/* ======================================================================== */
/* 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. */
/* ======================================================================== */
#ifndef DSP_AUTOCOR_H_
#define DSP_AUTOCOR_H_ 1
void DSP_autocor
(
short *restrict r,
const short *restrict x,
int nx,
int nr
);
#endif
/* ======================================================================== */
/* End of file: dsp_autocor.h */
/* ------------------------------------------------------------------------ */
/* Copyright (c) 2002 Texas Instruments, Incorporated. */
/* All Rights Reserved. */
/* ======================================================================== */