An Efficient Bit Allocation Strategy in AC-3 Encoder

As a significant perceptual audio coding standard, AC-3 has been widely applied in such areas as DTV and etc. The bit allocation module in AC-3 encoder plays a decisive role to the quality of the whole audio encoder. In this paper, based on the quantitative analysis of the SNRoffset, the theory deduction is provided, and formula to estimate the relation between the volume of bit allocation and the volume of SNRoffset is obtained, so that the optimal value of SNRoffset could be approached effectively. Then, based on the deduction, an efficient algorithm of the bit allocation is presented according the first degree approximation and the convergence control. Finally, several experiments are conducted which mainly focus on two parameters: the iteration times and the number of bit left, which weigh the accuracy and efficiency respectively. The experiment results show that this algorithm can both greatly enhance the accuracy and efficiency of the bit allocation in AC-3 encoder.