LAUSR

The expectations of modern mobile users are increasingly moving towards being able to access demanding services regardless of context or system influence factors, such as network conditions, service topology, and device processing capabilities. Multiparty audiovisual telemeetings are an example of a real-time, delay sensitive, and heavy load service, demanding to run on smartphones that are limited in display size, processing power, and battery capacity. In this paper, we first provide an overview of multiparty audiovisual calls established via mobile devices and key aspects influencing Quality of Experience (QoE). We then report on the results of five user studies conducted over the course of the past 4 years, focused on investigating the impact of video quality in terms of different video encoding parameter configurations (namely bitrate, frame rate, and resolution) on subjective QoE scores for WebRTC-based video calls. We identify lower and upper bounds on video configuration parameters when used in the context of three-party calls. Results have shown that in certain cases it is better to provide constant lower objective video quality than to switch between higher and lower qualities, since participants start to perceive impairments. Finally, we investigate the relationship between objectively measured video quality impairments (blurriness and blockiness) and subjective user scores. Obtained results indicate that the Birnbaum-Saunders distribution for blockiness and the Burr and Gamma distributions for blurriness provide good fits for quality ratings. Gathered results aim to provide input for deriving QoE-aware service adaptation strategies, enabling increased resource allocation efficiency while maintaining acceptable end-user QoE.