Method and apparatus for generating look-up table data in the video picture field

Claim 2

Method according to claim 1, characterized in that said look-up table data can be approximated by a piecewise linear function of a variable (S(VAL)) depending on the given value and that it comprises the following steps: dividing the set of N values into P subsets of consecutive values, each piece of the piecewise linear function being in a different subset; defining a look-up table for the two bound values of each subset i, called primary look-up table (PMTC i ) and secondary look-up table (SMTC i ) respectively, each of said primary and secondary look-up tables comprising an output data (PMTC, SMTC) for each possible input video data (YI), defining, for each subset i, a delta look-up table corresponding to the difference between the secondary look-up table (SMTC i ) and the primary look-up table (PMTC i ) related to the subset i, defining, for each one of said N values, an extrapolation coefficient (C(VAL)) in accordance with the value (S(VAL)) of a variable S for the given value (VAL) and the values (S(PMTC i ),S(SMTC i )) of the variable S for the two bound values of the subset i comprising the given value; and computing the look-up table data for said input video data (Yl) and for the given value (VAL) in accordance with the extrapolation coefficient (C(VAL)) defined for the given value (VAL) and the output data of the primary look-up table (PMTC i ) and the delta look-up table for said for said input video data (YI).

Claim 3

Method according to claim 2, characterized in that the look-up table data is a Metacode look-up table data, the parameter is an average power level and the variable (S(VAL)) is a number of sustain pulses corresponding to the given value (VAL) of the parameter.

Claim 4

Method according to claim 3, characterized in that the bound level related to the primary look-up table (PMTC i ) of a subset of average power level values is the highest average power level value of the subset and the bound level related to the secondary look-up table (SMTC i ) of a subset of average power level values is the lowest average power level value of the subset.

Claim 5

Method according to one of the claims 2 to 4, characterized in that the ratio between the value (S(PMTC i )) of the variable for one bound value in the subset i and the value (S(PMTC i+1 )) of the variable for the same bound value in the subset i+1 equals to a fixed parameter

Claim 6

Method according to the claim 5, characterized in that the parameter α is defined as followed : where S MAX is the value of the variable (S) for a peak white image and S MIN is the value of the variable (S) for a full white image.

Claim 7

Method according to one of the claims 2 to 6, characterized in that the extrapolation coefficient (C(VAL)) is proportional to: S(VAL) - S(PMTC i ) S(SMTC i )-S(PMTC i ) where S(PMTC i ) is the value of the variable for the highest bound value of the subset i; S(SMTC i ) is the value of the variable for the lowest bound value of the subset i; and S(VAL) is the value of the variable for the given value.

Claim 8

Method according to one of the claims 2 to 7, characterized in that the computed look-up table data equals to the sum of the output data of the primary look-up table (PMTC i ) and the output data of the delta look-up table (PMTC i ) for said input video data (YI) and the given value (VAL) weighted by the extrapolation coefficient for the given value (VAL).

Claim 9

Device for generating a look-up table data for an input video data (Yl) and for a given value (VAL) of a parameter (APL) among N different values, said output data being approximated by a piecewise linear function of a variable (S(VAL)) depending on the given value, the set of N values being divided into P subsets of consecutive values, each piece of the piecewise linear function being in a different subset, characterized in that it,comprises: a first memory (101) for storing, for each subset i, a primary look-up table (PMTC i ) associated to a bound value of the subset i and comprising an output data (PMTC) for each possible input video data (YI), a second memory (102) for storing, for each subset i, a delta look-up table corresponding to the difference between a secondary look-up table (SMTC i ) and the primary look-up table (PMTC i ) related to the subset i, the secondary look-up table (SMTC i ) being associated to the other bound value of the subset i and comprising an output data (SMTC) for each possible input video data (YI),, a third memory (103) for storing, for each of said N values, an index indicating which primary look-up table in the first memory (101) and which delta look-up table in the second memory (102) have to be used for extrapolation, a fourth memory (104) for storing an extrapolation coefficient (C) for each one of said N values, the extrapolation coefficient (C(VAL)) associated to a given value being defined in accordance with the value (S(VAL)) of a variable S for said given value (VAL) and the values (S(PMTC i ),S(SMTC i )) of the variable S for the two bound values of the subset i comprising said given value; and a computing block (105) for generating a look-up table data for said input video data (Yl) and for the given value (VAL) in accordance with the extrapolation coefficient (C(VAL)) defined for the given value (VAL) and the output data of the primary look-up table (PMTC i ) and the delta look-up table for said input video data (YI).

Claim 10

Device according to claim 9, characterized in that the parameter is an average power level and the variable (S(VAL)) is a number of sustain pulses corresponding to the given value (VAL) of the parameter and that it generates a Metacode look-up table data for each average power level value.

Claim 11

Device according to claim 10, characterized in that the bound level related to the primary look-up table (PMTC i ) of a subset of average power level values is the highest average power level value of the subset and the bound level related to the secondary look-up table (SMTC i ) of a subset of average power level values is the lowest average power level value of the subset.

Claim 12

Device according to one of the claims 9 to 11, characterized in that the ratio between the value (S(PMTC i )) of the variable for one bound value in the subset i and the value (S(PMTC i+1 )) of the variable for the same bound value in the subset i+1 equals to a fixed parameter α.

Claim 13

Device according to the claim 12, characterized in that the parameter α is defined as followed : where S MAx is the value of the variable (S) for a peak white image and S MIN is the value of the variable (S) for a full white image.

Claim 14

Device according to one of the claims 9 to 13, characterized in that the extrapolation coefficient (C(VAL)) is proportional to : S(VAL) - S(PMTC i ) S(SMTC i )-S(PMTC i ) where S(PMTC i ) is the value of the variable for the highest bound value of the subset i; S(SMTC i ) is the value of the variable for the lowest bound value of the subset i; and S(VAL) is the value of the variable for the given value

Claim 15

Device according to one of the claims 9 to 14, characterized in that the look-up table data computed by the computing block (105) equals to the sum of the output data of the primary look-up table (PMTC i ) and the output data of the delta look-up table (PMTC i ) for said input video data (YI) the given value (VAL) weighted by the extrapolation coefficient for the given value (VAL).