Motion vector refinement search with integer pixel resolution

A method for determining a motion vector for a block, wherein the method is applied to a processor of an apparatus and comprises:

• obtaining at least two candidate motion vectors pointing to positions in a reference picture and forming a search space;
• individually modifying each of the at least two candidate motion vectors by predetermined shift operations to the positions in the reference picture so as to obtain a respective representative motion vector in a modified search space formed by at least two representative motion vectors, wherein a candidate motion vector of the at least two candidate motion vectors points to a corresponding fractional sample position in the search space, wherein the shift operation applied to the candidate motion vector results in a position pointed to by the respective representative motion vector being given by rounding the fractional sample position pointed to by the candidate motion vector to an integer sample position, and wherein the integer sample position resulting from rounding the fractional sample position is one of the sample positions of the modified search space,
• selecting a first motion vector from the modified search space, by evaluating a predetermined criterion in the modified search space, and
• obtaining a second motion vector by applying an inverse shift operation of the predetermined shift operation by which the first motion vector was obtained to the first motion vector.

A non-transitory computer readable medium comprising processor-executable instructions which when executed by a processor cause the processor to perform a method for determining a motion vector for a block, the method including:

• obtaining at least two candidate motion vectors pointing to positions in a reference picture and forming a search space;
• individually modifying each of the at least two candidate motion vectors by predetermined shift operations to the positions in the reference picture so as to obtain a respective representative motion vector in a modified search space formed by at least two representative motion vectors, wherein a candidate motion vector of the at least two candidate motion vectors points to a corresponding fractional sample position in the search space, wherein the shift operation applied to the candidate motion vector results in a position pointed to by the respective representative motion vector being given by rounding the fractional sample position pointed to by the candidate motion vector to an integer sample position, and wherein the integer sample position resulting from rounding the fractional sample position is one of the sample positions of the modified search space,
• selecting a first motion vector from the modified search space, by evaluating a predetermined criterion in the modified search space, and
• obtaining a second motion vector by applying an inverse shift operation of the predetermined shift operation by which the first motion vector was obtained to the first motion vector.