An apparatus for error-correcting an input signal to generate an output signal. The apparatus includes an unreliable-location determining module for determining unreliable-locations of the input signal and generating an indication signal accordingly, a first error-correcting module for error-correcting the input signal to generate a first candidate signal, a second error-correcting module coupled to the unreliable-location determining module for error-correcting the input signal with reference to the indication signal to generate a second candidate signal, and a selecting module coupled to the first and second error-correcting modules for selecting one of the first and second candidate signals to be the output signal.