format that was co-developed by
Philips Koninklijke Philips N.V. (), commonly shortened to Philips, is a Dutch multinational conglomerate corporation that was founded in Eindhoven in 1891. Since 1997, it has been mostly headquartered in Amsterdam, though the Benelux headquarters i ...
and
Sony , commonly stylized as SONY, is a Japanese multinational conglomerate corporation headquartered in Minato, Tokyo, Japan. As a major technology company, it operates as one of the world's largest manufacturers of consumer and professiona ...
to store and play digital audio recordings. In August 1982, the first compact disc was manufactured. It was then released in October 1982 in Japan and branded as '' Digital Audio Compact Disc''. The format was later adapted (as CD-ROM) for general-purpose data storage. Several other formats were further derived, 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 that can be written once and read arbitrarily many times. CD-R discs (CD-Rs) are readable by most CD readers manufactured prior to the i ...
), 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 sensi ...
),
Video CD Video CD (abbreviated as VCD, and also known as Compact Disc Digital Video) is a home video format and the first format for distributing films on standard optical discs. The format was widely adopted in Southeast Asia, Central Asia and the ...
(VCD), Super Video CD (SVCD), Photo CD, Picture CD, Compact Disc-Interactive ( CD-i) and Enhanced Music CD. Standard CDs have a diameter of and are designed to hold up to 74 minutes of uncompressed stereo digital audio or about 650  MiB of data. Capacity is routinely extended to 80 minutes and 700  MiB by arranging data more closely on the same sized disc. The Mini CD has various diameters ranging from ; they are sometimes used for
CD single A CD single (sometimes abbreviated to CDS) is a music single in the form of a compact disc. The standard in the Red Book for the term ''CD single'' is an 8 cm (3-inch) CD (or Mini CD). It now refers to any single recorded onto a CD of any si ...
s, storing up to 24 minutes of audio, or delivering device drivers. 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 microcomputer whose size, capabilities, and price make it feasible for individual use. Personal computers are intended to be operated directly by an end user, rather than by a computer expert or tec ...
hard disk drive A hard disk drive (HDD), hard disk, hard drive, or fixed disk is an electro-mechanical data storage device that stores and retrieves digital data using magnetic storage with one or more rigid rapidly rotating platters coated with magne ...
, which would typically hold 10 MiB. 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 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 and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It ha ...
or, more rarely,
gold Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile me ...
is applied to the surface, making it reflective. The metal is protected by a film of lacquer normally spin coated directly on the reflective layer. The label is printed on the lacquer layer, usually by screen printing or offset printing. 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, and may also be applied to the writing speed of recordable discs. CLV implies that the angular velocity (i.e. rpm) varies during an ...
, 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 MiB 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 MiB. 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 on the wave, such as two adjacent crests, t ...
(
near infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from arou ...
)
semiconductor laser 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) is a semiconductor device similar to a light-emitting diode in which a diode pumped directly with e ...
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 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) meshes with a worm wheel (which is similar in appearance to a spur gear). The two elements are also called the worm screw and worm gear. The terminol ...
or 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 0s and 1s of
binary data Binary data is data whose unit can take on only two possible states. These are often labelled as 0 and 1 in accordance with the binary numeral system and Boolean algebra. Binary data occurs in many different technical and scientific fields, wher ...
. Instead,
non-return-to-zero, inverted In telecommunication, a non-return-to-zero (NRZ) line code is a binary code in which ones are represented by one significant condition, usually a positive voltage, while zeros are represented by some other significant condition, usually a negati ...
encoding is used: a change from either pit to land or land to pit indicates a 1, while no change indicates a series of 0s. There must be at least two, and no more than ten 0s between each 1, which is defined by the length of the pit. This, in turn, is decoded by reversing the
eight-to-fourteen modulation Eight-to-fourteen modulation (EFM) is a data encoding technique – formally, a ''line code'' – used by compact discs (CD), laserdiscs (LD) and pre- Hi-MD MiniDiscs. EFMPlus is a related code, used in DVDs and Super Audio CDs (SACDs). EFM and ...
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).


