A signal processing apparatus includes, a receiving unit which receives a stream includes compression-encoded data via a network, the stream being formed by packets to which time stamps are respectively added, a generating unit which generates a first stream from the stream received by the receiving unit, based on the time stamps added to the packets in the stream received by the receiving unit to output the first stream from an output port, a selector to which has a first port that receives the first stream output from the output port and a second port that receives a second stream including compression-encoded data and being transmitted in real time from outside, the selector selecting one of the first stream input to the first port and the second stream input to the second port, and a decoding unit which decodes the one stream selected by the selector.