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Compact Disc Digital Audio

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Compact Disc Digital Audio
Media typeOptical disc
Encoding2 channels ofLPCMaudio, eachsigned16-bitvalues sampled at 44100Hz
Capacityup to 74–80 minutes (up to 24 minutes for mini 8 cm CD)
ReadmechanismSemiconductor laser(780 nm wavelength)
StandardIEC 60908
DevelopedbySony&Philips
UsageAudio storage
ExtendedtoDVD-Audio
Released1982
Optical discs
General
Optical media types
Standards
See also

Compact Disc Digital Audio(CDDAorCD-DA), also known asDigital Audio Compact Discor simply asAudio CD,is thestandardformat for audiocompact discs.The standard is defined in theRed Booktechnical specifications,which is why the format is also dubbed"Redbook audio"in some contexts.[1]CDDA utilizespulse-code modulation(PCM) and uses a44,100 Hzsampling frequency and 16-bit resolution, and was originally specified to store up to 74 minutes ofstereoaudio per disc.

The first commercially available audioCD player,theSony CDP-101,was released in October 1982 in Japan. The format gained worldwide acceptance in 1983–84, selling more than a million CD players in its first two years, to play 22.5 million discs,[2]before overtakingrecordsandcassette tapesto become the dominant standard for commercial music. Peaking around year 2000, the audio CD contracted over the next decade due to rising popularity and revenue fromdigital downloading,and during the 2010s bydigital music streaming,[3]but has remained as one of the primary distribution methods for themusic industry.[4]In the United States, phonograph record revenues surpassed the CD in 2020 for the first time since the 1980s,[5][6]but in other major markets like Japan it remains the premier music format by a distance[7]and in Germany it outsold other physical formats at least fourfold in 2022.[8]

In the music industry, audio CDs have been generally sold as either aCD single(now largely dormant), or as full-lengthalbums,the latter of which has been more commonplace since the 2000s.[9]The format has also been influential in the progression ofvideo game music,used inmixed modeCD-ROMs,providing CD-quality audio popularized during the 1990s on hardware such asPlayStation,Sega Saturnandpersonal computerswith 16-bitsound cardslike theSound Blaster 16.[10][11]

History

[edit]

Theoptophone,first presented in 1931, was an early device that used light for both recording and playback of sound signals on atransparent photograph.[12]More than thirty years later, American inventorJames T. Russellhas been credited with inventing the first system to record digital media on a photosensitive plate. Russell's patent application was filed in 1966, and he was granted a patent in 1970.[13]Following litigation,SonyandPhilipslicensed Russell's patents for recording in 1988.[14][15]It is debatable whether Russell's concepts, patents, and prototypes instigated and in some measure influenced the compact disc's design.[16]

The compact disc is an evolution ofLaserDisctechnology,[17]where a focusedlaserbeam 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.[18]Although originally dismissed byPhilips Researchmanagement as a trivial pursuit,[19]the CD became the primary focus for Philips as theLaserDiscformat struggled.[20]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.[21]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.[22][23]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.[24]

Digital audio laser-disc prototypes

[edit]

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.[25]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.[17][26]

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. In 1973, his team developed a digitalPCM adaptorthat made audio recordings using aBetamaxvideo recorder. After this, in 1974 the leap to storing digital audio on an optical disc was easily made.[27]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) usingmodified frequency modulationencoding.[28]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-interleaved Reed-Solomon coding(CIRC)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 62ndAESConvention, held on 13–16 March 1979, inBrussels.[28]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"[29]inEindhoven,Netherlands.[30]Sony executiveNorio Ohga,later CEO and chairman of Sony, andHeitaro Nakajimawere convinced of the format's commercial potential and pushed further development despite widespread skepticism.[31]

Collaboration and standardization

[edit]
Dutch inventor and Philips chief engineerKees Schouhamer Imminkwas part of the team that produced the standard compact disc in 1980

In 1979, Sony and Philips set up a joint task force of engineers to design a new digital audio disc. Led by engineersKees Schouhamer ImminkandToshitada Doi,the research pushed forwardlaserandoptical disctechnology.[29]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 theIECas an international standard in 1987, with various amendments becoming part of the standard in 1996.[citation needed]

Philips coined the termcompact discin line with another audio product, theCompact Cassette,[26]and contributed the general manufacturingprocess,based on video LaserDisc technology. Philips also contributedeight-to-fourteen modulation(EFM), while Sony contributed theerror-correctionmethod, CIRC, which offers resilience to defects such as scratches and fingerprints.

The Compact Disc Story,[17]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,[19][32]though according to Philips, the compact disc was "invented collectively by a large group of people working as a team".[33]

Initial launch and adoption

[edit]

Early milestones in the launch and adoption of the format included:

  • The firsttest pressingwas of a recording ofRichard Strauss'sAn Alpine Symphony,recorded December 1–3, 1980 and played by theBerlin Philharmonicand conducted byHerbert von Karajan,who had been enlisted as an ambassador for the format in 1979.[34]
  • The world presentation took place during theSalzburg Easter Festivalon 15 April 1981, at a press conference ofAkio Moritaand Norio Ohga (Sony), Joop van Tilburg (Philips), and Richard Busch (PolyGram), in the presence of Karajan who praised the new format.[35]
  • The firstpublic demonstrationwas on theBBCtelevision programmeTomorrow's Worldin 1981, when theBee Gees' albumLiving Eyes(1981) was played.[36]
  • The firstcommercialcompact disc was produced on 17 August 1982, a 1979 recording of Chopin waltzes performed byClaudio Arrau.[37]
  • The first 50 titles werereleasedin Japan on 1 October 1982,[38]the first of which was a re-release of theBilly Joelalbum52nd Street.[39]
  • The first CD played on BBC Radio was in October 1982.[citation needed]
  • The Japanese launch was followed on 14 March 1983 by the introduction of CD players and discs to Europe[40]and North America where CBS Records released sixteen titles.[41]

The first artist to sell a million copies on CD wasDire Straits,with their 1985 albumBrothers in Arms.[42]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 wasDavid Bowie,whose first fourteen studio albums of (then) sixteen were made available byRCA Recordsin February 1985, along with four greatest hits albums; his fifteenth and sixteenth albums had already been issued on CD byEMI Recordsin 1983 and 1984, respectively.[43]On 26 February 1987, the first four UK albums bythe Beatleswere released in mono on compact disc.[44]

