A method for setting a motion trigger level is used in detection of motion in a video stream depicting a scene which includes receiving data pertaining to a video stream depicting the scene; dividing the scene into a plurality of specific portions; wherein each image frame of the video stream comprises multiple blocks of pixels, wherein each specific portion of the scene is associated with one or more block of pixels; and for each specific portion of the scene: evaluating, over time, statistical features of bitrate associated with an encoding of block of pixels pertaining to the specific portion of the scene; determining a motion base level based on the evaluated statistical features of bitrate associated with the encoding of block of pixels pertaining to the specific portion of the scene; and setting a motion trigger level based on the motion base level.