• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.10C
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• pp.950-958
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• 2007

This paper presents an efficient packet loss resilient scheme for real-time video transmission over the Internet. By analyzing the temporal and spatial dependencies in inter- and intra-frames, we assign forward error correction codes (FEC) across video packets for minimizing the effect of error concealment and error propagation from packet loss. To achieve optimal allocation of FEC codes, we formulate the effect of packet loss on video quality degradation as packet distortion model. Then we propose an unequal FEC assignment scheme with low complexity based on packet correction rate, which uses the packet distortion model and includes channel status information. Simulation results show that the proposed FEC assignment scheme gives substantial improvement for the received video quality in packet lossy networks. Furthermore the proposed scheme achieves relatively smaller degradation of video quality with higher packet loss rates.

• Journal of the Korean Institute of Intelligent Systems
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• v.19 no.6
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• pp.787-795
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• 2009

This paper presents a histogram equalization based on the logistic function for enhancing the quality of images. The histogram equalization is a simple and effective spatial processing method that it enhances the quality by adjusting the brightness of image. The logistic function that is a nonlinear transformation function is applied to adaptively enhance the brightness of the image according to its intensity level frequency. We propose a flexible and asymmetrical logistic function by only using the intensity level with maximum frequency and the maximum intensity level in an histogram, and the total number of pixels. The proposed function excludes both the computation load of an exponential function and the heuristic setting of an optimal parameter values in the traditional logistic function. The proposed method has been applied for equalizing many images with a different resolution and histogram distribution. The experimental results show that the proposed method has the superior enhancement performances and the faster equalizing speed compared with the traditional histogram equalization and the adaptively modified histogram equalization, respectively. And the proposed histogram equalization can be used in various multimedia systems in real-time.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37A no.9
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• pp.786-791
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• 2012

This paper presents a depth boundary sharpening method for improved view synthesis in 3D video. In depth coding, distortion occurs around object boundaries, degrading the quality of synthesized images. In order to encounter this problem, the proposed method estimates an edge map for each frame to filter only the boundary regions. In particular, a window-based filter is employed to choose the most reliable pixel as the replacement considering three factors: frequency, similarity and closeness. The proposed method was implemented as post-processing of the deblocking filter in JMVC 8.3.Compared to the conventional methods, the proposed method generated 0.49 dB PSNR increase and 16.58% bitrate decrease on average. The improved portions were subjectively confirmed as well.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.12
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• pp.2783-2797
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• 1997

This paper proposes a new motion estimation algorithm that employs matching in a variable search area. Instead of uisg a fixed search range for coarse motion estimation, we examine a varying search range, which is determined adaptively by the peak signal to noise ratio (PSNR) of the frame difference. The hexagonal matching method is one of the refined methods in image warping. It produces improved image quality, but it requires a large amount of computataions. The proposed adaptive partial matching method reduces computational complexity below about 50% of the hexagonal matching method, while maintaining the image quality comparable. The performance of two motion compensation methods, which combine the affine or bilinear transformation with the proposed motion estimation algorithm, is evaluated based on the following criteria:computtational complexity, number of coding bits, and reconstructed image quality. The quality of reconstructed images by the proposed method is substantially improved relative to the conventional BMA method, and is comparable to the full hexagonal matching method;in addition, computational complexity and the number of coding bits are reduced significantly.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.7
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• pp.100-106
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• 2015

In this paper, we propose a fast algorithm for low-power image enhancement method for mobile LCD. In the proposed fast algorithm, the spatial resolution of the input image is significantly reduced, and the image characteristics are analyzed on the reduced resolution image to find a dimming rate adaptive to the image content, thereby saving power. The proposed fast adaptive dimming and image enhancement algorithm is implemented as an application that runs on an Android device. Image quality evaluation and running time analysis experiments on the device indicate that the proposed fast algorithm jointly minimizes the quality degradation and power consumption, reducing the required computation load by over 95%.

• Journal of the Institute of Convergence Signal Processing
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• v.21 no.2
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• pp.92-100
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• 2020

Currently, the demand for underwater or underwater photography is growing very fast. Its coverage of underwater shooting for broadcasting, leisure and sports, and military and operational use is also growing rapidly. Among them, we specifically select the best camera to be used in underwater drones to photograph and inspect marine life attached to the ship's hull. To compare three cameras performance, they are compared and evaluated using objective and subjective criteria in special circumstances such as underwater shooting. This study checks whether performance criteria, such as resolution of a camera, meet objective and subjective standards in the unusual situation of underwater shooting. And it shows that in addition to the filter that calibrates the image, proper camera selection is important for providing good picture quality. Even after this study, research using more diverse cameras could provide an appropriate standard for comparison of underwater camera quality.

