• Journal of the Korean Institute of Telematics and Electronics B
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• v.30B no.4
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• pp.130-137
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• 1993

In this paper, A progressive coding of mean difference pyramid by Hadamard transform of the difference between two successive pyramid levels has been studied. A block adaptive bit allocation method based on ac energy of each sub-block has been proposed, which efficiently reduces the final distortion in the progressive transmission of image parameters. In our scheme, the dc energy equals the sum of the quantization errors of the Hadamard transform coefficients at previous level. Therefore proposed allocation method includes the estimation of dc energy at each pyramid level. Computer simulation results show some improvements in terms of MSE and picture quality over the conventional fixed allocation scheme.

• Journal of Communications and Networks
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• v.5 no.2
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• pp.141-149
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• 2003

In this paper, we investigate design criteria and the performance of the space-frequency bit-interleaved coded modulation (SF-BICM) systems in frequency-selective Rayleigh fading channels. To determine the key parameters that affect the performance of SF-BICM, we derive the pairwise error probability (PEP) in terms of the determinant of the matrix corresponding to any two codewords. We prove that the bit-interleavers do the function of distributing the nonzero bits uniformly such that two or more nonzero bits are seldom distributed into the symbols that are transmitted in the same frequency bin. This implies that the bit-interleavers transform an SF-BICM system into an equivalent 1-antenna system. Based on this, we present design criteria of SFBICM systems that maximizes the diversity order and the coding gain. Then, we analyze the performance of SF-BICM for the case of 2-transmit antennas and 2-multipaths by deriving a frame error rate (FER) bound. The derived bound is accurate and requires only the distance spectrum of the constituent codes of SF-BICM. Numerical results reveal that the bound is tight enough to estimate the performance of SF-BICM very accurately.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.8
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• pp.1790-1802
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• 1997

A wavelet transform coding method that fulfills the requirements of HD-VCR(high definition video casstte recorder) for studio applications in proposed. A constant bit rate is achieved by a forward rate control technique whcih determins the quantizer stepsize based on the coding results fo the previous frame. We also propose a two-level coder that consists of both the IDC(independently decodable code) and the DDC(dependently decodable code). To minimize error propagation, the transformed coefficients are restructured into transform blocks which are represented by a tree structure. The result shows thta the proposed coding scheme produces better picture quality with block effects than that of DCT(discrete cosine transform) based coding schemes at the same compression ratio. The proposed method meets most of the requirements of HD-VCR.

• The Journal of the Acoustical Society of Korea
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• v.21 no.5
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• pp.462-470
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• 2002

Wideband speech, characterized by a bandwidth of 50∼7000 ㎐, sounds more natural and intelligible, and is less tiring to listen to when compared to narrowband speech characterized by a bandwidth of 300∼3400 ㎐. Wideband speech coders, however, have not been as successful as the narrowband speech coders because of their higher bit rate. In this paper, we propose a new wideband speech coder which combines the European standard of a narrowband speech coder, i.e., GSM-EFR, and a transform coder using the discrete wavelet transform. The proposed wideband speech coder operates as follows input speech is first split into two subbands with equal bandwidth and the two subband signals are coded and decoded by each subband coder. A GSM-EFR is adopted as a lower subband coder and a subband coder with wavelet transformed speech is designed for a upper subband coder. The total bit rate of the proposed coder is 18.9kbps (12.2 kbps for lower band coder and 6.7 kbps for upper band coder), and informal listening test results have shown that the proposed coder has comparable speech quality to that of G.722 with 56 kbps.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 1999.05a
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• pp.272-275
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• 1999

In this paper, a wavelet transform-based adaptive interference excision scheme using the adaptive algorithm which suppresses narrow band interference in the wavelet transform domain for the direct spread modulation system application, is introduced. Using the Monte-Carlo simulation, the bit error probabilities of the direct spread communication systems with the excision systems of two kinds of Daubechies wavelets (db2, db8) in the transform domain, are analysed. With these results, it is shown that the performance of a system depends on the characteristics of wavelet being used. And with this scheme, we expect effective improvements in the direct spread communication system performance.

