Method and apparatus for storing data on magnetic or optical media

Claim 1

A method of storing data on a recording medium comprising the steps of: grouping digital binary signals into chucks of N bits wherein N is an integer number greater than 1; determining the value of each of N bit chunks; converting said N bit chunks to a corresponding symbol cell, each of said symbol cells having a duration which is dependent upon the value of the corresponding N bit chunk and which is equal to the sum of the minimum transition period for the recording medium and an incremental time period, said incremental time period being directly proportional to the value of said N bit chunk, the maximum duration of said incremental time period being less than the time duration of the minimum transition period; and recording said symbol cells onto a recording medium.

Claim 2

A method of storing data on a recording medium comprising the steps of: grouping digital binary signals into chucks of N bits wherein N is an integer number greater than 1; determining the value of each of N bit chunks; converting said N bit chunks to a corresponding symbol cell, each of said symbol cells having a duration which is dependent upon the value of the corresponding N bit chunk and which is equal to the sum of the minimum transition period for the recording medium and an incremental time period, said incremental time period being directly proportional to the value of said N bit chunk, the maximum duration of said incremental time period being less than the time duration of the minimum transition period; and recording said symbol cells onto a recording medium.

Claim 4

A method of storing data on a recording medium comprising the steps of: grouping binary input signals into chunks of N bits wherein N is an integer number greater than 1; determining the values of each of said N bit chunks; determining the relative frequency of occurrence of each of the values of said N bit chunks; assigning a symbol cell duration to each of said N bit chunks wherein the more frequently a value occurs, the shorter is the time duration assigned to the symbol cell; generating symbol cells for each N bit chunk in accordance with the symbol cell duration assigned thereto; and recording said symbol cells onto a recording medium.

Claim 5

A method of storing data on a recording medium comprising the steps of: grouping binary input signals into chunks of N bits wherein N is an integer number greater than 1; determining the values of each of said N bit chunks; determining the relative frequency of occurrence of each of the values of said N bit chunks; assigning a symbol cell duration to each of said N bit chunks wherein the more frequently a value occurs, the shorter is the time duration assigned to the symbol cell; generating symbol cells for each N bit chunk in accordance with the symbol cell duration assigned thereto; and recording said symbol cells onto a recording medium.

Claim 8

A method of storing data on a recording medium comprising the steps of: grouping binary signals into chunks of N bits wherein N is an integer greater than 1; determining the value of each of said N bit chunks; converting said N bit chunks to a corresponding symbol cell, each of said symbol cells having an assigned duration which is dependent upon the value of the corresponding N bit chunk; recording on a portion of said medium the relative symbol cell juxtapositions for at least two successive symbol cells; determining from said recorded symbol cell juxtapositions the transition shift for each of said juxtapositions of symbol cells; and adaptively precompensating for said transition shift by varying the duration of said symbol cells before recording.

Claim 9

A method of storing data on a recording medium comprising the steps of: grouping binary signals into chunks of N bits wherein N is an integer greater than 1; determining the value of each of said N bit chunks; converting said N bit chunks to a corresponding symbol cell, each of said symbol cells having an assigned duration which is dependent upon the value of the corresponding N bit chunk; recording on a portion of said medium the relative symbol cell juxtapositions for at least two successive symbol cells; determining from said recorded symbol cell juxtapositions the transition shift for each of said juxtapositions of symbol cells; and adaptively precompensating for said transition shift by varying the duration of said symbol cells before recording.

Claim 10

A method of storing data on a recording medium comprising the steps of: grouping binary signals into chunks of N bits wherein N is an integer greater than 1; determining the values of each of said N bit chunks; determining the relative frequency of occurrence of each of the values of said N bit chunks; assigning a symbol cell duration to each of said N bit chunks wherein the more frequently a value occurs, the shorter is the time duration assigned to the symbol cell; generating symbol cells for each N bit chunk in accordance with the symbol cell duration assigned thereto; recording on a portion of said medium the relative symbol juxtaposition for at least two successive symbol cells; determining from said recorded symbol cell juxtapositions the transition shift for each of said juxtapositions of symbol cells; and adaptively precompensating for said transition shift by varying the duration of said symbol cells before recording.

