ON THE ERROR DISTRIBUTION AND SCENE CHANGE FOR THE BIT-RATE CONTROL OF MPEG

Bit rate control, which is widely employed in a video coding system, has been proved to be an important technique used to transmit the variable rate bit stream over a fixed rate channel. In this paper, an improved MPEG-based adaptive bit rate control algorithm, which utilizes the predictive and delta modulation techniques in the regulation of quantization parameters, is proposed to smooth the error distribution in the picture layer as well as in the macroblock layer. The algorithm allocates bits hierarchically, first for the ''second'' layer, then for the ''picture'' layer and finally for the ''macroblock'' layer to ensure that both accurate bit rate and stable picture quality can be achieved. In addition, the influence of scene change is also analyzed and a strategy to avoid the picture degradation due to incorrect bit allocation after scene change is proposed. The strategy simply stops picture complexity propagation which causes an erroneous estimate of used bits in the next group of pictures (GOP) after scene change. In experimental situations, the algorithm has produced more stable picture quality and a more accurate bit rate in the macroblock layer than MPEG. The only overhead to implement this algorithm is a frame delay to logically allocate bits in the macroblock layer by picture content and hence can be ignored.