Browsing by Author "Chen, LH"

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A 528MS/s frequency synchronizer for OFDM-based UWB system
(2005)
Chen, LH
;
Chang, WC
;
Liu, HY
;
Lee, CY
;
電子工程學系及電子研究所
A novel frequency synchronizer is proposed for 528MHz OFDM-based UWB system. It can reduce 75% memory and 59% power consumption through a low-power scheme based on data. partition. Measured result shows the proposed design can achieve 528MSamples/s throughput in 0.18 mu m CMOS process.
A context-based approach for color image retrieval
(2002-03-01)
Shih, JL
;
Chen, LH
;
資訊工程學系
;
Department of Computer Science
In this paper, a color image retrieval method based on the primitives of images will be proposed. First, the context of each pixel in an image will be defined. Then, the contexts in the image are clustered into several classes based on the algorithm of fast noniterative clustering. The mean of the context in the same class is considered as a primitive of the image. The primitives are used as feature vectors. Since the numbers of primitives between images are different, a specially designed similarity measure is then proposed to do color image retrieval. To better adapt to the preferences of users, a relevance feedback algorithm is provided to automatically determine the weight of each primitive according to the user's response. To demonstrate the effectiveness of the proposed system, several test databases from Corel axe used to compare the performances of the proposed system with other methods. The experimental results show that the proposed system is superior to others.
A fast motion estimation algorithm based on the block sum pyramid
(1997-11-01)
Lee, CH
;
Chen, LH
;
資訊工程學系
;
Department of Computer Science
In this correspondence, a fast approach to motion estimation is presented. The algorithm uses the block sum pyramid to eliminate unnecessary search positions. It first constructs the sum pyramid structure of a block. Successive elimination is then performed hierarchically from the top level to the bottom level of the pyramid. Many search positions can be shipped from being considered as the best motion vector and, thus, the search complexity can be reduced. The algorithm can achieve the same estimation accuracy as the full search block matching algorithm with much lass computation time.
A fast motion estimation algorithm based on the block sum pyramid
(1997-11-01)
Lee, CH
;
Chen, LH
;
資訊工程學系
;
Department of Computer Science
In this correspondence, a fast approach to motion estimation is presented. The algorithm uses the block sum pyramid to eliminate unnecessary search positions. It first constructs the sum pyramid structure of a block. Successive elimination is then performed hierarchically from the top level to the bottom level of the pyramid. Many search positions can be shipped from being considered as the best motion vector and, thus, the search complexity can be reduced. The algorithm can achieve the same estimation accuracy as the full search block matching algorithm with much lass computation time.
A high-speed algorithm for elliptical object detection
(1996-03-01)
Ho, CT
;
Chen, LH
;
交大名義發表
;
資訊工程學系
;
National Chiao Tung University
A high-speed method for elliptical object location is proposed. Through the use of the geometric symmetry, it first locates centers of elliptical objects and classifies the boundary points, Then, each point possible on an elliptical object boundary is used to obtain the remaining three parameters of the elliptical object, Since each boundary point is at most transformed to one point on the parameter space, the proposed method is very fast. Some experimental results are also given to show that the proposed method is better than some existing methods under the consideration of space and storage.
A high-speed algorithm for line detection
(1996-05-01)
Ho, CT
;
Chen, LH
;
資訊工程學系
;
Department of Computer Science
A high-speed method for line detection is proposed in this paper. By shifting the black points in a black/white image I, a parallel line for each straight line on I will be generated. Through the use of the geometric properly on a pair of parallel lines, the parameter sets of those lines possibly on I can be obtained immediately. Since the transform from image space to parameter space is one to few points, the proposed method can significantly reduce the number of transforms for evaluating possible parameter sets. Experimental results are also given to show the correctness and effectiveness of the proposed method.
