Patent ID: 8379724

Claim:
An image coding apparatus for coding an image, comprising: a frame memory for storing a reference image including first and second coded reference image blocks; a first prediction motion search unit, coupled to an output of the frame memory, which computes, for a plurality of different coded reference image block sizes, coding cost information for coding on basis of the first and second coded reference image blocks, and outputs first and third coding cost information including information on a block size of the plurality of different coded reference image block sizes with minimum coding cost; and a second prediction motion search unit, coupled to the output of the frame memory and an output of the first prediction motion search unit, which outputs second coding cost information for coding on the basis of the first and second coded reference image blocks by using the first and third coding cost information, including information on the block size, output from the first prediction motion search unit; and one or more image coding units, which perform coding of the image by using the first coding cost information, the second coding cost information, and the third coding cost information, wherein the first prediction motion search unit comprises: a first unidirectional prediction motion search unit configured to perform motion searches for a first unidirectional prediction motion in the plurality of different image block sizes having units of n (n is 1 or larger) using the first coded reference image block, and to output the first coding cost information including a first minimum coding cost, a first motion vector, and a first block size of the plurality of different image block sizes with minimum coding cost for coding the image on the basis of the first coded reference image block; and a second unidirectional prediction motion search unit configured to perform motion searches for a second unidirectional prediction motion in the plurality of different image block sizes having units of n (n is 1 or larger) using the second coded reference image block that is different from the first coded reference image block, and to output the third coding cost information including a second minimum coding cost, a second motion vector, and a second block size of the plurality of different image block sizes with minimum coding cost for coding the image on the basis of the second coded reference image block, and wherein the second prediction motion search unit selects one of the first and second block sizes for coding on the basis of the first and second coded reference image blocks by comparing the first coding cost information and the third coding cost information.