moving picture coding method and a moving picture decoding method

Abstract

A moving picture coding apparatus includes a motion estimation unit ( 101 ) for performing motion estimation by fixing the one of two reference pictures as a reference picture indicated by an inputted default reference picture number DefRefNo and a variable length coding unit ( 107 ) for performing variable length coding on coded residual data ERes, a prediction type PredType, a reference picture number RefNo 2 and motion vectors MV 1, MV 2 on a block-by-block basis, and outputting them as coded moving picture data Str.

1 - 2 . (canceled) 
     
     
         3 . A picture coding method for dividing a current picture to be coded into blocks, selecting a reference picture from among reference pictures on a block basis, describing information which identifies the selected reference picture, and performing predictive coding onto the block, said method comprising:
 judging if a common reference picture is to be selected or not when coding a plural-block image unit made up of a plurality of blocks;   selecting, if it is judged that a common reference picture is to be selected, one common reference picture to be commonly referred to, from among plural reference pictures, the common reference picture being only one reference picture that is selected from among the plural reference pictures and is assigned commonly to each of the plurality of blocks of the plural-block image unit;   describing common information which identifies the selected common reference picture, in a common information area for the plural-block image unit such that reference picture identification information for the selected common reference picture can be omitted for at least one of the plurality of blocks of the plural-block image unit, instead of describing per block, reference picture identification information which identifies the selected common reference picture;   generating a predictive image of a current block to be coded included in the plural-block image unit, using the selected common reference picture; and   coding the current block using the predictive image.