Examine individual changes

'{{Refimprove|date=June 2009}} [[File:Zoom H4n audio recording levels.jpg|thumb|Audio levels display on a digital audio recorder ([[Zoom H4n]])]] In '''digital recording''', [[audio signal]]s picked up by a [[microphone]] or other [[transducer]] or [[video signal]]s picked up by a [[camera]] or similar device are [[Analog to digital conversion|converted]] into a stream of [[discrete number]]s, representing the changes over time in [[air pressure]] for audio, and [[Color|chroma]] and [[luminance]] values for video, then recorded to a storage device. To play back a digital sound recording, the numbers are retrieved and converted back into their original [[analog signal|analog]] waveforms so that they can be heard through a [[loudspeaker]]. To play back a digital video recording, the numbers are retrieved and converted back into their original [[analog signal|analog]] waveforms so that they can be viewed on a [[video monitor]], [[television]] or other display. == Timeline== *October 3, 1938: British telephone engineer [[Alec Harley Reeves]] files at the French Patent Office the first patent describing the technique known today as [[Pulse-code modulation]] (PCM). Later, Reeves files also in the USA on November 22, 1939. <ref>{{cite web|title=Patent US2272070: Electric signaling system|url=https://patentimages.storage.googleapis.com/eb/8e/9f/32ad53d114d2d6/US2272070.pdf|publisher=United States Patent Office|accessdate=23 December 2017}}</ref><ref>[http://www.privateline.com/TelephoneHistory2/reeves.html Robertson, David. ''Alec Reeves 1902–1971'' Privateline.com: Telephone History.] {{webarchive|url=https://web.archive.org/web/20140511182503/http://www.privateline.com/TelephoneHistory2/reeves.html |date=2014-05-11 }} Accessed November 14, 2009</ref> It was first proposed as a [[telephony]] technology.<ref name="Fine">{{cite journal |author=Thomas Fine |year=2008 |title=The dawn of commercial digital recording |journal=[[ARSC Journal]] |volume=39 |issue=1 |pages=1–17 |url=http://www.aes.org/aeshc/pdf/fine_dawn-of-digital.pdf}}</ref> *1943: [[Bell Labs|Bell Telephone Laboratories]] develops the first PCM-based digital scrambled speech transmission system, [[SIGSALY]],<ref>[http://www.nsa.gov/about/cryptologic_heritage/center_crypt_history/publications/sigsaly_story.shtml#3 J. V. Boone, J. V., Peterson R. R.: ''Sigsaly – The Start of the Digital Revolution''] Accessed November 14, 2009</ref> in response to German interception of military telephone traffic during [[World War II]]. The twelve transmission points were retired after the war. *1957: [[Max Mathews]] of Bell develops the process to digitally [[sound recording|record]] sound on a [[computer]]. *1967: The first [[monaural]] PCM encoder was developed by [[NHK]]'s research facilities in Japan.<ref name="Fine"/> The 30kHz 12-bit device used a [[compander]] (similar to [[Dbx (noise reduction)|DBX Noise Reduction]]) to extend the dynamic range, and stored the signals on a [[video tape recorder]]. *1969: NHK expands the PCM encoder's capabilities to 2-channel [[stereo]] and 32kHz 13-bit resolution. <ref name="Fine" /> *1970: [[United States|American]] [[inventor]] [[James Russell (inventor)|James Russell]] patents the first digital-to-optical recording and playback system, <ref>{{Cite web|url=https://docs.google.com/viewer?url=patentimages.storage.googleapis.com/pdfs/US3501586.pdf|title=Patent US 3501586: Analog to digital to optical photographic recording and playback system.|last=|first=|date=|website=|publisher=United States Patent Office|archive-url=|archive-date=|dead-url=|access-date=}}</ref>which would later lead to the [[Compact Disc]]. *January 1971: Using NHK's experimental PCM recording system, Dr. Takeaki Anazawa, an engineer at [[Denon]], records '''the world's first commercial digital recordings''', ''Something'' by [[Steve Marcus]] & Jiro Inagaki (January 25, 1971) and ''The World Of Stomu Yamash'ta 1 & 2'' by [[Stomu Yamash'ta]] (January 11, 1971).