Eight-to-fifteen modulation using no merging bit and optical disc recording or reading systems based thereon

A method of modulating a p-bit source code sequence into a q-bit (p<q) object code sequence which includes no merging bit and whose NRZI converted version satisfies predetermined run-length-limited constraints in a p-to-q modulator provided with a code table comprising a column for storing 2p possible p-bit source codes in order of magnitude and a plurality of columns (hereinafter referred to as “subtables”), each subtable comprising a subtable ID for identifying the subtable and 2p combinations of q-bit object codes and respective next subtable fields which combinations are associated in the row directions with respective source codes, each of said next subtable fields containing a subtable ID of a subtable to be used in a modulation of a next source of said source code sequence so as to cause said source code sequence to satisfy said RLL constraints, and selected object codes appearing repeatedly in said q-bit object codes in each subtable such that combinations of appearances of each of said selected object codes and respective next subtable fields are unique in the subtable, and wherein said plurality of subtables include at least one group of a first subtable and at least one second subtable such that said first subtable is usable in place of said at least one second subtable for source codes of said 2p source codes that are in a predetermined range and that, for each of said source codes in said predetermined range, the number of “1” symbols of two corresponding object codes of said first subtable and each of said at least one second subtable is an odd number, the method comprising the steps of:

• retrieving a first object code associated with a source code of said source code sequence from a subtable identified by a next subtable field attached to the last modulated object code;
• making a test to see if said subtable identified by said next subtable field is one of said at least one second subtable and said source code is in said predetermined range;
• in response to a pass in said test, retrieving a second object code associated with said source code of said source code sequence from said first subtable;
• calculating a first digital sum value (DSV) and a second DSV by using said first object code and said second object code, respectively;
• if the absolute value of said second DSV is smaller than that of said first DSV, including said second object code in said q-bit object code sequence;
• and
• if said test is unsuccessful or if the absolute of said second DSV is not smaller than that of said first DSV, including said first object code in said q-bit object code sequence.

A method of demodulating a q-bit code sequence into a p-bit (p<q) code sequence in a q-to-p demodulator provided with a code table comprising a column for storing 2p possible p-bit codes in order of magnitude and a plurality of columns (hereinafter referred to as “subtables”), each subtable comprising a subtable ID for identifying the subtable and 2p combinations of q-bit codes and respective next subtable fields which combinations are associated in the row directions with respective p-bit codes, each of said next subtable fields containing a subtable ID of a subtable to be used in a modulation of a next p-bit code of said p-bit code sequence so as to cause said p-bit code sequence to satisfy said RLL constraints, and selected q-bit codes appearing repeatedly in said q-bit codes in each subtable such that combinations of appearances of each of said selected q-bit codes and respective next subtable fields are unique in the subtable, and wherein the q-to-p demodulator is further provided with means based on a value of a next q-bit code following a current q-bit code for calculating at least one subtable from which said next q-bit code is derivable to provide a calculated subtable ID's and a possible state table for associating each of ending types determined by respective ranges of the 0-run length on the LSB (least significant bit) side (hereinafter, referred to as “LSB 0-run length”) of said current q-bit codes with ID's of possible subtables compatible with the ending type, the method comprising the steps of:

• finding ID's of said compatible subtables based on said LSB 0-run length of said current q-bit code;
• obtaining said calculated subtable ID's from said means;
• finding, as a next subtable ID for said next q-bit code, an ID common to said ID's of said compatible subtables and said calculated subtable ID's;
• searching, a subtable identified by a next subtable ID for said current q-bit code, for a combination of said current q-bit code and said next subtable ID for said next q-bit code;
• and
• outputting a p-bit code in a row in which said combination is located.