The growing acceptance of the CD in 1983 marks the beginning of the popular digital audio revolution.[45]It was enthusiastically received, especially in the early-adoptingclassical musicandaudiophilecommunities, and its handling quality received particular praise. As the price of players gradually came down, and with the introduction of the portableDiscman,the CD began to gain popularity in the larger popular and rock music markets. With the rise in CD sales, pre-recordedcassette tapesales began to decline in the late 1980s; CD sales overtook cassette sales in the early 1990s.[citation needed][46]In 1988, 400 million CDs were manufactured by 50 pressing plants around the world.[47]

Further development

[edit]
SonyDiscmanD-E307CK portable CD player with 1-bit DAC

Early CD players employed binary-weighteddigital-to-analog converters(DAC), which contained individual electrical components for each bit of the DAC.[48]Even when using high-precision components, this approach was prone to decoding errors.[clarification needed][48]Another issue wasjitter,a time-related defect. Confronted with the instability of DACs, manufacturers initially turned to increasing the number of bits in the DAC and using several DACs per audio channel, averaging their output.[48]This increased the cost of CD players but did not solve the core problem.

A breakthrough in the late 1980s culminated in development of the1-bit DAC,which converts high-resolution low-frequency digital input signal into a lower-resolution high-frequency signal that is mapped to voltages and then smoothed with an analog filter. The temporary use of a lower-resolution signal simplified circuit design and improved efficiency, which is why it became dominant in CD players starting from the early 1990s. Philips used a variation of this technique calledpulse-density modulation(PDM),[49]while Matsushita (nowPanasonic) chosepulse-width modulation(PWM), advertising it as MASH, which is an acronym derived from their patented Multi-stAge noiSe-sHaping PWM topology.[48]

The CD was primarily planned as the successor to thevinyl recordfor 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 andJoseph Braatpresented the first experiments with erasable compact discs during the 73rdAES Convention.[50]In June 1985, the computer-readableCD-ROM(read-only memory) and, in 1990, recordableCD-Rdiscs were introduced.[a]Recordable CDs became an alternative to tape for recording and distributing music and could be duplicated without degradation in sound quality.

Other newer video formats such asDVDandBlu-rayuse the same physical geometry as CD, and most DVD and Blu-ray players arebackward compatiblewith audio CDs.

Peak

[edit]

CD sales in the United States peaked by 2000.[51]By the early 2000s, the CD player had largely replaced theaudio cassetteplayer 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.[52]

Two new formats were marketed in the 2000s designed as successors to the CD: theSuper Audio CD(SACD) andDVD-Audio.However neither of these were adopted partly due to increased relevance of digital (virtual) music and the apparent lack of audible improvements in audio quality to most human ears.[53]These effectively extended the CD's longevity in the music market.[54]

Decline

[edit]

With the advent and popularity ofInternet-based distributionof files inlossy-compressedaudio formatssuch 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%.[55]Despite rapidly declining sales year-over-year, the pervasiveness of the technology lingered for a time, with companies placing CDs in pharmacies, supermarkets, and filling station convenience stores to target buyers less likely to be able to use Internet-based distribution.[20]In 2012, CDs and DVDs made up only 34% of music sales in the United States.[56]By 2015, only 24% of music in the United States was purchased on physical media, two thirds of this consisting of CDs;[57]however, in the same year in Japan, over 80% of music was bought on CDs and other physical formats.[58]In 2018, U.S. CD sales were 52 million units—less than 6% of the peak sales volume in 2000.[51]In the UK, 32 million units were sold, almost 100 million fewer than in 2008.[59]In 2018,Best Buyannounced plans to decrease their focus on CD sales, however, while continuing to sell records, sales of which are growing during thevinyl revival.[60][61][62]

During the 2010s, the increasing popularity of solid-state media and music streaming services caused automakers to remove automotive CD players in favor ofminijackauxiliary inputs, wired connections to USB devices and wirelessBluetoothconnections.[63]Automakers viewed CD players as using up valuable space and taking up weight which could be reallocated to more popular features, like large touchscreens.[64]By 2021, onlyLexusandGeneral Motorswere still including CD players as standard equipment with certain vehicles.[64]

Current status

[edit]

CDs continued to be strong in some markets such as Japan where 132 million units were produced in 2019.[65]

The decline in CD sales has slowed in recent years; in 2021, CD sales increased in the US for the first time since 2004,[66]withAxiosciting its rise to "young people who are finding they like hard copies of music in the digital age".[67]It came at the same time as both vinyl and cassette reached sales levels not seen in 30 years.[68]The RIAA reported that CD revenue made a dip in 2022, before increasing again in 2023 and overtook downloading for the first time in over a decade.[69]

In the US, 33.4 million CD albums were sold in the year 2022.[70]InFrancein 2023, 10.5 million CDs were sold, almost double that of vinyl, but both of them represented generated 12% each of the French music industry revenues.[71]

Awards and accolades

[edit]

Sony and Philips received praise for the development of the compact disc from professional organizations. These awards include:

  • TechnicalGrammy Awardfor Sony and Philips, 1998.[72]
  • IEEEMilestone award, 2009, for Philips alone 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."[73]

Standard

[edit]

TheRed Bookspecifies the physical parameters and properties of the CD, the optical parameters, deviations and error rate, modulation system (eight-to-fourteen modulation,EFM) and error correction facility (CIRC), and the eightsubcode channels.These parameters are common to all compact discs and used by all logical formats: audio CD,CD-ROM,etc. The standard also specifies the form ofdigital audioencoding.

The first edition of theRed Bookwas released in 1980 by Philips and Sony;[74][75]it was adopted by the Digital Audio Disc Committee and ratified by theInternational Electrotechnical Commission(IEC) Technical Committee 100 as aninternational standardin 1987 with the reference IEC 60908.[76]The second edition of IEC 60908 was published in 1999[77]and it replaces the first edition, amendment 1 (1992) and the corrigendum to amendment 1. The IEC 60908 however does not contain all the information for extensions that is available in theRed Book,such as the details forCD-Text,CD+GandCD+EG.[78][79]

The standard is not freely available and must be licensed. It is available from Philips and the IEC. As of 2013,Philips outsources licensing of the standard to Adminius[citation needed],which chargesUS$100for theRed Book,plusUS$50each for theSubcode Channels R-WandCD Text Modeannexes.[80]

Audio format

[edit]

The audio contained in a CD-DA consists of two-channelsigned16-bitLPCMsampled at44,100 Hzand written as alittle-endianinterleaved stream with left channel coming first.