<ref name="Fine" /> Both have to be recorded live, without edits. Marcus is released first (in February 1972), making it the '''first released digital recording'''. *1972: Using lessons learned from the NHK encoder, [[Denon]] unveils the first 8-channel PCM encoder, the DN-023R, which uses 47.25kHz 13-bit PCM resolution and 4-head open reel broadcast [[video tape recorder]].<ref name="Fine"/> The first recording with this new system is the [[Smetana Quartet]] performing [[Mozart]]'s ''String Quartets [[String Quartet No. 17 (Mozart)|K.458]] and [[String Quartet No. 15 (Mozart)|K.421]]'', recorded in Tokyo April 24–26 and released that October. At least six other Denon-recorded digital [[LP record]]s are released in October, including jazz, classical and traditional Japanese music.<ref name="Fine"/><ref>https://www.discogs.com/Nozomi-Aoki-Columbia-New-Sound-Orchestra-Genso-Kumikyoku-Nippon-Fantasic-Suite-Japan/release/12589188</ref> *December 2-3, 1974: The [[Jean-François Paillard|Paillard Chamber Orchestra]] records the '''first digital recording outside Japan''', in [[Paris]]' [[Notre-Dame de Paris|Notre Dame Cathedral]], using Denon's DN-023R. [[Johann Sebastian Bach|Bach]]'s "[[The Musical Offering]]" (BWV 1079) is released on LP May 1975.<ref name="Fine"/> *December 12-19, 1974: [[Helmuth Rilling]] records three [[Johann Sebastian Bach|Bach]] organ works inside the Gedächtniskirche, [[Stuttgart]] Germany using the DN-023R.<ref>https://www.discogs.com/JS-Bach-Helmuth-Rilling-Organ-Works/release/5697765</ref> *May 1975: [[University of Utah]] professor [[Thomas Stockham]] develops a PCM digital audio recorder of his own design, using computer tape drives as the storage system. He founds the company [[Soundstream]] to offer it commercially.<ref>http://www.arpjournal.com/asarpwp/soundstream-the-introduction-of-commercial-digital-recording-in-the-united-states/</ref> Between 1977 and 1980 a total of eighteen 4-channel 50kHz 16-bit units were manufactured, of which seven were sold (at about $150,000 each). Over 200 recordings were made on his equipment, almost half of all digital classical recordings made in the 1970s.<ref>http://history.sandiego.edu/gen/recording/stockham.html</ref><ref>http://www.arpjournal.com/asarpwp/soundstream-the-introduction-of-commercial-digital-recording-in-the-united-states/</ref> *1976: the prototype [[Soundstream]] 37.5kHz, 16-bit, 2-channel recorder<ref name="Fine"/> is used to record the [[Santa Fe Opera]] performing [[Virgil Thomson]]'s opera ''[[The Mother of Us All]]'' for [[New World Records]], making it '''the first US digital recording'''. However, the digital recorder is just a backup to the main analog [[multi-track recording|multi-track recorder]], and the analog recording is deemed superior and thus used for the LP release. The backup digital tape was presented at the October 1976 [[Audio Engineering Society|AES]] Convention in New York, but never commercially released. *1977: Denon develops the smaller portable PCM recording system, the DN-034R. Like the DN-023R it records 8 channels at 47.25&nbsp;kHz, but it uses 14-bits "with emphasis, making it equivalent to 15.5 bits." It also allowed for overdubbing for the first time, crucial for professional recording.<ref name="Fine"/> *August 28–31, 1977: Soundstream's second-generation PCM system runs in the background of a California [[direct to disc recording]] session by organist [[Virgil Fox]] for Crystal Clear Records. When initially released the resulting LPs were pressed from the direct-to-disc acetate, though the later CD reissue (1987) comes from the digital backup tapes when the acetates were no longer usable. The CD reissue was made by Bainbridge Records.