ACD player is an electronic device that plays audiocompact discs, which are adigitaloptical discdata storage format. CD players were first sold to consumers in 1982. CDs typically contain recordings of audio material such as music oraudiobooks. CD players may be part of homestereo systems,car audio systems,personal computers, orportable CD players such as CDboomboxes. Most CD players produce an output signal via aheadphone jack orRCA jacks. To use a CD player in a home stereo system, the user connects an RCA cable from the RCA jacks to ahi-fi (or otheramplifier) andloudspeakers for listening to music. To listen to music using a CD player with a headphone output jack, the user plugs headphones or earphones into the headphone jack.
Modern units can play audio formats other than the original CDPCM audio coding, such asMP3,AAC andWMA.DJs playingdance music at clubs often use specialized players with an adjustable playback speed to alter thepitch and tempo of the music.Audio engineers using CD players to play music for an event through asound reinforcement system use professional audio-grade CD players. CD playback functionality is also available onCD-ROM/DVD-ROM drive-equipped computers as well as onDVD players and most optical disc-basedhome video game consoles.
American inventorJames T. Russell is known for inventing the first system to record digital video information on an opticaltransparentfoil that is lit from behind by a high-power halogen lamp.[1][2] Russell's patent application was first filed in 1966, and he was granted a patent in 1970. Following litigation, Sony and Philips licensed Russell's recording patents (then held by a Canadian company, Optical Recording Corp.) in the 1980s.[3][4][5]
The compact disc is not based on Russell's invention; it is an evolution ofLaserDisc technology, where a focusedlaser beam is used that enables the high information density required for high-quality digital audio signals. Prototypes were developed byPhilips andSony independently in the late 1970s.[6] 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, theRed BookCD-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.[7] The success of the compact disc has been credited to the cooperation between Philips and Sony, who came together to agree upon and develop 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.[8]
TheSony CDP-101, released in 1982, was the world's first commercially released compact disc player. It was originally sold only in Japan.[9]
Unlike earlyLaserDisc players, first CD players already usedlaser diodes instead of largerhelium-neon lasers.[10][11]
In 1974, Lou Ottens, director of the audio division of Philips, started a small group with the aim to develop an analog[12] optical audio disc with a diameter of 20 cm (7.9 in) and a sound quality superior to that of the vinyl record.[13] However, due to the unsatisfactory performance of the analog format, two Philips research engineers recommended a digital format in March 1974.[12] 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.[12][14]
Heitaro Nakajima, who developed an early digital audio recorder within Japan's national public broadcasting organizationNHK in 1970, became general manager ofSony's audio department in 1971. His team developed a digitalPCM adaptor audio tape recorder using aBetamax video recorder in 1973. After this, in 1974, the leap to storing digital audio on an optical disc was easily made.[15]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 60 minutes of digital audio (44,100 Hz sampling rate and 16-bit resolution) usingMFM modulation.[16] 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, andcross-interleavederror 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 62ndAES Convention, held on 13–16 March 1979, inBrussels.[16] 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"[17] inEindhoven,Netherlands.[18]
Sony executiveNorio Ohga, later CEO and chairman of Sony, andHeitaro Nakajima were convinced of the format's commercial potential and pushed further development despite widespread skepticism.[19] As a result, in 1979, Sony and Philips set up a joint task force of engineers to design a new digital audio disc. Led by engineersKees Schouhamer Immink[20] andToshitada Doi, the research pushed forwardlaser andoptical disc technology.[17] After a year of experimentation and discussion, the task force produced theRed BookCD-DA standard. First published in 1980, the standard was formally adopted by theIEC as an international standard in 1987, with various amendments becoming part of the standard in 1996.
Philips coined the termcompact disc in line with another audio product, theCompact Cassette,[14] and contributed the generalmanufacturing process, based on video LaserDisc technology. Philips also contributedeight-to-fourteen modulation (EFM), which offers a certain resilience to defects such as scratches and fingerprints, while Sony contributed theerror-correction method,cross-interleaved Reed–Solomon coding (CIRC). TheCompact Disc Story,[12] 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 four to eight persons,[21][22] though according to Philips, the compact disc was "invented collectively by a large group of people working as a team."[23]
Red Book was the first standard in theRainbow Books series of standards.
Philips established the Polydor Pressing Operations plant inLangenhagen nearHannover,Germany, and quickly passed a series of milestones.
