394 research outputs found
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
Correlation-aware packet scheduling in multi-camera networks
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. © 2013 IEEE
QUALITY-DRIVEN CROSS LAYER DESIGN FOR MULTIMEDIA SECURITY OVER RESOURCE CONSTRAINED WIRELESS SENSOR NETWORKS
The strong need for security guarantee, e.g., integrity and authenticity, as well as privacy and confidentiality in wireless multimedia services has driven the development of an emerging research area in low cost Wireless Multimedia Sensor Networks (WMSNs). Unfortunately, those conventional encryption and authentication techniques cannot be applied directly to WMSNs due to inborn challenges such as extremely limited energy, computing and bandwidth resources. This dissertation provides a quality-driven security design and resource allocation framework for WMSNs. The contribution of this dissertation bridges the inter-disciplinary research gap between high layer multimedia signal processing and low layer computer networking. It formulates the generic problem of quality-driven multimedia resource allocation in WMSNs and proposes a cross layer solution. The fundamental methodologies of multimedia selective encryption and stream authentication, and their application to digital image or video compression standards are presented. New multimedia selective encryption and stream authentication schemes are proposed at application layer, which significantly reduces encryption/authentication complexity. In addition, network resource allocation methodologies at low layers are extensively studied. An unequal error protection-based network resource allocation scheme is proposed to achieve the best effort media quality with integrity and energy efficiency guarantee. Performance evaluation results show that this cross layer framework achieves considerable energy-quality-security gain by jointly designing multimedia selective encryption/multimedia stream authentication and communication resource allocation
Codage réseau pour des applications multimédias avancées
Network coding is a paradigm that allows an efficient use of the capacity of communication networks. It maximizes the throughput in a multi-hop multicast communication and reduces the delay. In this thesis, we focus our attention to the integration of the network coding framework to multimedia applications, and in particular to advanced systems that provide enhanced video services to the users. Our contributions concern several instances of advanced multimedia communications: an efficient framework for transmission of a live stream making joint use of network coding and multiple description coding; a novel transmission strategy for lossy wireless networks that guarantees a trade-off between loss resilience and short delay based on a rate-distortion optimized scheduling of the video frames, that we also extended to the case of interactive multi-view streaming; a distributed social caching system that, using network coding in conjunction with the knowledge of the users' preferences in terms of views, is able to select a replication scheme such that to provide a high video quality by accessing only other members of the social group without incurring the access cost associated with a connection to a central server and without exchanging large tables of metadata to keep track of the replicated parts; and, finally, a study on using blind source separation techniques to reduce the overhead incurred by network coding schemes based on error-detecting techniques such as parity coding and message digest generation. All our contributions are aimed at using network coding to enhance the quality of video transmission in terms of distortion and delay perceivedLe codage rĂ©seau est un paradigme qui permet une utilisation efficace du rĂ©seau. Il maximise le dĂ©bit dans un rĂ©seau multi-saut en multicast et rĂ©duit le retard. Dans cette thĂšse, nous concentrons notre attention sur lâintĂ©gration du codage rĂ©seau aux applications multimĂ©dias, et en particulier aux systĂšmes avancĂšs qui fournissent un service vidĂ©o amĂ©liorĂ© pour les utilisateurs. Nos contributions concernent plusieurs scĂ©narios : un cadre de fonctions efficace pour la transmission de flux en directe qui utilise Ă la fois le codage rĂ©seau et le codage par description multiple, une nouvelle stratĂ©gie de transmission pour les rĂ©seaux sans fil avec perte qui garantit un compromis entre la rĂ©silience vis-Ă -vis des perte et la reduction du retard sur la base dâune optimisation dĂ©bit-distorsion de l'ordonnancement des images vidĂ©o, que nous avons Ă©galement Ă©tendu au cas du streaming multi-vue interactive, un systĂšme replication sociale distribuĂ©e qui, en utilisant le rĂ©seau codage en relation et la connaissance des prĂ©fĂ©rences des utilisateurs en termes de vue, est en mesure de sĂ©lectionner un schĂ©ma de rĂ©plication capable de fournir une vidĂ©o de haute qualitĂ© en accĂ©dant seulement aux autres membres du groupe social, sans encourir le coĂ»t dâaccĂšs associĂ© Ă une connexion Ă un serveur central et sans Ă©changer des larges tables de mĂ©tadonnĂ©es pour tenir trace des Ă©lĂ©ments rĂ©pliquĂ©s, et, finalement, une Ă©tude sur lâutilisation de techniques de sĂ©paration aveugle de source -pour rĂ©duire lâoverhead encouru par les schĂ©mas de codage rĂ©seau- basĂ© sur des techniques de dĂ©tection dâerreur telles que le codage de paritĂ© et la gĂ©nĂ©ration de message digest
Transport Layer Optimizations for Heterogeneous Wireless Multimedia Networks
The explosive growth of the Internet during the last few years, has been propelled by the TCP/IP protocol suite and the best effort packet forwarding service. However, quality of service (QoS) is far from being a reality especially for multimedia services like video streaming and video conferencing. In the case of wireless and mobile networks, the problem becomes even worse due to the physics of the medium, resulting into further deterioration of the system performance.
