2 research outputs found
A Generic Algorithm for Mid-call Audio Codec Switching
We present and evaluate an algorithm that performs
in-call selection of the most appropriate audio codec given
prevailing conditions on the network path between the endpoints
of a voice call. We have studied the behaviour of different
codecs under varying network conditions, in doing so deriving
the impairment factors for non-ITU-T codecs so that the E-model
can be used to assess voice call quality for them. Moreover, we
have studied the drawbacks of codec switching from the end
user perception point of view; our switching algorithm seeks to
minimise this impact. We have tested our algorithm on different
packages that contain a selection of the most commonly used
codecs: G.711, SILK, ILBC, GSM and SPEEX. Our results show
that in many typical network scenarios, our switching codecs
mid-call algorithm results in better Quality of Experience (QoE)
than would have been achieved had the initial codec been used
throughout the call
Empirical studies of Quality of Experience (QoE) : A Systematic Literature Survey
Quality of Experience (QoE) is a relatively new phenomenon. The main focus of this thesis has been to conduct a systematic literature survey of research done in the field of QoE over a ten year period. The method, developed by A. Fink, has been used to survey empirical studies. A framework of QoE has been developed, which created the possibility of grouping together and analysing all the studies in a common framework.
In total, 44 studies were analysed. 66 per cent of them were studies with human participants and 34 per cent of them were studies without human participants. The majority of the selected empirical studies have analysed the sub-aspect ‘satisfaction’. Among other vital sub-aspects, which were of interest to researches, were ‘usefulness’, ‘ease of use’, ‘communication’, ‘loss/packet loss’, ‘delay’, ‘bandwidth’, and ‘jitter’. The results of this survey show that different sub-aspects depend on different services. It is not enough that one sub-aspect functions very well, because most of sub-aspects are closely related to each other. Therefore, it is very important that sub-aspects, which are dependent on each other, are functioning as one group to achieve higher QoE on user experience.
This thesis may contribute to deeper understanding of the phenomenon QoE. Knowledge of QoE can bring in new ideas and new possibilities for developing a new system or products for achieving satisfaction of user experience