• Journal of information and communication convergence engineering
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• v.10 no.3
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• pp.315-320
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• 2012

In H.264/AVC, the first frame of a group of pictures (GOP) is encoded in intra mode which generates a large number of bits. The number of bits for the I-frame affects the qualities of the following frames of a GOP since they are encoded using the bits remaining among the bits allocated to the GOP. In addition, the first frame is used for the inter mode encoding of the following frames. Thus, the initial quantization parameter (QP) affects the following frames as well as the first frame. In this paper, an adaptive peak signal to noise ratio (PSNR)-based initial QP determination algorithm is presented. In the proposed algorithm, a novel linear model is established based on the observation of the relation between the initial QPs and PSNRs of frames. Using the linear model and PSNR results of the encoded GOPs, the proposed algorithm accurately estimates the optimal initial QP which maximizes the PSNR of the current GOP. It is shown by experimental results that the proposed algorithm predicts the optimal initial QP accurately and thus achieves better PSNR performance than that of the existing algorithm.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.3C
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• pp.147-152
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• 2005

In this paper, we proposed a method for compressing the static video test patterns in high quality to test the picture quality in DTV. In our method, we use the fact that the generated bits and average quantization value have almost identical distribution characteristics per each GOP and we propose a new target bit allocation method suitable for compressing the static test pattern while the target bit allocation method in MPEG-2 TM5 is suitable for the moving picture. The proposed target bit allocation method is to maintain the high quality video continuously by using the normalized complexities which are updated or maintained by means of picture qualities at each GOP. Experiment result showed that the test pattern stream encoded by MPEG-2 software with the proposed algorithm had a stable bit rate and good video quality during the decoding process.

• Journal of Broadcast Engineering
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• v.11 no.4 s.33
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• pp.420-430
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• 2006

In this paper, we propose a flexible GGOP prediction structure to improve coding efficiency for multi-view video coding. In general, reference software used for MVC uses the fixed GGOP prediction structure. However, the performance of MVC depends on the base view and numbers of B-pictures between I-picture(or P-picture) and P-picture. In order to implement the flexible GGOP prediction structure, the location of base view is decided according to the global disparities among the adjacent sequences. Numbers of B-pictures between I-picture(or P-picture) and P-picture are decided by camera arrangement such as the baseline distance among the cameras. The proposed method shows better result than the reference software of MVC. The proposed prediction structure shows considerable reduction of coded bits by 7.1%.

• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.12
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• pp.1447-1454
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• 2014

In H.264 standard, an intra frame is the first frame of a GOP (Group of Pictures) and all macroblocks of an intra frame are encoded using the same quantization parameter. In addition, an intra frame is used for encoding the following frames of the same GOP so the encoding results of an intra frame affect the encoding results of the entire GOP. Thus, it is important to find the optimal quantization parameter of an intra frame for improving the quality of a GOP. In this paper, we propose an searching method for an optimal quantization parameter of an intra frame in real time. The proposed method uses a gradient descent method to find the optimal value based on characteristics of the optimal quantization parameters. Experimental results show that the proposed method captures the characteristics of the optimal quantization parameter and accurately estimates the optimal value.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2016.11a
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• pp.107-109
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• 2016

본 논문에서는 4K UHD 입력 영상을 실시간으로 부호화하기 위해 적용되는 GOP 단위 또는 IDR 주기 단위의 병렬 부호화 구조를 지원하도록 R-${\lambda}$ 모델 기반의 율 제어 방법을 개선하는 비트 분배(bit allocation) 방법을 제안한다. GOP 단위 또는 IDR 주기 단위의 병렬 부호화기 내에서 율 제어기를 작동시키는 경우, 계층적 B 구조에서 같은 계층에 있는 프레임 간에는 상호간에 얼마만큼의 비트를 소모 하였는지에 대한 정보를 공유 할 수 없기 때문에 기존의 비트 분배 방식으로는 비트 예산(bit budget) 관리가 불가능하다. 이를 해결하기 위해 본 논문에서는, 기존의 R-${\lambda}$ 모델 기반 율 제어 방법을 개선하여 부호화 순서에 의한 시간 순서 방향의 비트 예산 갱신 기반 비트 분배하던 방식으로부터, GOP 마다 비트를 할당한 후 계층적 B 구조에서의 계층이 깊어지는 방향으로 비트 예산을 갱신하여 비트를 분배하는 방식으로 율 배분 방식을 개선하였다. 실험 결과를 통해 R-${\lambda}$ 모델 기반 율 제어의 기존 비트 분배 방식보다 제안 방법에 의한 목표 비트 율 달성 오차가 감소함을 확인하였다.

