A customer at Indesign has some questions regarding the DSP_iir function of the DSPLIB for C64x:
"I am trying to implement an iir filter using TMS TMS320DM6446. I studied the DSP_iir function from the DSPLIB64x+ library. In the title of DSP_iir it says IIR with 5 Coefficients. That is what I am used to, 5 coefficients per biquad. Later it explains that the number of biquads are given by nh/4, and also it expects that nh being a multiple of 8. Does this mean that the first coefficient(b0) for each biquad is omitted because it is always 1. Therefore we have 4 coefficients per biquads two for b's and 2 for a's. Also if the order of filter is 6 is it possibe to add an all pass biquad to it to make it look like an 8th order, so that we have four second order biquads each with 8 b and 8 a coefficients to satisfy the nh multiple of 8 restrication. I have looked at the example program in C:\CCStudio_v3.3\c64plus\dsplib_v210\src\DSP_iir\DSP_iir_d.c. I don't understand the reason for the zero padding. Could you explain. Do you have another example that is using DSP_iir function? I appriciate your help"
I have not done that much work with the DSPLIB functions, can anyone help with this? Do we have another example?
