Rate-Distortion (RD) Analysis of Subpel Motion Vector Resolution Selection for Video Coding

A rate-distortion (RD) model for subpel motion vector (MV) selection is proposed for power-efficient video coding in this work. To reduce the encoder complexity, the block texture feature is used in the proposed RD model to predict the potential subpel MV gain for a given block. If the gain is not sufficiently large, we may choose integer or half-pel MV to save the search and interpolation cost at the encoder. Quantization noise and external noise are included in the model to improve the prediction accuracy furthermore. The resultant model is shown to be reliable in predicting the RD gain for different subpel resolutions. It is shown by experimental results that the proposed subpel MV selection scheme can maintain the RD performance similar to full subpel MV while reducing encoder complexity significantly.