• 방송공학회논문지
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• 제13권1호
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• pp.25-33
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• 2008

영상통화는 3G 이동통신망에서 가장 대표적인 서비스이며, 많은 여러 분야에서 영상통화의 품질을 향상시키기 위한 노력이 있다. 국내에서도 SKT와 KTF에서 3G와 3.5G망으로 WCDMA 방식을 채택해 전국서비스를 시작하였고, 이미 백만 명 이상의 많은 사용자를 확보한 상태이다. 본 논문에서는 WCDMA 망에서의 영상통화방법에 대해 알아보고, 영상품질을 향상시키기 위해 회선망의 물리계층 정보를 이용하여 영상코덱에서 손실확산을 최소화 할 수 있는 슬라이스 그룹을 만드는 새로운 전송기법에 대해 제안하고 실험을 통해 성능을 평가해 보았다. 실험결과, 기존의 방법들보다 좀 더 회선 망과 영상코덱 사이의 동기화가 잘 이루어지고, 이를 통해 손실의 확산을 줄일 수 있는 결과를 보여준다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2008년도 하계종합학술대회
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• pp.77-78
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• 2008

With advent of 3G mobile communication services, video telephony becomes one of the major services. However, due to a narrow channel bandwidth, the current video telephony services have not yet reached a satisfied level. In this paper, we propose an ROI (Region-Of-Interest) based improvement of visual quality for video telephony services with the H.264|MPEG-4 Part 10 (AVC: Advanced Video Coding) codec. To this end, we propose a face detection and tracking method to define ROI for the AVC codec based video telephony. Experiment results show that our proposed ROI based method allowed for improved visual quality in both objective and subjective perspectives.

• Journal of Information Technology Applications and Management
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• 제17권1호
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• pp.107-125
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• 2010

The purpose of this research is to identify the critical factors influencing on the continuous use of video telephony service for mobile devices. An empirical analysis has been performed by using service quality, brand image, price, fun as influencing factors, and satisfaction and commitment as mediating factors. The partial least squares(PLS) methodology with 228 questionnaires has been conducted. The results indicated that brand image, price, and fun were mediated by satisfaction and commitment to have a statistically significant influence on continuous use of video telephony service. Service quality showed a significant effect on continuous use mediated by satisfaction while it did not show any influence through commitment. Based on the results, companies in the communication service industry should consider and focus on the improved brand image, appropriate fees, and individual preferences for fun for the successful marketing activities, and should also maintain amicable relations with their customers.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2008년도 하계종합학술대회
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• pp.361-362
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• 2008

Video quality is degraded by codec and transmission error. By analyses video pattern through NR(no reference) method, we get to aware that telephony video has particular blocking and blurring pattern and NR is suitable for telephony video quality testing. So NR will make contribution to enhancing video quality and monitoring video quality in advance.

• 한국멀티미디어학회논문지
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• 제13권4호
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• pp.560-574
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• 2010

3G 통신 기술의 상용화로 모바일 단말기 상에서 영상통화 서비스가 활발히 제공되고 있다. 하지만, 단말기 상에서 비디오 시스템은 안정성과 성능 면에서 사용자들의 요구를 충족시키지 못하고 있으며, 이 때문에 영상통화 서비스에 대한 사용자들의 불만이 증가하는 것이 현 실정이다. 따라서 본 논문에서는 기존의 제한된 모바일 영상통화 환경에서 향상된 품질의 영상통화 서비스를 제공하기 위한 비디오 압축 방법을 제안한다. 제안한 방법에서는 매 프레임마다 중요 객체와 비중요 객체를 분리하며, 분리된 객체는 다른 비트율과 화질을 갖도록 각 객체에 적합한 변환 커널을 적용하여 부호화 절차를 달리한다. 중요 객체는 고화질을 가지도록 부호화하며, 비중요 객체에 대해서는 저화질을 가지도록 부호화함으로써 제한된 대역폭 내에서 중요 객체에 대한 화질을 보장하도록 한다. 실험 결과에서 동일 비트율에서 제안한 방법이 기존 방법보다 중요객체 영역에 대한 화질이 우수한 것을 확인할 수 있었다.

