"TMS320C55x DSP Library DSPLIB Programmer's Reference"

firinterpBenchmarks(preliminary)Cycles Core: (nx/D)*(10+nh+(D–1))Overhead 67Code size(in bytes)144firinterpInterpolating FIR FilterFunctionushort oflag = firinterp (DATA *x, DATA *h, DATA *r, DATA *dbuffer , ushort nh,ushort nx, ushort I)(defined in interp.asm)Argumentsx [nx]h[nh]r[nx*I]dbuffer[(nh/I)+1]nxPointer to real input vector of nx real elements.Pointer to coefficient vector of size nh in normalorder:H = b0 b1 b2 b3 …Pointer to real output vector of nx real elements.In-place computation (r = x) is allowedDelay buffer of (nh/I)+1 elements In the case of multiple-buffering schemes, thisarray should be initialized to 0 for the first blockonly. Between consecutive blocks, the delay bufferpreserves delayed input samples in dbuffer[1…(nh/I)+1].It also preserves a ptr to the nextnew entry into the dbuffer. This ptr is preservedacross function calls in dbuffer[0].The delay buffer is only nh/I elements and holdsonly delayed x inputs. No zero-samples are insertedinto dbuffer (since only non-zero productscontribute to the filter output)Number of real elements in vector x and rnh Number of coefficients, with (nh/I) 34-42