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

Abstract

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 time information determination unit operable to determine time information of a current B picture to be coded, a first reference picture referred to by the current B picture to be coded and a second reference picture referred to by the current B picture to be coded;   a first weighting coefficient determination unit operable to determine two weighting coefficients based on the time information determined by said first time information determination unit;   a first predictive pixel value generation unit operable to generate a predictive pixel value for a target block included in the current B 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 target block and the predictive pixel value generated 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 B picture to be decoded, a first reference picture referred to by the current B picture to be decoded and a second reference picture referred to by the current B picture to be decoded;   a second weighting coefficient determination unit operable to determine two weighting coefficients based on the time information determined by said second time information determination unit;   a second predictive pixel value generation unit operable to generate a predictive pixel value for a target block included in the current B 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;   a difference value decoding unit operable to decode a difference value between the target block included in the current B picture to be decoded and the predictive pixel value generated by said second predictive pixel value generation unit; and   a block decoding unit operable to reconstruct the target block by adding a difference value decoded by said difference value decoding unit and 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 ½ 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 in accordance with time information of the current B picture to be decoded, the first reference picture referred to by the current B picture to be decoded and the second reference picture referred to by the current B picture to be decoded 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.   
     
     
         2 . A picture coding and decoding method which includes a picture coding method for coding a picture on a block basis and a picture decoding method for decoding a coded picture on a block basis,
 wherein said picture coding method comprises:   a first time information determination step of determining time information of a current B picture to be coded, a first reference picture referred to by the current B picture to be coded and a second reference picture referred to by the current B picture to be coded;   a first weighting coefficient determination step of determining two weighting coefficients based on the time information determined in said first time information determination step;   a first predictive pixel value generation step of generating a predictive pixel value for a target block included in the current B 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 in said first weighting coefficient determination step; and   a coding step of coding a difference value between the target block and the predictive pixel value generated in said first predictive pixel value generation step, and   wherein said picture decoding method comprises:   a second time information determination step of determining time information of a current B picture to be decoded, a first reference picture referred to by the current B picture to be decoded and a second reference picture referred to by the current B picture to be decoded;   a second weighting coefficient determination step of determining two weighting coefficients based on the time information determined in said second time information determination step;   a second predictive pixel value generation step of generating a predictive pixel value for a target block included in the current B 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 in said second weighting coefficient determination step;   a difference value decoding step of decoding a difference value between the target block included in the current B picture to be decoded and the predictive pixel value generated in said second predictive pixel value generation step; and   a block decoding step of reconstructing the target block by adding a difference value decoded in said difference value decoding step and the predictive pixel value generated in said second predictive pixel value generation step,   wherein the second weighting coefficient determination step further includes the steps of:   (i) determining the two weighting coefficients to be a predetermined value of ½ in a case that a generation of the predictive pixel value cannot be performed within a predetermined significant bit number in said second predictive pixel value generation step, and   (ii) determining the two weighting coefficients in accordance with time information of the current B picture to be decoded, the first reference picture referred to by the current B picture to be decoded and the second reference picture referred to by the current B picture to be decoded in a case that the generation of the predictive pixel value can be performed within the predetermined significant bit number in said second predictive pixel value generation step.