Compact disc
"CD" and "CDs" redirect here.
For other uses, see CD (disambiguation) and CDS.
| Media type | Optical disc |
|---|---|
| Encoding | Various |
| Capacity | Typically up to 700 MiB (up to 80 minutes' audio) |
| Read mechanism | 780 nm wavelength (infrared and red edge) semiconductor laser (early players used helium–neon lasers), 1,200 Kibit/s (1×) |
| Write mechanism | 780 nm wavelength (infrared and red edge) semiconductor laser in recordable formats CD-R and CD-RW, pressed mold (stamper) in read only formats |
| Standard | Rainbow Books |
| Developed by | Philips, Sony |
| Usage | Audio and data storage |
| Extended from | LaserDisc |
| Extended to | CD-RW |
| Released | 1 October 1982; 38 years ago (1982-10-01) (Japan)
March 1983; 37 years ago (1983-03) (Europe and North America) |
Compact disc (CD) is a digital optical disc data storage format that was co-developed by Philips and Sony and released in 1982.
The format was originally developed to store and play only digital audio recordings (CD-DA) but was later adapted for storage of data (CD-ROM).
Several other formats were further derived from these, including write-once audio and data storage (CD-R), rewritable media (CD-RW), Video CD (VCD), Super Video CD (SVCD), Photo CD, PictureCD, Compact Disc-Interactive (CD-i), and Enhanced Music CD.
The first commercially available audio CD player, the Sony CDP-101, was released October 1982 in Japan.
Standard CDs have a diameter of 120 millimetres (4.7 in) 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 more data closely on the same sized disc.
The Mini CD has various diameters ranging from 60 to 80 millimetres (2.4 to 3.1 in); they are sometimes used for CD singles, 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 hard 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.
From the early 2000s, CDs were increasingly being replaced by other forms of digital storage and distribution, with the result that by 2010 the number of audio CDs being sold in the U.S. had dropped about 50% from their peak; however, they remained one of the primary distribution methods for the music industry.
In 2014, revenues from digital music services, such as iTunes, Spotify and YouTube, matched those from physical format sales for the first time.
According to the RIAA's midyear report in 2020, phonograph record revenues surpassed those of CDs for the first time since the 1980s.
History
Optophonie, first presented in 1931, is a very early example of a recording device using light for both recording and playing back sound signals on a transparent photograph.
More than thirty years later, American inventor James T. Russell has been credited with inventing the first system to record digital video on an optical transparent foil that is lit from behind by a high-power halogen lamp, not a laser.
Russell's patent application was filed in 1966, and he was granted a patent in 1970.
Following litigation, Sony and Philips licensed Russell's patents for recording, not the play-back part (then held by a Canadian company, Optical Recording Corp.) in the 1980s.
It is debatable whether Russell's concepts, patents, and prototypes instigated and in some measure influenced compact disc's design.
The compact disc is an evolution of LaserDisc technology, where a focused laser beam is used that enables the high information density required for high-quality digital audio signals.
Unlike the prior art by Optophonie and James Russell, the information on the disc is read from a reflective layer using a laser as a light source through a protective substrate.
Prototypes were developed by Philips and Sony independently in the late 1970s.
Although originally dismissed by Philips Research management as a trivial pursuit, the CD became the primary focus for Philips as the LaserDisc format struggled.
In 1979, Sony and Philips set up a joint task force of engineers to design a new digital audio disc.
After a year of experimentation and discussion, the Red Book CD-DA standard was published in 1980.
After their commercial release in 1982, compact discs and their players were extremely popular.
Despite costing up to $1,000, over 400,000 CD players were sold in the United States between 1983 and 1984.
By 1988, CD sales in the United States surpassed those of vinyl LPs, and by 1992 CD sales surpassed those of prerecorded music cassette tapes.
The success of the compact disc has been credited to the cooperation between Philips and Sony, which together agreed upon and developed compatible hardware.
The unified design of the compact disc allowed consumers to purchase any disc or player from any company, and allowed the CD to dominate the at-home music market unchallenged.
Digital audio laser-disc prototypes
In 1974, Lou Ottens, director of the audio division of Philips, started a small group to develop an analog optical audio disc with a diameter of 20 cm (7.9 in) and a sound quality superior to that of the vinyl record.
