Simple global model of an MPEG-2 bitstream

The paper describes a simple empirical model of bitstreams produced by MPEG-2 video coders. The number of bits that represent an I- or P-frame is expressed as a function of the quantization factor Q. This model is global in the sense that it describes the total number of bits in a frame thus ignoring local bitrate variation within a frame as well as changes of Q within a frame. This five-parameter model fits well to experimental data. Four of these parameters may be fixed thus obtaining a less accurate one-parameter model that can be used for coder control. The experimental results are reported for some video test sequences in the BT.601/4CIF format encoded by an MPEG-2 MP@ML coder.