isr.co.ro : glossary Codec Short for "coder-decoder," a unit, circuit, or program that converts information from its usual format to an encoded version used for storage or transmission--and converts it back again. One common type of codec you might encounter is the hardware video codec, which is used to convert audio or video information to digital form for transmission or storage and then back to analog form for recording or viewing. Another is the software compression codec, used to convert a digitized image, video clip, or sound to and from a more compressed version.