<ref name="Fine" /><ref>{{Cite web|url=https://www.discogs.com/es/Virgil-Fox-The-Digital-Fox-Vols-1-2/release/2917399|title=Virgil Fox - The Digital Fox Volume 1 And 2 (CD, Album) at Discogs|last=|first=|date=|website=|publisher=Discogs|archive-url=|archive-date=|dead-url=|access-date={{date|Dec 23 2017|mdy}}}}</ref> *September 1977: Sony introduces the PCM-1 Audio Unit ($4400 street price)<ref>http://www.thevintageknob.org/sony-PCM-1.html</ref> (44.056kHz, 14-bit), the first consumer (well-heeled) PCM encoder. It required the use of a home video tape recorder for storage.<ref>https://www.sony.net/SonyInfo/CorporateInfo/History/SonyHistory/2-07.html</ref> *November 4-7, 1977: [[3M]] demonstrates a prototype 2-channel 50.4kHz 16-bit digital recorder running on 1-inch tape at 45 ips at the New York [[Audio Engineering Society|AES]] Convention.<ref name="Fine" /> As no true 16-bit converters were available, it combined separate 12-bit and 8-bit converters to create 16-bit performance.<ref>https://www.mixonline.com/technology/1978-3m-digital-audio-mastering-system-377974</ref> *November 28, 1977: Denon brings their DN-034R to [[New York City]]'s Sound Ideas Studios and records [[Archie Shepp]]'s ''On Green Dolphin Street'', making it '''America's first {{em|released}} digitally-recorded commercial album'''.<ref name="Fine"/> The following two days, November 29-30, [[Frank Foster (musician)|Frank Foster]] and the Loud Minority record ''[[Manhattan Fever]]'' which is released April 1978.<ref name="Fine"/> Five other jazz albums are recorded with the DN-034R in New York before it returns to Japan in December.<ref>{{Cite web|url=http://www.jazzdisco.org/archie-shepp/discography/|title=Archie Shepp Discography|last=|first=|date=|website=www.jazzdisco.org|publisher=Jazz Discography Project|language=en-US|archive-url=|archive-date=|dead-url=|access-date={{date|Dec 22 2017|mdy}}}}</ref>{{failed verification|date=December 2015}} *March 1978: Sony introduces the professional-grade PCM-1600 Audio Processor (44.056kHz, 16-bit) (list price $40,000)<ref>https://books.google.com/books?id=KCQEAAAAMBAJ&pg=PT57&lpg=PT57&dq=Sony+PCM-1600+list+price&source=bl&ots=jY00bRFHU0&sig=HKxh76xuU_SHG_CIxHso3_A02BE&hl=en&sa=X&ved=2ahUKEwix-Y77xtXfAhVDlVQKHfbnC0UQ6AEwDnoECAoQAQ#v=onepage&q=Sony%20PCM-1600%20list%20price&f=false</ref> used with an external [[U-matic]] tape drive, making digital recording commercially available to recording studios for the first time. PCM-1610 and PCM-1630 follow.<ref>https://www.sony.net/SonyInfo/CorporateInfo/History/SonyHistory/2-10.html</ref><ref>http://www.thegreatbear.net/audio-tape/early-digital-tape-recordings-umatic-betamax-video-tape/</ref><ref>https://www.realhomerecording.com/docs/Sony_PCM-1610_brochure.pdf</ref> *April 4–5, 1978: [[Telarc International Corporation|Telarc]] uses Soundstream's PCM system to record [[Frederick Fennell]] and his Eastman Wind Ensemble playing [[Gustav Holst]]'s ''Suites for Military Band'' and [[George Frideric Handel]]'s ''[[Music for the Royal Fireworks]].'' When released on LP this became the '''first US-recorded digital classical release'''.<ref>{{cite web|url=http://www.arkivmusic.com/classical/album.jsp?album_id=3791|title=Holst, Handel, Bach / Fennell, Cleveland Symphonic ... - Telarc: TRC-80038 - Buy from ArkivMusic|author=|date=|website=www.arkivmusic.com|accessdate=9 April 2018}}</ref> *June 2, 1978: [[Sound 80]] studios in [[Minneapolis]] records the [[Saint Paul Chamber Orchestra]] performing [[Aaron Copland]]'s ''[[Appalachian Spring]]''. This session is set up as a [[direct to disc recording]], with the prototype [[3M]] 50.4kHz digital recorder running in the background. There is some disagreement,<ref name="Fine"/><ref>{{cite web|url=https://www.thespco.org/about-us/recording-discography/|title=Recording Discography|author=|date=18 February 2014|website=thespco.org|accessdate=9 April 2018}}</ref> but it appears the resulting [[LP record]] (Sound80 Records S80-DLR-101) was taken from the digital backup tapes rather than the direct-to-disc acetate.