Rate control of MPEG video for consistent picture quality

In this paper, we propose a rate control scheme using a rate-distortion (R-D) estimation model, which produces a consistent picture quality between consecutive frames. The R-D estimation used in our rate control scheme offers a closed-form mathematical model that enables us to predict the bits and the distortion generated from an encoded frame at a given quantization parameter (QP) and vice versa. The most attractive feature of the R-D estimation is the low complexity of computing the R-D data. Furthermore, it is accurate enough to be applied to practical video coding. In our simulation, the estimation errors for the rate and the distortion are less than 2.5% and 1.5%, respectively. Therefore, the proposed rate control scheme using this R-D estimation model is appropriate for applications requiring low delay and low complexity, and able to control the output bit-rate and quality accurately. Our rate control scheme ensures that the video buffers do not underflow and overflow by satisfying the buffer constraint and additionally prevents quality difference between consecutive frames from exceeding a demanded certain level by adopting the distortion constraint. In addition, a consistent picture quality is maintained within a frame and error propagation that is caused by quality degradation of anchor frames is reduced by differentiating the control procedure for the anchor frames from that for the nonanchor frames. Simulation results show that our control scheme achieves 0.52-1.84 dB peak signal-to-noise ratio (PSNR) gain over MPEG-2 Test Model 5 (TM5) rate control and maintains very consistent quality within a frame as well as between frames.