Patent ID: 8422807

Claim:
An encoder, comprising: at least one processing circuit configured to implement a difference calculator configured to calculate a differential block between a coding object block and a prediction block for each of a plurality of patterns of predictive coding processes; a frequency component calculator configured to, for each differential block of the plurality of patterns of predictive coding processes, orthogonally transform said respective differential block to calculate a frequency component block; a factor multiplier configured to, for each frequency component block of the plurality of patterns of predictive coding processes, multiply each frequency component in said respective frequency component block by a corresponding conversion factor included in a conversion factor matrix corresponding to the respective one of the plurality of patterns of predictive coding processes on which a magnitude relation of quantization steps is reflected, the corresponding conversion factor matrix being calculated from, and different from, a quantization matrix used to perform coding by the respective one of the predictive coding processes; a cost calculator configured to, for each frequency component block of the plurality of patterns of predictive coding processes, add up said frequency components in said respective frequency component block, each of which is multiplied by said corresponding conversion factor, to obtain a coding cost; and a selector configured to select the one of the predictive coding processes for which said coding cost is minimum, wherein said factor multiplier is configured to, for each frequency component block of the plurality patterns of predictive coding processes, use a value calculated on the basis of a relation between a correction factor set for each frequency component in said quantization matrix and a correction factor set for a DC component in said quantization matrix, as said conversion factors.