30 research outputs found
On-the-Fly Coding for Real-Time Applications
Although ironically it does not offer any real-time guarantee, Internet is a popular solution to support multimedia time-constrained applications (e.g. VoIP, Video Conferencing, ...). Following this trend, this paper focuses on the performance of these applications by studying the benefit of using a novel reliability concept which aims at signifi- cantly improving the performance of these time constrained applications over lossy best-effort networks. This reliability mechanism emerged from several recent works from both network and coding theories. Its principle is to integrate feedbacks in an on-the fly coding scheme in order to optimize the trade-off âpacket decoding delayâ vs âthroughputâ. We present the first evaluations of this mechanism for VoIP and video-conferencing applications for various erasure channels. Compared to classic block-based erasure codes, the results show significant gains in terms of quality observed by the user for both applications
IP-Level Satellite Link Emulation with KauNet
Distributed applications and transport protocols communicating over a satellite link may react very strongly to conditions specific to that kind of link. Providing a evaluation framework to allow tests of real implementations of such software in that context is quite a challenging task. In this paper we demonstrate how the use of the general-purpose KauNet IP-level emulator combined with satellite-specific packet loss patterns can help by reproducing losses and delays experienced on a satellite link with a simple Ethernet LAN setup. Such a platform is an essential tool for developers performing continuous testing as they provide new features for e.g. video codecs or transport-level software like DCCP and its congestion control components
Contributions à la fiabilisation du transport de la vidéo
Les applications vidĂ©o rencontrent un franc succes dans les nouveaux rĂ©seaux de communication. Leur utilisation dans des contextes de plus en plus difficiles : rĂ©seaux de paquets non fiables (internet), diffusion vers des rĂ©cepteurs mobiles via des canaux sans fil, ont requis le dĂ©veloppement de nouvelles solutions plus efficaces et mieux adaptĂ©es. Les travaux de cette thĂšse sont une tentative de rĂ©ponse Ă ces besoins. Les solutions qui ont Ă©tĂ© dĂ©veloppĂ©es peuvent ĂȘtre regroupĂ©es en deux ensembles : des solutions issues de travaux nouveaux dĂ©veloppĂ©s dans un contexte d'utilisation ordinaire et des solutions issues de l'amĂ©lioration et l'optimisation de travaux existants dĂ©veloppĂ©s pour des contextes extrĂȘmes.Le canal de Bernoulli a reprĂ©sentĂ© pour nous le cadre de travail pour le dĂ©veloppement des nouvelles solutions. Ainsi pour les applications de diffusion vidĂ©o, nous avons ciblĂ© la protection inĂ©gale et avons dĂ©veloppĂ© un mĂ©canisme Ă protection inĂ©gale des donnĂ©es vidĂ©o (DA-UEP). Ce mĂ©canisme se situe Ă proximitĂ© de la source vidĂ©o et adapte le niveau de protection des donnĂ©es Ă leur degrĂ© d'importance. Son originalitĂ© rĂ©side dans sa maniĂšre d'intĂ©grer la particularitĂ© d'interdĂ©pendances des donnĂ©es vidĂ©o dans le gĂ©nĂ©rateur de la protection inĂ©gale. Dans un travail d'approfondissement et d'exploration, nous avons combinĂ© la protection inĂ©gale des couches hautes produite par DA-UEP avec de la protection inĂ©gale de la couche physique produite par de la modulation hiĂ©rarchique. L'optimisation de ce systĂšme a permis d'obtenir des gains significatifs et a validĂ© le bien fondĂ© de cette piste de recherche. Pour les communications vidĂ©o interactives, nous avons Ă©valuĂ© les performances du mĂ©canisme Tetrys pour les communications vidĂ©o. Ce mĂ©canisme de codage Ă la volĂ©e avec intĂ©gration des acquittements a permis d'obtenir des rĂ©sultats Ă la hauteur de ceux obtenus par la protection inĂ©gale dans un cadre de diffusion. Ces rĂ©sultats ont aussi permis de mettre en avant tout le potentiel de ce mĂ©canisme.