A method of demodulating a q-bit code sequence into a p-bit (p<q) code sequence in a q-to-p demodulator provided with means based on a value of a next q-bit code following a current q-bit code for calculating at least one subtable from which said next q-bit code is derivable to provide a calculated subtable ID's and a decoding table for associating each of possible q-bit current codes with an ending type and corresponding p-bit codes further associated with respective subtable ID's for use in a demodulation of said next q-bit code, the method comprising the steps of:

• finding ID's of compatible subtables based on said ending type associated with said q-bit current codes;
• obtaining said calculated subtable ID's from said means;
• finding, as a next subtable ID for said next q-bit code, an ID common to said ID's of said compatible subtables and said calculated subtable ID's;
• and
• obtaining a p-bit code associated with said current q-bit code and said next subtable ID for said next q-bit code and outputting said obtained p-bit code.

A system for modulating a p-bit source code sequence into a q-bit (p<q) object code sequence which includes no merging bit and whose NRZI converted version satisfies predetermined run-length-limited constraints, the system comprising:

• a code table comprising a column for storing 2p possible p-bit source codes in order of magnitude and a plurality of columns (hereinafter referred to as “subtables”), each subtable comprising a subtable ID for identifying the subtable and 2p combinations of q-bit object codes and respective next subtable fields which combinations are associated in the row directions with respective source codes, each of said next subtable fields containing a subtable ID of a subtable to be used in a modulation of a next source of said source code sequence so as to cause said source code sequence to satisfy said RLL constraints, and selected object codes appearing repeatedly in said q-bit object codes in each subtable such that combinations of appearances of each of said selected object codes and respective next subtable fields are unique in the subtable, and said plurality of subtables including at least one group of a first subtable and at least one second subtable such that said first subtable is usable in place of said at least one second subtable for source codes of said 2p source codes that are in a predetermined range and that, for each of said source codes in said predetermined range, the number of “1” symbols of two corresponding object codes of said first subtable and each of said at least one second subtable is an odd number;
• means for retrieving a first object code associated with a source code of said source code sequence from a subtable identified by a next subtable field attached to the last modulated object code;
• means for making a test to see if said subtable identified by said next subtable field is one of said at least one second subtable and said source code is in said predetermined range;
• means, responsive to a pass in said test, for retrieving a second object code associated with said source code of said source code sequence from said first subtable;
• means for calculating a first digital sum value (DSV) and a second DSV by using said first object code and said second object code, respectively;
• means, responsive to a determination that the absolute value of said second DSV is smaller than that of said first DSV, for including said second object code in said q-bit object code sequence;
• and
• means, responsive to either a determination that said test is unsuccessful or a determination that the absolute of said second DSV is not smaller than that of said first DSV, for including said first object code in said q-bit object code sequence.

A system for demodulating a q-bit code sequence into a p-bit (p<q) code sequence, the system comprising:

• a code table comprising a column for storing 2p possible p-bit codes in order of magnitude and a plurality of columns (hereinafter referred to as “subtables”), each subtable comprising a subtable ID for identifying the subtable and 2p combinations of q-bit codes and respective next subtable fields which combinations are associated in the row directions with respective p-bit codes, each of said next subtable fields containing a subtable ID of a subtable to be used in a modulation of a next p-bit code of said p-bit code sequence so as to cause said p-bit code sequence to satisfy said RLL constraints, and selected q-bit codes appearing repeatedly in said q-bit codes in each subtable such that combinations of appearances of each of said selected q-bit codes and respective next subtable fields are unique in the subtable;
• calculating means, based on a value of a next q-bit code following a current q-bit code, for calculating at least one subtable from which said next q-bit code is derivable to provide a calculated subtable ID's;
• a possible state table for associating each of ending types determined by respective ranges of the 0-run length on the LSB (least significant bit) side (hereinafter, referred to as “LSB 0-run length”) of said current q-bit codes with ID's of possible subtables compatible with the ending type;
• means for finding ID's of said compatible subtables based on said LSB 0-run length of said current q-bit code;
• means for obtaining said calculated subtable ID's from said calculating means;
• means for finding, as a next subtable ID for said next q-bit code, an ID common to said ID's of said compatible subtables and said calculated subtable ID's;
• means for searching, a subtable identified by a next subtable ID for said current q-bit code, for a combination of said current q-bit code and said next subtable ID for said next q-bit code;
• and
• means for outputting a p-bit code in a row in which said combination is located.

