
In digital recording, an
audio or
video signal
Video is an electronic medium for the recording, copying, playback, broadcasting, and display of moving visual media. Video was first developed for mechanical television systems, which were quickly replaced by cathode-ray tube (CRT) ...
is converted into a stream of
discrete numbers representing the changes over time in
air pressure
Atmospheric pressure, also known as air pressure or barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The Standard atmosphere (unit), standard atmosphere (symbol: atm) is a unit of pressure defined as , whi ...
for audio, or
chroma and
luminance values for video. This number stream is saved to a storage device. To play back a digital recording, the numbers are retrieved and converted back into their original
analog audio or video forms so that they can be heard or seen.
In a properly matched
analog-to-digital converter (ADC) and
digital-to-analog converter (DAC) pair, the analog signal is accurately reconstructed, within the constraints of the
Nyquist–Shannon sampling theorem, which dictates the
sampling rate and
quantization error dependent on the
audio or
video bit depth. Because the signal is stored digitally, assuming proper
error detection and correction, the recording is not degraded by copying, storage or interference.
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). On November 22, 1939, Reeves files also in the US. It was first proposed as a
telephony
Telephony ( ) is the field of technology involving the development, application, and deployment of telecommunications services for the purpose of electronic transmission of voice, fax, or data, between distant parties. The history of telephony is ...
technology.
*1943:
Bell Telephone Laboratories develops the first PCM-based digital scrambled speech transmission system,
SIGSALY, in response to German interception of military telephone traffic during
World War II
World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...
. The twelve transmission points were retired after the war.
*June 1950:
Differential pulse-code modulation (DPCM) developed by
C. Chapin Cutler at Bell Labs.
*1957:
Max Mathews of Bell Labs recorded the first computer-generated music, a 17-second piece called "The Silver Scale" composed by his co-worker Newman Guttman.
*1967: The first commercial PCM encoder (
monaural) was developed by
NHK
, also known by its Romanization of Japanese, romanized initialism NHK, is a Japanese public broadcasting, public broadcaster. It is a statutory corporation funded by viewers' payments of a television licence, television license fee.
NHK ope ...
's research facilities in Japan.
The 30 kHz 12-bit device used a
compander (similar to
DBX Noise Reduction) to extend the dynamic range, and stored the signals on a
video tape recorder
A video tape recorder (VTR) is a tape recorder designed to record and playback video and audio signal, audio material from magnetic tape. The early VTRs were open-reel devices that record on individual reels of 2-inch-wide (5.08 cm) tape. ...
.
*1969: NHK expands the PCM encoder's capabilities to two-channel
stereo and 32 kHz 13-bit resolution.
*1969: The
charge-coupled device
A charge-coupled device (CCD) is an integrated circuit containing an array of linked, or coupled, capacitors. Under the control of an external circuit, each capacitor can transfer its electric charge to a neighboring capacitor. CCD sensors are a ...
, the first image sensor used in digital imaging, invented by
Willard S. Boyle and
George E. Smith at Bell Labs, based on
MOS capacitor technology.
*1970:
James Russell patents the first digital-to-optical recording and playback system, which would later lead to the
Compact Disc
The compact disc (CD) is a Digital media, digital optical disc data storage format co-developed by Philips and Sony to store and play digital audio recordings. It employs the Compact Disc Digital Audio (CD-DA) standard and was capable of hol ...
.
*January 1971: Using NHK's experimental PCM recording system, Dr. Takeaki Anazawa, an engineer at
Denon, records the world's first commercial digital recordings, ''The World Of Stomu Yamash'ta 1 & 2'' by
Stomu Yamash'ta (January 11, 1971)
and ''Something'' by
Steve Marcus & Jiro Inagaki (January 25, 1971). Both had to be recorded live, without edits. Marcus is released first (on LP, in February 1972), making it the first released digital recording. On January 27 Yamash'ta records ''Metempsychosis'' in the Nippon Columbia studio, Tokyo, with percussion and a brass section.
