• The KIPS Transactions:PartA
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• v.16A no.2
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• pp.89-100
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• 2009

With the advance in digital technologies and the increasing prevalence of high quality multimedia contents, there is a growing user demand for multimedia devices, such as mobile phones, digital TV, PMP, digital camcoders, digital cameras. Such devices provide various services associated with multimedia file manipulation, including multimedia contents playback, multimedia file editing, etc. Conventional file systems exhibit a performance-related drawback that requires considerable amount of time and disk I/Os in order to store large-sized edited multimedia files. This paper proposes a fast, efficient writing technique for large-sized edited multimedia files by using data block sharing with adjustment of inode block pointers. Our experiments show that the proposed scheme not only improves write performance of the Ext3 file system on average by 16 times with various types of edited multimedia files, but also reduces consumed disk space dramatically through the data block sharing.

• The KIPS Transactions:PartB
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• v.10B no.1
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• pp.87-94
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• 2003

A study on the characteristics of server workloads based on user access pattern offers insights for the strategies on continuous media caching and network workloads distribution. This paper analyses characteristics of continuous media filet in each fervor and user access requests to each of them, using log data of three commercial sites, which are providing continuous media files in the form of real time streaming on the Internet. These servers have more continuous files than ones in the previously reported studies and are processing very large number of user access requests. We analyse the characteristics of continuous media files in each server by the size of files. playback time and encoding bandwidth. We also analyse the characteristics of user access requests by the distribution of user requests to continuous media files, user access time, access rate based on the popularity of the files and the number if access requests to serial continuous media files.

• Journal of KIISE
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• v.42 no.8
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• pp.1039-1048
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• 2015

Recently, the web-based adaptive streaming service, DASH (Dynamic Adaptive Streaming over HTTP), is receiving more attention. However, existing network-based and buffer-based video quality control schemes in DASH environments make oscillation of segment throughput, causing degradation of the quality of experience (QoE) with frequent quality changes and playback interruptions because these schemes do not consider the content characteristics. In this paper, we propose a C-DASH (Content Characteristics based Dynamic Adaptive Streaming over HTTP) scheme in order to improve the QoE in DASH environments. The C-DASH scheme performs seamless and smooth quality control based on the segment throughput, buffer status, and segment size of the content. Based on simulation results, it is confirmed that the C-DASH scheme can improve the QoE, when compared with the existing quality control schemes.

• Journal of Korea Multimedia Society
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• v.10 no.2
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• pp.278-287
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• 2007

Even though a variety of types of multimedia data are being used on the basis of user characteristics and demands, all devices do not always support playing all multimedia data. Accordingly, a multimedia transcoder is used to create media suitable for each environments. This is due to the dissimilarity between the source QoS and the target QoS. Therefore, we need to consider adapting the two dissimilar QoS. Therefore in this paper, we create a suitable application-specific transcoding path with unit transcoders before performing the media transcoding in consideration of source QoS and target QoS. and the created transcoding path performs the transcoding. Here, creating a UTR(Unit Transcoder) conversion path that considers the transcoding possibility and the minimum of the UTR will allow the playback of various multimedia data with convenience. and The consideration of QoS allows users to use the multimedia easily.

• Journal of Convergence for Information Technology
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• v.7 no.2
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• pp.59-65
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• 2017

In order to realize the operation of the creative modular toy, it is required to record the motion and to read and repeat the motion. At this time, a control potentiometer is used to read the absolute angle of rotation of the toy motion output shaft. However, the unstable part of the sensing area of the potentiometer is present in a certain region, which may lead to instability of the motor control. In this paper, we propose an algorithm to find the absolute angle of one rotation by reading two stable potentiometers on one axis and reading each stable region. We also describe the correction algorithm that is needed to perform multiple rotations. The proposed method is applied to Topobo modular toys to record the operation and perform iterative operation. In addition, multi-turn operation is recorded and operated to suggest the usefulness of the proposed method. In the future, we will expand the functions of recording and playback through various actions.

