Quadruple grid true motion estimation for frame rate up-conversion

Abstract

In this paper, a novel frame rate up-conversion (FRUC) algorithm known as Quadruple Grid True Motion Estimation (QGTME) based on true motion estimation on multiple grids is proposed. It carries out bilateral motion estimation (BME) from the view-of-points of 4 different types of overlapping grids to enhance the accuracy of motion vector (MV). Recursive BME on various grids increases the spatial correlation of MV and gradually refines the predicted MV to be as close as the true MV. Early termination measure using motion vector reliability check and temporal MV prediction without using full search is implemented in order to accelerate the BME process. Conventionally, sum of absolute differences is used during BME process as the minimum residue criterion. However, it occasionally results in false MV that is caused by temporal symmetry ambiguity problem. Therefore, a new criterion named as Gaussian sum of absolute differences formulated using Bilinear Gaussian Window is implemented to give different weights to every search points. Last but not least, overlapped block motion compensation (OBMC) technique is incorporated into the motion compensated interpolation process as an effort to reduce the blocking artifacts caused by irregularity of MV fields. The experimental results demonstrate that this proposed QGTME algorithm has outperformed the conventional approaches such as Extended Bilateral Motion Estimation, Multi-Pass Motion Vector Propagation and Bilateral Multi Pass in terms of both objective and subjective evaluation. Furthermore, the computational speed is also boosted greatly.