Method of coding and decoding image

A video decoder comprising:

• a memory for storing a decoded image of a reference frame;
• and
• a predicted image synthesizing unit for synthesizing a predicted image of a present frame by using said decoded image and the information related to said present frame,
• wherein said predicted image synthesizing unit comprises:
• means for calculating motion vectors of 3 representative points having coordinates (i,j), (i+p,j), and (i,j+p) using motion vectors of corner points of said predicted image having coordinates (0,0), (r,0), and (0,s), where r, s, i, and j are integers, p and q are integer powers of 2, p is greater than or equal to r, p/2 is less than r, q is greater than or equal to s, q/2 is less than s, and the sampling intervals of pixels are 1 in both horizontal and vertical directions;
• means for calculating the motion vector of each pixel in said predicted image from said motion vectors of said representative points;
• and
• means for synthesizing said predicted image from said motion vector of each pixel and said decoded image, wherein:
• the horizontal and vertical components of said motion vectors of said corner points are integer multiples of 1/n;
• the horizontal and vertical components of said motion vector of each pixel in said predicted image are integer multiples of 1/m;
• the horizontal and vertical components of said motion vectors of said representative points are integer multiples of 1/k;
• in said means for calculating motion vectors of 3 representative points, said motion vectors of 3 representative points are calculated using equations:
• u′(x,y)=((u00rs+(u01−u00))xs+(u02−u00)yr)k)//(rsn),
• v′(x,y)=((v00rs+(v01−v00))xs+(v02−v00)yr)k)//(rsn),
• u0=u′(i,j), v0=v′(i,j), u1=u′(i+p,j), v1=v′(i+p,j),
• u2=u′(i,j+q), and v2=v′(i,j+q);
• and
• in said means for calculating the motion vector of each pixel in said predicted image, a motion vector of a pixel in said predicted image is calculated using equations:
• u(x,y)=((u0pq+(u1−u0))xq+(u2−u0)yp)m)//(pqk), and
• v(x,y)−((v0pq+(v1−v0))xq+(v2−v0)yp)m)//(pqk)
• where (u00,v00), (u01,v01), and (u02,v02) are n times said motion vectors of said corner points having coordinates (0,0), (r,0), and (0,s), (u(x,y), v(x,y)) is m times the horizontal and vertical components of the motion vector of a pixel having coordinates (x,y) in said predicted image, (u0,v0), (u1,v1), and (u2,v2) are k times said motion vectors of said representative points having coordinates (i,j), (i+p,j), and (i,j+p), u00, v00, u01, v01 u02, v02, u(x,y), v(x,y), u0, v0, u1, v1, u2, and v2 are integers, k, m, and n are integer powers of 2, and “///” and “//” represent integer divisions that round the quotient of ordinary division into an adjacent integer when said quotient of said ordinary division is not an integer, and their priority as an operator is the same as that of ordinary multiplication and division.