What Is A Codec

What Is A Codec

(1) (COder/DECoder or COmpressor/DECompressor) Hardware or software that encodes/compresses and decodes/decompresses audio and video data streams. The purpose of a codec is to reduce the size of digital audio samples and video frames in order to speed up transmission and save storage space. The goal of all codec designers is to maintain audio and video quality while compressing the binary data further. Speech codecs are designed to deal with the characteristics of voice, while audio codecs are developed for music. Codecs may also be able to transcode from one digital format to another; for example, from PCM audio to MP3 audio.

The codec algorithms may be implemented entirely in a chip or entirely in software in which case the PC does all of the processing. They are also commonly implemented in both hardware and software where a sound card or video capture card performs some of the processing, and the main CPU does the rest.

When analog signals are entered into a computer, cellphone or other device via a microphone or video source such as a VHS tape or TV, analog-to-digital converters create the raw digital audio samples and video frames. Speech, audio and video codecs are typically lossy codecs that compress data by altering the original format, which is why "codec" means "encoder/decoder" and "compressor/decompressor." If a codec uses only lossless compression in which the original data is restored exactly, then it would not be a coder/decoder. This is a subtle point, but the two meanings of the acronym have been confusing.

See companding,

Companding

(1) In the analog world, a method for improving audio reproduction by altering the dynamic range of the signals. On outgoing transmission, it raises the amplitude of weak signals and lowers the amplitude of strong signals. On incoming transmission, it restores the signal to its original form. Such techniques are used in dbx and Dolby noise reduction, AM, FM and SSB radio as well as in voice and musical instrument amplification to reduce feedback.

(2) In the digital world, a compression technique used in pulse code modulation (PCM). It reduces the number of bits used to represent digital voice samples in the loudest parts of the conversation.

codec switching and lossy compression.

(2) (COmpressor-DECompressor) The term is sometimes used to refer to a general data compression algorithm; for example, a "Zip codec." Using "codec" in this manner tends to refer to a realtime requirement; for example, reading a file, decompressing it and displaying it in one continuous operation. In the same context, the term is also used to refer to a graphics compression algorithm such as one that creates a GIF or JPEG file.

CODEC Examples

Following is a list of popular speech, audio and video codecs. The difference between speech and audio codecs is that speech codecs look for speech patterns in order to compress the data further.



SPEECH CODECS (DIGITAL)

Name     Purpose

A-Law PCM telephone circuit (Europe)
µ-Law PCM telephone circuit (U.S.)
DV Audio MiniDV audio
GSM 6.10 GSM cellphone
G.711 Audio/videoconferencing (ITU)
G.722 Audio/videoconferencing (ITU)
G.723.1 VoIP, Audio/videoconferencing (ITU)
G.728 Audio/videoconferencing (ITU)
G.729 Audio/videoconferencing (ITU)
AMR-NB GSM, 3GPP (ETSI narrowband)
AMR-WB GSM, 3GPP (ETSI wideband)
ACELP.net General speech (VoiceAge)
ACELP.wide High quality (VoiceAge)

AUDIO CODECS (DIGITAL)

Name Purpose

AAC Music with digital rights (DRM)
WMA Music (Windows streaming)
RA, RAM Music (RealNetworks streaming)
AIFF Music (Macintosh)
AU Music (Sun)
MP3 Music
ACELP.live Music (VoiceAge)
Ogg Vorbis Music (open source standard)

VIDEO CODECS (DIGITAL)

Name Purpose

MPEG-1 Movies
MPEG-2 Movies
MPEG-4 Movies
AVI Movies (Windows)
WMV Movies and Streaming (Windows)
RM, RV Movies and Streaming (RealNetworks)
Indeo Movies (Intel)
Cinepak Movies (SuperMac Technologies)
Sorenson Movies (Sorenson Media)

H.261 Videoconferencing (ITU)
H.263 Videoconferencing (ITU)
H.264 Videoconferencing (ITU)

