Abstract: This paper presents a general procedure for determining the optimal MPEG coding strategy in terms of the selection of macroblock coding modes and quantizer scales. The two processes of coding mode decision and rate control are intimately related to each other and should be determined jointly in order to achieve optimal coding performance. We formulate the constrained optimization problem and present solutions based upon rate- distortion characteristics, or R(D) curves, for all the macroblocks that compose the picture being coded. Distortion of the entire picture is assumed to be decomposable and expressible as a function of individual macroblock distortions, with this being the objective function to minimize. The determination of the optimal solution is complicated by the MPEG differential encoding of motion vectors and dc coefficients, which introduces dependencies that carry over from macroblock to macroblock for a duration equal to the slice length. Once the upper bound in performance is calculated, it can be used to assess how well practical sub-optimum methods perform.!1
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