Goal of this dissertation is the systematic development of comprehensive models that jointly characterize the performance of transport protocols and media delivery in heterogeneous wireless networks. At the core of our novel methodology, is the use of analytical models for driving the design of media transport algorithms, so that the delivery of conversational and non-interactive multimedia data is enhanced in terms of throughput, delay, and jitter. More speciffically, we develop analytical models that characterize the throughput and goodput of the transmission control protocol (TCP) and the transmission friendly rate control (TFRC) protocol, when CBR and VBR multimedia workloads are considered. Subsequently, we enhance the transport protocol models with new parameters that capture the playback buffer performance and the expected video distortion at the receiver. In this way a complete end-to-end model for media streaming is obtained. This model is used as a basis for a new algorithm for rate-distortion optimized mode selection in video streaming appli-
cations. As a next step, we extend the developed models for the aforementioned protocols, so that heterogeneous wireless networks can be accommodated. Subsequently, new algorithms are proposed in order to enhance the developed media streaming algorithms when heterogeneous wireless networks are also included. Finally, the aforementioned models and algorithms are extended for the case of concurrent multipath media transport over several hybrid wired/wireless links.Ph.D.Committee Chair: Vijay Madisetti; Committee Member: Raghupathy Sivakumar; Committee Member: Sudhakar Yalamanchili; Committee Member: Umakishore Ramachandran; Committee Member: Yucel Altunbasa
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
Multimedia over wireless ip networks:distortion estimation and applications.
2006/2007This thesis deals with multimedia communication over unreliable and resource
constrained IP-based packet-switched networks. The focus is on estimating, evaluating
and enhancing the quality of streaming media services with particular regard
to video services. The original contributions of this study involve mainly the
development of three video distortion estimation techniques and the successive
definition of some application scenarios used to demonstrate the benefits obtained
applying such algorithms. The material presented in this dissertation is the result
of the studies performed within the Telecommunication Group of the Department
of Electronic Engineering at the University of Trieste during the course of Doctorate
in Information Engineering.
In recent years multimedia communication over wired and wireless packet based
networks is exploding. Applications such as BitTorrent, music file sharing, multimedia
podcasting are the main source of all traffic on the Internet. Internet radio
for example is now evolving into peer to peer television such as CoolStreaming.
Moreover, web sites such as YouTube have made publishing videos on demand
available to anyone owning a home video camera. Another challenge in the multimedia
evolution is inside the house where videos are distributed over local WiFi
networks to many end devices around the house. More in general we are assisting
an all media over IP revolution, with radio, television, telephony and stored media
all being delivered over IP wired and wireless networks. All the presented applications
require an extreme high bandwidth and often a low delay especially for
interactive applications. Unfortunately the Internet and the wireless networks provide
only limited support for multimedia applications. Variations in network conditions
can have considerable consequences for real-time multimedia applications
and can lead to unsatisfactory user experience. In fact, multimedia applications
are usually delay sensitive, bandwidth intense and loss tolerant applications. In order
to overcame this limitations, efficient adaptation mechanism must be derived
to bridge the application requirements with the transport medium characteristics.
Several approaches have been proposed for the robust transmission of multimedia
packets; they range from source coding solutions to the addition of redundancy with forward error correction and retransmissions. Additionally, other techniques
are based on developing efficient QoS architectures at the network layer or at the
data link layer where routers or specialized devices apply different forwarding
behaviors to packets depending on the value of some field in the packet header.
