Macroblock quantizer selection for H.263 video coding

We consider two MSE-based strategies for selecting the best quantization parameter (Q) for each coded macroblock in H.263 video coding. In the first study, Q was adjusted to match a target mean-squared error (MSE) for each block. The goal was to avoid having large errors in a few macroblocks that detract from the overall perceived image quality. Effectively, we minimized the peak MSE over all macroblocks. In the second study, we sought to minimize the average MSE, modifying a gradient-search technique that has been applied to H.261. The choice of quantizers was limited by the H.263 syntactical constraints on changes in Q between successively-coded macroblocks. The results were compared with fixed Q encoding. The resulting sequences displayed only small perceptual differences. For the cases studied, the primary advantage of varying Q was to control the delay