• Journal of the Semiconductor & Display Technology
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• v.12 no.1
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• pp.35-39
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• 2013

H.264/AVC is an authoritative international video coding standard which shows code and efficiency more improved than the existing video standards. Above all, the parameter block mode of H.264/AVC significantly contributes much to high compression efficiency. However, as the occasion demands, users tend to pass while overlooking the part that can produce a little higher compression efficiency. We, taking notice of this point, are designed to bring in much higher compression efficiency by gathering up the overlooked parts. This paper suggests the algorithm that produces efficient performance improvement by using the histogram of luminance in the pixel unit (Macroblock) of respective prediction block and applying specific thresholds. The experimental results proves that the technique proposed by this paper increases the compression efficiency of the existing H.264/AVC algorithm by 0.4% without any increase in the whole encoding time and PSNR complexity.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2020.07a
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• pp.249-250
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• 2020

본 논문에서는 VVC 화면간 예측 모드 Combined Inter-intra Prediction(CIIP)의 화면내 예측 과정에서의 향상된 PLANAR 예측 방법을 제안한다. Combined Inter-intra Prediction(CIIP) 모드는 화면간 예측 신호와 PLANAR 모드로 생성되는 화면내 예측 신호를 가중합 하여 최종 예측 신호를 생성하는 모드이다. 제안하는 방법은 화면간 예측 신호로 생성된 예측 샘플을 PLANAR 모드 예측 과정에서 우측 및 하단의 참조 샘플로 사용한다. 이후 PLANAR 예측 및 가중합 하여 예측 신호를 만들어내는 것은 기존 CIIP와 동일하다. 제안하는 방법의 성능 평가를 위하여 VVC의 참조 소프트웨어인 VTM 9.0에 구현하였으며, 기존 VTM 9.0과 부호화 성능을 비교한 결과로 휘도 성분에서 0.01 % 부호화 성능 감소를 보이고 색차 성분에 대하여 각각 0.17%, 0.13% 부호화 성능 향상을 보인다.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.791-792
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• 2008

We present a new algorithm for VLC table prediction in H.264 context-based adaptive variable length coding (CAVLC). Using both the correlation of coding modes and the statistics of the mode distribution in intra and inter frames, we can predict an appropriate VLC table of the given $4{\times}4$ block. Experimental results demonstrate that the proposed algorithm reduces the bit rate about 0.97% on average, compared to the H.264/AVC standard.

• Proceedings of the Optical Society of Korea Conference
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• 2003.07a
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• pp.204-205
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• 2003

We demonstrate a novel OFDR system with compactness and short measurement time based on the use of a wavelength-swept mode-locked fiber laser. The optical source uses an intra-cavity tunable Fabry-Perot filter as a tuning element. The fiber laser sweeps 20 nm in less than 10 ms. Spatial resolution of 100 fm and total measurement range of several centimeters are demonstrate

• Journal of the Optical Society of Korea
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• v.17 no.2
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• pp.117-129
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• 2013

We briefly review the recent progress in passively mode-locked fiber lasers (PMLFLs) based on semiconductor saturable absorber mirrors (SESAMs) and discuss the detailed characterization of a SESAM-based, passively mode-locked erbium-doped fiber (EDF) laser operating in the 1.5-${\mu}m$ spectral range for various configurations. A simple and compact design of the laser cavity enables the PMLFL to generate either femtosecond or wavelength-tunable picosecond pulses with high stability as the intra-cavity filtering method is altered. All the cavities investigated in our experiments present self-starting, continuous-wave mode-locking with no Q-switching instabilities. The excellent stability of the source eventually enables the wavelength-tunable PMLFL to be used as a master oscillator for a power-amplifier source based on a large-core EDF, generating picosecond pulses of >10-kW peak power and >100-nJ pulse energy.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.3
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• pp.1093-1104
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• 2014

The High Efficiency Video Coding (HEVC) is a new video coding standard that can provide much better compression efficiency than its predecessor H.264/AVC. However, it is computationally more intensive due to the use of flexible quadtree coding unit structure and more choices of prediction modes. In this paper, a fast intraframe coding scheme is proposed for HEVC. Firstly, a fast bottom-up pruning algorithm is designed to skip the mode decision process or reduce the candidate modes at larger block size coding unit. Then, a low complexity rough mode decision process is adopted to choose a small candidate set, followed by early DC and Planar mode decision and mode filtering to further reduce the number of candidate modes. The proposed method is evaluated by the HEVC reference software HM8.2. Averaging over 5 classes of HEVC test sequences, 41.39% encoding time saving is achieved with only 0.77% bitrate increase.

• Journal of the Optical Society of Korea
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• v.15 no.1
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• pp.56-60
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• 2011

We demonstrate passive mode-locking of a Cr:forsterite laser with a single-walled carbon nanotube saturable absorber mirror (SWCNT-SAM). Without compensation of intra-cavity dispersion, the self-mode-locked laser generates 11.7 ps pulses at a repetition rate of 86 MHz. The dispersion-compensated laser yields ultrashort pulses as short as 80 fs near $1.25\;{\mu}m$ at 78 MHz with average output powers up to 295 mW, representing the highest power ever reported for mode-locked solid-state lasers based on saturable absorption of SWCNTs in this spectral region.

• Journal of Information Processing Systems
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• v.18 no.2
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• pp.235-244
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• 2022

Many new techniques have been adopted in HEVC (High efficiency video coding) standard, such as quadtree-structured coding unit (CU), prediction unit (PU) partition, 35 intra-mode, and so on. To reduce computational complexity, the paper proposes two optimization algorithms which include fast CU depth range decision and fast PU partition mode decision. Firstly, depth range of CU is predicted according to spatial-temporal correlation. Secondly, we utilize the depth difference between the current CU and CU corresponding to the same position of adjacent frame for PU mode range selection. The number of traversal candidate modes is reduced. The experiment result shows the proposed algorithm obtains a lot of time reducing, and the loss of coding efficiency is inappreciable.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.39 no.6
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• pp.591-601
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• 2002

Motion compensation is a powerful method to compress an image sequence. Its main drawback is that once an error is occurred, the error propagates through the frames. Recently, the intra update method was proposed to stop the error propagation at the expense of reduction in compression efficiency. This paper proposes an intra update method based on a rate-distortion optimization in error prone environments. The rate and the distortion are estimated using the Lagrangian optimization to select the coding mode and the quantization step size. The proposed method is applied to MPEG-4 codec, and the experimental results show that it is robust to the error such as packet losses comparing with the conventional ones.

• The Journal of the Acoustical Society of Korea
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• v.22 no.4
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• pp.329-336
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• 2003

Intra-Vascular Ultra-Sound (IVUS) transducers were developed for the application to diagnose coronary diseases. The transducer consists of 32 piezoelectric elements with a front insulation layer and a polymeric acoustic backing layer on a hollow alumina tube. The optimal geometrical structure of the transducer was designed through theoretical analysis of radiation patterns of the transducer. Samples of the IVUS transducers of the diameter of 3㎜ were fabricated to illustrate the design scheme. For the piezoelectric elements, 2-2 mode piezocomposite materials were employed. Experimental performance of the transducers showed good agreement with the design results, which verified feasibility of the transducer for IVUS applications.