Taegeun Oh

No-Reference Sharpness Assessment of Camera-Shaken Images by Analysis of Spectral Structure

The tremendous explosion of image-, video-, and audio-enabled mobile devices, such as tablets and smart-phones in recent years, has led to an associated dramatic increase in the volume of captured and distributed multimedia content. In particular, the number of digital photographs being captured annually is approaching 100 billion in just the U.S. These pictures are increasingly being acquired by inexperienced, casual users under highly diverse conditions leading to a plethora of distortions, including blur induced by camera shake. In order to be able to automatically detect, correct, or cull images impaired by shake-induced blur, it is necessary to develop distortion models specific to and suitable for assessing the sharpness of camera-shaken images. Toward this goal, we have developed a no-reference framework for automatically predicting the perceptual quality of camera-shaken images based on their spectral statistics. Two kinds of features are defined that capture blur induced by camera shake. One is a directional feature, which measures the variation of the image spectrum across orientations. The second feature captures the shape, area, and orientation of the spectral contours of camera shaken images. We demonstrate the performance of an algorithm derived from these features on new and existing databases of images distorted by camera shake.

Dynamic Bandwidth and Carrier Allocation for Video Broadcast/Multicast Over Multi-Cell Environments

Recently, broadcast/multicast over cellular networks has been actively discussed over commercial wireless mobile terminals. Compared to conventional terrestrial or satellite broadcasting systems, the quality-of-service (QoS) for edge users is an important issue due to inter-cell interference over multi-cell environments. In this paper, we introduce a dynamic bandwidth and carrier allocation (DBCA) technique by fully utilizing different visual importance of each layer in multi-layer video for broadcast/multicast services when the number of users is limited over macro/micro/femto cell environments. To ensure an acceptable video quality for edge users, the bandwidth and the loading ratio are dynamically controlled to enhance the utility through the radio resource control in accordance with the visual importance. The simulation results show that DBCA exhibits much better QoS by sending visually more important data with high priority in the cell border region.

Blind Sharpness Prediction Based on Image-Based Motion Blur Analysis

For high bit rate video, it is important to acquire the video contents with high resolution, the quality of which may be degraded due to the motion blur from the movement of an object(s) or the camera. However, conventional sharpness assessments are designed to find focal blur caused either by defocusing or by compression distortion targeted for low bit rates. To overcome this limitation, we present a no-reference framework of a visual sharpness assessment (VSA) for high-resolution video based on the motion and scene classification. In the proposed framework, the accuracy of the sharpness estimation can be improved via pooling weighted by the visual perception from the object and camera movements and by the strong influence from the region with the highest sharpness. Based on the motion blur characteristics, the variance and the contrast over the spectral domain are used to quantify the perceived sharpness. Moreover, for the VSA, we extract the highly influential sharper regions and emphasize them by utilizing the scene adaptive pooling. Based on the subjective results, we demonstrate that the VSA can measure the video sharpness more accurately than other sharpness measurements for high-resolution video.

Macroblock-Based Frequency Selective Weighting for Visual Scalable Video Coding of H.264/AVC

In this paper, a novel macroblock-based frequency selective weighting scalable video coding (MBFSW-SVC) algorithm is investigated by exploring the characteristics of the human visual system (HVS) in SVC H.264/AVC for improving the coding efficiency. Compared with previous SVC schemes, the MBFSW-SVC can extend the quality layer with different frequency weighting for each MB according to the size of region of interests. For reasonable adaptation of the frequency weighting into the quality layer extension, the spatial context characteristics and the motion activities in each picture are taken into account. The experiment results show that the proposed scheme can improve the coding performance up to a 10-20% reduction of the bit rate with almost the same subjective video quality. In particular, the subjective quality is significantly improved in lower scalable quality layers with a small number of the encoding bit budget.

