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We investigate the problem of collaborative video streaming in overlay networks. We exploit path and source diversity, as well as basic processing capabilities of network,nodes in order to increase the overall throughput and improve,the... more
We investigate the problem of collaborative video streaming in overlay networks. We exploit path and source diversity, as well as basic processing capabilities of network,nodes in order to increase the overall throughput and improve,the video quality at the clients. We consider an architecture where,several streaming servers simultaneously deliver video information to a set of clients. The servers apply Raptor
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We present a novel scheme for the transmission of H.264/AVC video streams over packet loss networks. The proposed scheme exploits the error resilient features of H.264/AVC codec and employs Reed-Solomon codes to protect effectively the... more
We present a novel scheme for the transmission of H.264/AVC video streams over packet loss networks. The proposed scheme exploits the error resilient features of H.264/AVC codec and employs Reed-Solomon codes to protect effectively the streams. A novel technique for adaptive classification of macroblocks into three slice groups using Flexible Macroblock Ordering is also proposed. The optimal classification of mac-
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In this paper, we investigate the problem of recovering source information from an incomplete set of network coded data with help of prior information about the sources. We study the theoretical performance of such systems under maximum a... more
In this paper, we investigate the problem of recovering source information from an incomplete set of network coded data with help of prior information about the sources. We study the theoretical performance of such systems under maximum a posteriori (MAP) decoding and examine the influence of the data priors and, in particular, source correlation on the decoding performance. We also propose a low complexity iterative decoding algorithm based on message passing for decoding the network coded data. The algorithm operates on a graph that captures the network coding constraints, while the knowledge about the source correlation is directly incorporated in the messages exchanged over the graph. We test the proposed method on both synthetic data and correlated image sequences and demonstrate that the prior knowledge about the statistical properties of the sources can be effectively exploited at the decoder in order to provide a good reconstruction of the transmitted data.
This paper addresses the problem of the distributed delivery of correlated data sources with help of network coding. Network coding provides an alternative to routing algorithms and offers improved system performance, robustness and... more
This paper addresses the problem of the distributed delivery of correlated data sources with help of network coding. Network coding provides an alternative to routing algorithms and offers improved system performance, robustness and throughput, with no need of deploying sophisticated routing strategies. However, the performance is directly driven by the number of innovative data packets that reach the receiver. If the number of received innovative data packets is significantly small, the decoder cannot perfectly recover the transmitted information. However, we show that the correlation between the data sources can be used at decoder for effective approximate decoding. We analytically investigate the impact of the network coding algorithm, and in particular, of the size of finite fields on the decoding performance. Then, we determine an optimal field size that minimizes the expected decoding error, which represents a trade-off between quantization of the source data and probability o...
We consider an interactive multiview video streaming (IMVS) system where clients select their preferred viewpoint in a given navigation window. To provide high quality IMVS, many high quality views should be transmitted to the clients.... more
We consider an interactive multiview video streaming (IMVS) system where clients select their preferred viewpoint in a given navigation window. To provide high quality IMVS, many high quality views should be transmitted to the clients. However, this is not always possible due to the limited and heterogeneous capabilities of the clients. In this paper, we propose a novel adaptive IMVS solution based on a layered multiview representation where camera views are organized into layered subsets to match the different clients constraints. We formulate an optimization problem for the joint selection of the views subsets and their encoding rates. Then, we propose an optimal and a reduced computational complexity greedy algorithms, both based on dynamic-programming. Simulation results show the good performance of our novel algorithms compared to a baseline algorithm, proving that an effective IMVS adaptive solution should consider the scene content and the client capabilities and their prefer...
