Abstract: A motion vector coder performs coding on motion vectors MV0, MV1 and MV2 in the stated order. Initially, the motion vector coder receives the motion vectors MV0-MV2 from a motion vector holder. The motion vector coder codes the motion vector MV0 at the lowest layer 0. Subsequently, the motion vector coder codes (½*MV0-MV1), which is a difference between ½ of MV0 and MV1, instead of coding the motion vector MV1 at layer 1. The motion vector coder then codes (½*MV1-MV2), which is a difference between ½ of MV1 and MV2, instead of coding the motion vector MV2 at layer 2.

Abstract: A motion vector holding unit 61 holds motion vector information with respect to a backward reference frame detected beforehand and received from a motion compensation unit 60. A motion vector calculation unit 63 calculates multiple motion vectors for each macro block defined in a coding target frame with reference to the motion vector information with respect to the backward reference frame held by the motion vector holding unit 61 according to each calculation mode of a set of different calculation modes. A motion compensation prediction unit 64 performs motion compensation using motion vectors obtained for each calculation mode, thereby creating predicted images. The predicted images are output to a coding amount estimation unit 65. The coding amount estimation unit 65 estimates the coding amount of the subtraction image, which is the subtraction between the predicted image and the original image, for each calculation mode.

Abstract: A local motion vector detection unit 66 obtains a local motion vector LMV for each macro block in a coding target frame image. A region setting unit 64 sets multiple global regions in the frame image. A global motion vector calculation unit 68 calculates a global motion vector GMV which indicates the global motion within each global region. A local motion vector difference coding unit 72 performs coding of the difference ?LMV which has been obtained by making the difference between each of the local motion vectors LMV within the global region and the global motion vector GMV obtained for each global region. A global motion vector difference coding unit 74 performs coding of the difference ?GMV which has been obtained by making the difference between each of the global motion vectors GMV obtained for corresponding global region and the reference global motion vector GMVB serving as a reference.

Abstract: A region setting unit 64 sets multiple global regions in a frame image. A bit number adjustment unit 62 adjusts the number of bits of the local motion vectors LMV which are to be obtained for each global region. A local motion vector detection unit 66 detects the local motion vectors LMV with the number of bits adjusted by the bit number adjustment unit 62 in units of macro blocks for each global region. A global motion vector calculation unit 68 calculates the global motion vector GMV which represents the global motion for each global region. A local motion vector difference coding unit 72 calculates the difference ?LMV, which is the difference between each local motion vector LMV and the global motion vector GMV, for each global region, and performs coding thereof.