View source for Company:Compact Disc Digital Audio

{{short description|Data format used for audio compact discs}}
{{Infobox storage medium
| name          = Compact Disc Digital Audio
| logo          = [[File:CDDAlogo.svg|frameless]]
| image         = Audio Compact Disc.png
| caption       = 
| type          = [[Engineering:Optical disc|Optical disc]]
| encoding      = 2 channels of LPCM audio, each [[Signedness|signed]] 16-[[Bit|bit]] values sampled at 44100&nbsp;[[Hertz|Hz]]
| capacity      = up to 74–80 minutes (up to 24 minutes for mini 8&nbsp;cm CD)
| read          = Semiconductor laser (780&nbsp;nm wavelength)
| write         = 
| standard      = IEC 60908
| owner         = [[Company:Sony|Sony]] & [[Company:Philips|Philips]]
| use           = Audio storage
| released      = 1982
| extended from = 
| extended to   = DVD-Audio
}}
{{optical disc authoring}}

'''Compact Disc Digital Audio''' ('''CDDA''' or '''CD-DA'''), also known as '''Digital Audio Compact Disc''' or simply as '''Audio CD''', is the standard format for audio [[Engineering:Compact disc|compact disc]]s. The standard is defined in the '''''Red Book''''', one of a series of Rainbow Books (named for their binding colors) that contain the technical specifications for all CD [[Content format|formats]].

The first commercially available audio [[CD player]], the Sony 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 those two years, to play 22.5 million discs.<ref>{{cite book |first=Ken C. |last=Pohlmann |date=2000 |title=Principles of Digital Audio |page=244 |publisher=McGraw-Hill |isbn=978-0-07-134819-5}}</ref>

Beginning in the 2000s, CDs were increasingly being replaced by other forms of digital storage and distribution, with the result that by 2010 the number of audio CDs being sold in the U.S. had dropped about 50% from their peak; however, they remained one of the primary distribution methods for the [[Finance:Music industry|music industry]].<ref name="AutoMR-2">{{cite news | url=https://www.nytimes.com/2010/05/31/business/media/31bestbuy.html | work=The New York Times | title=As CD Sales Wane, Music Retailers Diversify | first=Joseph | last=Plambeck | date=30 May 2010 | url-status=live | archive-url=https://web.archive.org/web/20170501175846/http://www.nytimes.com/2010/05/31/business/media/31bestbuy.html | archive-date=1 May 2017 }}</ref> In the 2010s, revenues from digital music services, such as [[Software:ITunes|iTunes]], [[Software:Spotify|Spotify]], and YouTube, matched those from physical format sales for the first time.<ref>{{cite news|title=IFPI publishes Digital Music Report 2015|url=http://www.ifpi.org/news/Global-digital-music-revenues-match-physical-format-sales-for-first-time|access-date=1 July 2016|date=14 April 2015|url-status=live|archive-url=https://web.archive.org/web/20150414194629/http://www.ifpi.org/news/Global-digital-music-revenues-match-physical-format-sales-for-first-time|archive-date=14 April 2015}}</ref> According to the RIAA's midyear report in 2020, phonograph record revenues surpassed those of CDs for the first time since the 1980s.<ref>{{cite news|title=Vinyl Outsells CDs For the First Time in Decades|url=https://pitchfork.com/news/vinyl-outsells-cds-for-the-first-time-in-decades/amp/|access-date=22 September 2020|date=10 September 2020|url-status=live|archive-url=https://archive.today/20200922170131/https://pitchfork.com/news/vinyl-outsells-cds-for-the-first-time-in-decades/amp/|archive-date=22 September 2020}}</ref><ref>{{cite web|url=https://www.riaa.com/wp-content/uploads/2020/09/Mid-Year-2020-RIAA-Revenue-Statistics.pdf|title=Mid-Year 2020 RIAA Revenue Statistics|website=Riaa.com|access-date=2 June 2023|archive-date=9 May 2023|archive-url=https://web.archive.org/web/20230509100235/https://www.riaa.com/wp-content/uploads/2020/09/Mid-Year-2020-RIAA-Revenue-Statistics.pdf|url-status=live}}</ref>

== History ==
The [[Engineering:Optophone|optophone]], first presented in 1931, was an early device that used light for both recording and playback of sound signals on a [[Engineering:Negative (photography)|transparent photograph]].<ref>{{Cite web|url=https://www.radiomuseum.org/forumdata/users/5100/Funkschau_4Jg_0131_1v1_v20.pdf|title=Das Photo als Schalplatte|language=de|access-date=2 July 2020|archive-url=https://web.archive.org/web/20160404173739/http://www.radiomuseum.org/forumdata/users/5100/Funkschau_4Jg_0131_1v1_v20.pdf|archive-date=4 April 2016|url-status=live}}</ref> More than thirty years later, American inventor James T. Russell has 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.<ref>{{cite patent |country=US |number=3,501,586 |title=Analog to digital to optical photographic recording and playback system |pubdate=1970-03-17 |fdate=1966-09-01}}</ref> Following litigation, [[Company:Sony|Sony]] and Philips licensed Russell's patents for recording in 1988.<ref>{{cite press release |date=2000 |publisher=Reed College public affairs office |title=Inventor and physicist James Russell '53 will receive Vollum Award at Reed's convocation |access-date=24 July 2014 |url=http://reed.edu/news_center/press_releases/2000-2001/288.html |archive-url=https://web.archive.org/web/20131009170700/http://www.reed.edu/news_center/press_releases/2000-2001/288.html |archive-date=9 October 2013  }}</ref><ref>{{cite web|url=http://web.mit.edu/invent/iow/russell.html |title=Inventor of the Week – James T. Russell – The Compact Disc |date=December 1999 |publisher=MIT |archive-url=https://web.archive.org/web/20030417162935/http://web.mit.edu/invent/iow/russell.html |archive-date=17 April 2003 }}</ref> It is debatable whether Russell's concepts, patents, and prototypes instigated and in some measure influenced the compact disc's design.<ref>{{cite news |newspaper=The Seattle Times |url=http://seattletimes.com/html/businesstechnology/2002103322_cdman29.html |author=Brier Dudley |title=Scientist's invention was let go for a song |date=29 November 2004 |access-date=24 July 2014 |archive-url=https://web.archive.org/web/20140810225444/http://seattletimes.com/html/businesstechnology/2002103322_cdman29.html |archive-date=10 August 2014}}</ref>

The compact disc is an evolution of [[LaserDisc]] technology,{{r|Immink}} where a focused [[Physics:Laser|laser]] beam is used that enables the high information density required for high-quality digital audio signals. Unlike the prior art by Optophonie and James Russell, the information on the disc is read from a reflective layer using a laser as a light source through a protective substrate. Prototypes were developed by [[Company:Philips|Philips]] and Sony independently in the late 1970s.<ref>{{cite web|title=The History of the CD|url=https://www.philips.com/a-w/research/technologies/cd/beginning.html|publisher=Philips Research|access-date=7 June 2014}}{{dead link|fix-attempted=yes|date=March 2023}}</ref> Although originally dismissed by Philips Research management as a trivial pursuit,<ref name="Immink2" /> the CD became the primary focus for Philips as the [[LaserDisc]] format struggled.<ref name="AndItsEnd">{{Cite journal|last=Straw|first=Will|date=2009|title=The Music CD and Its Ends|journal=Design and Culture|volume=1|issue=1|pages=79–91|doi=10.2752/175470709787375751|s2cid=191574354}}</ref> In 1979, Sony and Philips set up a joint task force of engineers to design a new digital audio disc. After a year of experimentation and discussion, the ''Red Book'' CD-DA standard was published in 1980. After their commercial release in 1982, compact discs and their players were extremely popular. Despite costing up to $1,000, over 400,000 CD players were sold in the United States between 1983 and 1984.<ref>{{cite web|url=http://www.spin.com/1985/05/compact-discs-sound-of-the-future/|title=Compact Discs: Sound of the Future|first=Edward|last=Rasen|work=Spin|date=May 1985|access-date=9 January 2016|url-status=live|archive-url=https://web.archive.org/web/20151216064105/http://www.spin.com/1985/05/compact-discs-sound-of-the-future/|archive-date=16 December 2015}}</ref> 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.<ref>{{Cite magazine|title=CD Unit Sales Pass Cassettes, Majors Say|last=Billboard|date=March 1992|magazine=Billboard}}</ref><ref>{{Cite news|title=Have Compact Disks Become Too Much of a Good Thing?|last=Kozinn|first=Allan|date=December 1988|work=The New York Times}}</ref> 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.<ref>{{Cite AV media|url=https://www.youtube.com/watch?v=_Tx6TYnPat8|title=Introducing the amazing Compact Disc (1982)|date=10 June 2015|publisher=Australian Broadcasting Corporation|access-date=9 January 2016|via=YouTube|url-status=live|archive-url=https://web.archive.org/web/20151123170700/https://www.youtube.com/watch?v=_Tx6TYnPat8|archive-date=23 November 2015}}</ref>