A new approach for audio classification and segmentation using Gabor wavelets and Fisher Linear Discriminator
(2005-09-01)
Lin, RS
;
Chen, LH
;
資訊工程學系
;
Department of Computer Science
Rapid increase in the amount of audio data demands an efficient method to automatically segment or classify audio stream based on its content. In this paper, based on the Gabor wavelet features, an audio classification and segmentation method is proposed. This method will first divide an audio stream into clips, each of which contains one-second audio information. Then, each clip is classified as one of two classes or five classes. Two classes contain speech and music; pure speech, pure music, song, speech with music background, and speech with environmental noise background are for five classes. Finally, a merge technique is provided to do segmentation. In order to make the proposed method robust for a variety of audio sources: we use Fisher Linear Discriminator to obtain features with the highest discriminative ability Experimental results show that the proposed method can achieve over 98% accuracy rate for speech and music discrimination, and more than 95% for a five-way discrimination. By checking the class types of adjacent clips, we can also identify more than 95% audio scene breaks in audio sequence.
A new approach for classification of generic audio data
(2005-02-01)
Lin, RS
;
Chen, LH
;
資訊工程學系
;
Department of Computer Science
The existing audio retrieval systems fall into one of two categories: single-domain systems that can accept data of only a single type (e.g. speech) or multiple-domain systems that offer content-based retrieval for multiple types of audio data. Since a single-domain system has limited applications, a multiple-domain system will be more useful. However, different types of audio data will have different properties, this will make a multiple-domain system harder to be developed. If we can classify audio information in advance, the above problems can be solved. In this paper, we will propose a real-time classification method to classify audio signals into several basic audio types such as pure speech, music, song, speech with music background, and speech with environmental noise background. In order to make the proposed method robust for a variety of audio sources, we use Bayesian decision function for multivariable Gaussian distribution instead of manually adjusting a threshold for each discriminator. The proposed approach can be applied to content-based audio/video retrieval. In the experiment, the efficiency and effectiveness of this method are shown by an accuracy rate of more than 96% for general audio data classification.
A new approach for recognizing multifont Chinese characters used in a special application
(1996-05-01)
Chen, LH
;
Lee, YK
;
資訊工程學系
;
Department of Computer Science
Many approaches for recognizing all of the 5401 commonly used Chinese characters have been proposed, but they are complex, For some applications such as cheques, receipts, addresses, in Chinese, etc., only a limited set of printed characters is needed, but they are usually require a real time response and a high recognition rate. Based on this reason, here we provide a simpler approach to meet these two requirements. The approach takes horizontal strokes, vertical ones and crossings among these strokes as the character features. A fast modified Hough transform is provided to extract these features, it satisfies an important stroke property that a dotted line must not be a real stroke. In the learning stage, an error measure is defined and an optimal stroke matching algorithm is proposed to establish an accurate random model for each type of characters. In the recognition stage, another error measure is defined and a nearly-optimal matching algorithm is presented to speed up the recognition process. It is worth mentioning that the approach does not use any thinning process. Some experimental results are also provided to show the effectiveness of the proposed recognizer.
A new method for extracting primitives of regular textures based on wavelet transform
(2002-02-01)
Lee, KL
;
Chen, LH
;
資訊工程學系
;
Department of Computer Science
In this paper, a new method for extracting primitives of a regular texture via wavelet transform is provided. Each primitive is restricted to be a parallelogram. The main work of the proposed method is to extract the two displacement vectors that form the primitive of a regular texture. A contrast-based criterion is used to select appropriate subimages obtained from wavelet transform for detecting displacement vectors. An edge thresholding method is then performed on the subimages selected to locate edges. Based on these edges, Hough transform is applied to extract the displacement vectors. The proposed method is quite efficient and can get more accurate results for displacement vectors when comparing to traditional co-occurrence matrix based methods. Synthesized textures are provided to show the effectiveness of the proposed method.
A new slow-motion replay extractor for soccer game videos
(2003-12-01)
Farn, EJ
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Chen, LH
;
Liou, JH
;
資訊工程學系
;
Department of Computer Science
In this paper, we will present a method to extract slow-motion replays in a soccer game video. According to our observation, a slow-motion replay always happens as a single shot and appears between two gradual transitions. Based on this fact, a video will first be segmented into individual shots and only those shots appearing between two gradual transitions are considered as candidate shots. There are two kinds of slow-motion replays. One comes from a standard camera and consists of some repeating or inserted frames. The other is from a high-speed camera with larger variation between two consecutive frames. Based on these features, an extractor is then provided to check if a candidate shot is a slow motion replay. Some experimental results are given to show the effectiveness of the proposed method.
