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
A method of encoding a motion vector includes: selecting one of a plurality of predicted candidate motion vector sets by using motion information of neighboring blocks of a current block; selecting one of predicted candidate motion vectors within a selected predicted candidate motion vector set, as a predicted motion vector; encoding a differential motion vector representing a difference between a current motion vector or motion vector of the current block and a selected predicted motion vector; and encoding a predicted motion vector index indicating the selected predicted motion vector. As a motion vector is encoded after selecting an efficient predicted candidate motion vector set, the size of a differential vector to be encoded can be reduced without necessarily encoding additional information to indicate which set of predicted candidate motion vectors has been selected, resulting in improved compression efficiency of motion vectors and in turn the improved video compression efficiency.
1. A video encoding method using an inter-prediction, comprising:
determining a current motion vector of a current block;
predicting the current block by using the determined current motion vector;
determining 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;
selecting a predicted motion vector of the current motion vector from the two candidate predicted motion vectors in the predicted candidate motion vector set;
encoding a differential motion 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; and
encoding a residual block representing a difference between the predicted block and the current block.
2. The method 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 method of claim 1 , wherein the determination of the candidate predicted motion vector set comprises:
determining whether there is a camera motion based on the number of the neighboring blocks of which motion vectors are zero vectors; and
determining the predicted candidate motion vector set based on whether there is the camera motion.
4. The method of claim 1 , wherein the determination of the candidate predicted motion vector set comprises:
determining object motions of the neighboring blocks by using the motion information of the neighboring blocks; and
determining the candidate predicted motion vector set based on determined object motions of the neighboring blocks.
5. The method of claim 1 , wherein the object motions of the neighboring blocks is determined by using predicted motion vectors of the neighboring blocks.
6. The method of claim 1 , wherein the determination of the candidate predicted motion vector set comprises:
determining 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;
determining 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
generating the candidate predicted motion vector set including the first predicted candidate motion vector and the second predicted candidate motion vector.
7. A video decoding method using an inter-prediction, comprising:
reconstructing a differential motion vector and a predicted motion vector index by decoding a motion vector data extracted from a bitstream;
determining a predicted candidate 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;
selecting 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;
reconstructing the current motion vector of the current block by adding the reconstructed differential motion vector and the selected predicted motion vector;
generating a predicted block of the current block by using the reconstructed current motion vector, and reconstructing a residual block from an image data extracted from the bitstream; and
reconstructing the current block by adding the predicted block and the residual block.
8. The method of claim 7 , wherein the neighboring blocks of the current block includes blocks located at left, upper, upper right and upper left sides of the current block.
9. The method of claim 7 , wherein the differential vector is data encoded by an Arithmetic Coding.
10. The method of claim 7 , wherein the predicted motion vector index is data encoded by an Arithmetic Coding.