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 rot Disc rot is the tendency of CD, 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 contamina ...
.Council on Library and Information Resources
Conditions that Affect CDs and DVDs
The fungus ''
Geotrichum candidum ''Geotrichum candidum'' is a fungus which is a member of the human microbiome, notably associated with skin, sputum, and faeces where it occurs in 25–30% of specimens. It is common in soil and has been isolated from soil collected around the w ...
'' has been found—under conditions of high heat and humidity—to consume the polycarbonate plastic and aluminium found in CDs. The
data integrity Data 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 ter ...
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, deteriorating media and
recordable media Data storage is the recording (storing) of information (data) in a storage medium. Handwriting, phonographic recording, magnetic tape, and optical discs are all examples of storage media. Biological molecules such as RNA and DNA are conside ...
written to by a malfunctioning
CD writer In computing, an optical disc drive is a disk drive, disc drive that uses laser light or electromagnetic waves within or near the visible light spectrum as part of the process of reading or writing data to or from optical discs. Some drives ...
. Error scanning can reliably predict data losses caused by media deteriorating. Support of error scanning differs between vendors and models of optical disc drives, and ''extended'' error scanning (known as ''"advanced error scanning"'' in Nero DiscSpeed) has only been available on
Plextor Plextor (styled PLEXTOR) ( zh, 浦科特; ja, プレクスター) is a Taiwanese (formerly Japanese) consumer electronics brand, best known for solid-state drives and optical disc drives. Company The brand name Plextor was used for all products ...
and some
BenQ BenQ Corporation (; ) is a Taiwanese multinational company that sells and markets technology products, consumer electronics, computing and communications devices under the "BenQ" brand name, which stands for the company slogan ''Bringing Enj ...
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 sizes 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 MiB (737,280,000-byte) data capacity. Discs are thick, with a center hole. The size of the hole was chosen by Joop Sinjou and based on a Dutch 10-cent coin: a
dubbeltje A ''dubbeltje'' () is a small former Dutch coin, originally made of silver, with a value of a tenth of a Dutch guilder. The 10-euro-cent coin is currently also called a dubbeltje in the Netherlands. The name "dubbeltje" is the diminutive for ...
. Philips/Sony patented the physical dimensions. 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 Earl ...
to be able to contain the entirety of
Beethoven's Ninth Symphony The Symphony No. 9 in D minor, Op. 125, is a choral symphony, the final complete symphony by Ludwig van Beethoven, composed between 1822 and 1824. It was first performed in Vienna on 7 May 1824. The symphony is regarded by many critics and musi ...
on one disc. This is a myth according to Kees Immink, as the EFM code format had not yet been decided in December 1979, when the 120 mm size was adopted. 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 an optical disc format for audio storage introduced in 1999. It was developed jointly by Sony and Philips Electronics and intended to be the successor to the Compact Disc (CD) format. The SACD format allows multiple a ...
,
DVD The DVD (common abbreviation for Digital Video Disc or Digital Versatile Disc) is a digital optical disc data storage format. It was invented and developed in 1995 and first released on November 1, 1996, in Japan. The medium can store any kind ...
,
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 data storage format. It was invented and developed in 2005 and released on June 20, 2006 worldwide. It is designed to supersede the DVD format, and capable of st ...
Disc. The diameter discs (" Mini CDs") can hold up to 24 minutes of music or 210 MiB.


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 standard format for audio compact discs. The standard is defined in the ''Red Book'', one of a series of Rainbow Books (named ...
after the color of its cover. The format is a two-channel 16-bit PCM encoding at a 44.1 kHz
sampling rate In signal processing, sampling is the reduction of a continuous-time signal to a discrete-time signal. A common example is the conversion of a sound wave to a sequence of "samples". A sample is a value of the signal at a point in time and/or s ...
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 reproduc ...
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, however, can have audio file formats with mono sound.
CD-Text CD-Text is an extension of the Red Book Compact Disc specifications standard for audio CDs. It allows storage of additional information (e.g. album name, song name, and artist name) on a standards-compliant audio CD. The specification for CD ...
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 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. The music i ...
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 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 that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultravio ...
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 devices and recording formats for electronic media. It is often characterized by political an ...
with
DVD-Audio DVD-Audio (commonly abbreviated as DVD-A) is a digital format for delivering high-fidelity audio content on a DVD. DVD-Audio uses most of the storage on the disc for high-quality audio and is not intended to be a video delivery format. The st ...
, 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 MIDI (; Musical Instrument Digital Interface) is a technical standard that describes a communications protocol, digital interface, and electrical connectors that connect a wide variety of electronic musical instruments, computers, and ...
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 standard was established by Sony and Philips, which defined a non-volatile optical data
computer data storage Computer data storage is a technology consisting of computer components and recording media that are used to retain digital data. It is a core function and fundamental component of computers. The central processing unit (CPU) of a compute ...
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 players, personal computers, and some video game consoles. The VCD standard was created in 1993 by Sony, Philips, Matsushita, and JVC and is referred to as the ''White Book'' standard. Overall picture quality is intended to be comparable to 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 In Norse mythology, Sif (Old Norse: ) is a golden-haired goddess associated with earth. Sif is attested in the ''Poetic Edda'', compiled in the 13th century from earlier traditional sources, and the ''Prose Edda'', written in the 13th century ...
) 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 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 for digital information or computer storage. The prefix '' kilo-'' (symbol k) is defined in the International System of Units (SI) as a multiplier of 103 (1 thousand), and therefore, :1 kilobit = = 10 ...
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 incorpor ...
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 type of read-only memory consisting of a pre-pressed optical compact disc that contains data. Computers can read—but not write or erase—CD-ROMs. Some CDs, called enhanced CDs, hold both comput ...
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, software resources, and provides common services for computer programs. Time-sharing operating systems schedule tasks for efficient use of the system and may also i ...
). 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 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 optical disc data storage format. CD players were first sold to consumers in 1982. CDs typically contain recordings of audio material such as music or audio ...
s, but CD-i discs are not compatible with most CD-ROM drives and software. The
CD-i Ready CD-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 certain technique to get audio CD players to skim over the CD-i software an ...
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, Matsushita, and JVC. These discs, most commonly found in Asia, are usually called ...
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 Ready CD-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 certain technique to get audio CD players to skim over the CD-i software an ...
, 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 01" for a given track in the table of contents (TOC). The pregap ("index 00") is typically two seconds long and usually, but not always, contains silence. P ...
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 data tracks 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, buyer's guide or other compilation of statistics and information. The term dates back to the 15th century, when large blue velvet-covered books were used for record-keeping by the Parliament of England. The ...
''.