=== Digital audio laser-disc prototypes ===
In 1974, Lou Ottens, director of the audio division of Philips, started a small group to develop an analog optical audio disc with a diameter of {{cvt|20|cm}} and a sound quality superior to that of the vinyl record.<ref>{{cite news |url=http://www.laweekly.com/music/why-cds-may-actually-sound-better-than-vinyl-5352162 |title=Why CDs may actually sound better than vinyl] |archive-url=https://web.archive.org/web/20160409132701/http://www.laweekly.com/music/why-CDs-may-actually-sound-better-than-vinyl-5352162 |archive-date=9 April 2016 |first=Chris |last=Kornelis |date=27 January 2015}}</ref> 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 {{cvt|11.5|cm}}, the diagonal of an audio cassette.{{r|Immink}}{{r|peek}}

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 digital [[PCM adaptor]] that made audio recordings using a [[Betamax]] video recorder. After this, in 1974 the leap to storing digital audio on an optical disc was easily made.<ref>{{cite magazine | url=https://books.google.com/books?id=kw0EAAAAMBAJ&pg=PA68 | title=Heitaro Nakajima | magazine=Billboard | date=8 January 2000 | access-date=4 November 2014 | author=McClure, Steve | pages=68 | url-status=live | archive-url=https://web.archive.org/web/20150319065246/http://books.google.com/books?id=kw0EAAAAMBAJ&pg=PA68 | archive-date=19 March 2015 }}</ref> Sony first publicly demonstrated an optical digital audio disc in September 1976. A year later, in September 1977, Sony showed the press a {{cvt|30|cm}} disc that could play an hour of digital audio (44,100&nbsp;Hz sampling rate and 16-bit resolution) using [[Modified frequency modulation|modified frequency modulation]] encoding.<ref name="SonyHistorical">{{cite journal |url=http://www.aes.org/e-lib/browse.cfm?elib=2912 |url-access=subscription |title = A Long Play Digital Audio Disc System | date = March 1979 |website=Audio Engineering Society | access-date = 14 February 2009 | url-status = live | archive-url = https://web.archive.org/web/20090725223113/http://www.aes.org/e-lib/browse.cfm?elib=2912 | archive-date = 25 July 2009 }}</ref> In September 1978, the company demonstrated an optical digital audio disc with a 150-minute playing time, 44,056&nbsp;Hz sampling rate, 16-bit linear resolution, and cross-interleaved error correction code—specifications similar to those later settled upon for the standard compact disc format in 1980. Technical details of Sony's digital audio disc were presented during the 62nd [[Organization:Audio Engineering Society|AES]] Convention, held on 13–16 March 1979, in Brussels.{{r|SonyHistorical}} 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"{{r|BBC6950933}} in Eindhoven, Netherlands.<ref name="PhilipsHistorical">{{cite web | url = http://www.philipsmuseumeindhoven.nl/phe/products/e_cd.htm | title = Philips Compact Disc | publisher = Philips | access-date = 14 February 2009 | archive-url = https://web.archive.org/web/20090319141821/http://www.philipsmuseumeindhoven.nl/phe/products/e_cd.htm | archive-date = 19 March 2009 }}</ref> Sony executive Norio Ohga, later CEO and chairman of Sony, and Heitaro Nakajima were convinced of the format's commercial potential and pushed further development despite widespread skepticism.<ref name="Ohgaobituary">{{ citation | url = http://www.foxnews.com/world/2011/04/24/sony-chairman-credited-developing-cds-dies/ | title = Sony chairman credited with developing CDs dies | access-date = 14 October 2012 | work = Fox News | date = 24 April 2011 | url-status = live | archive-url = https://web.archive.org/web/20130521044524/http://www.foxnews.com/world/2011/04/24/sony-chairman-credited-developing-cds-dies/ | archive-date = 21 May 2013 }}</ref>

=== Collaboration and standardization ===
[[File:schouhamerimmink.jpg|thumb|upright|Dutch inventor and Philips chief engineer Kees Schouhamer Immink was 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 engineers Kees Schouhamer Immink and Toshitada Doi, the research pushed forward [[Physics:Laser|laser]] and [[Engineering:Optical disc|optical disc]] technology.<ref name="BBC6950933">{{cite news | url = http://news.bbc.co.uk/2/hi/technology/6950933.stm | title = How the CD Was Developed | work = BBC News | date = 17 August 2007 | access-date = 17 August 2007 | archive-url = https://web.archive.org/web/20071222035025/http://news.bbc.co.uk/2/hi/technology/6950933.stm | archive-date = 22 December 2007 }}</ref> After a year of experimentation and discussion, the task force produced the ''Red Book'' CD-DA standard. First published in 1980, the standard was formally adopted by the [[Organization:International Electrotechnical Commission|IEC]] as an international standard in 1987, with various amendments becoming part of the standard in 1996.{{citation needed|date=December 2021}}

Philips coined the term ''compact disc'' in line with another audio product, the [[Engineering:Compact Cassette|Compact Cassette]],<ref name="peek">{{cite journal |first=Hans B. |last=Peek |title=The Emergence of the Compact Disc |journal=IEEE Communications Magazine |date=January 2010 |pages=10–17 |volume=48 |number=1 |issn=0163-6804 |doi=10.1109/MCOM.2010.5394021 |s2cid=21402165  }}</ref> and contributed the general manufacturing process, based on video LaserDisc technology. Philips also contributed [[Engineering:Eight-to-fourteen modulation|eight-to-fourteen modulation]] (EFM), while Sony contributed the error-correction method, CIRC, which offers resilience to defects such as scratches and fingerprints.

''The Compact Disc Story'',<ref name="Immink" /> 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,<ref name="Immink2" /><ref name="Knopper">{{cite book | title = Appetite for Self-Destruction: The Rise and Fall of the Record Industry in the Digital Age | author = Knopper, Steve | publisher = Free Press | date = 7 January 2009 | access-date = <!-- 2009-038-17 --> }}</ref> though according to Philips, the compact disc was "invented collectively by a large group of people working as a team."<ref name="PhilDoss">{{cite web | url = http://www.research.philips.com/newscenter/dossier/optrec/beethoven.html | title = The Inventor of the CD | work = Philips Research | access-date = 16 January 2009 | archive-url = https://archive.today/20080129201342/http://www.research.philips.com/newscenter/dossier/optrec/beethoven.html | archive-date = 29 January 2008 }}</ref>