A new system for trademark segmentation and retrieval
(2001-11-01)
Shih, JL
;
Chen, LH
;
資訊工程學系
;
Department of Computer Science
With the increase in the number of trademarks, trademark imitation has become a serious problem. Thus, building an efficient trademark retrieval system is imperative. In this paper, such a system is presented. First, a semi-automatic segmentation method is proposed to extract the shapes of those representative objects, called 'masks', in each trademark. Next, some features are selected to describe a mask. These include invariant moments, the histogram of edge directions, and two kinds of transform coefficients that are robust to geometric deformation. Then, based on the rank of the feature distance, a similarity measure is provided to do the similar trademark retrieval. Finally, a feedback algorithm is also proposed to automatically determine the weight of each feature according to the user's response. Furthermore, in order to show the effectiveness of the proposed system, two databases from MPEG-7 test database are used to compare the performances of the proposed system and those methods using chain code, Zernike moments or MPLV as features. The experimental results show that the proposed system is superior to others. (C) 2001 Elsevier Science B.V. All rights reserved.
A system for a new two-dimensional code: Secure 2D code
(1998-10-01)
Yeh, CT
;
Chen, LH
;
資訊工程學系
;
Department of Computer Science
A new 2D code called Secure 2D code is designed in this paper, both encoder and decoder are also proposed. Secure 2D code can store any kind of data and provides high security. With regard to security, the input data is divided into two parts: general and secret. The general data is transformed into a 2D code pattern, then secret data is hidden in the 2D code pattern. To raise the reading speed and allow various reading environments, some features are added around the 2D code pattern boundary. As to the reliability, RS code is adopted to treat damaged patterns.
An area and power efficient frame synchronizer for 480Mb/s OFDM-based UWB system
(2005)
Chang, WC
;
Chen, LH
;
Liao, WC
;
Liu, HY
;
Lee, CY
A novel frame synchronizer is proposed for OFDM-based UWB system. Integrating the improved matched filters and dynamic threshold design, the proposed design can reduce 65% area and 58% power with an acceptable performance loss. It can achieve 528MS/s throughput for 480Mb/s UWB system in 0.18 mu m CMOS process.
An efficient computation method for the texture browsing descriptor of MPEG-7
(2005-05-01)
Lee, KL
;
Chen, LH
;
資訊工程學系
;
Department of Computer Science
In this paper, an efficient computation method for computing the texture browsing descriptor of MPEG-7 is provided. Texture browsing descriptor is used to characterize a texture's regularity, directionality and coarseness. To compute the regularity of textures, Fourier transform is first performed. To get more discriminative features for regularity computation, the Fourier spectrum is treated as an image and the Fourier transform is performed again to produce an enhanced Fourier spectrum. A regularity measure based on the variance of the radial wedge distribution is then calculated to determine the regularity of textures. For regular textures, the texture primitives are assumed to be parallelograms, the two dominant directions are extracted by Hough transform. A scale computation method is then provided to determine the scales corresponding to the two dominant directions. In addition, principal component analysis is provided to detect textures with only one dominant direction. Experiments of texture browsing, coarse classification of textures and similarity-based image-to-image matching are performed on the texture images of Brodatz album and Corel Gallery image database to demonstrate the efficiency and effectiveness of the proposed method. The proposed method can be used in the applications of texture browsing and texture retrieval. (c) 2005 Elsevier B.V. All rights reserved.
Colour image retrieval based on primitives of colour moments
(2002-12-01)
Shih, JL
;
Chen, LH
;
資訊工程學系
;
Department of Computer Science
A colour image retrieval method based on the primitives of colour moments is proposed. First, an image is divided into several blocks. Then, the colour moments of all blocks are extracted and clustered into several classes. The mean moments of each class are considered as a primitive of the image. All primitives are used as features. Since two different images may have different numbers of features, a new similarity measure is then proposed. To demonstrate the effectiveness of the proposed method, two test databases from Corel are used to compare the performances of the proposed method with other existing ones. The experimental results show that the proposed method is usually better than the others. Furthermore, since for a few special types of images, other methods may have better results occasionally, a relevance feedback algorithm is also provided to automatically determine the best method according to the user's response.
