Compact disc

This may be in large degree due to its status as a Philips trademark under that spelling. Some of the improvements that are being worked on are:. Notwithstanding the variability of general usage between "disk" and "disc" [3], the customary spelling is "compact disc", rather than "compact disk". There is a great deal of active research and development into mobile phone technology that is currently underway. Not all players allow this. Vulnerabilities (such as SMS spoofing) have been found in many current protocols that continue to allow the possibility of eavesdropping or cloning. To hear the hidden track, the listener must usually "rewind" the player past the beginning of the first listed track. Although more recent digital systems (such as GSM) have attempted to address these fundamental issues, security problems continue to persist.

In this case, the hidden track is an unlisted track sandwiched between the two. Analogue phones could also be listened to on some radio scanners. On most discs, the location of the first track listed in the table of contents immediately follows the table of contents itself. Some problems with these models were "cloning", a variant of identity theft, and "scanning" whereby third parties in the local area could intercept and eaves drop in on calls. Other discs hide the extra material at the beginning of the disc. Early mobile phones did not have much security designed in. Either way, the hidden portion is heard when the disc is played to the end. Restrictive legislation has been proposed in 40 states in the US, but only New York State has passed such a law.

These may be an extension of the last audio track or a separate track hidden from the disc's table of contents. Drivers in the Czech Republic, France, and the Netherlands may use cell phones but can be fined if they are involved in crashes while using such a device. Some commercially released audio discs have a "secret" bonus track. Australia, Brazil, Chile, Denmark, Germany, Greece, Hungary, Italy, Poland, the Philippines, Romania, Slovenia, South Africa, Spain, Switzerland, Turkey, the United Kingdom, and the United Arab Emirates prohibit the use of hand-held cell phones while driving. This is commonly referred to as the analog hole. At least 25 countries restrict or prohibit cell and other wireless technology: Israel, Japan, Portugal and Singapore all prohibit mobile phone use while driving. Any loss of sound quality caused by this method is generally considered negligible. Accidents involving a driver being distracted by talking on a mobile phone have begun to be prosecuted as negligence similar to driving while intoxicated.

In any case, even if a disc cannot be directly ripped, it can still be played in audio mode, and the audio thence captured. An experiment conducted by the American television show MythBusters concluded that use of mobile phones while driving poses the same risk as someone operating a vehicle while under the influence of alcohol. Other systems developed are Macrovision CDS-200 and Mediamax CD-3. A study in The New England Journal of Medicine reports that drivers who used mobile phones while driving were four times more likely to crash than those who don't, a rate equal to that for drunken driving at the .01 blood alcohol concentration (BAC) level. The reason for this reuse is cost efficiency. Several studies have shown that motorists have a much higher risk of collisions and losing control of the vehicle while talking on the mobile telephone simultaneously with driving, even when using "hands-free" systems. in car radios, have problems playing copy-protected media, mostly because they use hardware and firmware components also used in CD-ROM drives. Another controversial but more lethal health concern is the correlation with road traffic accidents.

Also, many ordinary CD audio players, e.g. ^{[citation needed]}. For example, audio tracks on such media cannot be easily added to a personal music collection on a computer's hard disk or a portable (non-CD) music player. It is generally thought, however, that RF is incapable of producing any more than heating effects, as it is considered non-ionizing radiation; in other words, it lacks the energy to disrupt molecular bonds such as occurs in genetic mutations. However, there has been great public outcry over copy-protected discs because many see it as a threat to fair use. (see also electromagnetic radiation hazard). It also seems likely that Philips' new models of CD recorders will be designed to be able to record from these "protected" discs. So far, however, the World Health Organization Task Force on EMF effects on health has no definitive conclusion on the veracity of these allegations.

Philips has stated that such discs are not permitted to bear the trademarked Compact Disc Digital Audio logo because they violate the Red Book specification. Some researchers also report the mobile phone industry has interfered with further research on health risks. This is intended to prevent the data track from being ripped, but can be defeated by ignoring the table of contents and reading the disc sector by sector. More recently a pan-European study provided significant evidence of genetic damage under certain conditions. Another copy protection method places a data track (usually containing bonus software for computer users) at the end of the disc and gives it an invalid size in the disc's table of contents. There is a small amount of scientific evidence for an increase in certain types of rare tumors (cancer) in long-time, heavy users. These discs are said to be more sensitive to disc pollution or surface damage (typically in the form of scratches) because they partially exhaust the error-correction thresholds incorporated into the Red Book standard right from the time of production. As with many new technologies, concerns have arisen about the effects on health from using a mobile telephone.

