The current motion vector composition algorithms for reduced spatial resolution video transcoding does not consider the accuracy of input motion vectors. So the errors of these algorithms are rather big. In order to solve this problem

this paper proposes a motion vector composition algorithm based on the accuracy for reduced spatial resolution video transcoding. This algorithm includes two compositions. Firstly

it composes the input motion vectors by averaging them based on SAD. Secondly

it composes the neighboring motion vectors and composed motion vector in the first composition by selecting them based on rate distortion function. The simulation results show that the proposed algorithm reduces the error compared with the algorithms while maintaining the low complexity.