Content-based audio retrieval based on Gabor wavelet filtering
(2005-09-01)
Lin, RS
;
Chen, LH
;
資訊工程學系
;
Department of Computer Science
Rapid increase in the amount of audio data and especially music collections demand an efficient method to automatically retrieve audio objects based on its content. In this paper, based on the Gabor wavelet features, we will propose a method for content-based retrieval of perceptually similar music pieces in audio documents. It allows the user to select a reference passage within an audio file and retrieve perceptually similar passages such as repeating phrases within a music piece, similar music clips in a database or one song sung by different persons or in different languages. The proposed method will first divide an audio stream into clips, each of which contains one-second audio information. Then, the frame-based features of each clip are extracted based on the Gabor wavelet filters. Finally,, a similarity measuring technique is provided to perform pattern matching on the resulting sequences of feature vectors. Experimental results show that the proposed method can achieve over 96% accuracy rate for audio retrieval.
Content-based color trademark retrieval system using hit statistic
(2002-08-01)
Wang, CC
;
Chen, LH
;
資訊工程學系
;
Department of Computer Science
This paper proposes a content-based color trademark retrieval system. First, the edges of each color trademark are detected. Then, the smallest circle that covers the trademark is derived. Based on the smallest circle and edges, the feature called hit statistic on a dartboard of the color trademark is extracted. Using this feature, this paper constructs an efficient and simple color trademark retrieval system, which is robust to rotation, translation, scaling and some geometric distortions. Some experiments are conducted to compare the proposed system with the existing one using Zernike moment, and the results show that the proposed system is superior to that using Zernike moment.
Development of a parallel Poisson's equation solver with adaptive mesh refinement and its application in field emission prediction
(2006-06-15)
Hsu, KH
;
Chen, PY
;
Hung, CT
;
Chen, LH
;
Wu, JS
A parallel electrostatic Poisson's equation solver coupled with parallel adaptive mesh refinement (PAMR) is developed in this paper. The three-dimensional Poisson's equation is discretized using the Galerkin finite element method using a tetrahedral mesh. The resulting matrix equation is then solved through the parallel conjugate gradient method using the non-overlapping subdomain-by-subdomain scheme. A PAMR module is coupled with this parallel Poisson's equation solver to adaptively refine the mesh where the variation of potentials is large. The parallel performance of the parallel Poisson's equation is studied by simulating the potential distribution of a CNT-based triode-type field emitter. Results with similar to 100 000 nodes show that a parallel efficiency of 84.2% is achieved in 32 processors of a PC-cluster system. The field emission properties of a single CNT triode- and tetrode-type field emitter in a periodic cell are computed to demonstrate their potential application in field emission prediction. (c) 2006 Elsevier B.V. All rights reserved.
High capacity image steganographic model
(2000-06-01)
Lee, YK
;
Chen, LH
;
資訊工程學系
;
Department of Computer Science
Steganography is an ancient art of conveying messages in a secret way that only the receiver knows the existence of a message. So a fundamental requirement for a steganographic method is imperceptibility; this means that the embedded messages should not be discernible to the human eye. There are two other requirements, one is to maximise the embedding capacity, and the other is security. The least-significant bit (LSB) insertion method is the most common and easiest method for embedding messages in an image. However, how to decide on the maximal embedding capacity for each pixel is still an open issue. An image steganographic model is proposed that is based on variable-size LSB insertion to maximise the embedding capacity while maintaining image fidelity. For each pixel of a grey-scale image, at least four bits can be used for message embedding. Three components are provided to achieve the goal. First, according to contrast and luminance characteristics, the capacity evaluation is provided to estimate the maximum embedding capacity of each pixel. Then the minimum-error replacement method is adapted to find a grey scale as close to the original one as possible. Finally, the improved grey-scale compensation, which takes advantage of the peculiarities of human visual system, is used to eliminate the false contouring effect. Two methods, pixelwise and bitwise, are provided to deal with the security issue when using the proposed model. Experimental results show effectiveness and efficiency of the proposed model.