Motion vector coding method and motion vector decoding method

Abstract

A motion vector coding unit 117 executes processing including a neighboring block specification step (S 100 ) of specifying a neighboring block which is located in the neighborhood of a current block; a judgment step (Steps S 102, S 104 ) of judging whether or not the neighboring block has been coded using a motion vector of another block; a prediction step (S 106, S 108 ) of deriving a predictive motion vector of the current block using a motion vector calculated from the motion vector of the other block as a motion vector of the neighboring block; and a coding step (S 110 ) of coding the motion vector of the current block using the predictive motion vector.

The invention claimed is: 
     
       1. A motion vector decoding method for decoding a coded motion vector of a current block in a moving picture, comprising:
 specifying a three neighboring block blocks which is are located in a neighborhood of the current block and is are previously decoded; 
 deriving a predictive motion vector of the current block; and  
 decoding the coded motion vector of the current block using the predictive motion vector; to derive a final motion vector of the current block, wherein deriving the final motion vector of the current block comprises:
 adding the predictive motion vector of the current block to a decoded difference motion vector of the current block to derive the final motion vector of the current block, 
 
 wherein, in the deriving of the predictive motion vector of the current block, when comprises:
 responsive to determining that at least one of the three neighboring block blocks is decoded based on a motion vector of another block coded in a skip mode or a direct mode, deriving the predictive motion vector of the current block is derived based on the a motion vector of the another block different from the three neighboring blocks, and 
 responsive to determining that none of the three neighboring blocks are coded in the skip mode or the direct mode, deriving the predictive motion vector of the current block based on one or more motion vectors of the three neighboring blocks. 
 
 
     
     
       2. The motion vector decoding method according to  claim 1 , wherein the another block is located temporally at a forward or backward position relatively to one of the three neighboring block blocks. 
     
     
       3. The motion vector decoding method according to  claim 1 , wherein the another block is located in the moving picture including the three neighboring block blocks. 
     
     
       4. The motion vector decoding method according to claim 1, wherein the another block is located temporally at a forward position relatively to one of the three neighboring blocks. 
     
     
       5. The method of claim 1, further comprising generating a motion compensation image for the current block based on the final motion vector of the current block. 
     
     
       6. The method of claim 1, wherein deriving the predictive motion vector of the current block based on one or more motion vectors of the three neighboring blocks comprises deriving the predictive motion vector based on a median calculated from components of the one or more motion vectors of the three neighboring blocks. 
     
     
       7. A motion vector decoding method for decoding a coded motion vector of a current block in a moving picture, comprising:
 specifying three neighboring blocks which are located in a neighborhood of the current block and are previously decoded;   deriving, using one or more processing devices, a predictive motion vector of the current block;   decoding, using the one or more processing devices, the coded motion vector of the current block using the predictive motion vector to derive a final motion vector of the current block, wherein deriving the final motion vector of the current block comprises:
 adding the predictive motion vector of the current block to a decoded difference motion vector of the current block to derive the final motion vector of the current block, 
   wherein, deriving the predictive motion vector of the current block comprises:
 responsive to determining that at least one of the three neighboring blocks is coded in a skip mode or a direct mode, deriving the predictive motion vector of the current block based on a motion vector of another block different from the three neighboring blocks, and 
 responsive to determining that none of the three neighboring blocks are coded in the skip mode or the direct mode, deriving the predictive motion vector of the current block based on one or more motion vectors of the three neighboring blocks; and 
   storing results of the decoding in a tangible storage device.