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Publication Metadata only 3D shape correspondence by isometry-driven greedy optimization(IEEE Computer Soc, 2010) N/A; Department of Computer Engineering; Sahillioğlu, Yusuf; Yemez, Yücel; PhD Student; Faculty Member; Department of Computer Engineering; Graduate School of Sciences and Engineering; College of Engineering; 215195; 107907We present an automatic method that establishes 3D correspondence between isometric shapes. Our goal is to find an optimal correspondence between two given (nearly) isometric shapes, that minimizes the amount of deviation from isometry. We cast the problem as a complete surface correspondence problem. Our method first divides the given shapes to be matched into surface patches of equal area and then seeks for a mapping between the patch centers which we refer to as base vertices. Hence the correspondence is established in a fast and robust manner at a relatively coarse level as imposed by the patch radius. We optimize the isometry cost in two steps. in the first step, the base vertices are transformed into spectral domain based on geodesic affinity, where the isometry errors are minimized in polynomial time by complete bipartite graph matching. the resulting correspondence serves as a good initialization for the second step of optimization in which we explicitly minimize the isometry cost via an iterative greedy algorithm in the original 3D Euclidean space. We demonstrate the performance of our method on various isometric (or nearly isometric) pairs of shapes for some of which the ground-truth correspondence is available.Publication Metadata only A new scalable multi-view video coding configuration for robust selective streaming of free-viewpoint TV(IEEE, 2007) Özbek, Nükhet; Tunalı, E. Turhan; Department of Electrical and Electronics Engineering; Tekalp, Ahmet Murat; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 26207Free viewpoint TV (FTV) is a new media format that allows a user to change his/her viewpoint freely. To this effect, multi-view video must be coded to sAtışfy two conflicting requirements: i) achieve high compression efficiency, and ii) allow view switching with low delay. This paper proposes a new encoding configuration for scalable multi-view video coding, which achieves a compromise between the two requirements. In the new scalable multi-view configuration, the base layer is encoded with inter-view prediction at a minimum acceptable quality, while enhancement layers for each view only depend on their respective base layers (with no interview prediction). Thus, the base layer shall be served to all users, while enhancement layers shall be served selectively to users depending on their channel bandwidth and viewing direction. We compare the compression efficiency of the proposed method with those of non-scalable multi-view coding (MVC) and simulcast (H.264/AVC of each view independently) solutions.Publication Metadata only H.264 long-term reference selection for videos with frequent camera transitions(IEEE, 2006) Özbek, Nükhet; Department of Electrical and Electronics Engineering; Tekalp, Ahmet Murat; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 26207Long-tern reference prediction is an important feature of the H.264/MPEG-4 AVC standard, which provides a tradeoff between compression gain and computational complexity. In this study, we propose a long-tern reference selection method for videos with frequent camera transitions to optimize compression efficiency at shot boundaries without increasing the computational complexity. Experimental results show up to 50% reduction in the number of bits (at the same PSNR) for frames at the border of camera transitions.Publication Metadata only Hierarchical representation and coding of 3D mesh geometry for transmission of surface/volume data(IEEE, 2006) Celasun, Işıl; Eröksüz, Serkan; Siddiqui, Rizwan A.; Doğan, Ertuğrul; Department of Electrical and Electronics Engineering; Tekalp, Ahmet Murat; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 26207Hierarchical mesh representation and mesh simplification have been addressed in computer graphics for adaptive level-of-detail rendering of 3D objects. In this paper, by using a new simplification method to design hierarchical 3D meshes such that each mesh level has Delaunay topology, we can obtain not only meshes with desired geometric properties, but also efficient compression of the mesh data. The hierarchical compression technique is based on a nearest-neighbor ordering of mesh node points. The baseline is the use of entropy coding of linear prediction between nearest neighbor node coordinates. Vector quantization is also employed just to be able to process efficiently stAtıştical dependences between prediction error vectors of a node. The compression method allows progressive transmission and quality scalability.Publication Metadata only Quality assessment of asymmetric stereo video coding(IEEE, 2010) N/A; N/A; Department of Electrical and Electronics Engineering; Saygılı, Görkem; Gürler, Cihat Göktuğ; Tekalp, Ahmet Murat; Master Student; PhD Student; Faculty Member; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; 26207It is well known that the human visual system can perceive high frequencies in 3D, even if that information is present in only one of the views. therefore, the best 3D stereo quality may be achieved by asymmetric coding where the reference (right) and auxiliary (left) views are coded at unequal PSNR. However, the questions of what should be the level of this asymmetry and whether asymmetry should be achieved by spatial resolution reduction or SNR (quality) reduction are open issues. Extensive subjective tests indicate that when the reference view is encoded at sufficiently high quality, the auxiliary view can be encoded above a low-quality threshold without a noticeable degradation on the perceived stereo video quality. This