| 1. |
- Al-Zubaidy, Hussein, et al.
(författare)
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Reliable Video Streaming With Strict Playout Deadline in Multihop Wireless Networks
- 2017
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Ingår i: IEEE transactions on multimedia. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 1520-9210 .- 1941-0077. ; 19:10, s. 2238-2251
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Tidskriftsartikel (refereegranskat)abstract
- Motivated by emerging vision-based intelligent services, we consider the problem of rate adaptation for high-quality and low-delay visual information delivery over wireless networks using scalable video coding. Rate adaptation in this setting is inherently challenging due to the interplay between the variability of the wireless channels, the queuing at the network nodes, and the frame-based decoding and playback of the video content at the receiver at very short time scales. To address the problem, we propose a low-complexity model-based rate adaptation algorithm for scalable video streaming systems, building on a novel performance model based on stochastic network calculus. We validate the analytic model using extensive simulations. We show that it allows fast near-optimal rate adaptation for fixed transmission paths, as well as cross-layer optimized routing and video rate adaptation in mesh networks, with less than 10% quality degradation compared to the best achievable performance.
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| 2. |
- Amara, Umme, et al.
(författare)
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Molecular Intercommunication between the Complement and Coagulation Systems
- 2010
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Ingår i: Journal of Immunology. - : The American Association of Immunologists. - 0022-1767 .- 1550-6606. ; 185:9, s. 5628-5636
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Tidskriftsartikel (refereegranskat)abstract
- The complement system as well as the coagulation system has fundamental clinical implications in the context of life-threatening tissue injury and inflammation. Associations between both cascades have been proposed, but the precise molecular mechanisms remain unknown. The current study reports multiple links for various factors of the coagulation and fibrinolysis cascades with the central complement components C3 and C5 in vitro and ex vivo. Thrombin, human coagulation factors (F) XIa, Xa, and IXa, and plasmin were all found to effectively cleave C3 and C5. Mass spectrometric analyses identified the cleavage products as C3a and C5a, displaying identical molecular weights as the native anaphylatoxins C3a and C5a. Cleavage products also exhibited robust chemoattraction of human mast cells and neutrophils, respectively. Enzymatic activity for C3 cleavage by the investigated clotting and fibrinolysis factors is defined in the following order: FXa > plasmin > thrombin > FIXa > FXIa > control. Furthermore, FXa-induced cleavage of C3 was significantly suppressed in the presence of the selective FXa inhibitors fondaparinux and enoxaparin in a concentration-dependent manner. Addition of FXa to human serum or plasma activated complement ex vivo, represented by the generation of C3a, C5a, and the terminal complement complex, and decreased complement hemolytic serum activity that defines exact serum concentration that results in complement-mediated lysis of 50% of sensitized sheep erythrocytes. Furthermore, in plasma from patients with multiple injuries (n = 12), a very early appearance and correlation of coagulation (thrombin-antithrombin complexes) and the complement activation product C5a was found. The present data suggest that coagulation/fibrinolysis proteases may act as natural C3 and C5 convertases, generating biologically active anaphylatoxins, linking both cascades via multiple direct interactions in terms of a complex serine protease system. The Journal of Immunology, 2010, 185: 5628-5636.
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| 3. |
- Barry, Ousmane, et al.
(författare)
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Robust Motion-Compensated Orthogonal Video Coding Using EBCOT
- 2010
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Ingår i: Proceedings - 4th Pacific-Rim Symposium on Image and Video Technology, PSIVT 2010. - : IEEE. - 9781424488902 ; , s. 264-269
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Konferensbidrag (refereegranskat)abstract
- This paper proposes a rate-distortion control for motion-compensatedorthogonal video coding schemes and evaluates its robustness to packet loss as faced in, e.g., IP networks. The robustness of standard hybrid video coding is extensively studied in the literature. In contrast, motion-compensated orthogonal subbands offer important advantages and new features for robust video transmission. In this work, we utilize so-called uni-directional motioncompensated orthogonal transforms in combination with entropy coding similar to EBCOT known from JPEG2000.The approach provides a flexible embedded structure and allows flexible rate-distortion optimization. Moreover, it may even permit separate encoding and rate control. The proposed rate-distortion control takes channel coding into account and obtains a preemptively protected representation. Our implementation is based on repetition codes, adapted to the channel condition, and improves the PSNR significantly. The optimization requires an estimate of the packet loss rate at the encoder and shows moderate sensitivity to estimation errors.
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| 4. |
- Burk, Anne-Maud, et al.
(författare)
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Early Complementopathy After Multiple Injuries in Humans.
- 2012
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Ingår i: Shock. - 1540-0514. ; 37:4, s. 348-354
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Tidskriftsartikel (refereegranskat)abstract
- ABSTRACT: After severe tissue injury, innate immunity mounts a robust systemic inflammatory response. However, little is known about the immediate impact of multiple trauma on early complement function in humans. In the present study we hypothesized that multiple trauma results in immediate activation, consumption and dysfunction of the complement cascade and that the resulting severe "complementopathy" may be associated with morbidity and mortality.Therefore a prospective multicenter study with 25 healthy volunteers and 40 polytrauma patients (mean injury severity score [ISS] = 30.3 ± 2.9) was performed. After polytrauma serum was collected as early as possible at the scene, upon admission to the emergency room and 4, 12, 24, 120 and 240 hours post trauma and analysed for the complement profile. Complement hemolytic activity (CH-50) was massively reduced within the first 24 h after injury, recovered only 5 days after trauma and discriminated between lethal and non-lethal 28-day outcome. Serum levels of the complement activation products C3a and C5a were significantly elevated throughout the entire observation period and correlatedwith the severity of traumatic brain injury and survival. The soluble terminal complement complex SC5b-9 and mannose-binding lectin (MBL) showed a biphasic response after trauma. Key fluid phase inhibitors of complement, such as C4b-binding protein (C4BP) and factor I, were significantly diminished early after trauma.The present data indicate an almost synchronically rapid activation and dysfunction of complement suggesting a trauma-induced "complementopathy" early after injury. These events may participate to the impairment of the innate immune response observed after severe trauma.
