• Journal of Broadcast Engineering
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• v.14 no.2
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• pp.164-177
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• 2009

The DIBR(depth image-based rendering) method gives the sense of depth to viewers by using one color image and corresponding depth image. At this time, the qualities of the generated left- and right-image depend on the baseline distance of the virtual cameras corresponding to the view of the generated left- and right-image. In this paper, we present a novel method for enhancing the sense of depth by adjusting baseline distance of virtual cameras. Geometric analysis shows that the sense of depth is better in accordance with the increasing disparity due to the reduction of the image distortion. However, the entailed image degradation is not considered. Experimental results show that there is maximum bound in the disparity increasement due to image degradation and the visual field. Since the image degradation is reduced for increasing that bound, we add a depth map preprocessing. Since the interactive service where the disparity and view position are controlled by viewers can also be provided, the proposed method can be applied to the mobile broadcasting system such as DMB as well as 3DTV system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37A no.11
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• pp.918-926
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• 2012

In 3D video transmission, a depth map being used for depth image based rendering (DIBR) is generally compressed by reducing resolution for coding efficiency. Errors in resolution reduction are recovered by an appropriate up-sampling method after decoding. However, most previous works only focus on up-sampling techniques to reduce errors. In this paper, we propose a novel down-sampling technique of depth map that applies different down-sampling rates on moving objects and background in order to enhance human perceptual quality. Experimental results demonstrate that the proposed scheme provides both higher visual quality and peak signal-to-noise ratio (PSNR). Also, our method is compatible with other up-sampling techniques.

• Journal of Broadcast Engineering
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• v.16 no.1
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• pp.44-53
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• 2011

In this paper, we propose a 3D conversion algorithm of 2D video using depth layer partition method. In the proposed algorithm, we first set frame groups using cut detection algorithm. Each divided frame groups will reduce the possibility of error propagation in the process of motion estimation. Depth image generation is the core technique in 2D/3D conversion algorithm. Therefore, we use two depth map generation algorithms. In the first, segmentation and motion information are used, and in the other, edge directional histogram is used. After applying depth layer partition algorithm which separates objects(foreground) and the background from the original image, the extracted two depth maps are properly merged. Through experiments, we verify that the proposed algorithm generates reliable depth map and good conversion results.

• Journal of Broadcast Engineering
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• v.16 no.4
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• pp.584-595
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• 2011

Recently, RGB images and depth maps have been supplied to academic fields. The depth maps are utilized to the generation of stereoscopic images in the diverse formats according to the users' preference. A variety of methods that use depth maps have been introduced so far. One of applications is a medical field. In this area, the improvement of the perceptual quality of 2D medical images has gained much interest. In this paper, we propose a novel scheme that expands the conventional method to 3D stereoscopic image, thereby achieving the perceptual depth quality improvement as well as 3D stereoscopic perception enhancement at the same time. For this, contrast transformation as well as depth darkening are proposed and their performance is validated through the subjective test. Subjective experiments peformed for stereoscopic enhancement as well as visual fatigue validate that the proposed method achieves better 3D perception than the usage of the original stereoscopic image and suggests the limitation in terms of the visual fatigue.

• 한국HCI학회:학술대회논문집
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• 2007.02c
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• pp.170-175
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• 2007

영상 재투영이란, 깊이 맵을 투영하여 임의의 시점에서 본 이미지를 생성해내는 기법을 말한다. 기존의 CPU를 이용한 영상 재투영 기법들의 가장 큰 단점은 CPU와 GPU 간의 데이터 복사가 일어나고 재투영 연산 자체의 속도가 느리기 때문에 실시간 렌더링이 불가능 하다는 것이다. 따라서 본 논문에서는 GPU를 이용하여 영상 재투영을 구현하고 실시간에 이미지를 렌더링하는 기법을 소개한다. 우리의 기법은 입력으로 참조 이미지와 해당 이미지의 깊이 맵이 주어졌을 때, 임의의 시점에서 보이는 새로운 이미지를 실시간으로 생성한다. 임의의 시점에서 이미지를 생성하기 위해, 각 픽셀에서 참조 이미지에 해당하는 평면을 렌더링하여 시점 반대 방향의 광선을 생성한다. 이 광선을 참조 이미지의 투영 공간으로 변환한 후, 광선과 깊이 맵간의 교차점을 찾는다. 이렇게 찾아낸 깊이 맵의 교차점과 일치하는 참조 이미지의 픽셀 색으로 새로운 시점의 이미지를 만들어 낼 수 있다. 이와 같은 기법은 기하 정보의 복잡도와 관계없이 수십 프레임의 속도로 실시간 렌더링이 가능하다.