Pour les canaux satellites mobiles, nous nous sommes intéressés à la diffusion vidéo vers des récepteurs mobiles. Dans ce cadre, nous avons évalué des mécanismes tels que les codes correcteurs d'erreurs, les entrelaceurs de la couche physique et de la couche liaison et les codes à effacement de niveau intermédiaire. Nous avons travaillé sur un canal réaliste en prenant en compte les contraintes pratiques telles que les temps de zapping et la vitesse de déplacement des récepteurs. Nous avons révélé les relations qui existent entre vitesse de déplacement, étalement spatial et qualité de réception. Ainsi, nous avons pu mettre en évidence les combinaisons de mécanismes qui permettent d'obtenir les meilleurs résultats en termes de fiabilité et de temps de zapping dans ce contexte particulier. ABSTRACT : Video applications are growing more and more successful in the new communication networks. Their utilization in growing harder context as lossy packet network (Interne), satellitemobile broadcasting wireless channel, call for the developments of more ecient and well adapted solutions. The work done in this thesis is an attempt to answer those new needs. The proposed solutions can be grouped into two sets : solutions based on new works developed for medium context and solutions based on the improvement and optimization of existing works developed for extremes contexts. The Bernoulli channel represented the working environment to develop new solutions. So for video streaming application, we targeted unequal protection mechanisms and developed dependency-aware unequal protection codes (DA-UEP). This mechanism is located near the source application and adapt the protection level to the importance of the data. Its originality comes from its ability to integrate video data dependencies into the protection generator. In a forward work of improvement and exploration, we combined DA-UEP unequal protection from high layers with hierarchical-modulation unequal protection from lower layer. The system optimization achieves substantial gains and validate the righteous of this research area. For conversational video applications, we evaluated the performances of Tetrys in the video communication context. This On-the-y coding mechanism with acknowledgment integration achieves performances as high as those obtained by unequal protection in streaming context. Those performances also advances the high potential of this mechanism. The land mobile satellite channels represented the working environment to improve and optimize existing solutions. We particulary focus on satellite to mobile video broadcasting applications. In this context, we evaluated mechanisms such as forward errors correcting codes (FEC), data interleaving at physical or link layers and forward erasures correcting codes at intermediates layers. The evaluation is made on a realistic satellite channel and takes into account practical constraints such as the maximum zapping time and the user mobility at several speeds. We reveal the existing relations between user velocity, data spreading and reception quality. Consequently, We identied the combinations of mechanisms that give the best performance in terms of reliability and zapping time in this particular framework
Dependency-aware unequal erasure protection codes
Classical unequal erasure protection schemes split data to be protected into classes which are encoded independently. The unequal protection scheme presented in this paper is based on an erasure code which encodes all the data together according to the existing dependencies. A simple algorithm generates dynamically the generator matrix of the erasure code according to the packets streams structure, i.e., the dependencies between the packets, and the rate of the code. This proposed erasure code was applied to a packetized MPEG4 stream transmitted over a packet erasure channel and compared with other classical protection schemes in terms of PSNR and MOS. It is shown that the proposed code allows keeping a high video quality-level in a larger packet loss rate range than the other protection schemes
Cross-layer optimization of unequal protected layered video over hierarchical modulation
Abstract-unequal protection mechanisms have been proposed at several layers in order to improve the reliability of multimedia contents, especially for video data. The paper aims at implementing a multi-layer unequal protection scheme, which is based on a Physical-Transport-Application cross-layer design. Hierarchical modulation, in the physical layer, has been demonstrated to increase the overall user capacity of a wireless communications. On the other hand, unequal erasure protection codes at the transport layer turned out to be an efficient method to protect video data generated by the application layer by exploiting their intrinsic properties. In this paper, the two techniques are jointly optimized in order to enable recovering lost data in case the protection is performed separately. We show that the cross-layer design proposed herein outperforms the performance of hierarchical modulation and unequal erasure codes taken independently