The Japanese launch was followed in March 1983 by the introduction of CD players and discs to Europe[28] and North America (where CBS Records released 16 titles).[29] This event is often seen[by whom?] as the "Big Bang" of the digital audio revolution. The new audio disc was enthusiastically received, especially in the early-adoptingclassical music andaudiophile communities, and its handling quality received particular praise. As the price of players gradually came down, and with the introduction of the portableWalkman, the CD began to gain popularity in the larger popular and rock music markets. The first artist to sell a million copies on CD wasDire Straits, with their 1985 albumBrothers in Arms.[30] The first major artist to have his entire catalog converted to CD wasDavid Bowie, whose 15 studio albums were made available byRCA Records in February 1985, along with four greatest hits albums.[31] In 1988, 400 million CDs were manufactured by 50 pressing plants around the world.[32]
.jpg)
The CD was planned to be the successor of thegramophone record for playing music, rather than primarily as a data storage medium, but from its origins as a format for music, its use has grown to encompass other applications. In 1983, following the CD's introduction,Immink andBraat presented the first experiments with erasable compact discs during the 73rdAES Convention.[33] In June 1985, the computer-readableCD-ROM (read-only memory) was introduced and, in 1990, theCD-Recordable, also developed by both Sony and Philips.[34] Recordable CDs were a new alternative to tape for recording music and copying music albums without the defects introduced in the compression used in otherdigital recording methods. Other newer video formats such asDVD andBlu-ray use the same physical geometry as CD, and most DVD and Blu-ray players arebackward compatible with audio CD.
By the early 2000s, the CD player had largely replaced theaudio cassette player as standard equipment in new automobiles, with 2010 being the final model year for any car in the US to have a factory-equipped cassette player.[35] Currently, 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 and connections to USB devices.[citation needed]
Some CD players incorporate disc changers. Commonly these can hold 3, 5, 6, or 10 discs at once and change from one disc to the next without user intervention. Disc changers capable of holding up to 400 discs at once were available. Also, the user can manually choose the disc to be played, making it similar to ajukebox. They were often built into car audio and home stereo systems, although 7 disc CD changers were once made byNEC andNakamichi[36] for PCs. Some could also play DVD and Blu-ray discs.
Meanwhile, with the advent and popularity ofInternet-based distribution of files inlossily-compressedaudio formats such asMP3, 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%[37] – although independent and DIY music sales may be tracking better (according to figures released 30 March 2009), and CDs still continue to sell greatly.[38] As of 2012, CDs and DVDs made up only 34% of music sales in the United States.[39] In Japan, however, over 80% of music was bought on CDs and other physical formats as of 2015.[40] As of 2020, compact cassettes, vinyl records, and CDs are still being released by some musicians, primarily as merchandise, to allow fans to provide financial support while receiving something tangible in return.
The process of playing an audio CD, touted as a digital audio storage medium, starts with the plastic polycarbonate compact disc, a medium that contains the digitally encoded data. The disc is placed in a tray that either opens up (as with portable CD players) or slides out (the norm with in-home CD players, computer disc drives and game consoles). In some systems, the user slides the disc into a slot (e.g., car stereo CD players). Once the disc is loaded into the tray, the data is read out by a mechanism that scans the circular data tracks using alaser beam. An electric motor spins the disc. The tracking control is done by analog servo amplifiers and then the high-frequency analog signal read from the disc is digitized, processed and decoded into analog audio and digital control data which is used by the player to position the playback mechanism on the correct track, do the skip and seek functions and display track, time, index and, on newer players in the 2010s, display title and artist information on a display placed in the front panel.[41]
 | This sectiondoes notcite anysources. Please helpimprove this section byadding citations to reliable sources. Unsourced material may be challenged andremoved.(January 2014) (Learn how and when to remove this message) |
To read the data from the disc, a laser beam shines on the surface of the disc. Surface differences between discs being played, and tiny position differences once loaded, are handled by using a movable lens with a very close focal length to focus the light on the disc. A low-mass lens coupled to an electromagnetic coil is in charge of keeping focused the beam on the 600 nm wide data track.
When the player tries to read from a stop, it first does a focus seek program that moves the lens up and down from the surface of the disc until a reflection is detected; when there is a reflection, the servo electronics lock in place keeping the lens in perfect focus while the disc rotates and changes its relative height from the optical block.
Different brands and models of optical assemblies use different methods of focus detection. On most players, the focus position detection is made using the difference in the current output of a block of four photodiodes. The photodiode block and the optics are arranged in such a way that a perfect focus projects a circular pattern on the block while a far or near focus projects an ellipse differing in the position of the long edge in north–south or west-southwest. That difference is the information that the servo amplifier uses to keep the lens at the proper reading distance during the playback operation, even if the disc is warped.[42]
Another servo mechanism in the player is in charge of keeping the focused beam centered on the data track.
