Method and apparatus for encoding a motion vector, and method and apparatus for encoding/decoding image using same

1. An apparatus of predicting a current motion vector of a current block in a current frame for predictively decoding the current motion vector, the apparatus comprising:

a prediction candidate selector configured to select one or more motion vector prediction candidates from among blocks in the current frame and a block in a reference frame other than the current frame to determine a predicted motion vector corresponding to the current motion vector; and

a predicted motion vector determiner configured to determine the predicted motion vector among the one or more motion vector prediction candidates,

wherein the prediction candidate selector comprises:

means for deriving one or more first motion vector prediction candidates from motion vectors of one or more blocks adjacent to the current block in the current frame, and

means for deriving a second motion vector prediction candidate from a motion vector of the block located in the reference frame, wherein the block, from which the second motion vector prediction candidate is selected, in the reference frame is derived based on a position of the current block in the current frame,

wherein the prediction candidate selector is configured to select one of the first motion vector prediction candidates from upper blocks adjacent to the current block, and one of the first motion vector prediction candidates from left blocks adjacent to the current block,

wherein the prediction candidate selector is configured to determine the predicted motion vector among the one or more motion vector prediction candidates based on a prediction candidate identification flag extracted from a bitstream.

2. The apparatus of claim 1 , wherein the upper blocks include at least one of one or more blocks located at an upper left side, an upper side or an upper right side of the current block.

3. The apparatus of claim 1 , wherein the prediction candidate selector is configured to select the second motion vector prediction candidate from the block in the reference frame which is at a same position with the current block or neighboring to the same position with the current block.

4. The apparatus of claim 1 , wherein the prediction candidate selector is configured to select only one motion vector prediction candidate among two of motion vector prediction candidates which are within a preset distance.

5. The apparatus of claim 1 , wherein the prediction candidate selector is configured to select the one or more motion vector prediction candidates either from among the one or more first motion vector prediction candidates or from among the second motion vector prediction candidate.

6. The apparatus of claim 1 , wherein the prediction candidate selector is configured to select the one or more motion vector prediction candidates based on a prediction candidate selection flag extracted from a bitstream.

7. The apparatus of claim 1 , wherein the predicted motion vector determiner is configured to independently determine each of an x-component and a y-component of the predicted motion vector by

setting an x-component of the predicted motion vector to an x-component of one motion vector prediction candidate among the one or more motion vector prediction candidates and

setting a y-component of the predicted motion vector to a y-component of one motion vector prediction candidate among the one or more motion vector prediction candidates.

8. A method of predicting a current motion vector of a current block in a current frame for predictively decoding the current motion vector, the method comprising:

selecting one or more motion vector prediction candidates from among blocks in the current frame and a block in a reference frame other than the current frame to determine a predicted motion vector corresponding to the current motion vector; and

determining the predicted motion vector among the one or more motion vector prediction candidates,

wherein the selection of the one or more motion vector prediction candidates comprises:

deriving one or more first motion vector prediction candidates from motion vectors of one or more blocks adjacent to the current block in the current frame, and

deriving a second motion vector prediction candidate from a motion vector of the block located in the reference frame,

wherein the block, from which the second motion vector prediction candidate is selected, in the reference frame is derived based on a position of the current block in the current frame,

wherein the deriving of the one or more of first motion vector prediction candidates comprises:

selecting one of the first motion vector prediction candidates from left blocks adjacent to the current block, and

selecting one of the first motion vector prediction candidates from upper blocks adjacent to the current block,

wherein the predicted motion vector is determined among the one or more motion vector prediction candidates based on a prediction candidate identification flag extracted from a bitstream.

9. The method of claim 8 , wherein the upper blocks include at least one of one or more blocks located at an upper left side, an upper side or an upper right side of the current block.

10. The method of claim 8 , wherein the second motion vector prediction candidate is selected from the block in the reference frame which is at a same position with the current block or neighboring to the same position with the current block.

11. The method of claim 8 , wherein the selection of one or more motion vector prediction candidates comprising:

selecting only one motion vector prediction candidate among two of motion vector prediction candidates which are within a preset distance.

12. The method of claim 8 , wherein the one or more motion vector prediction candidates are selected either from among the one or more first motion vector prediction candidates or from among the second motion vector prediction candidate.

13. The method of claim 8 , wherein the one or more motion vector prediction candidates are selected based on a prediction candidate selection flag extracted from a bitstream.

14. The method of claim 8 , wherein the predicted motion vector is determined independently for each of an x-component and a y-component of the predicted motion vector by

setting an x-component of the predicted motion vector to an x-component of one motion vector prediction candidate among the one or more motion vector prediction candidates and

setting a y-component of the predicted motion vector to a y-component of one motion vector prediction candidate among the one or more motion vector prediction candidates.