A signal processing apparatus includes a first signal processing block and a second signal processing block. The first signal processing block is utilized for processing an input signal to generate a first target processing result, including a plurality of packets initially reproduced from the input signal, to an output port of the first signal processing circuit, where each of the packets contains a corresponding packet identifier (PID). The second signal processing block has an input port coupled to the output port of the first signal processing circuit, and is utilized for processing the first target processing result according to PIDs of the packets and accordingly generating a second target processing result. There is no buffer coupled between the output port of the first signal processing circuit and the input port of the second signal processing circuit.