*1972: Using lessons learned from the NHK encoder,
Denon unveils a desk-sized 8-channel PCM encoder, the DN-023R, which uses 47.25 kHz 13-bit PCM resolution and 4-head open reel broadcast
video tape recorder
A video tape recorder (VTR) is a tape recorder designed to record and playback video and audio signal, audio material from magnetic tape. The early VTRs were open-reel devices that record on individual reels of 2-inch-wide (5.08 cm) tape. ...
.
The first recording with this new system is the
Smetana Quartet performing
Mozart
Wolfgang Amadeus Mozart (27 January 1756 – 5 December 1791) was a prolific and influential composer of the Classical period (music), Classical period. Despite his short life, his rapid pace of composition and proficiency from an early age ...
's ''String Quartets
K.458 and
K.421'', recorded in Tokyo April 24–26 and released that October. At least six other Denon-recorded digital
LP record
The LP (from long playing or long play) is an Analog recording, analog sound storage medium, specifically a phonograph record format characterized by: a speed of revolutions per minute, rpm; a 12- or 10-inch (30- or 25-cm) diameter; use ...
s are released in October, including jazz, classical and traditional Japanese music.
*1973:
Adaptive differential pulse-code modulation (ADPCM) developed by P. Cummiskey,
Nikil Jayant and
James L. Flanagan at Bell Labs.
*December 2–3, 1974: The
Paillard Chamber Orchestra records the first digital recording outside Japan, in
Paris
Paris () is the Capital city, capital and List of communes in France with over 20,000 inhabitants, largest city of France. With an estimated population of 2,048,472 residents in January 2025 in an area of more than , Paris is the List of ci ...
'
Notre Dame Cathedral, using Denon's newly developed second-generation compact DN-023RA.
Bach's "
The Musical Offering" (BWV 1079) is released on LP May 1975.
*December 12–19, 1974:
Helmuth Rilling records three
Bach organ works inside the Gedächtniskirche,
Stuttgart
Stuttgart (; ; Swabian German, Swabian: ; Alemannic German, Alemannic: ; Italian language, Italian: ; ) is the capital city, capital and List of cities in Baden-Württemberg by population, largest city of the States of Germany, German state of ...
Germany using the DN-023RA. Between 1974 and 1977 over 250 PCM recordings are made by Denon, the majority recorded in Japan.
*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.
Between 1977 and 1980 a total of eighteen 4-channel 50 kHz 16-bit units were manufactured, of which seven were sold at about US$150,000 () each. Over 200 recordings were made on his equipment, almost as many as the Denon PCM.
*1976: The prototype
Soundstream 37.5 kHz, 16-bit, 2-channel recorder
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 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
AES Convention in New York, but never commercially released.
*January 1977: Denon develops a smaller fully-portable PCM recording system, the DN-034R. Like the DN-023R and DN-023RA it records 8 channels at 47.25 kHz on a 2-inch video tape recorder (VTR) running at 38.1 cm/s, but it uses 14-bits "with emphasis, making it equivalent to 15.5 bits," yielding 89 dB
signal-to-noise ratio. It also allowed for
overdubbing
Overdubbing (also known as layering) is a technique used in audio recording in which audio Music track, tracks that have been pre-recorded are then played back and monitored, while simultaneously recording new, doubled, or augmented tracks onto o ...
for the first time with the use of a second VTR, crucial for professional recording.
*September 1977: Sony introduces the PCM-1 Audio Unit ($4400 street price ) (44.056 kHz, 14-bit), the first consumer PCM encoder. It required the use of a home video tape recorder for storage.
*November 4–7, 1977:
3M demonstrates a prototype 2-channel 50.4 kHz 16-bit digital recorder running on 1-inch tape at at the New York
AES Convention.
As no true 16-bit converters were available, it combined separate 12-bit and 8-bit converters to create 16-bit performance.
