Pavel Troubil

Media Streams Planning with Transcoding

High-quality video, both uncompressed and compressed with relatively low compression ratio, is used in interactive environments, where minimum end-to-end latency is required. The media streams planning solves multi-point data routing for such applications even when bit rate of streams is comparable to capacity of network links. Recent advances in acceleration of high-throughput low-latency video processing enable on-the-fly video transcoding even for 4K and 8K video streams, thus allowing individual adaptation of data stream for each recipient without affecting the others. Stimulated by these advances, we present a novel media streams planning with transcoding on network nodes, and a mixed integer programming approach to solve the problem optimally. Our approach also enhances traditional end-to-end network model of the whole system with known topology of certain network regions. Our solution was implemented in the Co Universe, which is middleware for orchestration of collaborative environments. Measurements show that performance of the new solver is sufficient for interactive solving of most practical use-cases, thus enabling self-organization of high-performance collaborative environments.

Integer Programming for Media Streams Planning Problem

Continually increasing demands for high-quality videoconferencing have brought a problem of fully automated environment setup. A media streams planning problem forms an important part of this issue. As the multimedia streams are extremely bandwidth-demanding, their transmission has to be planned with respect to available capacities of network links and the plan also needs to be optimal in terms of data transfer latencies. This paper presents an integer programming solution of the problem and its implementation. The implementation achieved very promising results in performance-evaluating measurements. Compared to previous constraint-based solver, it is capable of finding optimal solution significantly faster, allowing for real-time planning of larger problem instances.

GColl: A Flexible Videoconferencing Environment for Group-to-Group Interaction

In this paper, we present GColl, a group-to-group videoconferencing environment concept, which aims to provide a natural communication channel even for ad-hoc groups or other teams that require frequent changes in the number of participants or videoconferencing locations. GColl supports mutual gaze as well as partial gaze awareness for all participants while still retaining very modest technical requirements: a camera and an echo-canceling microphone at each site; and a notebook with two USB cameras for each user. A working prototype is available for download.

GColl: enhancing trust in flexible group-to-group videoconferencing

In this paper we describe a quantitative study of a group-to-group videoconferencing environment called GColl that provides a compromise between the need for preserving non-verbal cues and the requirements of low-cost and flexibility. We have compared the task process and outcome of participants interacting over an environment analogous to common commodity solutions, those using face-to-face communication, and groups communicating over GColl. Our results demonstrate that it is possible to design a group-to-group collaboration environment with modest technical requirements and low overall cost that still shows measurable advantages over the common environment in its ability to support trust in social dilemma games.

Videoconferencing design for remote groups

Videoconferencing has emerged as a popular method of remote communication. The design of a videoconferencing environment strongly influences the communication efficiency and user satisfaction. Various studies on perceived effects of videoconferencing environments and their parameters have been done, however, they primarily focused on dyadic conversation. This paper describes an exploratory study on the effects on remote groups communication. Beginning with the standard environment, a videoconferencing design has been developed iteratively according to information obtained from the experimental group. Two new videoconferencing environment designs are introduced to suit the group conversation needs better and bring the group videoconference closer to face-to-face communication.

Media Streams Planning with Uncertain Link Capacities

Interactive collaborative environments built upon high quality video applications require minimum capture-to-display latency to maintain feeling of natural communication. In practice, end users often encounter interruptions due to network congestion, which they could not avoid without knowledge of physical network infrastructure. We solve the problem of application level multipoint routing without assuming accurate knowledge of network link capacities, but rather relying on their estimates by network inference and bandwidth measurement tools. Our approach can handle uncertainties caused by both unreliable bandwidth measurements and unexpected capacity sharing. Support for on-the-fly transcoding of data streams on multicast agents allows per-recipient adaptation of video quality and bandwidth. We have implemented an ant colony optimization algorithm in the Co Universe middleware for orchestration of collaborative environments. Experiments show very good quality of results on most practical use cases and ability to solve significantly larger instances than optimal approaches based on mixed integer programming.

Exploring trust in group-to-group video-conferencing

Previous work has shown that supporting trust via computer-mediated communication can be a challenge, especially among strangers. In this paper, we report on an experiment comparing two group-to-group video-conferencing environments and face-to-face communication in their ability to support trust and mutual cooperation in a social dilemma task. There are pronounced differences in participant behaviour between the two video-conferencing designs, indicating higher mutual trust in one of the video-conferencing conditions. The decisive factor seems to be a discrepancy in the type of group identity that develops during the game. Moreover, our results suggest that a combination of personal displays and a unique video-stream of each participant present in the better video-conferencing condition contributed to this result.

CoUnSiL: Collaborative Universe for Remote Interpreting of Sign Language in Higher Education

In this paper, we report on CoUnSiL (Collaborative Universe for Sign Language), our ongoing project on the videoconferencing environment for remote interpreting of sign language. Our work is motivated by the lack of qualified interpreters capable of interpreting highly specialized courses at universities. We present the tool that ensures low latency and sustainable framerate of multiple video and audio streams. We describe both the user interface of the CoUnSiL application followed by the background technologies. Next, we present the three evaluations with users.

CoUnSiL: A video conferencing environment for interpretation of sign language in higher education

Collaborative Universe for Sign Language (CoUnSiL) is a video conferencing environment for remote interpreting of sign language designed for use in higher education courses. The work is motivated by the lack of qualified interpreters capable of interpreting highly specialized courses at universities. Our ambition is to have a system that enables interpreting remotely to the same extent as on-site. Such as system allows us to utilize the free capacity of external interpreters who are not available physically in the location of a lecture which requires interpreting. The CoUnSiL environment ensures low latency and sustainable frame rate of multiple video and audio streams for up to 10 participants. In this paper, we describe the design requirements, present the backend technologies as well as the client-server architecture of the CoUnSiL environment. Further, we report on user evaluation sessions and their outcomes that influenced its final version.

Exploring Collaboration in Group-to-Group Videoconferencing

Prior work on videoconferencing shows that various design changes can have profound impacts on group dynamics. In order to further explore the available design space, we report on a qualitative study that compares behaviour of groups in two group-to-group videoconferencing environments and face-to-face communication during a complex social dilemma game. There are pronounced differences in participant behaviour between the two videoconferencing designs, indicating higher cooperative behaviour in one of the videoconferencing conditions. Based on qualitative analysis of the gameplay, we hypothesise that the decisive factor is a discrepancy in the type of group identity that develops during the game. Our results suggest that the differences in behaviour are due to differences in design of the two videoconferencing environments. In particular, the incorporation of personal displays and individualised videostreams likely contributed to these outcomes.