Adaptive Quantization-Parameter Clip Scheme for Smooth Quality in H.264/AVC

In this paper, we investigate the issues over the smooth quality and the smooth bit rate during rate control (RC) in H.264/AVC. An adaptive quantization-parameter (Qp) clip scheme is proposed to optimize the quality smoothness while keeping the bit-rate fluctuation at an acceptable level. First, the frame complexity variation is studied by defining a complexity ratio between two nearby frames. Second, the range of the generated bits is analyzed to prevent the encoder buffer from overflow and underflow. Third, based on the safe range of the generated bits, an optimal Qp clip range is developed to reduce the quality fluctuation. Experimental results demonstrate that the proposed Qp clip scheme can achieve excellent performance in quality smoothness and buffer regulation.