To generate a correct stream from all blocks and blocks including each border which a decoder with prescribed decoding capability can warrant decoding.

A full block verification unit u5 and a border block verification unit u6 respectively inform a verification synchronization unit u7 about frame processing end commands c1, c2 when a frame under verification (under processing) is finished. The verification synchronization unit u7 monitors the frame processing end commands c1, c2 to output a frame processing start command c3 when both the full block verification unit u5 and the border block verification unit u6 complete the processing of the frame. The full block verification unit u5 and the border block verification unit u6 interrupt their processing until the frame processing start command c3 is received and start the processing of a succeeding frame when receiving the frame processing start command c3.