*November 28, 1977: Denon brings their DN-034R to
New York City
New York, often called New York City (NYC), is the most populous city in the United States, located at the southern tip of New York State on one of the world's largest natural harbors. The city comprises five boroughs, each coextensive w ...
's Sound Ideas Studios and records
Archie Shepp's ''On Green Dolphin Street'', making it America's first digitally-recorded commercial album.
The following two days, November 29–30,
Frank Foster records ''
Manhattan Fever'' which is released April 1978.
Five other jazz albums are recorded with the DN-034R in New York before it returns to Japan in December.
*February 1978: Soundstream's first commercial release, ''
Diahann Carroll With the
Duke Ellington
Edward Kennedy "Duke" Ellington (April 29, 1899 – May 24, 1974) was an American Jazz piano, jazz pianist, composer, and leader of his eponymous Big band, jazz orchestra from 1924 through the rest of his life.
Born and raised in Washington, D ...
Orchestra Under The Direction Of
Mercer Ellington – A Tribute To
Ethel Waters'', is recorded.
*March 1978: Sony introduces the professional-grade
PCM-1600 at a list price of US$40,000 () 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.
*April 4–5, 1978:
Telarc uses Soundstream's PCM system to record
Frederick Fennell and his
Cleveland Symphonic Winds 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.
*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 50.4 kHz digital recorder running in the background. There is some disagreement,
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. In 1984 the session is re-released on
Compact Disc
The compact disc (CD) is a Digital media, digital optical disc data storage format co-developed by Philips and Sony to store and play digital audio recordings. It employs the Compact Disc Digital Audio (CD-DA) standard and was capable of hol ...
by ProArte. This recording was nominated for three
Grammy Award
The Grammy Awards, stylized as GRAMMY, and often referred to as The Grammys, are awards presented by The Recording Academy of the United States to recognize outstanding achievements in music. They are regarded by many as the most prestigious ...
s, winning "
Best Chamber Music Performance" (1980),
making it the first digital recording to win a Grammy.
*Early June 1978:
Sound 80 records ''
Flim and the BB's'' debut self-titled album as another
direct to disc recording
Direct-to-disc recording refers to sound recording methods that bypass the use of magnetic tape recording and record audio directly onto analog disc masters.
Professional analog sound recording
Most sound recordings for gramophone records, recor ...
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 ("very bulky and finicky") 3M digital recorder is disassembled, rendering the non-standard master tape unplayable. Therefore, no
Compact Disc
The compact disc (CD) is a Digital media, digital optical disc data storage format co-developed by Philips and Sony to store and play digital audio recordings. It employs the Compact Disc Digital Audio (CD-DA) standard and was capable of hol ...
release is possible. The compact disc release of the Saint Paul Chamber Orchestra, which used the same machine, is unexplained.
*March 8, 1979: The first prototype
Compact Disc
The compact disc (CD) is a Digital media, digital optical disc data storage format co-developed by Philips and Sony to store and play digital audio recordings. It employs the Compact Disc Digital Audio (CD-DA) standard and was capable of hol ...
player is demonstrated by
Philips in
Eindhoven
Eindhoven ( ; ) is a city and List of municipalities of the Netherlands, municipality of the Netherlands, located in the southern Provinces of the Netherlands, province of North Brabant, of which it is the largest municipality, and is also locat ...
,
Netherlands
, Terminology of the Low Countries, informally Holland, is a country in Northwestern Europe, with Caribbean Netherlands, overseas territories in the Caribbean. It is the largest of the four constituent countries of the Kingdom of the Nether ...
.
Prototype CDs played on the unit were a pressing of
Antonio Vivaldi's ''
Le quattro stagioni'' played by
Vittorio Negri and the
Kammerorchester Berlin (Philips 9500 100, recorded analog 1976), and
Joseph Haydn
Franz Joseph Haydn ( ; ; 31 March 173231 May 1809) was an Austrian composer of the Classical period (music), Classical period. He was instrumental in the development of chamber music such as the string quartet and piano trio. His contributions ...
