Delivering 360-degree Video With Viewport-Adaptive Truncation

Delivering Virtual Reality (VR) content wirelessly involves projecting a 360-video into a 2D format and then encoding it to satisfy the wireless bitrate requirements. However, the popular equirectangular and cubemap projections offer little flexibility to adapt to changing bitrates and headset motion. In this work, we show that the truncated square pyramid projection offers high flexibility for network and headset motion adaptation. We adapt by tuning a truncation parameter that controls the video quality for different spatial regions in the 360-video. Depending on the video, our scheme improves average video quality by up to 1.1dB in PSNR and up to 4.6 in VMAF score compared to a non-adaptive baseline.