An efficient approach for conversion between arbitrary sampling frequencies

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Abstract
An efficient technique is introduced for conversion between arbitrary input and output sampling frequencies, denoted by F/sub in/ and F/sub 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/sub 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/sub 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/sub in/) which is less than or equal to the desired time instant m/F/sub out/. In the second step, the corresponding output samples of the branch filters are multiplied by /spl gamma/(/sup r-1/) where r=1, 2, /spl middot//spl middot//spl middot/, R for the first, second, ..., and for the Rth branch and /spl gamma/=2LF/sub in/[m/F/sub out/-n/(LF/sub in/)]-1. The desired sample at the time instant m/F/sub 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.

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