Image coding apparatus

Abstract

An image coding technique for suppressing degradation in image quality, in which the time and space where intra macroblocks appear are dispersed. A block count determination part determines the number of intra macroblocks to be allocated in each frame. A position determination part arranges the intra macroblocks at random positions in each frame. A coding part performs coding on the basis of the number of intra macroblocks to be allocated in a time direction, which is determined by the block count determination part, and the arrangement of the intra macroblocks in a spatial direction, which is determined by the position determination part, to thereby output compressed image data.

1 . An image coding apparatus, comprising:
 a block count determination part for determining the number of intra macro blocks to be included in each frame;   a position determination part for determining respective spatial positions of said intra macroblocks to be included in said each frame in said frame; and   a coding part for arranging said intra macroblocks, the number of which is determined by said block count determination part, in said each frame on the basis of said positions determined by said position determination part, to thereby perform coding,   wherein said position determination part arranges said intra macroblocks to be included in said each frame at random positions in said frame.   
     
     
         2 . The image coding apparatus according to  claim 1 , wherein
 one frame consists of M macroblocks and each of said macroblocks is intra-coded once in N frames, and   said block count determination part determines the number of intra macroblocks to be allocated to said each frame so that said M intra macroblocks evenly appear in said N frames.   
     
     
         3 . The image coding apparatus according to  claim 2 , wherein
 said block count determination part determines the number of intra macroblocks to be allocated to said each frame so that the difference in the number of intra macroblocks appearing in said each frame among said frames is at most 1.   
     
     
         4 . The image coding apparatus according to  claim 2 , wherein
 said block count determination part allocates S intra macroblocks to each frame when M is an integral multiple of N and it is assumed that the quotient of M divided by N is S, and   said block count determination part allocates S intra macroblocks to each of (N−R) frames and allocates (S+1) intra macroblocks to each of R frames when M is not an integral multiple of N and it is assumed that M divided by N gives S as a quotient, leaving R as a remainder.   
     
     
         5 . The image coding apparatus according to  claim 4 , wherein
 said block count determination part disposes said frames each including (S+1) intra macroblocks at a rate of one in D frames when N is an integral multiple of R and it is assumed that the quotient of N divided by R is D, and   said block count determination part disposes (R−Q) frames each including (S+1) intra macroblocks at an interval of D frames and disposes Q frames each including (S+1) intra macroblocks at an interval of (D+1) frames when N is not an integral multiple of R and it is assumed that N divided by R gives D as a quotient, leaving Q as a remainder.   
     
     
         6 . The image coding apparatus according to  claim 5 , wherein
 said block count determination part mixedly arranges frames A which are disposed at an interval of (D+1) frames and frames B which are disposed at an interval of D frames among R frames each including (S+1) intra macroblocks so that dispersion of frame interval of said frames A becomes as small as possible.   
     
     
         7 . The image coding apparatus according to  claim 4 , wherein
 said block count determination part arranges said intra macroblocks so that the ratio of said intra macroblocks is higher in the first half of a GOP.   
     
     
         8 . An image coding apparatus, comprising:
 a position determination part for determining respective spatial positions of intra macroblocks to be included in each frame in said frame; and   a coding part for arranging said intra macroblocks in said each frame on the basis of said positions determined by said position determination part, to thereby perform coding,   wherein said position determination part arranges said intra macroblocks so that there is a difference in the motion of said intra macroblocks in a time direction between even-numbered frames and odd-numbered frames.