Hexagonal Search Research Articles

Adaptive Prediction based Diamond Search Algorithm (APDS) for Video Encoder of Solar Powered UAV

Aerial Vehicle (UAV) provide bird's eye view over an intersection or a large area, and provide real-time surveillance of area under observation. UAVs have been playing a vital role in disaster management due to the increased sensing and processing capabilities. This paper proposes a fast adaptive prediction based diamond search Motion Estimation (ME) algorithm for Sun Falcon 2, a solar powered UAV's video encoder to cope the computational complexity, low power and increased quality of ME process requirement. Results show that the proposed Adaptive Predict Diamond Search (APDS) ME algorithm performs best in the term of PSNR, MSE and number of Search Points (SP), for approximately all the video sequences. Moreover, performance of APDS is decreased a little bit in term of number of SP when compared to Hexagon search algorithm but its PSNR is still considerably high for those video sequences. The average PSNR improvement rate of APDS is 0.62, 2.67, 0.82, 0.83 and 2.31 for Diamond Search (DS), HexBS, FHS, FSS and MDS respectively, while the average SIR is 25.4404, 6.3374, 48.274 and 205.55 for DS, FHS, FSS and MDS respectively.

Performance Analysis of Fast Block Matching Motion Estimation Algorithms

Motion Estimation (ME) is an integral part of any video encoder and a large number of Block Matching Motion Estimation (BMME) Algorithms are proposed to cope the computational complexity and increase quality of ME process requirement. Therefore, it is necessary to evaluate the performance of these ME algorithms for different motion activities. In this paper five fast famous BMME algorithms are considered to evaluate their performance on the basis of ME time, search points, PSNR and Means Square Error (MSE). The algorithms evaluated in this paper are considered for state of the art video compression standards like MPEG 1, to MPEG4 and H.261 to H.264. Results show that the PSNR of Diamond Search (DS) is best for all test video sequences, whereas, Hardware Modified DS takes maximum number of search points to calculate motion vector. Moreover, hexagon search algorithm takes minimum number of search points but its PSNR is considerably lower than the other algorithms.

Multi Point Search Pattern for Fast Search Motion Estimation of High Resolution Video Coding

Block matching algorithm (BMA) based motion estimation (ME) is most accepted method for removal of temporal redundancy between frames in video coding. With recent advancement in resolution of video, the need of search pattern covering most of macroblocks within search area in frame is increasing. Existing search patterns are tiny and take plenty of time to reach at edge or corner of the search window. With aim of covering nearly every probable candidate macroblocks in all direction and to speed up the search process, multipoint search patterns are presented in this paper. Initial candidate macroblocks are chosen on grid of 12x12 and then search progresses like traditional diamond or hexagon search. Due to multipoint, chances of trapping in incorrect direction is very less and method can exhibit better quality of encoding with optimum number of search points. Index Terms—Motion Estimation, Fast search block matching algorithm, Multi point search, H.265, HD video sequences.

Fractal Depth Map Sequence Coding Algorithm with Motion-vector-field-based Motion Estimation

Three-dimensional video coding is one of the main challenges restricting the widespread applications of 3D video and free viewpoint video. In this paper, a novel fractal coding algorithm with motion-vector-field-based motion estimation for depth map sequence is proposed. We firstly add pre-search restriction to rule the improper domain blocks out of the matching search process so that the number of blocks involved in the search process can be restricted to a smaller size. Some improvements for motion estimation including initial search point prediction, threshold transition condition and early termination condition are made based on the feature of fractal coding. The motion-vector-field-based adaptive hexagon search algorithm on the basis of center-biased distribution characteristics of depth motion vector is proposed to accelerate the search. Experimental results show that the proposed algorithm can reach optimum levels of quality and save the coding time. The PSNR of synthesized view is increased by 0.56 dB with 36.97% bit rate decrease on average compared with H.264 Full Search. And the depth encoding time is saved by up to 66.47%. Moreover, the proposed fractal depth map sequence codec outperforms the recent alternative codecs by improving the H.264/AVC, especially in much bitrate saving and encoding time reduction.