Cooperative and joint video multicast over MIMO–OFDM networks

Abstract Systems that broadcast/multicast over cellular networks have recently been intensively investigated. When compared to conventional terrestrial or satellite broadcasting systems, the Quality of Service (QoS) experienced by edge users is an important issue due to the inevitable inter-cell interference (ICI) that occurs within multi-cell environments. In order to resolve this issue, we have developed cooperative sub-band allocation (CSA) and CSA-joint transmission (CSA-JT) techniques that operate as a function of defined visual importance levels assigned to multi-layer videos, where the number of service users is limited over the macro/micro cell environment. To ensure that an acceptable level of video quality is delivered to edge users, an adaptive sub-band allocation scheme for layered video is designed to enhance the overall experience for all users based on maintaining program fairness. In a multiple-input/multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) system, CSA can effectively mitigate ICI at the cell border via base station (BS) cooperation. Moreover, CSA-JT can improve the QoS for cell border users via joint transmission among the cooperating BSs. In order to achieve the delivery of optimal visual quality, an optimization problem is formulated that seeks to maximize the sum experience of the multicast users. A dual decomposition technique is applied in order to reduce the computational complexity of the system. Simulation results show that the CSA and CSA-JT algorithms exhibit a remarkable reduction of outage probability.

Optimal power allocation for minimizing visual distortion over MIMO communication systems

A recent dynamic increase in demand for wireless multimedia services has greatly accelerated the research on cross layer optimization techniques for transmitting multimedia data over wireless channel. In this paper, we explore a novel theoretical approach for joint optimization between the rate distortion (RD) of H.264/AVC video and the link-capacity of MIMO parallel subchannels. We obtain the optimal power level of subchannels through an optimization problem to minimize total visual distortion. In the simulation results, compared to the water filling (WF) method, the proposed scheme provides better results in aspects of visual quality in the face of sum rate loss.

Low-complexity and robust comic fingerprint method for comic identification

Copyright infringement has emerged as a significant issue in the growth of the e-book/comics market on account of illegal copying and distribution. It is therefore important to develop automated comic book identification techniques to prevent such problems. Fingerprinting methods have been typically used for multimedia identification; however previous fingerprinting methods are unsuitable for the identification of comic books, which may include several types of distortions, including geometric changes. In this paper, a new comic fingerprinting method is proposed based on a comparison of the average pixel intensity of sub-images, which are called pairwise patterns. In particular, for robust identification against such geometric distortions, circular patterns are newly proposed and evaluated after constructing a comic fingerprint database. The intra- and inter-distances of the features in a fingerprint are calculated to demonstrate its pairwise independence and robustness against various distortions. The result shows that the proposed fingerprinting method is more robust against various distortions, especially for rotational distortion, than those in previous methods. Moreover, owing to its low complexity, the method has potential advantages for commercial applications in real-time.11This research project was supported by Ministry of Culture, Sports and Tourism (MCST) and from Korea Copyright Commission in 2015. (2013-book_scan-9500). Display Omitted The additional circular fingerprint patterns robust to the rotational distortions.Reduced fingerprint bits (32 bits) compared to the previous one (38 bits).The unique fingerprint of 352 bits for the comic identification.

Network-based content identification system via content-based comics fingerprint

Recently, the comic contents are widely spread due to the development of mobile devices and network-based distribution. Large-scale data of contents increases the work load of network, so that it is necessary to manage effectively these contents distribution via content identifiers. However, the illegal channels such as online storage service provide the comics without the identifier. In addition, these comics would violate the copyright. To prevent the copyright violation, the comic identification is very important. However, the comic identification is the beginning stage. Thus, we propose a novel content-based fingerprint for comic content. To reduce work load of network, the fingerprint are extracted in consumers device with low computational complexity. The proposed method shows the reliable performance with the robustness and the efficiency for distorted comics identification.

Ego motion induced visual discomfort of stereoscopic video

When each video sequence is captured, an inappropriate camera motion should be one of crucial factors leading to visual discomfort and distortion. The well known symptom, visually induced motion sickness (VIMS) is caused by the illusion of self motion by perceiving the video with ego motion. In particular, for the stereoscopic 3D video, it can be easily observed that the viewers have dominantly feel much more severe symptoms of visual discomfort. In this paper, we analyze the ego motion of the stereoscopic video and predict the effects. We attempt a novel approach by exploiting the computer vision algorithm. We propose a novel method which can estimate the perceptual 3D ego motion from the stereoscopic video. Then we analyze the ego motion components to predict the visual discomfort of stereoscopic video.

Link Capacity Improvement by Utilizing Overlaid Bandwidth and Region Division

A cell planning and resource allocation scheme for improving channel capacity and for maintaining QoS (quality of service) over a downlink OFDMA (Orthogonal Frequency Division Multiple Access) system is proposed. The frequency overlay is applied to improve link capacity and the sectorization is reduce the influence of carrier collision. This consideration enhances link capacity of system with a proper outage probability.