Two optical pick-up designs exist, the original CDM series from Philips use a magnetic actuator mounted on a swing-arm to do coarse and fine tracking. Using only one laser beam and the 4 photodiode block, the servo knows if the track is centered by measuring side-by-side movement of the light of beam hitting on the block and corrects to keep the light on the center.
The other design by Sony uses a diffraction grating to part the laser light into one main beam and two sub-beams. When focused, the two peripheral beams cover the border of the adjacent tracks a fewmicrometers apart from the main beam and reflect back on two photodiodes separated from the main block of four. The servo detects the RF signal being received on the peripheral receivers and the difference in output between these two diodes conform the tracking error signal that the system uses to keep the optics in the proper track. The tracking signal is fed to two systems, one integrated in the focus lens assembly can do fine tracking correction and the other system can move the entire optical assembly side by side to do coarse track jumps.
The sum of the output from the four photodiodes makes the RF or high-frequency signal which is an electronic mirror of the pits and lands recorded on the disc. The RF signal, when observed on an oscilloscope, has a characteristiceye pattern and its usefulness in servicing the machine is paramount for detecting and diagnosing problems, and calibrating CD players for operation.
The first stage in the processing chain for the analog RF signal (from the photoreceptor device) is digitizing it. Using various circuits like a simple comparator or a data slicer, the analog signal becomes a chain of two binary digital values, 1 and 0. This signal carries all the information in a CD and is modulated using a system calledeight-to-fourteen modulation (EFM). The second stage is demodulating the EFM signal into a data frame that contains the audio samples, error correction parity bits, according with the CIRC error correction code, and control data for the player display and micro-computer. The EFM demodulator also decodes part of the CD signal and routes it to the proper circuits, separating audio, parity and control (subcode) data.
After demodulating, a CIRC error corrector takes each audio data frame, stores it in memory and verifies that it has been read correctly, if it is not, it takes the parity and correction bits and fixes the data, then it moves it out to adigital-to-analog converter (DAC) to be converted to an analog audio signal. If the data missing is enough to make recovery impossible, the correction is made by interpolating the data from subsequent frames so the missing part is not noticed. Each player has a different interpolation ability. If too many data frames are missing or unrecoverable, the audio signal may be impossible to fix by interpolation, so an audio mute flag is raised to mute the DAC to avoid played back of invalid data. The Redbook standard dictates that, if there is invalid, erroneous or missing audio data, it cannot be output to the speakers as digital noise, it has to be muted.
The Audio CD format requires every player to have enough processing power to decode the CD data; this is normally made byapplication-specific integrated circuits (ASICs). ASICs do not work by themselves, however; they require a main microcomputer ormicrocontroller to orchestrate the entire machine. Thefirmware of basic CD players typically is areal-time operating system.
Some early optical computer drives are equipped with an audio connector and buttons for standalone CD playback functionality.[43]
Sony released itsCDP-101 CD player[44] in 1982 with a slide-out tray design for the CD. As it was easy to manufacture and to use, most CD player manufacturers stayed with the tray style ever since.[45][46] The tray mechanism is also used in many moderndesktop computercases, as well as thePhilips CD-i,PlayStation 2,Xbox andXbox 360. However, there have been some notable exceptions to this common CD tray design.
During the launch of the first prototypeGoronta CD player[47] bySony at the Japanese Audio Fair in 1982, Sony showcased the vertical loading design. Although the Sony prototype design was never put into volume production, the concept was for a time adopted for production by a number of early Japanese CD player manufacturers, includingAlpine/Luxman,Matsushita under theTechnics brand,Kenwood andToshiba/Aurex. For the early vertical loading players, Alpine sourced their AD-7100 player designs for Luxman,[48] Kenwood and Toshiba (using their Aurex brand). Kenwood added theirSigma Drive outputs to this design as a modification. A picture of this early design can be seen on the Panasonic Web site.[49] The vertical loading is similar the one common incassette decks, where the holder opens, and disc is dropped to it. The holder is closed manually, by motor after pressing a button, or completely automatically. Some CD players combine vertical loading with slot loading due to the disc being drawn further into the disc holder as it closes.
In 1983, Philips, at the US and European launch of the CD format, showcased the first top-loading CD tray designs with their CD100 CD player.[50][51] (Philips audio products were sold asMagnavox in the US at the time.) The design had a clamp on the lid which meant the user had to close this over the CD when it was placed inside the machine. Later,Meridian introduced their MCD high end CD player,[52] with Meridian electronics in the Philips CD100 chassis.
