GOP

A GOP, or Group of Pictures, is the building block of inter-frame compression in codecs like H.264 and H.265. It begins with a complete I-frame (keyframe) and is followed by P- and B-frames that store only changes predicted from other frames, until the next I-frame starts a new group. Longer GOPs mean smaller files because fewer full frames are stored, but they make editing harder: to show any single frame the decoder must reconstruct from the surrounding group. A shorter GOP (more frequent keyframes) improves seeking, scrubbing, and clean cut points at the cost of size. Editors care about GOP structure when footage feels sluggish to scrub, when choosing export settings, and when a delivery spec demands a specific keyframe interval. Intra-frame codecs effectively use a GOP of one.