A QoE study of different stream and layout configurations in video conferencing under limited network conditions

One particular problem of QoE research in video conferencing is, that most research in the past concentrated on one-to-one video conferencing or simply video consumption. However, video conferencing with two people (one-to-one) and within a group (multi-party) is different. Particularly, limitations of one participant might have an effect on the QoE of the whole group. This possible effect however is not well studied. Therefore, this paper aims to better understand the impact of individual limitations towards the groups QoE. To do so, we show a study about different video stream configurations and layouts for multi-party conferencing in respect to individual network limitations. For this, we conduct a user study with 20 participants in 5 groups, in a semi-controlled setup. Such a setup, combines supervising participants locally while still using our software infrastructure deployed in the internet. Furthermore, we use an asymmetric experiment design, by putting every participant under a different condition, as this proposes a more realistic scenario. Within our study, we look at three different factors: layout, video quality and network limitations. To foster conversation between participants, the group engaged in a discussion based team building exercise about survival in the wilderness. Our findings show that packet loss and the resulting distortions have a greater impact on the QoE as reducing the video quality by its resolution. Furthermore, our findings indicate that participants are more satisfied in a visually equal layout (showing participants in a similar size) and a more balanced stream configuration.

I. Introduction

The wide popularity of video conferencing systems does not necessarily translate on the provision of fully satisfying user experiences. Technical difficulties, delays, and blurred videos are still commonplace in commercial services such as Skype and Google+ Hangouts. Even though some optimization mechanisms do exist [1] [2] [3], the use of conversation dynamics of participants in such systems is rather limited. This is also large due to limited research work in the aspect of group conversation analysis in video conferencing. One particular problem in group video conferencing is that even if only one computer is on a low internet connection, or suffering of problems, the experience for all participants will suffer. Thus, the study presented in this paper explores the relationship between QoE and three different factors: layout, video quality (resolution) and network limitations (packet loss). In detail our study analyses four different layout/stream configurations, with different bandwidth profiles and thus different network problems (packet loss). This study included 20 participants in 5 groups (4 people in each group) that were invited to our institute. We structured our study in a semi-controlled environment which allowed us to control the environment of participants (similar PC, room, lighting) while utilizing our server infrastructure in the internet. This is a practical approach that still results into realistic network conditions. Furthermore, the four layout/stream configurations where conducted in an asymmetric experiment design, giving every participant a different condition (in random order). This is also a practical and realistic approach and currently under the investigation of the ITU [4].