An efficient approach for conversion between arbitrary sampling frequencies

An efficient technique is introduced for conversion between arbitrary input and output sampling frequencies, denoted by F_in and F_out. The overall system consists of two basic building blocks. In the first block, the sampling rate is increased by an integer ratio L using a linear-phase multistage FIR interpolator, resulting in the sampling frequency of LF_in. In the second block, the output of this interpolator is first filtered by R parallel linear-phase FIR branch filters. The desired output samples at time instants m/F_out for m=0, 1, ... are then found in three steps. The first step involves finding at the output of each branch filter the largest existing sample point n/(LF_in) which is less than or equal to the desired time instant m/F_out. In the second step, the corresponding output samples of the branch filters are multiplied by γ(^r-1) where r=1, 2, ···, R for the first, second, ..., and for the Rth branch and γ=2LF_in[m/F_out-n/(LF_in)]-1. The desired sample at the time instant m/F_out is finally obtained by adding the results of the second step. Examples are included illustrating the efficiency of the proposed approach compared to other existing techniques