Network coding has recently emerged as an alternative to traditional routing algorithms in communication systems. In network coding, the network nodes can combine the packets they receive before forwarding them to the neighbouring nodes.... more
Network coding has recently emerged as an alternative to traditional routing algorithms in communication systems. In network coding, the network nodes can combine the packets they receive before forwarding them to the neighbouring nodes. Intensive research efforts have demonstrated that such a processing in the network nodes can provide advantages in terms of throughput or robustness. These potentials, combined with
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This paper addresses the problem of frame interpolation for Wyner-Ziv video coding. A novel frame interpolation method based on block-adaptive matching algorithm for motion estimation is presented. This scheme enables block size... more
This paper addresses the problem of frame interpolation for Wyner-Ziv video coding. A novel frame interpolation method based on block-adaptive matching algorithm for motion estimation is presented. This scheme enables block size adaptation to local activity within frames using block merging and splitting techniques. The efficiency of the proposed method is evaluated in a Wyner-Ziv video coding scheme. The experimental results demonstrate the superiority of the proposed method over existing frame interpolation techniques.
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The decoding of convolutional codes using the List Viterbi algorithm is proposed for data hiding applications. The per- formance of this technique is evaluated for wavelet-domain information hiding and is shown in many cases to be ad-... more
The decoding of convolutional codes using the List Viterbi algorithm is proposed for data hiding applications. The per- formance of this technique is evaluated for wavelet-domain information hiding and is shown in many cases to be ad- vantageous in comparison to the widely used Turbo codes for efficient extraction of information embedded in digital images.
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We present a system for collaborative video streaming in wired overlay networks. We propose a scheme that builds on both rateless codes and network coding in order to improve the system throughput and the video quality at clients. Our... more
We present a system for collaborative video streaming in wired overlay networks. We propose a scheme that builds on both rateless codes and network coding in order to improve the system throughput and the video quality at clients. Our hybrid coding algorithm permits to efficiently exploit the available source and path diversity without the need for expensive routing nor scheduling algorithms. We consider specifically an architecture where multiple streaming servers simultaneously deliver video information to a set of clients. The servers apply Raptor coding on the video packets for error resiliency, and the overlay nodes selectively combine the Raptor coded video packets in order to increase the packet diversity in the system. We analyze the performance of selective network coding and describe its application to practical video streaming systems. We further compute an effective source and channel rate allocation in our collaborative streaming system. We estimate the expected symbol diversity at clients with respect to the coding choices. Then we cast a minmax quality optimization problem that is solved by a low-cost bisection based method. The experimental evaluation demonstrates that our system typically outperforms Raptor video streaming systems that do not use network coding as well as systems that perform decoding and encoding in the network nodes. Finally, our solution has a low complexity and only requires small buffers in the network coding nodes, which are certainly two important advantages toward deployment in practical streaming systems.
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In this paper, the sequential decoding of convolutional codes is proposed for data hiding in the wavelet domain. The performance of this technique is evaluated for data hiding in JPEG2000 images and is shown to be advantageous in... more
In this paper, the sequential decoding of convolutional codes is proposed for data hiding in the wavelet domain. The performance of this technique is evaluated for data hiding in JPEG2000 images and is shown to be advantageous in comparison to other methods for the embedding/extraction of information in digital images.
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ABSTRACT In free viewpoint applications, the images are captured by an array of cameras that acquire a scene of interest from different perspectives. Any intermediate viewpoint not included in the camera array can be virtually synthesized... more
ABSTRACT In free viewpoint applications, the images are captured by an array of cameras that acquire a scene of interest from different perspectives. Any intermediate viewpoint not included in the camera array can be virtually synthesized by the decoder, at a quality that depends on the distance between the virtual view and the camera views available at decoder. Hence, it is beneficial for any user to receive camera views that are close to each other for synthesis. This is however not always feasible in bandwidth-limited overlay networks, where every node may ask for different camera views. In this work, we propose an optimized delivery strategy for free viewpoint streaming over overlay networks. We introduce the concept of layered quality-of-experience (QoE), which describes the level of interactivity offered to clients. Based on these levels of QoE, camera views are organized into layered subsets. These subsets are then delivered to clients through a prioritized network coding streaming scheme, which accommodates for the network and clients heterogeneity and effectively exploit the resources of the overlay network. Simulation results show that, in a scenario with limited bandwidth or channel reliability, the proposed method outperforms baseline network coding approaches, where the different levels of QoE are not taken into account in the delivery strategy optimization.
