• Journal of the Korean Institute of Telematics and Electronics S
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• v.36S no.7
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• pp.116-123
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• 1999

of a block if the method uses the quantization parameter depending on the bitrate control, and consequently it influence the image quality of video. In this paper, we propose a new method using the following three steps : calculating an averaging (Average of Sum, AS) value in each pixel's block of images, earning an average value of differences between each pixels and As (Differential Averaging Block Pixels, DABP), and finally achieving an improved coefficient values by the DABP and DCT coefficients. Simulation results show that the quality of moving picture could be improved by the proposed method.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.1
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• pp.81-86
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• 2011

Watermarking is one of the methods that insist on a copyright as it append digital signals in digital informations.(image, video, ets) In this paper, we proposed a digital watermarking algorithm which improved Gradient of DCT Coefficient. This method targets MPEG-2 TM5 system and watermarking process is to be performed during Quantization DCT. Watermark was inserted on Y components of each frames. The PSNR difference between the compressed images with and without watermarking was only 0..23dB. In each case that the resulting image was reusable the normalized correlation between the extracted watermark and the original one was above 0.99.

• Journal of KIISE
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• v.42 no.2
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• pp.162-168
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• 2015

Image data is mostly stored in compressed form because of its huge size. Therefore, a series of cumbersome procedures is required to apply a transformation to image data: decompression, extraction of spatial data, transformation and recompression. In this paper, we employ DCT(Discrete Cosine Transform) coefficients to change the spatial presentation of images. DCT is commonly used in still image compression standards such as JPEG and moving picture compression standards such as MPEG-2, MPEG-4, and H.264. In this paper, we derived mathematically the relationship between the geometry transformation in the spatial domain and coefficient changes in the DCT domain and verified it with images in the JPEG file format. Because of the efficiency of transformation in the frequency domain, our findings can be utilized for light-weight partial image encryption for privacy data protection or entertainment contents protection.

• Journal of Broadcast Engineering
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• v.10 no.3
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• pp.413-421
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• 2005

As the population of HDTV is growing, among many useful features of modern set top boxes (STBs) or digital video recorders (DVRs), video browsing, visual bookmark, and picture-in-picture capabilities are very frequently required. These features typically employ reduced-size versions of video frames, or thumbnail images. Most thumbnail generation approaches generate DC images directly from a compressed video stream. A discrete cosine transform (DCT) coefficient for which the frequency is zero in both dimensions in a compressed block is called a DC coefficient and is simply used to construct a DC image. If a block has been encoded with field DCT, a few AC coefficients are needed to generate the DC image in addition to a DC coefficient. However, the bit length of a codeword coded with variable length coding (VLC) cannot be determined until the previous VLC codeword has been decoded, thus it is required that all codewords should be fully decoded regardless of their necessary for DC image generation. In this paper, we propose a method especially for fast DC image generation from an I-frame using multiple-symbol lookup table (mLUT). The experimental results show that the method using the mLUT improves the performance greatly by reducing LUT count by 50$\%$.

• Journal of Broadcast Engineering
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• v.6 no.2
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• pp.187-194
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• 2001

The Advanced Intra Coding(AIC) mode included in the H.263+ which is for video ceding at low bit rates, selects one prediction direction of DCT coefficients among three directions for every intra macroblock. Based ()n the selected direction, It uses a different DCT scanning order, quantization scheme, and VLC table. The use of the AIC mode brings higher compression ratio and improved PSNR than the H.263 baseline. This paper proposes a simplified submode selection method for a direction of the DCT coefficient prediction for advanced ultra coding in H.263. Compared to the conventional method the proposed simplified method can achieve a similar coding Performance at computational complexity reduced to 1/7 and with much less memory requirement. The proposed method will be useful in implementing a simplified H.263 system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.9C
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• pp.1258-1268
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• 2004

