• Journal of information and communication convergence engineering
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• 제7권2호
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• pp.193-198
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• 2009

The H.264/ AVC video coding standard supports the intra prediction with various block sizes for luma component and a 8x8 block size for chroma components. This new feature of H.264/AVC offers a considerably higher improvement in coding efficiency compared to previous compression standards. In order to achieve this, H.264/AVC uses the Rate-distortion optimization (RDO) technique to select the best intra prediction mode for each block size, and it brings about the drastic increase of the computation complexity of H.264 encoder. In this paper, a fast block size decision algorithm is proposed to reduce the computation complexity of the intra prediction in H.264/AVC. The proposed algorithm computes the smoothness based on AC and DC coefficient energy for macroblocks and compares with the nonparametric criteria which is determined by considering information on neighbor blocks already reconstructed, so that deciding the best probable block size for the intra prediction. Also, the use of non-parametric criteria makes the performance of intra-coding not be dependent on types of video sequences. The experimental results show that the proposed algorithm is able to reduce up to 30% of the whole encoding time with a negligible loss in PSNR and bitrates and provides the stable performance regardless types of video sequences.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 2009년도 IWAIT
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• pp.142-147
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• 2009

The recent H.264/AVC video coding standard provides a higher coding efficiency than previous standards. H.264/AVC achieves a bit rate saving of more than 50 % with many new technologies, but it is computationally complex. Most of fast mode decision algorithms have focused on Baseline profile of H.264/AVC. In this paper, a fast block mode decision scheme for P- slices in High profile is proposed to reduce the computational complexity for H.264/AVC because the High profile is useful for broadcasting and storage applications. To reduce the block mode decision complexity in P- pictures of High profile, we use the SAD value after $16{\times}16$ block motion estimation. This SAD value is used for the classification feature to divide all block modes into some proper candidate block modes. The proposed algorithm shows average speed-up factors of 47.42 ${\sim}$ 67.04% for IPPP sequences.

• 전자공학회논문지CI
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• 제46권6호
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• pp.27-34
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• 2009

BTC (Block Truncation Coding)은 이미지 압축 기법의 일종으로서 간단하고 효과적이다. 그러나, 이 방법은 블록 크기를 크게 사용할 때 블록 효과가 증가하므로 이미지의 질이 좋지 않다. ODBTC(Ordered Dithering Block Truncation Coding)는 BTC와 같은 압축 능력을 유지하면서 블록 효과를 해결한 방법이다. 본 논문에서는 이와 같은 압축된 이미지를 이용하여 데이터를 하프톤 이미지에 저장하는 방법을 제안하고자 한다. EMD 방법은 Zhang과Wang[6]이 그레이스케일 이미지에 데이터를 은닉하도록 하도록 고안된 방법이다. 그런 이유로, 비트맵 이미지에는 적합하지 않다. 본 논문에서는 EMD가 어떻게 비트맵 이미지에 적용될 수 있는지를 제안한다. 또한, 본 논문의 실험에서, 우리가 제안한 방법이 하프톤 이미지에 효과적임을 증명한다.

• 한국항행학회논문지
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• 제12권2호
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• pp.115-121
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• 2008

본 논문에서는 DS-CDMA 시스템 구현 시 복잡성을 감소시키는 다중접속간섭 등의 여러 감쇠 요인을 고려하여 이를 개선시킬 수 있는 FS MC-CDMA 시스템의 성능을 분석하고 열악한 무선 모바일 환경에서 성능 개선기법인 BCH 부호화기법을 채용하여 FS MC-CDMA 시스템의 성능을 개선하였다. 또한 차세대 무선 모바일 통신 채널 환경으로는 나카가미 페이딩을 적용하여 FS MC-CDMA 시스템의 성능을 분석하여 검토하였다.

• ETRI Journal
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• 제31권5호
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• pp.607-609
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• 2009

In this letter, an effective scanning method based on a morphological representation of quantized coefficients is proposed for intra coding in H.264. In the proposed scanning method, the scan order for each block is adaptively reconfigured by exploiting a residual correlation beyond the border of the block. An initial scan order for the current block is determined first by using the pattern of nonzero coefficients in the adjacent block. Then, a complete scan order is obtained by performing the dilation operation at each position within the initial scan order. Experimental results show that the proposed method improves the coding efficiency up to 3.7% compared to the conventional zigzag scanning method.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2008년도 하계종합학술대회
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• pp.73-74
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• 2008

In this paper, we suggest a new video coding method using hierarchical block mode structure extension. It is based on the conventional H.264 block modes but adds hierarchically extended block modes to cover large resolution sequences. It is shown by experimental results that the proposed method can achieve a higher coding gain for HD sequences.

• 디지털콘텐츠학회 논문지
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• 제5권1호
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• pp.48-53
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• 2004

블록 기반 DCT 코딩 이미지는 NxN 블록 단위로 코딩을 하기 때문에 블록화 현상이 발생하게 된다. 특히 저비트율 이미지에서는 이러한 현상이 더욱 두드러지게 나타난다. 본 논문에서는 이러한 이미지에서 인근 픽셀 정보를 이용하여 블록화 현상을 줄이는 방법을 제안한다. 제안된 기법은 이미지 재구성 기법과 결합하는 경우에도 화질을 개선하는데 사용될 수 있다. 제안된 기법의 성능은 실험을 통해 보인다.

• 한국통신학회논문지
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• 제21권5호
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• pp.1089-1095
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• 1996

가변블록 변환부호화는 변환부호화에 적용되는 블럭의 크기를 다르게 하여 코딩의 효율을 좋게 한다. 변환블록의 크기는 블럭의 활성도에 따라 적응된다. 즉, 블럭의 활성도가 크면 블럭의 크기는 작아지고, 반대로 활성도가 작으면 블럭의 크기가 커진다. 본 논문에서는 블럭의 활성도로서 분산값 대신에 변환계수의 고주파 에너지를 이용하였다. 컴퓨터 시뮬레이션 결과, 제안한 방법이 분산값을 이용한 방법보다는 약 1~5dB, MAD를 이용한 방법보다는 약 0.5~3dB정도의 성능개선을 보여주었다.

• 산업기술연구
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• 제15권
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• pp.93-101
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• 1995

Fractal coding is a promising method for image compression, but it has not lived up to its promise as low bit-rate image compression scheme. The existing algorithms for finding self-mapping contractive transforms are computationally expensive and offer a poor rate-quality tradeoff. In this paper, we propose a segment based fractal coding. We classify the range blocks into shade, midrange or edge blocks, and segment edge block along the edge. And we apply midrange coding scheme for each segment. Our experiments show that our method gives better rate-qualty trade of than current fractal block coding methods.

• 한국통신학회논문지
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• 제22권3호
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• pp.469-480
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• 1997

For moving image coding, the variable size of region coding based on local motion is more efficient than fixed size of region coding. It can be applied well to complex motions and is more stable for wide motions because images are segmented according to local motions. In this paper, new image coding method using the segmentation of motion vectors is proposed. First, motion vector field is smoothed by filtering and segmented by smoothed motion vectors. The region growing method is used for decomposition of regions, and merging of regions is decided by motion vector and prediction errors of the region. Edge of regions is excluded because of the correlation of image, and neighbor motion vectors are used evaluation of current block and construction of region. The results of computer simulation show the proposed method is superior than the existing methods in aspect of coding efficiency.