AKI360: Enabling Highly Interactive 360-degree Video Streaming by Adaptive Keyframe Interval

360-degree video is a panoramic video technology designed to offer audience an immersive visual experience. In Motion Constrained Tile Set (MCTS)-based streaming schemes, the server only updates Field-Of-View (FOV) coordinates when codec generating keyframes, thus the keyframe interval significantly impacts FOV updates and interactivity. However, reducing the keyframe interval poses greater challenges for network transmission and encoding/decoding overhead. To address these issues, we design and implement AKI360, a 360-degree video streaming system with an Adaptive Keyframe Interval (AKI) mechanism along with Quantization Parameter (QP) adjustments. Extensive experiments show that AKI360 reduces the motion stall duration by 31% to 74% and FOV update interval by 78% to 86% comparing with the real-time approaches, and eliminates the blank area in the best-case comparing with the state-of-the-art pre-encoded approach. Meanwhile, AKI360 improves the video quality by up to 0.78 decrease in NIQE while maintaining comparable frame rate.