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| 5. |
- Ebri Mars, David, et al.
(författare)
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GEOMETRY-BASED RANKING FOR MOBILE 3D VISUAL SEARCH USING HIERARCHICALLY STRUCTURED MULTI-VIEW FEATURES
- 2015
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Ingår i: 2015 IEEE INTERNATIONAL CONFERENCE ON IMAGE PROCESSING (ICIP). - : IEEE Computer Society. - 9781479983391 ; , s. 3077-3081
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Konferensbidrag (refereegranskat)abstract
- This paper proposes geometry-based ranking for mobile 3D visual search. It utilizes the underlying geometry of the 3D objects as well as the appearance to improve the ranking results. A double hierarchy has been embedded in the data structure, namely the hierarchically structured multi-view features for each object and a tree hierarchy from multi-view vocabulary trees. As the 3D geometry information is incorporated in the multi-view vocabulary tree, it allows us to evaluate the consistency of the 3D geometry at low computational complexity. Thus, a cost function is proposed for object ranking using geometric consistency. With that, we devise an iterative algorithm that accomplishes 3D geometry-based ranking. The experimental results show that our 3D geometry-based ranking improves the recall-datarate performance as well as the subjective ranking results for mobile 3D visual search.
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| 6. |
- Flierl, Markus
(författare)
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A l(1)-NORM PRESERVING MOTION-COMPENSATED TRANSFORM FOR SPARSE APPROXIMATION OF IMAGE SEQUENCES
- 2010
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Konferensbidrag (refereegranskat)abstract
- This paper discusses an adaptive non-linear transform for image sequences that aims to generate a l(1)-norm preserving sparse approximation for efficient coding. Most sparse approximation problems employ a linear model where images are represented by a basis and a sparse set of coefficients. In this work, however, we consider image sequences where linear measurements are of limited use due to motion. We present a motion-adaptive non-linear transform for a group of pictures that outputs common and detail coefficients and that minimizes the l(1) norm of the detail coefficients while preserving the overall l(1) norm. We demonstrate that we can achieve a smaller l(1) norm of the detail coefficients when compared to that of motion-adaptive linear measurements. Further, the decay of normalized absolute coefficients is faster than that of motion-adaptive linear measurements.
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| 7. |
- Flierl, Markus
(författare)
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Adaptive spatial wavelets for motion-compensated orthogonal video transforms
- 2009
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Ingår i: 2009 16th IEEE International Conference on Image Processing (ICIP). - : IEEE. - 9781424456536 ; , s. 1045-1048
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Konferensbidrag (refereegranskat)abstract
- This paper discusses adaptive spatial wavelets for the class of motion-compensated orthogonal video transforms. Motion-compensated orthogonal transforms (MCOT) are temporal transforms for video sequences that maintain orthonormality while permitting flexible motion compensation. Orthogonality is maintained for arbitrary integer-pixel or sub-pixel motion compensation by cascading a sequence of incremental orthogonal transforms and updating so-called scale counters for each pixel. The energy of the input pictures is accumulated in a temporal low-band while the temporal high-bands are zero if the input pictures are identical after motion compensation. For efficient coding, the temporal subbands should be further spatially decomposed to exploit the spatial correlation within each temporal subband. In this paper, we discuss adaptive spatial wavelets that maintain the orthogonal representation of the temporal transforms. Similar to the temporal transforms, they update scale counters for efficient energy concentration. The type-1 adaptive wavelet is a Haar-like wavelet. The type-2 considers three pixels at a time and achieves better energy compaction than the type-1.
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| 8. |
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| 9. |
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| 10. |
- Flierl, Markus, et al.
(författare)
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Image transform for video coding
- 2006
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Patent (populärvet., debatt m.m.)abstract
- A method is disclosed for decomposing a set of even and odd pictures into low-band and high-band pictures respectively in a image decomposing unit, in which the even picture is used by at least two prediction motion compensators on which the output signal of each prediction motion compensator is scaled according to the number of prediction motion compensators. The method includes calculating the high-band picture by subtracting from the odd picture the scaled motion-compensated signals and using the high-band picture in the at least two update motion compensators, the output signal of each update motion compensator being scaled according to the number of update motion compensators. Finally, the low-band picture is calculated by adding the scaled update motion-compensated signals to the even picture.
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| 11. |
- Flierl, Markus, et al.
(författare)
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Method for spatially scalable video coding
- 2004
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Patent (populärvet., debatt m.m.)abstract
- A method for decomposing a digital image at resolution R and MR into a set of spatial sub-bands of resolution R and MR where MR>R and where the high-band at resolution MR is calculated by subtracting the filtered and up-sampled image at resolution R from the image at resolution MR and where the spatial low-band at resolution R is calculated by adding the filtered and down-sampled spatial high-band to the image at resolution R and where a rational factor for up-and down-sampling M is determined by the resolution ratio.
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| 12. |
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| 13. |
- Flierl, Markus, et al.
(författare)
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Multiview Video Compression : Exploiting Inter-Image Similarities
- 2007
-
Ingår i: IEEE signal processing magazine (Print). - 1053-5888 .- 1558-0792. ; 24:6, s. 66-76
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Tidskriftsartikel (refereegranskat)abstract
- Due to the vast raw bit rate of multiview video, efficient compression techniques are essential for 3D scene communication. As the video data originate from the same scene, the inherent similarities of the multiview imagery are exploited for efficient compression. These similarities can be classified into two types, inter-view similarity between adjacent camera views and temporal similarity between temporally successive images of each video.
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| 14. |
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| 15. |
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| 16. |
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| 17. |
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| 18. |
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| 19. |
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| 20. |
- Helgason, Hannes, et al.