's ''String Quartet No. 31''(?).
A third prototype disc, on
Archiv Produktion is pictured but the details are not legible. The text indicates it might be
Franz Schubert
Franz Peter Schubert (; ; 31 January 179719 November 1828) was an Austrian composer of the late Classical period (music), Classical and early Romantic music, Romantic eras. Despite his short life, Schubert left behind a List of compositions ...
's ''
Unfinished Symphony''.
Herbert von Karajan and the
Berlin Philharmonic's recording of
Richard Strauss's ''
Eine Alpensinfonie'' is also mentioned as a contender for earliest test pressing of a CD, but it was not recorded until December 1–3, 1980.
*July 11, 1979: The first U.S.-recorded digitally-recorded LP of
popular music
Popular music is music with wide appeal that is typically distributed to large audiences through the music industry. These forms and styles can be enjoyed and performed by people with little or no musical training.Popular Music. (2015). ''Fun ...
(with vocals), ''
Bop Till You Drop'' by guitarist
Ry Cooder, was released by
Warner Bros. Records. The album was recorded in
Los Angeles
Los Angeles, often referred to by its initials L.A., is the List of municipalities in California, most populous city in the U.S. state of California, and the commercial, Financial District, Los Angeles, financial, and Culture of Los Angeles, ...
on a 32-track digital machine built by the
3M corporation.
*August 27, 1979:
Giorgio Moroder
Giovanni Giorgio Moroder (, ; born 26 April 1940) is an Italian composer and music producer. Dubbed the "Honorific nicknames in popular music, Father of Disco", Moroder is credited with pioneering Euro disco and electronic dance music. His work ...
's ''
E=MC²'' is released, the first electronic live-to-digital LP recorded on Soundstream PCM.
*September 4, 1979: Scoring begins for Star Trek The Motion Picture soundtrack, recorded to
multitrack analog, mastered to digital stereo tape for LP release to coincide with film debut December 6, 1979.
*October 12, 1979:
Fleetwood Mac
Fleetwood Mac are a British-American Rock music, rock band formed in London in 1967 by the singer and guitarist Peter Green (musician), Peter Green. Green named the band by combining the surnames of the drummer, Mick Fleetwood, and the bassis ...
's ''
Tusk'' is released on LP. It, and ''
Live'', December 8, 1980, were mastered on the Soundstream PCM from analog multi-tracks.
*October 30, 1979:
Stevie Wonder
Stevland Hardaway Morris (; Judkins; born May 13, 1950), known professionally as Stevie Wonder, is an American and Ghanaian singer-songwriter, musician, and record producer. He is regarded as one of the most influential musicians of the 20th c ...
releases his
soundtrack album, ''
Journey Through "The Secret Life of Plants"'' recorded onto
U-matic video tapes using a Sony PCM-1600 digital adapter, and assembled into album form with a digital editing controller.
*December 1, 1979: The Grammy Award-winning self-titled ''
Christopher Cross'' album is released. Cross' album becomes the first digitally recorded album to chart (recorded on the 3M system) in the United States, eventually winning 5 Grammys. Digital recording is now mainstream.
*1980: The
Red Book standard (44.1 kHz, 16-bit) is established for
Compact Disc Digital Audio
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 compact discs. The standard is defined in the '' Red Book'' technical specifications, which is why t ...
.
*1980:
Mitsubishi Electric introduces the X-80
ProDigi open reel 1/4" tape 50.4 kHz 16-bit digital recorder ($5000 ). Only 200 are sold worldwide.
