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Cascaded MPEG rate control for simultaneous improvement of accuracy and quality

The often self-contradicting goals of MPEG-2 rate control are two-fold: to achieve the best video quality and maintain buffer status compliance as constrained by the channel rate and the decoder buffer size. Existing rate control algorithms use a single loop control structure at the macroblock level, and hence do not have a good mechanism in place to perform accurate picture level rate allocation and estimation. This leads to the conflict between rate control accuracy and video quality. In this paper, we propose a cascade control structure (CCS) for feedback control of bit allocation at both the picture level and the macroblock level. In addition, we combine CCS with model-based complexity estimation for better scene change handling. Simulation results show that our new rate control algorithm produces video with smoother quality and achieves accurate rate control at the same time. Performance of the encoder under scene changes is also improved.