Moving picture prediction method, moving picture coding method and apparatus, and moving picture decoding method and apparatus

A picture coding and decoding system which includes a picture coding apparatus that codes a picture on a block basis and a picture decoding apparatus that decodes a coded picture on a block basis,

• wherein said picture coding apparatus includes:
• a first time information determination unit operable to determine time information of a current picture to be coded, a first reference picture referred to by the current picture to be coded and a second reference picture referred to by the current picture to be coded;
• a first scaling parameter calculation unit operable to calculate a scaling parameter based on a temporal distance between the first reference picture and the second reference picture;
• a first weighting coefficient determination unit operable to determine two weighting coefficients based on the scaling parameter;
• a first predictive pixel value generation unit operable to generate a predictive pixel value of the current picture to be coded by scaling a pixel value of the first reference picture and a pixel value of the second reference picture using the two weighting coefficients determined by said first weighting coefficient determination unit;
• and
• a coding unit operable to code a difference value between the current picture and the predictive pixel value generated by said first predictive pixel value generation unit,
• wherein the first weighting coefficient determination unit is further operable to:
• (i) determine the two weighting coefficients to be a predetermined value of 1/2 in a case that a generation of the predictive pixel value cannot be performed within a predetermined significant bit number by said first predictive pixel value generation unit, and
• (ii) determine the two weighting coefficients to be a value calculated using the scaling parameter in a case that the generation of the predictive pixel value can be performed within the predetermined significant bit number by said first predictive pixel value generation unit, and
• wherein said picture decoding apparatus includes:
• a second time information determination unit operable to determine time information of a current picture to be decoded, a first reference picture referred to by the current picture to be decoded and a second reference picture referred to by the current picture to be decoded;
• a second scaling parameter calculation unit operable to calculate a scaling parameter based on a temporal distance between the first reference picture and the second reference picture;
• a second weighting coefficient determination unit operable to determine two weighting coefficients based on the scaling parameter;
• a second predictive pixel value generation unit operable to generate a predictive pixel value of the current picture to be decoded by scaling a pixel value of the first reference picture and a pixel value of the second reference picture using the two weighting coefficients determined by said second weighting coefficient determination unit;
• and
• a decoding unit operable to decode the current picture to be decoded using the predictive pixel value generated by said second predictive pixel value generation unit,
• wherein the second weighting coefficient determination unit is further operable to:
• (i) determine the two weighting coefficients to be a predetermined value of 1/2 in a case that a generation of the predictive pixel value cannot be performed within a predetermined significant bit number by said second predictive pixel value generation unit, and
• (ii) determine the two weighting coefficients to be a value calculated using the scaling parameter in a case that the generation of the predictive pixel value can be performed within the predetermined significant bit number by said second predictive pixel value generation unit.