Codec

A codec is the software or hardware logic that encodes and decodes audio or video formats. Windows applications use codecs for files such as H.264 video, HEVC video, AAC audio, and many streaming formats; graphics packages may also expose hardware acceleration for supported formats. When a file has sound but no picture, or plays in one application but not another, the required codec may be unavailable to that application rather than the sound or display hardware being faulty. Check the file type and the application's documented support first. Prefer codecs delivered by Windows, the Microsoft Store, or a trusted media application, and avoid broad download bundles that install unrelated filters across the system.