=== Initial launch and adoption ===
Early milestones in the launch and adoption of the format included:
* The first ''test pressing'' was of a recording of Richard Strauss's ''An Alpine Symphony'', recorded December 1–3, 1980 and played by the Berlin Philharmonic and conducted by Herbert von Karajan, who had been enlisted as an ambassador for the format in 1979.<ref name="Karajan">{{cite web | url= http://www.cnn.com/2012/09/28/tech/innovation/compact-disc-turns-30 | title= Rock on! The compact disc turns 30 | date= 29 September 2012 | first= Heather | last= Kelly | publisher= CNN | access-date= 30 September 2012 | quote= The first test CD was Richard Strauss's ''Eine Alpensinfonie'', and the first CD actually pressed at a factory was ABBA's ''The Visitors'', but that disc wasn't released commercially until later. | archive-url= https://web.archive.org/web/20180828171847/https://www.cnn.com/2012/09/28/tech/innovation/compact-disc-turns-30/ | archive-date= 28 August 2018 | url-status= live }}</ref>
* The world presentation took place during the Salzburg Easter Festival on 15 April 1981, at a press conference of Akio Morita and Norio Ohga (Sony), Joop van Tilburg (Philips), and Richard Busch (PolyGram), in the presence of Karajan who praised the new format.<ref>{{cite web|title=Weltpräsentation des "Compact Disc Digital Audio System" (Audio-CD)|url=http://salzburg-geschichte-kultur.at/weltpraesentation-des-compact-disc-digital-audio-system-audio-cd/|access-date=11 January 2023|website=Salzburg. Geschichte. Kultur.|publisher=Archiv der Erzdiözese Salzburg|location=Salzburg|language=de|archive-date=27 August 2023|archive-url=https://web.archive.org/web/20230827104049/http://salzburg-geschichte-kultur.at/weltpraesentation-des-compact-disc-digital-audio-system-audio-cd/|url-status=live}}</ref>
* The first ''public demonstration'' was on the BBC television programme ''Tomorrow's World'' in 1981, when the Bee Gees' album ''Living Eyes'' (1981) was played.<ref name="AutoMR-4">{{cite book| last = Bilyeu|first = Melinda|author2=Hector Cook |author3=Andrew Môn Hughes |publisher = Omnibus Press|year = 2004| isbn = 978-1-84449-057-8| title = The Bee Gees:tales of the brothers Gibb| page = 519 }}</ref>
* The first ''commercial'' compact disc was produced on 17 August 1982, a 1979 recording of Chopin waltzes performed by Claudio Arrau.<ref>{{Cite AV media |date=20 July 2010 |title=1985 News Story on Debut of the Compact Disc (CD) |url=https://www.youtube.com/watch?v=vwrU8s-M-gc |access-date=25 June 2022 |publisher=acmestreamingDOTcom |via=YouTube |language=en-US}}</ref>
* The first 50 titles were ''released'' in Japan on 1 October 1982,<ref name="AutoMR-6">{{cite web|url=http://www.sony.net/Fun/SH/1-20/h5.html|archive-url=https://web.archive.org/web/20080802133849/http://www.sony.net/Fun/SH/1-20/h5.html|archive-date=2 August 2008|title=Sony History: A Great Invention 100 Years On|publisher=[[Company:Sony|Sony]]|access-date=28 February 2012 }}</ref> the first of which was a re-release of the Billy Joel album ''52nd Street''.<ref>{{cite web|url=http://ultimateclassicrock.com/the-first-compact-disc-released/|title=How Billy Joel's '52nd Street' Became the First Compact Disc released|first=Jeff|last=Giles|work=Ultimate Classic Rock|publisher=[[Company:Townsquare Media|Townsquare Media]], LLC|date=1 October 2012|access-date=13 October 2017|url-status=live|archive-url=https://web.archive.org/web/20170706021629/http://ultimateclassicrock.com/the-first-compact-disc-released/|archive-date=6 July 2017}}</ref>
* The first CD played on BBC Radio was in October 1982 on BBC Radio Scotland (Jimmy Mack programme, Followed by Ken Bruce and Eddie Mair all BBC Scotland), with the first CD ''played'' on UK independent radio station shortly after (Radio Forth, Jay Crawford Show). The CD was the Dire Straits album ''Love Over Gold''.<ref>{{Cite web|url=https://www.hificorner.co.uk/|archive-url=https://web.archive.org/web/20171004211808/http://www.hificorner.co.uk/|url-status=dead|title=Home page – HiFi Corner|archive-date=4 October 2017|website=Hificorner.co.uk}}</ref>
*The Japanese launch was followed on 14 March 1983 by the introduction of CD players and discs to Europe<ref>[http://www.newscenter.philips.com/main/standard/about/news/press/20070816_25th_anniversary_cd.wpd "Philips celebrates 25th anniversary of the Compact Disc"]{{webarchive|url=https://wayback.archive-it.org/all/20150817154431/http://www.newscenter.philips.com/main/standard/about/news/press/20070816_25th_anniversary_cd.wpd |date=17 August 2015 }}, Philips Media Release, 16 August 2007. Retrieved 6 October 2013.</ref> and North America where CBS Records released sixteen titles.<ref name="G&M 1983-03-05">{{cite news
 | last      = Kaptainis
 | first     = Arthur
 | title     = Sampling the latest sound: should last a lifetime
 | newspaper = The Globe and Mail
 | date      = 5 March 1983
| location  = Toronto
 | page      = E11
}}</ref>

The first artist to sell a million copies on CD was Dire Straits, with their 1985 album ''Brothers in Arms''.<ref name="AutoMR-7">''Maxim'', 2004</ref> One of the first CD markets was devoted to reissuing popular music whose commercial potential was already proven. The first major artist to have their entire catalog converted to CD was David Bowie, whose first fourteen studio albums of (then) sixteen were made available by RCA Records in February 1985, along with four greatest hits albums; his fifteenth and sixteenth albums had already been issued on CD by EMI Records in 1983 and 1984, respectively.<ref name="AutoMR-8">The New Schwann Record & Tape Guide Volume 37 No. 2 February 1985</ref> On 26 February 1987, the first four UK albums by the Beatles were released in mono on compact disc.<ref name="BeatlesCD">{{cite web |url=https://www.nytimes.com/1987/02/25/arts/now-on-cd-s-first-4-beatles-albums.html |title=NOW ON CD'S, FIRST 4 BEATLES ALBUMS |author=JON PARELES |date=25 February 1987 |work={{wipe|The New York Times}} |access-date=6 February 2017 |archive-url=https://web.archive.org/web/20170310202959/http://www.nytimes.com/1987/02/25/arts/now-on-cd-s-first-4-beatles-albums.html |archive-date=10 March 2017 |url-status=live }}</ref>

The growing acceptance of the CD in 1983 marks the beginning of the popular digital audio revolution.<ref>{{cite book |last=Canale |first=Larry |date=1986 |title=Digital Audio's Guide to Compact Discs |page=4 |publisher=Bantam Books |isbn=978-0-553-34356-4}}</ref> It was enthusiastically received, especially in the early-adopting classical music and [[Engineering:Audiophile|audiophile]] communities, and its handling quality received particular praise. As the price of players gradually came down, and with the introduction of the portable Discman, the CD began to gain popularity in the larger popular and rock music markets. With the rise in CD sales, pre-recorded [[Engineering:Cassette tape|cassette tape]] sales began to decline in the late 1980s; CD sales overtook cassette sales in the early 1990s.{{citation needed|date=December 2021}}<ref>{{cite web |last1=Harlow |first1=Oliva |title=When Did the CD Replace the Cassette Tape? |url=https://southtree.com/blogs/artifact/when-did-the-cd-replace-the-cassette-tape |website=artifact |access-date=13 October 2019 |archive-url=https://web.archive.org/web/20191013073112/https://southtree.com/blogs/artifact/when-did-the-cd-replace-the-cassette-tape |archive-date=13 October 2019 |url-status=live }}</ref> In 1988, 400 million CDs were manufactured by 50 pressing plants around the world.<ref name="AutoMR-9">MAC Audio News. No. 178, November 1989. pp 19–21 Glenn Baddeley. ''November 1989 News Update''. Melbourne Audio Club Inc.</ref>

=== Further development ===
[[File:Sony-Discman-D-E307CK.jpg|thumb|Sony Discman D-E307CK portable CD player with 1-bit DAC]]

Early CD players employed binary-weighted [[Digital-to-analog converter|digital-to-analog converter]]s (DAC), which contained individual electrical components for each bit of the DAC.<ref name=stereophile-19890501-Willenswaard>{{cite web|url=https://www.stereophile.com/content/pdm-pwm-delta-sigma-1-bit-dacs|title=PDM, PWM, Delta-Sigma, 1-Bit DACs|last=van Willenswaard|first=Peter|website=stereophile.com|date=1 May 1989|access-date=30 January 2021|archive-date=4 February 2021|archive-url=https://web.archive.org/web/20210204151933/https://www.stereophile.com/content/pdm-pwm-delta-sigma-1-bit-dacs|url-status=live}}</ref> Even when using high-precision components, this approach was prone to decoding errors.{{clarify|date=December 2021}}<ref name=stereophile-19890501-Willenswaard /> Another issue was [[Jitter|jitter]], 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.<ref name=stereophile-19890501-Willenswaard /> This increased the cost of CD players but did not solve the core problem.

A breakthrough in the late 1980s culminated in development of the [[Delta-sigma modulation#Digital-to-analog conversion|1-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 called [[Pulse-density modulation|pulse-density modulation]] (PDM),<ref name=stereophile-198906-Atkinson>{{cite web|url=https://www.stereophile.com/content/pdm-pwm-delta-sigma-1-bit-dacs-john-atkinson|title=PDM, PWM, Delta-Sigma, 1-Bit DACs by John Atkinson|last=Atkinson|first=John|website=stereophile.com|year=1989|access-date=30 January 2021|archive-date=4 February 2021|archive-url=https://web.archive.org/web/20210204164249/https://www.stereophile.com/content/pdm-pwm-delta-sigma-1-bit-dacs-john-atkinson|url-status=live}}</ref> while Matsushita (now [[Company:Panasonic|Panasonic]]) chose [[Pulse-width modulation|pulse-width modulation]] (PWM), advertising it as MASH, which is an acronym derived from their patented Multi-stAge noiSe-sHaping PWM topology.<ref name=stereophile-19890501-Willenswaard />

The CD was primarily planned as the successor to the vinyl record for playing music, rather than as a data storage medium. However, CDs have grown to encompass other applications. In 1983, following the CD's introduction, Immink and Joseph Braat presented the first experiments with erasable compact discs during the 73rd AES Convention.<ref>{{Cite journal
|journal=J. Audio Eng. Soc.|volume=32|date=1984|title=Experiments Toward an Erasable Compact Disc
|author=K. Schouhamer Immink and J. Braat|url=https://www.researchgate.net/publication/237764745
|pages=531–538|access-date=2 February 2018}}</ref> In June 1985, the computer-readable [[CD-ROM]] (read-only memory) and, in 1990, recordable [[Engineering:CD-R|CD-R]] discs were introduced.{{efn|The world's first CD-R was made by the Japanese firm Taiyo Yuden Co., Ltd. in 1988 as part of the joint Philips-Sony development effort.}} Recordable CDs became an alternative to tape for recording and distributing music and could be duplicated without degradation in sound quality.