<ref>https://www.discogs.com/Aaron-Copland-Charles-Ives-Conductor-Dennis-Russell-Davies-Orchestra-The-Saint-Paul-Chamber-Orchestr/master/1069988</ref> In 1984 the session is re-released on [[Compact Disc]] by ProArte. This recording was nominated for three [[Grammy Award]]s, winning "[[Grammy Award for Best Chamber Music Performance|Best Chamber Music Performance]]" (1980), <ref>https://www.mixonline.com/technology/1978-3m-digital-audio-mastering-system-377974</ref> making it the '''first digital recording so honored'''.<ref>http://www.startribune.com/st-paul-chamber-orchestra-grabs-grammy-for-best-chamber-performance/471556164/</ref> *Early June 1978: [[Sound 80]] records ''[[Flim and the BB's]]'' debut self-titled album as another [[direct to disc recording]] again with the experimental [[3M]] recorder in the background. Again the acetate is deemed not as good as the digital backup, so the digital master is used for the [[LP record]] (Sound80 Records S80-DLR-102). This makes it the '''first U.S. non-classical digital release'''. Within 6 months the hand-built ("[[Sound 80|very bulky and finicky]]") 3M digital recorder is disassembled, rendering the non-standard master tape unplayable. Therefore, no [[Compact Disc]] reissue is possible. The compact disc issue of the St. Paul Chamber Orchestra is unexplained. *March 8, 1979: the first [[Compact Disc]] prototype was demonstrated by [[Philips]] in [[Eindhoven]] with the respective player nicknamed "Pinkeltje". <ref>{{Cite book|title=Origins and Successors of the Compact Disc (Philips Research Book Series, Volume 11)|last=Peek|first=Hans|last2=Bergmans|first2=Jan|last3=Van Haaren|first3=Jos|last4=Toolenaar|first4=Frank|last5=Stan|first5=Sorin|publisher=Springer Science+Business Media B.V.|year=2009|isbn=978-1-4020-9552-8|location=|pages=10}}</ref><ref>{{Cite web|url=http://www.dutchaudioclassics.nl/philips_press_first_philips_cd_prototype_1978/|title=Philips first CD prototype|last=|first=|date={{date|Dec 22 2017|mdy}}|website=|publisher=Dutchaudioclassics.nl|archive-url=|archive-date=|dead-url=|access-date=}}</ref> *July 11, 1979: the '''first U.S.-recorded digitally-recorded LP of [[popular music]] (with vocals)''', ''[[Bop 'Til You Drop]]'' by guitarist [[Ry Cooder]], was released by [[Warner Bros. Records]]. The album was recorded in [[Los Angeles]] on a 32-track digital machine built by the [[3M]] corporation. <ref>{{cite web|last1=Nichols|first1=Roger|title=I Can’t Keep Up With All The Formats II|url=http://archive.li/QvGI1|publisher=Roger Nichols|accessdate=23 December 2017|archiveurl=http://rogernichols.com/EQ/EQ_2001_08.html|archivedate=20 October 2002}}</ref><ref>{{cite web|title=1978 3M Digital Audio Mastering System|url=https://www.mixonline.com/technology/1978-3m-digital-audio-mastering-system-377974|publisher=NewBay Media, LLC|accessdate=23 December 2017|date=1 September 2007}}</ref> Also, [[Stevie Wonder]] digitally recorded his [[soundtrack album]], ''[[Journey Through the Secret Life of Plants]]'', three months after Cooder's album was released, followed by the Grammy-award self-titled [[Christopher Cross (album)|debut album]] of American singer [[Christopher Cross]]. Cross' album is the '''first digitally recorded album to chart''' in the US (coincidentally also winning 5 [[Grammy Awards|Grammys]]). *October 12, 1979: [[Fleetwood Mac]]'s [[Tusk (album)]] is released. It, and [[Live (Fleetwood Mac album)]], December 8, 1980, were mastered on the Soundstream PCM from analog multi-tracks.<ref>http://www.arpjournal.com/asarpwp/soundstream-the-introduction-of-commercial-digital-recording-in-the-united-states/</ref> *1980: The Red Book standard (44.1kHz, 16-bit)<ref>https://searchstorage.techtarget.com/definition/Red-Book</ref> is established for [[Compact Disc Digital Audio]]. *1980: [[Mitsubishi Electric]] introduces the X-80 [[ProDigi]] [[Reel-to-reel audio tape recording|open reel]] 1/4" tape 15 ips 50.4kHz 16-bit digital recorder ($5000). Only 200 are sold worldwide.