• Journal of Broadcast Engineering
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• v.22 no.2
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• pp.193-206
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• 2017

In this paper, we propose a rate control method based on the $R-{\lambda}$ model that supports a parallel encoding structure in GOP levels or IDR period levels for 4K UHD input video in real-time. For this, a slice-level bit allocation method is proposed for parallel encoding instead of sequential encoding. When a rate control algorithm is applied in the GOP level or IDR period level parallelism, the information of how many bits are consumed cannot be shared among the frames belonging to a same frame level except the lowest frame level of the hierarchical B structure. Therefore, it is impossible to manage the bit budget with the existing bit allocation method. In order to solve this problem, we improve the bit allocation procedure of the conventional ones that allocate target bits sequentially according to the encoding order. That is, the proposed bit allocation strategy is to assign the target bits in GOPs first, then to distribute the assigned target bits from the lowest depth level to the highest depth level of the HEVC hierarchical B structure within each GOP. In addition, we proposed a processing method that is used to improve subjective image qualities by allocating the bits according to the coding complexities of the frames. Experimental results show that the proposed bit allocation method works well for frame-level parallel HEVC software encoders and it is confirmed that the performance of our rate controller can be improved with a more elaborate bit allocation strategy by using the preprocessing results.

• Journal of Broadcast Engineering
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• v.6 no.2
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• pp.131-138
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• 2001

We have proposed a transcoder which converts the MPEG-2 422P@ML bitstream into MPEG-2 422P@ML bitstream. properties of the MPEG-2 422P@ML profile and requirements for the transcoder are analyzed for the proposed transcoder. The MPEG-2 422P@ML profile permits several GOP structures, each of which has little resemblance. Such different GOP structures lead to a complicated transcoder which includes motion estimation, and have limited use of the side information in the bitstream. By computer simulations, we showed that the results of the transcoding is as good as that of the direct coder by MPEG-2 422P@ML.

• Proceedings of the Korea Contents Association Conference
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• 2009.05a
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• pp.861-864
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• 2009

디지털 콘텐츠는 원본을 훼손하지 않고 복제 및 인터넷을 통한 배포가 가능하기 때문에 콘텐츠에 대한 지적 재산권 보호 할 수 있는 장치는 필수적이다. 본 논문에서는 디지털 콘텐츠의 지적 재산권을 보호할 수 있는 강인한 워터마킹 방법을 제안한다. 제안한 방법은 최신의 비디오 압축방법인 H.264에서 GOP(group of picture)내에서 시각적으로 민감하지 않고, 에러 전파를 할 수 없는 GOP의 프레임에 워터마크 강도를 크게 하고, 그렇지 않은 프레임에는 워터마크 강도를 상대적으로 낮추어 적은 화질열화에 비해 상대적으로 검출율이 높아 질 수 있도록 하였다. 실험 결과 H.264의 압축에서 높은 검출률을 보였고, 프레임별 화질 열화는 존재하지만 비디오를 재생하여 시각적인 테스트를 할 경우 화질 열화가 숨겨짐을 보였다. 제안하는 방법은 콘텐츠의 지적 재산권을 보호하기 위한 응용프로그램을 필요로 하는 DVD 제작자, IPTV 방송국과 같은 곳에 필요로 할 것이다.

• Proceedings of the KIEE Conference
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• 2007.04a
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• pp.292-294
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• 2007

Recently, for satisfying many application demands such as coding delay, computing power, transporting channel characteristic, etc, many profiles are supported in video coding standards. Therefore, in transcoding between same standards or between other standards, the functional difference of profiles supported by application occur many problems. In this paper, transcoding MPEG-2 main profile to H.264/AVC baseline profile which has restriction in the number of reference frame is focused. In this case, the bidirectional prediction supported in MPEG-2 main profile is not supported in H.264/AVC baseline profile. Also, in the restriction of reference frame, motion vectors in the MPEG-2 decoder as predictor should be adjusted. In this paper, the proposed algorithm is based on the characteristic of which motion. vector is uniform according to the distance from reference frame. The adaptive search techniques through the determination of the uniformity extremely reduce the computational complexity.

• Proceedings of the Korean Information Science Society Conference
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• 1998.10c
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• pp.234-236
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• 1998

본 논문은 GUI(Graphical User interface) 환경에서 MPGE-1 영상 편집을 위한 시스템 도구(Tool)를 기술한다. 기존에 출시된 제품은 일반적으로 AVI 나 MOV 포맷(format)을 사용하는데 비하여 본 논문에서는 MPGE-1을 압축 영역 상태에서 편집함으로써 영상의 품질과 저장의 효율성 및 처리속도에 많은 이점을 두었다. 편집 작업은 Random Access 의 기본 단위가 되는 GOP(Group of Picture) 단위의 경계 편집을 사용하여 영상 편집 기능인 Copy, Paste, Cut, Undo등을 기술하였다. 또한 효율적인 편집 환경을 위해 편집 윈도우 형태를 클립 청, 클립 정보 창, 편집 창, 재생 창, 미리 보기 창으로 구분하였다. 편집된 영상은 효율적 재생을 위하여 DirectDraw을 사용하였다. 본 논문에서 소개한 편집 시스템은 GUI 기반으로 사용자에게 익숙한 사용자 인터페이스 환경을 기술하였다.