A Novel Region-Dependent Packing Method for Stereoscopic 360° Videos Using Horizontal Downsampling of Equirectangular Projection

Utilizing frame-compatible (FC) formats is a common strategy for leveraging the existing single-view video transmission infrastructure to stream stereoscopic videos. However, using this method often comes with challenges, as stereoscopic video requires higher transmission bandwidth and larger memory buffers on the decoder compared to single-view videos. When it comes to stereoscopic 360° videos, these requirements become more challenging since they ask for ultra-high-resolution formats with high frame rates (e.g., 6K, 8K, or 12K at 100 frames per second) to provide an acceptable quality of experience (QoE) to the users (4K on a 120° viewport). To address these challenges, sub-sampled versions of the left and right views are usually used to form the spatial FC format, leading to a loss of visual quality. In this paper, we first analyze the amount of distortion due to hor-izontal and vertical downsampling in equirectangular projection (ERP). Then, we propose a novel region-dependent downsampling packing (RDDP) method using horizontal downsampling which exploits the uneven sampling characteristic of the ERP for stereoscopic 360° videos. Experimental results, using the VVC (VVenC) encoder, show that compared with the standard side-by-side (SbS) format, the proposed RDDP method for both views provides an average of around 8.7% and 7% of Bjentegaard-Delta bitrate (BD-BR) reduction for Random Access (RA) and Low Delay B (LDB) configurations, respectively with almost the same encoding time of SbS on average.