CD sales in the United States peaked by 2000.<ref name="statista">{{cite web |last1=Richter |first1=Felix |title=The Rise and Fall of the Compact Disc |url=https://www.statista.com/chart/12950/cd-sales-in-the-us/ |website=Statista |access-date=13 October 2019 |archive-url=https://web.archive.org/web/20191013073724/https://www.statista.com/chart/12950/cd-sales-in-the-us/ |archive-date=13 October 2019 |url-status=live }}</ref> By the early 2000s, the CD player had largely replaced the [[Engineering:Compact Cassette|audio cassette]] player as standard equipment in new automobiles, with 2010 being the final model year for any car in the United States to have a factory-equipped cassette player.<ref name=nyt20120718>{{cite news|url=https://www.nytimes.com/2011/02/06/automobiles/06AUDIO.html|title=For Car Cassette Decks, Play Time Is Over|last=Williams|first=Stephen|newspaper=New York Times|date=4 February 2011|access-date=18 July 2012|url-status=live|archive-url=https://web.archive.org/web/20121110105333/https://www.nytimes.com/2011/02/06/automobiles/06AUDIO.html|archive-date=10 November 2012}}</ref>

Other newer video formats such as [[Engineering:DVD|DVD]] and [[Engineering:Blu-ray|Blu-ray]] use the same physical geometry as CD, and most DVD and Blu-ray players are backward compatible with audio CDs.

=== Decline ===
With the advent and popularity of [[Digital distribution|Internet-based distribution]] of files in [[Lossy compression|lossy-compressed]] audio formats such as [[MP3]], sales of CDs began to decline in the 2000s. For example, between 2000 and 2008, despite overall growth in music sales and one anomalous year of increase, major-label CD sales declined overall by 20%.<ref name="AutoMR-11">{{cite news |first=Ethan |last=Smith |title=Music Sales Decline for Seventh Time in Eight Years: Digital Downloads Can't Offset 20% Plunge in CD Sales |url=https://www.wsj.com/articles/SB123075988836646491?mod=rss_whats_news_technology&mg=com-wsj |newspaper=Wall Street Journal |date=2 January 2009 |access-date=4 March 2009 |url-status=live |archive-url=https://web.archive.org/web/20171020191140/https://www.wsj.com/articles/SB123075988836646491?mod=rss_whats_news_technology&mg=com-wsj |archive-date=20 October 2017  }}</ref> In 2012, CDs and DVDs made up only 34% of music sales in the United States.<ref>{{cite web|url=http://www.tokyotimes.com/buying-cds-continues-to-be-a-tradition-in-japan/|title=Buying CDs continues to be a tradition in Japan – Tokyo Times|date=23 August 2013|access-date=30 December 2016|url-status=live|archive-url=https://web.archive.org/web/20161220150903/http://www.tokyotimes.com/buying-cds-continues-to-be-a-tradition-in-japan/|archive-date=20 December 2016}}</ref> By 2015, only 24% of music in the United States was purchased on physical media, two thirds of this consisting of CDs;<ref>{{Cite web|url=http://riaa.com/media/238E8AC7-3810-A95C-44DC-B6DEB46A3C6E.pdf|title=News and Notes on 2015 Mid-Year RIAA Shipment and Revenue Statistics|last=Friedlander|first=Joshua P.|year=2015|publisher=Recording Industry Association of America|archive-url=https://web.archive.org/web/20150930135150/http://riaa.com/media/238E8AC7-3810-A95C-44DC-B6DEB46A3C6E.pdf|archive-date=30 September 2015}}</ref> however, in the same year in Japan, over 80% of music was bought on CDs and other physical formats.<ref>Sisaro, Ben.  ''New York Times'' 11 June 2015:  {{cite news|url=https://www.nytimes.com/2015/06/12/business/media/line-music-a-new-streaming-service-aims-at-japanese-market.html?_r=0|title=Music Streaming Service Aims at Japan, Where CD Is Still King|newspaper=The New York Times|date=11 June 2015|archive-url=https://web.archive.org/web/20171020191923/https://www.nytimes.com/2015/06/12/business/media/line-music-a-new-streaming-service-aims-at-japanese-market.html?_r=0|archive-date=20 October 2017|url-status=live|access-date=26 August 2017|last1=Sisario|first1=Ben}}</ref> In 2018, U.S. CD sales were 52 million units—less than 6% of the peak sales volume in 2000.<ref name="statista" /> In the UK, 32&nbsp;million units were sold, almost 100&nbsp;million fewer than in 2008.<ref>{{citation |title=Is this the end of owning music? |work=BBC News |date=3 January 2019 |url=https://www.bbc.com/news/entertainment-arts-46735093 |access-date=3 March 2021 |archive-date=8 November 2020 |archive-url=https://web.archive.org/web/20201108002704/https://www.bbc.com/news/entertainment-arts-46735093 |url-status=live }}</ref>

During the 2010s, the increasing popularity of solid-state media and music streaming services caused automakers to remove automotive CD players in favor of minijack auxiliary inputs, wired connections to USB devices and wireless [[Bluetooth]] connections.<ref name="Biersdorfer">{{cite news |last1=Biersdorfer |first1=J.D. |title=Hand Me the AUX Cord |url=https://www.nytimes.com/2017/03/17/technology/personaltech/hand-me-the-aux-cord.html |access-date=12 January 2022 |work=The New York Times |date=March 17, 2017 |archive-date=12 January 2022 |archive-url=https://web.archive.org/web/20220112053206/https://www.nytimes.com/2017/03/17/technology/personaltech/hand-me-the-aux-cord.html |url-status=live }}</ref>  Automakers viewed CD players as using up valuable space and taking up weight which could be reallocated to more popular features, like large touchscreens.<ref name="Ramey">{{cite news |last1=Ramey |first1=Jay |title=Do You Want a CD Player in a New Car? |url=https://www.autoweek.com/car-life/classic-cars/a35459280/do-you-want-a-cd-player-in-a-new-car/ |access-date=12 January 2022 |work=Autoweek |date=February 9, 2021 |archive-date=27 August 2023 |archive-url=https://web.archive.org/web/20230827104052/https://www.autoweek.com/car-life/classic-cars/a35459280/do-you-want-a-cd-player-in-a-new-car/ |url-status=live }}</ref>  By 2021, only [[Company:Lexus|Lexus]] and [[Company:General Motors|General Motors]] were still including CD players as standard equipment with certain vehicles.<ref name="Ramey" />

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.<ref name="AndItsEnd" /> In 2018, [[Company:Best Buy|Best Buy]] announced plans to decrease their focus on CD sales, however, while continuing to sell records, sales of which are growing during the [[Engineering:Vinyl revival|vinyl revival]].<ref name="bestverge">{{cite web|url=https://www.theverge.com/2018/2/6/16973538/bestbuy-target-cd-sales-vinyl-cassette|title=Best Buy will stop selling CDs as digital music revenue continues to grow|first=Thuy|last=Ong|date=6 February 2018|access-date=6 February 2018|website=[[The Verge]]|archive-url=https://web.archive.org/web/20180206181746/https://www.theverge.com/2018/2/6/16973538/bestbuy-target-cd-sales-vinyl-cassette|archive-date=6 February 2018|url-status=live}}</ref><ref>{{cite news|url=https://www.forbes.com/sites/bobbyowsinski/2018/07/07/best-buy-cd-sales/amp/|title=Best Buy, Winding Down CD Sales, Pounds Another Nail Into The Format's Coffin|first=Bobby|last=Owsinski|date=7 July 2018|work=Forbes|access-date=6 August 2018|archive-url=https://web.archive.org/web/20180806211709/https://www.forbes.com/sites/bobbyowsinski/2018/07/07/best-buy-cd-sales/amp/|archive-date=6 August 2018|url-status=live}}</ref><ref>{{cite news|url=http://fortune.com/2018/07/02/best-buy-ends-cd-sales/|title=End of a Era: Best Buy Significantly Cuts Back on CDs|author=Chris Morris|date=2 July 2018|work=Fortune|access-date=6 August 2018|archive-url=https://web.archive.org/web/20180714110206/http://fortune.com/2018/07/02/best-buy-ends-cd-sales/|archive-date=14 July 2018|url-status=live}}</ref> CDs continued to be strong in some markets such as Japan where 132 million units were produced in 2019.<ref>{{Cite web|url=https://www.nippon.com/en/japan-data/h00740/|title=Physical Formats Still Dominate Japanese Music Market|date=24 June 2020|website=nippon.com|access-date=14 November 2022|archive-date=28 October 2022|archive-url=https://web.archive.org/web/20221028183640/https://www.nippon.com/en/japan-data/h00740/|url-status=live}}</ref>

