• ETRI Journal
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• v.46 no.3
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• pp.538-549
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• 2024

A conventional codec aims to increase the compression efficiency for transmission and storage while maintaining video quality. However, as the number of platforms using machine vision rapidly increases, a codec that increases the compression efficiency and maintains the accuracy of machine vision tasks must be devised. Hence, the Moving Picture Experts Group created a standardization process for video coding for machines (VCM) to reduce bitrates while maintaining the accuracy of machine vision tasks. In particular, in-loop filters have been developed for improving the subjective quality and machine vision task accuracy. However, the high computational complexity of in-loop filters limits the development of a high-performance VCM architecture. We analyze the effect of an in-loop filter on the VCM performance and propose a suboptimal VCM method based on the selective activation of in-loop filters. The proposed method reduces the computation time for video coding by approximately 5% when using the enhanced compression model and 2% when employing a Versatile Video Coding test model while maintaining the machine vision accuracy and compression efficiency of the VCM architecture.

• Journal of the Korean Society of Radiology
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• v.15 no.3
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• pp.321-327
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• 2021

Wrist PA-grip view is used to diagnose triangular fibrocartilage complex (TFCC) tear because it can easily diagnose damage to the surrounding wrist ligaments. However, despite advances in radiology equipment, distortion of images due to geometric elements still has many limitations. In this paper, we propose a method that can minimize the distortions of images by analyzing the distortions occurring in the wrist PA-grip view. A source of image distance (SID) were set at 130 cm and 150 cm for comparison with 110 cm. Depending on the SID, the phantom of wrist was moved at 0, 2, 4, 6, 8, and 10 cm in the X-axis and Y-axis directions, respectively. For quantitative evaluation, the difference of distance between the radius and ulna was measured in picture archiving and communication system (PACS) system. As a qualitative evaluation, survey was conducted among 20 radiologic technologists who examined the Wrist PA-grip view. The Kruskal Wallis test was performed to compare the distortion according to the phantom movement in the X-axis and Y-axis directions based on the SID, and the Tukey test was performed as a post-test. In the quantitative evaluation results, the measured values obtained in the X-axis was not significantly different in all groups (p>0.05). The measured values obtained in the Y-axis was significantly different in the most groups (p<0.05). Therefore, to reduce distortion while maintaining image quality, we recommend what examine the SID at 150 cm than 110 cm.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.9B
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• pp.1742-1754
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• 1999

In this paper, we propose a rate control scheme, using histogram based rate-distortion (R-D) estimation, which produces a consistent picture quality between consecutive frames. The histogram based R-D estimation used in our rate control scheme offers a closed-form mathematical model that enable us to predict the bits and the distortion generated from an encoded frame at a given quantization parameter (QP) and vice versa. The most attractive feature of the R-D estimation is low complexity of computing the R-D data because its major operation is just to obtain a histogram or weighted histogram of DCT coefficients from an input picture. Furthermore, it is accurate enough to be applied to the practical video coding. Therefore, the proposed rate control scheme using this R-D estimation model is appropriate for the applications requiring low delay and low complexity, and controls the output bit-rate ad quality accurately. Our rate control scheme ensures that the video buffer do not underflow and overflow by satisfying the buffer constraint and, additionally, prevents quality difference between consecutive frames from exceeding certain level by adopting the distortion constraint. In addition, a consistent considering the maximum tolerance BER of the voice service. Also in Rician fading channel of K=6 and K=10, considering CLP=$10^{-3}$ as a criterion, it is observed that the performance improment of about 3.5 dB and 1.5 dB is obtained, respectively, in terms of $E_b$/$N_o$ by employing the concatenated FEC code with pilot symbols.

• Journal of Broadcast Engineering
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• v.25 no.3
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• pp.313-324
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• 2020

In this paper, we propose a motion vector prediction method that increases the coding efficiency at the boundary of an image by utilizing the 360 video characteristic. In the current VVC method, the location of a neighbor block is excluded from the candidate list for inter prediction in case that it is out of boundary. This can reduce coding efficiency as well as subject quality. To solve this problem, we construct new candidates adding the location of the neighbor block at the boundary of the picture from already decoded information based on the projection method for 360 video coding. To evaluate the performance of the proposed method, we compare with VTM6.0 and 360Lib9.1 under Random Access condition of JVET-360 CTC. As a result, the coding performance shows a BD-rate reduction of 0.02% on average in luma component and 0.05%, 0.06% on average in chroma components respectively, without additional computational complexity. The coding performance at the picture boundary shows a BD-rate reduction of 0.29% on average in luma component and 0.45%, 0.43% on average in chroma components, respectively. Furthermore, we perform subjective quality test with the DSCQS method and obtain MOS values. The MOS value is improved by 0.03 value, and we calculate BD-MOS using MOS value and bit-rate. As a result, the proposed method improved performance by up to 8.78% and 5.18% on average.

• Journal of Broadcast Engineering
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• v.13 no.5
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• pp.636-650
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• 2008

DTV has a great advantage as compared to Analog TV in picture quality under low reception field strength. Various high quality tuners have been developed to result in much smaller Noise Figure of the receivers and many trials for receiving DTV signal through indoor antenna. In this paper, results of intensive field tests on the indoor reception of DTV are presented. Tests were carried out around Seoul-Gyeonggi Metropolitan area. Commercial directional and omni-directional antennas and 5th generation receiver were used for reception availability tests. The effects of heights, locations, and types of the house as well as the distance to the transmitter on the reception performances are analyzed. Our test results will be applied to improve the indoor reception environment of DTV.

• Journal of Distribution Research
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• v.16 no.2
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• pp.1-24
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• 2011

1. Introduction: Contrast to the offline purchasing environment, online store cannot offer the sense of touch or direct visual information of its product to the consumers. So the builder of the online shopping mall should provide more concrete and detailed product information(Kim 2008), and Alba (1997) also predicted that the quality of the offered information is determined by the post-purchase consumer satisfaction. In practice, many fashion and apparel online shopping malls offer the picture information with the product on the real person model to enhance the usefulness of product information. On the other virtual product experience has been suggested to the ways of overcoming the online consumers' limited perceptual capability (Jiang & Benbasat 2005). However, the adoption and the facilitation of the virtual reality tools requires high investment and technical specialty compared to the text/picture product information offerings (Shaffer 2006). This could make the entry barrier to the online shopping to the small retailers and sometimes it could be demanding high level of consumers' perceptual efforts. So the expensive technological solution could affects negatively to the consumer decision making processes. Nevertheless, most of the previous research on the online product information provision suggests the VR be the more effective tools. 2. Research Model and Hypothesis: Presented in