Efficient CABAC Bit Estimation for H.265/HEVC Rate-Distortion Optimization

摘要

The entropy coding of context-adaptive binary arithmetic coding (CABAC) has been utilized in the H.265/ HEVC for higher coding efficiency. But the related complexity also causes a bottleneck for its low-delay applications, owing to the employment of inter-symbol dependency in CABAC. In this paper, a fast bit-rate estimation method is proposed to skip the actual entropy coding of CABAC in mode decision to meet the requirement of low-delay implementations. The presented scheme firstly parses the characteristics of syntax elements and then guided by the principle of CABAC, an efficient scheme is derived following. It is very beneficial for reducing the computational complexity and saving the encoding time in H.265/HEVC mode decision. Experimental results demonstrate that the proposed fast algorithm can reduce the CABAC encoding time by 68% in average with negligible degradation in the rate-distortion performance.