(författare)
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Multiscale framework for adaptive and robust enhancement of depth in multi-view imagery
- 2012
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Ingår i: Image Processing (ICIP), 2012 19th IEEE International Conference on. - : IEEE. - 9781467325332 ; , s. 13-16
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Konferensbidrag (refereegranskat)abstract
- Depth Image Based Rendering (DIBR) is a standard technique in free viewpoint television for rendering virtual camera views. For synthesis it utilizes one or several reference texture images and associated depth images, which contain information about the 3D structure of the scene. Many popular depth estimation methods infer the depth information by considering texture images in pairs. This often leads to severe inconsistencies among multiple reference depth images, resulting in poor rendering quality. We propose a method which takes as input a set of depth images and returns an enhanced depth map to be used for rendering at the virtual viewpoint. Our framework is data-driven and based on a simple geometric multiscale model of the underlying depth. Inconsistencies and errors in the inputted depth images are handled locally using tools from the field of robust statistics. Numerical comparison shows the method outperform standard MPEG DIBR software.
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| 21. |
- Karlsson, Johannes, 1981-
(författare)
-
Low-delay sensing and transmission in wireless sensor networks
- 2008
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- With the increasing popularity and relevance of ad-hoc wireless sensor networks, cooperative transmission is more relevant than ever. In this thesis, we consider methods for optimization of cooperative transmission schemes in wireless sensor networks. We are in particular interested in communication schemes that can be used in applications that are critical to low-delays, such as networked control, and propose suitable candidates of joint source-channel coding schemes. We show that, in many cases, there are significant gains if the parts of the system are jointly optimized for the current source and channel. We especially focus on two means of cooperative transmission, namely distributed source coding and relaying. In the distributed source coding case, we consider transmission of correlated continuous sources and propose an algorithm for designing simple and energy-efficient sensor nodes. In particular the cases of the binary symmetric channel as well as the additive white Gaussian noise channel are studied. The system works on a sample by sample basis yielding a very low encoding complexity, at an insignificant delay. Due to the source correlation, the resulting quantizers use the same indices for several separated intervals in order to reduce the quantization distortion. For the case of relaying, we study the transmission of a continuous Gaussian source and the transmission of an uniformly distributed discrete source. In both situations, we propose design algorithms to design low-delay source-channel and relay mappings. We show that there can be significant power savings if the optimized systems are used instead of more traditional systems. By studying the structure of the optimized source-channel and relay mappings, we provide useful insights on how the optimized systems work. Interestingly, the design algorithm generally produces relay mappings with a structure that resembles Wyner-Ziv compression.
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| 22. |
- Li, Haopeng, et al.
(författare)
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3D model hypotheses for player segmentation and rendering in free-viewpoint soccer video
- 2012
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Ingår i: Proceedings - 2012 IEEE International Symposium on Multimedia, ISM 2012. - : IEEE. - 9780769548753 ; , s. 203-209
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Konferensbidrag (refereegranskat)abstract
- This paper presents a player segmentation approach based on 3D model hypotheses for soccer games. We use a hyperplane model for player modeling and a collection of piecewise geometric models for background modeling. To determine the assignment of each pixel in the image plane, we test it with two model hypotheses. We construct a cost function that measures the fitness of model hypotheses for each pixel. To fully utilize the perspective diversity of the multiview imagery, we propose a three-step strategy to choose the best model for each pixel. The experimental results show that our segmentation approach based on 3D model hypotheses outperforms conventional temporal median and graph cut methods for both subjective and objective evaluation.
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| 23. |
- Li, Haopeng
(författare)
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Feature-Based Image Processing for Rendering, Compression, and Visual Search
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Visual communication, vivid, meaningful, and creative, permits a way to express information visually. The communication media, by images, graphs and videos, passes informative color and shape to human perception sensors. But when we look close, we wonder: are we merely a passive receiver? Or can we actively select what we would like? Can our eyes only sense the visual images? Or can we enjoy a comprehensive immersive experience of the real world? To discover wonders, we have to explore the essentials and under wraps of visual communication.The work described in this dissertation develops the techniques of visual communication, including rendering, compression and visual search. We leave the conventional pixel-by-pixel image processing behind to explore the opportunities of sparse feature-based image processing. Thus, in this dissertation, a new objective is proposed: to seek a methodology to improve the performance of visual communication by using geometric information carried by the image features. To motivate it, we investigate two systems of visual communication, namely free viewpoint coding and rendering, and mobile visual search. The first system is based on the delivery and presentation of multi-view videos. We demonstrate how to use the image features for efficient video coding and high quality virtual view rendering. To further boost the importance of image features, we discuss the second system, the mobile visual search system, which is only based on the transmission of image features. We illustrate how to achieve reliable identification by using sparse image features.The system of free-viewpoint coding and rendering encodes and delivers the video content to the end-user and allows interactively choosing and rendering a virtual viewpoint in real time. We propose a content-adaptive coding and rendering method to separate the dynamic and static video content items, and apply content-adaptive coding and rendering to each of them. The content-adaptive scheme comprises the extraction of static and dynamic content, the video coding engines, and a synthesis unit for virtual view rendering. We address the problem of using the image features for rate-distortion optimal video coding and high quality geometry model-based rendering. For the video coding engine, we study a feature-based motion compensation scheme and an optimal rate allocation model. For the component of free viewpoint rendering, we study a hypothesis-driven free viewpoint rendering approach based on 3D model hypotheses.For the second system of mobile visual search, we propose a geometry-based search, namely mobile 3D visual search. The end-to-end scheme uses a client-server model for visual communication. The client extracts and encodes the features of the query. The server holds the feature database derived from the multi-view imagery, as well as the feature matching engine. We address the problem of rate-constrained identification by using multi-view image features. For the client, we propose a rate-constrained feature coding method to efficiently encode the query features. For the server side, we propose a double hierarchy to structure the database for indexing the database features. Moreover, we develop an algorithm that accomplishes 3D geometry-based matching and ranking by utilizing 3D geometric information and 2D texture information jointly.
