Editing Digital audio (section)

==History==
===Coding===
{{Main|Audio coding format|Audio data compression}}

[[Pulse-code modulation]] (PCM) was invented by British scientist [[Alec Reeves]] in 1937.<ref>{{citation |url=http://www.bbc.co.uk/programmes/b00zs7v5 |publisher=BBC |title=Genius Unrecognised |date=2011-03-27 |access-date=2011-03-30}}</ref> In 1950, [[C. Chapin Cutler]] of [[Bell Labs]] filed the patent on [[differential pulse-code modulation]] (DPCM),<ref name="DPCM">{{US patent reference|inventor=C. Chapin Cutler|title=Differential Quantization of Communication Signals|number=2605361|A-Datum=1950-06-29|issue-date=1952-07-29}}</ref> a [[data compression]] algorithm. [[Adaptive DPCM]] (ADPCM) was introduced by P. Cummiskey, [[Nikil Jayant|Nikil S. Jayant]] and [[James L. Flanagan]] at Bell Labs in 1973.<ref>P. Cummiskey, Nikil S. Jayant, and J. L. Flanagan, "Adaptive quantization in differential PCM coding of speech", ''Bell Syst. Tech. J.'', vol. 52, pp. 1105—1118, Sept. 1973</ref><ref>{{cite journal |last1=Cummiskey |first1=P. |last2=Jayant |first2=Nikil S. |last3=Flanagan |first3=J. L. |title=Adaptive quantization in differential PCM coding of speech |journal=The Bell System Technical Journal |date=1973 |volume=52 |issue=7 |pages=1105–1118 |doi=10.1002/j.1538-7305.1973.tb02007.x |issn=0005-8580}}</ref>

[[Perceptual coding]] was first used for [[speech coding]] compression, with [[linear predictive coding]] (LPC).<ref name="Schroeder2014">{{cite book |last1=Schroeder |first1=Manfred R. |title=Acoustics, Information, and Communication: Memorial Volume in Honor of Manfred R. Schroeder |date=2014 |publisher=Springer |isbn=9783319056609 |chapter=Bell Laboratories |page=388 |chapter-url=https://books.google.com/books?id=d9IkBAAAQBAJ&pg=PA388}}</ref> Initial concepts for LPC date back to the work of [[Fumitada Itakura]] ([[Nagoya University]]) and Shuzo Saito ([[Nippon Telegraph and Telephone]]) in 1966.<ref>{{cite journal |last1=Gray |first1=Robert M. |title=A History of Realtime Digital Speech on Packet Networks: Part II of Linear Predictive Coding and the Internet Protocol |journal=Found. Trends Signal Process. |date=2010 |volume=3 |issue=4 |pages=203–303 |doi=10.1561/2000000036 |url=https://ee.stanford.edu/~gray/lpcip.pdf |issn=1932-8346|doi-access=free }}</ref> During the 1970s, [[Bishnu S. Atal]] and [[Manfred R. Schroeder]] at Bell Labs developed a form of LPC called [[adaptive predictive coding]] (APC), a perceptual coding algorithm that exploited the masking properties of the human ear, followed in the early 1980s with the [[code-excited linear prediction]] (CELP) algorithm.<ref name="Schroeder2014"/>