• Journal of Broadcast Engineering
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• v.16 no.5
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• pp.861-872
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• 2011

Many fast block-matching algorithms (BMAs) in motion estimation field reduce computational complexity by screening the number of checking points. Although many fast BMAs reduce computations, sometimes they should endure matching errors in comparison with full-search algorithm (FSA). In this paper, a novel fast BMA for constrained one-bit transform (C1BT)-based motion estimation is proposed in order to decrease the calculations of the block distortion measure. Unlike the classical fast BMAs, the proposed algorithm shows a new approach to reduce computations. It utilizes the binomial distribution based on the characteristic of binary plane which is composed of only two elements: 0 and 1. Experimental results show that the proposed algorithm keeps its peak signal-to-noise ratio (PSNR) performance very close to the FSA-C1BT while the computation complexity is reduced considerably.

• Proceedings of the IEEK Conference
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• 2003.11a
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• pp.263-266
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• 2003

In this paper, we propose a new progressive image transmission system including the image coding scheme that efficiently uses the relationship between the properties of a spatial image and its wavelet transform. Firstly, an original image is decomposed into several layers by the wavelet transform, and simultaneously decomposed into 2"x2" blocks. Each image is classified into two image types according to the standard deviations of its blocks. And then each block is categorized into two regions by different thresholds according to the image types, i.e., significant activity region (SAR) and insignificant activity region (IAR). Simulation results show that the proposed coding method has better performance than the EZW and SPIHT in terms of image quality and transmitted bit-rate. In addition, it can be applied to the applications requiring the progressive image transmission.nsmission.

• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.351-355
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• 1999

The amount of data stored, processed and transmitted in the multi-media systems has been growing very fast, especially for the image data. For example, it takes 0.75Mbytes to store 512 12 pixels of 24-bit color image. A video signal with 30 frames per second will require 22.5Mbytes of storage space. To solve this problem, we need a good image compression technique. Recently, many researches on the image compression technique based on the wavelet transform are being pursued to overcome the problems of traditional JPEG. This paper describes the architecture and design of two-dimensional wavelet transform circuit. To keep the sire of the circuit small, we tried to minimize the internal storage space by using external SDRAM. This circuit was designed in Verilog-HDL, synthesized using Design Compiler and verified using Verilog-XL.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.15 no.2
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• pp.113-122
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• 2005

In this paper, we propose a multi-watermarking algorithm to satisfy two purposes: fragility against malicious attacks and robustness against non-malicious attacks. The algorithm can be used for image authentication using coefficients of Discrete Wavelet Transform(DWT). In the proposed method, watermarks are generated by combining binary image with some features extracted from the subband LL3, and then they are embedded into both the spatial and frequency domain. That is, on the spatial domain they are embedded into the Least Significant Bit(LSB) of all pixels of image blocks, and on the frequency domain the coefficients of the subband LH2 and HL2 are adjusted according to the watermarks. Thus the algorithm not only resists malicious attack but also permits non-malicious attacks such as blurring, sharpening, and JPEG compression.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.4A
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• pp.336-344
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• 2005

Discrete Wavelet Transform(DWT) is the oncoming generation of compression technique that has been selected for MPEG4 and JEPG2000, because it has no blocking effects and efficiently determines frequency property of temporary time. In this paper, we propose an efficient bit-serial architecture for the low-power and low-complexity DWT filter, employing two-channel QMF(Qudracture Mirror Filter) PR(Perfect Reconstruction) lattice filter. The filter consists of four lattices(filter length=8) and we determine the quantization bit for the coefficients by the fixed-length PSNR(peak-signal-to-noise ratio) analysis and propose the architecture of the bit-serial multiplier with the fixed coefficient. The CSD encoding for the coefficients is adopted to minimize the number of non-zero bits, thus reduces the hardware complexity. The proposed folded 1D DWT architecture processes the other resolution levels during idle periods by decimations and its efficient scheduling is proposed. The proposed architecture requires only flip-flops and full-adders. The proposed architecture has been designed and verified by VerilogHDL and synthesized by Synopsys Design Compiler with a Hynix 0.35$\mu$m STD cell library. The maximum operating frequency is 200MHz and the throughput is 175Mbps with 16 clock latencies.