An inter-image operation apparatus has temporal subtraction means for calculating a temporal subtraction image from two or more sets of base image data, and history data recording means for recording history data concerning the calculated temporal subtraction image in a database server and concurrently attaching the same history data to the data on the temporal subtraction image. A divider panel attached to at least one of the panels has upper and lower portions separated by an opening. The bit rate feedback information is obtained based on the congestion information on the network on the sender side, or obtained on a receiver side and fed back.