218 research outputs found
Optimized Data Representation for Interactive Multiview Navigation
In contrary to traditional media streaming services where a unique media
content is delivered to different users, interactive multiview navigation
applications enable users to choose their own viewpoints and freely navigate in
a 3-D scene. The interactivity brings new challenges in addition to the
classical rate-distortion trade-off, which considers only the compression
performance and viewing quality. On the one hand, interactivity necessitates
sufficient viewpoints for richer navigation; on the other hand, it requires to
provide low bandwidth and delay costs for smooth navigation during view
transitions. In this paper, we formally describe the novel trade-offs posed by
the navigation interactivity and classical rate-distortion criterion. Based on
an original formulation, we look for the optimal design of the data
representation by introducing novel rate and distortion models and practical
solving algorithms. Experiments show that the proposed data representation
method outperforms the baseline solution by providing lower resource
consumptions and higher visual quality in all navigation configurations, which
certainly confirms the potential of the proposed data representation in
practical interactive navigation systems
Navigation domain representation for interactive multiview imaging
Enabling users to interactively navigate through different viewpoints of a
static scene is a new interesting functionality in 3D streaming systems. While
it opens exciting perspectives towards rich multimedia applications, it
requires the design of novel representations and coding techniques in order to
solve the new challenges imposed by interactive navigation. Interactivity
clearly brings new design constraints: the encoder is unaware of the exact
decoding process, while the decoder has to reconstruct information from
incomplete subsets of data since the server can generally not transmit images
for all possible viewpoints due to resource constrains. In this paper, we
propose a novel multiview data representation that permits to satisfy bandwidth
and storage constraints in an interactive multiview streaming system. In
particular, we partition the multiview navigation domain into segments, each of
which is described by a reference image and some auxiliary information. The
auxiliary information enables the client to recreate any viewpoint in the
navigation segment via view synthesis. The decoder is then able to navigate
freely in the segment without further data request to the server; it requests
additional data only when it moves to a different segment. We discuss the
benefits of this novel representation in interactive navigation systems and
further propose a method to optimize the partitioning of the navigation domain
into independent segments, under bandwidth and storage constraints.
Experimental results confirm the potential of the proposed representation;
namely, our system leads to similar compression performance as classical
inter-view coding, while it provides the high level of flexibility that is
required for interactive streaming. Hence, our new framework represents a
promising solution for 3D data representation in novel interactive multimedia
services
Dünaamiline kiiruse jaotamine interaktiivses mitmevaatelises video vaatevahetuse ennustamineses
In Interactive Multi-View Video (IMVV), the video has been captured by numbers of
cameras positioned in array and transmitted those camera views to users. The user can
interact with the transmitted video content by choosing viewpoints (views from different
cameras in the array) with the expectation of minimum transmission delay while
changing among various views. View switching delay is one of the primary concern that
is dealt in this thesis work, where the contribution is to minimize the transmission delay
of new view switch frame through a novel process of selection of the predicted view
and compression considering the transmission efficiency. Mainly considered a realtime
IMVV streaming, and the view switch is mapped as discrete Markov chain, where
the transition probability is derived using Zipf distribution, which provides information
regarding view switch prediction. To eliminate Round-Trip Time (RTT) transmission
delay, Quantization Parameters (QP) are adaptively allocated to the remaining redundant
transmitted frames to maintain view switching time minimum, trading off with
the quality of the video till RTT time-span. The experimental results of the proposed
method show superior performance on PSNR and view switching delay for better viewing quality over the existing methods
In-Network View Synthesis for Interactive Multiview Video Systems
To enable Interactive multiview video systems with a minimum view-switching
delay, multiple camera views are sent to the users, which are used as reference
images to synthesize additional virtual views via depth-image-based rendering.