<ref>https://www.prosoundnetwork.com/archives/retro-review-mitsubishi-x-80-open-reel-digital-recorder</ref> *1980: Soundstream merges with Digital Recording Corporation, becoming DRC/Soundstream, to develop and market 50kHz PCM recording to an optical card. Eclipsed by the rise of the 44.1kHz [[Compact Disc]], the company is out of business after 1983.<ref>http://www.arpjournal.com/asarpwp/soundstream-the-introduction-of-commercial-digital-recording-in-the-united-states/</ref> *1981: Sony releases the PCM-F1 Digital Audio Processor ($1900)(44.056kHz, 16-bit) and matching SL-2000 [[Betamax]] VCR ($700) as a complete affordable portable (with optional batteries) home digital recording system <ref>https://www.mixonline.com/technology/1981-sony-pcm-f1-digital-recording-processor-377975</ref> *August 17, 1982: The '''first [[compact disc]] manufactured''', [[ABBA]]'s ''[[The Visitors (ABBA album)|The Visitors]]'' (because it was "mostly digitally recorded")<ref>https://www.discogs.com/ABBA-The-Visitors/release/8771945</ref> is produced in [[Hanover]], [[Germany]]. However due to production problems with it the third version didn't actually hit stores until later 1982 or early 1983. [[Billy Joel]]'s ''[[52nd Street (album)|52nd Street]]'' actually becomes '''the first CD to hit the market''', on October 1, 1982.<ref>http://www.funtrivia.com/askft/Question28718.html</ref> *September 5, 1982: [[Peter Gabriel]] releases his fourth studio album (titled [[Security (album)|''Security'']] in North America and ''Peter Gabriel IV'' elsewhere).<ref>https://petergabriel.com/release/peter-gabriel-4/</ref> When released on CD in October 1984 it becomes the '''first full-digital [[SPARS code|DDD]] release'''. It was recorded on [[Sony]]'s Mobile One digital studio<ref>https://books.google.com/books?id=_o8BDQAAQBAJ&pg=PA97&lpg=PA97&dq=%22mobile+one%22+recording+studio+peter+gabriel&source=bl&ots=0VEt1h9YiV&sig=uRrqqmQZUAS1lNkM090kTJ3sk6k&hl=en&sa=X&ved=2ahUKEwiM-ZXM4NXfAhWLGXwKHdTUALIQ6AEwB3oECAkQAQ#v=onepage&q=%22mobile%20one%22%20recording%20studio%20peter%20gabriel&f=false</ref> and mixed with a Sony PCM-1610.<ref>CD liner notes</ref> *October 1, 1982: ''[[The Nightfly]]'' by [[Donald Fagen]] is released, recorded and mixed on [[3M]]'s 32-track recorder. When the CD is issued in 1984 it becomes another early DDD release. *October 1, 1982: The first digital [[compact disc]] players are marketed by Sony (CDP-101, $900) and Philips (CD-100, $700).<ref>''[[Encyclopædia Britannica]] – Compact Disc''. 2003 Deluxe Edition CD-ROM</ref> *October 1982: [[New England Digital]] offers the [[hard disk recorder]] (Sample-to-Disk) option on the [[Synclavier]], the first commercial [[hard disk]] (HDD) recording system.<ref>{{cite web|url=http://www.500sound.com/synclavierhistory.html|title=Synclavier history|author=|date=|website=500sound.com|accessdate=9 April 2018}}</ref> *1984: Sony releases the PCM-501ES digital audio processor (44.1kHz, 16-bit) ($895 list price) which is used with an external VHS or Beta video recorder. *September 1984: [[Bruce Springsteen]]'s ''[[Born in the U.S.A.]]'' becomes the '''first US-manufactured CD''' to be released.<ref>http://www.funtrivia.com/askft/Question28718.html</ref> *1987: Sony develops [[Digital Audio Tape]]. *1989: Test broadcasts for [[NICAM stereo]] digital audio for broadcast TV began in the UK. *1990: [[digital radio]] begins in [[Canada]], using the [[L-Band]].<ref>[http://history.sandiego.edu/GEN/recording/dars.html University of San Diego: ''Digital Audio Radio Service (DARS)''] {{Webarchive|url=https://web.archive.org/web/20091015103302/http://history.sandiego.edu/gen/recording/dars.html |date=2009-10-15 }} Accessed November 14, 2009</ref> *1991: [[Alesis]] Digital Audio Tape or [[ADAT]] is a tape format used for simultaneously recording eight tracks of [[digital audio]] at once, onto [[Super VHS]] [[magnetic tape]] – a format similar to that used by consumer [[VCR]]s. The product was announced in January 1991 at the [[NAMM]] convention in [[Anaheim, California]]. The first ADAT recorders shipped over a year later in February or March 1992.