• Journal of Korea Society of Digital Industry and Information Management
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• v.11 no.4
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• pp.81-87
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• 2015

Recently, with the development of the ICT environment, the use of the software is growing rapidly. And the number of the web server software used with a variety of users is also growing. However, There are also various damage cases increased due to a software security vulnerability as software usage is increasing. Especially web shell hacking which abuses software vulnerabilities accounts for a very high percentage. These web server environment damage can induce primary damage such like homepage modification for malware spreading and secondary damage such like privacy. Source code weaknesses checking system is needed during software development stage and operation stage in real-time to prevent software vulnerabilities. Also the system which can detect and determine web shell from checked code in real time is needed. Therefore, in this paper, we propose the system improving security for web server by detecting web shell attacks which are invisible to existing detection method such as Firewall, IDS/IPS, Web Firewall, Anti-Virus, etc. while satisfying existing secure coding guidelines from development stage to operation stage.

• Proceedings of the IEEK Conference
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• 2001.06d
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• pp.41-44
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• 2001

Variable length coding (VLC) has been used in many well known standard video coding algorithms such as MPEG and H.26x. However, VLC can not be processed parallelly because of its sequentiality. This sequentiality is a big barrier for implementing a real-time software video codec since parallel schemes can not be applied. In this paper, we propose a new fast VLD (Variable Length Decoding) method based on the probabilistic distribution of symbols in VLC tables used in MPEG as well as H.263 standard codecs. Even though MPEG suggests the table partitioning method, they do not show theoretically why the number of partitioned tables is two or three. We suggest the method for deciding the number of partitioned tables. Applying our scheme to several well-known MPEG-2 test sequences, we can reduce the computational time up to about 10% without any sacrificing video quality

• Journal of Digital Contents Society
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• v.9 no.4
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• pp.687-695
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• 2008

One of the most significant characteristics of remote real time lecture, the emerging still image standard, is the OOI (Object of Interest) coding. The functionality of OOI is important in applications where certain parts of the image are more important than others. In such cases, these objects need to be encoded at higher quality than the background. JPEG2000 provides a number of OOI coding mechanisms. Many researchers have actively studied the preferred processing from the OOI coding methods to the new methods complementing them. But, there do not exist OOI coding methods suitable for all applications. Therefore, this study shows a criterion to select according to the application requirements for applying the best OOI coding method in JPEG2000 applications, and also shows the experimental results deciding the best parameters in the selected methods.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.9
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• pp.1838-1847
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• 1994

Until recently, they decided the standard of the digital mobile communication speech coding method and competively developed the more detailed techniques in North America, Europe, Japan, etc. But, we have not yet determined. In this paper, we compared the RPE-LTP speech coding algorithm, standard in Europe, with the VSELP speech coding algorith, standard in North America, with respect to the soruce coding. We described the comprehensive verification and comparison with each speech coder, and discussed the improvement plan. Next, we also compared the number of computations which affects the real time processing seriously. Moreover, we performed the simulation with the Korean speech data, concreting the algorithm of each speech coder. Finally, we compared the performance of each speech coder with segmental SNR and 5-point MOS. The number of computations was calculated, and the result was that the number of multiplication computing times of VSELP speech encoder was the largest. With 26 speech data, the segmental SNR of VSELP was calculated larger than that of RPE-LTP. The 5-point MOS test was performed, and the result was that the basic speech quality of VSELP was equivalent or better than that of RPE-LTP.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.44 no.3
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• pp.88-96
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• 2007

H.264 is a new international video coding standard that can achieve considerably higher coding efficiency than conventional standards. Its coding gain has been achieved by employing advanced video coding methods. Specially, the increased number of macroblock modes and the complex mode decision procedure using the Lagrangian optimization are the main factors for increasing coding efficiency. Although H.264 obtains improved coding efficiency, it is difficult to do an real-time encoding because it considers all coding parameters in the mode decision procedure. In this paper, we propose a fast mode decision algorithm which classifies the macroblock modes in order to determine the optimal mode having low complexity quickly. Simulation results show that the proposed algorithm can reduce the encoding time by 34.95% on average without significant PSNR degradation or bit-rate increment. In addition, in order to show the validity of simulation results, we set up a low boundary condition for coding efficiency and complexity and show that the proposed algorithm satisfies the low boundary condition.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.2
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• pp.408-427
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• 2011

Intensive computational complexity is an obstacle of enabling multiview video coding for real-time applications. In this paper, we present a fast macroblock (MB) mode selection algorithm for B frames which are based on the computational complexity analyses between the MB mode selection and reference frame selection. Three strategies are proposed to reduce the coding complexity jointly. First, the temporal correlation of MB modes between current MB and its temporal corresponding MBs is utilized to reduce computational complexity in determining the optimal MB mode. Secondly, Lagrangian cost of SKIP mode is compared with that of Inter $16{\times}16$ modes to early terminate the mode selection process. Thirdly, reference frame correlation among different Inter modes is exploited to reduce the number of reference frames. Experimental results show that the proposed algorithm can promote the encoding speed by 3.71~7.22 times with 0.08dB PSNR degradation and 2.03% bitrate increase on average compared with the joint multiview video model.

