a reproducing device which continuously reproduces a plurality of image data streams each encoded by using inter-frame encoding;

a buffer memory which temporarily stores the encoded image data stream reproduced by said reproducing device;

a decoding time calculation device which calculates a decoding time as a timing at which the encoded image data stream is output from the buffer memory to a decoder;

a buffer size setting device which sets an amount of the buffer memory for storing the encoded image data stream on the basis of an amount required by the encoded image data stream reproduced by the reproducing device, the buffer size setting device setting the amount of the buffer memory to at least twice a maximum value of the amount required by the encoded image data stream reproduced by the reproducing device;

a control device which controls the buffer memory, so as to succeedingly start storing a second encoded image data stream in the buffer memory after storage of a first encoded image data stream in the buffer memory is ended, and to continuously output the first encoded image data stream and the second encoded image data stream stored in the buffer memory to the decoder according to the decoding time calculated by the decoding time calculation device, the first encoded image data stream and the second encoded image data stream being included in the plurality of image data streams reproduced by said reproducing device,

the decoding time calculation device calculating a first decoding time of the second encoded image data stream on the basis of a time when storage of the first encoded image data stream in said buffer memory is ended and a first vbv_Delay value of the second encoded image data stream.