• Journal of IKEEE
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• v.23 no.3
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• pp.800-804
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• 2019

This paper presents a dual-loop sub-sampling digital PLL for a 2.4 GHz IoT applications. The PLL initially performs a divider-based coarse lock and switches to a divider-less fine sub-sampling lock. It achieves a low in-band phase noise performance by enabling the use of a high resolution time-to-digital converter (TDC) and a digital-to-time converter (DTC) in a selected timing range. To remove the difference between the phase offsets of the coarse and fine loops, a phase offset calibration scheme is proposed. The phase offset of the fine loop is estimated during the coarse lock and reflected in the coarse lock process, resulting in a smooth transition to the fine lock with a stable fast settling. The proposed digital PLL is designed by SystemVerilog modeling and Verilog-HDL and fully verified with simulations.

• Journal of the Institute of Convergence Signal Processing
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• v.6 no.3
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• pp.107-111
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• 2005

With the increasing use of multimedia technologies, image compression requires higher performance as well as new functionality in the informationized society. Specially, in the specific area of still image encoding in embedded system, a new standard, JPEG2000 that improve various problem of JPEG was developed. This paper proposed a method that reduce quantity of data delivered in EBCOT(Embedded Block Coding with Optimized Truncation) process using SPIHT(Set Partitioning in Hierarchical Trees) Algorithm to optimize selection of threshold from feature of wavelet transform coefficients and to remove sign bit in LL area for the increment of compression efficiency on JPEG2000. The experimental results showed the proposed algorithm achieves more improved bit rate in embedded system.

• Proceedings of the Korea Society for Industrial Systems Conference
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• 2001.05a
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• pp.288-299
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• 2001

In transcoding, simply reusing the motion vectors extracted from an incoming video bit stream may not result in the best quality because the incoming motion vectors become non-optimal due to the reconstruction errors. To achieve the best video quality possible, a new motion estimation should be performed in the transcoder. An adaptive motion vector refinement is proposed that refines the base motion vector according to the activity of macroblock using intermediate data extracted from an incoming video bit stream. Experimental results shows that the proposed method can improve the video quality to the level achieved by using the full-scale motion estimation with minimal computational complexity.

• Journal of the Korean Institute of Telematics and Electronics
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• v.20 no.4
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• pp.55-60
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• 1983

A new type of digital phase-locked loop (DPLL) that employs a multilevel quantified timing error detector (TED) is proposed and analyzed under the assumption of negligible quantizing effect and no noise. Since the timing error is quantized uniformly, the TED has a linear characteristic. From the linear characteristic of TED, a first order difference equation describing the behavior of the loop is derived. Using the system equation, the loop is analyzed mathematically for phase step and frequency step input. Desired locking condition for the loop to be locked and the lock range for the DPLL's to achieve exact locking independently of initial conditions are ob-tained. And these analyses are confirmed by timing error plane plots and computer simulation.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2020.11a
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• pp.143-144
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• 2020

VVC (Versatile Video Coding)는 HEVC이후 차세대 표준 비디오 코딩으로 JVET(Joint Video Exploration)에 의해 2018년 표준화를 시작하였다. VVC에는 복원픽쳐의 변환-양자화에러에 의해 발생한 블로어, 블로킹, 링잉 아티팩트를 감소시키기 위하여 deblocking filter (DF), sample adaptive offset (SAO), adaptive loop filter(ALF)와 같은 모듈을 사용한다. 한편 CNN (Convolutional Neural Network)은 최근 이미지와 비디오 복원에 높은 성능을 보이고 있다. VVC에서 픽쳐는 CTU (Coding Tree Unit)으로 분할되고 각 CTU는 다시 CU (Coding Unit)으로 분할된다. 그리고 인코딩을 위한 중요한 정보들이 Picture, CTU, CU단위로 디코더에 전송된다. 이 논문에서는 화면 간 예측으로 인코딩 된 픽처에서 블록과 픽처정보를 이용한 딥러닝 기반의 인루프 필터 모델을 제안한다. 제안하는 모델은 화면 간 예측에서 QP, 4×4 블록단위의 모션벡터, 참조블록과의 시간적거리, CU의 깊이를 모델에 추가적인 정보로 이용한다.