Thesampling rateis adapted from that attained when recording digital audio onvideotapewith aPCM adaptor,an earlier way of storing digital audio.[81][82]: sec. 2.6 An audio CD can represent frequencies up to 22.05 kHz, theNyquist frequencyof the44.1 kHzsample rate.[83]

There was a long debate over the use of 16-bit (Sony) or 14-bit (Philips)quantization,and 44,056 or 44,100 samples/s (Sony) or approximately 44,000 samples/s (Philips). When the Sony/Philips task force designed the Compact Disc, Philips had already developed a 14-bitD/A converter(DAC), but Sony insisted on 16-bit. In the end Sony won, so 16 bits and 44.1 kilosamples per second prevailed. Philips found a way to produce 16-bit quality using its 14-bit DAC by using four timesoversampling.[17]

Some early CDs were mastered withpre-emphasis,an artificial boost of high audio frequencies. The pre-emphasis improves the apparent signal-to-noise ratio by making better use of the channel's dynamic range. On playback, the player applies a de-emphasis filter to restore the frequency response curve to an overall flat one. Pre-emphasis time constants are 50 μs and 15 μs (9.49 dB boost at 20 kHz), and a binary flag in the discsubcodeinstructs the player to apply de-emphasis filtering if appropriate. Playback of such discs in a computer orrippingtoWAVfiles typically does not take into account the pre-emphasis, so such files play back with an incorrect frequency response.[citation needed]FFmpeghas a filter to remove (or apply) the pre-emphasis in order to create standard WAV files, or to create CDs with pre-emphasis.[84]

Four-channel, orquadraphonic,supported was originally intended to be included in CD-DA.[85]TheRed Bookspecification briefly mentioned a four-channel mode in its June 1980,[86]September 1983,[87]and November 1991[88]editions. On the first page, it lays out the "Main parameters" of the CD system, including: "Number of channels: 2 and/or 4 simultaneously[*] sampled." The footnote says, "In the case of more than two channels the encoder and decoder diagrams have to be adapted."

In reality, however, the underspecified "four-channel" mode was dropped from the CD standard when it was adopted by theInternational Electrotechnical Commissionand became IEC 908:1987,[89]and later IEC 60908:1999.[90]Since the behavior of the "four-channel" or "Broadcasting use" bit was never specified by either CD standard, no mass-marketed discs have attempted to use the Red Book's four-channel mode, and no players have purported to implement it.

Storage capacity and playing time

[edit]

The creators of the CD originally aimed at a playing time of 60 minutes with a disc diameter of 100 mm (Sony) or 115 mm (Philips).[19]Sony vice-presidentNorio Ohgasuggested extending the capacity to 74 minutes to accommodate the recording ofWilhelm FurtwänglerconductingLudwig van Beethoven'sNinth Symphonyat the 1951Bayreuth Festival.[91][92]The additional 14-minute playing time required increasing disc diameter.Kees Schouhamer Immink,Philips' chief engineer, however, denies this,[93]claiming that the increase was motivated by technical considerations and that even after the increase in size, the Furtwängler recording would not have fit onto one of the earliest CDs.[17][19]

According to aSunday Tribuneinterview,[94]the story is slightly more involved. In 1979, Philips ownedPolyGram,one of the world's largest music distributors. PolyGram had set up a large experimental CD plant inHannover,Germany, which could produce huge numbers of CDs having a diameter of 115 mm. Sony did not yet have such a facility. If Sony had agreed on the 115-mm disc, Philips would have had a significant competitive edge in the market. The long playing time of Beethoven's Ninth Symphony imposed byOhgawas used to push Philips to accept 120 mm, so that Philips' PolyGram lost its edge on disc fabrication.[94]

The 74-minute playing time of a CD, which is longer than the 22 minutes per side[95][96]typical oflong-playing(LP)vinyl albums,was often used to the CD's advantage during the early years when CDs and LPs vied for commercial sales. CDs would often be released with one or morebonus tracks,enticing consumers to buy the CD for the extra material. However, attempts to combine double LPs onto one CD occasionally resulted in the opposite situation in which the CD would instead offer less audio than the LP. One such example was withDJ Jazzy Jeff & The Fresh Prince's double albumHe's the DJ, I'm the Rapper,in which initial CD releases of the album had multiple tracks edited down for length to fit on a single disc; recent CD reissues package the album across two discs as a result. The emergence of 80-minute CDs allowed for some double albums that were previously edited for length, e.g.1999byPrince,or packaged as double CDs, e.g.Tommybythe Who,to be re-released on a single disc.

Playing times beyond 74 minutes are achieved by decreasing track pitch (the distance separating the track as it spirals the disc). However, most players can still accommodate the more closely spaced data if it is still withinRed Booktolerances.[97]Manufacturing processes used in the final years of CD technology allowed an audio CD to contain up to 98 minutes (variable from one replication plant to another) without requiring the content creator to sign a waiver releasing the plant owner from responsibility if the CD produced is marginally or entirely unreadable by some playback equipment. In this final practice, maximum CD playing time crept higher by reducing minimum engineering tolerances.

