• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.10a
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• pp.105-108
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• 2003

In the framework of universal multimedia access, one challenge for video transmission (communication) is to deliver video content through heterogeneous network channels matching the diversity of client devices. As one of the many adaptation methods, media transcoding is commonly considered. Particularly, FD (Frame Dropping)/CD Coefficient Dropping) transcoding is used due to the low computational complexity and simple implementation. In this scheme, CD is simply implemented by truncating the high frequency AC DCT coefficient bits. But, the CD error tends to be propagated within single GOV. In this paper, we derive the distortion relationships between CD error and propagation error, and investigate the error characteristics by computer simulations. The CD error characteristics can be effectively used in the FD/CD transcoding scheme.

• Korean Journal of Cognitive Science
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• v.11 no.2
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• pp.79-87
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• 2000

In this paper we present a face recognition and face detection algorithm in MPEG compressed video. The proposed method consists three stage of processing steps. The first step is to produce a spatially reduced DC image form MPEG compressed video for processing. And the second step is face detection on reduced DC image. Finally, the last step is face recognition on partially extracted compressed frames which contain the detected faces. The spatially reduced DC image is produced from two dimensional inverse DCT of the DC coefficient and the first two AC coefficients. The face detection is performed on DC image and face recognition is performed on one extracted frame per GOP by using the K-L transform. In order to evaluate the proposed method, we carried out experiments on video database. The experiment results show the proposed method is very efficient and helpful for target tasks.

• Journal of the Korean Institute of Intelligent Systems
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• v.24 no.1
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• pp.22-27
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• 2014

Blocking and ringing artifacts continue to be the most serious defects that occur in images and video streams compressed to low bit rates using block-based discrete cosine transform(DCT) compression standards. These artifacts contain the high frequency components near the block and the edge boundaries. Usually the lowpass filter can remove them. However, simple lowpass filter results into blur by removing important information such as edges at the same time. To overcome these problems, we propose a novel postfiltering algorithm that calculate the weight value based on the intensity similarity in the neighboring pixels and multiply this weight to the Gaussian lowpass filter coefficient. Experimental results show that the proposed technique provides satisfactory performance in both objective and subjective image quality.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.625-629
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• 2005

According to the rapid development of the information and communication technology, the demand on the efficient compression technology for the multimedia data is increased magnificently. In this Paper, we designed new compression algorithm structure using wavelet base for the compression of ECG signal and audible signal data. We examined the efficiency of the compression between 2-band structure and wavelet packet structure, and investigated the efficiency and reconstruction error by wavelet base function using Daubechies wavelet coefficient and Coiflet coefficient for each structure. Finally, data were compressed further more using Huffman code, and resultant Compression Rate(CR) and Percent Root Mean Square difference(PRD) were compared with those of existent DCT.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.5
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• pp.685-694
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• 1993

A progressive image transmission (PIT) scheme based on the classified transform vector quantization (CVQ) technique using the lapped orthogonal transform (LOT) and human visual system (HVS) weighting is proposed in this paper. Conventional block transform coding of images using DCT produces in general undesirable block-artifacts at low bit rates. In this paper, image blocks are transformed using the LOT and classified into four classes based on their structural properties and further divided adaptively into subvectors depending on the LOT coefficient statistics with HVS weighting to improve the reconstructed image quality by adaptive bit allocation. The subvectors are vector quantized and transmitted progressively. Coding tests using computer simulations show that the LOT/CVQ based PIT of images is a effective coding scheme. The results are also compared with those obtained using PIT/DCTVQ. The LOT/CVQ based PIT reduces the block-artifacts significantly.

