Motion vector encoding/decoding method and device and image encoding/decoding method and device using same

An apparatus for encoding a motion vector for a block, comprising:

• a predicted motion vector candidate selector for selecting a predicted motion vector candidate set including one or more predicted motion vector candidates for the block;
• a motion estimator for determining a search range for the predicted motion vector candidate set, selecting one predicted motion vector candidate among the one or more predicted motion vector candidates as a predicted motion vector for each search point, with respect to each search point within the search range in accordance with a first determination criterion prearranged with a video decoding apparatus, selecting one predicted motion vector among the predicted motion vectors for each search point in accordance with a second determination criterion not prearranged with the video decoding apparatus, and determining a predicted motion vector, a differential motion vector, and a current motion vector;
• and
• a motion information encoder for generating and encoding the differential motion vector as motion information.

A method of decoding a motion vector for a block, comprising:

• decoding encoded motion information and reconstructing a differential motion vector;
• selecting a predicted motion vector candidate set including one or more predicted motion vector candidates for the block;
• selecting one predicted motion vector candidate among the one or more predicted motion vector candidates as a predicted motion vector for a search point according to the reconstructed differential motion vector in accordance with a first determination criterion prearranged with a video encoding apparatus;
• and
• reconstructing a current motion vector by using the selected predicted motion vector and the reconstructed differential motion vector.

An apparatus for decoding a motion vector for a block, comprising:

• a motion information decoder for decoding encoded motion information and reconstructing a differential motion vector;
• a motion vector determiner for selecting a predicted motion vector candidate set including one or more predicted motion vector candidates for the block and selecting one predicted motion vector candidate among the one or more predicted motion vector candidates as a predicted motion vector for a search point according to the reconstructed differential motion vector in accordance with a first determination criterion prearranged with a video encoding apparatus;
• and
• a motion vector reconstructor for reconstructing a current motion vector by using the selected predicted motion vector and the reconstructed differential motion vector.

A method of encoding a video in the unit of blocks, comprising:

• determining a predicted motion vector and a differential motion vector among one or more predicted motion vector candidates in accordance with a first determination criterion prearranged with a video decoding apparatus, and a second determination criterion not prearranged with the video decoding apparatus;
• determining a current motion vector by using a determined predicted motion vector and the differential motion vector;
• encoding the differential motion vector as motion information for a current block;
• motion compensating the current block by using a determined current motion vector and generating a predicted block;
• subtracting the predicted block from the current block and generating a residual block;
• encoding the residual block and generating encoded residual data;
• and
• generating and outputting encoded data including the encoded residual data and the encoded motion information.

An apparatus for encoding a video in the unit of blocks, comprising:

• a motion vector encoder for determining a predicted motion vector and a differential motion vector among one or more predicted motion vector candidates in accordance with a first determination criterion prearranged with a video decoding apparatus, and a second determination criterion not prearranged with the video decoding apparatus, determining a current motion vector by using a determined predicted motion vector and differential motion vector, and encoding the differential motion vector as motion information for a current block;
• a motion compensator for motion compensating the current block by using a determined current motion vector to generate a predicted block;
• a subtracter for subtracting the predicted block from the current block to generate a residual block;
• an encoder for encoding the residual block to generate encoded residual data;
• and
• an encoded data generator for generating and outputting encoded data including the encoded residual data and the encoded motion information.

A method of decoding a video in the unit of blocks, comprising:

• extracting and decoding encoded motion information from encoded data to reconstruct a differential motion vector;
• selecting one predicted motion vector candidate among one or more predicted motion vector candidates as a predicted motion vector for a search point according to a reconstructed differential motion vector in accordance with a first determination criterion prearranged with a video encoding apparatus;
• reconstructing a current motion vector by using the reconstructed differential motion vector and a selected predicted motion vector;
• motion compensating a current block by using a reconstructed current motion vector to generate a predicted block;
• extracting and decoding encoded residual data from the encoded data to reconstruct a residual block;
• and
• adding a reconstructed residual block and the predicted block to reconstruct the current block.

An apparatus for decoding a video in the unit of blocks, comprising:

• an information extractor for extracting encoded motion information and encoded residual data from encoded data;
• a motion vector decoder for decoding the encoded motion information to reconstruct a differential motion vector, selecting one predicted motion vector candidate among one or more predicted motion vector candidates as a predicted motion vector for a search point according to a reconstructed differential motion vector in accordance with a first determination criterion prearranged with a video encoding apparatus, and reconstructing a current motion vector by using the reconstructed differential motion vector and a selected predicted motion vector;
• a motion compensator for motion compensating a current block by using a reconstructed current motion vector to generate a predicted block;
• a decoder for decoding the encoded residual data to reconstruct a residual block;
• and
• an adder for adding a reconstructed residual block and the predicted block to reconstruct the current block.