In order to control the coding quantity depending on the processing situation at the terminal when decoding or synthesizing plural pictures or sounds simultaneously, the decoding apparatus of the invention comprises a reception control unit 11 for receiving the information, a separation unit 12 for analyzing and separating the received information, a priority decision unit 14 for determining the priority of processing of the pictures separated in the separation unit 12, a picture expanding unit 18 for expanding the pictures according to the determined priority, s picture synthesizing unit 19 for synthesizing the pictures on the basis of the expanded pictures, a synthesis result accumulating unit 22 for accumulating the synthesized pictures, a reproduction time control unit 23 for controlling the time for starting reproduction, and an output unit 24 for delivering the result of synthesis according to the information of the reproduction time control unit 23.