A rate control scheme for H.264 video transmission

In some video applications, a variable bit rate (VBR) video bitstream will be transmitted over a constant bit rate (CBR) transmission channel, in which a channel buffer is employed. In this study, a rate control scheme for H.264 video transmission is proposed. The target number of bits for each video frame is first obtained. Three rate-quantization (R-Q) models are proposed to approximate the relationship between the number of coding bits for a video frame, B, and the quantization step size, Q, in the frame layer. The best model is selected to determine the candidate QP for the current video frame. After the coding complexity of each macroblock (MB) is estimated by using the candidate QP, the Lagrange multiplier is used to optimally select the N quantization step sizes {Q/sub mb,1/,Q/sub mb,2/,...,Q/sub mb,N/} for the N MB (macroblocks) in a video frame to minimize the distortion, subject to the given bit budget constraint. Based on the simulation results obtained in this study, the proposed approach can meet the target bit rate more accurately, keep a larger average frame rate, and higher PSNR values than the two quadratic approaches for comparison.