With dynamic Group of Pictures (GOP), the interval between I-frames is adjusted dynamically, based on the amount of the motion in the scene. I-frames contain the whole scene and are usually larger than P-frames which only contain changes compared to the previous frame. In scenes with limited or no motion, very few new I-frames need to be sent, so the overall savings in the bitrate and bandwidth are considerable, whilst still maintaining the required level of detail. The GOP length of the compressed video is adjusted in real-time, according to the amount of motion.
Figure 3: The GOP length is shorter when there is activity in the scene, but increases dynamically when there is less movement, resulting in fewer I-frames.