KEYWORDS: Video, Video compression, 3D video compression, JPEG2000, Video coding, Cameras, 3D image processing, Visualization, Computer programming, 3D displays
This paper presents a polygon soup representation for multiview data. Starting from a sequence of multi-view video plus depth (MVD) data, the proposed representation takes into account, in a unified manner, different issues such as compactness, compression, and intermediate view synthesis. The representation is built in two steps. First, a set of 3D quads is extracted using a quadtree decomposition of the depth maps. Second, a selective elimination of the quads is performed in order to reduce inter-view redundancies and thus provide a compact representation. Moreover, the proposed methodology for extracting the representation allows to reduce ghosting artifacts. Finally, an adapted compression technique is proposed that limits coding artifacts. The
results presented on two real sequences show that the proposed representation provides a good trade-off between
rendering quality and data compactness.
Autostereoscopic displays, allows one to see in 3D without glasses it requires at least 2 views and is often to maximize
user comfort. However multi-view capture is too complex for more than two cameras. Furthermore there is no
interoperability between 3D displays because each manufacturer has his specific input format. Thus we propose an
efficient automatic conversion from stereoscopic views to N views for a rendering on various autostereoscopic screens.
We describe the 2 main steps achieving automatic conversion from 2 to N views: disparity map estimation and view
interpolation. We use graph cut algorithm to compute the disparity map with occlusions detection. As the quality of the
disparity map is essential for interpolation we have developed an efficient management of occlusions through
morphological operation, outliers erasing and padding with the smallest disparity. We thus reconstruct details even for
concave objects. We also apply spatial regularization preserving borders and temporal smoothing with motion
compensation. Those processes improve considerably the quality of the depths map videos. Virtual views are then
generated through view morphing based on disparity to avoid 3D manipulation of data. Occlusion areas are managed and
irregular morphing pixel locations are resampled with a B-spline filter adapted to view interpolation.
Nowadays one of the most important issue linked to image transform is to take
into account the singularities of a signal which is organized on more than one
dimension. The best example is the wavelet transform extension to two
dimensional signal analysis. The drawback when one pass from a one dimensional
signal process to a two dimensional signal process by simply using separability of
wavelet transform is the over representation of irregularities in the wavelet
transform domain. In order to decrease this drawback, second generation wavelet
transform tries to take geometrical aspects of the image into account in the
analysis of the image (one can find examples with bandelets, curvelets,
ridgelets and others).
2 layers bandelets or first generation bandelets is among the first wavelet
transform which uses the flow to enhance the efficiency of the process. The
present proposition is mainly theoretical : we will propose now a pratical
interpretation of this work in order to make a new implementation of the
transform.
KEYWORDS: Digital watermarking, Distortion, Data hiding, Interference (communication), Discrete wavelet transforms, Performance modeling, Systems modeling, Signal to noise ratio, Data modeling, Demodulation
Data hiding has been mainly studied in the last years. Many applications are
targeted such as copy-rights management, meta-data embedding for rich-media
applications, ... In all these applications, it is crucial to estimate what
is the capacity of data hiding. Many works have then been made to study
watermarking performance considering data-hiding as a kind of channel
communication. However in all these studies, an assumption is made about the
perfect knowledge of all attacks parameters (may be known in advance or later
estimated with attacks modeling). More especially a malicious attacker may
biased its attack so that parameters estimation may not be perfect
(desynchronization in parameters). Furthermore, random geometrical attacks
for images such as proposed by Stirmark benchmark (more generally
desynchronization attacks) show that perfect synchronization may not also be
achievable. These last kind of attacks are actually the most effective and
lack of theoretical modeling for capacity estimation. We then propose a new
model for taking into account desynchronization phenomenon in data hiding
(coupled with degrading attacks - i.e. optimal SAWGN attacks). Further,
thanks to the use of game theory, we state bounds on the capacity that may be
obtained by data hiding systems when subject to desynchronization.
In the framework of multimedia communication over heterogeneous networks and variable quality of service, there are strong needs in robust and scalable video coding schemes. In order to reduce robustness problems of traditional finegrain scalable (FGS) video coding scheme, in this paper, we present a scalable texture-based video coding scheme for robust functionalities. To this purpose, the different frames are coded using an analysis-synthesis coding scheme with a progressive refinement layer. The robustness of the scheme is increased thanks to the ability to decode independently the
different frames of the video sequence.