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ABSTRACT In this paper, we consider the problem of decoding network coded correlated data when the decoder does not receive sufficient information for exact decoding. We propose an iterative decoding algorithm based on belief propagation... more
ABSTRACT In this paper, we consider the problem of decoding network coded correlated data when the decoder does not receive sufficient information for exact decoding. We propose an iterative decoding algorithm based on belief propagation that efficiently exploits the data correlation and provides approximate reconstruction of the sources when conventional decoding methods fail. The dependencies among the sources are captured by means of a factor graph. A simple noise model is used in order to describe the pairwise source relationships. The decoding decision is based on MAP estimates that are inferred by message passing over the underlying factor graph. Performance evaluation of the proposed decoding algorithm on correlated data sets consisting of video sequences confirms the efficiency of the proposed algorithm. Simulation results show that high quality reconstruction can be achieved even if significant amount of network coded information is missing at the decoder.
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ABSTRACT Growth codes are a subclass of Rateless codes that have found interesting applications in data dissemination problems. Compared to other Rateless and conventional channel codes, Growth codes show improved intermediate performance... more
ABSTRACT Growth codes are a subclass of Rateless codes that have found interesting applications in data dissemination problems. Compared to other Rateless and conventional channel codes, Growth codes show improved intermediate performance which is particularly useful in applications where partial data presents some utility. In this paper, we investigate the asymptotic performance of Growth codes using the Wormald method, which was proposed for studying the Peeling Decoder of LDPC and LDGM codes. Compared to previous works, the Wormald differential equations are set on nodes' perspective which enables a numerical solution to the computation of the expected asymptotic decoding performance of Growth codes. Our framework is appropriate for any class of Rateless codes that does not include a precoding step. We further study the performance of Growth codes with moderate and large size codeblocks through simulations and we use the generalized logistic function to model the decoding probability. We then exploit the decoding probability model in an illustrative application of Growth codes to error resilient video transmission. The video transmission problem is cast as a joint source and channel rate allocation problem that is shown to be convex with respect to the channel rate. This illustrative application permits to highlight the main advantage of Growth codes, namely improved performance in the intermediate loss region.
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... 105E065. AS Tan is supported in part by graduate scholarship of TUBITAK. ... task. In this work, a two-step optimization procedure, which iteratively determines the packet classification and the chan-nel protection is proposed. ...
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ABSTRACT Ultrasound imaging allows the evaluation of the degree of emergency of a patient. However, in many situations no experienced sonographer is available to perform such echography. To cope with this issue, the OTELO project “mObile... more
ABSTRACT Ultrasound imaging allows the evaluation of the degree of emergency of a patient. However, in many situations no experienced sonographer is available to perform such echography. To cope with this issue, the OTELO project “mObile Tele-Echography using an ultra-Light rObot” (OTELO) aims to develop a fully integrated end-to-end mobile tele-echography system using an ultralight, remotely controlled six degree-of-freedom (DOF) robot. In this context, this paper deals with the user interface environment of the OTELO system, composed by the following parts: an ultrasound video transmission system providing real-time images of the scanned area at each moment, an audio/video conference to communicate with the paramedical assistant and the patient, and finally a virtual reality environment, providing visual and haptic feedback to the expert, while capturing the expert's hand movements with a one-DOF hand free input device.
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Error-resilient techniques are proposed for the efficient transmission of still images and video over unreliable channels. The proposed techniques are applied in conjunction with multiresolution decomposition of images or video frames.... more
Error-resilient techniques are proposed for the efficient transmission of still images and video over unreliable channels. The proposed techniques are applied in conjunction with multiresolution decomposition of images or video frames. The resulting coders produce scalable bitstreams which can deliver very good quality over a variety of different bandwidths. The error-resilient structure of the stream endows the proposed systems with