In practice, bandwidth constraints may however restrict the number of reference
views sent to clients per time unit, which may in turn limit the quality of the
synthesized viewpoints. We argue that the reference view selection should
ideally be performed close to the users, and we study the problem of in-network
reference view synthesis such that the navigation quality is maximized at the
clients. We consider a distributed cloud network architecture where data stored
in a main cloud is delivered to end users with the help of cloudlets, i.e.,
resource-rich proxies close to the users. In order to satisfy last-hop
bandwidth constraints from the cloudlet to the users, a cloudlet re-samples
viewpoints of the 3D scene into a discrete set of views (combination of
received camera views and virtual views synthesized) to be used as reference
for the synthesis of additional virtual views at the client. This in-network
synthesis leads to better viewpoint sampling given a bandwidth constraint
compared to simple selection of camera views, but it may however carry a
distortion penalty in the cloudlet-synthesized reference views. We therefore
cast a new reference view selection problem where the best subset of views is
defined as the one minimizing the distortion over a view navigation window
defined by the user under some transmission bandwidth constraints. We show that
the view selection problem is NP-hard, and propose an effective polynomial time
algorithm using dynamic programming to solve the optimization problem.
Simulation results finally confirm the performance gain offered by virtual view
synthesis in the network
A modified multiview video streaming system using 3-tier architecture
In this paper, we present a modified inter-view prediction Multiview Video Coding (MVC) scheme from the perspective of viewer's interactivity. When a viewer requests some view(s), our scheme leads to lower transmission bit-rate. We develop an interactive multiview video streaming system exploiting that modified MVC scheme. Conventional interactive multiview video systems require high bandwidth due to redundant data being transferred. With real data test sequences, clear improvements are shown using the proposed interactive multiview video system compared to competing ones in terms of the average transmission bit-rate and storage size of the decoded (i.e., transferred) data with comparable rate-distortion
Optimized Packet Scheduling in Multiview Video Navigation Systems
In multiview video systems, multiple cameras generally acquire the same scene
from different perspectives, such that users have the possibility to select
their preferred viewpoint. This results in large amounts of highly redundant
data, which needs to be properly handled during encoding and transmission over
resource-constrained channels. In this work, we study coding and transmission
strategies in multicamera systems, where correlated sources send data through a
bottleneck channel to a central server, which eventually transmits views to
different interactive users. We propose a dynamic correlation-aware packet
scheduling optimization under delay, bandwidth, and interactivity constraints.
The optimization relies both on a novel rate-distortion model, which captures
the importance of each view in the 3D scene reconstruction, and on an objective
function that optimizes resources based on a client navigation model. The
latter takes into account the distortion experienced by interactive clients as
well as the distortion variations that might be observed by clients during
multiview navigation. We solve the scheduling problem with a novel
trellis-based solution, which permits to formally decompose the multivariate
optimization problem thereby significantly reducing the computation complexity.
Simulation results show the gain of the proposed algorithm compared to baseline
scheduling policies. More in details, we show the gain offered by our dynamic
scheduling policy compared to static camera allocation strategies and to
schemes with constant coding strategies. Finally, we show that the best
scheduling policy consistently adapts to the most likely user navigation path
and that it minimizes distortion variations that can be very disturbing for
users in traditional navigation systems
Multi-View Video Packet Scheduling
In multiview applications, multiple cameras acquire the same scene from
different viewpoints and generally produce correlated video streams. This
results in large amounts of highly redundant data. In order to save resources,
it is critical to handle properly this correlation during encoding and
transmission of the multiview data. In this work, we propose a
correlation-aware packet scheduling algorithm for multi-camera networks, where
information from all cameras are transmitted over a bottleneck channel to
clients that reconstruct the multiview images. The scheduling algorithm relies
on a new rate-distortion model that captures the importance of each view in the
scene reconstruction. We propose a problem formulation for the optimization of
the packet scheduling policies, which adapt to variations in the scene content.
Then, we design a low complexity scheduling algorithm based on a trellis search
that selects the subset of candidate packets to be transmitted towards
effective multiview reconstruction at clients. Extensive simulation results
confirm the gain of our scheduling algorithm when inter-source correlation
information is used in the scheduler, compared to scheduling policies with no
information about the correlation or non-adaptive scheduling policies. We
finally show that increasing the optimization horizon in the packet scheduling
algorithm improves the transmission performance, especially in scenarios where
the level of correlation rapidly varies with time
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