Top-loading was adopted on various equipment designs such as mini systems and portable CD players, but among stereo component CD players, only a handful of top-loading models have been made. Examples includeLuxman's D-500 and D-500X series[53] players andDenon's DP-S1,[54] both launched in 1993.Top-loading is also common in players intended for broadcast and live sound DJ use, such as Technics' SL-P50 (1984–1985) and Technics SL-P1200 (1986–1992). They more closely mimic the physical arrangement and ergonomics of record turntables used in those applications.
The top-loading disc tray design is also used in mostfifth-generationvideo gameconsoles (PlayStation,Saturn,3DO Interactive Multiplayer), as well as theDreamcast,GameCube, andWii Mini.
| This sectiondoes notcite anysources. Please helpimprove this section byadding citations to reliable sources. Unsourced material may be challenged andremoved.(January 2014) (Learn how and when to remove this message) |
The Philips CD303 of 1983-1984 was the first player to adopt tray loading with a sliding play mechanism. Basically, as the tray came out to collect the CD, the entire player's transport system also came out as one unit. TheMeridians 200 and 203 players were of this type. They were also the first to use a design in which the audio electronics were in a separate enclosure from the CD drive and pickup mechanism. A similar mechanism is used in slim optical disc drives (also known as slim internal DVD drive, optical drive or DVD burner), which were once commonly used in laptop computers.
| This sectiondoes notcite anysources. Please helpimprove this section byadding citations to reliable sources. Unsourced material may be challenged andremoved.(January 2014) (Learn how and when to remove this message) |
Slot loading is the preferred loading mechanism for car audio players. There is no tray that pops out, and a motor is used to assist disc insertion and removal. Some slot-loading mechanisms and changers can load and play backMini CDs without the need of an adapter (such as the originalWii model's standard-sized disc slot being capable of accepting smallerGameCube Game Discs) but they may work with limited functionality (a disc changer with a Mini CD inserted will refuse to operate until such disc is removed, for example).Non-circular CDs cannot be used on such loaders because they cannot handle non-circular discs. When inserted, such discs may become stuck and damage the mechanism. It is also used on some laptop computers, theoriginal and slimPlayStation 3, the Wii's original model and its Family Edition and mosteighth-generation video game consoles (theWii U,PlayStation 4 andXbox One), as well as theninth-generationPlayStation 5 andXbox Series X.
Two types of optical tracking mechanisms exist:
The swing-arm mechanism has a distinctive advantage over the other in that it does not skip when the rail becomes dirty. The swing arm mechanisms tend to have a much longer life than their radial counterparts.[citation needed] The main difference between the two mechanisms is the way they read the data from the disc. The swing-arm mechanism uses a magnetic coil wound over a permanent magnet to provide the tracking movement to the laser assembly in a similar way ahard drive moves its head across the data tracks. It also uses another magnetic movement mechanism attached to the focusing lens to focus the laser beam on the disc surface. By operating the tracking or the focus actuators, the laser beam can be positioned on any part of the disc.This mechanism employs a single laser beam and a set of four photodiodes to read, focus and keep track of the data coming from the disc.[56]
The linear tracking mechanism uses a motor and reduction gears to move the laser assembly radially across the tracks of the disc and it also has a set of six coils mounted in the focusing lens over a permanent magnetic field. One set of two coils moves the lens closer to the disc surface, providing the focusing motion, and the other set of coils moves the lens radially, providing a finer tracking motion. This mechanism uses the three-beam tracking method in which a main laser beam is used to read and focus the data track of the disc using three or four photodiodes, depending on the focus method, and two smaller beams read the adjacent tracks at each side to help the servo keep the tracking using two more helperphotodiodes.[57]
| This sectiondoes notcite anysources. Please helpimprove this section byadding citations to reliable sources. Unsourced material may be challenged andremoved.(January 2014) (Learn how and when to remove this message) |
A CD player has three major mechanical components: adrive motor, alens system or pickup head, and atracking mechanism.The drive motor (also called spindle) spins the disc to a scanning velocity of 1.2–1.4 m/s (constant linear velocity) – equivalent to approximately 500 RPM at the inside of the disc, and approximately 200 RPM at the outside edge. (A disc played from beginning to end slows its rotation rate during playback.) The tracking mechanism moves the lens system along the spiral tracks in which information is encoded, and the lens assembly reads the information using alaser beam produced by alaser diode. The laser reads information by focusing a beam on the CD, which is reflected off the disc's mirrored surface back to aphotodiode array sensor. The sensor detects changes in the beam, and a digital processing chain interprets these changes as binary data. The data are processed and eventually converted to sound using a DAC.
