Video decoding apparatus, video decoding method, and integrated circuit

A video decoding apparatus which decodes an encoded video stream encoded using motion estimation performed on a block-by-block basis, the video decoding apparatus comprising:

• a decoding unit configured to decode a difference value of a motion vector from the encoded video stream;
• a vector predictor calculating unit configured to calculate a vector predictor indicating a prediction value of the motion vector;
• a motion vector generating unit configured to generate a motion vector by adding the vector predictor calculated by the vector predictor calculating unit to the difference value of the motion vector decoded by the decoding unit;
• a motion vector comparing unit configured to compare the motion vector generated by the motion vector generating unit with motion vectors of adjacent blocks to determine whether or not the motion vector is equal to the motion vectors of the adjacent blocks;
• a block combining unit configured to combine the blocks determined by the motion vector comparing unit as being equal in motion vector, into one motion compensation block on which motion compensation is to be performed;
• a reference image obtaining unit configured to obtain, based on the motion vector generated by the motion vector generating unit, a reference image corresponding to the motion compensation block from reference image data previously decoded and stored into a memory;
• a motion compensating unit configured to perform motion compensation using the reference image obtained by the reference image obtaining unit, to generate a prediction image corresponding to the motion compensation block;
• and
• a reconstructing unit configured to reconstruct an image using the prediction image generated by the motion compensating unit.

A video decoding method of decoding an encoded video stream encoded using motion estimation performed on a block-by-block basis, the video decoding method comprising:

• decoding the encoded video stream to derive a flag regarding a motion vector, the flag indicating one of (i) a prediction direction indicating that the motion vector is equal to a motion vector of an adjacent block, (ii) that the motion vector is 0, and (iii) that difference information on the motion vector is encoded in the encoded video stream;
• determining whether or not a plurality of the motion vectors of adjacent blocks are equal to each other, using a plurality of the flags regarding the motion vectors of the adjacent blocks, the flags being derived in the decoding;
• combining the adjacent blocks determined in the comparing as being equal in motion vector, into one motion compensation block on which motion compensation is to be performed;
• generating a motion vector based on the flag regarding the motion vector;
• obtaining, based on the motion vector generated in the generating, a reference image corresponding to the motion compensation block from reference image data previously decoded and stored into a memory;
• performing motion compensation using the reference image obtained in the obtaining, to generate a prediction image corresponding to the motion compensation block;
• and
• reconstructing an image using the prediction image generated in the performing.

An integrated circuit which decodes an encoded video stream encoded using motion estimation performed on a block-by-block basis, the integrated circuit comprising:

• a decoding unit configured to decode the encoded video stream to derive a flag regarding a motion vector, the flag indicating one of (i) a prediction direction indicating that the motion vector is equal to a motion vector of an adjacent block, (ii) that the motion vector is 0, and (iii) that difference information on the motion vector is encoded in the encoded video stream;
• a motion vector comparing unit configured to determine whether or not a plurality of the motion vectors of adjacent blocks are equal to each other, using a plurality of the flags regarding the motion vectors of the adjacent blocks, the flags being derived by the decoding unit;
• a block combining unit configured to combine the adjacent blocks determined by the motion vector comparing unit as being equal in motion vector, into one motion compensation block on which motion compensation is to be performed;
• a motion vector generating unit configured to generate a motion vector based on the flag regarding the motion vector;
• a reference image obtaining unit configured to obtain, based on the motion vector generated by the motion vector generating unit, a reference image corresponding to the motion compensation block from reference image data previously decoded and stored into a memory;
• a motion compensating unit configured to perform motion compensation using the reference image obtained by the reference image obtaining unit, to generate a prediction image corresponding to the motion compensation block;
• and
• a reconstructing unit configured to reconstruct an image using the prediction image generated by the motion compensating unit.