A signal processing system is provided with a transmitting-side apparatus transmitting a digital signal, and a receiving-side apparatus receiving the digital signal. The transmitting-side apparatus includes a digital signal transmitter transmitting the digital signal and a signal controller controlling the digital signal. The receiving-side apparatus includes a digital signal receiver receiving the digital signal, an error rate detector detecting the error rate of the digital signal received, and a receiving-side controller transmitting error rate data based on the detected error rate to the transmitting-side apparatus. The transmitting-side apparatus further includes a transmitting-side controller receiving the error rate data and controlling the signal controller in response to the error rate data.