• The Journal of the Acoustical Society of Korea
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• v.24 no.7
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• pp.410-415
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• 2005

Recently, most of the speaker verification systems are based on the pattern recognition approach method. And performance of the pattern-classifier depends on how to classify a variety of speakers' feature parameters. In order to classify feature parameters efficiently and effectively, it is of great importance to enlarge variations between speakers and effectively measure distances between feature parameters. Therefore, this paper would suggest the positively mixed model scheme that can enlarge inter-speaker variation by searching the individual model with world model at the same time. During decision procedure, we can maximize inter-speaker variation by using the proposed mixed model scheme. We also make use of a symbol probability weighting function in this system so as to reduce vector quantization errors by measuring symbol probability derived from the distance rate of between the world codebook and individual codebook. As the result of our experiment using this method, we could halve the Detection Cost Function (DCF) of the system from $2.37\%\;to\;1.16\%$.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.39 no.6
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• pp.59-68
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• 2002

In this paper, we design the two-dimensional Discrete Wavelet Transform (2D DWT) filter that is widely used in various applications such as image compression because it has no blocking effects and relatively high compression rate. The filter that we used here is two-channel four-taps QMF(Quadrature Mirror Filter) Lattice filter with PR (Perfect Reconstruction) property. The proposed DWT architecture, with two consecutive inputs shows an efficient performance with a minimum of such hardware resources as multipliers, adders, and registers due to a simple scheduling. The proposed architecture was verified by the RTL simulation, and utilizes the hardware 100%. Our architecture shows a relatively high performance with a minimum hardware when compared with other approaches. An efficient memory mapping and address generation techniques are introduced and the fixed-point arithmetic analysis for minimizing the PSNR degradation due to quantization is discussed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.8
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• pp.1814-1822
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• 1997

In this paper, we present a new digital signature for copyright protection of digital images. The proposed algorithm is designed to be more robust to both the compression (quantization) errors and the illegal signature attack by a third party. More specifically, to maximize the watermaking effect, we embed the watermark by randomly adding or subtracking a fixed number instead of executing the XORs. Also, to improve the reliability of the watermark detection, we extact the watermark only on some image blocks, which are less sensitive to the compression error. Futhermore, the unrecovered compression errors are further detected by the Hypothesis testing. The illegal signalture attack of a third party is also protected by using some probabilistic decisions of the MSE between the orignal image and the signed image. Experimental results show that the peroposed algorithm is more robust to the quantization errors and illegal signature attack by a third party.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.8
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• pp.1677-1690
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• 1997

Block-transform coding is one of the most popular approaches for image compression. For example, DCT is widely used in the internaltional standards standards such as MPEG-1, MPEG-2, JPEG, and H.261. In the block-based transform coding, blocking artifacts may appear along block boundaries, and they can cause severe image degradation eqpecially when the transform coefficients are coarsely quantized. In this paper, we propose a new method for blocking artifacts reduction in transform-coded images. For blocking artifacts reduction, we add a correction term, on a block basis, composed of a linear combination of 28 basis images that are orthonormal on block boundaries. We select 28 DCT kernel functions of which boundary values are linearly independent, and Gram-Schmidt process is applied to the boundary values in order to obtain 28 boundary-orthonormal basis images. A threshold of bolock discontinuity is introduced for improvement of visual quality by reducing image blurring. We also investigate the number of basis images needed for efficient blocking artifacts reduction when the compression ratio changes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.8
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• pp.1790-1802
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• 1997

A wavelet transform coding method that fulfills the requirements of HD-VCR(high definition video casstte recorder) for studio applications in proposed. A constant bit rate is achieved by a forward rate control technique whcih determins the quantizer stepsize based on the coding results fo the previous frame. We also propose a two-level coder that consists of both the IDC(independently decodable code) and the DDC(dependently decodable code). To minimize error propagation, the transformed coefficients are restructured into transform blocks which are represented by a tree structure. The result shows thta the proposed coding scheme produces better picture quality with block effects than that of DCT(discrete cosine transform) based coding schemes at the same compression ratio. The proposed method meets most of the requirements of HD-VCR.