A TOC or Table of Contents is located after thelead-in area of the disc, which is located in an inner ring of the disc and contains roughly five kilobytes of available space. It is the first information that the player reads when the disc is loaded in the player and contains information on the total number of audio tracks, the running time on the CD, the running time of each track, and other information such as ISRC and the format structure of the disc. The TOC is of such vital importance for the disc that if it is not read correctly by the player, the CD could not be played back. That is why it is repeated three times before the first music program starts. Thelead out area in the end (the outer peripheral) of the disc tells the player that disc has come to an end.
| This sectiondoes notcite anysources. Please helpimprove this section byadding citations to reliable sources. Unsourced material may be challenged andremoved.(January 2014) (Learn how and when to remove this message) |
CD players can employ a number of ways to improve performance or reduce component count or price. Features such as oversampling, one-bit DACs, dual DACs, interpolation (error correction), anti-skip buffering, digital and optical outputs are, or were, likely to be found. Other features improve functionality, such as track programming, random play and repeat, or direct track access. Yet others are related to the CD player's intended target, such as anti-skip for car and portable CD players, pitch control and queuing for a DJ's CD player, remote and system integration for household players. Description of some features follows:
A portable CD player is aportable audio player used to playcompact discs. Portable CD players are powered by batteries and they have a 1/8" headphone jack into which the user plugs a pair ofheadphones. The first portable CD player released was theD-50 bySony.[58] The D-50 was made available on the market in 1984,[59] and adopted for Sony's entire portable CD player line.
In 1998, portableMP3 players began to compete with portable CD players. AfterApple Computer entered the music player market with itsiPod line, within ten years it became the dominant seller of portabledigital audio players, "...while former giantSony (maker of the [portable]Walkman and [CD]Discman [was] struggling."[60] This market shift was initiated when the first portable digital audio player, theRio digital music player, was introduced. The 64 MB Rio MP3 player enabled users to store about 20 songs.[61] One of the benefits of the Rio over portable CD players was that since the Rio had no moving parts, it offered skip-free playback.[61] Since 1998, the price of portable digital audio players has dropped and the storage capacity has increased significantly. In the 2000s, users can "carry [their] entire music collection in a [digital audio] player the size of a cigarette package."[61] The 4 GB iPod, for example, holds over 1,000 songs.[61] By the early 2010s, MP3 players began to decline in popularity,[62] in favour ofdownloading music on platforms such asiTunes, and laterstreaming music on platforms such asSpotify,Apple Music, andYouTube Music.[63][64][65]
Aboombox is a common term for a portablecassette and AM/FM radio that consists of an amplifier, two or moreloudspeakers and a carrying handle. Beginning in the 1990s, boomboxes typically included a CD player. The boombox CD player is the only type of CD player that produces sound audible by the listener independently, without the need forheadphones or an additional amplifier or speaker system. Designed for portability, boomboxes can be powered bybatteries as well as by line current. The boombox was introduced to the American market during the mid-1970s. The desire for louder and heavier bass led to bigger and heavier boxes; by the 1980s, some boomboxes had reached the size of asuitcase. Most boomboxes were battery-operated, leading to extremely heavy, bulky boxes.[66]
Most boomboxes from the 2010s typically include a CD player compatible withCD-R andCD-RW, which allows the user to carry their own music compilations on a higher fidelity medium. Many also permit iPod and similar devices to be plugged into them through one or more auxiliary input jacks. Some also support formats such asMP3 andWMA. Another modern variant is a DVD player/boombox with a top-loading CD/DVD drive and anLCD video screen in the position once occupied by a cassette deck.[67] Many models of this type of boombox include inputs for external video (such astelevision broadcasts) and outputs to connect the DVD player to a full-sized television.
Disc jockeys (DJs) who are playing a mix ofsongs at adance club,rave, ornightclub create their dancemixes by having songs playing on two or more sound sources and using aDJ mixer to transition seamlessly between songs. In the 1970sdisco era, DJs typically used tworecord players.[68] From the 1980s to the 1990s, twocompact cassette players became a popular sound source for DJs.[69] In subsequent decades, DJs shifted to CDs and then todigital audio players. DJs who use CDs and CD players typically use specialized DJ CD players (such asCDJs) that have features not available on regular CD players, such aspitch control.
DJs who are performingscratching–the creation of rhythmic sounds and sound effects from sound recordings–traditionally usedvinyl records andturntables. In the 2010s, some specialized DJ CD players can be used to create scratching effects using songs on CDs.
An international collaboration between Philips and the Sony Corporation lead to the creation of the compact disc. The author explains how it came about
| Discs | |
|---|---|
| Technology | |
| Hardware/software/content | |
| Court cases | |
| Lists | |
| Variants based on CD | |
| See also | |
