• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.1C
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• pp.56-62
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• 2009

In H.264/AVC, rate distortion optimization algorithm is used to decide the best block mode from various block modes. It improves a bit rate but greatly increases an amount of computation. This paper proposes a fast rate distortion optimization algorithm that omits a rate distortion optimization adaptively by predicting its cost from the cost calculated for motion estimation. The simulation results show that the proposed algorithm, on average, keeps nearly the image quality and the bit rate made by the rate distortion optimization while reduces 69.86% and 69.63% of computation added by it in CIF and QCIF respectively.

• International journal of steel structures
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• v.18 no.4
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• pp.1139-1152
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• 2018

Many studies on the application of stainless steels as structural materials in buildings and infra-structures have been performed thanks to superior characteristics of corrosion resistance, fire resistance and aesthetic appeal. Experimental investigation to estimate the ultimate strength and fracture mode of the fillet-welded connections of cold-formed austenitic stainless steel (STS304L) with better intergranular corrosion resistance than that of austenitic stainless steel, STS304 commonly used has carried out by authors. Specimens were fabricated to fail by base metal fracture not weld metal fracture with main variables of weld lengths according to loading direction. All specimens showed a block shear fracture mode. In this paper, finite element analysis model was developed to predict the ultimate behaviors of welded connection and its validity was verified through the comparison with test results. Since the block shear behavior of welded connection due to stress triaxiality and shear-lag effects is different from that of bolted connection, stress and strain distributions in the critical path of tensile and shear fracture section were investigated. Test and analysis strengths were compared with those by current design specifications such as AISC, EC3 and existing researcher's proposed equations. In addition, through parametric analysis with extended variables, the conditions of end distance and longitudinal weld length for block shear fracture and tensile fracture were suggested.

• Journal of information and communication convergence engineering
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• v.7 no.2
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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.

• Journal of Korea Multimedia Society
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• v.22 no.12
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• pp.1368-1375
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• 2019

In this paper, an prediction method is proposed for coding of depth pictures using spherical modeling. An spherical surface which has the least error from original depth values is modeled in a block. Pixels in the block are predicted through the parameters of the modeled spherical surface. Simulation results show that average prediction errors and entropy powers are improved to 30% and 200% comparing to the intra prediction of H.264/AVC, selection ratios of the proposed spherical modeling mode is more than 25%.

• JSTS:Journal of Semiconductor Technology and Science
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• v.12 no.1
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• pp.24-33
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• 2012

This paper describes a multi-mode LDPC decoder which supports 19 block lengths and 6 code rates of Quasi-Cyclic LDPC code for Mobile WiMAX system. To achieve an efficient implementation of 114 operation modes, some design optimizations are considered including block-serial layered decoding scheme, a memory reduction technique based on the min-sum decoding algorithm and a novel method for generating the cyclic shift values of parity check matrix. From fixed-point simulations, decoding performance and optimal hardware parameters are analyzed. The designed LDPC decoder is verified by FPGA implementation, and synthesized with a $0.18-{\mu}m$ CMOS cell library. It has 380,000 gates and 52,992 bits RAM, and the estimated throughput is about 164 ~ 222 Mbps at 56 MHz@1.8 V.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.949-950
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• 2008

The intra prediction technique is the one of the key factors to the success of H.264. There are nine optional prediction modes for each $4{\times}4$ luma block and 4 modes for each $16{\times}16$ luma block. To reduce the intra mode bits efficiently, the most probable mode (MPM) is estimated by using the intra modes of the adjacent blocks, since intra modes for neighboring $4{\times}4$ luma blocks are correlated. In this paper, a new method for estimating the MPM is proposed by using the statistical distribution of intra modes of adjacent intra blocks. Experimental results show that the proposed method can achieve a coding gain of about 0.1dB.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.807-808
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• 2008

In H.264, sub-pel motion estimation (ME) has strong effect when coding video sequences. 1/4-pel performs better at low bitrate while 1/8-pel gives better results at high bitrate. In this paper, a variable sub-pixel motion vector resolution based on block mode motion estimation method is proposed. Experiment results show that the proposed method can take the advantage of 1/4-pel at low bitrate and 1/8-pel at high bitrate. In addition to that, time is reduced from 14% to 53% compared to KTA1.3 with 1/8-pel motion vector (MV) resolution.

• Journal of the Korean Institute of Telematics and Electronics
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• v.24 no.5
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• pp.833-840
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• 1987

A new Block Truncation Coding(BTC) technique reducing the bit-plane and using differential pulse code modulation (DPCM) is proposed and compared with the conventional BTC methods. A new technique decides whether the subblock can be approximated to be uniform or not. If the subblock can be approximated to be uniform(merge mode), we transmit only the gray-level informantion. It not (split mode), we transmity both the bit-plane and the gray-level information. DPCM method is proposed to the encoding of gray-level information when the subblock can be approximated to be uniform. Also modified quantization method is presented to the encoding of gray-level information when the subblock is not uniform. This technique shows the results of coding 256 level images at the average data rate of about 0.75 bits/pel.

• ETRI Journal
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• v.37 no.6
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• pp.1176-1187
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• 2015

This work proposes a highly efficient sensorless motor driver chip for various permanent-magnet synchronous motors (PMSMs) in a wide power range. The motor driver chip is composed of two important parts. The digital part is a sensorless controller consisting mainly of an angle estimation block and a speed control block. The analog part consists of a gate driver, which is able to sense the phase current of a motor. The sensorless algorithms adapted in this paper include a sliding mode observer (SMO) method that has high robust characteristics regarding parameter variations of PMSMs. Fabricated SMO chips detect back electromotive force signals. Furthermore, motor current-sensing blocks are included with a 10-bit successive approximation analog-to-digital converter and various gain current amplifiers for proper sensorless operations. Through a fabricated SMO chip, we were able to demonstrate rated powers of 32 W, 200 W, and 1,500 W.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.30B no.12
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• pp.73-86
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• 1993

This paper proposes an automatic variable block truncation coding (BTC) method. It selects the block size automatically based on the mode of the discontinutiy measure of blocks. The combination of an automatic block-size determination scheme and the conventional BTC results in the proposed automatic variable BTC techniques. For color images, subsampling in I and Q chrominance components is adopted along with the variable BTC. To show the effectiveness of the proposed algorithm, its simulation results are compared to those of the several conventional BTC algorithms for monochrome and color test images. Computer simulation shows that the proposed algorithm gives better performance than the conventional ones based on the subjective and objective performance evaluation.