Using such network architecture, video packets are assigned to classes, in order
to obtain a different treatment by the network; in particular, packets assigned to
the most privileged class will be lost with a very small probability, while packets
belonging to the lowest priority class will experience the traditional bestâeffort
service. But the key problem in this solution is how to assign optimally video
packets to the network classes. One way to perform the assignment is to proceed
on a packet-by-packet basis, to exploit the highly non-uniform distortion impact
of compressed video. Working on the distortion impact of each individual video
packet has been shown in recent years to deliver better performance than relying
on the average error sensitivity of each bitstream element. The distortion impact
of a video packet can be expressed as the distortion that would be introduced at
the receiver by its loss, taking into account the effects of both error concealment
and error propagation due to temporal prediction.
The estimation algorithms proposed in this dissertation are able to reproduce accurately
the distortion envelope deriving from multiple losses on the network and
the computational complexity required is negligible in respect to those proposed in
literature. Several tests are run to validate the distortion estimation algorithms and
to measure the influence of the main encoder-decoder settings. Different application scenarios are described and compared to demonstrate the benefits obtained
using the developed algorithms. The packet distortion impact is inserted in each
video packet and transmitted over the network where specialized agents manage
the video packets using the distortion information. In particular, the internal structure of the agents is modified to allow video packets prioritization using primarily
the distortion impact estimated by the transmitter. The results obtained will show
that, in each scenario, a significant improvement may be obtained with respect to
traditional transmission policies.
The thesis is organized in two parts. The first provides the background material
and represents the basics of the following arguments, while the other is dedicated
to the original results obtained during the research activity.
Referring to the first part in the first chapter it summarized an introduction to
the principles and challenges for the multimedia transmission over packet networks.
The most recent advances in video compression technologies are detailed
in the second chapter, focusing in particular on aspects that involve the resilience
to packet loss impairments. The third chapter deals with the main techniques
adopted to protect the multimedia flow for mitigating the packet loss corruption due to channel failures. The fourth chapter introduces the more recent advances in
network adaptive media transport detailing the techniques that prioritize the video
packet flow. The fifth chapter makes a literature review of the existing distortion
estimation techniques focusing mainly on their limitation aspects.
The second part of the thesis describes the original results obtained in the modelling
of the video distortion deriving from the transmission over an error prone
network. In particular, the sixth chapter presents three new distortion estimation
algorithms able to estimate the video quality and shows the results of some validation
tests performed to measure the accuracy of the employed algorithms. The
seventh chapter proposes different application scenarios where the developed algorithms may be used to enhance quickly the video quality at the end user side.
Finally, the eight chapter summarizes the thesis contributions and remarks the
most important conclusions. It also derives some directions for future improvements.
The intent of the entire work presented hereafter is to develop some video distortion
estimation algorithms able to predict the user quality deriving from the loss on the network as well as providing the results of some useful applications able to enhance the user experience during a video streaming session.Questa tesi di dottorato affronta il problema della trasmissione efficiente di contenuti
multimediali su reti a pacchetto inaffidabili e con limitate risorse di banda.
Lâobiettivo Ăš quello di ideare alcuni algoritmi in grado di predire lâandamento
della qualitĂ del video ricevuto da un utente e successivamente ideare alcune tecniche in grado di migliorare lâesperienza dellâutente finale nella fruizione dei servizi video. In particolare i contributi originali del presente lavoro riguardano lo sviluppo di algoritmi per la stima della distorsione e lâideazione di alcuni scenari applicativi in molto frequenti dove poter valutare i benefici ottenibili applicando gli algoritmi di stima.
I contributi presentati in questa tesi di dottorato sono il risultato degli studi compiuti con il gruppo di Telecomunicazioni del Dipartimento di Elettrotecnica Elettronica ed Informatica (DEEI) dellâUniversitĂ degli Studi di Trieste durante il corso di dottorato in Ingegneria dellâInformazione.
Negli ultimi anni la multimedialitĂ , diffusa sulle reti cablate e wireless, sta diventando
parte integrante del modo di utilizzare la rete diventando di fatto il fenomeno piĂč imponente. Applicazioni come BitTorrent, la condivisione di file musicali e multimediali e il podcasting ad esempio costituiscono una parte significativa del traffico attuale su Internet. Quelle che negli ultimi anni erano le prime radio che trsmettevano sulla rete oggi si stanno evolvendo nei sistemi peer
to peer per piĂč avanzati per la diffusione della TV via web come CoolStreaming.
