A method for encoding video is disclosed. The method comprises the steps of receiving information representative of pixels in a current digital image frame of a video to be encoded, calculating a group value for each group of neighboring pixels based on the received information, accumulating group values of corresponding groups of pixels in a first sequence of frames to form a first accumulation of accumulated group values, accumulating group values of corresponding groups of pixels in a second sequence of frames to form a second accumulation of accumulated group values, wherein the second sequence includes frames captured over a longer period of time than the first sequence, comparing accumulated group values of the first accumulation with accumulated group values of the second accumulation, calculating a global change value based on the comparison, setting a GOP length based on the global change value; and encoding the current image frame as an intra-frame or inter-frame based on the GOP length. An encoder system for encoding video is also disclosed.