• Journal of information and communication convergence engineering
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• 제7권4호
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• pp.501-506
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• 2009

In the H.264/ AVC video coding standard, the intra-prediction coding with various block sizes offers a considerably high improvement in coding efficiency compared to previous standards. In order to achieve this, H.264/AVC uses the Rate-distortion optimization (RDO) technique to select the best intraprediction mode for a macroblock, and it brings about the drastic increase of the computation complexity of H.264 encoder. To reduce the computation complexity and stabilize the coding performance on visual quality, this paper proposed a fast intra-prediction mode decision algorithm using non-parametric thresholds and simplified directional masks. The use of nonparametric thresholds makes the intra-coding performance not be dependent on types of video sequences and simplified directional masks reduces the compuation loads needed by the calculation of local edge information. Experiment results show that the proposed algorithm is able to reduce more than 55% of the whole encoding time with a negligible loss in PSNR and bitrates and provides the stable performance regardless types of video sequences.

• 디지털산업정보학회논문지
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• 제8권2호
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• pp.131-143
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• 2012

This paper introduces the double-density discrete wavelet transform using 3 direction separable processing method, which is a discrete wavelet transform that combines the double-density discrete wavelet transform and quincunx sampling method, each of which has its own characteristics and advantages. The double-density discrete wavelet transform is nearly shift-invariant. But there is room for improvement because not all of the wavelets are directional. That is, although the double-density DWT utilizes more wavelets, some lack a dominant spatial orientation, which prevents them from being able to isolate those directions. The dual-tree discrete wavelet transform has a more computationally efficient approach to shift invariance. Also, the dual-tree discrete wavelet transform gives much better directional selectivity when filtering multidimensional signals. But this transformation has more cost complexity Because it needs eight digital filters. Therefor, we need to hybrid transform which has the more directional selection and the lower cost complexity. A solution to this problem is a the double-density discrete wavelet transform using 3 direction separable processing method. The proposed wavelet transformation services good performance in image and video processing fields.

• 한국통신학회논문지
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• 제36권4C호
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• pp.217-225
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• 2011

본 논문에서는 영상의 지역 특성별로 보간 방법을 적응적으로 선택하여 적용하는 효과적인 디인터레이싱 알고리듬을 제안한다. 기존의 알고리듬들의 경우 각기 다른 방법으로 방향성을 구하기 때문에 영상의 지역 특성별로 성능이 다르게 나오는 경우가 있다. 또한, FDD(Fine Directional De-interlacing) 알고리듬의 경우 PSNR(Peak Signal-to-Noise Ratio)은 다른 알고리듬들에 비해 높게 나오지만 계산량이 많다는 단점이 있다. 이를 보안하기 위해 본 논문에서는 여러 영상들에서 계산량은 적으면서 화질 성능은 뛰어난 LA(Line Average), MELA(Modified Edge-based Line Average), LCID(Low-Complexity Interpolation Method for De-interlacing) 알고리듬들 중 지역복잡도 (DoLC, Degree of Local Complexity)별로 효과적인 알고리듬을 학습하여 이를 이용하여 보간을 수행하는 디인터레이싱 방법을 제안한다. 실험 결과 제안하는 방법은 좋은 성능에 비해 계산량이 적은 LCID 알고리듬과 비슷한 계산량을 보이면서 객관적 화질이 우수한 FDD, MELA 알고리듬보다 PSNR로 대표되는 객관적 화질과 주관적 화질 측면에서 우수한 결과를 나타내는 것을 알 수 있다.

• Journal of Communications and Networks
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• 제15권4호
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• pp.370-382
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• 2013

Distributed massive MIMO systems, which have high bandwidth efficiency and can accommodate a tremendous amount of traffic using algorithms such as zero-forcing beam forming (ZFBF), may be deployed in large public venues with the antennas mounted under-floor. In this case the channel gain matrix H can be modeled as a multi-banded matrix, in which off-diagonal entries decay both exponentially due to heavy human penetration loss and polynomially due to free space propagation loss. To enable practical implementation of such systems, we present a multi-banded matrix inversion algorithm that substantially reduces the complexity of ZFBF by keeping the most significant entries in H and the precoding matrix W. We introduce a parameter p to control the sparsity of H and W and thus achieve the tradeoff between the computational complexity and the system throughput. The proposed algorithm includes dense and sparse precoding versions, providing quadratic and linear complexity, respectively, relative to the number of antennas. We present analysis and numerical evaluations to show that the signal-to-interference ratio (SIR) increases linearly with p in dense precoding. In sparse precoding, we demonstrate the necessity of using directional antennas by both analysis and simulations. When the directional antenna gain increases, the resulting SIR increment in sparse precoding increases linearly with p, while the SIR of dense precoding is much less sensitive to changes in p.

