Seamless use of video telephony in future mobile communication systems creates new challenges for high-quality provisioning. Terminal mobility and dynamically changing network properties will affect the quality of the Internet connection and consequently will impair the Quality of Experience (QoE) of mobile users. To ensure best connected video calls, cross-layer adaptation of the audiovisual transmission to the network circumstances will be required. To successfully adapt the transmission parameters, knowledge about the user perception during mobile video calls is required. This paper addresses this issue and presents a study of quality experience during selected periods of emulated video calls. Perception of dynamic phenomena, such as roaming between network technologies, switching the video and speech codecs, and changing the video bit rate during active calls are in scope of the investigation. The QoE of the analysed material is linked to the underlying transmission properties, which allows to select proper strategies of QoE adaptation during mobile video calls in future wireless networks.