Hoon Yoo

Direction-oriented interpolation and its application to de-interlacing

A new direction-oriented interpolation method is proposed and then applied to de-interlacing. The proposed method introduces the upper spatial direction vector. (USDV) and the lower spatial direction vector (LSDV) to obtain more accurate direction of the highest spatial correlation. Using the USDV and the LSDV, the proposed method reduces possibility of wrong decision for the highest-correlated spatial direction. Line-based directional interpolation is performed after the direction vector is found. Extensive simulations conducted for images and video sequences show the efficacy of the proposed method over the previous methods based on the ELA and over the line averaging method in terms of the objective and subjective image quality.

A unified framework for wavelet transforms based on the lifting scheme

In the context of image coding, a number of reversible integer-to-integer wavelet transforms were previously proposed and compared with respect to their lossy compression performance, lossless compression performance, and computational complexity. Among the transforms, some of them were found to perform particularly well. In this paper, we propose a unified framework for several efficient transforms using the lifting scheme. We represent the transforms with simple parameters. The parameters are usually dependent on the input signal. We give mathematical formulations on the framework and experimental results as well.

A low-complexity frame memory compression algorithm and its implementation for MPEG-2 video decoder

An algorithm and its implementation to compress video frame data to be stored in external memory are proposed, thereby enabling a reduction of memory requirements and bandwidth. To support random access capability, frames are organized as 1/spl times/8 fixed-length segments, which are used as compression units. For both compression efficiency and low complexity, modified Hadamard transform (MHT) and Golomb-Rice (GR) coding are utilized. The compression ratio is fixed at 50% and objective and subjective video quality assessments are performed. Efficient ASIC implementation including Golomb-Rice encoding/decoding is also proposed to reduce the total compression/decompression latency time.

A novel compression algorithm for cell animation images

We propose a novel compression algorithm for cell animation images. Conventional software algorithms include Cinepak, MPEG-1, Indeo5, etc., but these are for natural images, not for cell animation images. At low bit-rates, these provide relatively very poor image quality. In the proposed method, for intra frame coding, octree-based color quantization, ADPCM, and Golomb-Rice code are used. And for inter frame coding, block-to-block difference information is classified and coded. Therefore computational complexity is relatively low. The proposed methods outperform MPEG-1, FLC, and Indeo 5.

Mixed-Mode Fatigue Crack Growth in Orthotropic Steel Decks

The strain energy density factor approach under mixed-mode condition is used for the prediction of crack propagation in the orthotropic steel deck specimen, which is similar to that of existing suspension bridges. Stress intensity factor approach is used to compare with strain energy density factor approach for the fatigue crack growth analysis. The stress intensity factors are computed by numerical extrapolation using cracked models for the different crack length. The study shows that the fatigue crack propagation under mixed-mode condition is slower than that under mode I only. Parametric studies on the initial crack length, critical crack length and parameters related to crack growth equations are performed to show the influence of these parameters on the fatigue life.

Fatigue life prediction of out-of-plane gusset welded joints with curvatures

Publisher Summary Fatigue growth behavior of out-of-plane gusset welded joints is studied using the strain energy density factor approach. Fatigue tests on two types of specimens with curvatures of p = 0 and p = 30 are performed to estimate the fatigue strength under tension. Fatigue crack growth analysis is carried out to show the effects of initial crack shape, initial crack length, and stress ratio. Fatigue crack growth parameters are obtained from crack growth curves assuming constant crack shapes. The results of analysis for the assumed crack shapes agreed well with the experimental data. Fatigue propagation life of the p = 30 specimen is larger than that of the p = 0 specimen.

On the optimization of lifting for the wavelet transform

In this paper, we propose an iterative optimization method using the statistical method. First, the method optimizes the prediction coefficients and then optimizes the update coefficients. To determine both the coefficients and the filter length of the wavelet transform, we introduce an iterative optimization. The proposed method gives the optimal lifting coefficients faster than other methods.

Entropy coders for image compression based on binary forward classification

Entropy coders as a noiseless compression method are widely used as final step compression for images, and there have been many contributions to increase of entropy coder performance and to reduction of entropy coder complexity. In this paper, we propose some entropy coders based on the binary forward classification (BFC). The BFC requires overhead of classification but there is no change between the amount of input information and the total amount of classified output information, which we prove this property in this paper. And using the proved property, we propose entropy coders that are the BFC followed by Golomb-Rice coders (BFC+GR) and the BFC followed by arithmetic coders (BFC+A). The proposed entropy coders introduce negligible additional complexity due to the BFC. Simulation results also show better performance than other entropy coders that have similar complexity to the proposed coders.