<ref>Peterson, George; Robair, Gino [ed.] (1999). ''Alesis ADAT: The Evolution of a Revolution''. Mixbooks. p. 2. {{ISBN|0-87288-686-7}}</ref> *1993: [[RADAR (audio recorder)]] Random Access Digital Audio Recorder or [http://www.izcorp.com/radar RADAR] is the first single box device used for simultaneously recording 24 tracks of [[digital audio]] at once, onto [[hard disk]] drives. The product, manufactured by [[Creation Technologies]] ([http://www.izcorp.com/ iZ Technology Corporation]) was announced in October 1993 at the [[Audio Engineering Society|AES]] convention in [[New York City|New York]], [[New York (state)|New York]]. The first RADAR recorders shipped in August 1994. *1996: [[optical disc]]s and [[DVD player]]s begin selling in [[Japan]]. == Process == '''Recording''' # The analog signal is transmitted from the [[input device]] to an [[analog-to-digital converter]] (ADC). # The ADC converts this signal by repeatedly measuring the momentary level of the analog (audio) wave and then assigning a binary number with a given quantity of bits (word length) to each measuring point. # The frequency at which the ADC measures the level of the analog wave is called the [[sample rate]] or sampling rate. # A digital audio sample with a given word length represents the audio level at one moment. # The longer the word length the more precise the representation of the original audio wave level. # The higher the sampling rate the higher the upper audio frequency of the digitized audio signal. # The ADC outputs a sequence of digital audio samples that make up a continuous stream of 0s and 1s. # These binary numbers are stored on recording media such as a [[hard drive]], [[optical drive]] or in [[solid state memory]]. '''Playback''' # The sequence of numbers is transmitted from storage into a [[digital-to-analog converter]] (DAC), which converts the numbers back to an analog signal by sticking together the level information stored in each digital sample, thus rebuilding the original analog wave form. # This signal is amplified and transmitted to the [[loudspeaker]]s or video screen. == Recording of bits == Even after getting the signal converted to bits, it is still difficult to record; the hardest part is finding a scheme that can record the bits fast enough to keep up with the signal. For example, to record two channels of audio at [[44.1 kHz]] sample rate with a 16 bit word size, the recording software has to handle 1,411,200 bits per second. ===Techniques to record to commercial media=== For [[digital cassettes]], the read/write head moves as well as the tape in order to maintain a high enough speed to keep the bits at a manageable size. For [[optical disc recording technologies]] such as [[CD]]s or [[DVD]]s, a [[laser]] is used to burn microscopic holes into the dye layer of the medium. A weaker laser is used to read these signals. This works because the metallic substrate of the disc is reflective, and the unburned dye prevents reflection while the holes in the dye permit it, allowing digital data to be represented. == Concerns with digital audio recording == ===Word size=== The number of [[bit]]s used to represent a sampled [[sound wave|audio wave]] (the ''[[word size]]'') directly affects the resulting [[signal to noise ratio|noise]] in a recording after intentionally added [[dither]], or the [[distortion]] of an undithered signal<ref>{{Cite journal |journal=Journal of the Audio Engineering Society |volume=47 |date=March 1991 |title=The future of digital audio recording |author=Kees Schouhamer Immink |authorlink=Kees Schouhamer Immink |url=https://www.researchgate.net/publication/322974158_The_future_of_digital_audio_recording |pages=171-172 |quote=Keynote address was presented to the 104th Convention of the Audio Engineering Society in Amsterdam during the society's golden anniversary celebration on May 17, 1998.