Moving picture coding method and moving picture decoding method

A picture coding method comprising:

• generating commands indicating correspondence between reference pictures and reference indices designating the reference pictures;
• determining a maximum value of the reference indices;
• determining a weighting coefficient set for a reference index so as to determine a plurality of weighting coefficient sets for the reference indices;
• assigning a reference index to a reference picture, the reference picture being referred to when motion compensation is performed on a current block to be coded;
• generating a predictive image by performing linear prediction on pixel values of a reference block, using the weighting coefficient set corresponding to the assigned reference index, the reference block being obtained by motion estimation between the reference picture and the current block to be coded;
• generating a prediction error that is a difference between the current block to be coded and the predictive image;
• and
• outputting a coded image signal obtained by coding:
• the reference index assigned to the reference picture in said assigning;
• information indicating the maximum value of the reference indices;
• the commands;
• the weighting coefficient sets;
• and the prediction error,
• wherein, information of said weighting coefficient sets used for said generating of a predictive image are placed in a slice header of the coded image signal, and
• in the case that the current block is a block included in a P picture and the current block is coded by designating one reference picture which is referred to, each of said weighting coefficient sets comprises a first part w1 and a second part c1, the first part w1 being used for scaling pixel values of the reference block and the second part c1 being used for increasing each of the scaled pixel values by a value of c1.

A picture coding apparatus comprising:

• a command generation unit operable to generate commands indicating correspondence between reference pictures and reference indices designating the reference pictures;
• a maximum value determination unit operable to determine a maximum value of the reference indices;
• a weighting coefficient set determination unit operable to determine a weighting coefficient set for a reference index so as to determine a plurality of weighting coefficient sets for the reference indices;
• a reference index assigning unit operable to assign a reference index to a reference picture, the reference picture being referred to when motion compensation is performed on a current block to be coded;
• a predictive image generation unit operable to generate a predictive image by performing linear prediction on pixel values of a reference block, using the weighting coefficient set corresponding to the assigned reference index, the reference block being obtained by motion estimation between the reference picture and the current block to be coded;
• a prediction error generating unit operable to generate a prediction error that is a difference between the current block to be coded and the predictive image;
• and
• a coded image signal outputting unit operable to output a coded image signal obtained by coding:
• the reference index assigned to the reference picture in said assigning;
• information indicating the maximum value of the reference indices;
• the commands;
• the weighting coefficient sets;
• and the prediction error,
• wherein, information of said weighting coefficient sets determined by said weighting coefficient set determination unit are placed in a slice header of the coded image signal, and
• in the case that the current block is a block included in a P picture and the current block is coded by designating one reference picture which is referred to, each of said weighting coefficient sets comprises a first part w1 and a second part c1, the first part w1 being used for scaling pixel values of the reference block and the second part c1 being used for increasing each of the scaled pixel values by a value of c1.

A non-transitory computer-readable medium having a program stored thereon for causing a computer to perform a picture coding method, the picture coding method comprising:

• generating commands indicating correspondence between reference pictures and reference indices designating the reference pictures;
• determining a maximum value of the reference indices;
• determining a weighting coefficient set for a reference index so as to determine a plurality of weighting coefficient sets for the reference indices;
• assigning a reference index to a reference picture, the reference picture being referred to when motion compensation is performed on a current block to be coded;
• generating a predictive image by performing linear prediction on pixel values of a reference block, using the weighting coefficient set corresponding to the assigned reference index, the reference block being obtained by motion estimation between the reference picture and the current block to be coded;
• generating a prediction error that is a difference between the current block to be coded and the predictive image;
• and
• outputting a coded image signal obtained by coding:
• the reference index assigned to the reference picture in said assigning;
• information indicating the maximum value of the reference indices;
• the commands;
• the weighting coefficient sets;
• and the prediction error,
• wherein, information of said weighting coefficient sets used for said generating of a predictive image are placed in a slice header of the coded image signal, and
• in the case that the current block is a block included in a P picture and the current block is coded by designating one reference picture which is referred to, each of said weighting coefficient sets comprises a first part w1 and a second part c1, the first part w1 being used for scaling pixel values of the reference block and the second part c1 being used for increasing each of the scaled pixel values by a value of c1.