• Journal of the Korea Society of Computer and Information
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• v.18 no.8
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• pp.53-64
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• 2013

The existing research on the QoS of the Streaming video system(SVS) adjust the video stream being sent from the network perspective, the focus is to prevent data loss and delay. The other hand, changing the quality of the video stream will not receive the guaranteed QoS from the perspective of the users who want uniform quality. In order to solve these problems, this paper applied to ensure that the benefits in the amount of bits per frame occurs Encoder CBR streaming video is kept constant and uniform picture quality advantages of VBR streaming video VBR to CBR Encoder and CBR to VBR Decoder, Video was designed to control the playback stream for And to ensure a uniform quality of the user based on the design and implementation of uniform quality guaranteed SVS. PSNR evaluated for several characteristics of the sample video to demonstrate the superiority of the SVS ensure uniform quality, the proposed Performance evaluation of the SVS ensure uniform quality CBW the ABR from 100% to ensure uniform image quality from 85% to environmental excellence is proved.

• Journal of the Korea Society of Computer and Information
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• v.25 no.6
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• pp.57-64
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• 2020

Video surveillance is consists of cameras, transmission devices, storage and playback devices, and is used for crime prevention and disaster monitoring. Recently, it has been spreading to a wide variety of fields, and has developed into an intelligent video surveillance system that can automatically recognize or track characteristic objects of people and things. The purpose of this study was to investigate the cases of video surveillance service applying the latest technology by dividing it into the home, public, and private sectors. also this study tried to investigate and research what advantage it brings from a business perspective. By looking at the cases introduced in this study, it was confirmed that the viedo security service is developing intelligently, such as excellent compatibility with CCTV, multiple video surveillance, CCTV screen motion detection, and alarm through automatic analysis.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.28 no.6
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• pp.1523-1537
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• 2018

The AI speaker is a simple operation that provides users with useful functions such as music playback, online search, and so the AI speaker market is growing at a very fast pace. However, AI speakers always wait for the user's voice, which can cause serious problems such as eavesdropping and personal information exposure if exposed to security threats. Therefore, in order to provide overall improved security of all AI speakers, it is necessary to identify potential security threats and analyze them systematically. In this paper, security threat modeling is performed by selecting four products with high market share. Data Flow Diagram, STRIDE and LINDDUN Threat modeling was used to derive a systematic and objective checklist for vulnerability checks. Finally, we proposed a method to improve the security of AI speaker by comparing the vulnerability analysis results and the vulnerability of each product.

• Journal of Broadcast Engineering
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• v.23 no.6
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• pp.813-823
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• 2018

UHD content is characterized by higher bandwidth requirements to provide seamless playback. The existing HTTP adaptive streaming scheme periodically requests video segment of lower quality than the available bandwidth in the steady state. In the steady state, the On-Off pattern is repeated due to the difference of the available bandwidth and the encoding rate of the content. And the repeated Off interval is causing the problem that can not efficiently use the available bandwidth. In the wireless environment where the delay and loss rate are higher with large bandwidth fluctuations, this problem is exacerbated because the available bandwidth is estimated inaccurately. Therefore, in this paper, we propose a segment scheduling scheme for efficient bandwidth utilization of UHD contents streaming in wireless environment. Proposed scheme is a group segment that simultaneously reqeusts multiple segments in one request message in order to reduce frequency of OFF interval. Through simulation, Our scheme improves bandwidth utilization.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.05a
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• pp.571-573
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• 2014

In today's technology streaming service's QoS technologiey is an issue. On quality video streaming service there are some technical issues exist, such as buffering. This submission is "Adaptive dual-streaming system design" which is for the integrity of the data streaming that is sent to TCP and UDP for faster transmission of data to the stream. This system provides real-time incoming video encoding in bitrate of h.264-based H through a process based on the video footage of several server and client-to-TCP and UDP via Adaptive providing streaming services in a network environment. This is an unspecified number of buffers in a network environment and continued through the minimization of various streaming for playback of videos and multimedia will be utilized in the field.