Data decoding method and circuit and information recording and reproducing apparatus using the same

A data decoding method for converting an input signal sequence to a decoded code data sequence by using maximum likelihood data sequence decoding method,

• a first step of referring to an input signal sequence input for data detection by using said maximum likelihood data sequence detection method and a first decoded code data sequence decoded for said input signal sequence by using said maximum likelihood data sequence detection method, and calculating likelihood values (probabilities) that error events having preset predetermined code error patterns occur at each code position on said first decoded code data sequence;
• a second step of referring to contents of decoded code values at the position of a relevant decoded code, for which each likelihood value is calculated at said first step, and positions of before and after the relevant decoded code over a predetermined code length, and setting a predetermined reference value associated with the referred-to contents of the decoded code values;
• a third step of comparing each likelihood value calculated at said first step with the reference value set at the second step;
• and
• a fourth step of inverting code values included in code values of said first decoded code data sequence and of which the decoded code position is associated with said predetermined code error pattern, based on a result of said third step, thereby generating a second decoded code data sequence, and outputting the second decoded code data sequence as a resulting decoded code data sequence.

A data decoding circuit for converting an input signal sequence to a decoded code data sequence by using maximum likelihood data sequence detector, said data decoding circuit comprising a decoded code data processing unit behind said maximum likelihood data sequence detector, said decoded code data processing unit comprising;

• a computation circuit which refers to an input signal sequence input to said maximum likelihood data sequence detector and a first decoded code data sequence decoded by using said maximum likelihood data sequence detector, and calculates likelihood values (probabilities) that error events having preset predetermined code error patterns occur at each code position on said first decoded code data sequence;
• a compensation circuit which refers to contents of decoded code values at the position of a relevant decoded code, for which each likelihood value is calculated at said computation circuit, and positions of before and after the relevant decoded code over a predetermined code length, selects a predetermined compensation value associated with the referred-to contents of the decoded code values, and adds the selected compensation value to the likelihood value calculated by said computation circuit, and thereby performing compensation for the likelihood value;
• a comparison circuit which compares each likelihood value compensated by said compensation circuit with a predetermined reference value;
• and
• a code inversion circuit which inverts code values included in code values of said first decoded code data sequence and of which the decoded code position is associated with said predetermined code error pattern, based on a result output by said comparison circuit, thereby generating a second decoded code data sequence, and outputting the second decoded code data sequence as a resulting decoded code data sequence.

A data decoding circuit for converting an input signal sequence to a decoded code data sequence by using maximum likelihood data sequence detector, said data decoding circuit comprising a decoded code data processing unit behind said maximum likelihood data sequence detector, said decoded code data processing unit comprising;

• a computation circuit which refers to an input signal sequence input to said maximum likelihood data sequence detector and a first decoded code data sequence decoded by using said maximum likelihood data sequence detector, and calculates likelihood values (probabilities) that error events having preset predetermined code error patterns occur at each code position on said first decoded code data sequence;
• a selection circuit which refers to contents of decoded code values at the position of a relevant decoded code, for which each likelihood value is calculated at said computation circuit, and positions of before and after the relevant decoded code over a predetermined code length, and selects a predetermined reference value associated with the referred-to contents of the decoded code values;
• a comparison circuit which compares each likelihood value calculated by said computation circuit with a predetermined reference value selected by said selection circuit;
• and
• a code inversion circuit which inverts code values included in code values of said first decoded code data sequence and of which the decoded code position is associated with said predetermined code error pattern, based on a result output by said comparison circuit, thereby generating a second decoded code data sequence, and outputting the second decoded code data sequence as a resulting decoded code data sequence.

A data decoding method for convergting an input signal sequence to a decoded code data sequence by using maximum likelihood data sequence decoding method, said data decoding method comprising of steps of:

• calculating likelihood values (probabilities) that error events having preset predetermined code error patterns occur at each code position on a first decoded code data sequence which is decoded by using said maximum likelihood data sequence detection method from the input signal sequence or the first decoded code data sequence;
• inverting code values in each decoded code position of said first decoded code data sequence, according to the likelihood value;
• and
• outputting a second decoded code data sequence including the inverted code value as a resulting decoded code data sequence.

A data decoding circuit comprising a maximum likelihood data sequence decoder;

• a computation circuit which calculates likelihood values (probabilities) that error events having preset predetermined code error patterns occur at each code position on a first decoded code data sequence which is decoded by using said maximum likelihood data sequence detector from the input signal sequence or the first decoded code data sequence;
• a comparison circuit which compares the likelihood value with a predetermined threshold;
• a code inversion circuit which inverts code values in each decoded code position of said first decoded code data sequence, according to an output results of said comparison circuit;
• and
• outputting a second decoded code data sequence including the inverted code value as a resulting decoded code data sequence.