Fernando Boronat

Multimedia group and inter-stream synchronization techniques: A comparative study

This paper presents the most comprehensive analysis and comparison of the most-known multimedia group and inter-stream synchronization approaches. Several types of multimedia synchronization are identified but only inter-stream and group synchronization algorithms are considered. This is the first survey including group synchronization techniques. A classification of the main synchronization techniques included in most of the analyzed algorithms complements the paper. Finally, a table is presented summarizing the main characteristics of each analyzed algorithm according to those techniques and other critical issues.

Inter-Destination Multimedia Synchronization: Schemes, Use Cases and Standardization

Traditionally, the media consumption model has been a passive and isolated activity. However, the advent of media streaming technologies, interactive social applications, and synchronous communications, as well as the convergence between these three developments, point to an evolution towards dynamic shared media experiences. In this new model, geographically distributed groups of consumers, independently of their location and the nature of their end-devices, can be immersed in a common virtual networked environment in which they can share multimedia services, interact and collaborate in real-time within the context of simultaneous media content consumption. In most of these multimedia services and applications, apart from the well-known intra and inter-stream synchronization techniques that are important inside the consumers’ playout devices, also the synchronization of the playout processes between several distributed receivers, known as multipoint, group or Inter-destination multimedia synchronization (IDMS), becomes essential. Due to the increasing popularity of social networking, this type of multimedia synchronization has gained in popularity in recent years. Although Social TV is perhaps the most prominent use case in which IDMS is useful, in this paper we present up to 19 use cases for IDMS, each one having its own synchronization requirements. Different approaches used in the (recent) past by researchers to achieve IDMS are described and compared. As further proof of the significance of IDMS nowadays, relevant organizations’ (such as ETSI TISPAN and IETF AVTCORE Group) efforts on IDMS standardization (in which authors have been and are participating actively), defining architectures and protocols, are summarized.

GBP-WAHSN: A Group-Based Protocol for Large Wireless Ad Hoc and Sensor Networks

Grouping nodes gives better performance to the whole network by diminishing the average network delay and avoiding unnecessary message forwarding and additional overhead. Many routing protocols for ad-hoc and sensor networks have been designed but none of them are based on groups. In this paper, we will start defining group-based topologies, and then we will show how some wireless ad hoc sensor networks (WAHSN) routing protocols perform when the nodes are arranged in groups. In our proposal connections between groups are established as a function of the proximity of the nodes and the neighbors available capacity (based on the nodes energy). We describe the architecture proposal, the messages that are needed for the proper operation and its mathematical description. We have also simulated how much time is needed to propagate information between groups. Finally, we will show a comparison with other architectures.

Improving networks using group-based topologies

Communication network topology design needs to address several conflicting requirements, such as minimizing the overall network diameter, minimizing the infrastructure cost, minimizing management cost, maximizing load distribution and so on. Centralized, decentralized, and partially centralized networks have their respective benefits as well as several drawbacks. It is known that grouping nodes gives better performance to the group and to the whole system, thereby avoiding unnecessary message forwarding and additional overheads. This paper proposes a survey of group-based topologies. It shows their main issues and in which real environments they could be used. The improvement of the networks by using these kinds of topologies will also be discussed. We have split group-based topologies into two classes, planar and layered group-based topologies, and we will discuss existing group-based systems in both types. Highlighting one of the main aims of the paper, their comparison, benefits and drawbacks are presented. Finally, authors will describe two group-based topologies designed by them, one for planar group-based topologies and another for layered group-based topologies, and they will be compared with different previous works. We consider this work as a starting point for researchers on new group-based topologies.

Enhanced adaptive RTCP-based Inter-Destination Multimedia Synchronization approach for distributed applications

Newer social multimedia applications, such as Social TV or networked multi-player games, enable independent groups (or clusters) of users to interact among themselves and share services within the context of simultaneous media content consumption. In such scenarios, concurrently synchronized playout points must be ensured so as not to degrade the user experience on such interaction. We refer to this process as Inter-Destination Multimedia Synchronization (IDMS). This paper presents the design, implementation and evaluation of an evolved version of an RTCP-based IDMS approach, including an Adaptive Media Playout (AMP) scheme that aims to dynamically and smoothly adjust the playout timing of each one of the geographically distributed consumers in a specific cluster if an allowable asynchrony threshold between their playout states is exceeded. For that purpose, we previously had also to develop a full implementation of RTP/RTCP protocols for NS-2, in which we included the IDMS approach as an optional functionality. Simulation results prove the feasibility of such IDMS and AMP proposals, by adopting several dynamic master reference selection policies, to maintain an overall synchronization status (within allowable limits) in each cluster of participants, while minimizing the occurrence of long-term playout discontinuities (such as skips/pauses) which are subjectively more annoying and less tolerable to users than small variations in the media playout rate.