• Current Optics and Photonics
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• v.2 no.6
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• pp.532-539
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• 2018

Multiple LED arrays can be utilized in visible-light communication (VLC) to improve communication efficiency, while maintaining smart illumination functionality through dimming control. This paper proposes a modulation scheme called "Spatial Intensity Modulation" (SIM), where the effective number of turned-on LEDs is employed for data modulation and dimming control in VLC systems. Unlike the conventional pulse-amplitude modulation (PAM), symbol intensity levels are not determined by the amplitude levels of a VLC signal from each LED, but by counting the number of turned-on LEDs, illuminating with a single amplitude level. Because the intensity of a SIM symbol and the target dimming level are determined solely in the spatial domain, the problems of conventional PAM-based VLC and related MIMO VLC schemes, such as unstable dimming control, non uniform illumination functionality, and burdens of channel prediction, can be solved. By varying the number and formation of turned-on LEDs around the target dimming level in time, the proposed SIM scheme guarantees homogeneous illumination over a target area. An analysis of the dimming capacity, which is the achievable communication rate under the target dimming level in VLC, is provided by deriving the turn-on probability to maximize the entropy of the SIM-based VLC system. In addition, a practical design of dimmable SIM scheme applying the multilevel inverse source coding (MISC) method is proposed. The simulation results under a range of parameters provide baseline data to verify the performance of the proposed dimmable SIM scheme and applications in real systems.

• Smart Media Journal
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• v.12 no.11
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• pp.145-153
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• 2023

In a P2P-based distributed storage system where peers frequently join and leave, it is essential to guarantee not only data availability but also playback quality comparable to that provided by local storage devices when playing back video files with real-time constraints. In addition, cloud storage services based on distributed storage systems provide each user with the functionality to share their files with other users, so when multiple users request playback of the same video file at the same time, all playback should be supported seamlessly in real time. Therefore, in this paper, we propose a scheme that process multiple simultaneous playback requests for each video file in real time as well as data availability in a P2P-based distributed storage system that supports file sharing. This scheme can support real-time simultaneous playback and efficiently use storage space by adjusting the amount of redundant data encoded through erasure coding according to the number of concurrent playback requests for each video file.

• Journal of Broadcast Engineering
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• v.11 no.4 s.33
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• pp.386-395
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• 2006

Multi-view video coding technology demands the very high efficient coding technologies, because it has to encode a number of video sequences which are achieved from a number of video cameras. For this purpose, multi-view video coding introduces the inter-view prediction scheme between different views, but it shows a limitation of coding performance enhancement by adopting only new prediction method. Accordingly, we are going to achieve the more coding performance by enhancing dequantizer perfermance. Multi-view video coding is implemented basically based on H.264/AVC and uses the same quantization/de-quantization method as H.264/AVC does. The conventional quantizer and dequantizer is designed with the assumption that input residual signal follows the Laplacian PDF. However, it doesn't follow the fixed PDF type always. This mismatch between assumption and real data causes degradation of coding performance. To solve this problem, we propose the efficient de-quantization method based on quantized coefficients distribution at decoder without extra information. The extensive simulation results show that the proposed algorithm produces maximum $1.5\;dB{\sim}0.6\;dB$ at high bitrate compared with that of conventional method.

• Journal of Broadcast Engineering
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• v.20 no.3
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• pp.388-397
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• 2015

High Efficiency Video Coding (HEVC)/H.265 is a new video coding standard which is known as high compression ratio compared to the previous standard, Advanced Video Coding (AVC)/H.264. Due to achievement of high efficiency, HEVC sacrifices the time complexity. To apply HEVC to the market applications, one of the key requirements is the fast encoding. To achieve the fast encoding, exploiting thread-level parallelism is widely chosen mechanism since multi-threading is commonly supported based on the multi-core computer architecture. In this paper, we implement both the Tile-level parallelism and the Frame-level parallelism for HEVC encoding on multi-core platform. Based on the implementation, we present two approaches in combining the Tile-level parallelism with Frame-level parallelism. The first approach creates the fixed number of tile per frame while the second approach creates the number of tile per frame adaptively according to the number of frame in parallel and the number of available worker threads. Experimental results show that both improves the parallel scalability compared to the one that use only tile-level parallelism and the second approach achieves good trade-off between parallel scalability and coding efficiency for both Full-HD (1080 x 1920) and 4K UHD (3840 x 2160) sequences.