*1980: Soundstream merges with Digital Recording Corporation, becoming DRC/Soundstream, to develop and market 50 kHz PCM recording to an optical card. This is subsequently eclipsed by the rise of the 44.1 kHz
Compact Disc
The compact disc (CD) is a Digital media, digital optical disc data storage format co-developed by Philips and Sony to store and play digital audio recordings. It employs the Compact Disc Digital Audio (CD-DA) standard and was capable of hol ...
and the company is out of business after 1983.
*1981: Sony releases the PCM-F1 Digital Audio Processor ($1900 ) (44.056 kHz, 16-bit) and matching SL-2000
Betamax VCR ($700 ) as a complete affordable portable (with optional batteries) home digital recording system
*1981: Technics releases the SV-P100 digital audio recorder suitable for both professional (digital mastering) and consumer (home use) recording. It used PCM 14-bit recording on a VHS format cassette tape, resulting in an up to 3 hours programme of 2-channel stereo recording.
*1982: Sony releases the PCM-501ES
PCM adaptor (44.1 kHz, 16-bit) ($895 list price) which is used with an external
VHS or
Betamax video recorder.
*August 17, 1982:
Claudio Arrau's March 1979 analog recording of
Frederic Chopin waltzes (Philips 400 025) becomes the first classical Compact Disc ever commercially manufactured.
It is made by the Philips plant in
Langenhagen,
Hanover Region Germany
Germany, officially the Federal Republic of Germany, is a country in Central Europe. It lies between the Baltic Sea and the North Sea to the north and the Alps to the south. Its sixteen States of Germany, constituent states have a total popu ...
. Arrau himself was invited to press the button to start the manufacture. This CD was not actually released until 1983 so it presumably ran into manufacturing problems like the ABBA release (below).
*August 17, 1982: The first popular Compact Disc ever manufactured,
ABBA
ABBA ( ) were a Swedish pop group formed in Stockholm in 1972 by Agnetha Fältskog, Björn Ulvaeus, Benny Andersson, and Anni-Frid Lyngstad. They are one of the most popular and successful musical groups of all time, and are one of the List ...
's 1981 album ''
The Visitors'' (selected because it was "mostly digitally recorded") is produced at the same plant. However, due to production problems with it the third version didn't actually hit stores until March 1983.
*September 5, 1982:
Peter Gabriel releases his fourth studio album (titled
''Security'' in North America and ''Peter Gabriel IV'' elsewhere). When released on CD in October 1984 it becomes the first full-digital
DDD release. It was recorded on
Sony
is a Japanese multinational conglomerate (company), conglomerate headquartered at Sony City in Minato, Tokyo, Japan. The Sony Group encompasses various businesses, including Sony Corporation (electronics), Sony Semiconductor Solutions (i ...
's Mobile One digital studio and mixed to a Sony PCM-1610.
*October 1, 1982: The first
compact disc
The compact disc (CD) is a Digital media, digital optical disc data storage format co-developed by Philips and Sony to store and play digital audio recordings. It employs the Compact Disc Digital Audio (CD-DA) standard and was capable of hol ...
players are marketed by Sony (CDP-101, $900 ) and Philips (CD-100, $700 ).
*October 1, 1982:
Billy Joel
William Martin Joel (born May 9, 1949) is an American singer, songwriter, and pianist. Nicknamed the "Honorific nicknames in popular music, Piano Man" after his Signature song, signature 1973 song Piano Man (song), of the same name, Joel has ha ...
's analog-recorded ''
52nd Street'' becomes the first CD to hit the market in Japan, beating out ABBA's ''
The Visitors'' and Claudio Arrau's Chopin Waltzes. Forty-nine other CDs are released in Japan on the same day including
Toto's ''
Turn Back'',
Pink Floyd
Pink Floyd are an English Rock music, rock band formed in London in 1965. Gaining an early following as one of the first British psychedelic music, psychedelic groups, they were distinguished by their extended compositions, sonic experiments ...
's ''
Wish You Were Here'' and
Michael Jackson
Michael Joseph Jackson (August 29, 1958 – June 25, 2009) was an American singer, songwriter, dancer, and philanthropist. Dubbed the "King of Pop", he is regarded as Cultural impact of Michael Jackson, one of the most culturally significan ...