===============================

Definitions of codec on the Web

Short for compressor/decompressor, a codec is any technology for compressing and decompressing data. Codecs can be implemented in software, hardware, or a combination of both. Some popular codecs for computer video include MPEG, Indeo and Cinepak. In telecommunications, (short for coder/decoder) a device that encodes or decodes a signal. For example, telephone companies use codecs to convert binary signals transmitted on their digital networks to analog signals converted on their analog networks. The translation of a binary value into a voltage that can be transmitted over a wire.
www.xilinx.com/publications/glossary.htm


A coder-decoder that is used to convert analog signals such as video or voice into digital form for transmission over digital medium and, upon reception, reconverts the signals to the original analog form. May also perform other signal processing functions: coder-decoder or compressor-decompressor. (Novak)
citl.tamu.edu/citl-glossary-main.htm


(1. coder/decoder) (n.) In communications engineering, integrated circuits or chips that convert data to be used in, for example, a modem. A codec uses analog-to-digital conversion and digital-to-analog conversion in the same chip. See decoder, encoder. (2. compression/decompression) (n.) An algorithm or computer program for reducing byte consumption in large files and programs. See data compression.
docs.sun.com/db/doc/805-4368/6j450e60c


1. Short for compressor/decompressor, a codec is any technology for compressing and decompressing data. Codecs can be implemented in software, hardware, or a combination of both. Some popular codecs for computer video include MPEG, Indeo and Cinepak. 2. In telecommunications, (short for coder/decoder) a device that encodes or decodes a signal. For example, telephone companies use codecs to convert binary signals transmitted on their digital networks to analog signals converted on their analog networks. 3. The translation of a binary value into a voltage that can be transmitted over a wire.
www.5starsupport.com/info/glossary.htm


Compression-decompression or compressor-decompressor. This may be either a software-only, or a hardware assisted scheme that is used to process digital video and/or audio files. A CODEC reduces the amount of data to be transmitted by discarding redundant data on the transmitting end and reconstituting the signal on the receiving end.
neirtec.terc.edu/k12vc/resources/glossary.cfm


Equipment used to transform analog voice signals to digital signals (coder) and digital signals to analog signals (decoder). May be in the digital PBX or in the phone itself.
www.rvcomp.com/wiring/EIA/glossary.htm


Device that converts analog voice signals into digital signals for transmission, and then reconverts them to the original voice form. It can be in the telephone or part of the PBX.
www.c-b.com/industryinfo/glossaries/telecom.asp


(acronym for “COmpression/DECompression”) A specialized computer program used to reduce the size of large video and audio files. Examples of common codecs are MPEG and Cinepak.
catalyst.washington.edu/glossary.html


Short for "compressor/decompressor"; refers to the hardware in a cell phone and in the cell network that compresses digitized voice prior to transmission AND takes received compressed voice and decompresses it prior to passing it to either a cell phone speaker or into a wireline system. Codec allows the cell network to essentially pass a lot of data in compressed form to permit additional users on the system and to save bandwidth. The idea behind codec is that human voices are highly lossy and a significant amount of the conversation can be removed since human ears can fill in the removed gaps at the other end. Each technology has different codec algorithms -- for CDMA there is 13K and 8K.
www.geckobeach.com/cellular/intro/glossary.htm


"Coder-decoder." A device that converts analog video and audio signals into a digital format for transmission. Also converts received digital signals back into analog format.
www.pbs.org/digitaltv/glossary.html


(Compression and Decompression) Compresses information so that it can be sent across a network faster, and decompresses information received via the network.
support.radioshack.com/support_tutorials/audio_video/digvid-glossary.htm


Coder/decoder. Codecs convert data between uncompressed and compressed formats, reducing the bandwidth a clip consumes.
service.real.com/help/library/guides/realonescripting/browse/htmfiles/glossary.htm


