Browsing by Author "Hu, YQ"

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A discrete wavelet transform codec design
(2004-12-01)
Hu, YQ
;
Wu, BF
;
Su, CY
;
電控工程研究所
;
Institute of Electrical and Control Engineering
This manuscript presents a VLSI architecture and its design rule, called embedded instruction code (EIC), to realize discrete wavelet transform (DWT) codec in a single chip. Since the essential computation of DWT is convolution, we build a set of multiplication instruction, MUL, and the addition instruction, ADD, to complete the work. We segment the computation paths of DWT according to the multiplication and addition, and apply the instruction codes to execute the operators. Besides, we offer a parallel arithmetic logic unit (PALU) organization that is composed of two multipliers and four adders (2M4A) in our design. Thus, the instruction codes programmed by EIC control the PALU to compute efficiently. Additionally, we establish a few necessary registers in PALU, and the number of registers depends on the wavelet filters' length and the decomposition level. Yet, the numbers of multipliers and adders do not increase as we execute the DWT or the inverse DWT (IDWT) in multilevel decomposition. Furthermore, we deduce the similarity between DWT and IDWT, so the functions can be integrated in the same architecture. Besides, we schedule the instructions; thus, the execution of the multilevel processes can be achieved without superfluous PALU in a single chip. Moreover, we solve the boundary problem of DWT by using the symmetric extension. Therefore, the perfect reconstruction (PR) condition for DWT requirement can be accomplished. Through EIC, we can systematically generate a flexible instruction codes while we adopt different filters. Our chip supports up to six levels of decomposition, and versatile image specifications, e.g., VGA, MPEG-1, MPEG-2, and 1024 x 1024 image sizes. The processing speed is 7.78 Mpixel/s when the operation frequency, for normal case, is 100 MHz.
Adaptive self-quantization in wavelet-based fractal image compression
(1999-05-01)
Wu, BF
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Hu, YQ
;
Hsu, HH
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電控工程研究所
;
Institute of Electrical and Control Engineering
Finding a model to quantize the scale factors in wavelet-based fractal image compression is a complicated issue. To avoid error, it is helpful to model the distribution of the scale factors and quantize them before the computation process by iterated function systems. Traditionally, a fixed model with uniform distribution was frequently adopted. This is not sophisticated enough, however, to quantize these scale factors from errors since, in general, the factors are not uniformly distributed. We propose an adaptive algorithm with self-quantization to overcome this drawback. Except for the functions of adaptation and self-quantification, the approach has the optimal property that the fundamental objective is to reduce the quantization errors.
An efficient VLSI implementation of the discrete wavelet transform using embedded instruction codes for symmetric filters
(2003-09-01)
Wu, BF
;
Hu, YQ
;
電控工程研究所
;
Institute of Electrical and Control Engineering
This work presents a VLSI design rule, namely, an embedded instruction code (EIC), for the discrete wavelet transform (DWT). Our approach derives from the essential computations of DWT, and we establish a set of multiplication instructions, MUL,, and the addition instruction, ADD. In addition, we propose a parallel arithmetic logic unit (PALU) with two multipliers and four adders, called 2M4A. With these requirements, the DWT computation paths can be calculated more efficiently with limited PALUs. Furthermore, since the EIC is operated under the PALU, the number of needed inner registers depends on the wavelet filters' length. Besides, the boundary problem of DWT has also been resolved by the symmetric extension. Moreover, the two-dimensional inverse DWT (2-D IDWT) can be completed using the same PALU for 2-D DWT; the only changes needed to be made are the instruction codes and coefficients. Our chip supports up to six levels of decomposition and versatile image specifications, e.g., VGA, MPEG-1, MPEG-2 and 1024 x 1024 image sizes.
An integrated method in wavelet-based image compression
(1998-08-01)
Hsu, HH
;
Hu, YQ
;
Wu, BF
;
電控工程研究所
;
Institute of Electrical and Control Engineering
In this paper, we propose an integrated image compression method, which contains the discrete wavelet transform, scalar quantization and some lossless codings, to gain higher compression ratios while maintaining the image fidelity. The discrete wavelet transform has the properties of entropy reduction and energy concentration in high frequency subimages. An innovative approach, called revised rein-length coding, is proposed to improve the compression performance. The idea of this approach is to represent the appearance of symbols of the run-length cone in exponential expression for saving the storage in bits. The differential pulse code modulation is used to reduce the entropy of the lowest frequency subimage of the discrete wavelet transform and to achieve high compression effects losslessly. (C) 1998 The Franklin Institute. Published by Elsevier Science Ltd.
An integrated method to image compression using the discrete wavelet transform
(1997)
Hu, YQ
;
Hsu, HH
;
Wu, BF
;
交大名義發表
;
電控工程研究所
In this paper, we propose an integrated image compression method, which contains the discrete wavelet tranform scalar quantization and some lossless codings, to gain higher compression ratios while maintaining the image fidelity. The discrete wavelet transform, a multiresolution technique, has the properties of entropy reduction and energy concentration in high frequency subimages. Scalar quantizer is applied to the high frequency components since those histograms can be modelled to the generalized Gaussian distribution. These subimages with small relative energy can be dropped entirely to compensate the compression ratio if the optimal scalar quantization is adopted. An innovative approach, named as revised run-length coding, is proposed to improve the compression performance. The idea of this approach is to represent the appearance of symbols of run-length codes in exponential expression for saving the storage In bits. One coding method, differential pulse coded modulation, is introduced to reduce the entropy of the lowest frequency subimage performed after the discrete wavelet transform and to acheive the high compression effect losslessly. The experimental results are compared with some well-known methods, for example, JPEG, (entropy constrained) vector quantization, fractal-based compression method and wavelet with variable-length coding.