Multimedia Quality Integration Function for Videophone Services

We present a multimedia quality integration function that can estimate the overall quality of a videophone service considering multimodality and interactivity. That is, it takes into account individual audiovisual qualities and their delays. Videophone services are rich multimedia services that are expected to become popular on the next-generation network (NGN). To provide ones with sufficient quality, we must properly evaluate, design, and manage users' perceptual quality of service, i.e., quality of experience (QoE). Subjective quality assessment tests were conducted using a PC-based point-to-point interactive videophone application to clarify how overall multimedia quality characteristics depend on the individual audiovisual qualities, absolute audiovisual delay, and media synchronization. From the test results, we formulated a multimedia quality integration function that can accurately evaluate overall multimedia quality. In addition, verification test results showed that this function achieved good performance in terms of correlation coefficient and evaluation error between subjective and estimated qualities. Our model will be a useful QoE planning tool capable of providing feedback on individual qualities as well as the overall multimedia quality of videophone services.