Some of these deliberately introduced error patterns into audio tracks severe enough to defeat the error-correcting code (and hence defeat most CD-ROM drives attempting to copy the tracks as data), but not so disruptive as to prevent interpolation from working (hence allowing the same tracks to be played in audio mode without overly affecting fidelity). Each network operator has a unique radio frequency band. Starting in early 2002, attempts were made by record companies to market "copy-protected" compact discs. Some technologies include AMPS for analog, and TDMA, CDMA, GSM, GPRS, EV-DO, and UMTS for digital communications. Where error correction fails on larger defects, audio CD players are expected to apply interpolation algorithms to conceal the loss of audio data. The technology that achieves this depends on the system which the mobile phone operator has adopted. An error-correcting code is included with Red Book audio to deal with small scratches or defects on the disc media. The dialogue between the handset and the cell site is a stream of digitized audio (except for the first generation analog networks).

Ripping is the process by which the contents of an audio disc is copied out verbatim to a duplicate disc or re-encoded into some other format, such as MP3 or Ogg Vorbis. The switch in turn connects the call to another subscriber of the same wireless service provider or to the public telephone network, which includes the networks of other wireless carriers. The Red Book audio specification does not include any copy protection mechanism. Cell sites have relatively low-power (often only one or two Watts) radio transmitters which broadcast their presence and relay communications between the mobile handsets and the switch. A CD-RW does not have as great a difference in the reflectivity of lands and bumps as a pressed CD or a CD-R, and so many CD audio players cannot read CD-RW discs, although the majority of standalone DVD players can. As the user moves around the network, the mobile device will "hand off" to new cell sites. The write laser in this case is used to heat and alter the chemical properties of the alloy and hence change its reflectivity. The handset constantly listens for the strongest signal being received from the surrounding base stations.

CD-RW is a re-recordable medium that uses a metallic alloy instead of a dye. When the cellular phone or data device is turned on, it registers with the mobile telephone exchange ("switch") with its unique identifiers, and will then be alerted by the mobile switch when there is an incoming telephone call. The resulting discs can be read by most CD-ROM drives and played in most audio CD players. The phones have a low-power transceiver that transmits voice and data to the nearest cell sites, usually .5 to 10 miles away. CD-R recordings are permanent. However, all of them communicate through electromagnetic radio waves with a cell site/base station, the antennas of which are usually mounted on a tower, pole, or building. The write laser of the CD recorder changes the characteristics of the dye to allow the read laser of a standard CD player to see the data as it would an injection molded compact disc. Mobile phones and the network they operate under vary significantly from provider to provider, and even from nation to nation.

A photosensitive dye is then applied, and then the discs are metallized and lacquer coated. Mobile phones often have features beyond sending text messages and make voice calls—including Internet browsing, music (MP3) playback, personal organizers, e-mail, built-in cameras and camcorders, ringtones, games, radio, Push To Talk (PTT), infrared and bluetooth connectivity, call registers, and ability to watch streaming video or download video for later viewing. Recordable compact discs are injection molded with a "blank" data spiral. In the event of an emergency, disaster response crews can locate trapped or injured people using the signals from their mobile phones; an interactive menu accessible through the phone's Internet browser notifies the company if the user is safe or in distress. The disc is then metallized with aluminum and lacquer coated. In Japan, cellular phone companies provide immediate notification of earthquakes and other natural disasters to their customers free of charge. Polycarbonate is liquified and injected into the mold cavity where the stamper transfers the pattern of pits and lands to the polycarbonate disc. Stories like the London Bombings, the Indian Ocean Tsunami and Hurricane Katrina have been reported on by cameraphone users on news sites like NowPublic and photosharing sites like Flickr.

It is then plated to make a positive version of the CD. Cameraphones and videophones that can capture video and take photographs are increasingly being used to cover breaking news. This dye is then etched, leaving the data track. Mobile phone use on aircraft is also prohibited, but due to concerns of possible interference with aircraft radio communications. A "stamper" is made from the original media (audio tape, data disc, etc.) by writing to a glass disc (referred to as a glass master) coated with a photosensitive dye with a laser. Many rail companies, particularly those providing long distance services, offer a "quiet car" where phone use is prohibited, much like the designated non-smoking cars in the past. Injection moulding is used to mass produce compact discs. It has become common practice for places like bookshops, libraries, movie theatres, and houses of worship to post signs prohibiting the use of mobile phones, sometimes even installing jamming equipment to prevent them.

