Adaptive interpolated motion compensated prediction
Current video coders rely heavily on block-based motion compensation, which is known to accurately capture pure translation, but to (at best) approximate all other types of motion, such as rotation and zoom. Moreover, as motion vectors are obtained through pixel-domain block matching to optimize a rate-distortion cost, and do not necessarily represent the actual motion, the model should not be considered a proper sampling of the underlying pixel motion field. This paper explicitly treats several neighboring motion vectors as pointers to multiple observation sources for estimating a pixel in the current frame. The corresponding optimal linear estimation coefficients are derived for predicting each pixel, given the observations obtained based on nearby motion vectors. Prediction coefficients are further adapted to local statistics by switching between predefined sets of coefficients, which are trained offline through a procedure of “K-modes” clustering. Experimental results outside the training set validate this paradigm with significant bit rate savings over conventional motion compensated prediction.