Yazılım Mühendisliği Bölümü Yayın Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/2147
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Conference Object Recent Challenges in Video Coding and Streaming(2006) Choupanı, Roya; Choupani, R.; Tolun, M.R.; Tolun, Mehmet Reşit; Bilgisayar Mühendisliği; Yazılım MühendisliğiVideo streaming over the Internet has gained popularity during the recent years which is mainly the result of the introduction of video-conferencing and videotelephony. These in turn have made it possible to bring to life many applications such as transmitting video over the Internet and telephone lines, surveillance and monitoring, telemedicine (medical consultation and diagnosis at a distance), and computer based training and education. These applications need a large bandwidth which is not available in all cases. Many video encoding standards have been introduced to deal with video compression and transmission problems. In this study, we have discussed the main technical features of the most important video coding standards in a comparative approach. The appropriateness of these features is application and transmission environment dependant. Manipulating video stream features or video transcoding methods are discussed as well.Article Hand Gesture Recognition in Variable Length Sequences(2005) Choupanı, Roya; Choupani, R.; Tolun, M.R.; Tolun, Mehmet Reşit; Bilgisayar Mühendisliği; Yazılım MühendisliğiUsing hand gestures in human computer interaction has been a major challenge during the recent years. Many of the hand gesture recognition systems however, have been based on the recognition of hand postures and estimating the related gesture which is restricted to a few numbers of possible movements. However when dealing with applications such as understanding sign languages which include a large number of classes, an automatic learning method based on matching a sequence of postures with the characterizing feature sequence of each class is necessary. An important characteristic of this method is that each sample sequence of a class may have a variable length and different position of the key features. In this paper a syntactic method has been proposed for classifying the input sequences. An algorithm foe extracting the grammar of the method during training stage is also given.Conference Object Citation - WoS: 2Multiple Description Scalable Coding for Video Transmission Over Unreliable Networks(Springer-verlag Berlin, 2009) Choupanı, Roya; Choupani, Roya; Tolun, Mehmet Reşit; Wong, Stephan; Tolun, Mehmet R.; Bilgisayar Mühendisliği; Yazılım MühendisliğiDeveloping real time multimedia applications for best effort networks such as the Internet requires prohibitions against jitter delay and frame loss. This problem is further complicated in wireless networks as the rate of frame corruption or loss is higher in wireless networks while they generally have lower data rates compared to wired networks. On the other hand, variations of the bandwidth and the receiving device characteristics require data rate adaptation capability of the coding method. Multiple Description Coding (MDC) methods are used to solve the jitter delay and frame loss problems by making the transmitted data more error resilient, however, this results in reduced data rate because of the added overhead. MDC methods do not address the bandwidth variation and receiver characteristics differences. In this paper a new method based on integrating MDC and the scalable video coding extension of H.264 standard is proposed. Our method can handle both jitter delay and frame loss, and data rate adaptation problems. Our method utilizes motion compensating scheme and, therefore, is compatible with the current video coding standards such as MPEG-4 and H.264. Based on the simulated network conditions, our method shows promising results and we have achieved tip to 36dB for average Y-PSNR.Conference Object Citation - Scopus: 3Scalable Video Transmission Over Unreliable Networks Using Multiple Description Wavelet Coding(2011) Choupanı, Roya; Choupany, R.; Wong, S.; Tolun, M.; Bilgisayar MühendisliğiScalable video coding (SVC) and multiple description coding (MDC) are the two different adaptation schemes for video transmission over heterogenous and best-effort networks such as the Internet. We present a new approach to combine the advantages of SVC and MDC to provide reliable video communication over a wider range of communication networks and/or satisfy application requirements. Our proposed method utilizes 3D discrete wavelet transform and a modified embedded zero tree data structure to group the coefficients in different descriptions. The proposed method reduces the impact of the drift error by organizing the frames in a hierarchical structure. © 2011 AICIT.Conference Object Hierarchical SNR Scalable Video Coding with Adaptive Quantization for Reduced Drift Error(2015) Choupani, Roya; Wong, Stephan; Tolun, MehmetIn video coding, dependencies between frames are being exploited to achieve compression by only coding the differences. This dependency can potentially lead to decoding inaccuracies when there is a communication error, or a deliberate quality reduction due to reduced network or receiver capabilities. The dependency can start at the reference frame and progress through a chain of dependent frames within a group of pictures (GOP) resulting in the so-called drift error. Scalable video coding schemes should deal with such drift errors while maximizing the delivered video quality. In this paper, we present a multi-layer hierarchical structure for scalable video coding capable of reducing the drift error. Moreover, we propose an optimization to adaptively determine the quantization step size for the base and enhancement layers. In addition, we address the trade-off between the drift error and the coding efficiency. The improvements in terms of average PSNR values when one frame in a GOP is lost are 3.70(dB) when only the base layer is delivered, and 