360PI: A Practical Performance Index for 360-Degree Video Streaming Systems

The proliferation of 360-degree video streaming to mobile devices and VR headsets has driven significant research, yet a standardized framework for evaluating quality-cost trade-offs in streaming approaches remains lacking. This paper introduces 360PI, a novel metric that quantifies performance by measuring the Euclidean distance between a scheme's operation point (quality vs. cost) and an adaptive baseline curve. Unlike prior methods focusing solely on quality or cost, 360PI enables unified, context-aware comparisons by aligning with application priorities (e.g., quality or cost sensitivity). We extend the open-source simulator E3PO to compute 360PI, validating its effectiveness across state-of-the-art approaches. Experiments demonstrate that 360PI accurately benchmarks trade-offs of diverse approaches. By bridging the gap in systematic evaluation, this work provides a data-driven foundation for optimizing 360-degree video streaming systems, guiding advancements in immersive media delivery.