An audio codec is a device or computer program capable of encoding or decoding a digital data stream (a

codec A codec is a device or computer program In imperative programming, a computer program is a sequence of instructions in a programming language that a computer can execute or interpret. In declarative programming, a ''computer program'' is a Set ...

) that encodes or decodes audio. In software, an audio codec is a computer program implementing an algorithm that compresses and decompresses digital audio data according to a given audio file or streaming media

audio coding format An audio coding format (or sometimes audio compression format) is a content representation format for storage or transmission of digital audio Digital audio is a representation of sound recorded in, or converted into, Digital signal (signal p ...

. The objective of the algorithm is to represent the high-fidelity audio signal with minimum number of bits while retaining quality. This can effectively reduce the storage space and the

bandwidth Bandwidth commonly refers to: * Bandwidth (signal processing) or ''analog bandwidth'', ''frequency bandwidth'', or ''radio bandwidth'', a measure of the width of a frequency range * Bandwidth (computing), the rate of data transfer, bit rate or thr ...

required for transmission of the stored audio file. Most software codecs are implemented as

libraries A library is a collection of materials, books or media that are easily accessible for use and not just for display purposes. It is responsible for housing updated information in order to meet the user's needs on a daily basis. A library provi ...

which interface to one or more multimedia players. Most modern audio compression algorithms are based on

modified discrete cosine transform The modified discrete cosine transform (MDCT) is a transform based on the type-IV discrete cosine transform A discrete cosine transform (DCT) expresses a finite sequence of data points in terms of a sum of cosine In mathematics, the trigonom ...

(MDCT) coding and

linear predictive coding Linear predictive coding (LPC) is a method used mostly in audio signal processing and speech processing for representing the spectral envelope of a Digital data, digital signal (information theory), signal of Speech communication, speech in data co ...

(LPC). In hardware, audio codec refers to a single device that encodes analog audio as digital signals and decodes digital back into analog. In other words, it contains both an

analog-to-digital converter In electronics, an analog-to-digital converter (ADC, A/D, or A-to-D) is a system that converts an analog signal, such as a sound picked up by a microphone or light entering a digital camera, into a Digital signal (signal processing), digit ...

(ADC) and

digital-to-analog converter In , a digital-to-analog converter (DAC, D/A, D2A, or D-to-A) is a system that converts a into an . An (ADC) performs the reverse function. There are several DAC ; the suitability of a DAC for a particular application is determined by ...

(DAC) running off the same

clock signal In electronics and especially Synchronous logic, synchronous digital circuits, a clock signal (historically also known as ''logic beat'') oscillates between a high and a low state and is used like a metronome to coordinate actions of digital Electr ...

. This is used in

sound card A sound card (also known as an audio card) is an internal expansion card Modern EEPROM chip suitable for storing expansion card configuration electronically In computing Computing is any goal-oriented activity requiring, benefiting f ...

s that support both audio in and out, for instance. Hardware audio codecs send and receive digital data using

buses A bus (contracted from omnibus, with variants multibus, motorbus, autobus, etc.) is a designed to carry many s. Buses can have a capacity as high as 300 passengers. The most common type is the , with larger loads carried by and es, and sm ...

such as AC-Link,

I²S I²S (Inter-IC Sound), pronounced eye-squared-ess, is an electrical serial bus 300px, Parallel versus serial communication. In telecommunication and data transmission, serial communication is the process of sending data one bit at a time, ...

, SPI,

I²C I2C (Inter-Integrated Circuit, ), alternatively known as I2C or IIC, is a synchronous Synchronization is the coordination of events to operate a system in unison. For example, the Conductor (music), conductor of an orchestra keeps the orch ...

, etc. Most commonly the digital data is

linear PCM Pulse-code modulation (PCM) is a method used to digitally represent sampled analog signal An analog signal is any continuous signal for which the time-varying feature of the signal is a representation of some other time-varying quantity ...

, and this is the only format that most codecs support, but some legacy codecs support other formats such as

G.711 G.711 is a narrowband {{refimprove, date=March 2011 In radio communications, a narrowband channel is a channel in which the bandwidth of the message does not significantly exceed the channel's coherence bandwidth. In the study of wired chan ...

for telephony.

References

{{DEFAULTSORT:Audio Codec fr:Codec

See also

References