조남익 교수

An algorithm for the fast computation of a 2-D discrete cosine transform (DCT) is presented. It is shown that the N*N DCT, where N=2/sup m/, can be computed using only N 1-D DCTs and additions, instead of using 2N 1-D DCTs as in the conventional row-column approach. Hence the total number of multiplications for the proposed algorithm is only half of that required for the row-column approach and is also less than that of most of other fast algorithms, whereas the number of additions is almost com

A lattice notch filter for the detection and enchancement of sinusoids in noise is presented, and the convergence properties of the algorithm are investigated using ODE (ordinary differential equation) analysis. It is shown that the frequency estimate of the algorithm for a single sinusoid is unbiased, regardless of the pole-zero contraction factor and the noise variance. An expression for the MSE (mean square error) of the frequency estimate and the output SNR of the algorithm is derived. Simul

Two simple methods for retrieving a single sinusoid corrupted with noise are proposed. They are based on the lattice form realization of an adaptive infinite-impulse-response (IIR) notch filter. The IIR filter is a cascade of second-order all-pole and all-zero filters, and the coefficients of the finite-impulse-response (FIR) section are adapted. The proposed algorithms keep the poles of the filter inside the unit circle. The computer simulation results show that the algorithms have considerable

Two algorithms are presented for computing the discrete cosine transform (DCT) on existing VLSI structures. First, it is shown that the N-point DCT can be implemented on the existing systolic architecture for the N-point discrete Fourier transform (DFT) by introducing some modifications. Second, a new prime factor DCT algorithm is presented for the class of DCTs of length N=N/sub 1/*N/sub 2/, where N/sub 1/ and N/sub 2/ are relatively prime and odd numbers. It is shown that the proposed algorith

The authors present an efficient algorithm for the computation of the 4*4 discrete cosine transform (DCT). The algorithm is based on the decomposition of the 4*4 DCT into four 4-point 1-D DCTs. Thus, only 1-D transformations and some additions are required. It is shown that the proposed algorithm requires only 16 multiplications, which is half the number needed for the conventional row-column method. Since the 2/sup m/*2/sup m/ DCT can be computed using the 4*4 DCT recursively for any m, the pro

This paper introduces the concept of warped discrete cosine transform (WDCT) and an image compression algorithm based on the WDCT. The proposed WDCT is a cascade connection of a conventional DCT and all-pass filters whose parameters can be adjusted to provide frequency warping. Because only the first-order all-pass filters are considered, the WDCT can be implemented by a Laguerre network connected with the DCT. For the more efficient software implementation, we propose truncated and approximated

N. I. Cho and S. U. Lee (1991) proposed a fast algorithm for 2-D N*N DCT, where N=2/sup m/. It requires only half the number of multiplications of the conventional row-column approach. However, the signal flow graph for the postaddition stage seems very complicated and the order of the output index is seemingly irregular, because the postaddition stage was not based on the mathematical expressions. Consequently, derivation of the signal flow graph becomes complicated as the transform size increa

In this paper, tracking properties of the adaptive lattice notch filter (ALNF) for input sinusoids with linearly and randomly varying frequencies are investigated. Expressions for the asymptotic tracking error and the mean square error (MSE) of the frequency estimate are derived. The expressions show that the forgetting factor, or the step-size constant of the algorithm, plays an important role in controlling the tracking error, the MSE of the frequency estimate, and the output SNR. It is shown

An algorithm for the design of optimal one-dimensional (1-D) and two-dimensional (2-D) FIR filters over a discrete coefficient space is proposed. The algorithm is based on the observation that the equiripple frequencies of a subproblem (SP) in the branch and bound (BaB) algorithm are closely related to those of neighboring SPs. By using the relationship among the SPs, the proposed algorithm reduces the number of constraints required for solving each SP. Thus, the overall computational load for t

Recently, a novel fast algorithm for 2-D N*N DCT (discrete cosine transform), where N=2/sup m/, was proposed. Only half the number of multiplications required for the conventional row-column approach are needed. However, the relationship between the input-output indices for the postaddition stage in the algorithm is seemingly very irregular. In the present work, the authors derive general and systematic expressions for the relation of the postaddition stage in the 2-D DCT algorithm by representi

This paper proposes an adaptive algorithm for the quantization step size control of MPEG-2, using the information obtained from the previously encoded picture. Before quantizing the DCT coefficients, the properties of reconstruction error of each macro block (ME) is predicted from the previous frame. For the prediction of the error of current MB, a block with the size of ME in the previous frame are chosen by use of the motion vector. Since the original and reconstructed images of the previous f

This paper proposes an algorithm for the reduction of blocking artifacts in the transform coded images and videos. The algorithm is based on the filtering of block boundaries. However, the proposed technique is not the actual filtering in the sense that no multiplication of the pixel values with the filter coefficients is required. Instead of filtering the pixel values through the filter coefficients, the output of the filter is modeled as a typical step response function of the lowpass filter o