Quality of Experience of adaptive video streaming: Investigation in service parameters and subjective quality assessment methodology

• The semi-continuous method used in this study can be an appropriate approach for evaluation of the adaptation events which can last up to some minutes.
• On the comparison between the testing methodologies (ACR and the semi-continuous method) and influence of audio presence on subjective evaluation of test videos no statistically significant effect was found.
• The QoE of constant low quality was voted statistically significantly lower compared to the up-switching.
• No main effect from ANOVA was observed for any of the adaptation related study factors, i.e. in contrary to many of previous studies, using short chunk or abrupt quality switching do not necessarily degrade the QoE.
• The video content characteristics had an influence on the absolute MOS results.

The usage of HTTP adaptive streaming (HAS) has become widely spread in multimedia services. Because it allows the service providers to improve the network resource utilization and user׳s Quality of Experience (QoE). Using this technology, the video playback interruption is reduced since the network and server status in addition to capability of user device, all are taken into account by HAS client to adapt the quality to the current condition. Adaptation can be done using different strategies. In order to provide optimal QoE, the perceptual impact of adaptation strategies from point of view of the user should be studied. However, the time-varying video quality due to the adaptation which usually takes place in a long interval introduces a new type of impairment making the subjective evaluation of adaptive streaming system challenging. The contribution of this paper is two-fold: first, it investigates the testing methodology to evaluate HAS QoE by comparing the subjective experimental outcomes obtained from ACR standardized method and a semi-continuous method developed to evaluate the long sequences. In addition, influence of using audiovisual stimuli to evaluate the video-related impairment is inquired. Second, impact of some of the adaptation technical factors including the quality switching amplitude and chunk size in combination with high range of commercial content type is investigated. The results of this study provide a good insight toward achieving appropriate testing method to evaluate HAS QoE, in addition to designing switching strategies with optimal visual quality.