Progression in the maximum duration of released audio CDs
Released Time Title Artist Label
1980 50:47[98] Richard Strauss: Eine Alpensinfonie Berlin Philharmonic Orchestra / Herbert von Karajan None. This was the first test pressing of a CD. Later sold commercially byDeutsche Grammophon.
1988 80:08[99] Mission of Burma(compilation) Mission of Burma Rykodisc
1990 98:57 The California RaisinsinBuena Park Buddy Miles Warner Bros. Records/Priority Records
1990 80:51[100] Late Romantic Masterworks Andrew Fletcher Mirabilis Records
1990 82:04[100] JS Bach, Das Orgelbüchlein Richard Marlow Mirabilis Records
1990 96:43 Donna SummerLush Life Donna Summer Warner Bros. Records
1990 96:57 Art of Noisein Hollywood Part 1 Art of Noise China Records/Polydor/Priority Records/BMG
1991 97:04 Art of Noisein Hollywood Part 2 Art of Noise China Records/Polydor/Priority Records/BMG
1991 90:05 The California RaisinsinWest Covina Buddy Miles Priority Records/ZTT/BMG
1991 93:05 The Beach BoysinHuntington Beach The Beach Boys Capitol Records
1992 95:36 The Beach BoysonNBC The Beach Boys Capitol Records/ZTT
1993 99:03 The Beach Boyson Fox 11 The Beach Boys Capitol Records
2003 80:12[101] Myこれ!クション nội hải hòa tử ベスト(My Kore! Kushon Kazuko Utsumi Best) compilation Nội hải hòa tử(Kazuko Utsumi) Pony Canyon– PCCA-01870
2004 82:34[102] Bruckner'sFifth(live) Munich Philharmoniccond.Christian Thielemann Deutsche Grammophon/Universal Classics 477 5377
2005 82:34[103] Sergey Tanyiev works for piano and ensemble Vadim Repin, Ilya Gringolts, Nobuko Imai, Lynn Harrell, and Mikhail Pletnev Deutsche Grammophon/Universal Classics 477 5419
2006 88:41 on disc 1, 89:07 on disc 2[104][unreliable source?] Bäst of Die Ärzte Hot Action/Universal 930 003
2014 85:16[105] Chopin & Schumann Etudes Valentina Lisitsa Decca/Universal Classics 478 7697
2014 85:10 and 85:57[106] So80s Presents Alphaville Alphaville(curated byBlank & Jones) Soulfood
2016 86:30[107] Mozart Violin Concertos (Mozart 225 Boxed Set, CD75) Various Artists Deutsche Grammophon/Universal Classics 478 9864

Technical specifications

[edit]

Data encoding

[edit]

Each audio sample is asigned16-bittwo's complementinteger,which has sample values ranging from −32768 to +32767. The source audio data is divided into frames, containing twelvesampleseach (six left and six right samples, alternating), for a total of 192 bits (24 bytes) of audio data per frame.

This stream of audio frames is then subjected to CIRC encoding, which segments and rearranges the data and expands it with error correction codes in a way that allows occasional read errors to be detected and corrected. CIRC encoding interleaves the audio frames throughout the disc over several consecutive frames so that the information will be more resistant toburst errors.Therefore, a physical frame on the disc will actually contain information from multiple logical audio frames. This process adds 64 bits of error correction codes to each frame. After this, 8 bits ofsubcode dataare added to each of these encoded frames, which is used for control and addressing when playing the CD.

CIRC encoding plus the subcode byte generates 33-byte long frames, calledchannel-dataframes. These frames are then modulated througheight-to-fourteen modulation(EFM), where each 8-bit byte is replaced with a corresponding 14-bit word designed to reduce the number of transitions between 0 and 1. This reduces the density ofphysical pitson the disc and provides an additional degree of error tolerance. Threemergingbits are added before each 14-bit word for disambiguation and synchronization. In total, there are 33 × (14 + 3) = 561 bits. A 27-bit word (a 24-bit pattern plus 3 merging bits) is added to the beginning of each frame to assist with synchronization, so the reading device can locate frames easily. With this, a frame ends up containing 588 bits ofchannel datawhich are decoded to 192 bits of digital audio.

The frames of channel data are finally written to disc physically in the form ofpits and lands,with each pit or land representing a series of zeroes, and with the transition points—the edge of each pit—representing a 1. ARed Book-compatibleCD-Rhas pit-and-land-shaped spots on a layer of organic dye instead of actual pits and lands; a laser creates the spots by altering the reflective properties of the dye.

Due to the weaker error correctionsector structureused on audio CDs andvideo CDs(Mode 2 Form 2) than on data discs (Mode 1orMode 2 Form 1),C2 errorsare not correctable and signify data loss.[108][109]Even with uncorrectable errors, a compact disc player useserror concealmentwith the aim of making the damage unhearable.[110]

Data structure

[edit]
Some of the visible features of an audio CD, including the lead-in, program area, and lead-out. A microscopic spiral of digital information begins near the disc's center and progresses toward the edge.

The audio data stream in an audio CD is continuous, but has three parts. The main portion, which is further divided into playable audio tracks, is theprogram area.This section is preceded by alead-intrack and followed by alead-outtrack. The lead-in and lead-out tracks encode only silent audio, but all three sections containsubcodedata streams.

The lead-in's subcode contains repeated copies of the disc's Table of Contents (TOC), which provides an index of the start positions of the tracks in the program area and lead-out. The track positions are referenced by absolutetimecode,relative to the start of the program area, in MSF format: minutes, seconds, and fractional seconds calledframes.Each timecode frame is one seventy-fifth of a second, and corresponds to a block of 98 channel-data frames—ultimately, a block of 588 pairs of left and right audio samples. Timecode contained in the subchannel data allows the reading device to locate the region of the disc that corresponds to the timecode in the TOC. The TOC on discs is analogous to thepartition tableonhard drives.Nonstandard or corrupted TOC records are abused as a form ofCD/DVD copy protection,in e.g. thekey2Audioscheme.

Tracks

[edit]
Main article:Track (optical disc) § Audio tracks

The largest entity on a CD is called atrack.A CD can contain up to 99 tracks (including a data track formixed mode discs). Each track can in turn have up to 100 indexes, though players which still support this feature have become rarer over time. The vast majority of songs are recorded under index 1, with thepregapbeing index 0. Sometimeshidden tracksare placed at the end of the last track of the disc, often using index 2 or 3, or using the pregap as index 0 (this latter usage will result in the track playing as the time counter counts down to time 0:00 at the start of the track, index 1.) This is also the case with some discs offering "101 sound effects", with 100 and 101 being indexed as two and three on track 99. The index, if used, is occasionally put on the track listing as a decimal part of the track number, such as 99.2 or 99.3. (Information Society'sHackwas one of very few CD releases to do this, following a release with an equally obscureCD+Gfeature.) The track and index structure of the CD were carried forward to the DVD format as title and chapter, respectively.

Tracks, in turn, are divided into timecode frames (or sectors), which are further subdivided into channel-data frames.

Frames and timecode frames

[edit]
Main article:Track (optical disc) § Sector structure

The smallest entity in a CD is a channel-dataframe,which consists of 33 bytes and contains six complete 16-bit stereo samples: 24 bytes for the audio (two bytes × two channels × six samples = 24 bytes), eight CIRC error-correction bytes, and onesubcodebyte. As described in the "Data encoding" section, after the EFM modulation the number of bits in a frame totals 588.