Novel superimposed diamond search algorithm for medical image compression

A novel search algorithm called superimposed diamond search algorithm SDSA based on lifting wavelet transform LWT for medical image compression is proposed in this paper. Fuzzy C means clustering FCM is applied to extract the region of interest ROI from the medical image. MAXSHIFT method is used to scale the coefficients so that the bits associated with the ROI are placed in higher bit planes than the bits associated with the background without the requirement of the shape information and without the need for calculating the ROI mask. SDSA keeps track of significant pixels of wavelet sub-band in hexagonal search in the scan order of left to right and top to bottom. The experimental results show the good compression ratio over the other existing methods such as set partitioning in hierarchical trees SPIHT and embedded zerotree wavelet EZW.

SSR Surveillance Network Double Covering Problem with Obstacle Effect Consideration

In this paper, SSR surveillance network double covering problem with obstructing affected by surface features is studied. The purpose is to improve the performance of SSR surveillance network, thus ensure the efficiency and safety management in airspace. The objective is to minimize the number of radar and the decision variable is the site of radar. Only one type of radar is considered. Firstly, radar network covering problem without obstructing affect is studied. The objective is to minimize the number of radar by arrange them in suitable position satisfying the requirement of complete coverage. For this problem, regular hexagonal expansion algorithm and tabu search algorithm is proposed. Worst-case analysis is provided. We conclude the performance of the algorithm is better when the ratio between the whole region area and radar coverage area is bigger. Secondly, double covering problem in the whole region is taken into account. For this problem, regular triangular expansion algorithm and tabu search algorithm is provided firstly which is more efficient for double covering problem. For those convex target areas worst-case analysis is provided also. Finally, SSR surveillance network covering problem with obstructing affected by surface features is studied. The constraint of complete coverage in whole region is also considered in this problem. This problem is more complex and no efficient optimal algorithm can be used. For this problem, improved hexagon expansion algorithm and tabu search algorithm is applied..

An Electronic Image Stabilization Algorithm Based on Efficient Block Matching on the Bitplane

This paper proposes an electronic image stabilization algorithm based on efficient block matching on the plane. This algorithm uses a hexagonal search algorithm, and uses the bit-planes to estimate and compensate for the translational motion between video sequences at the same time; As for the rotary motion vector generated in the video sequences, in order to highlight the intensity change of the image sequence, the algorithm firstly conducts Laplace transform for the reference frame, then select a number of characteristics at the image edge to make block matching with the current frame, calculate and compensate for the rotational movement that may exist finally. Through theoretical analysis and simula-tion, we prove that, as for a mixed translational and rotational motion video sequences, the proposed algorithm can reduce required time for block matching computation ,while improving the accuracy of the electronic image stabilization.

A fast block motion estimation algorithm using dynamic pattern search

In block-based motion estimation algorithms, it has always been desired to reduce search point computation with quality as good as full-search algorithm. A number of such algorithms like diamond search (DS) and hexagon search (HS) have been proposed in literature, which use fixed-size search patterns for finding motion vectors. The drawback with these fixed-size search pattern–based algorithms is that they may suffer from oversearch/undersearch problem depending on the magnitude of the motion vector. In this manuscript, a dynamic pattern search–based algorithm (DPS), which uses spatial and temporal coherence among blocks and dynamically adapts its search pattern for a candidate block, has been proposed. The proposed algorithm has been compared with various motion estimation algorithms like DS, HS, adaptive rood pattern search (ARPS) and full search in terms of various performance parameters. Experimental results show that proposed DPS has a speed gain of 1.18 over ARPS, whereas it is nearly 1.94 and 1.33 over DS and HS algorithms in terms of average search points/block. Further, in terms of peak signal-to-noise ratio (PSNR) (dB)/frame, DPS produces almost same average value than ARPS and HS, whereas it is only 1% inferior to DS. A modified version of DPS has also been proposed, which increases its speed gain by 1.39 times with negligible decrease in PSNR. In terms of another time parameter—average execution time per frame (s)—for DPS, it is 0.66 s, whereas this time is 0.71, 0.77 and 1.06 for ARPS, HS and DS algorithms, respectively.

