Bit-rate reduction using Superpixel for 360-degree videos - VR application

Abstract

Superpixels are applied on the side views of the 2D projected video. Then the video is partitioned into Coding Tree Units (CTUs). The CTUs and the superpixels positions will be compared within the frame of video. During comparison, the following cases will be considered: Case-1: If two or more CTUs are covered by the same superpixel, then the CTUs will be merged into one large coding tree unit. This merged CTU will be called as Intra CTU. Case-2: If one CTU is covered by two or more superpixels, then it will be referred to as Boundary CTU. After finding the Intra CTUs and Boundary CTUs, a Rate control algorithm was developed. The developed algorithm will allocate different QP values according to the cases 1 and 2. The Intra CTU will be coded with higher value of Quantization Parameter (QP) and Boundary CTU will be coded with lower value of QP. To apply this method, the rate control algorithm will modify the standard approach of applying same QP value on the entire video. Instead, in this algorithm, the code was written in such a way that it will recognize the Intra CTUs and Boundary CTUs and accordingly assign the QP values. Here proposed algorithm will not encode the entire video using the same QP, instead assign different QPs as discussed above to save bit-rate without loss in visual quality. Different quality metrics such as PSNR, SSIM and Bit-rate reduction are calculated and conclusions are drawn based on this.