On aRed Bookaudio CD, data is addressed using theMSF scheme,withtimecodesexpressed in minutes, seconds and another type offrames(mm:ss:ff), where one frame corresponds to 1/75 of a second of audio: 588 pairs of left and right samples. This timecode frame is distinct from the 33-byte channel-data frame described above, and is used for time display and positioning the reading laser. When editing and extracting CD audio, this timecode frame is the smallest addressable time interval for an audio CD; thus, track boundaries only occur on these frame boundaries. Each of these structures contains 98 channel-data frames, totaling 98 × 24 = 2,352 bytes of music. The CD is played at a speed of 75 frames (or sectors) per second, thus 44,100 samples or 176,400 bytes per second.

In the 1990s,CD-ROMand relatedDigital Audio Extraction(DAE) technology introduced the termsectorto refer to each timecode frame, with each sector being identified by a sequentialintegernumber starting at zero, and with tracks aligned on sector boundaries. An audio CD sector corresponds to 2,352 bytes of decoded data. TheRed Bookdoes not refer to sectors, nor does it distinguish the corresponding sections of the disc's data stream except as "frames" in the MSF addressing scheme.

The following table shows the relation between tracks, timecode frames (sectors) and channel-data frames:

Track level Track N
Timecode frame and sector level Timecode frame and sector 1 (2,352 B of data) Timecode frame and sector 2 (2,352 B of data) ...
Channel-data frame level Channel-data frame 1 (24 B of data) ... Channel-data frame 98 (24 B of data) ... ...

Bit rate

[edit]

The audiobit ratefor aRed Bookaudio CD is 1,411,200bits per second(1,411 kbit/s) or 176,400bytes per second;2 channels × 44,100 samples per second per channel × 16 bits per sample. Audio data coming in from a CD is contained in sectors, each sector being 2,352 bytes, and with 75 sectors containing 1 second of audio. For comparison, the bit rate of a "1×"CD-ROMis defined as 2,048 bytes per sector × 75 sectors per second = 153,600 bytes per second. The remaining 304 bytes in a sector are used for additional data error correction.

Data access from computers

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Unlike on aDVDorCD-ROM,there are no "files"on aRed Bookaudio CD; there is only one continuous stream ofLPCMaudio data, and a parallel, smaller set of 8subcodedata streams. Computeroperating systems,however, may provide access to an audio CD as if it contains files. For example,Windowsrepresents the CD's Table of Contents as a set ofCompact Disc Audio track(CDA) files, each file containing indexing information, not audio data. By contrast however,FinderonmacOSpresents the CD's content as an actual set of files, with theAIFF-extension, which can be copied directly, randomly and individually by track as if it were actual files. In reality, macOS performs its own as-needed-rips in the background completely transparent to the user. The copied tracks are fully playable and editable on the user's computer.

In a process calledripping,digital audio extraction software can be used to read CD-DA audio data and store it in files. Commonaudio file formatsfor this purpose includeWAVand AIFF, which simply preface the LPCM data with a shortheader;FLAC,ALAC,andWindows Media Audio Lossless,which compress the LPCM data in ways that conserve space yet allow it to be restored without any changes; and variouslossy,perceptual codingformats likeMP3,AAC,andOpus,which modify and compress the audio data in ways that irreversibly change the audio, but that exploit features of human hearing to make the changes difficult to discern.

Format variations

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Recording publishers have created CDs that violate theRed Bookstandard. Some do so for the purpose ofcopy prevention,using systems likeCopy Control.Some do so for extra features such asDualDisc,which includes both a CD layer and a DVD layer whereby the CD layer is much thinner, 0.9 mm, than required by theRed Book,which stipulates a nominal 1.2 mm, but at least 1.1 mm. Philips and many other companies have stated that including the Compact Disc Digital Audio logo on such non-conforming discs may constitute trademark infringement.

Super Audio CDwas a standard published in 1999 that aimed to provide better audio quality than CDs.DVD-Audioemerged at around the same time.[111]Both formats were designed to feature audio of higher fidelity by using a higher sampling rate andDVDmedia. Neither format was widely accepted.

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Main article:Compact Disc and DVD copy protection

There have been moves by therecording industryto make audio CDs (Compact Disc Digital Audio) unplayable on computerCD-ROMdrives, to prevent the copying of music. This is done by intentionally introducing errors onto the disc that the embedded circuits on most stand-alone audio players can automatically compensate for, but which may confuse CD-ROM drives. Consumer rights advocates as of October 2001 pushed to require warning labels on compact discs that do not conform to the official Compact Disc Digital Audio standard (often called theRed Book) to inform consumers which discs do not permit fullfair useof their content.

In 2005,Sony BMG Music Entertainmentwas criticized when a copy protection mechanism known asExtended Copy Protection(XCP) used on some of their audio CDs automatically and surreptitiously installed copy-prevention software on computers (seeSony BMG copy protection rootkit scandal). Such discs are not legally allowed to be called CDs or Compact Discs because they break theRed Bookstandard governing CDs, and Amazon.com for example describes them as "copy protected discs" rather than "compact discs" or "CDs".

See also

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Notes

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  1. ^The world's first CD-R was made by the Japanese firmTaiyo YudenCo., Ltd. in 1988 as part of the joint Philips-Sony development effort.