However, in 1985 Yellow Book CD-ROM standard was established by Sony and Philips, which defined a non-volatile optical data storage medium using the same physical format as audio compact discs, readable by a computer with a CD-ROM drive. Users often speak at increased volume, with little regard for other people nearby. For its first few years of existence, the compact disc was purely an audio format. Mobile phone etiquette has become an important issue with mobiles ringing at funerals, weddings, movies, and plays.
. The sale of commercial ringtones exceeded $2.5 billion in 2004 [1]. The originally CD-only label Ryko extended this system to the other media when it began making LPs and cassettes so that a digital recording on an LP would be DDA, and so forth. This has emerged as its own industry.

A notable example is Herb Alpert's Rise album from 1979. The mobile phone itself has also become a totemic and fashion object, with users decorating, customizing, and accessorizing their mobile phones to reflect their personality. A few examples of DAD recordings exist, mostly of works that were originally recorded digitally but later remixed by artists who preferred to work with analog technology. Cellular phones in Japan, offering Internet capabilities such as NTT DoCoMo's i-mode, offer text messaging via standard e-mail. Two examples from 1982 are Signals by Rush and The Nightfly by Donald Fagen. Many phones even offer Instant Messenger services to increase the simplicity and ease of texting on phones. By the time the compact disc was introduced worldwide digital recording and mixing was becoming commonplace among recording artists and producers known for their interest in fidelity. The commercial market in SMS's is growing.

An early example of an analog recording that was digitally mixed is Fleetwood Mac's 1979 release Tusk. Many people keep in touch using SMS, and a whole culture of "texting" has developed from this. Martin used digital mixing, however, to eliminate the distortion and noise that an analog master tape would introduce (thus ADD). With high levels of mobile telephone penetration, a mobile culture has evolved, where the phone becomes a key social tool, and people rely on their mobile phone addressbook to keep in touch with their friends. Others, such as former Beatles producer George Martin, felt that the multitrack digital recording technology of the early 1980s had not reached the sophistication of analog systems. In some developing countries, where there is little existing fixed-line infrastructure, the mobile phone has become widespread. Stevie Wonder adopted the technology in early 1979 for Journey Through the Secret Life of Plants and used it on all later recordings. It is not uncommon for young adults to simply own a mobile phone instead of a land-line for their residence.

Many other top recording artists were early adherents of digital recording. In many countries, mobile phones now outnumber land-line telephones, with most adults and many children now owning mobile phones. It was unmixed, being recorded straight to a two-track 3M digital recorder in the studio. In less than twenty years, mobile phones have gone from being rare and expensive pieces of equipment used by businesses to a pervasive low-cost personal item. The first digitally recorded (DDD) popular music album was Ry Cooder's Bop Till You Drop, recorded in late 1978. In other countries, such as the United States, Japan, and South Korea, legislation does not require any particular standard, and GSM coexists with other standards, such as CDMA. (Unmixed analog recordings are likewise usually described as ADD to denote a single generation of analog recording). All European nations and some Asian nations legislated it as their sole standard.

These unmixed digital recordings are still described as DDD since the technology involved is purely digital. This is due to the equipment manufacturers working to meet one of a few standards, particularly the GSM standard which was designed for Europe-wide interoperability. In most cases there was no mixing stage involved; a stereo digital recording was made and used unaltered as the master tape for subsequent commercial release. The mobile phone has become ubiquitous because of the interoperability of mobile phones across different networks and countries. The first 16-bit PCM recording in the United States was made by Thomas Stockham at the Santa Fe Opera in 1976 on a Soundstream recorder. The availability of Prepaid or pay as you go services, where the subscriber does not have to commit to a long term contract, has helped fuel this growth. Commercial digital recording of classical and jazz music began in the early 1970s, pioneered by Japanese companies such as Denon, although experimental recordings exist from the 1960s. At present India and China have the largest growth rates of cellular subscribers in the world.

Often this code was accompanied by a short description such as "Full Digital Recording" for DDD and "Digitally Mixed Analog Recording" for ADD. In most of Europe, wealthier parts of Asia and Latin America, Australia, Canada and the United States, mobile phones are now widely used, with the majority of the adult, teenage, and even child population owning one. Almost all early CDs are "AAD" (analog recording and mixing, digital transfer to CD) as a result. Due to their low establishment costs and rapid deployment, mobile phone networks have since spread rapidly throughout the world, outstripping the growth of fixed telephony. The first letter represents how the album was recorded, the second how it was mixed, and the third how it was transferred (inevitably a D, as the CD is a digital medium). Radio phones have a long and varied history that stretches back to the 1950s, with hand-held cellular radio devices being available since 1983. Many CDs, especially classical music and many popular recordings, come with a three-letter code printed on the back known as the SPARS (acronym for Society of Professional Audio Recording Studios) Code, where "A" stands for analog and "D" stands for digital. .