• Journal of Broadcast Engineering
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• v.19 no.3
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• pp.362-371
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• 2014

Blur variation caused by camera de-focusing provides a proper cue for depth estimation. Depth from Defocus (DFD) technique calculates the blur amount present in an image considering that blur amount is directly related to scene depth. Conventional DFD methods use two defocused images that might yield the low quality of an estimated depth map as well as a reconstructed infocused image. To solve this, a new DFD methodology based on infocused and defocused images is proposed in this paper. In the proposed method, the outcome of Subbaro's DFD is combined with a novel edge blur estimation method so that improved blur estimation can be achieved. In addition, a saliency map mitigates the ill-posed problem of blur estimation in the region with low intensity variation. For validating the feasibility of the proposed method, twenty image sets of infocused and defocused images with 2K FHD resolution were acquired from a camera with a focus control in the experiments. 3D stereoscopic image generated by an estimated depth map and an input infocused image could deliver the satisfactory 3D perception in terms of spatial depth perception of scene objects.

• Journal of Broadcast Engineering
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• v.19 no.1
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• pp.31-43
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• 2014

A depth map is an important component for stereoscopic image generation. Since the depth map acquired from a depth camera has a low resolution, upsamling a low-resolution depth map to a high-resolution one has been studied past decades. Upsampling methods are evaluated by objective evaluation tools such as PSNR, Sharpness Degree, Blur Metric. As well, the subjective quality is compared using virtual views generated by DIBR (depth image based rendering). However, works on the analysis of the relation between depth map upsampling and stereoscopic images are relatively few. In this paper, we investigate the relationship between subjective evaluation of stereoscopic images and objective performance of upsampling methods using cross correlation and linear regression. Experimental results demonstrate that the correlation of edge PSNR and visual fatigue is the highest and the blur metric has lowest correlation. Further, from the linear regression, we found relative weights of objective measurements. Further we introduce a formulae that can estimate 3D performance of conventional or new upsampling methods.

• Proceedings of the Korean Information Science Society Conference
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• 2007.10c
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• pp.424-427
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• 2007

스테레오 영상으로부터 3차원 구조를 복원하기 위해서는 깊이맵에 해당하는 시차맵을 생성해야 한다. 시차맵 생성을 위해서는 정합비용을 계산하고, 집성한 후에 시차를 계산하는 절차로 이루어진다. 본 논문에서는 스테레오 영상으로부터 빠르고 안정된 시차맵을 생성하기 위해서 후처리 과정으로 각 스캔라인에 대해서 분산을 이용하여 세그멘테이션을 한 후에 세그멘테이션 별로 평균을 내어 객체간의 구분을 명확히 한다. 조밀 시차맵을 생성하기 위해서는 시차 계산에 실패한 화소들에 대해서도 시차를 계산해야 하는데 본 논문에서는 간단하게 인접 화소의 값을 복사하는 방법으로 홀을 메우는 방법을 제안한다. 실제 환경에서의 다양한 스테레오 영상에 대한 실험 결과들은 제안된 시차맵 생성과 홀을 메우는 방법이 기존의 시차맵 생성 기법만큼 빠르고 기존의 방법보다 좀더 안정적이고 다양한 컴퓨터 비전 시스템응용에 적용될 수 있음을 보여준다.

• Journal of Broadcast Engineering
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• v.16 no.2
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• pp.274-292
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• 2011

This paper proposes an efficient coding method of the depth-map which is different from the natural images. The depth-map are so smooth in both inner parts of the objects and background, but it has sharp edges on the object-boundaries like a cliff. In addition, when a depth-map block is decomposed into bit planes, the characteristic of perfect matching or inverted matching between bit planes often occurs on the object-boundaries. Therefore, the proposed depth-map coding scheme is designed to have the bit-plane unit coding method using the adaptive XOR method for efficiently coding the depth-map images on the object-boundary areas, as well as the conventional DCT-based coding scheme (for example, H.264/AVC) for efficiently coding the inside area images of the objects or the background depth-map images. The experimental results show that the proposed algorithm improves the average bit-rate savings as 11.8 % ~ 20.8% and the average PSNR (Peak Signal-to-Noise Ratio) gains as 0.9 dB ~ 1.5 dB in comparison with the H.264/AVC coding scheme. And the proposed algorithm improves the average bit-rate savings as 7.7 % ~ 12.2 % and the average PSNR gains as 0.5 dB ~ 0.8 dB in comparison with the adaptive block-based depth-map coding scheme. It can be confirmed that the proposed method improves the subjective quality of synthesized image using the decoded depth-map in comparison with the H.264/AVC coding scheme. And the subjective quality of the proposed method was similar to the subjective quality of the adaptive block-based depth-map coding scheme.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.49 no.2
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• pp.83-93
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• 2012

This paper proposes a method to efficiently encode multi-view color videos and depth maps. The proposed coding method for multi-view color videos and depth maps can improve the coding efficiency by additional inter-view prediction, as well as inter-frame prediction. By means of the proposed method, we achieved the coding gain of approximately 55% for 2-view color videos and approximately 12% for 2-view depth maps. For 3-view case, we found that the proposed system yields 54% of coding gain from outer view color videos and 56% of coding gain from center view color videos, respectively. Moreover, for 3-view depth map case, approximately 11% of coding gain from outer view and 13% of coding gain from center view are obtained with the proposed coder, respectively.