Computing & media A COmpressor DECompressor is a piece of computer hardware or software used for the compression and/or decompression of digital media (most usually audio or video). The most common file formats created and read by CODECs include MP3 for compressed audio, and MPEG-1, MPEG-2, QuickTime-1 and M-JPEG for digital video.
www.nottingham.ac.uk/cyber/fullglos.html


Short for compressor/decompressor. An algorithm or scheme used when recording digital video or audio. A codec is used, for example, when video is transmitted over the Internet; the video is compressed on the sending end and decompressed on the receiving end. Windows Media Tools provides a choice of codecs for ASF content. Users can select a codec based on the audio or image quality, and image size preferred.
www.microsoft.com/windows2000/en/advanced/help/ns_glossary_epcb.htm


A coder decoder. The terminology is commonly use for equipment which transmits and receives coded video information. Coding compresses the video information so that it may by transmitted over a digital channel with a lower bandwidth than would otherwise be required to carry the signal.
ops.fhwa.dot.gov/Travel/Arterials_and_Signals/Glossary.htm


Equipment used to transform analog voice signals to digital signals (coder) and digital signals to analog signals (decoder). May be in digital PABX or in the device/instrument itself.
www.networkcables.com/c.htm


a term used for a "code/decode" electrical device which converts an analog electrical signal into a digital form for transmission purposes. It is generally used to transform video signals into digital form for transmission over digital transmission systems. Generally speaking, this digital information must be reconverted into analog form at its point of reception.
telemedicine.wramc.amedd.army.mil/Support/GlosTermTMED1.htm


Compression/decompression technology for digital video and stereo audio.
www.macsounduk.com/pc_glossary.html


Acronym for coder-decoder. 1. An assembly consisting of an encoder and a decoder in one piece of equipment. (188) 2. A circuit that converts analog signals to digital code and vice versa. 3. An electronic device that converts analog signals, such as video and voice signals, into digital form and compresses them to conserve bandwidth on a transmission path. (188) Note: Codecs in this sense are used in this sense for video conferencing systems.
www.bandwidthmarket.com/resources/glossary/C5.html


Compression-Decompression. Various CODECs exist to handle media, optimising the efficiency with which they are stored and delivered using compression and decompression technology. A compressed file must be decompressed, or reinterpreted, before it can be delivered to the end user. This process usually means loss of quality.
www.thinkworks.co.uk/support/gad.htm


(pronounced CO-deck, short for compressor/decompressor) refers to a device inside the phone (and at the cell system) which takes digitized voice and compresses it prior to transmission to the cell, and which takes compressed voice received from the cell and decompresses it prior to playing it out the speaker of the phone. Codec algorithms are extremely sophisticated and are designed specifically around the characteristics of human voices and human ears. There are three in common use in IS-95, called "8K", "13K" and EVRC. GSM and IS-136 have their own codec standards.
home.san.rr.com/denbeste/glossary.html


Codec stands for compression / decompression. A codec is a small program that's installed on your computer which then allows Windows to compress and/or decompress audio to and from certain formats. Codecs which allow for higher quality compression are available for download separate from any specific software program, but are not useful unless you have a program that supports that Codec. For example, Blaze Audio RipEditBurn supports both the Fraunhofer and LAME codecs when creating MP3 files.
www.blazeaudio.com/glossary.html


Pertaining to adapters that compress and decompress video files. The letters "CODEC" represent "compression/decompression"; in the past, they represented "coder/decoder."
www.gcal.ac.uk/cit/helpdesk/useful_definitions.htm


Compresses information so that it can be sent across a network faster, and decompresses information received via the network.
www.kodak.com/US/en/digital/dlc/book4/chapter2/glossaryC.shtml


Short for compressor/decompressor; a codec is any technology for compressing and decompressing data. Codecs can be implemented in software, hardware, or a combination of both.
electronics.cnet.com/consumerelectronics/0-6613935-7-2643634.html
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