In some video applications, the 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.26L video transmission is proposed. The target number of bits for each frame is first obtained. Two 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 better model is selected to determine the candidate QP for the current frame. After the coding complexity of each macroblock is estimated by using the candidate QP, the Lagrangian 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 MBs (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.
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