A device or the like capable of improving continuity of a moving image outputted to an image output device of a remote operation device even in circumstances where an inter-frame difference of the moving image becomes large. When it is predicted that a data amount of a captured image is to exceed a threshold in consideration of a detection result of a moving mode of a working machine, high frequency components exceeding a specified frequency in a second specified image area excluding a first specified image area of the captured image are eliminated Thus, the data amount of the captured image is reduced so that the data amount becomes equal to or smaller than the threshold. Then, not only inter-frame continuity of the first specified image area of an environment image outputted to an image output device of a remote operation device but also visibility by an operator is improved.