Evaluation of cross-layer reliability mechanisms for satellite digital multimedia broadcast
This paper presents a study of some reliability mechanisms which may be put at work in the context of Satellite Digital Multimedia Broadcasting (SDMB) to mobile devices such as handheld phones. These mechanisms include error correcting codes, interleaving at the physical layer, erasure codes at
intermediate layers and error concealment on the video decoder. The evaluation is made on a realistic satellite channel and takes into account practical constraints such as the maximum zapping time and the user mobility at several speeds. The evaluation is done by simulating different scenarii with complete protocol stacks. The simulations indicate that, under the assumptions taken here, the scenario using highly compressed video protected by erasure codes at intermediate layers seems to be the best solution
on this kind of channel
Tetrys : Un mécanisme de fiabilisation polyvalent
Actuellement, une succession dâerreurs qui ne peut ĂȘtre masquĂ©e par le mĂ©canisme de fiabilisation (code Ă effacement) doit attendre au minimum un RTT pour ĂȘtre corrigĂ©e, ce qui nâest souvent pas satisfaisant pour les application temps-rĂ©el. Les concepts apportĂ©s par la thĂ©orie du codage rĂ©seau (Network Coding) permettent aujourdâhui de combler le fossĂ© entre fiabilisation et fiabilitĂ© totale en s'abstrayant du concept dâARQ. Cet article prĂ©sente un mĂ©canisme innovant nommĂ© Tetrys dont lâune des caractĂ©ristiques est de pouvoir reconstruire les pertes dans un temps paramĂ©trable et indĂ©pendant du RTT. A notre meilleure connaissance, c'est la premiĂšre fois que les propriĂ©tĂ©s temps rĂ©el d'un tel mĂ©canisme sont Ă©noncĂ©es et Ă©tudiĂ©es. Intuitivement, les applications ciblĂ©es sont celles nĂ©cessitant une fiabilitĂ© totale avec contrainte de dĂ©lai. Il sâavĂšre quâĂ taux de redondance Ă©gal, des applications telles que la VoIP et la vidĂ©o-confĂ©rence sont bien plus performantes lorsque les flux sont protĂ©gĂ©s par le mĂ©canisme Tetrys que par les mĂ©canismes FEC ou H-ARQ classiques. AprĂšs un rapide rappel des points clĂ©s relatifs Ă FEC et H-ARQ, nous dĂ©crivons le principe de Tetrys et montrons son possible dĂ©ploiement. Nous comparons les performances de FEC, H-ARQ et Tetrys du point de vue applicatif Ă l'aide dâun prototype et suivant des mĂ©triques de dĂ©lai et dans le cadre de la VoIP, de qualitĂ© de la transmission (MOS)
Simple Reed-Solomon Forward Error Correction (FEC) Scheme for FECFRAME, RFC 6865
This document describes a fully-specified simple Forward Error Correction (FEC) scheme for Reed-Solomon codes over the finite field (also known as the Galois Field) GF(2^^m), with 2 <= m <= 16, that can be used to protect arbitrary media streams along the lines defined by FECFRAME. The Reed-Solomon codes considered have attractive properties, since they offer optimal protection against packet erasures and the source symbols are part of the encoding symbols, which can greatly simplify decoding. However, the price to pay is a limit on the maximum source block size, on the maximum number of encoding symbols, and a computational complexity higher than that of the Low-Density Parity Check (LDPC) codes, for instance
Contributions à la fiabilisation du transport de la vidéo
Les applications vidĂ©o rencontrent un franc succes dans les nouveaux rĂ©seaux de communication. Leur utilisation dans des contextes de plus en plus difficiles : rĂ©seaux de paquets non fiables (internet), diffusion vers des rĂ©cepteurs mobiles via des canaux sans fil, ont requis le dĂ©veloppement de nouvelles solutions plus efficaces et mieux adaptĂ©es. Les travaux de cette thĂšse sont une tentative de rĂ©ponse Ă ces besoins. Les solutions qui ont Ă©tĂ© dĂ©veloppĂ©es peuvent ĂȘtre regroupĂ©es en deux ensembles : des solutions issues de travaux nouveaux dĂ©veloppĂ©s dans un contexte d'utilisation ordinaire et des solutions issues de l'amĂ©lioration et l'optimisation de travaux existants dĂ©veloppĂ©s pour des contextes extrĂȘmes.Le canal de Bernoulli a reprĂ©sentĂ© pour nous le cadre de travail pour le dĂ©veloppement des nouvelles solutions. Ainsi pour les applications de diffusion vidĂ©o, nous avons ciblĂ© la protection inĂ©gale et avons dĂ©veloppĂ© un mĂ©canisme Ă protection inĂ©gale des donnĂ©es vidĂ©o (DA-UEP). Ce mĂ©canisme se situe Ă proximitĂ© de la source vidĂ©o et adapte le niveau de protection des donnĂ©es Ă leur degrĂ© d'importance. Son originalitĂ© rĂ©side dans sa maniĂšre d'intĂ©grer la particularitĂ© d'interdĂ©pendances des donnĂ©es vidĂ©o dans le gĂ©nĂ©rateur de la protection inĂ©gale. Dans un travail d'approfondissement et d'exploration, nous avons combinĂ© la protection inĂ©gale des couches hautes produite par DA-UEP avec de la protection