I expected a website like http://www.codecguide.com/faq.htm to have a ‘nice’ simple definition of what a codec is. After reading the What are codecs? section, I was no better informed, .. or as usual – end-up with more questions than when I started.
GOOGLED ‘wiki codecs‘ (AND; pasted a more friendly definition below)
A codec is a device or computer program capable of encoding and/or decoding a digital data stream or signal. The word codec is a portmanteau (a blending of two or more words) of ‘compressor-decompressor’ or, more accurately, ‘coder-decoder’.
Historically a modem was a contraction of modulator/demodulator (modem was called dataset by telcos) and converted digital data from computers to analog for phone line transmission. On the receiving end the analog was converted back to digital. CODECs did the opposite (convert audio analog to digital and then computer digital sound back to audio). There was no compression involved in CODECs, only coding and decoding.
Previous post on ‘Codecs’
FROM a VoIP perspective; Codecs are used to convert an analog voice signal to digitally encoded version. Codecs vary in the sound quality, the bandwidth required, the computational requirements, etc.
Each service, program, phone, gateway, etc typically supports several different codecs, and when talking to each other, negotiate which codec they will use.