's ''
Off the Wall''.
*October 1982:
New England Digital offers the Sample-to-Disk
hard disk recorder option on the
Synclavier
The Synclavier is an early digital synthesizer, polyphonic digital sampling system, and music workstation manufactured by New England Digital Corporation of Norwich, Vermont. It was produced in various forms from the late 1970s into the ea ...
, the first commercial
hard disk recording system.
*November 26–28, 1982:
Flim & the BB's record their second studio album, ''Tricycle''. Released in early 1983, it becomes the first non-classical fully digital CD to be released. (Later given a
SPARS code of DD).
*March 2, 1983: CD players and 16 CDs from
CBS Records are introduced in the United States.
*September 1984:
Bruce Springsteen's ''
Born in the U.S.A.'' becomes the first US-manufactured CD to be released.
*12 November 1984: American singer
Madonna
Madonna Louise Ciccone ( ; born August 16, 1958) is an American singer, songwriter, record producer, and actress. Referred to as the "Queen of Pop", she has been recognized for her continual reinvention and versatility in music production, ...
's second studio album ''
Like a Virgin'' is released. It became the first digitally-recorded album that topped the
''Billboard'' 200 chart.
*13 May 1985: English rock band
Dire Straits' fifth studio album ''
Brothers in Arms'' is released. It became the best-selling digitally-recorded album of the 80s, and the first album whose CDs' sales outsold LPs'.
*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
Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, making it the world's List of coun ...
, using the
L-Band.
*1991: Alesis Digital Audio Tape (
ADAT) is a tape format used for simultaneously recording eight tracks of
digital audio
Digital audio is a representation of sound recorded in, or converted into, digital signal (signal processing), digital form. In digital audio, the sound wave of the audio signal is typically encoded as numerical sampling (signal processing), ...
at once, onto
Super VHS magnetic tape – a format similar to that used by consumer
VCRs. The product was announced in January 1991 at the
NAMM Show
The NAMM Show is an annual trade show in the United States organized by the National Association of Music Merchants (NAMM), which describes it as "the industry’s largest stage, uniting the global music, sound and entertainment technology commun ...
. The first ADAT recorders shipped over a year later in February or March 1992.
*1993: Random Access Digital Audio Recorder (
RADAR
Radar is a system that uses radio waves to determine the distance ('' ranging''), direction ( azimuth and elevation angles), and radial velocity of objects relative to the site. It is a radiodetermination method used to detect and track ...
) is the first single box device used for simultaneously recording 24 tracks of
digital audio
Digital audio is a representation of sound recorded in, or converted into, digital signal (signal processing), digital form. In digital audio, the sound wave of the audio signal is typically encoded as numerical sampling (signal processing), ...
at once, onto hard disk drives. The product, manufactured by
Creation Technologies was announced in October 1993 at the
AES convention in New York. The first RADAR recorders shipped in August 1994.
*1996:
DVD players begin selling in Japan.
*1999:
Ricky Martin
Enrique Martin Morales (born December 24, 1971), known professionally as Ricky Martin, is a Puerto Rican singer, songwriter and actor. He is known for his musical versatility, with his Ricky Martin albums discography, discography incorporati ...
's "
Livin' la Vida Loca" becomes the first No. 1 single to be recorded, edited, and mixed fully within a
digital audio workstation
A digital audio workstation (DAW ) is an electronic device or application software used for Sound recording and reproduction, recording, editing and producing audio files. DAWs come in a wide variety of configurations from a single software pr ...
. Produced by
Charles Dye and
Desmond Child using
Pro Tools.
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 measurement point. The longer the word length the more precise the representation of the original audio wave level.
