Apparatus and method for generating/recovering motion information based on predictive motion vector index encoding, and apparatus and method for image encoding/decoding using same

A motion information generating apparatus, comprising:

• a predictive motion vector index generator configured to generate, in performing an inter prediction of a current block by using a reference frame, index information of a predictive motion vector of the current block based on motion information of a co-located block of the reference frame;
• a subtractor configured to generate a differential motion vector by subtracting the predictive motion vector from a motion vector of the current block;
• and
• a motion information constructor configured to construct motion information of the current block including at least one selected from the group consisting of a reference frame index, a predictive motion vector index and the differential motion vector.

A video decoding apparatus, comprising:

• a decoder configured to decode a bitstream received from a video encoding apparatus tot
• extract a quantization frequency coefficient row from the bitstream to generate a residual block having the extracted quantization frequency coefficients,
• extract motion information including predictive motion vector index and reference frame index, and
• extract a differential motion vector from the bitstream;
• an inverse-quantization and inverse-transform unit configured to inversely quantize a quantized transformed residual block into a transformed residual block and inversely transforms the transformed residual block to generate a residual block;
• an inter prediction unit configured to set a predictive motion vector based on the predictive motion vector index, reconstruct a motion vector of a current block to be decoded by adding the predictive motion vector and the differential motion vector, and reconstruct a prediction block of the current block based on the reconstructed motion vector of the current block and the reference frame index;
• and
• an adder configured to reconstruct the current block by adding the reconstructed prediction block and the residual block generated by the inverse-quantization and inverse-transform unit.

A motion information reconstruction apparatus, comprising:

• a predictive motion vector setting unit configured to configure a predictive motion vector by extracting an index value of the predictive motion vector from a bitstream;
• an adder configured to configure a motion vector of a current block by adding the predictive motion vector and a differential motion vector extracted from the bitstream;
• and
• a motion information constructor configured to reconstruct motion information based on reference frame index included in the bitstream and the motion vector of the current block.

A video encoding method performed by a video encoding apparatus, comprising:

• for an inter prediction of a current block by using a reference frame, (i) generating a predictive motion vector index of the current block based on motion vectors of blocks adjacent to the current block and a motion vector of a co-located block of a reference frame, (ii) generating motion information of the current block including the predictive motion vector index and reference frame index together with a differential motion vector obtained by subtracting the predictive motion vector from a motion vector of the current block, and (iii) generating a prediction block based on the generated motion information;
• subtracting the generated prediction block from the current block to thereby generate a residual block;
• transforming and quantizing the residual block with frequency coefficients;
• and
• encoding the transformed and quantized residual block to thereby generate a bitstream.

A video decoding method performed by a video decoding apparatus, comprising:

• decoding a bitstream received from an video encoding apparatus to extract a quantization frequency coefficient row, and generating a residual block having quantization frequency coefficients based on the extracted quantization frequency coefficient row;
• extracting motion information including predictive motion vector index and reference frame index;
• extracting a differential motion vector from the bitstream;
• inversely quantizing a quantized transformed residual block into a transformed residual block and inversely transforming the transformed residual block to generate a residual block;
• setting a predictive motion vector based on the predictive motion vector index, reconstructing a motion vector of a current block to be decoded by adding the predictive motion vector and the differential motion vector, and reconstructing a prediction block of the current block based on the reconstructed motion vector of the current block and the reference frame index;
• and
• reconstructing the current block by adding the reconstructed prediction block and the residual block.