Note that the CD+G or “karaoke” extension also uses the R-W subchannels or subcodes to store low resolution graphics. Mobile phones are also distinct from cordless telephones, which generally operate only within a limited range of a specific base station. ITTS is also used by Digital Audio Broadcasting or the MiniDisc. There are also specialist communication systems related to, but distinct from mobile phones, such as satellite phones and Professional Mobile Radio. The text is stored in a format usable by the Interactive Text Transmission System (ITTS). Some of the world's largest mobile phone manufacturers include Alcatel, Audiovox, Fujitsu, Kyocera (formerly the handset division of Qualcomm), LG, Motorola, NEC, Nokia, Panasonic (Matsushita Electric), Philips, Sagem, Samsung, Sanyo, Sharp, Siemens, SK Teletech, Sony Ericsson, and Toshiba. About 31 megabytes of information can be stored there. In addition to the standard voice function of a telephone, a mobile phone can support many additional services such as SMS for text messaging, packet switching for access to the Internet, and MMS for sending and receiving photos and video.

The information is stored in the lead-in area of the CD, where there is roughly five kilobytes of space available, or in the R through W Subchannels on the disc, which are not used by strict Red Book CDs. The mobile phone communicates via a cellular network of base stations, or cell sites, which are in turn linked to the conventional telephone network. album name, song name, and artist) on a standards-compliant audio CD. Most current mobile phones connect instead to the network using a wireless radio wave transmission technology. It allows for storage of additional information (e.g. A mobile phone or cell phone is an electronic telecommunications device with the same basic capability as a conventional fixed-line telephone, but which is also entirely portable and is not required to be connected with a wire to the telephone network. CD-Text is part of the CD+G extension to the Red Book standard for audio CDs. The GPS technology already available in some phones, while coupled with the camera phone, may also allow users in the future to not only take a picture, but snap the exact location and angle at which the picture was taken.

Channels R…W are unused by Red-Book compliant CDs, and have been used for extensions to the standard. This would likely lead to maps and help finding where you are going, and supports social efforts, such as locating friends or group members nearby, and identifying some strangers. The ISRC is used by the media industry, and contains information about the country of origin, the year of publication, owner of the rights, as well as a serial number, and some additional tags:. In the future, GPS positioning may be coupled with accelerometer positioning, for covering underground or indoor positioning. It contains positioning information, the Media Catalog Number (MCN), and International Standard Recording Code (ISRC). There are several cell phones that can perform GPS positioning. Channel Q is used for control purposes of more sophisticated players. But it is likely that the bandwidth to communicate the video, and receive a processed model will exist.

Quite a few players ignore it in favor of the Q Channel. It is unlikely that cell phones will have the processing power to construct models and textures. Channel P is a simple pause/music flag, which can be used for low-cost search systems. With time, this may develop into full 3D texturing and modeling. These streams are called "channels", and are labeled starting with the letter P, like so:. Image scanning, as seen in existing research [2] [3]. Each of these bits corresponds to a separate stream of information. These methods avoid swamping the network by using traditional broadcasting.

Each of the 96 subchannel data bytes can be thought of as being divided into eight bits. The delivery of multimedia content including video to mobiles is beginning to become a reality with two main competing standards DMB - Digital Multimedia Broadcasting - and DVB-H - a handset version of the Digital Video Broadcasting standard. 1 byte for command, 1 byte for instruction, 2 bytes for parityQ, 16 bytes for data, and 4 bytes parityP. The technology is proving popular and there are now even vending machines that accept this form of payment. The 96 bytes of subchannel information in each sector contain four packets of 24 bytes apiece:. By charging up a phone with pre-paid cash credits, it can act as a sophisticated mobile-phone wallet. In each sector there are 2352 bytes (24×98) of audio content data and 96 bytes of subchannel data. The system, pioneered by NTT DoCoMo and SonyEricsson, is called Felica and there are around 10,000 convenience stores where one can now use a phone to pay for goods just by 'swiping' it over a flat reader.

Thus each channel has a bit rate of 7.35 (=44.1/6) kbit/s. New technology in Japan has combined the RFID chip principle into the handset and hooked it up to a network of readers and interfaces. The eight bits are used as eight different subcoding channels, and given letters designating their usage: P, Q, …, W. Directly tapping into the inner ear or the auditory nerve is already technologically feasible and will become practical as surgical methods advance. The eight bits of a subcode byte are available for control and display. In addition, the implant was only designed to receive signals, not transmit them. A frame comprises 33 bytes, of which 24 are audio bytes (six full stereo samples), eight error correction, CIRC-generated, bytes plus one subcode byte. The implant is currently powered externally, given that no current power source is small enough to fit inside the tooth with it.