• Journal of Information Processing Systems
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• 제18권1호
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• pp.1-11
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• 2022

Online video telephony systems have been increasingly used in several industrial areas because of coronavirus disease 2019 (COVID-19) spread. The existing session initiation protocol (SIP)-based video call system is being usefully utilized, however, there is a limitation that it is very inconvenient for users to transmit additional information during conversation to the other party in real time. To overcome this problem, an enhanced scheme is presented based on augmented real-time reality (AR). In this scheme, augmented information is automatically searched from the Internet and displayed on the user's device during video telephony. The proposed approach was qualitatively evaluated by comparing it with other conferencing systems. Furthermore, to evaluate the feasibility of the approach, we implemented a simple network application that can generate SIP call requests and answer with AR object pre-fetching. Using this application, the call setup time was measured and compared between the original SIP and pre-fetching schemes. The advantage of this approach is that it can increase the convenience of a user's mobile phone by providing a way to automatically deliver the required text or images to the receiving side.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2008년도 하계종합학술대회
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• pp.797-798
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• 2008

Visual quality of video telephony over 3G networks is not satisfactory due to limited bandwidths. Therefore, it is worthwhile to enhance subjective visual quality based on ROI coding. In this paper, we propose a rate-control algorithm for video telephony with ROI based H.264|AVC coding. The QP values are increasingly assigned in non-ROI away from the ROI so that graceful degradation of visual quality can be achieved, which is more visually pleasant.

• Journal of Information Technology Applications and Management
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• 제17권2호
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• pp.111-132
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• 2010

Korean telecommunications industry has a large scale market and boasts on high service quality and high technologies enough to provide the mobile video telephony service(the VTS) satisfactorily. For many years, Korean telecommunications companies have been investing enormous amount of money to advertise their VTS widely and to allow their customers to change their cell phones for the 3G(the third generation) devices indispensable for the VTS. However, despite their efforts, the VTS adoption rate in Korea is very low as of January, 2010 and it seems that customers seldom feel the necessity to use. From this viewpoint, it becomes necessary to identify antecedents influencing the intention to use for the VTS empirically. For this purpose, we have proposed several hypotheses from the perspective of the Value-based Adoption Model(VAM). We conducted a survey and found the several factors which influence the value perception of VTS.

• International Journal of Contents
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• 제8권1호
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• pp.16-22
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• 2012

In this paper we propose a method for verifying video in a video telephony system implemented in DM6446 DaVinci Processor. Each frame is categorized either error free frame or error frame depending on the predefined criteria. Human face is chosen as a basic means for authenticating the video frame. Skin color based algorithm is implemented for detecting the face in the video frame. The video frame is classified as error free frame if there is single face object with clear view of facial features (eyes, nose, mouth etc.) and the background of the image frame is not different then the predefined background, otherwise it will be classified as error frame. We also implemented the image histogram based NCC (Normalized Cross Correlation) comparison for video verification to speed up the system. The experimental result shows that the system is able to classify frames with 90.83% of accuracy.

• 산업기술연구
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• 제26권B호
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• pp.199-206
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• 2006

Internet telephony provides voice communication services with added flexibility for multimedia extension at a lower cost compared to traditional telephone systems. We implemented an internet telephony system as an overlay network without a centralized server, using a distributed hash table (DHT). Compared to the current server-based internet telephony system, our system is fault-tolerant, scalable, and can be flexible extended to various services and advanced to integrated service. To demonstrate the high flexibility of our DHT-based internet telephony system, we made our system cooperate with web servers. Web users can check up others' online stales and establish voice communication sessions to online users at a mouse click. This technology can be applied to more complex services such as multimedia messaging or video conference service.