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| 24. |
- Li, Haopeng, et al.
(författare)
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Mobile 3D Visual Search using the Helmert Transformation of Stereo Features
- 2013
-
Konferensbidrag (refereegranskat)abstract
- This work presents a scheme for mobile 3D visual search that facilitates mobile recognition of 3D objects. We use a multi-view approach to extract the 3D geometric information of the query objects and integrate it into SIFT descriptors. To meet a given transmission bandwidth, we use a rate-constrained quad-tree representation for feature selection and encoding. With this approach, we are able to progressively match the query features against the stereo features in the database and implement a robust geometric verification with the Helmert transformation.
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| 25. |
- Li, Haopeng, et al.
(författare)
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Rate-Distortion-Optimized Content-Adaptive Coding For Immersive Networked Experience Of Sports Events
- 2011
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Konferensbidrag (refereegranskat)abstract
- This paper presents a content-adaptive coding scheme for immersive networked experience of sports events, in particular, soccer games. We assume that future sports events are captured by an array of fixed high-definition cameras which provide multiview image sequences for a free-viewpoint immersive networked experience in a home environment. We discuss a content-adaptive coding scheme for image sequences that exploits properties of such sequences and that permits efficient user interactions. In this work, we construct a rate distortion model for an image sequence to obtain the optimal bitrate allocation among static and dynamic content items. The optimal bitrate allocation results in a rate distortion performance of the coding scheme that outperforms that of conventional H.264/AVC coding significantly.
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| 26. |
- Li, Haopeng, et al.
(författare)
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SIFT-BASED IMPROVEMENT OF DEPTH IMAGERY
- 2011
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Konferensbidrag (refereegranskat)abstract
- Depth Image Based Rendering (DIBR) is a widely used technique to enable free viewpoint television. It utilizes one or more reference texture images and their associated depth images to synthesize virtual camera views. The depth image plays a crucial role for DIBR. However, most of the conventional depth image estimation approaches determine the depth information from a limited set of nearby reference images. This leads to inconsistencies among multiple reference depth images, thus resulting in poor rendering quality. In this paper, we propose an approach that uses the Scale Invariant Feature Transform (SIFT) to improve depth images at virtual viewpoints. We extract SIFT features in left and right reference images, and use feature correspondences to improve the consistency between reference depth images. By doing so, the quality of rendered virtual views can be enhanced.
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| 27. |
- Li, Haopeng, et al.
(författare)
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Sift-based modeling and coding of background scenes for multiview soccer video
- 2012
-
Ingår i: Image Processing (ICIP), 2012 19th IEEE International Conference on. - : IEEE. - 9781467325332 ; , s. 1221-1224
-
Konferensbidrag (refereegranskat)abstract
- This paper presents a content-adaptive modeling and coding scheme for static multiview background scenes of soccer games. We discuss a content-adaptive modeling approach for static multiview background imagery that is based on piecewise geometric models of the content. We propose an approach that uses the Scale Invariant Feature Transform (SIFT) to extract the parameters of the geometric models. Moreover, a content-adaptive rendering approach is presented for handling occlusion problems in large baseline scenarios. The experimental results show that our content-adaptive modeling and coding scheme outperforms conventional DIBR schemes.
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| 28. |
- Li, Haopeng, et al.
(författare)
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Sift-based multi-view cooperative tracking for soccer video
- 2012
-
Ingår i: Acoustics, Speech and Signal Processing (ICASSP), 2012 IEEE International Conference on. - : IEEE. - 9781467300469 ; , s. 1001-1004
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Konferensbidrag (refereegranskat)abstract
- This paper presents a SIFT-based multi-view cooperative tracking scheme for multiple player tracking in soccer games. We assume that future sports events will be captured by an array of fixed high-definition cameras which provide multi-view video sequences. The imagery will then be used to provide a free-viewpoint networked experience. In this work, SIFT features are used to extract the interview and inter-frame correlation among related views. Hence, accurate 3D information of each player can be efficiently utilized for real time multiple player tracking. By sharing the 3D information with all cameras and exploiting the perspective diversity of the multi-camera system, occlusion problems can be solved effectively. The extracted 3D information improves the average reliability of tracking by more than 10% when compared to SIFT-based 2D tracking.
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| 29. |
- Li, Yun
(författare)
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Coding of three-dimensional video content : Depth image coding by diffusion
- 2013
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Three-dimensional (3D) movies in theaters have become a massive commercial success during recent years, and it is likely that, with the advancement of display technologies and the production of 3D contents, TV broadcasting in 3D will play an important role in home entertainments in the not too distant future. 3D video contents contain at least two views from different perspectives for the left and the right eye of viewers. The amount of coded information is doubled if these views are encoded separately. Moreover, for multi-view displays (i.e. different perspectives of a scene in 3D are presented to the viewer at the same time through different angles), either video streams of all the required views must be transmitted to the receiver, or the displays must synthesize the missing views with a subset of the views. The latter approach has been widely proposed to reduce the amount of data being transmitted. The virtual views can be synthesized by the Depth Image Based Rendering (DIBR) approach from textures and associated depth images. However it is still the case that the amount of information for the textures plus the depths presents a significant challenge for the network transmission capacity. An efficient compression will, therefore, increase the availability of content access and provide a better video quality under the same network capacity constraints.In this thesis, the compression of depth images is addressed. These depth images can be assumed as being piece-wise smooth. Starting from the properties of depth images, a novel depth image model based on edges and sparse samples is presented, which may also be utilized for depth image post-processing. Based on this model, a depth image coding scheme that explicitly encodes the locations of depth edges is proposed, and the coding scheme has a scalable structure. Furthermore, a compression scheme for block-based 3D-HEVC is also devised, in which diffusion is used for intra prediction. In addition to the proposed schemes, the thesis illustrates several evaluation methodologies, especially, the subjective test of the stimulus-comparison method. It is suitable for evaluating the quality of two impaired images, as the objective metrics are inaccurate with respect to synthesized views.The MPEG test sequences were used for the evaluation. The results showed that virtual views synthesized from post-processed depth images by using the proposed model are better than those synthesized from original depth images. More importantly, the proposed coding schemes using such a model produced better synthesized views than the state of the art schemes. As a result, the outcome of the thesis can lead to a better quality of 3DTV experience.
