In an imaging system having a semiconductor integrated circuit device, noise problems due to a large through-current in an output circuit resulting from the change-over of digital video data outputted from an AD conversion LSI are reduced by a technique involving encoding and code conversion. After AD conversion of an analog color video signal from an imaging element, a difference between codes of adjacent pixels is obtained in regard to the same color, and an output code of this difference is converted into a code with less change-over bits between the adjacent codes.