Gabriel Hege

Peer-to-peer videoconferencing with H.264 software codec for mobiles

A rapidly growing number of carriers offer wireless video services to their customers, taking advantage of high quality video codecs implemented in dedicated hardware of selected mobile devices. In this paper we introduce a video conferencing software, which seamlessly integrates mobile with stationary users in a provider and device independent fashion. Innovations of this work are twofold. At first we report on a mobile realization of an H.264 video codec and its performance on a standard consumer Smartphone. Operating within the tight bounds of real-time compliance on mobiles, this software is an adapted version of a highly optimized H.264 codec. This DAVC codec, which we introduce along the line, significantly out-performs compatible H.264 realizations and allows for a scalable adaptation of its frame rate. In the second part we present a barrier-resistant peer-to-peer group communication scheme, which scales well for medium-size conferences and accounts for the heterogeneous nature of mobile and stationary participants. An outlook on mobility related group communication issues and future optimizations based on structured communication layers concludes the work.

AuthoCast—a mobility-compliant protocol framework for multicast sender authentication

Summary Mobility is considered a key technology of the next generation Internet and has been standardized within the IETF. Rapidly emerging multimedia group applications such as IPTV, MMORPGs and video conferencing increase the demand for mobile group communication, but a standard design of mobile multicast is still awaited. The open problem poses signicant operational and security challenges to the Internet infrastructure. This paper introduces a protocol framework for authenticating multicast sources and securing their mobility handovers. Its contribution is twofold: At rst, the current mobile multicast problem and solution spaces are summarized from the security perspective. At second, a solution to the mobile source authentication problem is presented that complies to IPv6 mobility signaling standards. Using an autonomously veriable one-way authentication based on cryptographically generated addresses, a common design is derived to jointly comply with the mobile any source and source specic multicast protocols that are currently proposed. This light-weight scheme smoothly extends the unicast enhanced route optimization for mobile IPv6 and adds only little overhead to multicast packets and protocol operations. Copyright c 2008 John Wiley & Sons, Ltd.

Connecting the worlds: Multipoint videoconferencing integrating H.323 and IPv4, SIP and IPv6 with autonomous sender authentication

In this paper we present a multipoint media conference software with extended network capabilities. Its core components combine an advanced, highly efficient H.264/AVC video coding system. Session signaling follows the SIP standard and simultaneously supports IPv4 and IPv6. Built upon an underlying peer-to-peer communication scheme, it further supports advanced integration with legacy MCUs and thereby enables hybrid sessions that extend into the H.323 world. We demonstrate how our software can span fully functional conferences across these worlds by deploying a passive gateway peer. Finally, we address security issues arising in distributed conferencing systems. It is shown, how the use of cryptographically generated identifiers enables the application to authenticate data on a packet level, thereby preventing abuse and impersonation of the conference overlay network.

An optimized 11.264-based video conferencing software for mobile devices

Mobile phones and related gadgets in networks are on the spot to deliver sufficient performance for rich multimedia applications and communication. In this report we introduce a video conferencing software, which seamlessly integrates mobile with stationary users into fully distributed multi-party conversations. Innovations related to this work are twofold. At first we report on a highly optimized realisation of a 11.264 codec and our implementation experiences of the video conference software on a consumer mobile. Within the tight bounds of real-time requirements on mobiles, the coding software out performs compatible 11.264 realizations. At second we present an integrated peer-to-peer group communication solution, which scales well for medium-size conferences and accounts for the heterogeneous nature of mobile and stationary participants.

