In digital recording, the analog signal of a motion-picture/sound is converted into a stream of discrete numbers, representing the changes in air pressure (chroma and luminance values in case of video) through time; thus making an abstract template for the original sound or moving image. Analog recording is the first way humans were able to store sounds for later playback. ... Film refers to the celluloid media on which movies are printed. ... This article is about audible acoustic waves. ... It has been suggested that this article or section be merged into Fixed-point arithmetic. ... Air pressure can refer to: Atmospheric pressure, the pressure of air environmentally Pressure of air in a system Category: ... Color is an important part of the visual arts. ... Luminance (also called luminosity) is a photometric measure of the density of luminous intensity in a given direction. ... Look up time in Wiktionary, the free dictionary. ...

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.

• The first digital compact discs marketed in 1982.

• In 1984, AMS launches the AudioFile — the world’s 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.

Year 1937 (MCMXXXVII) was a common year starting on Friday (link will display the full calendar) of the Gregorian calendar. ... Alec Reeves was one the 20th Centurys greatest, but least conventional, scientists. ... PCM redirects here. ... Year 1943 (MCMXLIII) was a common year starting on Friday (the link will display full 1943 calendar) of the Gregorian calendar. ... Bell Laboratories (also known as Bell Labs and formerly known as AT&T Bell Laboratories and Bell Telephone Laboratories) was the main research and development arm of the United States Bell System. ... SIGSALY exhibit at the National Cryptologic Museum In cryptography, SIGSALY (also Green Hornet) was a telephone scrambler used in World War II for the highest-level Allied communications. ... Year 1957 (MCMLVII) was a common year starting on Tuesday (link displays the 1957 Gregorian calendar). ... Max Vernon Mathews was born in Columbus, Nebraska, on November 13, 1926. ... Methods and media for sound recording are varied and have undergone significant changes between the first time sound was actually recorded for later playback until now. ... This article is about the machine. ... Year 1967 (MCMLXVII) was a common year starting on Sunday (link will display full calendar) of the 1967 Gregorian calendar. ... A waveform before and after the compression stage of companding In telecommunication, signal processing, and thermodynamics, companding (occasionally called compansion) is a method of reducing the effects of a channel with limited dynamic range. ... Thomas Greenway Stockham, (December 22, 1933-January 6, 2004) was an American scientist who developed the first practical digital audio recording system, and pioneered techniques for digital audio recording and processing as well. ... Soundstream Inc. ... Year 1972 (MCMLXXII) was a leap year starting on Saturday (link will display full calendar) of the Gregorian calendar. ... A Sony TC-630 reel-to-reel recorder, once a common household object. ... Also: 1979 by Smashing Pumpkins. ... CD redirects here. ... CD redirects here. ... Year 1982 (MCMLXXXII) was a common year starting on Friday (link displays the 1982 Gregorian calendar). ... Year 1990 (MCMXC) was a common year starting on Monday (link displays the 1990 Gregorian calendar). ... This article needs to be cleaned up to conform to a higher standard of quality. ... L band (20-cm radar long-band) is a portion of the microwave band of the electromagnetic spectrum ranging roughly from 0. ... The inside of a DVD player A DVD player is a device not only playing discs produced under the DVD Video standard but also playing discs under the standard of DVD Audio. ... Year 1996 (MCMXCVI) was a leap year starting on Monday (link will display full 1996 Gregorian calendar). ... Year 1998 (MCMXCVIII) was a common year starting on Thursday (link will display full 1998 Gregorian calendar). ... High-definition television (HDTV) is a digital television broadcasting system with greater resolution than traditional television systems (NTSC, SECAM, PAL). ... Year 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... Nickname: Location in the State of Iowa Coordinates: , Country State County Linn Incorporated 1849 Government  - Mayor Kay Halloran Area  - City 166. ...

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 count of the numbers produced per second is called the sample rate.
3. A bundle of wires transmits these numbers into storage. (Such as a hard drive or compact disc burner).

Playback An input device is a hardware mechanism that transforms information in the external world for consumption by a computer. ... This article or section should include material from AD converters In electronics, an analog-to-digital converter (abbreviated ADC, A/D, or A to D) is a device that converts continuous signals to discrete digital numbers. ... The binary or base-two numeral system is a system for representing numbers in which a radix of two is used; that is, each digit in a binary numeral may have either of two different values. ... The sampling frequency or sampling rate defines the number of samples per second taken from a continuous signal to make a discrete signal. ... A wire is a single, usually cylindrical, elongated strand of drawn metal. ... Typical hard drives of the mid-1990s. ...

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 loudspeaker.

In electronics, a digital-to-analog converter (DAC or D-to-A) is a device for converting a digital (usually binary) code to an analogue signal (current, voltage or charges). ... For the Marty Friedman album, see Loudspeaker (album) An inexpensive low fidelity 3. ...

Getting the bits recorded

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 a two channels song 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. Digital audio casette formats introduced to the audio professionals and consumer markets: Digital Audio Tape known more commonly as just DAT which had some success as a audio storage format among professionals before the prices of hard drives dropped and the capacities soared in the late 90s. ...

For CDs or DVDs, 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. For other uses, see Laser (disambiguation). ...

Concerns with digital recording

Word Size

The number of bits used to represent a single audio wave (the word size) directly affects the distortion of a signal. Increasing a sample's word length by one bit doubles its possible values, likewise increasing the potential accuracy of each sample and the fidelity of the recording to the original. 24-bit recording is generally considered a current practical limit as this word length allows a signal-to-noise ratio exceeding that of most analog circuitry, which by necessity must be used in at least two points in the recording/playback chain. This article is about the unit of information. ... This article is about compression waves. ... In computer hardware terminology, word size (word length) is the number of bits that a CPU can process at one time (the word). ... For other uses, see Distortion (disambiguation). ... Signal-to-noise ratio (often abbreviated SNR or S/N) is an electrical engineering concept defined as the ratio of a signal power to the noise power corrupting the signal. ...

Sample rate

The sample rate is even more important a consideration than the word size. If the sample rate is too low, the sampled signal cannot be reconstructed to the original sound signal. Hence the output will be different to the input. The process of under sampling results in aliasing whereby the high frequency components of the sound wave are represented as being lower than they should be. This causes the output wave shape to be severely altered. Properly sampled image of brick wall. ... Output is the term denoting either an exit or changes which exits a system and which activate/modify a process. ...

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. The Nyquist-Shannon sampling theorem is the fundamental theorem in the field of information theory, in particular telecommunications. ...

Error Rectification

Main article: digital

One of the great advantages of digital recording over analog recording is its resistance to errors. Since these bits are physically extremely small, some are bound to be damaged during the process of recording or using them. With analog recording techniques, any amount of damage is irreversible. As you use it, the increasing damage causes the noise to get worse and worse. For other uses, see Digital (disambiguation). ...

With digital recording techniques, small amounts of damage are completely irrelevant. When a crisp bump meant to represent a "1" gets a small notch knocked off or becomes worn, it's still very easy to distinguish it from a "0". Even when one particualar "1" bump is so well worn that it becomes uncorrectable from a "0", there are error correction schemes that can look for the lost information and release it. Here are some methods used to circumvent losing any data even when particular pieces of a work are completely ruined. For other uses, see Data (disambiguation). ...

• Compact discs use Reed-Solomon error correction
• Many bits are stored on RAID storage systems.