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Can someone explain the use of the fir_interp_fr16() function

Question asked by StuartC on Sep 9, 2009

I want to upsample an 8kHz signal to 48kHz, i.e. interpolate by a factor of 6.  (this is on BF52x processor)


fir_interp_fr16() function seems to do what I need, but I have a problem getting this function to work. Specifically I cannot find any explanation of the exact order of the coefficients required by this function.


I already have a set of coefficients for a low pass filter (4kHz cut off) which I have used successfully in the fir_decima_fr16() function. (to go from 48kHz to 8kHz)

If these are in the order :


    c0, c1, c2, c3, c4, c5, c6, c7, c8, c9, c10, c11, c12, c13, c14, c15, c16, c17, c18, c19, c20, c21, c22, c23, c24


What then is the order of these co-efficients that I must present to the fir_interp_fr16() function ?