(1) (video en
COder/
DECoder)  Software that compresses and decompresses a digital video signal.  MPEG, Windows Media Video (WMV) and H.264 are examples of popular codecs that compress and decompress digital video.  The video codec may also be a hardware circuit.  See 
codec examples, 
codec, 
MPEG, 
Windows Media formats, 
QuickTime, 
H.264 and 
VC-1.
(2) (video en
COder/
DECoder)  A hardware circuit that converts analog video (NTSC, PAL, SECAM) into digital code and vice versa.  The circuit may provide only the A/D and D/A conversion, or it may include a compression algorithm to further reduce the signal such as defined in #1 above.  See 
codec.