GOP

Group of Pictures, a grouping of frames (pictures) for interframe compression techniques. Longer GOPs allow for better multi-frame compression but slow down the overall delivery process for live encoding. Each GOP begins with an I-frame keyframe and then can contain any number of predictive (P frames) and bidirectional predictive (B frames). According to Wikipedia: "The GOP structure is often referred by two numbers, for example M=3, N=12. The first one tells the distance between two anchor frames (I or P). The second one tells the distance between two full images (I-frames): it is the GOP length. For the example M=3 N=12, the GOP structure is IBBPBBPBBPBBI"