The data in a CD are arranged in frames. Sound is transmitted via radio waves from another device (presumably a mobile phone) and received by the implant. Besides digital audio, a CD contains digital data called "subcode", which is multiplexed with the digital audio. This device consists of a radio receiver and transducer, which transmits the sound via bone conduction through the jawbone into the ear. ... Speculative improvements in the future may be inspired by an English team led by James Auger and Jimmy Loizeau who in 2002 developed an implant designed to be inserted into a tooth during dental surgery. An audio CD has a very different structure:. However, different display technologies, such as OLED displays, e-paper or retinal displays, smarter communication hardware (directional antennae, multi-mode and peer-to-peer phones) may reduce power requirements, while new power technologies such as fuel cells may provide better energy capacity.

A CD-ROM (data) sector contains 2352 bytes:. Colour screens and additional functions put increasing demands on the device's power source, and battery developments may not proceed sufficiently fast to compensate. A 1x speed CD drive reads 75 consecutive sectors per second. Further improvements in battery life will be required. The playing time is 74 minutes, or 4440 seconds, so that the net capacity of a Mode-1 CD-ROM is 682 MB. The new standard (UMA) has been developed for this. The net byte rate of a Mode-1 CD-ROM is 44.1k×2048/(6×98) = 153.6 kB/s. The emergence of integration capabilities with other unlicensed access technologies such as a WiMAX and WLAN, as well as allowing handover between traditional operator networks supporting GSM, CDMA and UMTS to unlicensed mobile networks.

In a Mode-2 CD-ROM, which is mostly used for video files, there are 2336 user-available bytes per sector. Developments in podcast software enables mobile phones to become podcast playback devices through existing channels like MMS Podcast, J2ME Podcast and AMR-NB Podcast. A Mode-1 CD-ROM, which has the full third layer error correction capability, contains a net 2048 bytes of the available 2352 per sector. Developments in miniaturised hard disks and flash drives to solve the storage space issue are already surfacing, therefore opening a window for phones to become portable music libraries and players similar to the iPod. Note that the CIRC error correction system used in the CD audio format has two interleaved layers. Examples of companies that are currently developing this technology are Neomedia (via Paperclick), Mobot and Scanbuy. In order to achieve improved error correction and detection, a CD-ROM has a third layer of Reed-Solomon error correction. Searches can also be personalized to local areas using a GPS system built in to cell phones.

The CD-ROM is in essence a data disc, which cannot rely on error concealment, and it requires therefore a higher reliability of the retrieved data. This technology can be extended to RFID tags, or even snapped pictures of company logos. A CD-ROM sector contains 98 frames, and holds 98×24 = 2352 bytes. Phones equipped with barcode reader-enabled cameras will be able to snap photos of barcodes and direct the user to corresponding sites on the Internet. The synchronization word cannot occur in the normal bit stream, and can thus be used to identify the beginning of a frame. New technologies are being explored that will utilize the Extended Internet and enable mobile phones to treat a barcode as a URL tag. A 27-bit unique synchronization word is added, so that the number of channel bit in a frame totals 588. However, to support more natural speech recognition and translation, a drastic improvement in the state of technology in these devices is required.

In total we have 33*(14+3) = 561 channel bits. Many phones already have rudimentary speech recognition in a form of voice dialing. The eight bits of a subcode byte are available for control and display. Mobile phones will include various speech technologies as they are being developed. A frame comprises 33 bytes, of which 24 are audio bytes (six full stereo samples), eight error correction, CIRC-generated, bytes plus one subcode byte. Examples of companies that are currently developing this technology are Digital Airways with the Kaleido product, e-sim, mobile arsenal, and Qualcomm with UIOne for the BREW environment. Data in a CD-ROM are organized in both frames and sectors. New solutions are being developed to create new MMI more easily and let manufacturers and operators experiment new concepts.

2×2×6 = 24 bytes. An important area of evolution relates to the Man Machine Interface. A frame can accommodate six complete 16-bit stereo samples, i.e. Currently it is only available in stand-alone devices, such as Ectaco translators. The smallest entity in the CD audio format is called a frame. One function that would be useful in phones is a translation function. Each 14-bit EFM word alternates with a 3-bit merging word. However, this may be solved using folding e-paper or built-in projectors.

