Moving picture prediction method, moving picture coding method and apparatus, and moving picture decoding method and apparatus
An image decoding method is provided which includes a time information determination step of determining time information of a current picture, a first reference picture referred to by the current picture and a second reference picture referred to by the current picture; a scaling parameter calculation step of calculating a scaling parameter based on a time distance between the first reference picture and a second reference picture; a weighting coefficient determination step of determining two weighting coefficients based on the scaling parameter; a predictive pixel value generation step of generating a predictive pixel value of the current picture 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 in the weighting coefficient determination step; and a decoding step of decoding the current picture using the predictive pixel value.
1. 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 and second parameters calculation unit configured to:
calculate a first parameter corresponding to a distance between an input picture to be coded and a first reference picture referred to by a current block to be coded that is included in the input picture, and
calculate a second parameter corresponding to a distance between the first reference picture and a second reference picture referred to by the current block to be coded;
a first judgment unit configured to judge whether or not a value of a third parameter calculated based on a ratio between the first parameter and the second parameter is included in a predetermined range;
a first predictive pixel value calculation unit configured to:
calculate a predictive pixel value of the current block to be coded by scaling a pixel value of the first reference picture using one of two weighting coefficients and scaling a pixel value of the second reference picture using the other of the two weighting coefficients, the two weighting coefficients being calculated using the first and second parameters, when the value of the third parameter is included in the predetermined range, and
calculate a predictive pixel value of the current block to be coded by scaling a pixel value of the first reference picture and a pixel value of the second reference picture using two weighting coefficients, the two weighting coefficients having a same predetermined value, when the value of the third parameter is not included in the predetermined range;
a difference value coding unit configured to code a difference value between a pixel value of the current block and the calculated predictive pixel value of the current block to output coded data of the current block,
wherein said picture decoding apparatus includes:
a first parameter calculation unit configured to calculate a first parameter corresponding to a distance between a current picture to be decoded and a first reference picture referred to by a current block to be decoded that is included in the current picture to be decoded;
a second parameter calculation unit configured to calculate a second parameter corresponding to a distance between the first reference picture and a second reference picture referred to by the current block to be decoded;
a second judgment unit configured to judge whether or not a value of a third parameter calculated based on a ratio between the first parameter and the second parameter is included in a predetermined range;
a predictive pixel value generation unit configured to:
calculate a predictive pixel value of the current block to be decoded by scaling a pixel value of the first reference pictures using one of two weighting coefficients and scaling a pixel value of the second reference picture using the other of the two weighting coefficients, the two weighting coefficients being calculated using the first and second parameters, when the value of the third parameter is included in the predetermined range, and
calculate a predictive pixel value of the current block to be decoded by scaling a pixel value of the first reference picture and a pixel value of the second reference picture using two weighting coefficients, the two weighting coefficients having a same predetermined value, when the value of the third parameter is not included in the predetermined range;
a difference value decoding unit configured to decode coded data of the current block to be decoded to obtain a decoded difference value of the current block to be decoded; and
a block reconstructing unit configured to reconstruct a pixel value of the current block by adding the decoded difference value of the current block and the predictive pixel value of the current block calculated by said predictive pixel value generation unit.
2. The picture coding and decoding system according to claim 1 ,
wherein each of the distance between the input picture to be coded and the first reference picture, the distance between the first reference picture and the second reference picture, the distance between the current picture to be decoded and the first reference picture, and the distance between the first reference picture and the second reference picture is a temporal distance.