Claim 11

A method of storing data on a recording medium comprising the steps of: grouping binary signals into chunks of N bits wherein N is an integer greater than 1; determining the values of each of said N bit chunks; determining the relative frequency of occurrence of each of the values of said N bit chunks; assigning a symbol cell duration to each of said N bit chunks wherein the more frequently a value occurs, the shorter is the time duration assigned to the symbol cell; generating symbol cells for each N bit chunk in accordance with the symbol cell duration assigned thereto; recording on a portion of said medium the relative symbol juxtaposition for at least two successive symbol cells; determining from said recorded symbol cell juxtapositions the transition shift for each of said juxtapositions of symbol cells; and adaptively precompensating for said transition shift by varying the duration of said symbol cells before recording.

Claim 13

A method of storing data in a recording medium comprising the steps of: grouping binary signals into chunks of N bits wherein N is an integer greater than 1; determining the value of each of said N bit chunks; converting said N bit chunks to a corresponding symbol cell, each of said symbol cells having an assigned duration which is dependent upon the value of the corresponding N bit chunk; recording on a portion of said medium the relative symbol cell juxtapositions for a plurality of successive symbol cells; determining from said recorded symbol cell juxtapositions the transition shift for each of said juxtapositions of symbol cells; modifying the duration of said symbol cells to compensate for said determined transition shift; and recording said symbol cells onto a recording medium.

Claim 14

A method of storing data in a recording medium comprising the steps of: grouping binary signals into chunks of N bits wherein N is an integer greater than 1; determining the value of each of said N bit chunks; converting said N bit chunks to a corresponding symbol cell, each of said symbol cells having an assigned duration which is dependent upon the value of the corresponding N bit chunk; recording on a portion of said medium the relative symbol cell juxtapositions for a plurality of successive symbol cells; determining from said recorded symbol cell juxtapositions the transition shift for each of said juxtapositions of symbol cells; modifying the duration of said symbol cells to compensate for said determined transition shift; and recording said symbol cells onto a recording medium.

Claim 16

A method of storing data on a recording medium comprising the steps of: grouping digital binary signals into chunks of N bits, wherein N is an integer number greater than 1; determining the value of each of said N bit chunks; converting said N bit chunks to a corresponding symbol cell, each of said symbol cells having a duration which is dependent upon the value of the corresponding N bit chunk; recording a plurality of different symbol juxtapositions onto a magnetic medium; determining from said recorded symbol cell juxtapositions the transition shift for each of said juxtapositions of symbol cells; compensating said symbol cells for transition shift by varying the duration thereof; and recording said compensated symbol cells corresponding to said N bit chunks onto a recording medium.

Claim 17

A method of storing data on a recording medium comprising the steps of: grouping digital binary signals into chunks of N bits, wherein N is an integer number greater than 1; determining the value of each of said N bit chunks; converting said N bit chunks to a corresponding symbol cell, each of said symbol cells having a duration which is dependent upon the value of the corresponding N bit chunk; recording a plurality of different symbol juxtapositions onto a magnetic medium; determining from said recorded symbol cell juxtapositions the transition shift for each of said juxtapositions of symbol cells; compensating said symbol cells for transition shift by varying the duration thereof; and recording said compensated symbol cells corresponding to said N bit chunks onto a recording medium.

Claim 21

A method of storing data on a recording medium comprising the steps of: grouping binary signals into chunks of N bits wherein N is an integer greater than 1; determining the value of each of said N bit chunks; converting said N bit chunks to a corresponding symbol cell, each of said symbol cells having an assigned duration which is dependent upon the value of the corresponding N bit chunks; recording on a portion of said medium the relative symbol cell juxtapositions for three successive symbol cells; determining from said recorded symbol cell juxtapositions the transition shift for each of said juxtapositions of symbol cells; compensating said symbol cells for transition shift by varying the duration of said symbol cells; repeating said recording, determining and compensating steps until said transition shift has been compenstated; and compensating symbol cells to be stored for transition shift by varying the duration of said symbol cells in accordance with the determined transition shift of juxtaposed symbol cells.

Claim 22

A method of storing data on a recording medium comprising the steps of: grouping binary signals into chunks of N bits wherein N is an integer greater than 1; determining the value of each of said N bit chunks; converting said N bit chunks to a corresponding symbol cell, each of said symbol cells having an assigned duration which is dependent upon the value of the corresponding N bit chunks; recording on a portion of said medium the relative symbol cell juxtapositions for three successive symbol cells; determining from said recorded symbol cell juxtapositions the transition shift for each of said juxtapositions of symbol cells; compensating said symbol cells for transition shift by varying the duration of said symbol cells; repeating said recording, determining and compensating steps until said transition shift has been compenstated; and compensating symbol cells to be stored for transition shift by varying the duration of said symbol cells in accordance with the determined transition shift of juxtaposed symbol cells.

