In digital recording, the analog signal of video or sound is converted into a stream of discrete numbers, representing the changes in air pressure or chroma and luminance values through time; thus making an abstract template for the original sound or moving image.

History

• In 1937, the British scientist Alec Reeves files the first patent describing Pulse-code modulation.

• In 1943, Bell Telephone Laboratories developed the first digital scrambled speech transmission system, SIGSALY.

• In 1957, Max Mathews of Bell developed the process to digitally record sound via computer.

• In 1967, the first digital tape recorder was invented. A 12-bit 30 kHz stereo device using a compander (similar to DBX Noise Reduction) to extend the dynamic range.

• In the 1970s, Thomas Stockham makes the first digital audio recordings using standard computer equipment, as well as developing a digital audio recorder of his own design, the first of its kind to be offered commercially (through Stockham's Soundstream company).

• In 1972, Denon invented the first 8-track reel to reel digital recorder.

• In 1979, the first digital Compact Disc prototype was created as a compromise between sound quality and size of the medium.

• In 1979 the first digitally recorded album of popular music 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 3M Corporation.

• The first digital compact discs marketed in 1982.

• In 1982, New England Digital offers the Sample-to-Disk option on the Synclavier — the first commercial hard disk recording system

• In 1990, digital radio begins in Canada, using the L-Band.

• DVD players begin selling in Japan in 1996.

• In 1998, the first HDTV set went on sale, August 6, for $5,499

• On January 5, 2004, the first HD car radio was sold in Cedar Rapids, Iowa.

Process

Recording

1. The analog signal is transmitted from the input device to an analog to digital converter (ADC).
2. The ADC converts this signal to a series of binary numbers. The quantity of numbers produced per second is called the sample rate.
3. A bundle of wires transmits these numbers into storage onto recording media such as magnetic tape or hard drive or optical drive.

Playback

1. The sequence of numbers is transmitted from storage into a digital to analog converter (DAC), which converts the numbers back to an analog signal.
2. this signal amplified and transmitted to the loudspeakers or video screen.

Getting the bits recorded