Emerging challenges in subjective quality assessment of volumetric videos in eXtended Reality

Visual quality assessment of volumetric videos has become an important matter for emerging use cases and applications in eXtended Reality (XR). The results of such experiments can pave the way for upgrades in compression and rendering methods that will improve the Quality of Experience of end users. However, only a few subjective experiments were run to assess the perceived quality of such dynamic content, and no standard methodologies and recommendations have been defined for now. In this paper, we analyze and compare the available results from subjective experiments in XR for the quality assessment of volumetric videos represented as Dynamic Point Clouds. By doing so, we determine the requirements in terms of number of observers for various test and rating methodologies. Our conclusion is a step forward to the definition of common test conditions for dynamic volumetric content in 6DoF subjective quality assessment.