High Efficiency Architecture Design of Real-Time QFHD for H.264/AVC Fast Block Motion Estimation

Motion estimation (ME) in the MPEG-4 AVC/JVT/H.264 video coding standard employs seven permitted block sizes to improve the rate-distortion performance. This novel feature achieves significant coding gain over coding a macroblock using the fixed block size. However, ME is computationally intensive with the complexity increasing linearly with the number of the allowed block sizes. This paper presents an architecture for a combined fast ME algorithm with the predict hexagon search (PHS) and the edge information mode decision (EIMD). The EIMD algorithm utilizes edge information to predict the best block size quickly and precisely. The PHS algorithm searches the best motion vector efficiently. The analytical results reveal that the EIMD+PHS algorithm is 2.4-25 times faster than other popular fast ME algorithms. Additionally, the EIMD+PHS algorithm is 600-2000 times faster than JM10.2, and the peak signal-to-noise ratio degradation is less than 0.15 dB. The proposed architecture applies a large search range and low operation frequency as compared with other popular ME architectures. The proposed architecture only needs 19.4 MHz operating frequency to achieve real-time execution for the general specification of the standard-definition television (720 × 480) used with four reference frames and the search range of 256 × 256. The proposed architecture only requires 116.6 MHz operating frequency to achieve real-time execution for the ultrahigh specification of the quad full high definition (3840 × 2160) used with one reference frame and the search range of 256 × 256. The gate count of the proposed architecture is 300 K, and the memory usage is 12.6 kB.

A Fast Fractal Video Coding Algorithm Using Cross-Hexagon Search for Block Motion Estimation

We propose a novel fractal video coding method using fast block-matching motion estimation to overcome the drawback of the time-consuming character in the fractal coding. As fractal encoding essentially spends most time on the search for the best-matching block in a large domain pool, search patterns and the center-biased characteristics of motion vector distribution have large impact on both search speed and quality of block motion estimation. In this paper, firstly, we propose a new hexagon search algorithm (NHEXS), and, secondly, we ameliorate, by using this NHEXS, the traditional CPM/NCIM, which is based on Fisher's quadtree partition. This NHEXS uses two cross-shaped search patterns as the first two initial steps and large/small hexagon-shaped patterns as the subsequent steps for fast block motion estimation (BME). NHEXS employs halfway stop technique to achieve significant speedup on sequences with stationary and quasistationary blocks. To further reduce the computational complexity, NHEXS employs modified partial distortion criterion (MPDC). Experimental results indicate that the proposed algorithm spends less encoding time and achieves higher compression ratio and compression quality compared with the traditional CPM/NCIM method.

FAST BLOCK MOTION ESTIMATION WITH EDGE ALIGNMENT ON H.264 VIDEO CODING

This paper presents a novel block matching scheme with edge alignment strategy on H.264 video coding. which uses multiple references and multiple block Sizes for motion estimation in order to improve the rate-distortion performance. In H.264. the computational complexity is linearly dependent on the number of allowed reference frames and block sizes using the full exhaustive search. Many fast block-matching algorithms reduce the computational complexity of motion estimation by carefully designing the search patterns with different shapes or sites which have significant impact on the search speed and distortion performance. However, the search speed and the distortion performance conflict often with each other for these methods. In this paper. given a block in the current frame. we first apply a fast approximate method based on edge alignment to obtain a good initial motion vector as well as a tight initial hound of distortion measure. Then, considering the edge orientation of the block, a modified hexagon search is used to fine tune the motion vector in low computation complexity. The proposed algorithm also pays attentions to the characteristics of multiple reference frames and multiple block sizes in H.264. Computer simulation results show that the proposed method gives good performance and pans a new way to design a cost-effective real-time video coding system.

An adaptive fast search algorithm for block motion estimation in H.264

Motion estimation is an important issue in H.264 video coding systems because it occupies a large amount of encoding time. In this paper, a novel search algorithm which utilizes an adaptive hexagon and small diamond search (AHSDS) is proposed to enhance search speed. The search pattern is chosen according to the motion strength of the current block. When the block is in active motion, the hexagon search provides an efficient search means; when the block is inactive, the small diamond search is adopted. Simulation results showed that our approach can speed up the search process with little effect on distortion performance compared with other adaptive approaches.

Hardware Design of Hexagonal Search Algorithm

Motion Estimation (ME) is vital element in video coding as it reduces temporal redundancy. Given that the motion estimation stage is very complex in terms of computational effort, a hardware implementation on a reconfigurable circuit is crucial for the requirements of different real time multimedia applications. Hexagonal search algorithm is one of Fast Block Matching Algorithms (FBMAs) which belongs to block based motion estimation. This paper presents a hardware design of hexagonal search algorithm and its implementation on FPGA. We specified, simulated and synthesized the design with VHDL description. The proposed design is implemented on a virtex5 FPGA using xc5vlx30-3ff676 component. Our simulations confirm the functionality of the algorithm using Modelsim (version XE 6.3.4) simulator. When our design was synthesized on xc5vlx30-3ff676, we obtained the following results for area and clock frequency: 6810 LUT and 65,892MHz respectively.

