{'fraction_non_alphanumeric': 0.031578947368421054, 'fraction_numerical': 0.01818181818181818, 'mean_word_length': 5.116959064327485, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Spherical domain rate-distortion optimization for 360-degree video coding

Emerging virtual reality (VR) applications bring much challenge to video coding for 360-degree videos. To compress this kind of video, each picture should be projected to a 2D plane (e.g. equirctangular projection map) first, adapting to the input of existing video coding systems. At the display side, an inverse projection is performed before viewport rendering. However, such a project introduces much different levels of distortions depending on the location, which makes the rate-distortion optimization process in video coding much inefficient. In this paper, we consider the distortion in spherical domain and analyse its influence to the rate-distortion optimization process. Then we derive the optimal rate-distortion relationship in spherical domain and present its optimal solution based on HEVC/H.265. Experimental results show that the proposed method can bring up to 11.5% bit-saving compared with the current HEVC/H.265 anchor for 360-degree video coding.