On the Use of Adaptive Media Playout for Inter-Destination Synchronization

Inter-Destination Multimedia Synchronization (IDMS) is essential in most of the emerging social multimedia applications. In this paper we present a novel Adaptive Media Playout (AMP) scheme that aims to acquire an overall synchronization status between distributed receivers by means of smoothly adjusting their playout timing. Simulation results show that the proposed solution minimizes long-term playout discontinuities (skips and/or pauses) which are subjectively more annoying to users than small variations in the media playout rate.

Two Levels SPF-Based System to Interconnect Partially Decentralized P2P File Sharing Networks

Partially decentralized P2P (PDP2P) networks are a subset of P2P networks. Roles of nodes are different according to their functionality in the network. Nowadays, there are many PDP2P networks, with different characteristics. It is necessary to find a way to join those autonomous networks. We have not found any interconnection system, so in this article we present a new hierarchical system for interconnecting peers from different PDP2P networks. It will allow sharing data, content and resources between networks. It can be employed between sensor networks, P2P networks, and generally, overlay networks. Oldest superpeers or brokers with higher bandwidth in the PDP2P network will belong to higher layers. The topology will change as a function of the available processing capacity and the available number of connections with neighbor nodes. We also describe the interconnection system and its management. Simulations results for some topologies are shown

The need for inter-destination synchronization for emerging social interactive multimedia applications

Currently, the media consumption paradigm is changing from a single end user to a group shared experience. Now, social communication opportunities may be exploited (e.g., conferencing while watching television), facing lots of technological (e.g., synchronization, universal session handling, scalability) and perceptual (e.g., presence awareness, QoE) challenges. This article focuses on one of these major challenges ahead in new emerging social interactive multimedia applications, which is the synchronization of different media streams across multiple locations, known as inter-destination multimedia synchronization (IDMS). We describe the three kinds of temporal multimedia synchronization, and summarize some related work and examples of applications in which IDMS is needed. The article includes a discussion about an RTP/RTCP-based IDMS solution the authors have been working on, as well as the standardization status regarding this kind of synchronization.

Understanding Timelines Within MPEG Standards

Nowadays, media content can be delivered via diverse broadband and broadcast technologies. Although these different technologies have somehow become rivals, their coordinated usage and convergence, by leveraging of their strengths and complementary characteristics, can bring many benefits to both operators and customers. For example, broadcast TV content can be augmented by on-demand broadband media content to provide enriched and personalized services, such as multi-view TV, audio language selection, and inclusion of real-time web feeds. A piece of evidence is the recent Hybrid Broadcast Broadband TV (HbbTV) standard, which aims at harmonizing the delivery and consumption of (hybrid) broadcast and broadband TV content. A key challenge in these emerging scenarios is the synchronization between the involved media streams, which can be originated by the same or different sources, and delivered via the same or different technologies. To enable synchronized (hybrid) media delivery services, some mechanisms providing timelines at the source side are necessary to accurately time align the involved media streams at the receiver-side. This paper provides a comprehensive review of how clock references (timing) and timestamps (time) are conveyed and interpreted when using the most widespread delivery technologies, such as DVB, RTP/RTCP and MPEG standards (e.g., MPEG-2, MPEG-4, MPEG-DASH, and MMT). It is particularly focused on the format, resolution, frequency, and the position within the bitstream of the fields conveying timing information, as well as on the involved components and packetization aspects. Finally, it provides a survey of proofs of concepts making use of these synchronization related mechanisms. This complete and thorough source of information can be very useful for scholars and practitioners interested in media services with synchronization demands.

Design and Simulation of a Distributed Control Scheme for Inter-destination Media Synchronization

Inter-Destination Multimedia Synchronization(IDMS) is a key requirement to enable satisfying group shared media experiences. This paper presents the design and simulation of a Distributed Control Scheme (DCS) for IDMS. In this scheme, geographically dispersed receivers exchange(multicast) RTCP reports on their arrival and play out timing for RTP packets, and each one of them uses the collected reports from the other receivers belonging to the same logical group (or cluster) to adaptively adjust its local play out timing such that an overall synchronization status (within allowable limits) is maintained. Also, the strengths (interactivity, flexibility, scalability, and robustness) and weaknesses (traffic overhead, security) of a DCS for IDMS are discussed, in comparison with centralized approaches. Moreover, a simple technique to enhance the performance in terms of coherence when using the DCS for IDMS is proposed. Simulation results prove the effectiveness of the proposed control scheme and techniques to guarantee concurrently synchronized play outpoints for independent clusters of receivers.