Modeling of ITU-T G.729 codec with bit-width optimization for intensive computation blocks

In this work, ITU-T G.729 speech codec is precisely modeled using basic building blocks of SIMULINK such as simple adders and multipliers. Therefore, a golden model of the codec which best suits as a reference for its hardware implementation is developed. In a custom hardware design, the precision of the computations, i.e. the optimum number of the bits of the computational blocks should be calculated. The optimum number of the bits of the computational blocks is the minimum word-width that maintains the quality of the output with minimum chip area. Three blocks are selected to extract their bit-true models. The optimum bit-width of the coefficients and the internal computations are measured. These blocks are the pre-processing block, the open loop pitch estimator, and the fixed codebook search block. The former is important in terms of error propagation to the output and the two others are the blocks that demand the most computational power respectively. As such, these blocks are suitable choices to be hardware implemented in a hardware-software co-design project.