• 한국콘텐츠학회논문지
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• 제9권3호
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• pp.20-27
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• 2009

다중 참조 영상을 이용한 최적 부호화 모드를 선택하기 위해 율-왜곡 최적화 기법을 적용한 H.264/AVC 동영상 압축 표준은 기존의 동영상 압축 표준들보다 높은 부호화 효율을 얻었지만 계산 복잡도가 그만큼 증가하게 되었다. 따라서 이런 계산의 복잡도를 줄이기 위한 많은 빠른 모드 결정 방법들이 제안되었다. 그중에 I4MB의 방향성 정보를 이용한 고속 인트라 모드 결정 알고리즘을 제안하였다. 제안한 알고리즘은 JM11.0과 비교하여 무시할만하게 PSNR이 손실되고 비트율의 증가하지만 IPPP 영상들에서 전체 부호화 시간을 평균 15%와 모든 영상을 인트라로 처리한 영상들에서 부호화 시간을 평균 44% 감소시킬 수 있었다.

• 방송공학회논문지
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• 제20권1호
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• pp.171-182
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• 2015

HEVC는 H.264/AVC에 비해 압축 성능을 크게 개선시킬 수 있지만 부호화기와 복호화기 모두 복잡도가 크게 증가한다. 본 논문에서는 HEVC의 화면 간 예측 모드 결정 과정을 분석하고, 이 결과로부터 부호화기 및 복호화기의 복잡도를 효과적으로 감소시키기 위한 방법을 제안하였다. 제안하는 방법은 단방향 예측 모드의 결과로부터 양방향 예측 모드를 수행하지 않아도 되는 조건을 찾고, 이 조건을 만족하는 경우 미리 종료시킴으로써 부호화 복잡도를 감소시킨다. 실험 결과 압축률 하락 폭이 각각 0.6%, 1.0%, 1.5%인 경우 부호화 복잡도를 12.0%, 14.2%, 17.2% 감소시킬 수 있었으며, 이 때, 양방향 예측 모드의 비율을 각각 6.3%, 11.8%, 16.6% 감소시킴으로써 복호화기의 복잡도도 함께 감소시킬 수 있었다. 마지막으로, 제안한 방법이 HEVC 참조 소프트웨어에 기 적용되어 있는 고속화 알고리즘과 함께 사용되는 경우에도 유사한 효과를 낼 수 있음을 검증하였다.

• 대한전자공학회논문지
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• 제24권6호
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• pp.1087-1094
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• 1987

In this paper, we describe about polygon resizing porblem where the given polygons are expanded or shrunk in two dimensional plane. First, the definition of polygon resizing and it's problems are given, then the enhanced XY method is proposed: the polygon resizing can be completed in one directional sweep of plane only, usisng enhanced plane sweep method. The time complexity is 0(n log n), and space complexity 0(\ulcorner), where n is the number of verties of polygons. The applications of polygon resizing to the mask artwork processing and layout verification are discussed.

• 디지털산업정보학회논문지
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• 제10권3호
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• pp.197-205
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• 2014

In applications of adaptive noise control or active noise control, the presence of a transfer function in the secondary path following the adaptive controller and the error path, been shown to generally degrade the performance of the Least Mean Square (LMS) algorithm. Thus, the convergence rate is lowered, the residual power is increased, and the algorithm can become unstable. In general, in order to solve these problems, the filtered-x LMS (FX-LMS) type algorithms can be used. But these algorithms have slow convergence speed and weakness in the environment that the secondary path and error path are varied. Therefore, I present the new algorithm called the "Bi-directional Filtered-x (BFX) LMS" algorithm with nearly equal computation complexity. Through experimental study, the proposed BFX-LMS algorithm has better convergence speed and better performance than the conventional FX-LMS algorithm, especially when the secondary path or error path is varied and the impulsive disturbance is flow in.

• 디지털산업정보학회논문지
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• 제10권4호
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• pp.133-142
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• 2014

The least mean square(LMS) algorithm has been popular owing to its simplicity, stability, and availability to implement. But it inherently has a problem of slow convergence speed, and the presence of a transfer function in the secondary path following the adaptive controller and the error path has been shown to generally degrade the stability and the performance of the LMS algorithm in applications of acoustical noise control. In general, in order to solve these problems, the filtered-x LMS (FX-LMS) type algorithms can be used and the bi-directional Filtered-x LMS(BFXLMS) algorithm is very attractive among them, which increase the convergence speed and the performance of the controller with nearly equivalent computation complexity. In this paper, a mathematical analysis for the BFXLMS algorithm is presented. In terms of view points of time domain, frequency domain, and stochastic domain, the characteristics and stabilities of algorithm is accurately analyzed.

• 한국통신학회논문지
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• 제30권3C호
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• pp.133-140
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• 2005

본 논문에서는 블록 기반의 영상압축에 있어서 방향성 기반 공간적 에러 은닉 기법을 제안한다. 제안된 기법은 우선 공간적 경계 정합 기법을 이용하여 손실된 블록 내의 에지 방향성을 나타내는 공간 방향 벡터들을 찾아낸다. 이 벡터들을 이용한 방향성 보간을 통해 복원 블록들을 만들고, 그 중 방향성 경계정합 에러가 작은 복원 블록들을 이용하여 최종 복원 영상을 생성한다. 제안된 기법은 매크로블록이나 슬라이스 단위의 에러에 대해 적응적으로 대처할 수 있고, 복잡도가 낮을 뿐만 아니라 우수한 복원 화질을 얻게 해준다.