Complexity-based intra frame rate control by jointing inter-frame correlation for high efficiency video coding

Rate control is of great significance for the High Efficiency Video Coding (HEVC). Due to the high efficiency and low complexity, the R-lambda model has been applied to the HEVC as the default rate control algorithm. However, the video content complexity, which can help improve the code efficiency and rate control performance, is not fully considered in the R-lambda model. To address this problem, an intra-frame rate control algorithm, which aims to provide improved and smooth video quality, is developed in this paper by jointly taking into consideration the frame-level content complexity between the encoded intra frames and the encoded inter frame, as well as the CTU-level complexity among different CTUs in texture-different regions for intra-frame. Firstly, in order to improve the rate control efficiency, this paper introduces a new prediction measure of content complexity for CTUs of intra-frame by jointly considering the inter-frame correlations between encoding intra frame and previous encoded inter frames as well as correlations between encoding intra frame and previous encoded intra frame. Secondly, a frame-level complexity-based bit-allocation-balancing method, by jointly considering the inter-frame correlation between intra frame and previous encoded inter frame, is brought up so that the smoothness of the visual quality can be improved between adjacent inter- and intra-frames. Thirdly, a new region-division and complexity-based CTU-level bit allocation method is developed to improve the objective quality and to reduce PSNR fluctuation among CTUs in intra-frame. In the end, related model parameters are updated during the encoding process to increase rate control accuracy. As a result, as can be seen from the extensive experimental results that compared with the state-of-the-art schemes, the video quality can be significantly improved. More specifically, up to 10.5% and on average 5.2% BD-Rate reduction was achieved compared to HM16.0 and up to 2.7% and an average of 2.0% BD-Rate reduction was achieved compared to state-of-the-art algorithm. Besides, a superior performance in enhancing the smoothness of quality can be achieved, which outperforms the state-of-the-art algorithms in term of flicker measurement, frame and CTU-wise PSNR, as well as buffer fullness. (C) 2016 Elsevier Inc. All rights reserved.