A codec is software or hardware that encodes and decodes media, compressing audio or video for storage or transmission and expanding it again for playback. The word joins coder and decoder.
In practice
A video call compresses your camera image before sending it and decompresses the other person's stream on arrival. Graphics hardware often includes dedicated codec blocks, which the display driver exposes so playback uses less processor time and battery.
Common confusion
Codec does not mean file format: a container file can hold streams encoded with various codecs. In audio hardware, codec can also mean the physical chip converting between analogue and digital signals, a different but related use of the word.
Why it matters to readers
When playback works on one computer but stutters on another, codec capability in the hardware and its driver is a common difference. Release notes for display drivers frequently mention codec changes.
A closer look
Hardware codec capability is specific to each format and profile. A graphics processor may decode one modern video format but only encode an older one. When an application reports software decoding, it may be because the hardware lacks capability for that format or because the driver does not expose it, two different causes that release notes can help distinguish.