A Multiple Pattern Algorithm for Block Motion Estimation Based on Variable Block-size

Motion estimation is computationally intensive in the H.264 video-coding standard.A novel variable block- size block-matching motion estimation algorithm using multiple hexagon search patterns is presented.According to the seven kinds of macroblock partitions,multiple hexagon search patterns,such as large hexagon patterns,horizontal flatted hexagon pattern,and vertical flatted hexagon pattern,are adopted respectively.Compared with traditional hexagon search algorithm,the new strategy provides not only better matching flexibility but also more sufficient overlapping of target searching block.Simulation result shows that the proposed algorithm has a prediction quality close to the full search (FS) and reduces the search points by about 10 % relatively to the hexagon search algorithm.

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.

Predictive cross-hexagon search algorithm for fast block motion estimation

Block-matching motion estimation plays an important role in real-time video compression and thus has significant impact on searching speed and quality of performance. In order to address these issues, we introduce a highly efficient block motion estimation algorithm, referred to as a predictive cross-hexagon search (PCHS) algorithm, that can considerably reduce the complexity of the Joint Video Team (JVT) encoder. In contrast to many classical fast motion estimation algorithms, PCHS has three desirable features: (1) prediction of a search center, (2) usage of search patterns with different sizes, and (3) early algorithm termination that makes it adaptive and effective. We set four predictor candidates for initial search point options and then increase the accuracy of the predictor. The different-size search patterns, including small cross search patterns, hexagon search patterns, and cross-hexagon search patterns, used in the searching process can better suit more motion types. Due to the high accuracy of the predictor, the proposed algorithm adapts early termination; as the predictor is good enough, the search stops early. Therefore, the PCHS algorithm is suitable for real-time video encoding, as it can speed up the encoder without sacrificing performance compared with other fast algorithms.

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).

Panorama Mosaic Optimization for Mobile Camera Systems

In order to enable the real-time image mosaic in mobile devices that have very limited computing power and memory, we propose an efficient image mosaic algorithm with integer arithmetic. The proposed algorithm is focused not only on the computational efficiency, but also on the performance improvement of image mosaic. For the efficient projection without transform estimation, we obtain successive images through the semitransparent view finder which shows the fixed amount of right part of previously captured image. We project each images onto cylindrical surface by the proposed projection equation and integer arithmetic. We align the projected images by hierarchical hexagon search and a matching measure that is robust to illumination changes caused by different exposures and vignette distortion. Finally, the images are naturally blended using color compensation and dynamic programming based stitching. The proposed mosaic algorithm is embedded and tested in mobile phone systems. According to various tests and experiments, the proposed algorithm shows good panorama composition in real-time compared with the other PC-based methods.

A novel adjustable multiple cross-hexagonal search algorithm for fast block motion estimation

In this paper, we propose a novel adjustable multiple cross-hexagonal search (AMCHS) algorithm for fast block motion estimation. It employs adjustable multiple cross search patterns (AMCSP) in the first step and then uses half-way-skip and half-way-stop technique to determine whether to employ two hexagonal search patterns (HSPs) subsequently. The AMCSP can be used to find small motion vectors efficiently while the HSPs can be used to find large ones accurately to ensure prediction quality. Simulation results showed that our proposed AMCHS achieves faster search speed, and provides better distortion performance than other popular fast search algorithms, such as CDS and CDHS.

Adaptive Double-Layered Initial Search Pattern for Fast Motion Estimation

Multimedia communication relies on data compression technology to reduce the data bits of transmission. Motion compensation is the key function in exploiting temporal redundancy for compression in most video coding standards. For example, fixed search pattern motion estimation algorithms such as hexagonal search (HEXBS) usually spend extra search steps to confirm near-zero motion vectors. Divide and conquer methods such as the efficient three-step search (E3SS) are not optimized for the probability model of motion vectors. This paper proposes a pair of complementary double-layered (inner layer and outer layer) initial search patterns to reduce computational complexity. The inner-layer search is applied first and tests for small motion. Afterwards, the outer layer search serves as a guard line to catch large motion. It is used only when the inner search layer fails to find a good solution. Experimental results of motion estimation on various QCIF/CIF video sequences show that the proposed algorithm achieves image quality similar to diamond search but with the search point cost as low as cross-diamond-hexagonal search