4.78(dB) when both the base and the enhancement layers are delivered. The improvements in presence of burst errors are 3.52(dB) when only the base layer is delivered, and 4.50(dB) when both base and enhancement layers are delivered.Article Citation - WoS: 6Citation - Scopus: 7An Island Parallel Harris Hawks Optimization Algorithm(Springer London Ltd, 2022) Dokeroglu, Tansel; Sevinc, EnderThe Harris hawk optimization (HHO) is an impressive optimization algorithm that makes use of unique mathematical approaches. This study proposes an island parallel HHO (IP-HHO) version of the algorithm for optimizing continuous multi-dimensional problems for the first time in the literature. To evaluate the performance of the IP-HHO, thirteen unimodal and multimodal benchmark problems with different dimensions (30, 100, 500, and 1000) are evaluated. The implementation of this novel algorithm took into account the investigation, exploitation, and avoidance of local optima issues effectively. Parallel computation provides a multi-swarm environment for thousands of hawks simultaneously. On all issue cases, we were able to enhance the performance of the sequential version of the HHO algorithm. As the number of processors increases, the suggested IP-HHO method enhances its performance while retaining scalability and improving its computation speed. The IP-HHO method outperforms the other state-of-the-art metaheuristic algorithms on average as the size of the dimensions grows.Article Citation - WoS: 4Citation - Scopus: 6A New Robust Harris Hawk Optimization Algorithm for Large Quadratic Assignment Problems(Springer London Ltd, 2023) Dokeroglu, Tansel; Ozdemir, Yavuz SelimHarris Hawk optimization (HHO) is a new robust metaheuristic algorithm proposed for the solution of large intractable combinatorial optimization problems. The hawks are cooperative birds and use many intelligent hunting techniques. This study proposes new HHO algorithms for solving the well-known quadratic assignment problem (QAP). Large instances of the QAP have not been solved exactly yet. We implement HHO algorithms with robust tabu search (HHO-RTS) and introduce new operators that simulate the actions of hawks. We also developed an island parallel version of the HHO-RTS algorithm using the message passing interface. We verify the performance of our proposed algorithms on the QAPLIB benchmark library. One hundred and twenty-five of 135 problems are solved optimally, and the average deviation of all the problems is observed to be 0.020%. The HHO-RTS algorithm is a robust algorithm compared to recent studies in the literature.Article Citation - WoS: 15Citation - Scopus: 15A Constraint Programming Approach To a Real-World Workforce Scheduling Problem for Multi-Manned Assembly Lines With Sequence-Dependent Setup Times(Taylor & Francis Ltd, 2024) Kandiller, Levent; Drake, John H.; Guner, Funda; Gorur, Abdul K.; Satir, BenhurFor over five decades, researchers have presented various assembly line problems. Recently, assembly lines with multiple workers at each workstation have become very common in the literature. These lines are often found in the manufacturing of large vehicles, where workers at a workstation may perform their assigned tasks at the same time. Most research on multi-manned assembly lines focuses on balancing tasks and workers among workstations and scheduling tasks for workers. This study, however, concentrates on assigning tasks to workers already assigned to a specific workstation, rather than balancing the entire line. The problem was identified through an industrial case study at a large vehicle manufacturing company. The study presents two methods, one using mixed integer linear programming and the other using constraint programming, to minimise the number of workers required on a multi-manned assembly line with sequence-dependent setup times. The results of the computational experiments indicate that the constraint programming method performs better than the mixed integer linear programming method on several modified benchmark instances from the literature. The constraint programming model is also tested on the real-world scenario of our industrial case study and leads to significant improvements in the productivity of the workstations.Conference Object Optimized Multiple Description Coding for Temporal Video Scalability(Springer Verlag, 2013) Choupani, R.; Wong, S.; Tolun, M.The vast application of video streaming over the Internet requires video adaptation to the fluctuations of the available bandwidth, and the rendering capabilities of the receiver device. On the other hand, the available video coding standards are designed for optimum bit rate which makes them susceptible to packet losses. A combination of video adaptation methods and error resilient methods can make the video stream more robust against networking problems. In this paper, an optimization for combining scalable video coding with multiple description coding schemes have been proposed. Our proposed method is capable of creating balanced descriptions with optimum coding efficiency.Conference Object Citation - Scopus: 1Component-Based Project Estimation Issues for Recursive Development(Springer, 2008) Altunel, Yusuf; Tolun, Mehmet R.In this paper we investigated the component-based specific issues that might affect project cost estimation. Component-based software development changes the style of software production. With component-based approach the software is developed as the composition of reusable software components. Each component production process must be treated as a stand-alone software project, which needs individual task of management. A typical pure component-based development can be considered as decomposition/integration activities successively applied at different levels and therefore results in recursive style of development. We analyzed and presented our results of studies on the component-based software development estimation issues from recursive point of view.