Method and apparatus for encoding/decoding a motion vector by selecting a set of predicted candidate motion vectors, and method and apparatus for image encoding/decoding using the same

1. A video encoding apparatus using an inter-prediction, comprising:

a video encoder configured to

determine a current motion vector of a current block,

predict the current block by using the determined current motion vector, and

encode a residual block representing a difference between the predicted block and the current block; and

a motion vector encoder configured to

determine a candidate predicted motion vector set based on motion information of neighboring blocks of the current block, wherein the candidate predicted motion vector set has two candidate predicted motion vectors for the current motion vector,

select a predicted motion vector of the current motion vector from among the two candidate predicted motion vectors in the candidate predicted motion vector set, and

encode a differential vector representing a difference between the current motion vector and the selected predicted motion vector and a predicted motion vector index indicating the selected predicted motion vector among the two candidate predicted motion vectors.

2. The apparatus of claim 1 , wherein the neighboring blocks of the current block include blocks located at left, upper, upper right and upper left sides of the current block.

3. The apparatus of claim 1 , wherein the motion vector encoder is configured to

determine whether there is a camera motion based on the number of the neighboring blocks of which motion vectors are zero vectors, and

determine the candidate predicted motion vector set based on whether there is the camera motion.

4. The apparatus of claim 1 , wherein the motion vector encoder is configured to

determine object motions of the neighboring blocks by using the motion information of the neighboring blocks, and

determine the candidate predicted motion vector set based on the determined object motions of the neighboring blocks.

5. The apparatus of claim 1 , wherein the object motions of the neighboring blocks is determined by using predicted motion vectors of the neighboring blocks.

6. The apparatus of claim 1 , wherein the motion vector encoder is configured to

determine object motions of the neighboring blocks by using the motion information of the neighboring blocks and selecting a first predicted candidate motion vector based on determined object motions,

determine whether there is a camera motion by using the motion information of the neighboring blocks and selecting a second predicted candidate motion vector based on a determined camera motion, and

generate the candidate predicted motion vector set including the first predicted candidate motion vector and the second predicted candidate motion vector.

7. The apparatus of claim 1 , wherein the differential vector is encoded by an arithmetic coding.

8. The apparatus of claim 1 , wherein the predicted motion vector index is encoded by an arithmetic coding.

9. A video decoding apparatus using an inter-prediction, comprising:

a motion vector decoder configured to

reconstruct a differential vector and a predicted motion vector index by decoding motion vector data included in a bitstream,

determine a candidate predicted motion vector set by using motion information of neighboring blocks of a current block, wherein the candidate predicted motion vector set has two candidate predicted motion vectors for a current motion vector of the current block,

select a candidate predicted motion vector identified by the reconstructed predicted motion vector index from among the two candidate predicted motion vectors in the candidate predicted motion vector set, as a predicted motion vector of the current motion vector, and

reconstruct the current motion vector of the current block by adding the reconstructed differential vector and the selected predicted motion vector; and

a video decoder configured to

generate a predicted block of the current block by using the reconstructed current motion vector,

reconstruct a residual block from an image data extracted from the bitstream, and

reconstruct the current block by adding the predicted block and the residual block.

10. The apparatus of claim 9 , wherein the neighboring blocks of the current block includes blocks located at left, upper, upper right and upper left sides of the current block.

11. The apparatus of claim 9 , wherein the motion vector decoder is configured to

determine whether there is a camera motion based on the number of the neighboring blocks of which motion vectors are zero vectors, and

determine the candidate predicted motion vector set based on whether there is the camera motion.

12. The apparatus of claim 1 , wherein the motion vector decoder is configured to

determine object motions of the neighboring blocks by using the motion information of the neighboring blocks, and

determine the candidate predicted motion vector set based on the determined object motions of the neighboring blocks.

13. The apparatus of claim 9 , wherein the differential vector is data encoded by an arithmetic coding.

14. The apparatus of claim 9 , wherein the predicted motion vector index is data encoded by an arithmetic coding.