Distributed SIP conference management with autonomously authenticated sources and its application to an H.264 videoconferencing software for mobiles

The design of conferencing systems for achieving efficient and flexible communication in a fully distributed, infrastructure-independent fashion is a promising direction, both in terms of research and practical development. In the particular case of video communication, the seamless adaptation to heterogeneous mobile devices poses an additional strong challenge to those seeking for interoperable and easy-to-deploy solutions. In this paper, we make several contributions towards a generic peer-to-peer (P2P) videoconferencing solution that extends into the mobile realm. We describe the essential building blocks for conference management and media distribution that are necessary for a distributed conferencing approach. Establishing a distributed SIP conference focus, participants share the conference according to their individually given capabilities and resources in terms of bandwidth and processing power rather than in a centralized and fixed way. Overall concepts and SIP-primitives for such an autonomous organization are presented. Security issues that derive from this decentralized identity management are resolved by so-called Overlay AuthoCast, a novel use of cryptographically generated identifiers. Furthermore, this work is dedicated to the development of a software-based H.264 video codec implementation and the specific aspects resulting from tuning such a highly resource-intensive software codec to the given target platform of a standard consumer smartphone.

Adaptive Temporal Scalability of H.264-Compliant Video Conferencing in Heterogeneous Mobile Environments

In this paper, we present a multipoint video conferencing system that adapts to heterogeneous members including mobiles. The system is built upon a low complexity scalable extension of our H.264 codec DAVC, and a congestion-aware dynamic adaptation layer. Our temporally scaled video codec DSVC has the same RD performance as the non-scaled version with comparable configuration. We achieve this by QP cascading, i.e., assigning gradually refining quantization parameters to the declining temporal layers. We present and analyse a mobile-compliant version of DSVC at reduced complexity that still admits comparable performance. Finally, we report on early work of dynamic layer tuning. Derived of delay variation measures, senders exploit scalable video layering to adapt the video transmission to varying network conditions. Initial results indicate that video performance remains close to optimal.

A virtual and distributed control layer with proximity awareness for group conferencing in P2PSIP

There is an increasing demand to access voice or video group conferences without the burden of a dedicated infrastructure, but at any place and in an ad hoc fashion. Corresponding solutions require a lightweight, fully distributed cooperation among parties that share and manage the conference in an efficient, self-adaptive way. The technology framework of P2PSIP can be seen as a promising starting point to meet these objectives. In this paper, we make several contributions towards such a distributed, virtualized control layer based on P2PSIP that seamlessly scales and adapts to the user needs. We propose a P2P-signaling protocol scheme for a distributed conference control with SIP, that splits the semantic of Identifier and Locator of a SIP conference URI in a standard-compliant manner. This protocol scheme serves as further basis for a virtualization in RELOAD. We further design and evaluate a self-organizing communication layer that provides load sharing and churn resilience with proximity-awareness. Finally, we address key aspects of security and trust, as well as compatibility for conference unaware clients.

Overlay AuthoCast: Distributed Sender Authentication in Overlay Multicast

Multicast services raise significant operational and security challenges not only when deployed on the Internet layer, but also in overlay networks. Large P2P groups as emerging from IPTV applications may be abused by unwanted traffic or denial of service attacks through amplified flooding. In this paper, we introduce a distributed, autonomously verifiable scheme for multicast sender authentication, which does not depend on pre-established trust relationships. Based on cryptographic identifiers and passport packets, any overlay peer is enabled to verify the origin of data prior to forwarding and to repel its misuse. Dynamic ingress filtering and individually established gradual trust allow for a lightweight protection of the distribution system in structured overlays.

Let's Meet at the Mobile - Learning Dialogs with a Video Conferencing Software for Mobile Devices

Mobile phones and related gadgets in networks are omnipresent at our students, advertising itself as the platform for mobile, pervasive learning. Currently, these devices rapidly open and enhance, being soon able to serve as a major platform for rich, open multimedia applications and communication. In this report we introduce a video conferencing software, which seamlessly integrates mobile with stationary users into fully distributed multi-party conversations. Following the paradigm of flexible, user-initiated group communication, we present an integrated solution, which scales well for medium-size conferences and accounts for the heterogeneous nature of mobile and stationary participants. This approach allows for a spontaneous, location independent establishment of video dialogs, which is of particular importance in interactive learning scenarios. The work is based on a highly optimized realization of a H.264 codec.