On the Compression Performance of HEVC, VP9 and AV1 Encoders for Virtual Reality Videos

Thanks to advances in display technologies and affordable end user devices, interest in Virtual Reality (VR) and related multimedia content, namely 180° and 360° images and videos, has been rapidly increasing in recent years. For effective delivery of a video in such format, compression algorithms with high efficiency are vital. In this paper, the outputs of a subjective-based compression performance study of recent (HEVC and VP9) and emerging (AV1) video coding formats for 180°/360° videos are presented. Viewers' Quality of Experience (QoE) is assessed by subjective tests utilizing Absolute Category Rating with Hidden Reference (ACR-HR) protocol. In addition, these tests, wherein two different Head Mounted Devices (HMDs) from Oculus were used, are extended with a custom questionnaire that helps to better understand observers' experience and feelings with VR. Results revealed that not only the quality levels (bit rates) of the compressed 180°/360° videos have influence on the viewers' perceived QoE.