a hard drive carrier is disclosed that includes a detachable tab on the top wall of the frame of the carrier. Communication buffer memory includes free and committed memory, with copies of transmitted messages awaiting acknowledgement stored in committed memory of transmit buffer. Moreover, there is executed a detection processing for detecting a corresponding point which corresponds to each reference point of one frame contained in the first compressed dynamic image from one frame contained in the second compressed dynamic image by causing each set of frames between said first compressed dynamic image and said second compressed dynamic image to be a target.