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| 30. |
- Liu, Du, et al.
(författare)
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Energy Compaction on Graphs for Motion-Adaptive Transforms
- 2015
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Ingår i: Data Compression Conference Proceedings. - 9781479984305 ; , s. 457-
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Konferensbidrag (refereegranskat)abstract
- It is well known that the Karhunen-Loeve Transform (KLT) diagonalizes the covariance matrix and gives the optimal energy compaction. Since the real covariance matrix may not be obtained in video compression, we consider a covariance model that can be constructed without extra cost. In this work, a covariance model based on a graph is considered for temporal transforms of videos. The relation between the covariance matrix and the Laplacian is studied. We obtain an explicit expression of the relation for tree graphs, where the trees are defined by motion information. The proposed graph-based covariance is a good model for motion-compensated image sequences. In terms of energy compaction, our graph-based covariance model has the potential to outperform the classical Laplacian-based signal analysis.
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| 31. |
- Liu, Du, et al.
(författare)
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Fractional-Pel Accurate Motion-Adaptive Transforms
- 2019
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Ingår i: IEEE Transactions on Image Processing. - : IEEE. - 1057-7149 .- 1941-0042. ; 28:6, s. 2731-2742
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Tidskriftsartikel (refereegranskat)abstract
- Fractional-pel accurate motion is widely used in video coding. For subband coding, fractional-pel accuracy is challenging since it is difficult to handle the complex motion field with temporal transforms. In our previous work, we designed integer accurate motion-adaptive transforms (MAT) which can transform integer accurate motion-connected coefficients. In this paper, we extend the integer MAT to fractional-pel accuracy. The integer MAT allows only one reference coefficient to be the lowhand coefficient. In this paper, we design the transform such that it permits multiple references and generates multiple low-band coefficients. In addition, our fractional-pel MAT can incorporate a general interpolation filter into the basis vector, such that the highband coefficient produced by the transform is the same as the prediction error from the interpolation filter. The fractional-pel MAT is always orthonormal. Thus, the energy is preserved by the transform. We compare the proposed fractional-pel MAT, the integer MAT, and the half-pel motion-compensated orthogonal transform (MCOT), while HEVC intra coding is used to encode the temporal subbands. The experimental results show that the proposed fractional-pel MAT outperforms the integer MAT and the half-pel MCOT. The gain achieved by the proposed MAT over the integer MAT can reach up to 1 dB in PSNR.
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| 32. |
- Liu, Du, 1986-, et al.
(författare)
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Graph-Based Construction and Assessment of Motion-Adaptive Transforms
- 2013
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Konferensbidrag (refereegranskat)abstract
- In this paper, we propose two algorithms to construct motion-adaptive transforms that are based on vertex-weighted graphs. The graphs are constructed by motion vector information. The weights of the vertices are given by scale factors that are used to accommodate proper concentration of energy in transforms. The vertex-weighted graph defines a one dimensional linear subspace. Thus, our transform basis is subspace constrained. We propose two algorithms. The first is based on the Gram-Schmidt orthonormalization of the discrete cosine transform (DCT) basis. The second combines the rotation of the DCT basis and the Gram-Schmidt orthonormalization. We assess both algorithms in terms of energy compaction. Moreover, we compare to prior work on graph-based rotation of the DCT basis and on so-called motion-compensated orthogonal transforms (MCOT). In our experiments, both algorithms outperform MCOT in terms of energy compaction. However, their performance is similar to that of graph-based rotation of the DCT basis.
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| 33. |
- Liu, Du, 1986-, et al.
(författare)
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Graph-Based Rotation of the DCT Basis for Motion-Adaptive Transforms
- 2013
-
Ingår i: 2013 20TH IEEE INTERNATIONAL CONFERENCE ON IMAGE PROCESSING (ICIP 2013). - : IEEE conference proceedings. - 9781479923410 ; , s. 1802-1805
-
Konferensbidrag (refereegranskat)abstract
- In this paper, we consider motion-adaptive transforms that are based on vertex-weighted graphs. The graphs are constructed by motion vector information and the weights of the vertices are given by scale factors, where the scale factors are used to control the energy compaction of the transform. The vertex-weighted graph defines a one dimensional linear subspace. Thus, our transform basis is subspace constrained. To find a full transform matrix that satisfies our subspace constraint, we rotate the discrete cosine transform (DCT) basis such that the first basis vector matches the subspace constraint. Since rotation is not unique in high dimensions, we choose a simple rotation that only rotates the DCT basis in the plane which is spanned by the first basis vector of the DCT and the subspace constraint. Experimental results on energy compaction show that the motion-adaptive transform based on this rotation is better than the motion-compensated orthogonal transform based on hierarchical decomposition while sharing the same first basis vector.
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| 34. |
- Liu, Du, 1986-, et al.
