• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2012.07a
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• pp.457-458
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• 2012

본 논문에서는 저비트율 환경에서 화면내 예측 모드 정보를 적응적으로 부호화하는 방법을 제안한다. 저비트율 환경에서의 예측 모드의 확률정보에 기반하여 특성을 분석한 후 기존의 방법과 제안된 방법을 적응적으로 선택하여 예측 모드 정보를 부호화 한다. 제안된 방법에서는 기존의 MPM을 대체하여 하나의 MB내에서 MPM과 일치하지 않는 블록에 대한 개수에 대한 정보, 해당 블록의 위치 정보, 실제 모드 정보를 부호화하는 방법을 사용하였다. 실험 결과를 통해서, 제안된 기술은 저비트율 환경에서 평균적으로 0.10dB의 BD-PSNR 증가 또는 1.72%의 BD-bitrate를 감소시킴으로써 H264/AVC의 효율을 향상시킴을 확인할 수 있다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2022.06a
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• pp.74-77
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• 2022

본 논문에서는 계층적 픽셀 예측과 컨텍스트 적응적 산술 부호화를 이용한 이미지 적응 무손실 압축 알고리즘을 제안한다. 입력 RGB 이미지는 먼저 가역적 색상 변환이 적용된다. Y 채널 이미지는 기존의 무손실 압축 인코더로 압축되고, U와 V채널 이미지는 Y 채널 이미지를 기반으로 예측된다. 원본과의 차이는 컨텍스트 적응적 산술 부호화를 통해 압축된다. 본 논문에서 제안된 알고리즘에서는 입력 이미지의 성질에 따라 산술 부호화에 사용되는 인코더의 개수를 적응적으로 변화시킨다. 또한 저주파 성분에 상대적으로 많은 자원을 집중시킴으로써 압축 성능을 향상시켰다. 제안된 방법은 기존에 사용되던 압축 방식들과 비교했을 때에도 의미 있는 성능을 보였다.

• Proceedings of the Korea Information Processing Society Conference
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• 2008.05a
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• pp.115-118
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• 2008

H.264/AVC는 동영상 데이터를 효율적으로 전송하기 위한 압축 기술로써 7가지 가변 블록에 대한 움직임 예측(Motion Estimation) 및 움직임 보상(Motion Compensation), DCT(Discrete Cosine Transform), 엔트로피 부호화(Entropy Coding), 디블록킹 필터 등 여러 가지 방법이 있다. 이러한 방법들로 인해 압축 효율은 높아졌으나 많은 계산량으로 인해 부호화 시간이 증가하게 되었다. 따라서 화질 손실을 최소한으로 줄이면서 소모되는 시간을 단축시키는 H.264 부호화 방법들이 개발되어야 한다. 그래서 본 논문에서는 H.264 부호화 과정 중 시간이 많이 소모되는 움직임 예측에서 움직임 벡터를 찾기 위한 방법을 제안한다.

• Journal of Broadcast Engineering
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• v.9 no.3
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• pp.225-235
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• 2004

In this paper, we propose a new stereoscopic video coding approach for heterogeneous consumer devices by exploiting the concept of spatio-temporal scalability. The proposed method uses MPEG-2 standard for coding the left or main sequence and an enhanced compatible coding scheme for predicting the P- and B-type of frames of the right or auxiliary sequence. The enhanced compatible coding scheme predicts matching block by interpolating both two forward and backward motion predicted macroblocks and disparity predicted macroblock. To provide flexible stereo video service, we define both a temporally scalable layer and a spatially scalable layer for each eye-view. The experimental results show the efficiency of proposed coding scheme by comparison with already known methods and the advantages of disparity estimation in terms of scalability overhead. According to the experimental results, we expect the proposed functionalities will play a key role in establishing highly flexible stereo video service for ubiquitous computing environment where devices and network connections are heterogeneous.

• Journal of the Korean Association of Geographic Information Studies
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• v.3 no.1
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• pp.1-11
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• 2000

The hybrid coding algorithm for multi-spectral image obtained from satellite is discussed. As the spatial and spectral resolution of satellite image are rapidly increasing, there are enormous amounts of data to be processed for computer processing and data transmission. Therefore an efficient coding algorithm is essential for multi-spectral image processing. In this paper, VQ(vector quantization), quadtree decomposition, and DCT(discrete cosine transform) are combined to compress the multi-spectral image. VQ is employed for predictive coding by using the fact that each band of multi-spectral image has the same spatial feature, and DCT is for the compression of residual image. Moreover, the image is decomposed into quadtree structure in order to allocate the data bit according to the information content within the image block to improve the coding efficiency. Computer simulation on Landsat TM image shows the validity of the proposed coding algorithm.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2016.06a
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• pp.209-210
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• 2016