The decline in CD sales has slowed in recent years; in 2021, CD sales increased in the US for the first time since 2004,<ref>{{cite web | url=https://www.strata-gee.com/lets-get-physical-vinyl-sales-up-51-cd-sales-up-for-first-time-in-17-yrs/ | title=Let's Get Physical! Vinyl Sales up >51%, CD Sales up for First Time in 17-yrs | website=Strata-gee.com | date=26 January 2022 | access-date=14 November 2022 | archive-date=14 November 2022 | archive-url=https://web.archive.org/web/20221114140242/https://www.strata-gee.com/lets-get-physical-vinyl-sales-up-51-cd-sales-up-for-first-time-in-17-yrs/ | url-status=live }}</ref> with Axios citing its rise to "young people who are finding they like hard copies of music in the digital age".<ref>{{Cite web|url=https://www.makeuseof.com/cd-sales-are-rising-again-but-why/|title=CD Sales Are Rising Again, but Why?|first=Patrick|last=Kariuki|date=18 March 2022|website=Makeuseof.com|access-date=14 November 2022|archive-date=27 August 2023|archive-url=https://web.archive.org/web/20230827104056/https://www.makeuseof.com/cd-sales-are-rising-again-but-why/|url-status=live}}</ref> It came at the same time as both vinyl and cassette reached sales levels not seen in 30 years.<ref>{{Cite web|url=https://www.officialcharts.com/chart-news/vinyl-and-cassette-uk-sales-continue-to-surge-to-30-year-high-as-cd-sales-decline-slows__34839/|title=Vinyl and cassette UK sales continue to surge to 30 year high|website=Officialcharts.com|access-date=14 November 2022|archive-date=27 August 2023|archive-url=https://web.archive.org/web/20230827104058/https://www.officialcharts.com/chart-news/vinyl-and-cassette-uk-sales-continue-to-surge-to-30-year-high-as-cd-sales-decline-slows__34839/|url-status=live}}</ref><!--User:Kvng/RTH-->

=== Awards and accolades ===
Sony and Philips received praise for the development of the compact disc from professional organizations. These awards include
* Technical Grammy Award for Sony and Philips, 1998.<ref name="grammy">{{cite news |url=http://www.grammy.org/recording-academy/producers-and-engineers/awards |title=Technical Grammy Award |access-date=5 November 2014 |url-status=live |archive-url=https://web.archive.org/web/20141026094809/http://www.grammy.org/recording-academy/producers-and-engineers/awards |archive-date=26 October 2014  }}</ref>
* IEEE Milestone award, 2009, for Philips only with the citation: "On 8 March 1979, N.V. Philips' Gloeilampenfabrieken demonstrated for the international press a Compact Disc Audio Player. The demonstration showed that it is possible by using digital optical recording and playback to reproduce audio signals with superb stereo quality. This research at Philips established the technical standard for digital optical recording systems."<ref name="IEEE_CD_Milestone">{{cite web | url = http://www.ieeeghn.org/wiki/index.php/Milestones:Compact_Disc_Audio_Player,_1979 | title = IEEE CD Milestone | publisher = IEEE Global History Network | access-date = 14 October 2010 | url-status = live | archive-url = https://web.archive.org/web/20091126195434/http://www.ieeeghn.org/wiki/index.php/Milestones:Compact_Disc_Audio_Player,_1979 | archive-date = 26 November 2009 }}</ref>

== Standard ==
The ''Red Book'' specifies the physical parameters and properties of the CD, the optical parameters, deviations and error rate, modulation system ([[Engineering:Eight-to-fourteen modulation|eight-to-fourteen modulation]], EFM) and error correction facility ([[Cross-interleaved Reed–Solomon coding|cross-interleaved Reed–Solomon coding]], CIRC), and the eight subcode 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 of [[Digital audio|digital audio]] encoding (2-channel [[Signedness|signed]] 16-[[Bit|bit]] [[Pulse-code modulation|LPCM]] sampled at [[44,100 Hz|44,100 Hz]]).

The first edition of the ''Red Book'' was released in 1980 by Philips and Sony;<ref name="BBC" /><ref name="Auto45-1" /> it was adopted by the Digital Audio Disc Committee and ratified by the [[Organization:International Electrotechnical Commission|International Electrotechnical Commission]] (IEC) Technical Committee 100 as an [[International standard|international standard]] in 1987 with the reference IEC 60908.<ref name="Auto45-2" /> The second edition of IEC 60908 was published in 1999<ref name="Auto45-3" /> 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 the Red Book, such as the details for [[CD-Text]], CD+G and CD+EG.<ref>{{Cite web|url=https://www.edocpublish.com/resources-2/specifications/cd-logos/|title=CD Logos|website=Edocpublish.com|date=4 February 2013|access-date=21 January 2023|archive-date=8 July 2018|archive-url=https://web.archive.org/web/20180708044901/http://www.edocpublish.com/resources-2/specifications/cd-logos/|url-status=live}}</ref><ref>{{Cite web|url=http://www.ccs.neu.edu/home/bchafy/cdb/info/info.html|archive-url=https://web.archive.org/web/20120501075730/http://www.ccs.neu.edu/home/bchafy/cdb/info/info.html|url-status=dead|title=Specs for Freeware Developers|archive-date=1 May 2012}}</ref>

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|date=February 2022}}, which charges {{US$|100}} for the ''Red Book'', plus {{US$|50}} each for the ''Subcode Channels R-W'' and ''CD Text Mode'' annexes.<ref name="philips_red_book">{{cite web |url=https://www.lscdweb.com/ordering/cd_products.html |title=CD Products |website=Lscdweb.com |access-date=24 May 2013 |archive-date=21 April 2019 |archive-url=https://web.archive.org/web/20190421163757/https://www.lscdweb.com/ordering/cd_products.html |url-status=live }}</ref>

== Audio format ==
The audio contained in a CD-DA consists of two-channel [[Signedness|signed]] 16-[[Bit|bit]] [[Pulse-code modulation|LPCM]] sampled at [[44,100 Hz|44,100 Hz]] and written as a [[Endianness|little-endian]] interleaved stream with left channel coming first.

The [[Sampling rate|sampling rate]] is adapted from that attained when recording digital audio on [[Engineering:Videotape|videotape]] with a [[PCM adaptor]], an earlier way of storing digital audio.<ref name="Auto45-4" /><!-- more sources needed --> An audio CD can represent frequencies up to 22.05&nbsp;kHz, the [[Nyquist frequency]] of the 44.1&nbsp;kHz sample rate.<ref name="Leis" />

There was a long debate over the use of 16-bit (Sony) or 14-bit (Philips) [[Quantization (signal processing)|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-bit [[Digital-to-analog converter|D/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 times [[Oversampling|oversampling]].<ref name=Immink />

Some CDs are mastered with [[Engineering:Emphasis (telecommunications)|pre-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 50µs and 15µs (9.49&nbsp;dB boost at 20&nbsp;kHz), and a binary flag in the disc subcode instructs the player to apply de-emphasis filtering if appropriate. Playback of such discs in a computer or [[Engineering:Ripping|ripping]] to [[WAV]] files typically does not take into account the pre-emphasis, so such files play back with a distorted frequency response.{{citation needed|date=January 2022}} [[Software:FFmpeg|FFmpeg]] has a filter to remove (or apply) the pre-emphasis in order to create standard WAV files, or to create CDs with pre-emphasis.<ref>{{cite web |title=FFmpeg Filters Documentation |url=https://ffmpeg.org/ffmpeg-filters.html#aemphasis |website=FFmpeg |publisher=FFmpeg project |access-date=6 January 2024}}</ref>

