QUALITY EVALUATION OF LONG DURATION AUDIOVISUAL CONTENT

Subjective quality assessment of multi-modal services depends on a number of external factors that affect the final judgment, e.g. user expectations, user fatigue, room environment or methodology used in the evaluation process. In order to obtain as accurate as possible measurement of the perceived quality, an experimenter should carefully consider all factors contributing to the overall experience. Particulary important is to choose the right measurement method for the purpose of a specific task. In spite of the fact that a number of standardized test procedures for the quality assessment exist it is not always possible to find the one which suits a certain research purpose. In such case, the development of new assessment techniques is usually necessary, which then needs to be followed by appropriate testing and validation procedures. The lack of an appropriate methodology for instantaneous measurement of user’s audio-visual quality expectations/preferences over extended periods of time, as well as the scarce attention devoted to the topic of temporal development of Quality of Experience, were the main driving factors for this work. This dissertation, composed of five papers, helps to understand the underlying attributes of perceived quality and user cognitive processes used in evaluation of long duration audiovisual content. The work described here is twofold: firstly, a novel methodology for continuous quality evaluation is proposed, and secondly, using the method, the effect of the time dimension on user’s behavioral reaction to the experienced quality is investigated. The momentary-based approach described in this work reflects instantaneous measures of users’ quality judgements. Such measures allow capturing time varying changes of system characteristics and help to contribute to the holistic vision of quality of experience. The results obtained from several experiments described in this work reveal the importance of content duration in the process of quality assessment and its impact on user’s quality requirements. The knowledge gained from those studies can be directly applied to the quality assurance models of multimedia content providers and may serve as a valuable source of information for objective quality metrics development