electronics a set of equipment that encodes an analogue speech or video signal into digital form for transmission purposes and at the receiving end decodes the digital signal into a form close to its original
Word Origin for codec
C20: from co (de) + dec (ode)
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
by 1970, an abbreviation from compressor-decompressor or coder-decoder, on model of modem.
Online Etymology Dictionary, © 2010 Douglas Harper