Inoltre siti web come YouTube hanno costruito il loro business sulla memorizzazione/
distribuzione di video creati da chiunque abbia una semplice video camera.
Unâaltra caratteristica dellâimponente rivoluzione multimediale a cui stiamo
assistendo Ăš la diffusione dei video anche allâinterno delle case dove i contenuti
multimediali vengono distribuiti mediante delle reti wireless locali tra i vari dispositivi finali. Tuttâoggi Ăš in corso una rivoluzione della multimedialitĂ sulle reti
IP con le radio, i televisioni, la telefonia e tutti i video che devono essere distribuiti
sulle reti cablate e wireless verso utenti eterogenei. In generale la gran parte delle
applicazioni multimediali richiedono una banda elevata e dei ritardi molto contenuti specialmente se le applicazioni sono di tipo interattivo. Sfortunatamente le reti wireless e Internet piĂč in generale sono in grado di fornire un supporto limitato alle applicazioni multimediali. La variabilitĂ di banda, di ritardo e nella perdita possono avere conseguenze gravi sulla qualitĂ con cui viene ricevuto il video e questo puĂČ portare a una parziale insoddisfazione o addirittura alla rinuncia della fruizione da parte dellâutente finale.
Le applicazioni multimediali sono spesso sensibili al ritardo e con requisiti di
banda molto stringenti ma di fatto rimango tolleranti nei confronti delle perdite
che possono avvenire durante la trasmissione. Al fine di superare le limitazioni Ăš necessario sviluppare dei meccanismi di adattamento in grado di fare da ponte fra i requisiti delle applicazioni multimediali e le caratteristiche offerte dal livello di trasporto. Diversi approcci sono stati proposti in passato in letteratura per
migliorare la trasmissione dei pacchetti riducendo le perdite; gli approcci variano
dalle soluzioni di compressione efficiente allâaggiunta di ridondanza con tecniche
di forward error correction e ritrasmissioni. Altre tecniche si basano sulla creazione di architetture di rete complesse in grado di garantire la QoS a livello rete dove router oppure altri agenti specializzati applicano diverse politiche di gestione del traffico in base ai valori contenuti nei campi dei pacchetti. Mediante queste architetture il traffico video viene marcato con delle classi di prioritĂ al fine di creare una differenziazione nel traffico a livello rete; in particolare i pacchetti con i privilegi maggiori vengono assegnati alle classi di prioritĂ piĂč elevate e verranno persi con probabilitĂ molto bassa mentre i pacchetti appartenenti alle classi di prioritĂ inferiori saranno trattati alla stregua dei servizi di tipo best-effort. Uno dei principali problemi di questa soluzione riguarda come assegnare in maniera ottimale i singoli pacchetti video alle diverse classi di prioritĂ . Un modo per effettuare questa classificazione Ăš quello di procedere assegnando i pacchetti alle varie classi sulla base dellâimportanza che ogni pacchetto ha sulla qualitĂ finale.
Eâ stato dimostrato in numerosi lavori recenti che utilizzando come meccanismo
per lâadattamento lâimpatto sulla distorsione finale, porta significativi miglioramenti
rispetto alle tecniche che utilizzano come parametro la sensibilitĂ media del flusso nei confronti delle perdite. Lâimpatto che ogni pacchetto ha sulla qualitĂ puĂČ essere espresso come la distorsione che viene introdotta al ricevitore se il pacchetto viene perso tenendo in considerazione gli effetti del recupero (error concealment) e la propagazione dellâerrore (error propagation) caratteristica dei piĂč recenti codificatori video.
Gli algoritmi di stima della distorsione proposti in questa tesi sono in grado di riprodurre in maniera accurata lâinviluppo della distorsione derivante sia da perdite isolate che da perdite multiple nella rete con una complessitĂ computazionale minima se confrontata con le piĂč recenti tecniche di stima. Numerose prove sono stati effettuate al fine di validare gli algoritmi di stima e misurare lâinfluenza dei principali parametri di codifica e di decodifica. Al fine di enfatizzare i benefici ottenuti applicando gli algoritmi di stima della distorsione, durante la tesi verranno presentati alcuni scenari applicativi dove lâapplicazione degli algoritmi proposti migliora sensibilmente la qualitĂ finale percepita dagli utenti. Tali scenari verranno descritti, implementati e accuratamente valutati. In particolare, la distorsione stimata dal trasmettitore verrĂ incapsulata nei pacchetti video e, trasmessa
nella rete dove agenti specializzati potranno agevolmente estrarla e utilizzarla come meccanismo rate-distortion per privilegiare alcuni pacchetti a discapito di altri. In particolare la struttura interna di un agente (un router) verrĂ modificata al fine di consentire la differenziazione del traffico utilizzando lâinformazione dellâimpatto che ogni pacchetto ha sulla qualitĂ finale. I risultati ottenuti anche in termini di ridotta complessitĂ computazionale in ogni scenario applicativo proposto mettono in luce i benefici derivanti dallâimplementazione degli algoritmi di stima.
