1. A data reproduction apparatus having a viterbi decoder, the data reproduction apparatus comprising: a storage unit to store a first input signal; a frequency detection unit to generate a frequency detection signal indicating that a frequency of the first input signal is detected, and to generate frequency information of the first input signal based on a second input signal; and a level value determination unit to detect at least one level value for the first input signal according to the frequency detection signal by converting a sampling rate for the first input signal based on a ratio between the generated frequency information and preset frequency information, and to determine the at least one detected level value as an initial level value of the viterbi decoder.