References

[edit]
  1. ^"Redbook Audio (Concept)".Giant Bomb.Retrieved28 August2024.
  2. ^Pohlmann, Ken C. (2000).Principles of Digital Audio.McGraw-Hill. p. 244.ISBN978-0-07-134819-5.
  3. ^"IFPI publishes Digital Music Report 2015".14 April 2015.Archivedfrom the original on 14 April 2015.Retrieved1 July2016.
  4. ^Plambeck, Joseph (30 May 2010)."As CD Sales Wane, Music Retailers Diversify".The New York Times.Archivedfrom the original on 1 May 2017.
  5. ^"Vinyl Outsells CDs For the First Time in Decades".10 September 2020.Archivedfrom the original on 22 September 2020.Retrieved22 September2020.
  6. ^"Mid-Year 2020 RIAA Revenue Statistics"(PDF).Riaa.com.Archived(PDF)from the original on 9 May 2023.Retrieved2 June2023.
  7. ^"3 observations on… how Japan's music industry caters to (and relies on) 'superfans' more than any other market".Music Business Worldwide.23 October 2023.Retrieved3 May2024.
  8. ^"Statistik | Absatz von physischen Tonträgern und digitalen Musikprodukten".miz.org(in German).Retrieved3 May2024.
  9. ^"1999: The Year the Record Industry Lost Control".theafterword.co.uk.Retrieved3 May2024.
  10. ^Collins, Karen.From Bits to Hits: Video Games Music Changes its Tune.School of Music, University of Windsor.
  11. ^"Group Test: 90MHz Pentiums - Sound cards".Personal Computer World.Vol. 18, no. 9. September 1995.
  12. ^"Das Photo als Schalplatte"(PDF)(in German).Archived(PDF)from the original on 4 April 2016.Retrieved2 July2020.
  13. ^US 3,501,586,"Analog to digital to optical photographic recording and playback system", published 1970-03-17
  14. ^"Inventor and physicist James Russell '53 will receive Vollum Award at Reed's convocation"(Press release). Reed College public affairs office. 2000. Archived fromthe originalon 9 October 2013.Retrieved24 July2014.
  15. ^"Inventor of the Week – James T. Russell – The Compact Disc".MIT.December 1999. Archived fromthe originalon 17 April 2003.
  16. ^Brier Dudley (29 November 2004)."Scientist's invention was let go for a song".The Seattle Times.Archived fromthe originalon 10 August 2014.Retrieved24 July2014.
  17. ^abcdeK. Schouhamer Immink(1998)."The Compact Disc Story".Journal of the Audio Engineering Society.46(5): 458–460.Archivedfrom the original on 19 April 2023.Retrieved6 February2018.
  18. ^"The History of the CD".Philips Research. Archived fromthe originalon 23 May 2016.Retrieved7 June2014.
  19. ^abcdK. Schouhamer Immink(2007)."Shannon, Beethoven, and the Compact Disc".IEEE Information Theory Society Newsletter.57:42–46.Retrieved6 February2018.
  20. ^abStraw, Will (2009). "The Music CD and Its Ends".Design and Culture.1(1): 79–91.doi:10.2752/175470709787375751.S2CID191574354.
  21. ^Rasen, Edward (May 1985)."Compact Discs: Sound of the Future".Spin.Archivedfrom the original on 16 December 2015.Retrieved9 January2016.
  22. ^Billboard (March 1992). "CD Unit Sales Pass Cassettes, Majors Say".Billboard.
  23. ^Kozinn, Allan (December 1988). "Have Compact Disks Become Too Much of a Good Thing?".The New York Times.
  24. ^Introducing the amazing Compact Disc (1982).Australian Broadcasting Corporation. 10 June 2015.Archivedfrom the original on 23 November 2015.Retrieved9 January2016– via YouTube.
  25. ^Kornelis, Chris (27 January 2015)."Why CDs may actually sound better than vinyl]".Archived fromthe originalon 9 April 2016.
  26. ^abPeek, Hans B. (January 2010). "The Emergence of the Compact Disc".IEEE Communications Magazine.48(1): 10–17.doi:10.1109/MCOM.2010.5394021.ISSN0163-6804.S2CID21402165.
  27. ^McClure, Steve (8 January 2000)."Heitaro Nakajima".Billboard.p. 68.Archivedfrom the original on 19 March 2015.Retrieved4 November2014.
  28. ^ab"A Long Play Digital Audio Disc System".Audio Engineering Society.March 1979.Archivedfrom the original on 25 July 2009.Retrieved14 February2009.
  29. ^ab"How the CD Was Developed".BBC News.17 August 2007. Archived fromthe originalon 22 December 2007.Retrieved17 August2007.
  30. ^"Philips Compact Disc".Philips. Archived fromthe originalon 19 March 2009.Retrieved14 February2009.
  31. ^"Sony chairman credited with developing CDs dies",Fox News,24 April 2011,archivedfrom the original on 21 May 2013,retrieved14 October2012
  32. ^Knopper, Steve (7 January 2009).Appetite for Self-Destruction: The Rise and Fall of the Record Industry in the Digital Age.Free Press.
  33. ^"The Inventor of the CD".Philips Research.Archived fromthe originalon 29 January 2008.Retrieved16 January2009.
  34. ^Kelly, Heather (29 September 2012)."Rock on! The compact disc turns 30".CNN.Archivedfrom the original on 28 August 2018.Retrieved30 September2012.The first test CD was Richard Strauss'sEine Alpensinfonie,and the first CD actually pressed at a factory was ABBA'sThe Visitors,but that disc wasn't released commercially until later.
  35. ^"Weltpräsentation des" Compact Disc Digital Audio System "(Audio-CD)".Salzburg. Geschichte. Kultur.(in German). Salzburg: Archiv der Erzdiözese Salzburg.Archivedfrom the original on 27 August 2023.Retrieved11 January2023.
  36. ^Bilyeu, Melinda; Hector Cook; Andrew Môn Hughes (2004).The Bee Gees:tales of the brothers Gibb.Omnibus Press. p. 519.ISBN978-1-84449-057-8.
  37. ^1985 News Story on Debut of the Compact Disc (CD).acmestreamingDOTcom. 20 July 2010.Archivedfrom the original on 25 June 2022.Retrieved25 June2022– via YouTube.
  38. ^"Sony History: A Great Invention 100 Years On".Sony.Archived fromthe originalon 2 August 2008.Retrieved28 February2012.
  39. ^Giles, Jeff (1 October 2012)."How Billy Joel's '52nd Street' Became the First Compact Disc released".Ultimate Classic Rock.Townsquare Media,LLC.Archivedfrom the original on 6 July 2017.Retrieved13 October2017.
