;* ======================================================================== *;
;* TEXAS INSTRUMENTS, INC. *;
;* *;
;* DSPLIB DSP Signal Processing Library *;
;* *;
;* Release: Version 1.02 *;
;* CVS Revision: 1.5 Fri Mar 22 00:59:57 2002 (UTC) *;
;* Snapshot date: 18-Apr-2002 *;
;* *;
;* This library contains proprietary intellectual property of Texas *;
;* Instruments, Inc. The library and its source code are protected by *;
;* various copyrights, and portions may also be protected by patents or *;
;* other legal protections. *;
;* *;
;* This software is licensed for use with Texas Instruments TMS320 *;
;* family DSPs. This license was provided to you prior to installing *;
;* the software. You may review this license by consulting the file *;
;* TI_license.PDF which accompanies the files in this library. *;
;* ------------------------------------------------------------------------ *;
;* Copyright (C) 2002 Texas Instruments, Incorporated. *;
;* All Rights Reserved. *;
;* ======================================================================== *;
* ========================================================================= *
* *
* TEXAS INSTRUMENTS, INC. *
* *
* NAME *
* DSP_autocor *
* *
* REVISION DATE *
* 21-Mar-2002 *
* *
* USAGE *
* This routine has the following C prototype: *
* *
* void DSP_autocor *
* ( *
* short *restrict r, *
* const short *restrict x, *
* int nx, *
* int nr *
* ) *
* *
* r[nr] : Output array. *
* x[nr+nx]: Input array. *
* Must be word aligned. *
* nx : Length of autocorrelation. *
* Must be multiple of 8. *
* nr : Number of lags. *
* Must be multiple of 2. *
* *
* DESCRIPTION *
* This routine performs an autocorrelation of an input vector *
* x. The length of the autocorrelation is nx samples. Since nr *
* such autocorrelations are performed, input vector x needs to be *
* of length nx + nr. This produces nr output results which are *
* stored in an output array r. *
* *
* The following diagram illustrates how the correlations are *
* obtained. *
* *
* Example for nr=8, nx=24: *
* 0 nr nx+nr-1 *
* |-------|----------------------| <- x[] *
* | |----------------------| -> r[0] *
* | |----------------------| -> r[1] *
* | |----------------------| -> r[2] *
* | |----------------------| -> r[3] *
* | |----------------------| -> r[4] *
* | |----------------------| -> r[5] *
* | |----------------------| -> r[6] *
* *
* Note that x[0] is never used, but is required for padding to make *
* x[nr] word aligned. *
* *
* C CODE *
* void autcor(short r[],short x[], int nx, int nr) *
* { *
* int i,k,sum; *
* *
* for (i = 0; i < nr; i++) *
* { *
* sum = 0; *
* for (k = nr; k < nx+nr; k++) *
* sum += x[k] * x[k-i]; *
* r[i] = (sum >> 15); *
* } *
* } *
* *
* TECHNIQUES *
* The inner loop is unrolled eight times thus the length of *
* the input array must be a multiple of eight. The outer *
* loop is unrolled twice so the length of output array must *
* be a multiple of 2. *
* *
* The outer loop is conditionally executed in parallel with the *
* inner loop. This allows for a zero overhead outer loop. *
* *
* ASSUMPTIONS *
* nx must be a multiple of 8 *
* nr must be a multiple of 2 *
* x[] must be word aligned *
* No alignment restrictions on r[] *
* *
* MEMORY NOTE *
* nr/2 - 1 memory hits occur. *
* This code is a LITTLE ENDIAN implementation. *
* *
* NOTES *
* This code is interrupt tolerant but not interuptible. *
* *
* CYCLES *
* nr * nx /2 + 31 + (nr/2 - 1) *
* *
* For nx = 24, nr = 8: 130 cycles *
* For nx = 40, nr = 10: 237 cycles *
* *
* CODESIZE *
* 544 bytes *
* *
* ------------------------------------------------------------------------- *
* Copyright (c) 2002 Texas Instruments, Incorporated. *
* All Rights Reserved. *
* ========================================================================= *
.global _DSP_autocor
* ========================================================================= *
* End of file: dsp_autocor.h62 *
* ------------------------------------------------------------------------- *
* Copyright (c) 2002 Texas Instruments, Incorporated. *
* All Rights Reserved. *
* ========================================================================= *