In this paper, we present a technique for tracking non-rigid video objects in a sequence. It assumes that the object in the initial image has been previously defined by an object partition. Most of object tracking methods usually rely on the motion homogeneity of the object to be tracked. They do not assume that the selected objects present either motion or spatial homogeneity. When they assume these, they employed a spatial or temporal criterion separately to achieve the object tracking. Our proposed object tracking approach relies on the concept of backward partition projection using a likelihood joint spatial-temporal model to deal with occlusion, uncover areas and fast motion problems. Several examples in different scenarios are finally presented in order to demonstrate the performance of the proposed method.
KEYWORDS: Digital watermarking, Interference (communication), Signal to noise ratio, Distortion, Signal processing, Field emission displays, Forward error correction, Receivers, Magnesium, Multimedia
Nowadays, a popular method used for additive watermarking is wide spread spectrum. It consists in adding a spread signal into the host document. This signal is obtained by the sum of a set of carrier vectors, which are modulated by the bits to be embedded. To extract these embedded bits, weighted correlations between the watermarked document and the carriers are computed. Unfortunately, even without any attack, the obtained set of bits can be corrupted due to the interference with the host signal (host interference) and also due to the interference with the others carriers (inter-symbols interference (ISI) due to the non-orthogonality of the carriers). Some recent watermarking algorithms deal with host interference using side informed methods, but inter-symbols interference problem is still open. In this paper, we deal with interference cancellation methods, and we propose to consider ISI as side information and to integrate it into the host signal. This leads to a great improvement of extraction performance in term of signal-to-noise ratio and/or watermark robustness.
This article introduces a novel approach for scalable video coding based on an analysis-synthesis scheme. Active meshes are used to represent motion model, this permits to exploit temporal redundancy along motion trajectories in a video sequence using temporal wavelet transform. The use of 3D wavelets in the coding strategy provides natural scalability functionalities to the video coder. Furthermore, the analysis-synthesis scheme allows to decouple motion and texture and to code these informations separately. Motion can then be lossy coded, bitrates gain can be reported to texture coding. Because motion is lossy coded, a new quality criterion measured in the texture domain is then proposed. Finally, the proposed analysis-synthesis video scheme overcomes some of the limitations of existing video coding schemes using 3D wavelets, limitations due for the most part to the use of block-based motion model. Our video coding scheme performs as well as fully optimized H26Lv8, while providing a scalable bitstream.
In this paper, we present a mesh-based motion estimation scheme for image sequence. Nodal motion vectors optimization is performed by using a multi-resolution differential method. Because our final aim is mesh tracking throughout a video sequence with optimized reconstruction, neither backward tracking nor forward tracking is well suited. One motivation of our work is to take advantage of both forward tracking (which enables tracking) and backward tracking (for its efficiency) in a `backward in forward' method. For the optimization of the nodal motion vectors, we also propose a novel approach with multi-resolution and several hierarchy levels, which, in addition, makes it possible scalable representation. This is achieved with a progressive representation defined according to a rate distortion criterion. Results are presented to illustrate the proposed methods.
In this paper, we present a technique for tracking video objects in a sequence. The proposed technique is based on a backward projection technique. Since classical backward technique can be disturbed by occlusions and potential errors in spatial segmentation or motion estimation, we propose an extension to be backward projection technique in order to cope with these problems. Results obtained show the relevance of the proposed approach for various kind of tracked objects that can either be rigid or non-rigid.
Recent development in video coding research deals with the use of hierarchical and/or adaptative mesh for video representation. Concurrently, transmitted bit rates have to be reduced to adapt to the network available bandwidth. Some previous works deal with adaptative node sampling according to image content. However, adaptative hierarchical proposed approaches do not optimize a compromise between distortion and bitrate: the representation coding cost is often stated but not taken into account as a constraint. Compared to these methods, this paper proposes for considering an adaptative hierarchical mesh based representation whose splitting criterion optimizes both the coding cost and the image rendering. Jointly, node value optimization, adaptative quantization, cheap coding tree and a wavelet approach are presented. To illustrate our different proposed methods, experimental results are shown and compared to the JPEG picture coding format.
This article deals with the coding of segmentation maps used in region-based video coding. The scheme proposed to code these maps is based on an efficient edge representation using a graph of contours. Lossless and lossy compressions are then applied in order to have the cheapest representation. Lossless compression is based on Freeman chain-code associated to arithmetic coding, lossy compression is based on polygonal approximation of the contours controlled y a minimum description length criterion. We compare these two encoding schemes applied to different sequences and initial segmentation maps, 1.3 bits per contour points and 0.5 bits per contour points are obtained. Some discussions are also proposed to optimize the segmentation map and its accuracy.
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