A system for demodulating a q-bit code sequence into a p-bit (p<q) code sequence, the system comprising:

• calculating means, based on a value of a next q-bit code following a current q-bit code, for calculating at least one subtable from which said next q-bit code is derivable to provide a calculated subtable ID's;
• a decoding table for associating each of possible q-bit current codes with an ending type and corresponding p-bit codes further associated with respective subtable ID's for use in a demodulation of said next q-bit code;
• means for finding ID's of compatible subtables based on said ending type associated with said q-bit current codes;
• means for obtaining said calculated subtable ID's from said calculating means;
• means for finding, as a next subtable ID for said next q-bit code, an ID common to said ID's of said compatible subtables and said calculated subtable ID's;
• and
• means for obtaining a p-bit code associated with said current q-bit code and said next subtable ID for said next q-bit code and outputting said obtained p-bit code.

A device having an optical disc player which includes a system for demodulating a q-bit code sequence into a p-bit (p<q) code sequence, the system comprising:

• calculating means, based on a value of a next q-bit code following a current q-bit code, for calculating at least one subtable from which said next q-bit code is derivable to provide a calculated subtable ID's;
• a decoding table for associating each of possible q-bit current codes with an ending type and corresponding p-bit codes further associated with respective subtable ID's for use in a demodulation of said next q-bit code;
• means for finding ID's of compatible subtables based on said ending type associated with said q-bit current codes;
• means for obtaining said calculated subtable ID's from said calculating means;
• means for finding, as a next subtable ID for said next q-bit code, an ID common to said ID's of said compatible subtables and said calculated subtable ID's;
• and
• means for obtaining a p-bit code associated with said current q-bit code and said next subtable ID for said next q-bit code and outputting said obtained p-bit code.

An optical disc storing an NRZ1 converted version of a q-bit object code sequence obtained through a method of modulating a p-bit source code sequence into the q-bit (p<q) object code sequence which includes no merging bit and whose NRZI converted version satisfies predetermined run-length-limited constraints in a p-to-q modulator provided with a code table comprising a column for storing 2p possible p-bit source codes in order of magnitude and a plurality of columns (hereinafter referred to as “subtables”), each subtable comprising a subtable ID for identifying the subtable and 2p combinations of q-bit object codes and respective next subtable fields which combinations are associated in the row directions with respective source codes, each of said next subtable fields containing a subtable ID of a subtable to be used in a modulation of a next source of said source code sequence so as to cause said source code sequence to satisfy said RLL constraints, and selected object codes appearing repeatedly in said q-bit object codes in each subtable such that combinations of appearances of each of said selected object codes and respective next subtable fields are unique in the subtable, and wherein said plurality of subtables include at least one group of a first subtable and at least one second subtable such that said first subtable is usable in place of said at least one second subtable for source codes of said 2p source codes that are in a predetermined range and that, for each of said source codes in said predetermined range, the number of “1” symbols of two corresponding object codes of said first subtable and each of said at least one second subtable is an odd number, the method comprising the steps of:

• retrieving a first object code associated with a source code of said source code sequence from a subtable identified by a next subtable field attached to the last modulated object code;
• making a test to see if said subtable identified by said next subtable field is one of said at least one second subtable and said source code is in said predetermined range;
• in response to a pass in said test, retrieving a second object code associated with said source code of said source code sequence from said first subtable;
• calculating a first digital sum value (DSV) and a second DSV by using said first object code and said second object code, respectively;
• if the absolute value of said second DSV is smaller than that of said first DSV, including said second object code in said q-bit object code sequence;
• and
• if said test is unsuccessful or if the absolute of said second DSV is not smaller than that of said first DSV, including said first object code in said q-bit object code sequence.