Influence of 4^th-Order Ambisonics Audio on the Perceived Quality and Exploration Behavior of 360° Videos

Recent technological advances have increased the popularity of immersive video consumption, such as head-mounted devices for 360° video displays. Higher video resolutions and highly realistic scene representations are typically prioritized to enhance immersion in 360° videos. One often not-so-well-studied and analyzed aspect related to the sense of immersion in 360° videos is the video stream paired with spatial audio, which is addressed in this paper. Two subjective studies are designed and conducted to investigate the interplay between audio and encoding parameters on video quality perception and users’ exploration behavior. The studies follow a within-subjects and between-subjects design to assess the impact of 4<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup>-order Ambisonics audio (4OA audio) on the perceived 360° video quality, exploration behavior, and user’s sense of comfort measured as cybersickness. In the experiments conducted, audio representation (4OA audio and no audio) and video compression parameters (H.264 and H.265 codecs with different settings) were varied. The audio conditions were found not to influence the video quality rating and the cybersickness in the test carried out. This finding demonstrates that participants were able to focus on visual quality during the assessment task without being influenced by the presence of spatial audio. At the same time, increased scene exploration with 4OA audio suggests that spatial audio did affect how participants interacted with the content, highlighting its role in shaping engagement even when not directly reflected in quality ratings. Additionally, less exploration was observed during repeated viewings, indicating that participants became familiar with the content and adopted a more focused viewing strategy to judge visual quality.