Claim 23

A method of compensating for transition shift in a magnetic storage medium comprising the steps of: recording on a portion of said magnetic medium a plurality of different bit juxtapositions; recording the order in which said plurality of relative bit juxtaposition are recorded; reading from said medium the order in which said bit juxtapositions are recorded; reading from said medium the plurality of different bit juxtapositions; determining the level of transition shift for each of said plurality of different bit juxtapositions; reading data stored on said medium; and compensating said read data bits for transition shift by varying the duration of said symbol cells in accordance with said determined transition shift.

Claim 24

A method of compensating for transition shift in a magnetic storage medium comprising the steps of: recording on a portion of said magnetic medium a plurality of different bit juxtapositions; recording the order in which said plurality of relative bit juxtaposition are recorded; reading from said medium the order in which said bit juxtapositions are recorded; reading from said medium the plurality of different bit juxtapositions; determining the level of transition shift for each of said plurality of different bit juxtapositions; reading data stored on said medium; and compensating said read data bits for transition shift by varying the duration of said symbol cells in accordance with said determined transition shift.

Claim 25

A method of storing data on a recording medium comprising the steps of: grouping digital binary signals into chunks of N bits, wherein N is an integer number greater than 1; determining the value of each of said N bit chunks; converting said N bit chunks to a corresponding symbol cell, each of said symbol cells having a duration which is dependent upon the value of the corresponding N bit chunk; and recording on a portion of said magnetic medium a plurality of relative symbol cell juxtapositions; recording the order in which said plurality of relative symbol cell juxtapositions are recorded; reading from said medium the order in which said symbol cell juxtapositions are recorded; reading from said medium the plurality of symbol cell juxtapositions; determining the level of transition shift for each of said plurality of symbol cell juxtapositions; reading data stored in a form of said symbol cells from said medium; and compensating said read data symbol cells for transition shift by varying the duration of said symbol cells in accordance with said determined said transition shift.

Claim 26

A method of storing data on a recording medium comprising the steps of: grouping digital binary signals into chunks of N bits, wherein N is an integer number greater than 1; determining the value of each of said N bit chunks; converting said N bit chunks to a corresponding symbol cell, each of said symbol cells having a duration which is dependent upon the value of the corresponding N bit chunk; and recording on a portion of said magnetic medium a plurality of relative symbol cell juxtapositions; recording the order in which said plurality of relative symbol cell juxtapositions are recorded; reading from said medium the order in which said symbol cell juxtapositions are recorded; reading from said medium the plurality of symbol cell juxtapositions; determining the level of transition shift for each of said plurality of symbol cell juxtapositions; reading data stored in a form of said symbol cells from said medium; and compensating said read data symbol cells for transition shift by varying the duration of said symbol cells in accordance with said determined said transition shift.

Claim 29

A method of storing data on a recording medium comprising the steps of: recording a plurality of different bit juxtapositions onto a magnetic medium; determining from said recorded bit juxtapositions the transition shift for each of said juxtapositions of bits; compensating said bits for transition shift by varying the duration thereof; recording bits of data on said recording medium by precompensating said bits in accordance with the determined transition shift of said plurality of bits shift juxtapositions; recording the order in which said plurality of different bit juxtapositions are recorded onto said magnetic medium; reading from said medium the order in which said bit juxtapositions are recorded; reading from said medium the plurality of recorded bits of data; determining the level of transition shift for each of said plurality of different bit juxtapositions; reading said recorded bits of data from said medium; and compensating said read data bits for transition shift by varying the duration of said bits in accordance with said determined transition shift.

Claim 30

A method of storing data on a recording medium comprising the steps of: recording a plurality of different bit juxtapositions onto a magnetic medium; determining from said recorded bit juxtapositions the transition shift for each of said juxtapositions of bits; compensating said bits for transition shift by varying the duration thereof; recording bits of data on said recording medium by precompensating said bits in accordance with the determined transition shift of said plurality of bits shift juxtapositions; recording the order in which said plurality of different bit juxtapositions are recorded onto said magnetic medium; reading from said medium the order in which said bit juxtapositions are recorded; reading from said medium the plurality of recorded bits of data; determining the level of transition shift for each of said plurality of different bit juxtapositions; reading said recorded bits of data from said medium; and compensating said read data bits for transition shift by varying the duration of said bits in accordance with said determined transition shift.