low-quality threshold may depend on the 3D display; e.g., it is about 31 dB for a parallax barrier display and 33 dB for a polarized projection display. Subjective tests show that, Above this PSNR threshold value, users prefer SNR reduction over spatial resolution reduction on both parallax barrier and polarized projection displays. It is also observed that, if the auxiliary view is encoded below this threshold value, symmetric coding starts to perform better than asymmetric coding in terms of perceived 3D video quality.Publication Metadata only Rate-visual-distortion optimized extraction with quality layers for scalable coding of stereo videos(Institute of Electrical and Electronics Engineers (IEEE), 2008) Özbek, Nükhet; Department of Electrical and Electronics Engineering; Tekalp, Ahmet Murat; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 26207The quality layers concept is proposed and adopted in the JSVM in order to ensure an optimal adaptation in a rate-distortion sense. In this paper it is extended to multiview case for scalable coding of stereo videos. Rate-visual-distortion optimized rate allocation among the views is necessary for efficient transport of 3DTV data over the Internet. This paper addresses a standard compatible approach to solve the problem. Experimental results are presented that demonstrate the effectiveness of the proposed method for several stereo videos.Publication Metadata only Scalable multi-view video coding for interactive 3DTV(IEEE, 2006) Özbek, Nükhet; Department of Electrical and Electronics Engineering; Tekalp, Ahmet Murat; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 26207A standard for scalable video coding (SVC) is currently being worked on by the ISO MPEG Group. Work on standardization of multiple-view video coding (MVC) has also recently started under the ISO MPEG. Although there are many approaches published on SVC and WC, there is no current work reported on scalable multi-view video coding (SMVC). This paper presents new coding structures for scalable stereo and multi-view video coding The proposed structures are implemented as extensions to the JSVM software and resulting bitrates and PSNR are demonstrated. SMVC can be used for transport of multiview video over IP for interactive 3DTV by dynamic adaptive combination of temporal, spatial, and SNR scalability according to network conditions.Publication Metadata only Scanning led array based volumetric display(IEEE, 2007) N/A; Department of Electrical and Electronics Engineering; Sayınta, Murat; Ürey, Hakan; PhD Student; Faculty Member; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 8579This paper reports a novel volumetric display system using 1D LED arrays mounted on rotating platforms to create a quasi-holographic display. the system employs a 2D array of such modules and a special diffuser screen in front of them. a virtual 3D image pixel (voxel) appears behind the screen at the intersection of 2 rays emitted from 2 LEDs at different rotation angles. the basic concept is reported for the first time here. a subsystem demonstrator is developed using a single LED mounted on a polymer scanner platform rotating at 60Hz, which corresponds to the refresh rate of the display system. Large rotation angle and high modulation speeds are achievable with LEDs mounted on polymer scanners. an array of LEDs can be driven by a LED Driving IC, integrated with the polymer scanner.Publication Metadata only Unequal inter-view rate allocation using scalable stereo video coding and an objective stereo video quality measure(IEEE, 2008) Özbek, Nükhet; Department of Electrical and Electronics Engineering; Tekalp, Ahmet Murat; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 26207In stereoscopic 3D video, it is well-known that humans can perceive high quality 3D video provided that one of the views is in high quality. Hence, in stereo video encoding, the best overall rate vs. perceived-distortion performance may be achieved by reduction of the spatial, temporal, and/or quantization resolution of the second view, while keeping the first view in full resolution. In this paper, we address the best selection of unequal inter-view rate allocation strategy depending on the content of the video for a scalable multi-view video codec (SMVC) [1]. Since the perceived 3D video quality does not correlate well with the average PSNR of the two views, we propose a new quantitative measure using a weighted combination of two PSNR values and a jerkiness measure. We verified that unequal rate allocation between the left and right views results in better perceived stereo video quality.Publication Metadata only Viterbi-like joint optimization of stereo extraction for on-line rate adaptation in scalable multiview video coding(Institute of Electrical and Electronics Engineers (IEEE), 2010) Özbek, Nükhet; Department of Electrical and Electronics Engineering; Tekalp, Ahmet Murat; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 26207The concept of Quality Layers (QL) has been adopted in the SVC standard in order to ensure optimal rate adaptation of pre-coded video in the rate-distortion sense [1]. We have previously extended QL to multiview scalable video for efficient transport of 3DTV over the Internet [2]. However, it is not possible to use the QL method in applications that require real-time encoding since priority determination process assumes the availability of the whole stereo video sequence. In this work, a Viterbi-like on-line, joint optimization of right and left view rate-adaptation is proposed for real-time scalable stereo video coding (with one GoP delay). We assume that the encoder/extractor is aware of the available dynamic network bandwidth in order to perform rate-distortion optimized MGS layer selection for each GoP. Experimental results show that the performance of proposed on-line method is comparable to that of QL that would require the whole stereo sequence.