dsp_iir.h64

来自「dm642函数库」· H64 代码 · 共 124 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.                                    *;
;* ======================================================================== *;
* ========================================================================= *
*   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.                           *
* ========================================================================= *

        .global _DSP_iir

* ========================================================================= *
*   End of file:  dsp_iir.h64                                               *
* ------------------------------------------------------------------------- *
*             Copyright (c) 2003 Texas Instruments, Incorporated.           *
*                            All Rights Reserved.                           *
* ========================================================================= *