(författare)
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Motion-Adaptive Transforms Based on the Laplacian of Vertex-Weighted Graphs
- 2014
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Konferensbidrag (refereegranskat)abstract
- We construct motion-adaptive transforms for image sequences by using the eigenvectors of Laplacian matrices defined on vertex-weighted graphs, where the weights of the vertices are defined by scale factors. The vertex weights determine only the first basis vector of the linear transform uniquely. Therefore, we use these weights to define two Laplacians of vertex-weighted graphs. The eigenvectors of each Laplacian share the first basis vector as defined by the scale factors only. As the first basis vector is common for all considered Laplacians, we refer to it as subspace constraint. The first Laplacian uses the inverse scale factors, whereas the second utilizes the scale factors directly. The scale factors result from the assumption of ideal motion. Hence, the ideal unscaled pixels are equally connected and we are free to form arbitrary graphs, such as complete graphs, ring graphs, or motion-inherited graphs. Experimental results on energy compaction show that the Laplacian which is based on the inverse scale factors outperforms the one which is based on the direct scale factors. Moreover, Laplacians of motion-inherited graphs are superior than that of complete or ring graphs, when assessing the energy compaction of the resulting motion-adaptive transforms.
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| 35. |
- Liu, Du, 1986-, et al.
(författare)
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Motion-Adaptive Transforms based on Vertex-Weighted Graphs
- 2013
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Ingår i: 2013 Data Compression Conference (DCC). - : IEEE Computer Society. - 9781467360371 ; , s. 181-190
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Konferensbidrag (refereegranskat)abstract
- Motion information in image sequences connects pixels that are highly correlated. In this paper, we consider vertex-weighted graphs that are formed by motion vector information. The vertex weights are defined by scale factors which are introduced to improve the energy compaction of motion-adaptive transforms. Further, we relate the vertex-weighted graph to a subspace constraint of the transform. Finally, we propose a subspace-constrained transform (SCT) that achieves optimal energy compaction for the given constraint. The subspace constraint is derived from the underlying motion information only and requires no additional information. Experimental results on energy compaction confirm that the motion-adaptive SCT outperforms motion-compensated orthogonal transforms while approaching the theoretical performance of the Karhunen Loeve Transform (KLT) along given motion trajectories.
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| 36. |
- Liu, Du, 1986-
(författare)
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Orthonormal Motion-Adaptive Transforms for Image Sequences
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis, we propose and discuss a class of motion-adaptive transforms (MAT) to describe the temporal correlation in image sequences for compression. The temporal correlation is based on motion models, and undirected graphs are used to represent this correlation in image sequences. The transforms are adaptive to general motion fields. Hence, they avoid the predict-update mismatch of the classic block-motion lifting schemes in processing connected and disconnected pixels. Moreover, the proposed transforms are orthonormal for general motion field, and thus, they permit energy conservation and perfect reconstruction.As we represent the motion-connected signals by graphs, we introduce a graph-based covariance matrix model and use the associated eigenvector matrix for compression. As the proposed covariance model is closely related to the graph, the relation between the covariance matrix and theLaplacian matrix is studied and the associated eigenvector matrices are discussed. The class of MAT is constructed by using so-called scale factors.We show that the scale factors determine a relevant subspace of the signal representation.Hence, we propose a subspace-constrained transform, which achieves optimal energy compaction given the subspace constraint. On the other hand, the resulting basis vectors are signal dependent.To construct practical transforms without using covariance matrices, we consider two types of incremental transforms over graphs, namely the uni-directional orthogonal transform (Uni-OT) and the bidirectional orthogonal transform (Bi-OT). In addition, fractional-pel MAT is proposed to further extend the class of MAT. Our fractional-pel MAT can incorporate a general interpolation filter into the basis vectors, while offering perfect reconstruction, orthogonality, and improved coding efficiency.
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| 37. |
- Liu, Du, et al.
(författare)
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Temporal Signal Basis for Hierarchical Block Motion in Image Sequences
- 2018
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Ingår i: IEEE Signal Processing Letters. - : IEEE. - 1070-9908 .- 1558-2361. ; 25:1, s. 10-14
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Tidskriftsartikel (refereegranskat)abstract
- In classic data compression, the optimal transform for energy compaction is the Karhunen-Loeve transform with the eigenvectors of the covariance matrix. In coding applications, neither the covariance matrix nor the eigenvectors can be easily transmitted to the decoder. In this letter, we introduce a covariance matrix model based on graphs determined by hierarchical block motion in image sequences and use its eigenvector matrix for compression. The covariance matrix model is defined using the graph distance matrix, where the graph is determined by block motion. As the proposed covariance matrix is closely related to the graph, the relation between the covariance matrix and the Laplacian matrix is studied and their eigenvector matrices are discussed. From our assumptions, we show that our covariance model can be viewed as a Gaussian graphicalmodel where the signal is described by the second order statistics and the zeros in the precision matrix indicate missing edges in the graph. To assess the compression performance, we relate the coding gain due to the eigenbasis of the covariance model to that of the Laplacian eigenbasis. The experimental results show that the eigenbasis of our covariance model is advantageous for tree-structured blockmotion in image sequences.
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| 38. |
- Liu, Du, et al.
(författare)
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Video coding using multi-reference motion-adaptive transforms based on graphs
- 2016
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Ingår i: 2016 IEEE 12th Image, Video, and Multidimensional Signal Processing Workshop, IVMSP 2016. - : IEEE. - 9781509019298
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Konferensbidrag (refereegranskat)abstract
- The purpose of the work is to produce jointly coded frames for efficient video coding. We use motion-adaptive transforms in the temporal domain to generate the temporal subbands. The motion information is used to form graphs for transform construction. In our previous work, the motion-adaptive transform allows only one reference pixel to be the lowband coefficient. In this paper, we extend the motion-adaptive transform such that it permits multiple references and produces multiple lowband coefficients, which can be used in the case of bidirectional or multihypothesis motion estimation. The multi-reference motion-adaptive transform (MRMAT) is always orthonormal, thus, the energy is preserved by the transform. We compare MRMAT and the motion-compensated orthogonal transform (MCOT) [1], while HEVC intra coding is used to encode the temporal subbands. The experimental results show that MRMAT outperforms MCOT by about 0.6dB.
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| 39. |
- Liu, Du, et al.
