• Journal of Korea Multimedia Society
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• v.7 no.9
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• pp.1246-1254
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• 2004

This paper presents a image coding method that is well adaptive to close-range video transmission because of its low titrate and simple coding procedure. At first, it reduces temporal redundancies by performing image DPCM between previous frame and current frame, and makes wavelet transformed image of this difference image. Then, the coefficients are quantized selectively by using the coefficient values of base level and mid-frequency level because inter-level redundancies are widely exists in multi-resolution images. Finally quantized coefficients are made iron the function that implies the target bitrate, the average coefficient energy, and the value of the level. The proposed method shows the effective Performance in the experiments using the continuous motion images and transition images.

• Journal of the Korea Society of Computer and Information
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• v.4 no.3
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• pp.73-77
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• 1999

In this paper. wavelet transform coding for image conference is studied. Original video frames are transformed into hierarchical pyramidal images with multiresolution using the band property of wavelet transform coefficients. Moving information between neighboring frames is obtained from the low-resolution band. Also, to control the video coding procedure. a new picture set filter is proposed. This filter controls the compression ratio of each frame depending on the correlation to the reference frame by selectively eliminating less important high-resolution areas. Consequently. video quality can be preserved and bit rate can be controlled adaptively In the simulation, to test the performance of the proposed coding method, comparisons with the full search block matching algorithm and the differential image coding algorithm are made. Consequently. the proposed method shows a reasonably good performance over existing ones.

• Journal of Korea Multimedia Society
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• v.10 no.6
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• pp.737-744
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• 2007

This paper proposes the blind watermarking algorithm for digital video based on magnitude modulus subband in wavelet transform domain. After transforming each of frames into wavelet domain, the proposed algorithm divides LH, HL, and HH subbands of 2-level into $3{\times}3$ blocks and calculates average magnitude modulus of all blocks. Then the watermark bit is embedded into a target magnitude modulus comparing with an average magnitude modulus within a block. Experimental results were confirmed that the proposed algorithm has the good robustness against MPEG and frame attacks than the conventional algorithm.

• Proceedings of the IEEK Conference
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• 2003.11a
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• pp.433-436
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• 2003

In this paper, the efficient motion estimation and compensation method for 3 dimensional wavelet transform is proposed. Recently, since the compression performance and scalable functionality are provided by wavelet transform, many researches have been carried out for applying to the video compression. For the temporal filtering, motion estimation and compensation techniques are used, but the unconnected pixels, which are produced by motion compensation result into the degradation of coding performance and quality of the picture. For the efficient motion compensated temporal filtering by reducing the number of these unconnected pixels, we propose the variable block size motion estimation and compensation method. Also we propose a method that determines the block size using rate-distortion optimization technique according to the local characteristics of the frame. The simulation results show the improved performances than the MPEG-4 scalable coding methods and the 3 dimensional wavelet coding methods using fixed block size motion estimation and compensation.

• Proceedings of the IEEK Conference
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• 2007.07a
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• pp.221-222
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• 2007

This paper presents wavelet-based moving object segmentation using double change detection and background registration. Three successive frame differences for detection change were used in the wavelet domain. The background was constructed with the wavelet coefficients in the lowest frequency subband which are the approximated version of an image. Combining double change detection and background registration, we can obtain an efficient moving object segmentation algorithm.

• Structural Engineering and Mechanics
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• v.56 no.3
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• pp.423-442
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• 2015

This study examines the wavelet transform for output-only system identification of ambient excited engineering structures with emphasis on its utilization for modal parameter estimation of high-order and closely-spaced modes. Sophisticated time-frequency resolution analysis has been carried out by employing the modified complex Morlet wavelet function for better adaption and flexibility of the time-frequency resolution to extract two closely-spaced frequencies. Furthermore, bandwidth refinement techniques such as a bandwidth resolution adaptation, a broadband filtering technique and a narrowband filtering one have been proposed in the study for the special treatments of high-order and closely-spaced modal parameter estimation. Ambient responses of a 5-story steel frame building have been used in the numerical example, using the proposed bandwidth refinement techniques, for estimating the modal parameters of the high-order and closely-spaced modes. The first five natural frequencies and damping ratios of the structure have been estimated; furthermore, the comparison among the various proposed bandwidth refinement techniques has also been examined.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.1C
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• pp.124-130
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• 2008

