关键词: H.264, 码率控制, 量化参数, 平均绝对值差

Abstract: Due to limited bandwidth of communication channel，it is necessary to control the bit rate of video coding output.This paper proposes the estimation of initial value of QP and macroblock layer rate control.In the computation of initial value of QP，this paper proposes bpp，entropy and gradient as an estimate of the complexity of the image.It calculates the initial value of QP through this way.Meanwhile，this paper improves the prediction of MAD by using motion vector and the MAD gradient.Thus，it can achieve the control of the bit rate more effectively.The simulation results show that compared with the algorithms of H.264 reference software JM11.0，the proposed algorithm enhances the PSNR and is closer to the target bit.

Key words: H.264, rate control, Quantization Parameter（QP）, Mean Absolute Difference（MAD）