Frame bit allocation for H.264 using Cauchy-distribution based source modelling

Based on the observation that a Cauchy density is more accurate in estimating the distribution of the AC coefficients than the traditional Laplacian density for H.264 video coders, a rate model with improved accuracy is derived. Using the new rate model, a frame bit-allocation algorithm for the rate control of an H.264 video coder is developed. Extensive analysis with carefully selected anchor video sequences demonstrates a 0.43 dB average PSNR improvement over the JM 8.4 rate control algorithm, and a 0.27 dB average PSNR improvement over the TM5-based bit-allocation algorithm that has recently been proposed for H.264 by S. Ma et al. (see Proc. 2003 Int. Conf. Image Process., ICIP '03, vol.3, p.793-6, 2003). The analysis also demonstrates 20% and 60% reductions in PSNR variation among the encoded pictures when compared to the JM 8.4 rate control algorithm and the TM5-based bit-allocation algorithm, respectively.