Hexagon-based Search Research Articles

Application of Genetic Algorithm to Hexagon-Based Motion Estimation

With the improvement of science and technology, the development of the network, and the exploitation of the HDTV, the demands of audio and video become more and more important. Depending on the video coding technology would be the solution for achieving these requirements. Motion estimation, which removes the redundancy in video frames, plays an important role in the video coding. Therefore, many experts devote themselves to the issues. The existing fast algorithms rely on the assumption that the matching error decreases monotonically as the searched point moves closer to the global optimum. However, genetic algorithm is not fundamentally limited to this restriction. The character would help the proposed scheme to search the mean square error closer to the algorithm of full search than those fast algorithms. The aim of this paper is to propose a new technique which focuses on combing the hexagon-based search algorithm, which is faster than diamond search, and genetic algorithm. Experiments are performed to demonstrate the encoding speed and accuracy of hexagon-based search pattern method and proposed method.

Enhanced Hexagonal-Based Search Using Direction-Oriented Inner Search for Motion Estimation

The newly developed enhanced hexagonal-based search using point-oriented inner search (EHS-POIS) enormously speeds up hexagon-based search (HS). From a different perspective, an inherent correlation between distortion and spatial direction through statistical analysis is found. Based on the observed distortion distribution, a novel enhanced hexagonal-based search with direction-oriented inner search (EHS-DIOS) is proposed to avoid real distortion calculation and thus reduce high computation. Experimental results show that, the proposed algorithm is faster than EHS-POIS by achieving two times improvement in terms of inner search speed, and as compared with previous works, it makes a better tradeoff between speed and decoded image quality.

Multi-direction search algorithm for block motion estimation in H.264/AVC

Many efficient search algorithms such as three-step search, new three-step search, four-step search, block-based gradient descent search, diamond search and hexagon-based search are developed for block motion estimation (ME) to search for the optimal objective function. The block ME technique involves an optimisation problem. Although these algorithms can converge to a minimal point rapidly, they suffer from becoming trapped in local minimum if the objective function has multiple minima. To solve this problem, the hybrid multi-hexagon-grid search (UMHexagonS) algorithm has been proposed in H.264/AVC, in which an unsymmetrical-cross search and an uneven UMHexagonS are employed over a wide search range to find a nearly global minimum. The experiment shows that the hybrid UMHexagonS algorithm is computation expensive and is occasionally trapped in local minimum. The authors propose a novel and fast search algorithm, called multi-direction search (MDS) algorithm, which uses an MDS first to find all possible locally optimal points and then uses the extended hexagon search to refine these points for the final optimal motion vector. The experimental results indicate that a significant improvement in computation reduction (∼30 and 50% reduction in average search points, corresponding to 19 and 37% reduction in total encoding time, for MDS and fast MDS, respectively) can be achieved while maintaining better coding performance, compared with the hybrid UMHexagonS algorithm.

Novel fast block motion estimation using diamond‐arc‐hexagon search patterns

This work presents a novel block motion estimation (ME) approach, diamond‐arc‐hexagon search (DAHS), which uses diamond, arc, and hexagon search patterns to accomplish the fast searching process. According to the characteristic of the center‐based motion vector distribution for the real‐world video sequence, DAHS employs a small diamond pattern extended hexagon search to refine the central area search. Furthermore for estimation in large motion situations, the strategy of the large diamond‐to‐arc search can preserve good performance. Experimental results indicate that DAHS is suitable for both (quasi‐) stationary and large motion searches. DAHS outperforms the efficient three‐step (E3SS) and hexagon‐based search (HEXBS) in prediction quality, and improves the searching speed about 9% compared to E3SS. The proposed algorithm was tested using several sequences and delivered excellent performance in search speed and prediction of video quality. The DAHS can be applied to real‐time video processes, such as H.264/MPEG‐4 advanced video coding (AVC) and scalable video coding (SVC).

A Fully Adaptive Distance-Dependent Thresholding Search (FADTS) Algorithm for Performance-Management Motion Estimation

Trading off computational complexity and quality is an important performance constraint for real time application of motion estimation algorithm. Previously, the novel concept of a distance-dependent thresholding search (DTS) was introduced for performance scalable motion estimation in video coding applications. This encompassed the full search as well as other fast searching techniques, such as the three-step search, with different threshold settings providing various quality-of-service levels in terms of processing speed and predicted image quality. The main drawback of the DTS was that the threshold values had to be manually defined. In this paper, the DTS algorithm has been extended to a fast and fully adaptive DTS (FADTS), a key feature of which is the automatic adaptation of the threshold using a desired target and the content from the actual video sequence, to achieve either a guaranteed level of quality or processing complexity. Experimental results confirm the performance of the FADTS algorithm in achieving this objective by demonstrating either comparable or improved search speed over existing fast algorithms including the diamond search, hexagon-based search, and enhanced hexagon-based search, while maintaining similar error performance

Novel Point-Oriented Inner Searches for Fast Block Motion Estimation

Recently, an enhanced hexagon-based (EHS) search algorithm was proposed to speedup the original hexagon-based search (HS) using a 6-side-based fast inner search. However, this 6-side-based method is quite irregular by inspecting the distance between the inner search points and the coarse search points that would lower prediction accuracy. In this paper, a new point-oriented grouping strategy is proposed to develop fast inner search techniques for speeding up the HS and diamond search (DS) algorithms. Experimental results show that the new HS and DS using point-oriented inner searches are faster than their original algorithms up to 30% with negligible peak signal-to-noise ratio degradation

Hexagon-based search pattern for fast block motion estimation

In block motion estimation, a search pattern with a different shape or size has a very important impact on search speed and distortion performance. A square-shaped search pattern is adopted in many popular fast algorithms. Recently, a diamond-shaped search pattern was introduced in fast block motion estimation and has exhibited a faster search speed. Based on an in-depth examination of the influence of the search pattern on speed performance, we propose a novel algorithm using a hexagon-based search pattern to achieve further improvement. The hexagon-based search pattern is investigated in comparison with diamond search pattern and demonstrates significant speedup gain over the diamond-based search. Analysis shows that a speed improvement rate of the hexagon-based search (HEXBS) algorithm over the diamond search (DS) algorithm can be over 80% for locating some motion vectors in certain scenarios. In short, the proposed HEXBS algorithm can find the same motion vector with fewer search points than the DS algorithm. Generally speaking, the larger the motion vector, the more search points the. HEXBS algorithm can save, which is further justified by experimental results.