digital recording

In digital recording, an audio or video signal is converted into a stream of discrete numbers representing the changes over time in air pressure 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 per the constraints of the Nyquist–Shannon sampling theorem dependent on 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 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. 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 develops the process to digitally record sound on a computer.
*1967: The first monaural PCM encoder was developed by NHK'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.
*1969: NHK expands the PCM encoder's capabilities to two-channel stereo and 32 kHz 13-bit resolution.
*1969: The charge-coupled device, 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.
*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 (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 the first 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. The first recording with this new system is the Smetana Quartet performing Mozart'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 records 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' Notre Dame Cathedral, using Denon's DN-023R. 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 Germany using the DN-023R.
*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 half of all digital classical recordings made in the 1970s.
*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.
*1977: Denon develops the smaller portable PCM recording system, the DN-034R. Like the DN-023R it records 8 channels at 47.25 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.
*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'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.
*January 1978: Soundstream's first commercial release, ''Diahann Carroll With the Duke Ellington Orchestra Under The Direction Of Mercer Ellington – A Tribute To Ethel Waters'', appears
*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 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.
*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 by ProArte. This recording was nominated for three Grammy Awards, 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 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 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 player is demonstrated by Philips in Eindhoven

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