• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.6
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• pp.21-27
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• 2019

The video compression standard required a processing technique for a high resoluion image and increased the coding size to increase the resolution of the image. Accurate motion estimation and increased coding size provide high accuracy and compression rate, but there is a problem of increased computational complexity. In this paper, we use DCT - based motion estimation in the frequency domain to reduce complexity. However, we found that the DCT and quantization process used in a general video encoder are applied to the frequency domain encoder, resulting in problems caused by the scaling process. Therfore, in this paper, we extract the scaling matrix that can be applied in the DCT step and resolve the, and improve the performance of motion estimation using increased coding size.

• IEIE Transactions on Smart Processing and Computing
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• v.2 no.1
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• pp.20-26
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• 2013

Image noise reduction in the frequency domain by thresholding is simple, but quite effective. Wavelet domain thresholding has been an active area of research but relatively little work has been published on DCT domain denoising. A novel method for determining the hard threshold for the DCT domain denoising is proposed. The low amplitude DCT coefficients are discarded until the cumulative sum of the discarded signal energy is comparable to that of noise in each DCT block. Cycle spinning is also applied to reduce block artifacts. The proposed method is quite effective and simple enough to be used in portable devices.

• Proceedings of the KIEE Conference
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• 2007.04a
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• pp.38-40
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• 2007

In this paper, we propose a novel architecture, which is based on DCT (Discrete Cosine Transform), for ME (Motion Estimation) and MC (Motion Compensation). The traditional algorithms of ME and MC based on DCT did not suffer the advantage of the coarseness of the 2-dimensional DCT (2-D DCT) coefficients to reduce the operational time. Therefore, we derive a recursion equation for transform-domain ME and MC and design the structure by using highly regular, parallel, and pipeline processing elements. The main difference with others is removing the IDCT block by using to transform domain. Therefore, the performance of our algorithm is more efficient in practical image processing such as DVR (Digital Video Recorder) system. We present the simulation result which is compare with the spatial domain methods. it shows reducing the calculation cost. compression ratio. and peak signal to noise ratio (PSNR).

• Journal of Korea Multimedia Society
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• v.9 no.10
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• pp.1276-1281
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• 2006

In this paper, We proposed a robust blind digital watermarking algorithm using variance and DCT domain. The proposed method embedded watermark signals into DC components of $8{\times}8$ block DCT using valiance, texture regions and smooth regions. In the digital watermarking algorithms using DCT domain, more robustness can be achieved if watermarks are embedded in DC components since DC components have much larger perceptual capacity than AC components. Experiment showed that robustness of the proposed method better than that of the conventional methods in JPEG quality and scaling attack.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.8
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• pp.1227-1237
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• 1989

In this paper, we propose a lossless progressive image transmission scheme using hierarchical pyramid structure and classified vector quantizer in DCT domain. By adopting DCT to the hierarchical pyramid signals, we can reduce the spatial redundance. Moreover, the DCT coefficients can be encoded efficiently by using classified vector quantizer in DCT domain. The classifier is simply based on the variance of a subblock. Also, the mirror set of training set of images can improve the robustness of codebooks. Progressive image transmission can be achieved through following processes: from top to bottom level of planes in a pyramid, and from high to low AC variance class in a plane. Some simulation results with real images show that the proposed coding scheme yields a good performance at below 0.3 bpp and an excellent result at 0.409 bpp. The proposed coding scheme is well suited for lossless progressive image transmission as well as image data compression.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.37 no.2
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• pp.28-38
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• 2000

This paper proposes a fractal compression method using the domain classification and local searching, which utilize DCT coefficient characteristic Generally, the fractal Image encoding method has a time consuming process to search a domain to be matched with range block In order to reduce computation complexity, the domain and range regions are respectively classified into 4 category by using the characteristics of DCT coefficients and each range region is encoded by a method suitable for the property of its category Since the bit amount of the compressed image depends on the number of range blocks, the matching of domain block and range block is induced on the large range block by using local search, so that compression ratio is increased by reducing the number of range block In the local search, the searching complexity is reduced by determining the direction and distance of searching using the characteristics of DCT coefficients The experimental results shows that the proposed algorithm have 1 dB higher PSNR and 0 806 higher compression ratio than previous algorithm.

• Proceedings of the KIEE Conference
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• 2004.11c
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• pp.178-180
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• 2004

In this work, we propose new method of sigma filtering for efficient filtering and preserving edge regions in DCT Domain. In block-based image compression technique, the image is first divided into non-overlapping $8{\times}8$ blocks. Then, the two-dimensional DCT is computed for each $8{\times}8$ block. Once the DCT coefficients are obtained, they are quantized using a specific quantization table. Quantization of the DCT coefficients is a lossy process, and in this step, noise is added. In this work, we combine IDCT matrix and filter matrix to a new matrix to simplify filtering process to remove noise after IDCT in spatial domain, for each $8{\times}8$ DCT coefficient block, we determine whether this block is edge or homogeneous region. If this block is edge region, we divide this $8{\times}8$ block into four $4{\times}4$ sub-blocks, and do filtering process for sub-blocks which is homogeneous region. By this process, we can remove blocking artifacts efficiently preserving edge regions at the same time.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.8
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• pp.1265-1274
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• 1990

A new classified VQ scheme for DCT coefficients(DCT-CVQ) is proposed for still image coding. DCT coefficient matrices are classified into six classes by ac coefficients that well represent edge characteristics and the distribution of ac energy in the DCT domain. To reduce the complexity of, VQ, ac transform coefficients are partitioned into several vectors, and an adaptive method is provided by making different codebook sizes for different classes. Simulation results show that this DCT-CVQ results in good subjective quality at low bit rates, and SNR is increased by about 1.5-4.0 dB in the range 0.2-0.5 bpp, when compared with other DCT-VQ coding schemes.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2013.11a
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• pp.8-11
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• 2013

We implement the foveation and frequency sensitivity feature of human visual system in discrete cosine transform (DCT) domain. Resolution of human visual perception decays as distance from the eye-focused point, known as foveation property, and the middle frequency components give most pleasant image quality to human than the low and high frequency components, which is the frequency sensitivity property of human visual system. For satisfying the foveation property, we enhanced the local contrast at the focused regions and smoothed local contrast at the non-focused regions in the DCT domain without bringing the blocking and ringing artifacts. Moreover, the energies at each DCT frequency components is modified with various degree to fulfill the frequency sensitivity property. The proposed method is verified by the subjective and objective evaluations that it can the improve the human perceptual visual quality.

• Journal of the Korea Society of Computer and Information
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• v.24 no.2
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• pp.41-48
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• 2019

Digital image watermarking techniques have been studied in various fields in order to protect the copyright of multimedia contents mostly composed by images. JPEG compression is a representative copyright attack for image watermarking. The CRT-based watermarking methods in DCT domain have been studied, because these are robust for JPEG compression attack. In this paper, we propose a new method with improved performance compared with the existing CRT based methods in DCT domain. The proposed method selects the DCT block according to the denseness at the watermark insertion phase, and iteratively adjust the CRT Conditional coefficients at the watermark extraction. This paper shows that it is more robust for the JPEG compression attacks through experimental results.