Adaptive Motion Search Range Prediction for Video Encoding

An adaptive motion search range (SR) prediction algorithm for video coding is proposed in this letter. To determine a proper SR size for motion vectors (MVs) is important to video encoding, since a good choice helps reduce the memory access bandwidth while maintaining the rate-distortion coding performance. To achieve this objective, we first obtain a motion vector predictor (MVP) for a target block based on MVs of its spatially and temporally neighboring blocks, which form a MV prediction set. Then, we relate the variance of the MV prediction set to the SR. That is, a larger variance implies lower accuracy of the MVP and, thus, a larger SR. Finally, we derive a probability model for the motion vector prediction difference, the difference between the optimal MV and the MVP, to quantify the probability for a chosen SR to contain the optimal MV. The superior performance of the proposed SR selection algorithm is demonstrated by experimental results.