La presenti tesi di dottorato Ăš strutturata in due parti principali; la prima fornisce
il background e rappresenta la base per tutti gli argomenti trattati nel seguito mentre
la seconda parte Ăš dedicata ai contributi originali e ai risultati ottenuti durante
lâintera attivitĂ di ricerca.
In riferimento alla prima parte in particolare unâintroduzione ai principi e alle opportunitĂ offerte dalla diffusione dei servizi multimediali sulle reti a pacchetto
viene esposta nel primo capitolo. I progressi piĂč recenti nelle tecniche di compressione
video vengono esposti dettagliatamente nel secondo capitolo che si focalizza in particolare solo sugli aspetti che riguardano le tecniche per la mitigazione delle perdite. Il terzo capitolo introduce le principali tecniche per proteggere i flussi multimediali e ridurre le perdite causate dai fenomeni caratteristici del canale. Il quarto capitolo descrive i recenti avanzamenti nelle tecniche di network adaptive media transport illustrando i principali metodi utilizzati per differenziare il traffico video. Il quinto capitolo analizza i principali contributi nella letteratura sulle
tecniche di stima della distorsione e si focalizza in particolare sulle limitazioni dei metodi attuali.
La seconda parte della tesi descrive i contributi originali ottenuti nella modellizzazione della distorsione video derivante dalla trasmissione sulle reti con perdite.
In particolare il sesto capitolo presenta tre nuovi algoritmi in grado di riprodurre
fedelmente lâinviluppo della distorsione video. I numerosi test e risultati verranno
proposti al fine di validare gli algoritmi e misurare lâaccuratezza nella stima. Il settimo capitolo propone diversi scenari applicativi dove gli algoritmi sviluppati
possono essere utilizzati per migliorare in maniera significativa la qualitĂ percepita
dallâutente finale. Infine lâottavo capitolo sintetizza lâintero lavoro svolto e i principali risultati ottenuti. Nello stesso capitolo vengono inoltre descritti gli
sviluppi futuri dellâattivitĂ di ricerca.
Lâobiettivo dellâintero lavoro presentato Ăš quello di mostrare i benefici derivanti
dallâutilizzo di nuovi algoritmi per la stima della distorsione e di fornire alcuni
scenari applicativi di utilizzo.XIX Ciclo197
Quality of Experience and Adaptation Techniques for Multimedia Communications
The widespread use of multimedia services on the World Wide Web and the advances
in end-user portable devices have recently increased the user demands for better quality.
Moreover, providing these services seamlessly and ubiquitously on wireless networks and
with user mobility poses hard challenges. To meet these challenges and fulfill the end-user
requirements, suitable strategies need to be adopted at both application level and network
level. At the application level rate and quality have to be adapted to time-varying bandwidth
limitations, whereas on the network side a mechanism for efficient use of the network
resources has to be implemented, to provide a better end-user Quality of Experience (QoE)
through better Quality of Service (QoS). The work in this thesis addresses these issues by
first investigating multi-stream rate adaptation techniques for Scalable Video Coding (SVC)
applications aimed at a fair provision of QoE to end-users. Rate Distortion (R-D) models
for real-time and non real-time video streaming have been proposed and a rate adaptation
technique is also developed to minimize with fairness the distortion of multiple videos
with difference complexities. To provide resiliency against errors, the effect of Unequal
Error protection (UXP) based on Reed Solomon (RS) encoding with erasure correction has
been also included in the proposed R-D modelling. Moreover, to improve the support of
QoE at the network level for multimedia applications sensitive to delays, jitters and packet
drops, a technique to prioritise different traffic flows using specific QoS classes within an
intermediate DiffServ network integrated with a WiMAX access system is investigated.
Simulations were performed to test the network under different congestion scenarios
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