Digital magnetic recording/reproducing apparatus
A digital magnetic recording/reproducing apparatus includes an LVA (List Viterbi Algorithm) detector which produces first to nth best sequences (n>1) of a decoded result, and replaces a likelihood ratio and a path memory of the ith best sequence (i=2, 3, . . . , n) with those of the (2i−1)th best sequence when contents of path memories of the (i−1)th and ith best sequences are equal to each other and an absolute value of a difference between likelihood ratios of the (i−1)th and (2i−1)th best sequences is smaller than a decision threshold. Alternatively, the LVA detector initializes a likelihood ratio of the ith best sequence to be a likelihood ratio of the (i−1)th best sequence with a constant difference value added thereto when contents of path memories of the (i−1)th and ith best sequences are equal to each other.
1. A digital magnetic recording/reproducing apparatus for recording and reproducing digital information comprising:
a Viterbi detector which decodes a signal sequence obtained by partial response equalization and produces n candidates of a decoded result, the candidates being a best candidate to an nth best candidate and being produced simultaneously by the Viterbi decoder;
an error detector which detects errors in the n candidates; and
an selector which selects from the candidates a candidate having no detected errors as a correct decoded result and supplies the correct decoded result to a recording decoder;
wherein the Viterbi decoder uses a path memory having a length which is shorter than a length of an error detection block used by the error detector.
2. A digital magnetic recording/reproducing apparatus according to claim 1 , wherein the length of the error detection block is selected so that a coding rate after error detection is not less than 8/9.
3. A digital magnetic recording/reproducing apparatus according to claim 1 , wherein the error detection block is a CRC (Cyclic Redundancy Check) block.
4. A digital magnetic recording/reproducing apparatus according to claim 1 , wherein the Viterbi detector uses an LVA (List Viterbi Algorithm) for signal processing.
5. A digital magnetic recording/reproducing apparatus according to claim 1 , further comprising a coder which adds error detection check bits to the signal sequence.
6. A digital magnetic recording/reproducing method for recording and reproducing digital information comprising the steps of:
decoding a signal sequence obtained by partial response equalization and producing n candidates of a decoded result using a Viterbi decoder, the candidates being a best candidate to an nth best candidate and being produced simultaneously by the Viterbi decoder;
detecting errors in the n candidates; and
selecting from the candidates a candidate having no detected errors as a correct decoded result and supplying the correct decoded result to a recording decoder;
wherein the Viterbi decoder uses a path memory having a length which is shorter than a length of an error detection block used in the error detecting step.
7. A digital magnetic recording/reproducing method according to claim 6 , wherein the length of the error detection block is selected so that a coding rate after error detection is not less than 8/9.
8. A digital magnetic recording/reproducing method according to claim 6 , wherein the error detection block is a CRC (Cyclic Redundancy Check) block.
9. A digital magnetic recording/reproducing method according to claim 6 , wherein the Viterbi detector uses an LVA (List Viterbi Algorithm) for signal processing.
10. A digital magnetic recording/reproducing method according to claim 6 , further comprising the step of adding error detection check bits to the signal sequence.
11. An apparatus for recording and reproducing digital information comprising:
a decoder which decodes a signal sequence and produces n candidates of a decoded result, each of the n candidates being divided into error detection blocks; and
a circuit which detects errors in the n candidates based on the error detection blocks, and selects a candidate having no errors from the n candidates as a correct decoded result,
wherein the decoder produces the n candidates using a path memory having a length which is shorter than a length of each of the error detection blocks.
12. An apparatus according to claim 11 , wherein the length of the error detection block is selected so that a coding rate after error detection is not less than 8/9.
13. An apparatus according to claim 11 , wherein the error detection blocks are CRC (Cyclic Redundancy Check) blocks.
14. An apparatus according to claim 11 , wherein the detector uses an LVA (List Viterbi Algorithm) for signal processing.
15. An apparatus according to claim 11 , further comprising a coder which adds error detection check bits to the signal sequence.
16. A method for recording and reproducing digital information in a digital magnetic recording/reproducing apparatus, the method comprising:
decoding a signal sequence and producing n candidates of a decoded result, each of the n candidates being divided into error detection blocks;
detecting errors in the n candidates based on the error detection blocks; and
selecting a candidate having no errors from the n candidates as a correct decoded result,
wherein the n candidates are produced using a path memory having a length which is shorter than a length of each of the error detection blocks.
17. A method according to claim 16 , wherein the length of the error detection block is selected so that a coding rate after error detection is not less than 8/9.
18. A method according to claim 16 , wherein the error detection blocks are CRC (Cyclic Redundancy Check) blocks.