However, due to the unsatisfactory performance of the analog format, two Philips research engineers recommended a digital format in March 1974.
In 1977, Philips then established a laboratory with the mission of creating a digital audio disc.
The diameter of Philips's prototype compact disc was set at 11.5 cm (4.5 in), the diagonal of an audio cassette.
Heitaro Nakajima, who developed an early digital audio recorder within Japan's national public broadcasting organization NHK in 1970, became general manager of Sony's audio department in 1971.
His team developed a digital PCM adaptor audio tape recorder using a Betamax video recorder in 1973.
After this, in 1974 the leap to storing digital audio on an optical disc was easily made.
Sony first publicly demonstrated an optical digital audio disc in September 1976.
A year later, in September 1977, Sony showed the press a 30 cm (12 in) disc that could play an hour of digital audio (44,100 Hz sampling rate and 16-bit resolution) using MFM modulation.
In September 1978, the company demonstrated an optical digital audio disc with a 150-minute playing time, 44,056 Hz sampling rate, 16-bit linear resolution, and cross-interleaved error correction code—specifications similar to those later settled upon for the standard compact disc format in 1980.
Technical details of Sony's digital audio disc were presented during the 62nd AES Convention, held on 13–16 March 1979, in Brussels.
Sony's AES technical paper was published on 1 March 1979.
A week later, on 8 March, Philips publicly demonstrated a prototype of an optical digital audio disc at a press conference called "Philips Introduce Compact Disc" in Eindhoven, Netherlands.
Sony executive Norio Ohga, later CEO and chairman of Sony, and Heitaro Nakajima were convinced of the format's commercial potential and pushed further development despite widespread skepticism.
Collaboration and standardization
In 1979, Sony and Philips set up a joint task force of engineers to design a new digital audio disc.
Led by engineers Kees Schouhamer Immink and Toshitada Doi, the research pushed forward laser and optical disc technology.
After a year of experimentation and discussion, the task force produced the Red Book CD-DA standard.
First published in 1980, the standard was formally adopted by the IEC as an international standard in 1987, with various amendments becoming part of the standard in 1996.
Philips coined the term compact disc in line with another audio product, the Compact Cassette, and contributed the general manufacturing process, based on video LaserDisc technology.
Philips also contributed eight-to-fourteen modulation (EFM), while Sony contributed the error-correction method, CIRC, which offers a certain resilience to defects such as scratches and fingerprints.
The Compact Disc Story, told by a former member of the task force, gives background information on the many technical decisions made, including the choice of the sampling frequency, playing time, and disc diameter.
The task force consisted of around 6 persons, though according to Philips, the compact disc was "invented collectively by a large group of people working as a team."
Initial launch and adoption
Philips established the Polydor Pressing Operations plant in Langenhagen near Hannover, Germany, and quickly passed a series of milestones.
- The first test pressing was of a recording of Richard Strauss's Eine Alpensinfonie (An Alpine Symphony) played by the Berlin Philharmonic and conducted by Herbert von Karajan, who had been enlisted as an ambassador for the format in 1979.
- The first public demonstration was on the BBC television programme Tomorrow's World in 1981, when the Bee Gees' album Living Eyes (1981) was played.
- The first commercial compact disc was produced on 17 August 1982, a 1979 recording of Chopin waltzes by Claudio Arrau.
- The first 50 titles were released in Japan on 1 October 1982, the first of which was a re-release of the Billy Joel album 52nd Street.
- The first CD played on BBC Radio was in October 1982 on BBC Radio Scotland (Jimmy Mack programme, Followed by Ken Bruce and Eddie Mair all BBC Scotland), with the first CD played on UK independent radio station shortly after (Radio Forth, Jay Crawford Show). The CD was Dire Straits album Love Over Gold.
The Japanese launch was followed on 14 March 1983 by the introduction of CD players and discs to Europe and North America (where CBS Records released sixteen titles).
This 1983 event is often seen as the "Big Bang" of the digital audio revolution.
The new audio disc was enthusiastically received, especially in the early-adopting classical music and audiophile communities, and its handling quality received particular praise.
As the price of players gradually came down, and with the introduction of the portable Discman the CD began to gain popularity in the larger popular and rock music markets.