Four-channel, or quadraphonic, supported was originally intended to be included in CD-DA.<ref>{{Cite book|url = https://books.google.com/books?id=jqwgBQAAQBAJ&q=Four-channel+Compact+Disc+Digital+Audio&pg=PA108|title = Digital Audio and Compact Disc Technology|isbn = 978-1-4831-4039-1|last1 = Baert|first1 = Luc|last2 = Theunissen|first2 = Luc|last3 = Vergult|first3 = Guido|date = 2013-10-22| publisher=Newnes |access-date = 27 August 2023|archive-date = 27 August 2023|archive-url = https://web.archive.org/web/20230827104057/https://books.google.com/books?id=jqwgBQAAQBAJ&q=Four-channel+Compact+Disc+Digital+Audio&pg=PA108|url-status = live}}</ref> The Red Book specification briefly mentioned a four-channel mode in its June 1980,<ref name="RedBook1980">"Red Book" Audio CD specification, June 1980, Sony/Philips</ref> September 1983,<ref name="RedBook1983">"Red Book" Audio CD specification, September 1983, Sony/Philips</ref> and November 1991<ref name="RedBook1991">"Red Book" Audio CD specification, November 1991, Sony/Philips</ref> 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 the [[Organization:International Electrotechnical Commission|International Electrotechnical Commission]] and became IEC 908:1987,<ref name="IEC1987">{{citation |url=https://webstore.iec.ch/publication/18347 |title=IEC 60908:1987 Compact disc digital audio system |access-date=6 May 2015 |archive-date=4 September 2015 |archive-url=https://web.archive.org/web/20150904041217/https://webstore.iec.ch/publication/18347 |url-status=live }}</ref> and later IEC 60908:1999.<ref name="IEC1999">{{citation |url=https://webstore.iec.ch/preview/info_iec60908%7Bed2.0%7Db.pdf |title=IEC 60908:1999 Audio recording – Compact disc digital audio system |access-date=6 May 2015 |archive-date=16 October 2015 |archive-url=https://web.archive.org/web/20151016064048/https://webstore.iec.ch/preview/info_iec60908%7Bed2.0%7Db.pdf |url-status=live }}</ref> 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 ==
The creators of the CD originally aimed at a playing time of 60&nbsp;minutes with a disc diameter of 100&nbsp;mm (Sony) or 115&nbsp;mm (Philips).<ref name=Immink2 /> Sony vice-president Norio Ohga suggested extending the capacity to 74 minutes to accommodate the recording of Wilhelm Furtwängler conducting [[History:Ludwig van Beethoven|Ludwig van Beethoven]]'s Ninth Symphony at the 1951 Bayreuth Festival.<ref name="PhilBeet" /><ref name="Auto45-6" /> The additional 14-minute playing time subsequently required changing to a 120&nbsp;mm disc. Kees Schouhamer Immink, Philips' chief engineer, however, denies this, 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.<ref name=Immink /><ref name=Immink2 />

According to a ''Sunday Tribune'' interview,<ref name="ferguscassidy" /> the story is slightly more involved. In 1979, Philips owned PolyGram, one of the world's largest distributors of music. PolyGram had set up a large experimental CD plant in Hannover, Germany, which could produce huge numbers of CDs having a diameter of 115&nbsp;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 by Ohga was used to push Philips to accept 120&nbsp;mm, so that Philips' PolyGram lost its edge on disc fabrication.<ref name="ferguscassidy" />

The 74-minute playing time of a CD, which is longer than the 22&nbsp;minutes per side<ref name="Auto45-7" /><ref name="Auto45-8" /> typical of long-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 more bonus 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 with DJ Jazzy Jeff & The Fresh Prince's double-album ''He'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 or packaged as double-CDs to be re-released on a single disc, such as ''1999'' by Prince in the case of the former and ''Tommy'' by the Who in the case of the latter.

Playing times beyond 74&nbsp;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 within ''Red Book'' tolerances.<ref name="Auto45-9" /> Current manufacturing processes allow an audio CD to contain up to 82 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 current practice, maximum CD playing time has crept higher by reducing minimum engineering tolerances.

{| class="wikitable"
|+Progression in the maximum duration of released audio CDs
|-
! Title !! Artist !! Label !! Released !! Time
|-
| ''Mission of Burma'' (compilation) || Mission of Burma || Rykodisc || 1988 || 80:08<ref name="Auto45-11" />
|-
|Myこれ!クション 内海和子 ベスト (''My Kore! Kushon Kazuko Utsumi Best'')
(compilation)
|内海和子 (Kazuko Utsumi)
|Pony Canyon – PCCA-01870
|2003
|80:12<ref>{{Cite web |title=内海和子/内海和子 ベスト |url=https://tower.jp/item/973090/%E5%86%85%E6%B5%B7%E5%92%8C%E5%AD%90-%E3%83%99%E3%82%B9%E3%83%88 |access-date=2022-09-25 |website=tower.jp |archive-date=27 August 2023 |archive-url=https://web.archive.org/web/20230827104648/https://tower.jp/item/973090/%E5%86%85%E6%B5%B7%E5%92%8C%E5%AD%90-%E3%83%99%E3%82%B9%E3%83%88 |url-status=live }}</ref>
|-
| ''Late Romantic Masterworks''
| Andrew Fletcher
| Mirabilis Records
| 1990
| 80:51<ref name="ambisonic.info">{{Cite web|url=https://ambisonic.info/mirabilis.html|title=Ambisonic Info &#124; Mirabilis Recordings|access-date=3 October 2021|archive-date=27 August 2023|archive-url=https://web.archive.org/web/20230827104607/https://ambisonic.info/mirabilis.html|url-status=live}}</ref>
|-
| ''JS Bach, Das Orgelbüchlein''
| Richard Marlow
| Mirabilis Records
| 1990
| 82:04<ref name="ambisonic.info" />
|-
| Bruckner's Fifth (live) || Munich Philharmonic cond. Christian Thielemann || Deutsche Grammophon/Universal Classics 477 5377 || 2004 || 82:34<ref name="Auto45-10" />
|-
| Sergey Tanyiev works for piano and ensemble
| Vadim Repin, Ilya Gringolts, Nobuko Imai, Lynn Harrell, and Mikhail Pletnev
| Deutsche Grammophon/Universal Classics 477 5419
| 2005
| 82:34<ref>{{Cite web|url=https://www.discogs.com/release/6096529-Taneyev-Vadim-Repin-Ilya-Gringolts-Nobuko-Imai-Lynn-Harrell-Mikhail-Pletnev-Chamber-Music-Piano-Quin|title=Taneyev – Vadim Repin, Ilya Gringolts, Nobuko Imai, Lynn Harrell, Mikhail Pletnev – Chamber Music: Piano Quintet = Klavierquintett • Piano Trio = Klaviertrio|date=1 July 2005|access-date=2 June 2023|website=Discogs.com|archive-date=27 August 2023|archive-url=https://web.archive.org/web/20230827104710/https://www.discogs.com/release/6096529-Taneyev-Vadim-Repin-Ilya-Gringolts-Nobuko-Imai-Lynn-Harrell-Mikhail-Pletnev-Chamber-Music-Piano-Quin|url-status=live}}</ref>
|-
|Chopin & Schumann Etudes
|Valentina Lisitsa
|Decca/Universal Classics 478 7697
|2014
|85:16<ref>{{Cite web|url=https://www.amazon.com/%C3%89tudes-Valentina-Lisitsa/dp/B00NVY8VJE|title=Valentina Lisitsa – Études – Amazon.com Music|website=Amazon.com|access-date=1 January 2017|archive-date=1 January 2017|archive-url=https://web.archive.org/web/20170101231453/https://www.amazon.com/%C3%89tudes-Valentina-Lisitsa/dp/B00NVY8VJE|url-status=live}}</ref>
|-
|So80s Presents Alphaville
|Alphaville (curated by Blank & Jones)
|Soulfood
|2014
|85:10 and 85:57<ref>{{Cite web|url=https://www.discogs.com/Alphaville-Curated-By-Blank-Jones-So80s-Soeighties-Presents-Alphaville/master/780651|title=Alphaville Curated By Blank & Jones – So80s (Soeighties) Presents Alphaville|website=[[Company:Discogs|Discogs]]|access-date=21 October 2019|archive-date=29 October 2019|archive-url=https://web.archive.org/web/20191029044548/https://www.discogs.com/Alphaville-Curated-By-Blank-Jones-So80s-Soeighties-Presents-Alphaville/master/780651|url-status=live}}</ref>
|-
|Mozart Violin Concertos (Mozart 225 Boxed Set, CD75)
|Various Artists
|Deutsche Grammophon/Universal Classics 478 9864
|2016
|86:30<ref>{{Cite news|url=http://www.kirkville.com/cds-longer-than-80-minutes-are-becoming-more-common/|title=CDs Longer than 80 Minutes Are Becoming More Common|last=McElhearn|first=Kirk|date=12 May 2017|work=Kirkville|access-date=12 May 2017|language=en-US|archive-date=17 May 2017|archive-url=https://web.archive.org/web/20170517003528/http://www.kirkville.com/cds-longer-than-80-minutes-are-becoming-more-common/|url-status=live}}</ref>
|-
|''Bäst of''
|Die Ärzte
|Hot Action/Universal 930 003
|2006
|88:41 on disc 1, 89:07 on disc 2<ref>{{Cite web|url=https://www.discogs.com/Die-%C3%84rzte-B%C3%A4st-Of/release/806980|title=Die Ärzte – Bäst Of|website=Discogs |access-date=31 January 2021|language=en-US|archive-date=21 February 2021|archive-url=https://web.archive.org/web/20210221082151/https://www.discogs.com/Die-%C3%84rzte-B%C3%A4st-Of/release/806980|url-status=live}}</ref>
|-
|}

