dsp_iir.h

来自「dm642函数库」· C头文件 代码 · 共 135 行

/* ======================================================================== */
/*  TEXAS INSTRUMENTS, INC.                                                 */
/*                                                                          */
/*  DSPLIB  DSP Signal Processing Library                                   */
/*                                                                          */
/*      Release:        Revision 1.04b                                      */
/*      CVS Revision:   1.8     Tue Jun 24 17:03:36 2003 (UTC)              */
/*      Snapshot date:  23-Oct-2003                                         */
/*                                                                          */
/*  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) 2003 Texas Instruments, Incorporated.             */
/*                          All Rights Reserved.                            */
/* ======================================================================== */
/* ======================================================================== */
/*  Assembler compatibility shim for assembling 4.30 and later code on      */
/*  tools prior to 4.30.                                                    */
/* ======================================================================== */
/* ======================================================================== */
/*  End of assembler compatibility shim.                                    */
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/*  TEXAS INSTRUMENTS, INC.                                                 */
/*                                                                          */
/*  NAME                                                                    */
/*      iir -- Infinite Impulse Response Filter/ ARMA filter, Hand ASM      */
/*                                                                          */
/*  REVISION DATE                                                           */
/*      29-Mar-2002                                                         */
/*                                                                          */
/*  USAGE                                                                   */
/*      This routine is C callable and can be called as:                    */
/*                                                                          */
/*      void DSP_iir                                                        */
/*      (                                                                   */
/*          short *restrict r1,                                             */
/*          const short *x,                                                 */
/*          short *restrict r2,                                             */
/*          const short *h2,                                                */
/*          const short *h1,                                                */
/*          int nr                                                          */
/*      )                                                                   */
/*                                                                          */
/*      r1[nr+4] : Output array (used).                                     */
/*      x[nr+4]  : Input array.                                             */
/*      r2[nr]   : Output array (stored).                                   */
/*      h1[5]    : 4 Autoregressive filter coefficients (h1[0] is not used) */
/*      h2[5]    : 5 Moving-average filter coefficients.                    */
/*      nr       : Number of output samples. Must be >= 8.                  */
/*                                                                          */
/*  DESCRIPTION                                                             */
/*      The IIR performs an auto-regressive moving-average (ARMA) filter    */
/*      with 4 auto-regressive filter coefficients and 5 moving-average     */
/*      filter coefficients for nr output samples. The output vector is     */
/*      stored in two locations.  This routine is used as a high pass       */
/*      filter in the VSELP vocoder.                                        */
/*                                                                          */
/*  C CODE                                                                  */
/*      void iir(short *restrict r1, const short *x, short *restrict r2,    */
/*               const short *h2, const short *h1, int nr)                  */
/*      {                                                                   */
/*          int j,i;                                                        */
/*          int sum;                                                        */
/*                                                                          */
/*          for (i=0; i<nr; i++)                                            */
/*          {                                                               */
/*              sum = h2[0] * x[4+i];                                       */
/*                 for (j = 1; j <= 4; j++)                                 */
/*                  sum += h2[j]*x[4+i-j] - h1[j]*r1[4+i-j];                */
/*              r1[4+i] = (sum >> 15);                                      */
/*              r2[i] = r1[4+i];                                            */
/*          }                                                               */
/*      }                                                                   */
/*                                                                          */
/*  TECHNIQUES                                                              */
/*      Reads to the output array to get the previous output samples        */
/*      for AR filtering are avoided by maintaining copies of the           */
/*      samples in the register file.  The accumulator for the "AR"         */
/*      part and the "FIR" part are de-coupled to break data                */
/*      dependencies.  Inner loop that iterates through the filter          */
/*      coefficients is completely unrolled.                                */
/*                                                                          */
/*      C64x multiply instructions such as DOTP2 are used for the FIR       */
/*      portion of the computation, and the lower latency MPY               */
/*      instructions are used for the IIR portion.                          */
/*                                                                          */
/*  ASSUMPTIONS                                                             */
/*      "nr" is greater than or equal to 8.                                 */
/*                                                                          */
/*      Input data array "x" contains "nr + 4" input samples to produce     */
/*      "nr" output samples.                                                */
/*                                                                          */
/*      Output array "r1" contains "nr + 4" locations, "r2" contains        */
/*      "nr" locations for storing "nr" output samples. The output          */
/*      samples are stored with an offset of 4 into the "r1" array.         */
/*                                                                          */
/*  CYCLES                                                                  */
/*      cycles = 4 * nr + 21                                                */
/*                                                                          */
/*  CODESIZE                                                                */
/*      268 bytes                                                           */
/*                                                                          */
/* ------------------------------------------------------------------------ */
/*            Copyright (c) 2003 Texas Instruments, Incorporated.           */
/*                           All Rights Reserved.                           */
/* ======================================================================== */
#ifndef DSP_IIR_H_
#define DSP_IIR_H_ 1

void DSP_iir
(
    short *restrict r1,
    const short *x,
    short *restrict r2,
    const short *h2,
    const short *h1,
    int nr
);

#endif
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/*  End of file:  dsp_iir.h                                                 */
/* ------------------------------------------------------------------------ */
/*            Copyright (c) 2003 Texas Instruments, Incorporated.           */
/*                           All Rights Reserved.                           */
/* ======================================================================== */