Claim 31

A method of storing data on a recording medium comprising the steps of: grouping ditigal binary signals into chunks of N bits, where N is an integer greater than 1; determining the value of each of said N bit chunks; converting said N bit chunks to a corresponding symbol cell, each of said symbol cells having an duration which is dependent upon the value of the corresponding N bit chunks; recording on a portion of said medium the relative symbol cell juxtapositions for at least two successive symbol cells; determining from said recorded symbol cell juxtapositions the transition shift for each of said juxtapositions of symbol cells; compensating said symbol cells for transition shift by varying the duration of said symbol cells; recording on a portion of said magnetic medium a plurality of relative symbol cell juxtapositions wherein said symbol cells are precompensated to reduce transition shift distortion; recording the order in which said plurality of relative symbol cell juxtapositions are recorded; reading from said medium the order in which said symbol cell juxtapositions are recorded; reading from said medium the plurality of symbol cell juxtapositions; determining the level of transition shift for each of said pluality of said symbol cell juxtapositions; reading data stored in the form of said symbol cells from said medium; and compensating said read data symbol cells for transition shift by varying the duration of said symbol cells in accordance with said determined transition shift.

Claim 32

A method of storing data on a recording medium comprising the steps of: grouping ditigal binary signals into chunks of N bits, where N is an integer greater than 1; determining the value of each of said N bit chunks; converting said N bit chunks to a corresponding symbol cell, each of said symbol cells having an duration which is dependent upon the value of the corresponding N bit chunks; recording on a portion of said medium the relative symbol cell juxtapositions for at least two successive symbol cells; determining from said recorded symbol cell juxtapositions the transition shift for each of said juxtapositions of symbol cells; compensating said symbol cells for transition shift by varying the duration of said symbol cells; recording on a portion of said magnetic medium a plurality of relative symbol cell juxtapositions wherein said symbol cells are precompensated to reduce transition shift distortion; recording the order in which said plurality of relative symbol cell juxtapositions are recorded; reading from said medium the order in which said symbol cell juxtapositions are recorded; reading from said medium the plurality of symbol cell juxtapositions; determining the level of transition shift for each of said pluality of said symbol cell juxtapositions; reading data stored in the form of said symbol cells from said medium; and compensating said read data symbol cells for transition shift by varying the duration of said symbol cells in accordance with said determined transition shift.

Claim 34

A system of storing data on a recording medium comprising: means for grouping digital binary signals into chunks of N bits wherein N is an integer number greater than 1; means for determining the value of each of said N bit chunks; means for converting sain N bit chunks to a corresponding symbol cell, each of said symbol cells having a duration which is dependent upon the value of the corresponding N bit chunk, and having a duration equal to the sum of the minimum transition period for the recording medium and an incremental time period, said incremental time period being directly proportional to the value of said N bit chunks, the maximum duration of said incremental time period being less than the time duration of the minimum transition period; and means for recording said symbol cells onto a recording medium.

Claim 35

A system of storing data on a recording medium comprising: means for grouping digital binary signals into chunks of N bits wherein N is an integer number greater than 1; means for determining the value of each of said N bit chunks; means for converting sain N bit chunks to a corresponding symbol cell, each of said symbol cells having a duration which is dependent upon the value of the corresponding N bit chunk, and having a duration equal to the sum of the minimum transition period for the recording medium and an incremental time period, said incremental time period being directly proportional to the value of said N bit chunks, the maximum duration of said incremental time period being less than the time duration of the minimum transition period; and means for recording said symbol cells onto a recording medium.

Claim 37

A system of storing data on a recording medium comprising: means for grouping binary input signals into chunks of N bits wherein N is an integer number greater than 1; means for determining the value of each of said N bit chunks; means for determining the relative frequency of occurrence of each of the values of said N bit chunks; means for assigning a symbol cell duration to each of said N bit chunks wherein the more frequently a value occurs, the shorter is the time duration assigned to the symbol cell; means for generating symbol cells for each N bit chunk in accordance with the symbol cell duration assigned thereto; and means for recording said symbol cells onto a recording medium.