날이 갈수록 빨라지는 IT분야의 발달로 최근 정보 통신망, 핸드폰, 컴퓨터 등의 발달과 함께 시간과 장소에 상관없이 빠르게 동영상 수요가 급증 하고 있다. 급증하고 있는 동영상 수요에 맞춰 고품질의 서비스를 제공하기 위해서는 압축 부호화 기술이 필수적이다. 이와 같은 흐름에 따라 표준화 기관인 ITU-T, ISO/IEC는 2013년 초, 최신 압축 부호화 기술인 HEVC를 제정하였다. HEVC에서는 이전 표준과 비교하여 다양한 부호화 기술이 포함되었는데 그 중 화면 내 예측 기술에서는 35가지 모드 중에서 최적의 모드를 결정하여 예측 블록을 더욱 정밀하게 생성한다. 이때, 색차 성분의 화면 내 예측 모드는 휘도 성분의 예측 모드와는 달리, 고정된 5개의 모드만 가지고 있다. 본 논문에서는 5개 모드의 번호를 통계적 특성을 이용하여 새롭게 모드 번호를 할당하는 실험을 수행하고 결과를 분석한 후, 향후 연구 방향을 제시한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.6C
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• pp.585-593
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• 2007

For the improvement of coding efficiency, the H.264 standard uses new coding tools such as VBS, 1/4-pel accurate ME, multiple references, intra prediction, loop filter, etc. Using these coding tools, H.264 has achieved significant improvements from rate-distortion point of view compared to existing standards. However, the encoder complexity is greatly increased due to these coding tools. We focus on the complexity reduction method of intra-mode decision. Our algorithm first restricts selective prediction modes of Intra4x4 using a simple preprocessing. The prediction modes of Intra4x4 are used for restricting those of the other inter-modes. Simulation results show that the proposed method outperforms other conventional methods and save about 82% of total encoding time.

• Journal of Broadcast Engineering
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• v.17 no.6
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• pp.976-989
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• 2012

In this paper, we propose an efficient motion prediction architecture and DPB design mechanism for scalable multi-view video coding which is implemented by integrating SVC and MVC coding algorithms. In the proposed motion prediction architecture, we employ pictures associated with other views as a candidate for reference picture for improved motion prediction performance. By the proposed prediction architecture, we could enormously reduce the size of compressed video data. When performing scalable multi-view video coding, an integrated DPB design mechanism is also proposed. It is shown by various simulations that the proposed motion prediction architecture for scalable multi-view video coding can result in reduced data size in the compressed bitstream.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.45 no.3
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• pp.160-174
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• 2008

In this paper, we propose new coding techniques for photometry data of three-dimensional(3-D) mesh models. We make a good use of geometry and connectivity information to improve coding efficiency of color, normal vector, and texture data. First of all, we determine the coding order of photometry data exploiting connectivity information. Then, we exploit the obtained geometry information of neighboring vortices through the previous process to predict the photometry data. For color coding, the predicted color of the current vertex is computed by a weighted sum of colors for adjacent vortices considering geometrical characteristics between the current vortex and the adjacent vortices at the geometry predictor. For normal vector coding, the normal vector of the current vertex is equal to one of the optimal plane produced by the optimal plane generator with distance equalizer owing to the property of an isosceles triangle. For texture coding, our proposed method removes discontinuity in the texture coordinates and reallocates texture image segments according to the coding order. Simulation results show that the proposed compression schemes provide improved performance over previous works for various 3-D mesh models.

• Journal of Broadcast Engineering
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• v.21 no.3
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• pp.319-329
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• 2016

Internet Video Coding (IVC) is a royalty-free codec currently being developed in MPEG. Coding efficiency of IVC codec has been steadily enhanced and it was reported that the performance of Committee Draft (CD) version is comparable to H.264/AVC High Profile (HP) in terms of objective and subjective qualities. In this paper, we present some coding tools that have been proposed for enhancing the coding efficiency of IVC during the developing process in MPEG along with brief overview of IVC codec architecture and coding algorithms. The coding tools include both of normative tools and informative tools such as non-reference P frame coding, DC mode intra prediction, Lagrange multiplier selection, and extension of chroma intra prediction modes. Improvement obtained by each tool is presented in terms of algorithm and coding gain based on the experiments. As a result of the experiment, the coding tools give the average bit saving of 8.8%, 0.4%, 0.4%, and 0.0%, respectively, in the low-delay coding mode.