Ravindra Kumar Purwar

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.

A matching criterion for motion compensation in the temporal coding of video signal

Video data have spatial as well as temporal redundancy and motion estimation plays a vital role in the removal of temporal redundancy of video data. Block matching techniques are mostly used and generally the matching criterion in these block matching techniques is the mean absolute error (MAE). Though MAE-based approach is simple and less complex, it does not give better prediction specially for large motion video inputs with contrast variation. In this manuscript, a new block matching criterion has been suggested and experimentally compared with three existing methods in terms of four parameters—average MAE/pixel, average search points/block, average peak signal to noise ratio (PSNR) and average number of bits/pixel value. Proposed criterion gives nearly 75% less average error than conventional MAE. An increase of nearly 16% in average PSNR value and 37% reduction in average bits/pixel value in comparison to MAE has been observed for the proposed criterion. Further, these criterions have also been evaluated for quality/compression ratio which is nearly 80% more for the proposed criterion than corresponding MAE metric.

A Quality Based Motion Estimation Criterion for Temporal Coding of Video

In video compression, motion compensation techniques are used for removal of temporal redundancy and it is the block based matching concept which is most popular among them. In such matching techniques, Mean Absolute Difference (MAD) is widely accepted as the matching criterion because of its simplicity and low computation. Since MAD considers only average error value in a block for matching purposes while ignoring individual difference between the pixels, the matching may not be more accurate. In this paper, a new block matching criterion is being suggested and is experimentally compared with two other matching criterions including MAD, using four parameters and the results are better for the proposed one.

A Novel Approach of Digital Video Encryption

the recent years with the development of internet technologies, video technologies have been broadly used in TV, communication and multimedia, So security is required on video data. Although much video encryption technique has been develop but not give so much efficiency in terms of encryption and decryption process. However, they are more complex to implement as a system and are difficult to be applied in a widespread manner. Here we propose a new novel scheme for digital video encryption. In this paper we give a method to generate an encrypted video by encrypted Video-frame. Based on novel secure video scheme, an effective and generalized scheme of video encryption. It is a matrix computation scheme which uses a concept of Video- frame and xor() operation. This paper proves that proposed scheme is able to fully encrypt the video frame and have a better performance that can be measured by different Parameters. Further we can extend our approach into a digital video stenography.

A better approach for object tracking using dual-tree complex wavelet transform

One of the most crucial tasks in content based video coding is the object retrieval and its tracking in subsequent frames. A number of algorithms for object tracking using real wavelet transforms have been proposed in literature. Major deficiencies in these algorithms are due to shift variance and directional selectivity problem of the real wavelet transforms. In this paper an algorithm for object tracking using dual-tree complex wavelet transform has been proposed which removes these problems of real wavelet transforms, experimental results show that the proposed algorithm is better than existing wavelet transform based.

A block matching criterion for interframe coding of video

Interframe coding is used for removal of temporal redundancy in video data and motion compensation plays a very significant role in the interframe coding of such data. Motion compensation based on block matching technique generally uses the criterion of either minimum Mean Square Error (MSE)/ Mean Absolute Difference (MAD) value to find the suitable motion vector. Vector Matching Criterion (VMC) is another such method for motion compensation in the literature. In this manuscript, a new matching criterion for block based motion compensation is being proposed and compared with other existing techniques. The experimental results show that the proposed criterion of block matching gives excellent results in comparison to the existing criterion of block matching techniques.

Improved Accuracy in Initial Search Center Prediction to Fasten Motion Estimation in h.264/AVC

ABSTRACT In this paper, a new two-step approach for enhancing the accuracy of initial search center (ISC) prediction in h.264 has been proposed which improves the speed of motion estimation in video encoding. Previous methods for estimating the ISC worked in a single step by finding the mean/median of motion vectors (MVs) of neighboring blocks of the current and reference frames. The major drawback of all the existing ISC techniques is that they consider the participation of all the neighboring blocks with equal probability without taking into account their correlation with the current block. The blocks which have least correlation or no correlation at all affect the accuracy of prediction and hence increase the chances of trapping the search in local minima. Moreover, in the existing ISC prediction techniques, participation of MVs of restricted neighboring blocks is considered, which further limits the prediction accuracy. To elevate these drawbacks, a new two-step approach has been presented. The first step of the method works by identifying some candidate blocks for ISC and the second phase refines the search to obtain best possible ISC. Use of all the surrounding blocks from spatial and temporal frame along with the refinement stage has improved the accuracy. Simulation results clearly show the enhancement in accuracy of ISC prediction, improvement in video quality in terms of peak signal-to-noise ratio (PSNR) and reduction in the number of search steps. Most recent approach in ISC prediction has shown an improvement of 11.7% as compared to standard median predictor, whereas the proposed technique shows an improvement of almost 50%. The reduction in search points is nearly 40%–50% compared to standard median predictor for fast-motion sequences. Also the proposed technique works equally well for fast, medium, slow, cif, qcif and HD video sequences as indicated in the results.

Handwritten Hindi character recognition: a review

As the years passed by, computers became more powerful and automation became the need of generation. Humans tried to automate their work and replace themselves with machines. This effort of transition from manual to automatic gave rise to various research fields, and document character recognition is one such field. From the last few years, there is a sincere contribution from researchers for the development of optical character recognition systems for various scripts and languages. As a result of intensive research and development, there has been a significant improvement in handwritten devnagari text recognition. The main focus of this study is detailed survey of existing techniques for recognition of offline handwritten Hindi characters. It addresses all the aspects of Hindi character recognition starting from database to various phases of character recognition. The most relevant techniques of preprocessing, feature extraction and classification are discussed in various sections of this study. Moreover, this study is a zest of work accepted and published by research community in recent years. This study benefits its readers by discussing limitations of existing techniques and by providing beneficial directions of research in this field.

Hindi handwritten character recognition using multiple classifiers

Humans can easily recognize handwritten words, after gaining basic knowledge of languages. This knowledge needs to be transferred to computers for automatic character recognition. The work proposed in this paper tries to automate recognition of handwritten hindi isolated characters using multiple classifiers. For feature extraction, it uses histogram of oriented gradients as one feature and profile projection histogram as another feature. The performance of various classifiers has been evaluated using theses features experimentally and quadratic SVM has been found to produce better results.

A new fast motion estimation algorithm using adaptive size diamond pattern search with early search termination

In this paper, a new dynamic zero motion prejudgment (ZMP) with adaptive diamond pattern search-based algorithm is suggested to enhance the search efficiency and accuracy of motion estimation (ME) in video coding. Firstly, a dynamic ZMP technique is proposed for early identification of the stationary blocks. For non-stationary blocks, a new initial search centre prediction technique is suggested. This new search centre has high probability to be near actual MV. Its distortion is compared against a dynamically predicted threshold to check if this location could be the position of actual MV. If so, search is terminated thereafter, otherwise a variable size diamond pattern is suggested to swiftly attain the global minima. Experimental results show 95% to 99% speed gain of proposed algorithm with only 0.007-0.7 dB PSNR and 0.0001-0.0073 SSIM degradation over full search. Also, the proposed algorithm shows very promising results over other fixed and dynamic search algorithms.