We propose a new fast, algorithm which is used for detecting frontal face in the frequency domain based on human skin-color using OCT coefficient of dynamic image compression and skin color information. The region where each pixel has a value of skin-color were extracted from U and V value based on DCT coefficient obtained in the process of Image compression using skin-color map in the Y, U, V color space A morphological filter and labeling method are used to eliminate noise in the resulting image We propose the algorithm to detect fastly human face that estimate the directional feature and variance of luminance block of human skin-color Then Extraction of face was completed adaptively on both background have the object analogous to skin-color and background is simple in the proposed algorithm The performance of face detection algorithm is illustrated by some simulation results earned out on various races We confined that a success rate of 94 % was achieved from the experimental results.

• Journal of the Korea Society of Computer and Information
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• v.16 no.7
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• pp.59-65
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• 2011

Korea DMB Service is popularized, and is used by many users. But latest display devices compared to the DMB content resolution support higher resolution and a variety of video resampling technologies has been used. Generally, subjective video quality is determined by object recognition rate in video, and increased as the edge space between objects are more clear. An edge is the boundary between an object and the background, and indicates the boundary between overlapping objects. the predicted direction in intra prediction used in H.264/AVC has the similarity up to 80% for the edge information. In the study, we propose an effective up-sampling mothed using the edge information that is extracted for the relationship between the intra prediction data and the DCT coefficient data of H.264 video encoding.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.4
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• pp.1790-1806
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• 2016

Digital image encryption is widely used for image data security. JPEG standard compresses image with great performance on reducing file size. Thus, to encrypt an image in JPEG format we should keep the quality of original image and reduced size. This paper proposes a JPEG image encryption scheme based on quantized DC and non-zero AC coefficients inner category scrambling. Instead of coefficient value encryption, the address of coefficient is encrypted to get the address of cipher text. Then 8*8 blocks are shuffled. Chaotic iteration is employed to generate chaotic sequences for address scrambling and block shuffling. Analysis of simulation shows the proposed scheme is resistant to common attacks. Moreover, the proposed method keeps the file size of the encrypted image in an acceptable range compared with the plain text. To enlarge the cipher text possible space and improve the resistance to sophisticated attacks, several additional procedures are further developed. Contrast experiments verify these procedures can refine the proposed scheme and achieve significant improvements.

• Proceedings of the Korea Multimedia Society Conference
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• 2002.11b
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• pp.254-258
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• 2002

멀티미디어의 내용 기반 검색을 위한 표준인 MPEG-7은 컨텐츠의 비주얼 내용 정보를 표현하기 위해 Part3에서 비주얼 기술자를 정의하고 있다. MPEG-7 비주얼 컬러 기술자에 의해 정의된 컨텐츠의 컬러 정보를 추출하기 위해서는 주파수 영역 정보를 공간 영역 정보로 변환해야 한다. 이때 변환 과정에서 수행되는 IDCT(Inverse DCT)의 연산 속도는 특징 추출 시간을 증가시키는 원인이 된다. 본 논문에서는 IDCT의 연산 시간을 최소화하는 방법으로 DCT 계수 영역에서 컬러 특징 정보를 빠르게 추출하는 방법에 대해 제안하였다. 제안한 방법에 대해 MPEG-7 실험 모듈과 공인 데이터 베이스를 이용하여 실험을 수행하였고 실험 결과, 검색 율이 평균 5% 감소한 반면 추출 시간은 평균 80% 향상되었다.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.527-528
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• 2006

In this paper, we propose an IP design and implementation of System on a chip(SoC) for Discrete Cosine Transform (DCT) and Discrete Wavelet Transform (DWT) processor using adder-based DA(Adder-based Distributed Arithmetic). To reduced hardware cost and to improve operating speed, the combined DCT/ DWT processor used the bit-serial method and DA module. The transform of coefficient equation result in reduction in hardware cost and has a regularity in implementation. We use Verilog-HDL and Xilinx ISE for simulation and implement FPGA on SoCMaster-3.