inĂ©gale de la couche physique produite par de la modulation hiĂ©rarchique. L'optimisation de ce systĂšme a permis d'obtenir des gains significatifs et a validĂ© le bien fondĂ© de cette piste de recherche. Pour les communications vidĂ©o interactives, nous avons Ă©valuĂ© les performances du mĂ©canisme Tetrys pour les communications vidĂ©o. Ce mĂ©canisme de codage Ă la volĂ©e avec intĂ©gration des acquittements a permis d'obtenir des rĂ©sultats Ă la hauteur de ceux obtenus par la protection inĂ©gale dans un cadre de diffusion. Ces rĂ©sultats ont aussi permis de mettre en avant tout le potentiel de ce mĂ©canisme.Pour les canaux satellites mobiles, nous nous sommes intĂ©ressĂ©s Ă la diffusion vidĂ©o vers des rĂ©cepteurs mobiles. Dans ce cadre, nous avons Ă©valuĂ© des mĂ©canismes tels que les codes correcteurs d'erreurs, les entrelaceurs de la couche physique et de la couche liaison et les codes Ă effacement de niveau intermĂ©diaire. Nous avons travaillĂ© sur un canal rĂ©aliste en prenant en compte les contraintes pratiques telles que les temps de zapping et la vitesse de dĂ©placement des rĂ©cepteurs. Nous avons rĂ©vĂ©lĂ© les relations qui existent entre vitesse de dĂ©placement, Ă©talement spatial et qualitĂ© de rĂ©ception. Ainsi, nous avons pu mettre en Ă©vidence les combinaisons de mĂ©canismes qui permettent d'obtenir les meilleurs rĂ©sultats en termes de fiabilitĂ© et de temps de zapping dans ce contexte particulier.Video applications are growing more and more successful in the new communication networks. Their utilization in growing harder context as lossy packet network (Interne), satellitemobile broadcasting wireless channel, call for the developments of more ecient and well adapted solutions. The work done in this thesis is an attempt to answer those new needs. The proposed solutions can be grouped into two sets : solutions based on new works developed for medium context and solutions based on the improvement and optimization of existing works developed for extremes contexts. The Bernoulli channel represented the working environment to develop new solutions. So for video streaming application, we targeted unequal protection mechanisms and developed dependency-aware unequal protection codes (DA-UEP). This mechanism is located near the source application and adapt the protection level to the importance of the data. Its originality comes from its ability to integrate video data dependencies into the protection generator. In a forward work of improvement and exploration, we combined DA-UEP unequal protection from high layers with hierarchical-modulation unequal protection from lower layer. The system optimization achieves substantial gains and validate the righteous of this research area. For conversational video applications, we evaluated the performances of Tetrys in the video communication context. This On-the-y coding mechanism with acknowledgment integration achieves performances as high as those obtained by unequal protection in streaming context. Those performances also advances the high potential of this mechanism. The land mobile satellite channels represented the working environment to improve and optimize existing solutions. We particulary focus on satellite to mobile video broadcasting applications. In this context, we evaluated mechanisms such as forward errors correcting codes (FEC), data interleaving at physical or link layers and forward erasures correcting codes at intermediates layers. The evaluation is made on a realistic satellite channel and takes into account practical constraints such as the maximum zapping time and the user mobility at several speeds. We reveal the existing relations between user velocity, data spreading and reception quality. Consequently, We identied the combinations of mechanisms that give the best performance in terms of reliability and zapping time in this particular framework.TOULOUSE-INP (315552154) / SudocSudocFranceF
On-the-fly erasure coding for real-time video applications
This paper introduces a robust point-to-point transmission scheme: Tetrys,
that relies on a novel on-the-fly erasure coding concept which reduces the
delay for recovering lost data at the receiver side. In current erasure coding
schemes, the packets that are not rebuilt at the receiver side are either lost
or delayed by at least one RTT before transmission to the application. The
present contribution aims at demonstrating that Tetrys coding scheme can fill
the gap between real-time applications requirements and full reliability.
Indeed, we show that in several cases, Tetrys can recover lost packets below
one RTT over lossy and best-effort networks. We also show that Tetrys allows to
enable full reliability without delay compromise and as a result: significantly
improves the performance of time constrained applications. For instance, our
evaluations present that video-conferencing applications obtain a PSNR gain up
to 7dB compared to classic block-based erasure codes