Subjective and objective quality assessment of omnidirectional video

Omnidirectional video, also known as 360° video, is becoming quite popularsince it provides a more immersive and natural representation of the real world. However, to fulfill the expectation of an high quality-of-experience (QoE), the video content delivered to the end users must also have high quality. To automatically evaluate the video quality, objective quality assessment metrics are then required. This paper starts by presenting the results of a subjective assessment campaign that was conducted to evaluate the impact, on quality, of HEVC compression and/or spatial/temporal subsampling, when the videos are displayed in a head mounted device (HDM). The subjective assessment results are then used as ground-truth to evaluate conventional quality assessment metrics developed for 2D video, as well as some of the recently proposed metrics for omnidirectional video, namely, spherical peak-signal to noise ratio (S-PSNR), weighted to spherically uniform PSNR (WS-PSNR), and viewport PSNR (VP-PSNR); in the context of this study, the adaptation of two SSIM based metrics, to omnidirectional contents, are also proposed and evaluated.