With the rise in CD sales, pre-recorded cassette tape sales began to decline in the late 1980s; CD sales overtook cassette sales in the early 1990s.
The first artist to sell a million copies on CD was Dire Straits, with their 1985 album Brothers in Arms.
One of the first CD markets was devoted to reissuing popular music whose commercial potential was already proven.
The first major artist to have their entire catalog converted to CD was David Bowie, whose first fourteen studio albums of (then) sixteen were made available by RCA Records in February 1985, along with four greatest hits albums; his fifteenth and sixteenth albums had already been issued on CD by EMI Records in 1983 and 1984, respectively.
On February 26, 1987, the first four UK albums by the Beatles were released in mono on compact disc.
In 1988, 400 million CDs were manufactured by 50 pressing plants around the world.
Further development and decline
The CD was primarily planned as the successor to the vinyl record for playing music, rather than as a data storage medium.
However, CDs have grown to encompass other applications.
In 1983, following the CD's introduction, Immink and Joseph Braat presented the first experiments with erasable compact discs during the 73rd AES Convention.
It took, however, almost 10 years before their technology was commercialized in Sony's MiniDisc.
In June 1985, the computer-readable CD-ROM (read-only memory) and, in 1990, CD-Recordable were introduced, also developed by both Sony and Philips.
Recordable CDs were a new alternative to tape for recording and copying music without the defects introduced in compression used in other digital recording methods.
Other newer video formats such as DVD and Blu-ray use the same physical geometry as CD, and most DVD and Blu-ray players are backward compatible with audio CD.
CD sales in the United States peaked by 2000.
By the early 2000s, the CD player had largely replaced the audio cassette player as standard equipment in new automobiles, with 2010 being the final model year for any car in the United States to have a factory-equipped cassette player.
With the increasing popularity of portable digital audio players, such as mobile phones, and solid state music storage, CD players are being phased out of automobiles in favor of minijack auxiliary inputs, wired connection to USB devices and wireless Bluetooth connection.
Meanwhile, with the advent and popularity of Internet-based distribution of files in lossily-compressed audio formats such as MP3, sales of CDs began to decline in the 2000s.
For example, between 2000 and 2008, despite overall growth in music sales and one anomalous year of increase, major-label CD sales declined overall by 20%, although independent and DIY music sales may be tracking better according to figures released March 30, 2009, and CDs still continue to sell greatly.
As of 2012, CDs and DVDs made up only 34% of music sales in the United States.
By 2015, only 24% of music in the United States was purchased on physical media, 2/3 of this consisting of CDs; however, in the same year in Japan, over 80% of music was bought on CDs and other physical formats.
In 2018, U.S. CD sales were 52 million units—less than 6% of the peak sales volume in 2000.
Despite the rapidly declining sales year-over-year, the pervasiveness of the technology remained for a time, with companies placing CDs in pharmacies, supermarkets, and filling station convenience stores targeting buyers least able to use Internet-based distribution.
In 2018 Best Buy announced plans to decrease their focus on CD sales, however, while continuing to sell records, sales of which are growing during the vinyl revival.
Awards and accolades
Sony and Philips received praise for the development of the compact disc from professional organizations.
These awards include
- Technical Grammy Award for Sony and Philips, 1998.
- IEEE Milestone award, 2009, for Philips only with the citation: "On 8 March 1979, N.V. Philips' Gloeilampenfabrieken demonstrated for the international press a Compact Disc Audio Player. The demonstration showed that it is possible by using digital optical recording and playback to reproduce audio signals with superb stereo quality. This research at Philips established the technical standard for digital optical recording systems."
Physical details
Logical format
Manufacture
Main article: CD manufacturing
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 tapes, cassette tapes, 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 vinyl to CDs but was broken when Apple 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
Main article: CD-R
Recordable Compact Discs, CD-Rs, 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 changes the color of the dye to allow the read laser of a standard 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 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 System), an early form of digital rights management (DRM), to conform to the AHRA (Audio Home Recording Act).
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
Main article: CD-RW
CD-RW 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 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 (SCMS), an early form of digital rights management (DRM), to conform to the United States' Audio Home Recording Act (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
Main article: Compact Disc and DVD 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 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
Credits to the contents of this page go to the authors of the corresponding Wikipedia page: en.wikipedia.org/wiki/Compact disc.