Claim 38

A system of storing data on a recording medium comprising: means for grouping binary input signals into chunks of N bits wherein N is an integer number greater than 1; means for determining the value of each of said N bit chunks; means for determining the relative frequency of occurrence of each of the values of said N bit chunks; means for assigning a symbol cell duration to each of said N bit chunks wherein the more frequently a value occurs, the shorter is the time duration assigned to the symbol cell; means for generating symbol cells for each N bit chunk in accordance with the symbol cell duration assigned thereto; and means for recording said symbol cells onto a recording medium.

Claim 40

A system for storing data on a recording medium comprising: means for grouping binary signals into chunks of N bits wherein N is an integer greater than 1; means for determining the value of each of said N bit chunks; means for converting said N bit chunks to a corresponding symbol cell, each of said symbol cells having an assigned duration which is dependent upon the value of the corresponding N bit chunks; means for recording on a portion of said medium the relative symbol cell juxtapositions for three successive symbol cells; means for determining from said recorded symbol cell juxtapositions the transition shift for each of said juxtapositions of symbol cells; means for compensating said symbol cells to be stored for transition shift by varying the duration of said symbol cells in accordance with the determined transition shift of juxtaposed symbol cells.

Claim 41

A system for storing data on a recording medium comprising: means for grouping binary signals into chunks of N bits wherein N is an integer greater than 1; means for determining the value of each of said N bit chunks; means for converting said N bit chunks to a corresponding symbol cell, each of said symbol cells having an assigned duration which is dependent upon the value of the corresponding N bit chunks; means for recording on a portion of said medium the relative symbol cell juxtapositions for three successive symbol cells; means for determining from said recorded symbol cell juxtapositions the transition shift for each of said juxtapositions of symbol cells; means for compensating said symbol cells to be stored for transition shift by varying the duration of said symbol cells in accordance with the determined transition shift of juxtaposed symbol cells.

Claim 43

A system for storing data on a recording medium comprising: means for grouping binary signals into chunks of N bits wherein N is an integer greater than 1; means for determining the value of each of said N bit chunks; means for converting said N bit chunks to a corresponding symbol cell, each of said symbol cells having an assigned duration which is dependent upon the value of the corresponding N bit chunk; means for recording on a portion of said medium the relative symbol cell juxtapositions for at least two successive symbol cells; means for determining from said recorded symbol cell juxtapositions the transition shift for each of said juxtapositions of symbol cells; and means for adaptively precompensating for said transition shift by varying the duration of said symbol cells before recording and means for recording said symbol cells corresponding to said input data.

Claim 44

A system for storing data on a recording medium comprising: means for grouping binary signals into chunks of N bits wherein N is an integer greater than 1; means for determining the value of each of said N bit chunks; means for converting said N bit chunks to a corresponding symbol cell, each of said symbol cells having an assigned duration which is dependent upon the value of the corresponding N bit chunk; means for recording on a portion of said medium the relative symbol cell juxtapositions for at least two successive symbol cells; means for determining from said recorded symbol cell juxtapositions the transition shift for each of said juxtapositions of symbol cells; and means for adaptively precompensating for said transition shift by varying the duration of said symbol cells before recording and means for recording said symbol cells corresponding to said input data.

Claim 46

A system for storing data on a recording medium comprising: means for grouping digital binary signals into chunks of N bits wherein N is an integer number greater than 1; means for determining the value of each of said N bit chunks; means for converting said N bit chunks to a corresponding symbol cell, each of said symbol cells having duration which is dependent upon the value of the corresponding N bit chunk; means for recording on a portion of said magnetic medium a plurality of relative symbol cell juxtapositions; means for recording the order in which said plurality of relative symbol cell juxtapositions are recorded; means for reading from said medium the order in which said symbol cell juxtapositions are recorded; means for reading from said medium the plurality of symbol cell juxtapositions; means for determining the level of transition shift for each of said plurality of symbol cell juxtapositions; means for reading data stored in a form of said symbol cells from said medium; and means for compensating said read data symbol cells for transition shift by varying the durtion of said symbol cells in accordance with said determined transition shift.

