• Proceedings of the IEEK Conference
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• 2001.09a
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• pp.297-300
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• 2001

본 논문에서는 동영상의 계층적 부호화의 효율을 높이기 위한 방안에 대해 연구하였다. 단일 계층부호화에 비해 다 계층부호화는 계산량이 많아진다. 따라서 계층적 부호화의 장점을 살리고 단점을 보완하는 방안을 제시하였다. 우선 인코더에서 고급계층의 복잡도를 줄이기 위하여 고급계층의 참조 형태를 P-VOP (Prediction-Video Object Plane)만으로 정한다. 고급계층의 참조 영역으로 사용되는 업샘플링된 VOP의 횟수를 줄여서 업샘플링에 따른 계산량을 줄인다. 그리고 고급계층의 비트율을 조절하여 Traffic shaping 효과도 얻을 수 있다. 이러한 방법들을 통해 단일 계층 부호화에 비해 다 계층부호화의 장점을 살리고 단점을 보완하는 코덱을 제안한다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.12
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• pp.1068-1071
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• 2007

When a dielectric layer, in-cell retarder (ICR) is formed between electrode and LC layer to get a single gap transflective fringe-field switching (FFS) display, the operating voltage ($V_{op}$) is highly increased due to the thickness of dielectric material. But, we also knew the phenomenon that the increasing rate of Vop is different whether the 1st common electrode was composed of plate type or slit type. In this paper, the common electrode in transmissive part was composed of slit type which had less steepness effect of the Vop and in reflective part was composed of plate type. The rubbing angle of reflective part can be adjusted properly to match the voltage dependent transmittance and reflectance.

• Proceedings of the Korea Information Processing Society Conference
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• 2003.05a
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• pp.71-74
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• 2003

본 연구는 MPEG-4 시스템 파일 포맷인 MP4 파일 포맷을 분석하여 I-VOP(Intra - Video Object Plane)의 추출 암호화를 통한 DRM 솔루션을 설계 및 구현하였다. 또한, 구현을 통해 암호화 정보를 포함한 DRM 정보를 MPEG-4 데이터 내부에 삽입하여 스트리밍 서비스에 DRM을 적용시키는 방안을 제시하였다. I-VOP의 암호화는 가장 효율적인 데이터 암호화 방안으로 전체 데이터를 암/복호화 하는데서 생기는 시스템 부하를 최소화 시친 수 있다. 플레이어는 스트리밍 패킷을 밭음과 동시에 데이터의 암호화 유 무를 확인하고, DRM 정보를 이용하여 복호화 시킴으로써 인터넷 방송용 MPEG-4 스트리밍 데이터의 저작권 보호를 실현한다.

• Proceedings of the Korea Information Processing Society Conference
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• 2004.05a
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• pp.1043-1046
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• 2004

본 논문에서는 MPEG-4 스트림의 디지털 저작권 관리(DRM)를 위한 암호화 방법을 제안한다. MPEG-4는 멀티미디어 스트리밍을 위한 표준이며 MPEG-4 파일 포맷에 따라 저장된다. 인가된 사용자들만 접근이 가능하도록 MPEG-4 파일 포맷으로부터 추출된 I-VOP, P-VOP의 매크로 블록(MB)들과 모션 벡터(MV)들을 암호화 하는 3가지 방법을 설계하였고, MPEG-4 데이터의 암호화에는 DES(Data Encryption Standard)를 사용하였다. 이러한 암호화 방법을 기반으로 MPEG-4 데이터 스트리밍을 위한 인터넷 방송 서비스용 DRM 솔루션을 구현하고, 최적의 암호화 방법을 선택하기 위해 복호화 속도 및 영상의 품질을 비교하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.2C
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• pp.147-161
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• 2003

Video object segmentation is one of the core technologies for content-based real-time MPEG-4 encoding system. For real-time requirement, the segmentation algorithm should be fast and accurate but almost all existing algorithms are computationally intensive and not suitable for real-time applications. The MPEG-4 VM(Verification Model) has provided basic algorithms for MPEG-4 encoding but it has many limitations in practical software development, real-time camera input system and compression efficiency. In this paper, we implemented the preprocessing system for real-time camera input and VOP extraction for content-based video coding and also implemented motion detection to achieve the 180 : 1 compression rate for real-time and high compression MPEG-4 encoding.