VinylDisc

VinylDisc is the hybrid of a standard audio CD and the
vinyl record A phonograph record (also known as a gramophone record, especially in British English), or simply a record, is an analog sound storage medium in the form of a flat disc with an inscribed, modulated spiral groove. The groove usually starts nea ...
. 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 cassettes, 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 perceived value increased. This continued from phonograph records to CDs, but was broken when
Apple An apple is an edible fruit produced by an apple tree (''Malus domestica''). Apple trees are cultivated worldwide and are the most widely grown species in the genus ''Malus''. The tree originated in Central Asia, where its wild ancestor, ' ...
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 that can be written once and read arbitrarily many times. CD-R discs (CD-Rs) are readable by most CD readers manufactured prior to the i ...
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, an optical disc drive is a disc drive that uses laser light or electromagnetic waves within or near the visible light spectrum as part of the process of reading or writing data to or from optical discs. Some drives can only ...
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 optical disc data storage format. CD players were first sold to consumers in 1982. CDs typically contain recordings of audio material such as music or audio ...
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 rot Disc rot is the tendency of CD, 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 contamina ...
, 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 System The Serial Copy Management System (SCMS) is a copy protection scheme that was created in response to the digital audio tape (DAT) invention, in order to prevent DAT recorders from making second-generation or serial copies. SCMS sets a "copy" bit ...
), an early form of digital rights management (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 Aud ...
). 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 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 sensi ...
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. It was invented and developed in 1995 and first released on November 1, 1996, in Japan. The medium can store any kind ...
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 System The Serial Copy Management System (SCMS) is a copy protection scheme that was created in response to the digital audio tape (DAT) invention, in order to prevent DAT recorders from making second-generation or serial copies. SCMS sets a "copy" bit ...
(SCMS), an early form of digital rights management (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 Aud ...
(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 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, and other media. Copy protection is most commonly found o ...
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
ripped Ripped may refer to: * Ripped, a slang term for having achieved muscle hypertrophy * '' Ripped: How the Wired Generation Revolutionized Music'', a book by Greg Kot * ''Ripped,'' a series of books and DVDs by Clarence Bass * "Ripped", an episode of ...
, or copied, to hard drives or easily converted to other formats (like FLAC,
MP3 MP3 (formally MPEG-1 Audio Layer III or MPEG-2 Audio Layer III) is a coding format for digital audio developed largely by the Fraunhofer Society in Germany, with support from other digital scientists in the United States and elsewhere. Origin ...
or
Vorbis Vorbis is a free and open-source software project headed by the Xiph.Org Foundation. The project produces an audio coding format and software reference encoder/decoder (codec) for lossy audio compression. Vorbis is most commonly used in conj ...
). 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 AutoPlay, a feature introduced in Windows 98, examines newly discovered removable media and devices and, based on content such as pictures, music or video files, launches an appropriate application to play or display the content. It is closely re ...
to prevent the running of the DRM executable program.


See also


References


Further reading

*
Ecma International Ecma International () is a nonprofit standards organization for information and communication systems. It acquired its current name in 1994, when the European Computer Manufacturers Association (ECMA) changed its name to reflect the organization ...

''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. * 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. (), commonly shortened to Philips, is a Dutch multinational conglomerate corporation that was founded in Eindhoven in 1891. Since 1997, it has been mostly headquartered in Amsterdam, though the Benelux headquarters i ...
in 2005
Patent History CD Disc
nbsp;– published by
Philips Koninklijke Philips N.V. (), commonly shortened to Philips, is a Dutch multinational conglomerate corporation that was founded in Eindhoven in 1891. Since 1997, it has been mostly headquartered in Amsterdam, though the Benelux headquarters i ...
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 , commonly stylized as SONY, is a Japanese multinational conglomerate corporation headquartered in Minato, Tokyo, Japan. As a major technology company, it operates as one of the world's largest manufacturers of consumer and professiona ...
website in Japanese
Popularized History on Soundfountain

A Media History of the Compact Disc
(1-hour podcast interview) {{Authority control 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 Home video