Encyclopedia of Computer Science and Technology

92 codecMurcah, Mike, Anne Prince, and Raul Menendez. Murach’s MainframeCOBOL. Fresno, Calif.: Murach and Associates, 2004.Sammet, J. E. “The Early History of COBOL,” in History of ProgrammingLanguages. Wexelblat, R. L., ed., 199–276. NewYork: Academic Press, 1985.codecShort for “coder/decoder,” a codec is essentially an algorithmfor encoding (and compressing) a stream of data fortransmission, and then decoding and decompressing it atthe receiving end. Usually the data involved representsaudio or video content (see streaming). Typically the datais being downloaded from a Web site to be played on apersonal computer or portable player (see multimedia andmusic and video players, digital).A codec is described as “lossy” if some of the originalinformation is lost in the compression process. It thenbecomes a question of whether the loss in quality is perceivedby the user as significant. A codec that preserves allthe information needed to re-create the original file is “lossless.”For most purposes, the much greater size of the losslessversion of a file is not worth the (often imperceptible)increase in quality or fidelity.A codec is usually used in connection with a “containerformat” that specifies how the encoded data is to be storedCodecAACAIFFALACAVIFLACCMP3MPEGOgg VorbisQuick TimeReal Audio andand RealVideoRIFFVorbisWAVWMAWMVContainer Descriptionadvanced audio coding; developed as asuccessor to MP3 and especially usedby Apple (iTunes, iPod, iPhone, etc.)audio interchange file format; audiocontainer format for transferring contentbetween applicationsApple lossless audio codecaudio video interleave; video and moviescontainer formatfree lossless audio codec; music, opensource, losslessactually MPEG-3, probably the mostcommon music codecMoving Picture Experts Group; video,movies, audio (four layers MPEG-1through MPEG-4)music, open source (often used on Linuxsystems)Apple multimediadeveloped by RealNetworks for manyplatformsresource interchange file format; containerformatfree, open-source audio codec (often usedin Linux)Windows audio format (usuallyuncompressed)Windows media audioWindows media videoin a file. Often a container can hold more than one datastream and even more than one kind of media (such asvideo and audio). When one refers to a Windows WAV file,for example, one is actually referring to a container.Most of the popular codecs and file formats are proprietary,which creates something of a dilemma for users whoprefer open-source solutions. However, while most Linuxdistributions do not include support for formats such asMP3 out of the box, distributions such as Ubuntu are nowmaking it easier for users to choose nonsupported proprietarycodecs if desired.The preceding table lists some codecs likely to beencountered by program developers and consumers.Further ReadingAudio Files. Available online. URL: http://www.fileinfo.net/filetypes/audio. Accessed September 3, 2007.Harte, Lawrence. Introduction to MPEG. Fuquay Varina, N.C.:Althos Publishing, 2006.Rathbone, Andy. MP3 for Dummies. 2nd ed. New York: HungryMinds, 2001.Richardson, Iain E. G. Video Codec Design: Developing Image andVideo Compression Systems. New York: Wiley, 2002.Roberts-Breslin, Jan. Making Media: Foundations of Sound andImage Production. Boston: Focal Press, 2003.Thurott, Paul. PC Magazine Windows XP Digital Media Solutions.Indianapolis: Wiley, 2005.Video Files. Available online. URL: http://www.fileinfo.net/filetypes/video. Accessed September 3. 2007.cognitive scienceCognitive science is the study of mental processes such asreasoning, memory, and the processing of perception. Itis necessarily an interdisciplinary approach that includesfields such as psychology, linguistics, and neurology. Theimportance of the computer to cognitive science is that itoffers a potential nonhuman model for a thinking entity.The attempts at artificial intelligence over the past 50 yearshave used the insights of cognitive science to help deviseartificial means of reasoning and perception. At the sametime, the models created by computer scientists (such asthe neural network and Marvin Minsky’s idea of “multipleintelligent agents”) have in turn been applied to the studyof human cognition (see Minsky, Marvin Lee and neuralnetwork).Since the late 19th century, technological metaphorshave been used to describe the human mind. The neuronsand synapses of the brain were compared to the multitudeof switches in a telephone company central office. Theinvention of digital computers seemed to offer an even morecompelling correspondence between neurons and their electrochemicalstates and the binary state of a vacuum tube ortransistor. It is only a small further step to assert that humanmental processes can be reduced in principle to computation,albeit a very complex tapestry of computation. Variousschools of popular psychology and personal improvementhave offered simplistic images of the human mind sufferingfrom “bad programming” that can be debugged or manipulatedthrough various processes. The simulation of someforms of reasoning and language construction by AI pro-