Comb filtering differs from audio to video. For audio, it is the outcome; for composite video, it is an added function. See
composite video.
Audio Comb Filtering
Audio comb filtering is the unintentional effect when multiple microphones or sound sources are used, and the resulting delay in frequencies sound hollow. However, to create special effects, audio comb filtering can be intentionally applied.
Video Comb Filtering
With regard to "composite video," comb filtering intentionally separates the brightness (luminance) from the color (chroma). To reduce artifacts, each line is combined with a delayed version of itself (see
dot crawl).