Each 14 consecutive bits are grouped and decoded using Eight-to-Fourteen Modulation to get a byte. For example, ebooks may well become a distinct device, because of conflicting form-factor requirements — ebooks require large screens, while phones need to be smaller. As bit-times are counted off, a transition (pit-to-land, or land-to-pit) is interpreted as a "1" bit, while a constant region (all-land or all-pit) is interpreted as a "0" bit. One difficulty in adapting mobile phones to new uses is form factor. Under a microscope, all that is visible is a series of various-sized pits arranged in a long spiral, starting near the inner hole. A "4.7 GB" DVD has a nominal capacity of about 4.38 GiB.

But DVD capacities are given in decimal units. A "700 MB" (or "80 minute") CD has a nominal capacity of about 700 MiB. CD capacities are always given in binary units. However, attempts to combine double LPs onto one CD occasionally resulted in an opposing situation in which the CD would actually offer fewer tracks than the LP equivalent.

CDs would often be released with one or more bonus tracks, enticing consumers to buy the CD for the extra material. The 74-minute playing time of a CD, being more than that of most long-playing vinyl albums, was often used to the format's advantage during the early years when CDs and LPs vied for commerical sales. However, these discs can cause problems in playback when the end of the disc is reached. Another technique to increase the capacity of a disc is store data in the lead out groove that is normally used to indicate the end of a disk, and an extra minute or two of recording is often possible.

This is the limit for most conventional audio CDs today. Using a linear velocity of 1.2 m/s and a track pitch of 1.5 micrometre leads to a playing time of 80 minutes, or a capacity of 700 MB. A disc with data appearing slightly more densely is allowable. If the disc diameter were 115 mm, the maximum playing time would have been 68 minutes, i.e., six minutes less.

With a scanning speed of 1.2 m/s, the playing time is 74 minutes, or around 650 MB of data on a CD-ROM. The program area is 86.05 cm², so that the length of the recordable spiral is 86.05/1.6 = 5.38 km. The main parameters of the CD (taken from the September 1983 issue of the compact disc specification) are as follows:. The Sony PCM-1610 and PCM-1630 are well known examples of PCM adaptors used in conjunction with the Sony U-matic VCR.

There was a long debate over whether to use 14 or 16 bit samples and/or 44,056 or 44,100 samples/s when the Sony/Philips task force designed the compact disc; 16 bits and 44.1 kilo-samples/s prevailed. This system could either store 14-bit samples with some error correction, or 16-bit samples with almost no error correction. Similarly PAL has 294 lines and 50 fields, which gives 44,100 samples/s. A standard NTSC video signal has 245 usable lines per field, and 59.94 fields/s, which works out at 44,056 samples/s.

This technology could store six samples (three samples per each stereo channel) in a single horizontal line. A device that turns an analog audio signal into PCM audio, which in turn is changed into an analog video signal is called a PCM adaptor. The sampling rate of 44.1 kHz is inherited from a method of converting digital audio into an analog video signal for storage on video tape, which was the most affordable way to store it at the time the CD specification was being developed. Reed-Solomon error correction allows the CD to be scratched to a certain degree and still be played back.

In broad terms the format is a two-channel (four-channel sound is an allowed option within the Red Book format, but has never been implemented) stereo 16-bit PCM encoding at a 44.1 kHz sampling rate. Philips is responsible for the licensing program of the intellectual property pertinent to the Compact Disc including the "Compact Disc Digital Audio" logo that appears on the disc. The format of the audio disc, known as the "Red Book" / Sony standard, was laid out by Sony and Philips in 1981. Bulk packaging can be done before or after printing.

Sometimes the spindle of 150 discs are shrinkwrapped together in bulk. The finished assembly has security stickers applied, and is shrinkwrapped with marketing stickers applied. Printing and Packaging: The label is printed onto the disc using a one to six color process (in the case of silk screening), then the printed discs are loaded into a packaging macine that combines a jewel box, tray card, the disc, and booklet. The discs are sampled by QC to ensure quality product.

A laquer is spin coated onto the disc and the disc is tranfered to a spindle. At this point the disc is clear, so a coating of aluminum or gold is applied to the disc for reflectivity. The chamber opens and a robotic arm grabs the disc and transfers it to the next stage. Melted polycarbonate resin is injected into the chamber and the CD is pressed using up to 40 tons of pressure.

Pressing: Each stamper is mounted in an injection moulding machine. This process is also done in a clean room environment. Each stamper is quality checked. Multiple stampers can be made from one glass master.

