To output a data stream at a rate that is close to its sending rate.

A video encoder 110 encodes the input video data with compression to generate video streams and an audio encoder 120 encodes the input audio data with compression to generate audio streams. A multiplexer 160 sequentially multiplexes the elementary streams of encoder 110 or 120 and outputs them to a multiplexer 170. A CPU 151 decides the sequence of elementary streams to be multiplexed and the quantity of multiplexing data of each elementary stream, etc., according to the data sizes, etc., notified from data size interfaces 131 and 132, and then controls multiplexes 160 and 170 according to these decided sequence and data quantity. A multiplexed transport packet is buffered by a FIFO buffer 180 and a transport stream is outputted at a rate approximate to the desired one. Furthermore, a packet space control part 190 performs fine adjustment of the packet space, and a transport stream of a desired output rate is generated.