(författare)
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Video coding with adaptive motion-compensated orthogonal transforms
- 2012
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Konferensbidrag (refereegranskat)abstract
- Well-known standard hybrid coding techniques utilize the concept of motion-compensated predictive coding in a closed-loop. The resulting coding dependencies are a major challenge for packet-based networks like the Internet. On the other hand, subband coding techniques avoid the dependencies of predictive coding and are able to generate video streams that better match packet-based networks. An interesting class for subband coding is the so-called motion-compensated orthogonal transform. It generates orthogonal subband coefficients for arbitrary underlying motion fields. In this paper, a theoretical signal model based on Gaussian distributions is discussed to construct a cost function for efficient rate allocation. Additionally, a rate-distortion efficient video coding scheme is developed that takes advantage of motion-compensated orthogonal transforms. The scheme combines multiple types of motion-compensated orthogonal transforms, variable block sizes, and half-pel accurate motion compensation. The experimental results show that this adaptive scheme outperforms individual motion-compensated orthogonal transforms by up to 2 dB.
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| 40. |
- Lu, Xiaohua, et al.
(författare)
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H.264-compatible coding of background soccer video using temporal subbands
- 2012
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Ingår i: Proceedings - 2012 IEEE International Symposium on Multimedia, ISM 2012. - : IEEE. - 9780769548753 ; , s. 141-144
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Konferensbidrag (refereegranskat)abstract
- This paper presents an H.264-compatible temporal subband coding scheme for static background scenes of soccer video. We utilize orthonormal wavelet transforms to decompose a group of successive frames into temporal subbands. By exploiting the property of energy conservation of orthonormal wavelet transforms, we construct a rate distortion model for optimal bitrate allocation among different subbands. To take advantage of the high efficiency video codec H.264/AVC, we encode each subband with H.264/AVC Fidelity Range Extension (FRExt) intra-coding by assigning optimal bitrates. The experimental results show that our proposed coding scheme outperforms conventional video coding with H.264/AVC for both subjective and objective evaluations.
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| 41. |
- Lyu, Xinrui, et al.
(författare)
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Hierarchically Structured Multi-View Features for Mobile Visual Search
- 2014
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Konferensbidrag (refereegranskat)abstract
- This paper presents an approach for using hierarchically structured multi-view features for mobile visual search. We utilize a graph model to describe the feature correspondences between multi-view images. To add features of images from new viewpoints, we design a level raising algorithm and the associated multi-view geometric verification, which are based on the properties of the hierarchical structure. With this approach, features from new viewpoints can be recursively added in an incremental fashion. Additionally, we design a query matching strategy which utilizes the advantage of the hierarchical structure. The experimental results show that our structure of the multi-view feature database can efficiently improve the performance of mobile visual search.
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| 42. |
- Ma, Zhanyu, et al.
(författare)
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Bayesian estimation of Dirichlet mixture model with variational inference
- 2014
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Ingår i: Pattern Recognition. - : Elsevier BV. - 0031-3203 .- 1873-5142. ; 47:9, s. 3143-3157
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Tidskriftsartikel (refereegranskat)abstract
- In statistical modeling, parameter estimation is an essential and challengeable task. Estimation of the parameters in the Dirichlet mixture model (DMM) is analytically intractable, due to the integral expressions of the gamma function and its corresponding derivatives. We introduce a Bayesian estimation strategy to estimate the posterior distribution of the parameters in DMM. By assuming the gamma distribution as the prior to each parameter, we approximate both the prior and the posterior distribution of the parameters with a product of several mutually independent gamma distributions. The extended factorized approximation method is applied to introduce a single lower-bound to the variational objective function and an analytically tractable estimation solution is derived. Moreover, there is only one function that is maximized during iterations and, therefore, the convergence of the proposed algorithm is theoretically guaranteed. With synthesized data, the proposed method shows the advantages over the EM-based method and the previously proposed Bayesian estimation method. With two important multimedia signal processing applications, the good performance of the proposed Bayesian estimation method is demonstrated.
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| 43. |
- Mahima, K.T.Y, et al.
(författare)
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Fighting Dengue Fever with Aerial Drones
- 2022
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Ingår i: EWSN '22. - : Association for Computing Machinery (ACM). ; , s. 206-207
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Konferensbidrag (refereegranskat)abstract
- Dengue and Zika are two arboviral viruses that affect a significant portion of the world population. Each year, almost 400 million dengue infections happen. Due to severe dengue fever, around half a million people each year are in need of hospitalization and about 36.000 people die.Dengue spreads rapidly in densely populated urban areas. The principle vector species of both dengue and zika viruses are the Aedes aegypti and Aedes albopictus mosquitoes. They breed in very slow-flowing or standing water pools. It is important to reduce and control such potential breeding grounds to contain the spread of these diseases.We describe our system design and presents initial results. We employ mmWave radios to detect water retention areas as potential mosquito habitats. Next, we use multi-spectral images to analyze the water area, measure the depth of the water, and understand the larvae density. After that, we fuse the results for the final classification of the water area.
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| 44. |
- Mahima, K. T. Y., et al.
(författare)
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MM4Drone : A Multi-spectral Image and mmWave Radar Approach for Identifying Mosquito Breeding Grounds via Aerial Drones
- 2023
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Ingår i: Lecture Notes of the Institute for Computer Sciences, Social-Informatics and Telecommunications Engineering, LNICST. - Cham : Springer Science and Business Media Deutschland GmbH. - 9783031345852 - 9783031345869 ; , s. 412-426, s. 412-426
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Konferensbidrag (refereegranskat)abstract
- Mosquitoes spread disases such as Dengue and Zika that affect a significant portion of the world population. One approach to hamper the spread of the disases is to identify the mosquitoes’ breeding places. Recent studies use drones to detect breeding sites, due to their low cost and flexibility. In this paper, we investigate the applicability of drone-based multi-spectral imagery and mmWave radios to discover breeding habitats. Our approach is based on the detection of water bodies. We introduce our Faster R-CNN-MSWD, an extended version of the Faster R-CNN object detection network, which can be used to identify water retention areas in both urban and rural settings using multi-spectral images. We also show promising results for estimating extreme shallow water depth using drone-based multi-spectral images. Further, we present an approach to detect water with mmWave radios from drones. Finally, we emphasize the importance of fusing the data of the two sensors and outline future research directions.