== Technical specifications ==

=== Data encoding ===
Each audio sample is a [[Signedness|signed]] 16-bit [[Two's complement|two's complement]] [[Integer (computer science)|integer]], with sample values ranging from −32768 to +32767. The source audio data is divided into frames, containing twelve [[Sampling (signal processing)|samples]] each (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, as a whole, is then subjected to [[Cross-interleaved Reed–Solomon coding|CIRC]] encoding, which segments and rearranges the data and expands it with [[Error correction code|error correction code]]s 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 to [[Burst error|burst error]]s. Therefore, a physical frame on the disc will actually contain information from multiple logical audio frames. This process adds 64 bits of error correction data to each frame. After this, 8 bits of subcode or subchannel data are added to each of these encoded frames, which is used for control and addressing when playing the CD.

CIRC encoding plus the subcode byte generate 33-bytes long frames, called "channel-data" frames. These frames are then modulated through [[Engineering:Eight-to-fourteen modulation|eight-to-fourteen modulation]] (EFM), where each 8-bit word is replaced with a corresponding 14-bit word designed to reduce the number of transitions between 0 and 1. This reduces the density of [[Engineering:Compact disc#Physical details|physical pits]] on the disc and provides an additional degree of error tolerance. Three "merging" bits 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 of "channel data" (which are decoded to only 192 bits of music).

The frames of channel data are finally written to disc physically in the form of [[Engineering:Compact disc#Physical details|pits 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.
A Red Book-compatible [[Engineering:CD-R|CD-R]] has 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 correction [[CD-ROM#Sector structure|sector structure]] used on audio CDs and [[Engineering:Video CD|video CD]]s (''[[CD-ROM#Mode 2 Form 2|Mode 2 Form 2]]'') than on data discs (''Mode 1'' or ''Mode 2 Form 1''), [[Engineering:C2 error|C2 error]]s are not correctable and signify data loss.<ref>{{cite web  |title=Fehlerprotoll / Error Check CD  |url=https://just-add-grooves.de/faq-lexikon-cd-vinyl/94-fehlerprotoll-error-check-cd |author1=Alex |website=Just Add Grooves |language=de-de  |access-date=9 August 2020  |archive-date=9 August 2020  |archive-url=https://web.archive.org/web/20200809161953/https://just-add-grooves.de/faq-lexikon-cd-vinyl/94-fehlerprotoll-error-check-cd  |url-status=live  }}</ref><ref name=wiethoff>{{cite web |last1=Wiethoff |first1=André |title=Exact Audio Copy: Audiodaten von optischen Speichermedien extrahieren |url=https://www.hs-rm.de/fileadmin/persons/khofmann/Gastvortraege/Vortragsfolien/20110415-wiethoff.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://www.hs-rm.de/fileadmin/persons/khofmann/Gastvortraege/Vortragsfolien/20110415-wiethoff.pdf |archive-date=2022-10-09 |url-status=live |access-date=9 August 2020 |website=Hochschule Rhein-Main |pages=51–53 |language=de |date=15 April 2011}}</ref> Even with uncorrectable errors, a compact disc player interpolates the [[Data loss|data loss]] with the aim of making the damage unhearable.<ref>{{cite web |title=CD |url=https://cs.stanford.edu/people/eroberts/cs201/projects/1997-98/optical-media/cd2.html |website=cs.stanford.edu |publisher=Stanford.edu |access-date=9 August 2020 |language=en |quote=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. |archive-date=9 August 2020 |archive-url=https://web.archive.org/web/20200809203424/https://cs.stanford.edu/people/eroberts/cs201/projects/1997-98/optical-media/cd2.html |url-status=live }}</ref>

=== Data structure ===
[[File:Basic Illustration and mesures of a CD.svg|thumb|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 the ''program area''. This section is preceded by a ''lead-in'' track and followed by a ''lead-out'' track. The lead-in and lead-out tracks encode only silent audio, but all three sections contain subcode data 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 absolute [[Timecode|timecode]], relative to the start of the program area, in MSF format: minutes, seconds, and fractional seconds called ''frames''. 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 the [[Partition table|partition table]] on hard drives. Nonstandard or corrupted TOC records are abused as a form of CD/DVD copy protection, in e.g. the key2Audio scheme.

==== Tracks ====
The largest entity on a CD is called a track. A CD can contain up to 99 tracks (including a data track for mixed 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 the [[Engineering:Pregap|pregap]] being index 0. Sometimes hidden tracks are 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's ''Hack'' was one of very few CD releases to do this, following a release with an equally obscure CD+G feature.) 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 ====
The smallest entity in a CD is a channel-data ''frame'', 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 one subcode byte. As described in the "Data encoding" section, after the EFM modulation the number of bits in a frame totals 588.

On a ''Red Book'' audio CD, data is addressed using the ''MSF scheme'', with [[Timecode|timecode]]s expressed in minutes, seconds and another type of ''frames'' (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-ROM]] and related [[Engineering:Ripping|Digital Audio Extraction]] (DAE) technology introduced the term ''[[CD-ROM#CD-ROM format|sector]]'' to refer to each timecode frame, with each sector being identified by a sequential [[Integer|integer]] number starting at zero, and with tracks aligned on sector boundaries. An audio CD sector corresponds to 2,352 bytes of decoded data. The ''Red Book'' does 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:

{| class="wikitable"
|-
! Track level
| colspan = 6 | Track N
|-
! Timecode frame and sector level
| colspan = 3 | 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 ===
The audio [[Bit rate|bit rate]] for a ''Red Book'' audio CD is 1,411,200 bits per second (1,411 kbit/s) or 176,400 bytes 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-ROM]] is 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 ===
Unlike on a [[Engineering:DVD|DVD]] or [[CD-ROM]], there are no "[[Computer file|files]]" on a ''Red Book'' audio CD; there is only one continuous stream of LPCM audio data, and a parallel, smaller set of 8 subcode data streams. Computer [[Operating system|operating system]]s, however, may provide access to an audio CD as if it contains files. For example, [[Software:Microsoft Windows|Windows]] represents the CD's Table of Contents as a set of Compact Disc Audio track (CDA) files, each file containing indexing information, not audio data. By contrast however, [[Software:Finder|Finder]] on [[Software:MacOS|macOS]] presents the CD's content as an actual set of files, with the [[Audio Interchange File Format|AIFF]]-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 called [[Engineering:Ripping|ripping]], digital audio extraction software can be used to read CD-DA audio data and store it in files. Common [[Audio file format|audio file format]]s for this purpose include [[WAV]] and AIFF, which simply preface the LPCM data with a short [[Header (computing)|header]]; [[Software:FLAC|FLAC]], [[Software:Apple Lossless|ALAC]], and [[Windows Media Audio#Windows Media Audio Lossless|Windows Media Audio Lossless]], which compress the LPCM data in ways that conserve space yet allow it to be restored without any changes; and various [[Lossy compression|lossy]], [[Perceptual audio coder|perceptual coding]] formats like [[MP3]], [[Advanced Audio Coding|AAC]], and [[Software:Opus (audio format)|Opus]], 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 ==
Recording publishers have created CDs that violate the ''Red Book'' standard. Some do so for the purpose of [[Copy protection|copy prevention]], using systems like Copy Control. Some do so for extra features such as [[Engineering:DualDisc|DualDisc]], which includes both a CD layer and a DVD layer whereby the CD layer is much thinner, 0.9&nbsp;mm, than required by the ''Red Book'', which stipulates a nominal 1.2&nbsp;mm, but at least 1.1&nbsp;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.

[[Engineering:Super Audio CD|Super Audio CD]] was a standard published in 1999 that aimed to provide better audio quality than CDs. DVD-Audio emerged at around the same time.<ref name="Auto45-12" /> Both formats were designed to feature audio of higher fidelity by using a higher sampling rate and [[Engineering:DVD|DVD]] media. Neither format was widely accepted.