Stamper Process: Next the glass master is used to create nickel stampers using an electroplating technique. The glass master produced is quality checked before it moves to the next stage. Source material is encoded into the appropriate format whereupon a computer controlled machine "burns" the pits into the emulsion layer of the glass master. The glass is coated with an emulsion.

The nickel is transfered by exciting the nickel to a plasma state whereupon a thin layer of nickel will adhere to the glass. Mastering Process: First, in a clean room, a glass master is prepared by coating a perfectly flat piece of half inch thick circular glass with a layer of nickel. Discs are consequently much easier to ruin by scratching the label side, whereas clear-side scratches can be repaired by refilling them with plastic of similar index of refraction. Pits are much closer to the label side of a disc so that defects and dirt on the clear side can be out of focus during playback.

Most CD manufacturers, dependent on the exact pit geometry such as the slope of the pit edges etc, choose a pit depth of around 90-100 nm, (which is around λ/6n) yielding a sound trade-off between the quality of the push-pull radial tracking and full aperture detection signal. For a maximum push-pull radial tracking signal the best choice is λ/8n = 65 nm. For a maximum full aperture signal, the optimum pit depth is λ/4n = 130 nm (refractive index n=1.5, λ=780 nm). However, the Red Book implicitly specifies the pit depth by specifying the strength of both the push-pull radial tracking signal and full aperture detection signal.

It specifies that the pit depth should be less than (and, thus, not equal) 130 nm. Figure 1, page 8a, of the Red Book specifies many mechanical parameters including the pit depth. This in turn is decoded by reversing the Eight-to-Fourteen Modulation used in mastering the disc, finally revealing the raw data stored on the disc. Instead a change from pit to land or land to pit indicates a one, while no change indicates a zero.

The pits and lands themselves do not represent the zeroes and ones of binary data. By measuring this intensity with a photodiode, one is able to read the data from the disc. The destructive interference thus reduces the intensity of the reflected light compared to when the laser is focused on just a land. The difference in height between pits and lands is one quarter to one sixth of the wavelength of the laser light, leading to a half-wavelength or less phase difference between the light reflected from a pit and from its surrounding land.

A CD is read by focusing a 780 nm wavelength semiconductor laser through the bottom of the polycarbonate layer. The spiral begins at the center of the disc and proceeds outwards to the edge, which allows the different size formats available. To grasp the scale of the pits and land of a CD, if the disc is enlarged to the size of a stadium, a pit would be approximately the size of a grain of sand. The spacing between the tracks is 1.6 μm.

(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 long. The information on a standard CD is encoded as a spiral track of pits moulded into the top of the polycarbonate layer. There is a 15 mm hole in the centre of the disc, usually used by some form of clamp or clip device within the player to hold it in place and allow it to be rotated by a motor. Some irregularly shaped discs will work with tray loading CD drives if they include a circular ridge on their underside which centers them on the part of the tray designed to hold 80 mm CDs, assuming the tray has such a feature.

Irregularly shaped, non rotationally symmetric discs with an offset centre of mass may also cause damaging vibration if played in computer CD drives, which can operate at a much higher rotational velocity than stand-alone audio CD players. Examples include Business Card CDs in the shape of a rectangular card and CDs shaped like the map of a country etc, although such discs are not always compatible with all CD players — they will work with any machine where the disc is inserted by manually clipping it onto the spindle (the mechanism used in virtually all portable CD players), but may not necessarily be inserted into drives which load the disc from a tray, or pull it into a slot. Other unique shapes and smaller form factors have also been sold or given away as promotional items. Each such "miniCD" or "Maxi CD" can hold 21 minutes of music, or 180 MB of data (this form factor has also been called "CD3", since it is about three inches across).

Japan), much like the old vinyl single. 80 mm discs are also available, a format which is mainly used for audio CD singles in some regions (e.g. Such a standard disc weighs 15 grams. By far the most common is 120 mm in diameter, with a 74-minute audio capacity and a 650 MB data or a 80-minute audio capacity and a 700 MB data (See storage capacity; this form factor has also erroneously been called "CD5" since it is 4 3/4 inches in diameter, about five inches across).

CDs are available in two sizes. Common printing methods for compact discs are silkscreening and offset printing. The lacquer can be printed with a label. Compact discs are made from a 1.2 mm thick disc of polycarbonate plastic coated with a much thinner layer of Super Purity Aluminium (or rarely, gold, used for its data longevity, such as in some limited-edition audiophile CDs) layer which is protected by a film of lacquer.