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| 45. |
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| 46. |
- Mars, David, et al.
(författare)
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Joint Geometric Verification and Ranking using Multi-View Vocabulary Trees for Mobile 3D Visual Search
- 2015
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Ingår i: Data Compression Conference Proceedings. - 9781479984305
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Konferensbidrag (refereegranskat)abstract
- This paper proposes multi-view vocabulary trees for mobile 3D visual search. We generate hierarchically structured multi-view features and construct a multi-view vocabulary tree from the multi-view images. As the 3D geometry information is incorporated in the multi-view vocabulary tree, it allows us to design an algorithm forfast 3D geometric verification at low computational complexity. With that, we devise an iterative algorithm that accomplishes jointly matching and geometric verification. The experimental results show that our joint approach to matching and verification improves the recall-datarate performance as well as the subjective ranking results for mobile 3D visual search.
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| 47. |
- Parthasarathy, Srinivas, et al.
(författare)
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Denoising of volumetric depth confidence for view rendering
- 2012
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Ingår i: 3DTV-Conference: The True Vision - Capture, Transmission and Display of 3D Video (3DTV-CON), 2012. - : IEEE. - 9781467349055 ; , s. 1-4
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Konferensbidrag (refereegranskat)abstract
- In this paper, we define volumetric depth confidence and propose a method to denoise this data by performing adaptive wavelet thresholding using three dimensional (3D) wavelet transforms. The depth information is relevant for emerging interactive multimedia applications such as 3D TV and free-viewpoint television (FTV). These emerging applications require high quality virtual view rendering to enable viewers to move freely in a dynamic real worldscene. Depth information of a real world scene from different viewpoints is used to render an arbitrary number of novel views. Usually, depth estimates of 3D object points from different viewpoints are inconsistent. This inconsistency of depth estimates affects the quality of view rendering negatively. Based on the superposition principle, we define a volumetric depth confidence description of the underlying geometry of natural 3D scenes by using these inconsistent depth estimates from different viewpoints. Our method denoises this noisy volumetric description, and with this, we enhance the quality of view rendering by up to 0.45 dB when compared to rendering with conventional MPEG depth maps.
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| 48. |
- Rana, Pravin Kumar, 1982-, et al.
(författare)
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A Variational Bayesian Inference Framework for Multiview Depth Image Enhancement
- 2012
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Ingår i: Proceedings - 2012 IEEE International Symposium on Multimedia, ISM 2012. - : IEEE. - 9780769548753 ; , s. 183-190
-
Konferensbidrag (refereegranskat)abstract
- In this paper, a general model-based framework for multiview depth image enhancement is proposed. Depth imagery plays a pivotal role in emerging free-viewpoint television. This technology requires high quality virtual view synthesis to enable viewers to move freely in a dynamic real world scene. Depth imagery of different viewpoints is used to synthesize an arbitrary number of novel views. Usually, the depth imagery is estimated individually by stereo-matching algorithms and, hence, shows lack of inter-view consistency. This inconsistency affects the quality of view synthesis negatively. This paper enhances the inter-view consistency of multiview depth imagery by using a variational Bayesian inference framework. First, our approach classifies the color information in the multiview color imagery. Second, using the resulting color clusters, we classify the corresponding depth values in the multiview depth imagery. Each clustered depth image is subject to further subclustering. Finally, the resulting mean of the sub-clusters is used to enhance the depth imagery at multiple viewpoints. Experiments show that our approach improves the quality of virtual views by up to 0.25 dB.
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| 49. |
- Rana, Pravin Kumar, 1982-, et al.
(författare)
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Depth consistency testing for improved view interpolation
- 2010
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Ingår i: <em></em>. - 9781424481118 ; , s. 384-389
-
Konferensbidrag (refereegranskat)abstract
- Multiview video will play a pivotal role in the next generation visual communication media services like three-dimensional (3D) television and free-viewpoint television. These advanced media services provide natural 3D impressions and enable viewers to move freely in a dynamic real world scene by changing the viewpoint. High quality virtual view interpolation is required to support free viewpoint viewing. Usually, depth maps of different viewpoints are used to reconstruct a novel view. As these depth maps are usually estimated individually by stereo-matching algorithms, they have very weak spatial consistency. The inconsistency of depth maps affects the quality of view interpolation. In this paper, we propose a method for depth consistency testing to improve view interpolation. The method addresses the problem by warping more than two depth maps from multiple reference viewpoints to the virtual viewpoint. We test the consistency among warped depth values and improve the depth value information of the virtual view. With that, we enhance the quality of the interpolated virtual view.
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| 50. |
- Rana, Pravin Kumar, 1982-, et al.
(författare)
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Depth Pixel Clustering for Consistency Testing of Multiview Depth
- 2012
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Ingår i: European Signal Processing Conference. - 9781467310680 ; , s. 1119-1123
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Konferensbidrag (refereegranskat)abstract
- This paper proposes a clustering algorithm of depth pixels for consistency testing of multiview depth imagery. The testing addresses the inconsistencies among estimated depth maps of real world scenes by validating depth pixel connection evidence based on a hard connection threshold. With the proposed algorithm, we test the consistency among depth values generated from multiple depth observations using cluster adaptive connection thresholds. The connection threshold is based on statistical properties of depth pixels in a cluster or sub-cluster. This approach can improve the depth information of real world scenes at a given viewpoint. This allows us to enhance the quality of synthesized virtual views when compared to depth maps obtained by using fixed thresholding. Depth-image-based virtual view synthesis is widely used for upcoming multimedia services like three-dimensional television and free-viewpoint television.
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