• Information and Communications Magazine
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• v.30 no.7
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• pp.50-57
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• 2013

망관리성이란 다수의 이용자가 네트워크를 효율적으로 이용할 수 있도록 하기 위해 통신사업자가 네트워크를 합리적으로 관리할 수 있어야 한다는 것을 의미한다. 본고에서는 최근 증가하고 있는 대용량 비디오 트래픽에 대한 최적의 이용환경을 제공하고 망관리성을 제고하는 방안으로서 비디오 트래픽 대역폭 최적화 동향을 살펴보고 향후 방향을 제시하고자 한다. 비디오 트래픽 대역폭 최적화란 네트워크(3G/ LTE 등), 단말(휴대폰/태블릿 등), 콘텐츠(스포츠/드라마/영화 등) 유형별로 이용자의 동영상 품질 만족도와 네트워크 품질을 동시에 만족하는 최적 대역폭(비트레이트)의 비디오 트래픽을 전송하는 것이다. 비디오 트래픽 최적화에 있어서 최적대역폭 선정 기준의 정립은 다음과 같은 두 가지의 연구 결과를 기반으로 진행된다. 첫째, 일반적으로 동영상 대역폭이 증가할수록 영상 품질도 정비례로 증가할 것이라는 예상과는 달리, 무선 단말 이용자는 영상화질의 일정 임계치 이상에서 품질의 차이를 거의 느낄 수 없다. 둘째, 다량의 비디오 트래픽이 네트워크 총 대역폭의 일정 비율 이상을 차지하게 될 경우 네트워크 품질저하 요소가 발생하여 네트워크 품질이 급격히 악화된다. 비디오 트래픽 최적화는 이러한 요소를 고려하여 이용자의 영상 품질 만족도를 최대화하면서 네트워크 품질 유지비용을 최소화하고 트래픽 전송품질을 확보할 수 있는 최적대역폭을 설정하는 것이다. 비디오 트래픽 최적화의 목적은 트래픽을 통제하거나 차단하는 것이 아니며 최적대역폭에 대한 가이드라인을 제시하여 콘텐츠사업자(이하 CP)와 Over-The-Top 사업자(이하 OTT)가 자발적으로 준수하도록 유도하고자 하는 것이다. 비디오 트래픽 최적화는 ICT생태계 모든 이해관계자에게 편익을 제고할 것으로 기대된다. 첫째, 이용자에 대해서는 통신품질 안정화로 전체적인 이용자 만족도를 향상시킨다. 둘째, CP/OTT는 멀티미디어 서비스의 대중화와 서버 및 전송장비 비용을 절감할 수 있다. 마지막으로 통신사는 네트워크 품질저하 및 비용 급증을 방지할 수 있다.

• The Journal of the Korea Contents Association
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• v.12 no.4
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• pp.367-372
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• 2012

The aim of this study was to assess the effect of exposure factors such as kVp and mA applied by BMI on the image quality and patients absorbed dose of Coronary angiography in CT. Each data sets were into 4groups with different exposure values : Group A at 100kVp, 240mAs, Group B at 120kVp, 240mAs, Group C at 100kVp, 270mAs and Group D at 120kVp, 270mAs, and the mean of the scores of 4 groups was calculated for image quality as 4grades that is, 1(poor), 2(fair), 3(good) and 4(very good). Patient absorbed dose was calculated as DLP on the monitor. In case of absorbed dose, deviation in 2groups at 100kVp was 5.6 $mGy{\cdot}cm$, 11 $mGy{\cdot}cm$, was at 120kVp(DLP) with p<0.05. There was rather difference between groups with 100kVp or 120kVp respectively but the gaps were very little. No significant correlation was found between exposure factors and image quality in any images assessed(p>0.05), and the image quality was sufficient for diagnosis. As we applying coronary angiography, the selection of adequate exposure factors considering BMI identified might be effective for reduction of patient absorbed dose, improvement of image quality and diagnostic accuracy.

• Science of Emotion and Sensibility
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• v.13 no.1
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• pp.251-258
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• 2010

'Naturalness' is the important "ness" which is a key factor in image quality assessment. 'Naturalness' is a representive factor depending on the context of the image which arouses different emotions. The Image Quality Circle was split into two steps. The first step is predicting the visual perceptual attribute which are lightness, colourfulness, hue and contrast. The next step is SSE which is dependent to image contents. In this study the image contents are grouped in genres. The images were rendered using four different colour attributes which are lightness, contrast, colourfulness and hue. Using a scale, the score of image quality and SSE was asked to each participant for all rendered images. A seven-point category scale of increasing amount of "ness" is used as a quantitative adjectives sequence. The image quality model was built by combining the SSEs for each scene. The SSEs, where vividness is common, are considered as independent variables to predict the image quality score. Then the vividness model was built using colour attributes as variables to predict the vividness of each scene (genre). Vividness is an important factor of naturalness which the meaning is different for all scenes that links the naturalness and image quality. The vividness meaning was different for each scene (genre). Therefore, the colour attributes that express the vividness would depend on the image content.

• The Journal of the Korea Contents Association
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• v.13 no.1
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• pp.9-18
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• 2013

In order to measure the parameters of consumers' preferred image quality, this research suggests image quality assessment factors; dynamic range, color, and contrast. They have both physical image quality factors and psychological characteristics from the previous researches. We found out the specific ranges of preferred image quality metrics. As a result, Digital Zone System meant for dynamic range generally shows 6~10 stop ranges in portrait, nightscape, and landscape. Total RGB mean values represent in portrait (67.2~215.2), nightscape (46~142), and landscape (52~185). Portrait total RGB averages have the widest range, landscape, and nightscape, respectively. Total scene contrast ranges show in portrait (196~589), nightscape (131~575), and landscape (104~767). Especially in portrait, skin tone RGB mean values are in ZONE V as the exposure standard, but practically image consumers' preferred skin tone level is in ZONE IV. Also, total scene versus main subject contrast ratio represents 1:1.2; therefore, we conclude that image consumers prefer the out-of-focus effect in portrait. Throughout this research, we can measure the preferred image quality metrics ranges. Also, we expect the practical and specific dynamic range, color, and contrast information of preferred image quality to positively influence product development.