[[Discrete cosine transform]] (DCT) coding, a [[lossy compression]] method first proposed by [[Nasir Ahmed (engineer)|Nasir Ahmed]] in 1972,<ref name="Ahmed">{{cite journal |last=Ahmed |first=Nasir |author-link=N. Ahmed |title=How I Came Up With the Discrete Cosine Transform |journal=[[Digital Signal Processing (journal)|Digital Signal Processing]] |date=January 1991 |volume=1 |issue=1 |pages=4–5 |doi=10.1016/1051-2004(91)90086-Z |bibcode=1991DSP.....1....4A |url=https://www.scribd.com/doc/52879771/DCT-History-How-I-Came-Up-with-the-Discrete-Cosine-Transform|url-access=subscription }}</ref><ref name="DCT">{{cite journal |author1=Nasir Ahmed |author2=T. Natarajan |author3=Kamisetty Ramamohan Rao |journal=IEEE Transactions on Computers|title=Discrete Cosine Transform|volume=C-23|issue=1|pages=90–93|date=January 1974 |doi=10.1109/T-C.1974.223784 |s2cid=149806273 |url=https://www.ic.tu-berlin.de/fileadmin/fg121/Source-Coding_WS12/selected-readings/Ahmed_et_al.__1974.pdf}}</ref> provided the basis for the [[modified discrete cosine transform]] (MDCT), which was developed by J. P. Princen, A. W. Johnson and A. B. Bradley in 1987.<ref>J. P. Princen, A. W. Johnson und A. B. Bradley: ''Subband/transform coding using filter bank designs based on time domain aliasing cancellation'', IEEE Proc. Intl. Conference on Acoustics, Speech, and Signal Processing (ICASSP), 2161–2164, 1987.</ref> The MDCT is the basis for most [[audio coding standards]], such as [[Dolby Digital]] (AC-3),<ref name="Luo">{{cite book |last1=Luo |first1=Fa-Long |title=Mobile Multimedia Broadcasting Standards: Technology and Practice |date=2008 |publisher=[[Springer Science & Business Media]] |isbn=9780387782638 |page=590 |url=https://books.google.com/books?id=l6PovWat8SMC&pg=PA590}}</ref> MP3 ([[MPEG]] Layer III),<ref name="Guckert">{{cite web |last1=Guckert |first1=John |title=The Use of FFT and MDCT in MP3 Audio Compression |url=http://www.math.utah.edu/~gustafso/s2012/2270/web-projects/Guckert-audio-compression-svd-mdct-MP3.pdf |website=[[University of Utah]] |date=Spring 2012 |access-date=14 July 2019}}</ref><ref name="Schroeder2014"/> AAC, [[Windows Media Audio]] (WMA), Opus and [[Vorbis]] ([[Ogg]]).<ref name="Luo"/>

===Recording===
{{Main|Digital recording}}
[[File:Reel to reel Hitachi I (1972).JPG|thumb|upright|Analog [[reel-to-reel tape recorder]]]]
[[File:Sony PCM-7030 of DR 20111102a-crop.jpg|thumb|Sony professional [[digital audio tape]] (DAT) recorder PCM-7030]]
[[File:REAPER_Digital_Audio_Workstation.jpg|thumb|[[Digital audio workstation]]]]

PCM was used in [[telecommunications]] applications long before its first use in commercial broadcast and recording. Commercial digital recording was pioneered in Japan by [[NHK]] and [[Nippon Columbia]] and their [[Denon]] brand, in the 1960s. The first commercial digital recordings were released in 1971.<ref name="Fine"/>

The [[BBC]] also began to experiment with digital audio in the 1960s. By the early 1970s, it had developed a 2-channel recorder, and in 1972 it deployed a digital audio transmission system that linked their broadcast center to their remote transmitters.<ref name="Fine">{{cite journal |url=http://www.aes.org/aeshc/pdf/fine_dawn-of-digital.pdf |access-date=2010-05-02 |journal=ARSC Journal |year=2008 |editor=Barry R. Ashpole |first=Thomas |last=Fine |title=The Dawn of Commercial Digital Recording}}</ref>

The first 16-bit PCM recording in the [[United States]] was made by [[Thomas Stockham]] at the [[Santa Fe Opera]] in 1976, on a [[Soundstream]] recorder. An improved version of the Soundstream system was used to produce several classical recordings by [[Telarc]] in 1978. The [[3M]] digital [[multitrack recorder]] in development at the time was based on BBC technology. The first all-digital album recorded on this machine was [[Ry Cooder]]'s ''[[Bop till You Drop]]'' in 1979. British record label [[Decca Records|Decca]] began development of its own 2-track digital audio recorders in 1978 and released the first European digital recording in 1979.<ref name="Fine"/>

Popular professional digital multitrack recorders produced by Sony/Studer ([[Digital Audio Stationary Head|DASH]]) and Mitsubishi ([[ProDigi]]) in the early 1980s helped to bring about digital recording's acceptance by the major record companies.  Machines for these formats had their own transports built-in as well, using [[reel-to-reel]] tape in either 1/4", 1/2", or 1" widths, with the audio data being recorded to the tape using a multi-track stationary tape head. [[PCM adaptor]]s allowed for stereo digital audio recording on a conventional NTSC or PAL [[video tape recorder]].