The CD and its later extensions have been extremely successful: in 2004 the annual worldwide sales of CD-Audio, CD-ROM, and CD-R reached about 30 billion discs. A user-recordable CD for data storage, CD-R, was introduced in the early 1990s, and it became the de facto standard for exchange and archiving of computer data and music. A CD can store around 640 megabytes of data. With this it was now possible to disseminate massive amounts (for the time) of computer data instead of digital sound.

Two years later, in 1985, the CD-ROM (read-only memory) was introduced. From its origins as a music format, Compact Disc has grown to encompass other applications. [2]. It spurred the sale of compact disc players like no other recording before it, helped to drive down the price of players, induced other acts and record labels to release more music on CD and firmly established the format in the mind of the average consumer.

One of the first all-digital rock recordings and the first by a major act, Brothers in Arms played to the strengths of the CD by offering more and longer tracks, running ten minutes longer than the album's concurrent LP and cassette releases. This "highbrow niche" status of the CD format changed dramatically in May, 1985, when UK rock band Dire Straits released the album Brothers in Arms. The far larger popular and rock music industries were slower to adopt the new format, especially in the huge consumer markets in Europe and the United States. The new audio disc was enthusiastically received, especially in the early-adopting classical music and audiophile communities and its handling quality received particular praise.

This event is often seen as the "Big Bang" of the digital audio revolution. The Compact Disc reached the market in late 1982 in Asia and early the following year in other markets. According to Philips, the Compact Disc was thus "invented collectively by a large group of people working as a team."[1]. The Compact Disc Story, told by a former member of the taskforce, gives background information on the many technical decisions made, including the choice of the sampling frequency, playing time, and disc diameter.

Philips also contributed the Eight-to-Fourteen Modulation, EFM, which offers both a large playing time and a high resilience against disc handling damage such as scratches and fingerprints; while Sony contributed the error-correction method, CIRC. Philips contributed the general manufacturing process, based on the video Laserdisc technology. After a year of experimentation and discussion, the taskforce produced the "Red Book", the Compact Disc standard. Prominent members of the task force were Kees Immink and Toshitada Doi.

In 1979 Philips and Sony decided to join forces, setting up a joint task force of engineers whose mission was to design the new digital audio disc. At the end of the 1970s, Philips, Sony, and other companies presented prototypes of digital audio discs. In the early 1970s, using video Laserdisc technology, Philips' researchers started experiments with "audio-only" optical discs, initially with wideband frequency modulation FM and later digitized PCM audio signals. .

Online services such as CDDB were developed to work around these shortcomings in the computer age. As a result, the original CD format has a number of limitations; no built-in track names or disc naming for example. Only later did the concept of an 'audio file' arise, and the generalising of this to any data file. The design of the CD was originally conceived as an evolution of the gramophone record, rather than primarily as a data storage medium.

Compact disc technology was later adapted for use as a data storage device, known as a CD-ROM. They hold about 20 minutes of audio. The 80 mm discs are used as "CD-singles" or novelty "business-card CDs". The 120 mm discs can hold 74 minutes of audio, and versions holding 80, 90 or even 99 minutes have been introduced.

Standard compact discs have a diameter of 120 mm, though 80 mm versions exist in circular and "business-card" forms. An audio CD consists of several stereo tracks stored using 16-bit PCM coding at a sampling rate of 44.1 kHz. A standard compact disc, often known as an "audio CD" to differentiate it from later variants, stores audio data in a format compliant with the red book standard. It is the standard playback format for commercial audio recordings today.

A compact disc (or CD) is an optical disc used to store digital data, originally developed for storing digital audio. ISBN 895793008. Middleton, Wisconsin: A-R Editions. The Compact Disc Handbook.

Pohlmann (1992). Kenneth C. 458-465, May 1998 [4]. Kees Immink, The Compact Disc Story, AES Journal, pp.

AAD: analog tape recorder used during session recording and subsequent mixing and/or editing, digital tape recorder used during mastering (transcription). ADD: analog tape record used during session recording, digital tape recorder used during subsequent mixing and/or editing and during mastering (transcription). DDD: digital tape recorder used during session recording, mixing and/or editing, and mastering (transcription). 276 bytes: error correction.

8 bytes: null. 4 bytes: error detection. 2 048 bytes: user data. 4 bytes: sector ID.

12 bytes: sync. Outer radius program area: 58 mm. Inner radius program area: 25 mm. Disc thickness: 1.2 mm.

Disc diameter 120 mm. Track pitch: 1.6 μm. Scanning velocity: 1.2–1.4 m/s (constant linear velocity) - Equivalent to about 500 rpm at the inside of the disc, or about 200 rpm at the outside edge.