We present in this paper a method of digital watermarking for video data based on the discrete wavelet transform. In the proposed method, a watermark signal is inserted into the decompressed bitstream while detection is performed using the uncompressed video. This method allows detection if video has been manipulated or its format changed. We embed the watermark in the lowest frequency components of each frame in the un-coded video by using wavelet transform. The watermark can be extracted directly from the decoded video without access to the original video. Experimental results show that the proposed method gives the watermarked video of better quality and is robust against MPEG coding, down sampling and re-encoding to other type of video format such as MPEG4, H.264

• Proceedings of the Korea Multimedia Society Conference
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• 1998.04a
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• pp.110-115
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• 1998

웨이브릿 해석에서 CWT(continuous wavelet transform)에서는 Plancherel 형태의 복원 정리가 성립하고, 웨이브릿 급수는 frame 이론과 다해상도 이론(multiresolution analysis)을 활용한 이산복원정리가 성립한다. 복원정리가 만들어짐에 따라 이에 상응하는 웨이브릿이 생성되는데, CWT에서는 허용조건(admissibility condition)을 만족하는 basic wavelet이고, 웨이브릿 급수에서는 MRA를 이용한 Daubechies 웨이브릿, frame 이론을 이용한 Meyer 웨이브릿 등을 생각할 수 있다. 본 연구에서는 CWT에서 사용한 허용조건을 자연스럽게 확장함으로써 기존의 것보다 간편하고 활용도가 우수한 이산복원정리를 발견하고, 이에 상응하는 보다 만들기 쉬운 새로운 형태의 L1 웨이브릿군을 개발함을 목적으로 한다. 본 연구에 개발한 새로운 웨이브릿을 사용하여 시간-주파수에서의 신호 복원 및 분석에 응용한다.

• Journal of the Korea Computer Industry Society
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• v.6 no.2
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• pp.271-278
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• 2005

This paper proposed a new time adapted threshold using the standard deviations of Wavelet coefficients after Wavelet transform by frame scale. The time adapted threshold is set up using the sum of standard deviations of Wavelet coefficient in level 3 approximation and weighted level 1 detail. Level 3 approximation coefficients represent the voiced sound with low frequency and level 1 detail coefficients represent the unvoiced sound with high frequency. After reducing noise by soft thresholding with the proposed time adapted threshold, there are still residual noises in silent interval. To reduce residual noises in silent interval, a detection algorithm of silent interval is proposed. From simulation results, it is demonstrated that the proposed algorithm improves SNR and MSE performance more than Wavelet transform and Wavelet packet transform does.

• Smart Structures and Systems
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• v.1 no.1
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• pp.29-46
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• 2005

In this study, a wavelet packet based method is proposed for identifying damage occurrence and damage location for beam-like structures. This method assumes that the displacement or the acceleration response time histories at various locations along a beam-like structure both before and after damage are available for damage assessment. These responses are processed through a proper level of wavelet packet decomposition. The wavelet packet signature (WPS) that consists of wavelet packet component signal energies is calculated. The change of the WPS curvature between the baseline state and the current state is then used to identify the locations of possible damage in the structure. Two numerical studies, one on a 15-storey shear-beam building frame and another on a simply-supported steel beam, and an experimental study on a simply-supported reinforced concrete beam are performed to validate the proposed method. Results show the WPS curvature change can be used to locate both single and sparsely-distributed multiple damages that exist in the structure. Also the accuracy of assessment does not seem to be affected by the presence of 20-15dB measurement noise. One advantage of the proposed method is that it does not require any mathematical model for the structure being monitored and hence can potentially be used for practical application.