The 1982 introduction of the CD by [[Philips]] and [[Sony]] popularized digital audio with consumers.<ref name="Fine"/>

[[ADAT]] became available in the early 1990s, which allowed eight-track [[44,100 Hz|44.1]] or [[48,000 Hz|48&nbsp;kHz]] recording on S-VHS cassettes, and [[DTRS]] performed a similar function with Hi8 tapes.

Formats like ProDigi and DASH were referred to as '''SDAT''' (stationary-head digital audio tape) formats, as opposed to formats like the PCM adaptor-based systems and [[Digital Audio Tape]] (DAT), which were referred to as '''RDAT''' (rotating-head digital audio tape) formats,  due to their helical-scan process of recording.

Like the DAT cassette, ProDigi and DASH machines also accommodated the obligatory 44.1&nbsp;kHz sampling rate, but also 48&nbsp;kHz on all machines, and eventually a 96&nbsp;kHz sampling rate.  They overcame the problems that made typical analog recorders unable to meet the bandwidth (frequency range) demands of digital recording by a combination of higher tape speeds, narrower head gaps used in combination with metal-formulation tapes, and the spreading of data across multiple parallel tracks.

Unlike analog systems, modern [[digital audio workstation]]s and [[audio interface]]s allow as many channels in as many different sampling rates as the computer can effectively run at a single time. [[Avid Audio]] and [[Steinberg]] released the first digital audio workstation software programs in 1989.<ref name=":0">{{Cite journal |last=Reuter |first=Anders |date=2022-03-15 |title=Who let the DAWs Out? The Digital in a New Generation of the Digital Audio Workstation |url=https://www.tandfonline.com/doi/full/10.1080/03007766.2021.1972701 |journal=Popular Music and Society |language=en |volume=45 |issue=2 |pages=113–128 |doi=10.1080/03007766.2021.1972701 |s2cid=242779244 |issn=0300-7766|url-access=subscription }}</ref> Digital audio workstations make multitrack recording and mixing much easier for large projects which would otherwise be difficult with analog equipment.
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===Telephony===
{{Main|Digital telephony}}

The rapid development and wide adoption of PCM [[digital telephony]] was enabled by [[metal–oxide–semiconductor]] (MOS) [[switched capacitor]] (SC) circuit technology, developed in the early 1970s.<ref name="Allstot">{{cite book |last1=Allstot |first1=David J. |chapter=Switched Capacitor Filters |editor-last1=Maloberti |editor-first1=Franco |editor-last2=Davies |editor-first2=Anthony C. |title=A Short History of Circuits and Systems: From Green, Mobile, Pervasive Networking to Big Data Computing |date=2016 |publisher=[[IEEE Circuits and Systems Society]] |isbn=9788793609860 |pages=105–110 |chapter-url=https://ieee-cas.org/sites/default/files/a_short_history_of_circuits_and_systems-_ebook-_web.pdf |access-date=2019-11-29 |archive-date=2021-09-30 |archive-url=https://web.archive.org/web/20210930151716/https://ieee-cas.org/sites/default/files/a_short_history_of_circuits_and_systems-_ebook-_web.pdf |url-status=dead }}</ref> This led to the development of PCM codec-filter chips in the late 1970s.<ref name="Allstot"/><ref name="Gibson26">{{cite book |last1=Floyd |first1=Michael D. |last2=Hillman |first2=Garth D. |chapter=Pulse-Code Modulation Codec-Filters |title=The Communications Handbook |edition=2nd |date=8 October 2018 |orig-year=1st pub. 2000 |pages=26-1, 26-2, 26-3 |publisher=[[CRC Press]] |isbn=9781420041163 |chapter-url=https://books.google.com/books?id=Tokk5bZxB0MC&pg=SA26-PA1}}</ref> The [[silicon-gate]] [[CMOS]] (complementary MOS) PCM codec-filter chip, developed by [[David A. Hodges]] and W.C. Black in 1980,<ref name="Allstot"/> has since been the industry standard for digital telephony.<ref name="Allstot"/><ref name="Gibson26"/> By the 1990s, [[telecommunication network]]s such as the [[public switched telephone network]] (PSTN) had been largely [[digitized]] with [[VLSI]] (very [[large-scale integration]]) CMOS PCM codec-filters, widely used in [[electronic switching system]]s for [[telephone exchanges]], user-end [[modems]] and a range of [[digital transmission]] applications such as the [[integrated services digital network]] (ISDN), [[cordless telephones]] and [[cell phones]].<ref name="Gibson26"/>