Revisiting Pre-analysis Information Based Rate Control in x265
This work addresses an incremental improvement in video compression efficiency for users of the x265 encoder, enhancing rate-distortion performance.
The paper tackles the problem of suboptimal rate control in x265 by proposing an improved cost-guided scheme that better utilizes pre-analysis information and integrates CU-tree with a lambda-domain model, resulting in a 10.3% BD-rate gain with only 0.22‰ bitrate error.
Due to the excellent compression and high real-time performance, x265 is widely used in practical applications. Combined with CU-tree based pre-analysis, x265 rate control can obtain high rate-distortion (R-D) performance. However, the pre-analysis information is not fully utilized, and the accuracy of rate control is not satisfactory in x265 because of an empirical linear model. In this paper, we propose an improved cost-guided rate control scheme for x265. Firstly, the pre-analysis information is further used to refine the bit allocation. Secondly, CU-tree is combined with the lambda-domain model for more accurate rate control and higher R-D performance. Experimental results show that compared with the original x265, our method can achieve 10.3\% BD-rate gain with only 0.22\textperthousand bitrate error.