}}</ref>. The number of possible voltage levels at the output is simply the number of levels that may be represented by the largest possible digital number (the number 2 raised to the power of the number of bits in each sample). There are no “in between” values allowed. If there are more bits in each sample the waveform is more accurately traced, because each additional bit doubles the number of possible values. The distortion is roughly the percentage that the least significant bit represents out of the average value. Distortion (as a percentage) in digital systems increases as signal levels decrease, which is the opposite of the behavior of analog systems.<ref>{{Cite web|title = Digital Recording|url = http://artsites.ucsc.edu/ems/music/tech_background/TE-16/teces_16.html|website = artsites.ucsc.edu|accessdate = 2015-09-29}}</ref> ===Sample rate=== The [[Sampling rate|sample rate]] is just as important a consideration as the word size. If the sample rate is too low, the sampled signal cannot be reconstructed to the original sound signal. To overcome aliasing, the sound signal (or other signal) must be sampled at a rate at least twice that of the highest frequency component in the signal. This is known as the [[Nyquist-Shannon sampling theorem]]. For recording music-quality audio the following PCM sampling rates are the most common: 44.1, 48, 88.2, 96, 176.4, and 192&nbsp;kHz. When making a recording, experienced audio recording and mastering engineers will normally do a master recording at a higher sampling rate (i.e. 88.2, 96, 176.4 or 192&nbsp;kHz) and then do any editing or mixing at that same higher frequency. High resolution PCM recordings have been released on DVD-Audio (also known as DVD-A), DAD (Digital Audio Disc—which utilizes the stereo PCM audio tracks of a regular DVD), DualDisc (utilizing the DVD-Audio layer), or Blu-ray (Profile 3.0 is the Blu-ray audio standard, although as of mid-2009 it is unclear whether this will ever really be used as an audio-only format). In addition it is nowadays also possible and common to release a high resolution recording directly as either an uncompressed WAV or lossless compressed FLAC file<ref>{{cite web|url=http://flac.sourceforge.net/news.html|title=FLAC - news|first=Josh|last=Coalson|date=|website=flac.sourceforge.net|accessdate=9 April 2018}}</ref> (usually at 24 bits) without down-converting it. However, if a CD (the CD Red Book standard is 44.1&nbsp;kHz 16 bit) is to be made from a recording, then doing the initial recording using a sampling rate of 44.1&nbsp;kHz is obviously one approach. Another approach that is usually preferred is to use a higher sample rate and then [[Sample rate conversion|downsample]] to the final format's sample rate. This is usually done as part of the [[Audio mastering|mastering]] process. One advantage to the latter approach is that way a high resolution recording can be released, as well as a CD and/or lossy compressed file such as mp3—all from the same master recording. Beginning in the 1980s, music that was recorded, mixed and mastered digitally was often labelled using the [[SPARS code]] to describe which processes were analog and which were digital. ===Error rectification=== {{Main article|Digital data}} One of the advantages of digital recording over analog recording is its resistance to errors. ==See also== *[[Compact disc]]s use [[Reed-Solomon error correction]] *[[Cyclic redundancy check]] (CRC) *[[Digital audio workstation]] *[[Direct to disk recording]] *[[Magnetic storage]] *[[Multitrack recording]] *[[Parity bit|Parity Computation]] *Many bits are stored on [[RAID|RAID storage systems]] *[[4D Audio Recording system]] ==References== {{Reflist}} {{Audio formats}} {{Music technology}} {{DEFAULTSORT:Digital Recording}} [[Category:Digital audio recording| ]] [[Category:Sound]] [[Category:Video]]'