Decoding apparatus and method thereof

1. An apparatus for improving decoding accuracy of an equalized signal having a direct current (DC) level obtained from an optical disk, comprising:

a Viterbi decoder configured to decode the equalized signal and output a Viterbi-decoded signal; and

a DC controller configured to add an offset value to the equalized signal, to adjust the DC level of the equalized signal such that the equalized signal with the adjusted DC level is decoded.

2. The apparatus as claimed in claim 1 , wherein the Viterbi decoder further decodes the equalized signal according to at least one target level, and the apparatus further comprises:

a level adjustor configured to adjust the at least one target level according to a sliced signal such that the equalized signal is decoded according to the adjusted target level.

3. The apparatus as claimed in claim 2 , further comprising:

a slicer configured to generate the sliced signal by slicing the equalized signal.

4. The apparatus as claimed in claim 1 , wherein the offset value is determined according to a table look-up method.

5. The apparatus as claimed in claim 1 , wherein the DC controller adjusts the DC level of the equalized signal according to the Viterbi-decoded signal.

6. The apparatus as claimed in claim 5 , wherein the DC controller adjusts the DC level of the equalized signal when a digital sum value (DSV) of the Viterbi-decoded signal is larger than a threshold value.

7. The apparatus as claimed in claim 1 , further comprising:

a decoder configured to decode the Viterbi-decoded signal and output an indicator reflecting the decoded condition of the Viterbi-decoded signal, wherein the DC controller adjusts the DC level of the equalized signal according to the indicator.

8. The apparatus as claimed in claim 1 , wherein the DC level of the equalized signal obtained from the optical disk is a predetermined DC level.