• The KIPS Transactions:PartC
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• v.12C no.2 s.98
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• pp.175-182
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• 2005

This paper presents encryption techniques for digital right management solutions of MPEG-4 streams. MPEG-4 is a format for multimedia streaming and stored in the MPEG-4 file format. We designed three kinds of encryption methods, which encrypt macro blocks (MBs) or motion vectors (MVs) of I-, P-VOPs (Video Object Planes), extracted from the MPEG-4 file format. We used DES to encrypt MPEG-4 data Based on theses three methods, we designed and implemented a DRM solution for an Internet broadcasting service, which enabled a MPEG-4 data streaming, and then compared the results of decryption speed and quality of rendered video sequences to get an optimal encryption method.

• The KIPS Transactions:PartC
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• v.13C no.2 s.105
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• pp.241-248
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• 2006

Mobile computing has such characteristics as portability, wireless network, mobility, etc. These characteristics cause various problems to mobile terminals like frequent disconnection, high error rate, and varying network status. These problems motivate us to develop an adaptive error control mechanism for supporting multimedia service in mobile computing environment. In this paper, we propose the Adaptive Error Control(AEC) scheme using client's buffer size and current error rate. After categorizing the status into four groups according to client's buffer size and current error rate, this scheme applies an appropriate error control scheme to each status. In this scheme, thresholds of buffer size and error rate are determined by the data transmission time, play rate and average VOP size, and by the probability of error for a sequence of packets. The performance of proposed scheme is evaluated by flaying MPEG-4 files on an experimental client/server environment, respectively. The results show that error correcting rate is similar to other schemes while the time for correcting error reduce a little. In addition, the size of data for correcting error is decreased by 23% compared with FEC and Hybrid FEC, respectively. Theses results demonstrate that the proposed scheme is more suitable in mobile computing environment with small bandwidth and varying environment than existing schemes.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.41 no.1
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• pp.13-20
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• 2004

In this paper, we have analyzed the current MPEG-4 video encoding tools and proposed efcient coding techniques that reduce the complexity of the encoder. Until recently, encoder optimization without shape coding has been a major concern in video for wire/wireless low bit rate coding services. Recently, we found out that the computational complexity of MPEG-4 shape coding plays a very important role in the object-based coding through experiments. We have made an experiment whether we could get optimized object-based coding method through successfully combining latest optimized texture coding techniques with our proposed optimized shape coding techniques. In texture coding, we applied the MVFAST method for motion estimation. We chose not to use IVOPF(Intelligent VOP Formation) but to use TRB(Tightest Rectangular Boundary) for positioning VOP and, finally, to eliminate the spiral search of shape motion estimation to reduce the complexity in shape coding. As a result of experiment, our proposed scheme achieved improved time complexity over the existing reference software by $57.3\%$ and over the optimized method on which only shape coding was applied by $48.7\%$, respectively.

• Proceedings of the IEEK Conference
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• 2000.09a
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• pp.523-526
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• 2000

본 논문에서는 임의의 모양을 가지는 영상 객체(image object)에 적용 가능한 모양적응 이산변환(PSADT : Polar coordinates shape adaptive discrete transform)에 기반한 새로운 워터마킹 기법을 제안한다. 대수-극 좌표계(log-polar coordinates)와 모양적응 이산변환을 이용하여 제안된 기법은 MPEG-4의 VOP와 같은 임의의 모양을 가지는 영상 객체에 적용할 수 있을 뿐만 아니라 기존 기법에 비하여 회전과 크기 변화와 같은 기하학적인 공격에 대하여 우수한 강인성을 제공한다.

• Journal of Broadcast Engineering
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• v.2 no.2
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• pp.146-155
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• 1997

The new video coding standard Iv1PEG-4 is enabling content-based functionalities. It requires a prior decomposition of sequences into video object planes (VOP's) so that each VOP represents moving objets. This paper addresses an image segmentation method for separating moving objects from still background (non-moving area) in video sequences using a statistical hypothesis test. In the proposed method. three consecutive image frames are exploited and a hypothesis testing is performed by comparing two means from two consecutive difference images. which results in a T-test. This hypothesis test yields a change detection mask that indicates moving areas (foreground) and non-moving areas (background), Moreover. an effective method for extracting