A Novel Rate Control Scheme for Video Coding in HEVC-SCC

Abstract

The particular characteristics of contents generated by computers and the frequent scene change in screen content videos make the exiting R- $\lambda $ model in the rate control be not suitable to encode screen content videos. A novel rate control scheme designed for screen content videos coding (SCC) is proposed in this paper. Text blocks, screen image blocks and nature image blocks in screen content videos can result in different bitrate-distortion (R-D) relationships. A content-based rate control method is put forward at Coding Tree Unit (CTU) level for this reason. Three independent parameter update modes are adopted for three different types of CTUs according to their corresponding R-D relationship. Furthermore, frequent scene change in screen content videos needs a novel bit allocation scheme for precise rate control. In view of this, the frames in the screen content videos are classified into scene changed frames and scene unchanged frames. Different bit allocation methods are adopted for different types of frames on the basis of inter frame and intra frame complexity. Besides, a region level bit allocation algorithm considering the inter frame continuity and the numbers of different types of CTUs is added between frame level and CTU level bit allocation schemes. Experimental results show that our proposed rate control algorithm respectively achieves 0.88 dB BDPSNR and 1.54 dB BDPSNR increase under the Low Delay coding structure on average, compared with the default rate control algorithm with hierarchical and non-hierarchical bit allocation in the HEVC-SCC.