Content-adaptive thresholding early termination scheme on directional gradient descent searches for fast block motion estimation

Abstract

An efficient algorithm named modified directional gradient descent searches to enhance the directional gradient descent search (DGDS) algorithm is presented to reduce computations. A modified search pattern with an adaptive threshold for early termination is applied to DGDS to avoid meaningless calculation after the searching point is good enough. A statistical analysis of best motion vector distribution is analyzed to decide the modified search pattern. Then a statistical model based on the characteristics of the block distortion information of the previous coded frame helps the early termination parameters selection, and a trade-off between the video quality and the computational complexity can be obtained. The simulation results show the proposed algorithm provides significant improvement in reducing the motion estimation (ME) by 17.81% of the average search points and 20% of ME time saving compared to the fast DGDS algorithm implemented in H.264/AVC JM 18.2 reference software according to different types of sequences, while maintaining a similar bit rate without losing picture quality.

Pattern-based integer sample motion search strategies in the context of HEVC

“…by using the distortion from neighboring MVs to derive the threshold). 22,[29][30][31][32][33][34][35][36] Adaptive thresholding for motion vector search in the HEVC context has also been proposed. 37 The authors suggest the computation of 13 thresholds to cover possible combinations of the coding unit depth in the coding tree along with the partition sizes, and employ the coding costs obtained from the first picture in the same group of pictures (GOP).…”

“…Many early termination techniques proposed in the literature suffer from one major drawback, namely the complexity of the model steering the decision process. 31,32,34,36 Clearly, this is not the case for static thresholds, which fail to adopt to a given video sequence. For this reason, only adaptive, yet simple early termination formulations are considered in this context, as described in the following.…”