  40. ^"Philips celebrates 25th anniversary of the Compact Disc"Archived17 August 2015 atArchive-It,Philips Media Release, 16 August 2007. Retrieved 6 October 2013.
  41. ^Kaptainis, Arthur (5 March 1983). "Sampling the latest sound: should last a lifetime".The Globe and Mail.Toronto. p. E11.
  42. ^Maxim,2004
  43. ^The New Schwann Record & Tape Guide Volume 37 No. 2 February 1985
  44. ^JON PARELES (25 February 1987)."NOW ON CD'S, FIRST 4 BEATLES ALBUMS".The New York Times.Archivedfrom the original on 10 March 2017.Retrieved6 February2017.
  45. ^Canale, Larry (1986).Digital Audio's Guide to Compact Discs.Bantam Books. p. 4.ISBN978-0-553-34356-4.
  46. ^Harlow, Oliva."When Did the CD Replace the Cassette Tape?".artifact.Archivedfrom the original on 13 October 2019.Retrieved13 October2019.
  47. ^MAC Audio News. No. 178, November 1989. pp 19–21 Glenn Baddeley.November 1989 News Update.Melbourne Audio Club Inc.
  48. ^abcdvan Willenswaard, Peter (1 May 1989)."PDM, PWM, Delta-Sigma, 1-Bit DACs".stereophile.com.Archivedfrom the original on 4 February 2021.Retrieved30 January2021.
  49. ^Atkinson, John (1989)."PDM, PWM, Delta-Sigma, 1-Bit DACs by John Atkinson".stereophile.com.Archivedfrom the original on 4 February 2021.Retrieved30 January2021.
  50. ^K. Schouhamer Immink and J. Braat (1984)."Experiments Toward an Erasable Compact Disc".J. Audio Eng. Soc.32:531–538.Retrieved2 February2018.
  51. ^abRichter, Felix."The Rise and Fall of the Compact Disc".Statista.Archivedfrom the original on 13 October 2019.Retrieved13 October2019.
  52. ^Williams, Stephen (4 February 2011)."For Car Cassette Decks, Play Time Is Over".New York Times.Archivedfrom the original on 10 November 2012.Retrieved18 July2012.
  53. ^"Journal of the AES » 2007 September - Volume 55 Number 9".www.aes.org.Retrieved3 May2024.
  54. ^"Blu-ray is to DVD as SACD was to CD: Better, but not enough better?".CNET.Retrieved3 May2024.
  55. ^Smith, Ethan (2 January 2009)."Music Sales Decline for Seventh Time in Eight Years: Digital Downloads Can't Offset 20% Plunge in CD Sales".Wall Street Journal.Archivedfrom the original on 20 October 2017.Retrieved4 March2009.
  56. ^"Buying CDs continues to be a tradition in Japan – Tokyo Times".23 August 2013.Archivedfrom the original on 20 December 2016.Retrieved30 December2016.
  57. ^Friedlander, Joshua P. (2015)."News and Notes on 2015 Mid-Year RIAA Shipment and Revenue Statistics"(PDF).Recording Industry Association of America. Archived fromthe original(PDF)on 30 September 2015.
  58. ^Sisaro, Ben.New York Times11 June 2015:Sisario, Ben (11 June 2015)."Music Streaming Service Aims at Japan, Where CD Is Still King".The New York Times.Archivedfrom the original on 20 October 2017.Retrieved26 August2017.
  59. ^"Is this the end of owning music?",BBC News,3 January 2019,archivedfrom the original on 8 November 2020,retrieved3 March2021
  60. ^Ong, Thuy (6 February 2018)."Best Buy will stop selling CDs as digital music revenue continues to grow".The Verge.Archivedfrom the original on 6 February 2018.Retrieved6 February2018.
  61. ^Owsinski, Bobby (7 July 2018)."Best Buy, Winding Down CD Sales, Pounds Another Nail Into The Format's Coffin".Forbes.Archivedfrom the original on 6 August 2018.Retrieved6 August2018.
  62. ^Chris Morris (2 July 2018)."End of a Era: Best Buy Significantly Cuts Back on CDs".Fortune.Archivedfrom the original on 14 July 2018.Retrieved6 August2018.
  63. ^Biersdorfer, J.D. (17 March 2017)."Hand Me the AUX Cord".The New York Times.Archivedfrom the original on 12 January 2022.Retrieved12 January2022.
  64. ^abRamey, Jay (9 February 2021)."Do You Want a CD Player in a New Car?".Autoweek.Archivedfrom the original on 27 August 2023.Retrieved12 January2022.
  65. ^"Physical Formats Still Dominate Japanese Music Market".nippon.com.24 June 2020.Archivedfrom the original on 28 October 2022.Retrieved14 November2022.
  66. ^"Let's Get Physical! Vinyl Sales up >51%, CD Sales up for First Time in 17-yrs".Strata-gee.com.26 January 2022.Archivedfrom the original on 14 November 2022.Retrieved14 November2022.
  67. ^Kariuki, Patrick (18 March 2022)."CD Sales Are Rising Again, but Why?".Makeuseof.com.Archivedfrom the original on 27 August 2023.Retrieved14 November2022.
  68. ^"Vinyl and cassette UK sales continue to surge to 30 year high".Officialcharts.com.Archivedfrom the original on 27 August 2023.Retrieved14 November2022.
  69. ^https://www.riaa.com/wp-content/uploads/2024/03/2023-Year-End-Revenue-Statistics.pdf[bare URL PDF]
  70. ^"Physical album shipments in the U.S. 2022".Statista.Retrieved3 May2024.
  71. ^Bazoge, Mickaël (27 March 2024)."En France comme aux États-Unis, les vinyles en position de force face aux CD".01net.com(in French).Retrieved3 May2024.
  72. ^"Technical Grammy Award".Archivedfrom the original on 26 October 2014.Retrieved5 November2014.
  73. ^"IEEE CD Milestone".IEEE Global History Network.Archivedfrom the original on 26 November 2009.Retrieved14 October2010.
  74. ^"How the CD was developed".BBC News.17 August 2007.Archivedfrom the original on 7 January 2012.Retrieved17 August2007.
  75. ^"Philips Compact Disc".Philips Historical Products.Archived fromthe originalon 25 April 2016.Retrieved24 January2016.
  76. ^"IEC 60908:1987 Compact disc digital audio system".Webstore.iec.ch.Archivedfrom the original on 4 September 2015.Retrieved6 May2015.
  77. ^"IEC 60908:1999 Audio recording – Compact disc digital audio system"(PDF).Webstore.iec.ch.Archived(PDF)from the original on 16 October 2015.Retrieved6 May2015.
  78. ^"CD Logos".Edocpublish.com.4 February 2013.Archivedfrom the original on 8 July 2018.Retrieved21 January2023.
  79. ^"Specs for Freeware Developers".Archived fromthe originalon 1 May 2012.
