PURPOSE: To eliminate necessity to respectively perform reading, correcting and writing operations to a memory by just once storing an auxiliary data word into the memory.

CONSTITUTION: A memory 210 is provided for storing plural input video data blocks while containing plural pixel data words and the auxiliary data word concerning the input video data block in each input video data block. The stored pixel data words are read out while changing the order together with the correspondent auxiliary data word. The auxiliary data word concerning the input video data blocks in the prescribed order is read into a recirculation buffer 230. A means for successively reading the output video data blocks out of the memory 210 and the recirculation buffer simultaneously output the respective pixel data words and correspondent auxiliary data word of respective output video data blocks.