Claim 47

A system for storing data on a recording medium comprising: means for grouping digital binary signals into chunks of N bits wherein N is an integer number greater than 1; means for determining the value of each of said N bit chunks; means for converting said N bit chunks to a corresponding symbol cell, each of said symbol cells having duration which is dependent upon the value of the corresponding N bit chunk; means for recording on a portion of said magnetic medium a plurality of relative symbol cell juxtapositions; means for recording the order in which said plurality of relative symbol cell juxtapositions are recorded; means for reading from said medium the order in which said symbol cell juxtapositions are recorded; means for reading from said medium the plurality of symbol cell juxtapositions; means for determining the level of transition shift for each of said plurality of symbol cell juxtapositions; means for reading data stored in a form of said symbol cells from said medium; and means for compensating said read data symbol cells for transition shift by varying the durtion of said symbol cells in accordance with said determined transition shift.

Claim 49

A system of storing data on a recording medium comprising: means for grouping digital binary signals into chunks of N bits, where N is an integer greater than 1; means for determining the value of each of said N bit chunks; means for converting said N bit chunks to a corresponding symbol cell, each of said symbol cells having a duration which is dependent upon the value of the corresponding N bit chunks; means for recording on a portion of said medium the relative symbol cell juxtapositions for at least two successive symbol cells; means for determining from said recorded symbol cell juxtapositions the transition shift for each of said juxtapositions of symbol cells; means for compensating said symbol cells for transition shift by varying the duration of said symbol cells; means for recording on a portion of said magnetic media a plurality of relative symbol cell juxtapositions wherein said symbol cells are precompensated to reduce transition shift distortion; means for recording the order in which said plurality of relative symbol cell juxtapositions are recorded; means for reading from said medium the order in which said symbol cell juxtapositions are recorded and the plurality of symbol cell juxtapositions; means for determining the level of transition shift for each of said plurality of said symbol cell juxtapositions; means for reading data stored in the form of said symbol cells from said medium; and means for compensating said read data symbol cells for transition shift by varying the duration of said symbol cells in accordance with said determined transition shift.

Claim 50

A system of storing data on a recording medium comprising: means for grouping digital binary signals into chunks of N bits, where N is an integer greater than 1; means for determining the value of each of said N bit chunks; means for converting said N bit chunks to a corresponding symbol cell, each of said symbol cells having a duration which is dependent upon the value of the corresponding N bit chunks; means for recording on a portion of said medium the relative symbol cell juxtapositions for at least two successive symbol cells; means for determining from said recorded symbol cell juxtapositions the transition shift for each of said juxtapositions of symbol cells; means for compensating said symbol cells for transition shift by varying the duration of said symbol cells; means for recording on a portion of said magnetic media a plurality of relative symbol cell juxtapositions wherein said symbol cells are precompensated to reduce transition shift distortion; means for recording the order in which said plurality of relative symbol cell juxtapositions are recorded; means for reading from said medium the order in which said symbol cell juxtapositions are recorded and the plurality of symbol cell juxtapositions; means for determining the level of transition shift for each of said plurality of said symbol cell juxtapositions; means for reading data stored in the form of said symbol cells from said medium; and means for compensating said read data symbol cells for transition shift by varying the duration of said symbol cells in accordance with said determined transition shift.

Claim 51

A system for compensating for transition shift in a magnetic storage medium comprising the steps of: means for recording on a portion of said magnetic medium a plurality of relative symbol cell juxtapositions wherein said symbol cells are precompensated to reduce transition shift distortion; means for recording the order in which said plurality of relative symbol cell juxtapositions are recorded; means for reading from said medium the order in which said symbol cell juxtapositions are recorded; means for reading from said medium the plurality of symbol cell juxtapositions; means for determining the level of transition shift for each of said plurality of symbol cell juxtapositions; means for reading data stored in the form of said symbol cells from said medium; and means for compensating said read data symbol cells for transition shift by varying the duration of said symbol cells in accordance with said determined transition shift.

Claim 52

A system for compensating for transition shift in a magnetic storage medium comprising the steps of: means for recording on a portion of said magnetic medium a plurality of relative symbol cell juxtapositions wherein said symbol cells are precompensated to reduce transition shift distortion; means for recording the order in which said plurality of relative symbol cell juxtapositions are recorded; means for reading from said medium the order in which said symbol cell juxtapositions are recorded; means for reading from said medium the plurality of symbol cell juxtapositions; means for determining the level of transition shift for each of said plurality of symbol cell juxtapositions; means for reading data stored in the form of said symbol cells from said medium; and means for compensating said read data symbol cells for transition shift by varying the duration of said symbol cells in accordance with said determined transition shift.