  80. ^"CD Products".Lscdweb.com.Archivedfrom the original on 21 April 2019.Retrieved24 May2013.
  81. ^stason.org, Stas Bekman: stas (at)."2-35] Why 44.1KHz? Why not 48KHz?".stason.org.Archivedfrom the original on 21 January 2023.Retrieved21 January2023.
  82. ^Watkinson, John (1989).The art of digital audio(Revised Reprint ed.). Oxford: Focal Press.ISBN978-0-08-049936-9.OCLC171287847.
  83. ^John W. Leis (2011).Digital Signal Processing Using MATLAB for Students and Researchers.John Wiley & Sons. p. 82.ISBN978-1-118-03380-7.Archivedfrom the original on 27 August 2023.Retrieved14 September2022.TheNyquist rateis twice the bandwidth of the signal... TheNyquist frequencyorfolding frequencyis half the sampling rate and corresponds to the highest frequency which a sampled data system can reproduce without error.
  84. ^"FFmpeg Filters Documentation".FFmpeg.FFmpeg project.Archivedfrom the original on 28 March 2017.Retrieved6 January2024.
  85. ^Baert, Luc; Theunissen, Luc; Vergult, Guido (22 October 2013).Digital Audio and Compact Disc Technology.Newnes.ISBN978-1-4831-4039-1.Archivedfrom the original on 27 August 2023.Retrieved27 August2023.
  86. ^"Red Book" Audio CD specification, June 1980, Sony/Philips
  87. ^"Red Book" Audio CD specification, September 1983, Sony/Philips
  88. ^"Red Book" Audio CD specification, November 1991, Sony/Philips
  89. ^IEC 60908:1987 Compact disc digital audio system,archivedfrom the original on 4 September 2015,retrieved6 May2015
  90. ^IEC 60908:1999 Audio recording – Compact disc digital audio system(PDF),archived(PDF)from the original on 16 October 2015,retrieved6 May2015
  91. ^Philips."Beethoven's Ninth Symphony of Greater Importance than Technology".Archived fromthe originalon 2 February 2009.Retrieved9 February2007.
  92. ^AES."AES Oral History Project: Kees A.Schouhamer Immink".Archivedfrom the original on 15 May 2009.Retrieved29 July2008.
  93. ^K. A. Schouhamer Immink(2018)."How we made the compact disc".Nature Electronics.1.Retrieved7 September2024.An international collaboration between Philips and the Sony Corporation lead to the creation of the compact disc. The author explains how it came about
  94. ^abCassidy, Fergus (23 October 2005)."Great Lengths".Sunday Tribune.Archived fromthe original(reprint)on 12 October 2007.Retrieved7 January2017.
  95. ^Hoffmann, Frank; Ferstler, Howard (2005).Encyclopedia of Recorded Sound.CRC Press.p. 1289.ISBN978-0-415-93835-8.
  96. ^Goldmark, Peter.Maverick inventor; My Turbulent Years at CBS.New York: Saturday Review Press, 1973.
  97. ^Andy McFadden (9 January 2010)."CD-Recordable FAQ".Archivedfrom the original on 18 November 2013.Retrieved30 December2010.
  98. ^"Richard Strauss: Eine Alpensinfonie - Berlin P..."AllMusic.Retrieved25 September2024.
  99. ^"Mission of Burma 1988 Rykodisc compilation information".Discogs.Archivedfrom the original on 17 October 2010.Retrieved18 January2011.This Rykodisc release was the first compact disc to contain 80 minutes of music; 78 minutes had previously been the longest length possible to encode on a CD.
  100. ^ab"Ambisonic Info | Mirabilis Recordings".Archivedfrom the original on 27 August 2023.Retrieved3 October2021.
  101. ^"Nội hải hòa tử / nội hải hòa tử ベスト".tower.jp.Archivedfrom the original on 27 August 2023.Retrieved25 September2022.
  102. ^"BRUCKNER: Symphony No. 5 in B flat major (original version) — Munich Philharmonic/Christian Thielemann — DGG – Audiophile Audition".Audiophile Audition. 13 July 2005. Archived fromthe originalon 16 May 2013.
  103. ^"Taneyev – Vadim Repin, Ilya Gringolts, Nobuko Imai, Lynn Harrell, Mikhail Pletnev – Chamber Music: Piano Quintet = Klavierquintett • Piano Trio = Klaviertrio".Discogs.com.1 July 2005.Archivedfrom the original on 27 August 2023.Retrieved2 June2023.
  104. ^"Die Ärzte – Bäst Of".Discogs.Archivedfrom the original on 21 February 2021.Retrieved31 January2021.
  105. ^"Valentina Lisitsa – Études – Amazon.com Music".Amazon.com.Archivedfrom the original on 1 January 2017.Retrieved1 January2017.
  106. ^"Alphaville Curated By Blank & Jones – So80s (Soeighties) Presents Alphaville".Discogs.Archivedfrom the original on 29 October 2019.Retrieved21 October2019.
  107. ^McElhearn, Kirk (12 May 2017)."CDs Longer than 80 Minutes Are Becoming More Common".Kirkville.Archivedfrom the original on 17 May 2017.Retrieved12 May2017.
  108. ^Alex."Fehlerprotoll / Error Check CD".Just Add Grooves(in German).Archivedfrom the original on 9 August 2020.Retrieved9 August2020.
  109. ^Wiethoff, André (15 April 2011)."Exact Audio Copy: Audiodaten von optischen Speichermedien extrahieren"(PDF).Hochschule Rhein-Main(in German). pp. 51–53.Archived(PDF)from the original on 9 October 2022.Retrieved9 August2020.
  110. ^"CD".cs.stanford.edu.Stanford.edu.Archivedfrom the original on 9 August 2020.Retrieved9 August2020.An added feature of audio CD's is that in the event of damage, the missing data can be interpolated; that is to say, the information follows a predictable pattern that allows the missing value to be guessed at. So if an audio CD is damaged by dirt or a scratch, the missing data can be averaged from a pattern with no noticeable difference to the listener. This is something the next technology in optical digital memory, CD-ROM, cannot do because an executable program's data doesn't follow a natural law. An interpolation-based guess isn't just slightly different; it's completely wrong. Because of this precision, CD-ROM drives for PC's came later and much more expensive than audio.
  111. ^Taylor, Jim."DVD FAQ".DVD Demystified.Archived fromthe originalon 22 August 2009.Retrieved21 August2012.
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