• Proceedings of the IEEK Conference
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• 2002.07b
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• pp.1228-1231
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• 2002

Digital image watermarking scheme using adaptive block division is proposed. To increase the perceptual invisibility, the image is divided into blocks by local properties and the human visual system (HVS), then the significant blocks are selected in the divided blocks. The significant coefficient is determined by Weber's law in these blocks. To increase the robustness, low frequency domains of the discrete cosine transform (DCT) and the discrete wavelet transform (DWT) are used. The watermark is embedded into the selected significant blocks of the DCT's and DWT's low frequency domains with adaptive watermark strengths. The watermark strength is determined by the variance and the local properties of the significant block. The experimental results prove that the proposed scheme has a good robustness against several image processing operations (e.g. median filtering, cropping, scaling, JPEG, JPEG2000, etc.) without significant degradation of the watermarked image.

• Journal of Korea Multimedia Society
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• v.4 no.6
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• pp.500-509
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• 2001

Image compression based on Wavelet gives much better quality than JPEG based on DCT, but suffers from ringing or blurring effects around edges as the compression is increased. In this paper, we proposed enhanced image compression by pre-processing wavelet coefficients. This pre-processing is performed by making a low threshold and enhanced by zerotree scan method when subband's zerotrees are established. It might increase significants coefficient by means of modifying the threshold and reflect on the orientation of subbands. Some experimental results show our method is more efficient than the conventional methods, JPEG. And then the developed coding scheme improves the quality of images and visually shows more pleasing results for most practical images.

• The Journal of the Acoustical Society of Korea
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• v.24 no.8
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• pp.492-497
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• 2005

In this paper, we suggest that the new volume of robust audio watermarking method protects form the MP3 compression attack, mostly used in audio field. Watermarks were inserted at the coefficients repeatedly from low frequencies to high frequencies after DCT transform in commonly used Cox's spread spectrum method. However, our method could be investigated losing frequency when MP3 attacks and make order by small amount of losing frequency and then insert watermarks rightly through statistical analysis. In the result about various sound clips, the suggested method have better performances than Cox's method by preserving watermarks and reducing distortions of the original sounds.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.2
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• pp.31-37
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• 2015

The security of the image information is very important in many areas of the IoT(Internet of Things), and study a number of ways to display the security (copyright, etc.). In this paper, information of image that is used by the IoT is converted to a DCT(Discrete Cosine Transform) and QC(Quantization Coefficient). And watermark (message) is to create a new encoded message(WMQR) through a QR Code. QC and WMQR applies LSB steganography techniques, can get the security (copyright, etc.) of image information. LSB steganographic techniques may be inserted according to a message (Watermark) to determine the location (Secret Key). The encoded image is sent to the recipient via the Internet. The reverse process can be obtained image and a QR code, a watermark (Message). A method for extracting a watermark from the security of the image information is coded using only the image and Secret Key, through the DCT and quantization process, so obtained by separating the watermark (Message) for the image. In this paper, we were able to improve the security of the method of image information, the image quality of the image by the simulations (PSNR), in turn, benefits were also normalized correlation (NC) and security.

• Journal of Institute of Control, Robotics and Systems
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• v.11 no.5
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• pp.471-475
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• 2005

Recently, development of digital technology is occupying a large part of multimedia information like character, voice, image, video, etc. Research about video indexing and retrieval progresses especially in research relative to video. This paper proposes the novel notation in order to retrieve MPEG video in the international standards of moving picture encoding For realizing the retrieval-system, we detect DCT DC coefficient, and then we obtain shot to apply MVC(Mean Value Comparative) notation to image constructed DC coefficient. We choose the key frame for start-frame of a shot, and we have the codebook index generating it using feature of DC image and applying PCA(principal Component Analysis) to the key frame. Also, we realize the retrieval-system through similarity after indexing. We could reduce error detection due to distinguish shot from conventional shot detection algorithm. In the mean time, speed of indexing is faster by PCA due to perform it in the compressed domain, and it has an advantage which is to generate codebook due to use statistical features. Finally, we could realize efficient retrieval-system using MVC and PCA to shot detection and indexing which is important step of retrieval-system, and we using retrieval-system over the internet.