== Copyright issues ==
There have been moves by the recording industry to make audio CDs (Compact Disc Digital Audio) unplayable on computer [[CD-ROM]] drives, 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 the Red Book) to inform consumers which discs do not permit full [[Social:Fair use|fair use]] of their content.

In 2005, Sony BMG Music Entertainment was criticized when a copy protection mechanism known as [[Extended Copy Protection]] (XCP) used on some of their audio CDs automatically and surreptitiously installed copy-prevention software on computers (see [[Social:Sony BMG copy protection rootkit scandal|Sony BMG copy protection rootkit scandal]]). Such discs are not legally allowed to be called CDs or Compact Discs because they break the Red Book standard governing CDs, and Amazon.com for example describes them as "copy protected discs" rather than "compact discs" or "CDs".

== See also ==
* [[Audio Interchange File Format]] (AIFF)
* [[Engineering:Digital rights management|Digital rights management]]
* [[Extended Copy Protection]]
* Four-channel compact disc digital audio
* [[Gapless playback]]

== Notes ==
{{Notelist}}

== References ==
{{Reflist|refs=
<ref name="BBC">{{cite news | url = http://news.bbc.co.uk/2/hi/technology/6950933.stm | title = How the CD was developed | work = BBC News | date = 17 August 2007 | access-date = 17 August 2007 | archive-date = 7 January 2012 | archive-url = https://web.archive.org/web/20120107064451/http://news.bbc.co.uk/2/hi/technology/6950933.stm | url-status = live }}</ref>
<ref name="Auto45-1">{{cite web |url=http://www.philips-historische-producten.nl/cd-uk.html |title=Philips Compact Disc |work=Philips Historical Products |access-date=24 January 2016 |archive-url=https://web.archive.org/web/20160425035643/http://www.philips-historische-producten.nl/cd-uk.html |archive-date=25 April 2016 }}</ref>
<ref name="Auto45-2">{{cite web |website=Webstore.iec.ch |url=https://webstore.iec.ch/publication/18347 |title=IEC 60908:1987 Compact disc digital audio system |access-date=6 May 2015 |archive-date=4 September 2015 |archive-url=https://web.archive.org/web/20150904041217/https://webstore.iec.ch/publication/18347 |url-status=live }}</ref>
<ref name="Auto45-3">{{cite web |website=Webstore.iec.ch |url=https://webstore.iec.ch/preview/info_iec60908%7Bed2.0%7Db.pdf |title=IEC 60908:1999 Audio recording – Compact disc digital audio system |access-date=6 May 2015 |archive-date=16 October 2015 |archive-url=https://web.archive.org/web/20151016064048/https://webstore.iec.ch/preview/info_iec60908%7Bed2.0%7Db.pdf |url-status=live }}</ref>
<ref name="Auto45-4">{{Cite web|url=https://stason.org/TULARC/pc/cd-recordable/2-35-Why-44-1KHz-Why-not-48KHz.html|title=2-35] Why 44.1KHz? Why not 48KHz?|first=Stas Bekman: stas (at)|last=stason.org|website=stason.org|access-date=21 January 2023|archive-date=21 January 2023|archive-url=https://web.archive.org/web/20230121153032/https://stason.org/TULARC/pc/cd-recordable/2-35-Why-44-1KHz-Why-not-48KHz.html|url-status=live}}</ref>
<ref name="PhilBeet">{{cite web | url = http://www.marantzphilips.nl/The_cd_laser/ | archive-url = https://web.archive.org/web/20090202030718/http://marantzphilips.nl/The_cd_laser/ | archive-date = 2 February 2009 | title = Beethoven's Ninth Symphony of Greater Importance than Technology | author = Philips | access-date = 9 February 2007 }}</ref>
<ref name="Auto45-6">{{cite web | url = http://www.aes.org/historical/store/oralhistory/?code=OHP-016-DVD | title = AES Oral History Project: Kees A.Schouhamer Immink | author = AES | access-date = 29 July 2008 | archive-date = 15 May 2009 | archive-url = https://web.archive.org/web/20090515010836/http://www.aes.org/historical/store/oralhistory/?code=OHP-016-DVD | url-status = live }}</ref>
<ref name="ferguscassidy">{{cite news | url = http://www.ferguscassidy.ie/ethos-23-Oct-2005.html | title = Great Lengths | last = Cassidy | first = Fergus | format = reprint | newspaper = Sunday Tribune | date = 23 October 2005 | archive-date=12 October 2007 | archive-url=https://web.archive.org/web/20071012121905/http://ferguscassidy.ie/ethos-23-Oct-2005.html |access-date = 7 January 2017 }}</ref>
<ref name="Auto45-7">{{cite book |last1=Hoffmann |first1=Frank |last2=Ferstler |first2=Howard |title=Encyclopedia of Recorded Sound |publisher=CRC Press |year=2005| page=1289 |isbn=978-0-415-93835-8}}</ref>
<ref name="Auto45-8">Goldmark, Peter. ''Maverick inventor; My Turbulent Years at CBS.'' New York: Saturday Review Press, 1973.</ref>
<ref name="Auto45-9">{{cite web |url=http://www.cdrfaq.org/faq03.html#S3-8 |title=CD-Recordable FAQ |author=Andy McFadden |date=9 January 2010 |access-date=30 December 2010 |archive-date=18 November 2013 |archive-url=https://web.archive.org/web/20131118040105/http://www.cdrfaq.org/faq03.html#S3-8 |url-status=live }}</ref>
<ref name="Auto45-10">{{ cite web |archive-url=https://web.archive.org/web/20130516001041/http://audaud.com/2005/07/bruckner-symphony-no-5-in-b-flat-major-original-version-munich-philharmonicchristian-thielemann-dgg/ |url=http://audaud.com/2005/07/bruckner-symphony-no-5-in-b-flat-major-original-version-munich-philharmonicchristian-thielemann-dgg/ |title= BRUCKNER: Symphony No. 5 in B flat major (original version) — Munich Philharmonic/Christian Thielemann — DGG – Audiophile Audition |date=13 July 2005 |publisher=Audiophile Audition |archive-date=16 May 2013}}</ref>
<ref name="Auto45-11">{{cite web|url=http://www.discogs.com/Mission-Of-Burma-Mission-Of-Burma/release/1129709|title=Mission of Burma 1988 Rykodisc compilation information|publisher=Discogs|access-date=18 January 2011|quote=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.|archive-date=17 October 2010|archive-url=https://web.archive.org/web/20101017071502/http://www.discogs.com/Mission-Of-Burma-Mission-Of-Burma/release/1129709|url-status=live}}</ref>
<ref name="Auto45-12">{{ cite web |last=Taylor |first=Jim |title=DVD FAQ |url=http://www.dvddemystified.com/dvdfaq.html |work=DVD Demystified |access-date=21 August 2012 |archive-url=https://web.archive.org/web/20090822172353/http://www.dvddemystified.com/dvdfaq.html |archive-date=22 August 2009 }}</ref>
<ref name="Immink2">{{Cite journal
|journal=IEEE Information Theory Society Newsletter
|volume=57
|date=2007
|title=Shannon, Beethoven, and the Compact Disc
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<ref name="Immink">{{Cite journal
|journal=Journal of the Audio Engineering Society
|volume=46
|issue=5
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|author=K. Schouhamer Immink
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<ref name=Leis>{{cite book|author=John W. Leis|url=https://books.google.com/books?id=Qtd-e1NtZVkC&pg=PA82|title=Digital Signal Processing Using MATLAB for Students and Researchers|date=2011|publisher=John Wiley & Sons|isbn=978-1-118-03380-7|page=82|quote=The ''Nyquist rate'' is twice the bandwidth of the signal ... The ''Nyquist frequency'' or ''folding frequency'' is half the sampling rate and corresponds to the highest frequency which a sampled data system can reproduce without error.|access-date=14 September 2022|archive-date=27 August 2023|archive-url=https://web.archive.org/web/20230827104606/https://books.google.com/books?id=Qtd-e1NtZVkC&pg=PA82|url-status=live}}</ref>

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}}

== External links ==
* [http://www.ip.philips.com/licensing/program/15 Philips' Audio Standards licensing info]
* [https://webstore.iec.ch/preview/info_iec60908%7Bed2.0%7Db.pdf IEC 60908:1999 Audio recording – Compact disc digital audio system]
* [http://wiki.multimedia.cx/index.php?title=PCM#Red_Book_CD_Audio MultimediaWiki article about PCM and ''Red Book'' CD Audio]

{{List of IEC standards}}
{{Rainbow Books}}

[[Category:Joint ventures]]

{{Sourceattribution|Compact Disc Digital Audio}}