"TMS320C55x DSP Library DSPLIB Programmer's Reference"

acorracorrFunctionArgumentsAutocorrelationushort oflag = acorr (DATA *x, DATA *r, ushort nx, ushort nr, type)(defined in araw.asm, abias.asm , aubias.asm)x [nx]Pointer to real input vector of nx real elements. nx ≥ nrr [nr]nxnrtypeoflagPointer to real output vector containing the first nr elementsof the positive side of the autocorrelation function of vectora. r must be different than a (in-place computation is notallowed).Number of real elements in vector xNumber of real elements in vector rAutocorrelation type selector. Types supported: If type = raw, r contains the raw autocorrelation of x If type = bias, r contains the biased autocorrelation of x If type = unbias, r contains the unbiased autocorrelation ofxOverflow flag. If oflag = 1, a 32-bit overflow has occurred If oflag = 0, a 32-bit overflow has not occurredDescriptionAlgorithmComputes the first nr points of the positive side of the autocorrelation of thereal vector x and stores the results in real output vector r. The full-length autocorrelationof vector x will have 2*nx–1 points with even symmetry around thelag 0 point (r[0]). This routine provides only the positive half of this for memoryand computational savings.Raw Autocorrelationr[j] nxj1k0x[j k] x[k]0 j nrBiased Autocorrelationr[j] nx 1 nxj1 x[j k] x[k]k00 j nrUnbiased Autocorrelationr[j] 1(nx abs(j))nxj1k0x[j k] x[k]0 j nrFunction Descriptions4-7