# The frequency at which the ADC measures the level of the analog wave is called the
sample rate or sampling rate. 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
magnetic tape
Magnetic tape is a medium for magnetic storage made of a thin, magnetizable coating on a long, narrow strip of plastic film. It was developed in Germany in 1928, based on the earlier magnetic wire recording from Denmark. Devices that use magnetic ...
, a
hard drive
A hard disk drive (HDD), hard disk, hard drive, or fixed disk is an electro-mechanical data storage device that stores and retrieves digital data using magnetic storage with one or more rigid rapidly rotating hard disk drive platter, pla ...
,
optical drive or in
solid state memory.
Playback
# The sequence of numbers is transmitted from storage into a
digital-to-analog converter (DAC)
# The DAC converts the numbers back to an analog signal by sticking together the level information stored in each digital sample, thus rebuilding the original analog waveform.
# This signal is amplified and transmitted to the
loudspeakers.
Recording of bits
Techniques to record to commercial media
For
digital cassettes, the
tape head moves as well as the tape, typically in a
helical scan configuration, in order to maintain a high enough speed to keep the bits at a manageable size.
For
optical disc recording technologies such as
CD-R
CD-R (Compact disc-recordable) is a digital media, digital optical disc data storage device, storage format. A CD-R disc is a compact disc that can only be Write once read many, written once and read arbitrarily many times.
CD-R discs (CD-Rs) ...
, a
laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word ''laser'' originated as an acronym for light amplification by stimulated emission of radi ...
is used to alter the optical properties of the dye layer of the medium. A weaker laser is used to read these patterns.
Performance parameters
Word size
The
number of bits used to represent an audio signal directly affects the resulting
noise
Noise is sound, chiefly unwanted, unintentional, or harmful sound considered unpleasant, loud, or disruptive to mental or hearing faculties. From a physics standpoint, there is no distinction between noise and desired sound, as both are vibrat ...
or
distortion
In signal processing, distortion is the alteration of the original shape (or other characteristic) of a signal. In communications and electronics it means the alteration of the waveform of an information-bearing signal, such as an audio signal ...
in a recording.
Sample rate
As stated by the
Nyquist–Shannon sampling theorem, to prevent
aliasing, the audio signal must be sampled at a rate at least twice that of the highest frequency component in the signal. For music-quality audio,
44.1 and 48 kHz sampling rates are the most common.
Master recording may be done at a higher sampling rate (i.e. 88.2, 96, 176.4 or 192 kHz). High-resolution PCM recordings have been released on
DVD-Audio (also known as DVD-A),
DualDisc (utilizing the DVD-Audio layer), or
High Fidelity Pure Audio on Blu-ray. In addition, it is possible to release a high-resolution recording as either an uncompressed
WAV or lossless compressed
FLAC file (usually at 24 bits) without
down-converting it. There remains controversy about whether higher sampling rates provide any verifiable benefit to the consumer product.
When a
Compact Disc
The compact disc (CD) is a Digital media, digital optical disc data storage format co-developed by Philips and Sony to store and play digital audio recordings. It employs the Compact Disc Digital Audio (CD-DA) standard and was capable of hol ...
(the
CD Red Book standard is 44.1 kHz 16 bit) is to be made from a high-res recording, the recording must be
down-converted to 44.1 kHz. This is done as part of the
mastering process.
Beginning in the 1980s, music that was recorded, mixed or mastered digitally was often labeled using the
SPARS code to describe which processes were analog and which were digital. Since digital recording has become near-ubiquitous the SPARS codes are now rarely used.
Error rectification
One of the advantages of digital recording over analog recording is its resistance to errors. Once the signal is in the digital format, it is not subject to
generation loss from copying. Instead of the gradual degradation experienced with analog media, digital media is subject to a
cliff effect.
Examples of digital recording devices
*
Camcorder
*
Data logger
*
Dictation machine
*
Digital video recorder
See also
*
Phone surveillance
Notes
References
{{DEFAULTSORT:Digital Recording
Sound
Video
Sound recording