fir-flat.c

来自「Reference Implementation of G.711 standa」· C语言 代码 · 共 733 行 · 第 1/2 页

/*                                                         v2.2 16.MAY.97 18H00
  =============================================================================

                          U    U   GGG    SSSS  TTTTT
                          U    U  G       S       T
                          U    U  G  GG   SSSS    T
                          U    U  G   G       S   T
                           UUU     GG     SSS     T

                   ========================================
                    ITU-T - USER'S GROUP ON SOFTWARE TOOLS
                   ========================================

       =============================================================
       COPYRIGHT NOTE: This source code, and all of its derivations,
       is subject to the "ITU-T General Public License". Please have
       it  read  in    the  distribution  disk,   or  in  the  ITU-T
       Recommendation G.191 on "SOFTWARE TOOLS FOR SPEECH AND  AUDIO
       CODING STANDARDS".
       =============================================================

MODULE:         FIRFLT, HIGH QUALITY FIR UP/DOWN-SAMPLING FILTER
                Sub-unit: Flat-weighting filters, LP and BP

ORIGINAL BY:
 	Chris Tate <[e-mail]>
	John Barnes <[e-mail]>
	Rudolf Hofmann <[e-mail]>
        Simao Ferraz de Campos Neto <[e-mail]>

DESCRIPTION:
        This file contains procedures for flat-weighting low-pass and 
	high-pass filters, with rate factors of 2 and 3 for both up-
	and down-sampling.

FUNCTIONS:
  Global (have prototype in firflt.h)
         = hq_down_2_to_1_init() :  initialize down-sampling filter 2:1
         = hq_down_3_to_1_init() :  initialize down-sampling filter 3:1
         = hq_up_1_to_2_init()   :  initialize   up-sampling filter 1:2
         = hq_up_1_to_3_init()   :  initialize   up-sampling filter 1:3
         = linear_phase_pb_2_to_1_init()
         = linear_phase_pb_1_to_2_init()
         = linear_phase_pb_1_to_1_init()

  Local (should be used only here -- prototypes only in this file)
         = fill_lp_2_to_1(...)   : filling filter coefficients into
                                   array for flat low pass, factor 2:1
         = fill_lp_3_to_1(...)   : idem, for flat low pass, factor 3:1
         = fill_flat_band_pass(...): idem, for linear-phase band-pass 



HISTORY:
    16.Dec.91 v0.1 First beta-version <[e-mail]>
    28.Feb.92 v1.0 Release of 1st version to UGST <[e-mail]>
    20.Apr.94 v2.0 Added new filtering routines: modified IRS at 16kHz and
                   48kHz, Delta-SM, Linear-phase band-pass.
                   <[e-mail]>
    30.Sep.94 v2.1 Updated to accomodate changes in the name of the name and
                   slitting of module in several files, for ease of expansion.
    ** THIS FILE WAS SPLIT FROM THE ORIGINAL .C FILE **
    16.May.97 v2.2 Added function for HQ flat bandpass keeping the sampling
                   rate (1:1 factor)
  =============================================================================
*/


/*
 * ......... INCLUDES .........
 */
#include <stdio.h>
#ifndef VMS
#include <stdlib.h>		/* General utility definitions */
#endif

#include "firflt.h"		/* Global definitions for FIR-FIR filter */


/*
 * ......... Local function prototypes .........
 */

void fill_lp_2_to_1 ARGS((float *h0[], long *lenh0));
void fill_lp_3_to_1 ARGS((float **h0, long *lenh0));
void fill_flat_band_pass ARGS((float **h0, long *lenh0));


/* 
 * ..... Private function prototypes defined in other sub-unit ..... 
 */
extern SCD_FIR *fir_initialization ARGS((long lenh0, float h0[], double gain, 
                                                 long idwnup, int hswitch));


/*
 * ...................... BEGIN OF FUNCTIONS .........................
 */


/*
  ============================================================================

        SCD_FIR *hq_down_2_to_1_init (void);
        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~

        Description:
        ~~~~~~~~~~~~

        Initialization routine for high quality FIR downsampling filter
        by factor of 2.

        Parameters:  none.
        ~~~~~~~~~~~

        Return value:
        ~~~~~~~~~~~~~
        Returns a pointer to struct SCD_FIR;

        Author: <[e-mail]>
        ~~~~~~~

        History:
        ~~~~~~~~
        28.Feb.92 v1.0 Release of 1st version <[e-mail]>

 ============================================================================
*/
SCD_FIR        *hq_down_2_to_1_init()
{
  float          *h0;		/* pointer to array with FIR coeff. */
  long            lenh0;	/* number of FIR coefficients */


  /* allocate array for FIR coeff. and fill with coefficients */
  fill_lp_2_to_1(&h0, &lenh0);

  return
    fir_initialization(		/* Returns: pointer to SCD_FIR-struct */
		       lenh0,	/* In: number of FIR-coefficients */
		       h0,	/* In: pointer to array with FIR-cof. */
		       1.0,	/* In: gain factor for FIR-coeffic. */
		       2l,	/* In: Down-sampling factor */
		       'D'	/* In: switch to down-sampling kernel */
    );
}
/* ..................... End of hq_down_2_to_1_init() ..................... */



/*
  ============================================================================

        SCD_FIR *hq_up_1_to_2_init (void);
        ~~~~~~~~~~~~~~~~~~~~~~~~~~

        Description:
        ~~~~~~~~~~~~

        Initialization routine for high quality upsampling FIR filter
        by factor of 2.

        Parameters:  none.
        ~~~~~~~~~~~

        Return value:
        ~~~~~~~~~~~~~
        Returns a pointer to struct SCD_FIR;

        Author: <[e-mail]>
        ~~~~~~~

        History:
        ~~~~~~~~
        28.Feb.92 v1.0 Release of 1st version <[e-mail]>

 ============================================================================
*/
SCD_FIR        *hq_up_1_to_2_init()
{
  float          *h0;		/* pointer to array with FIR coeff. */
  long            lenh0;	/* number of FIR coefficients */


  /* allocate array for FIR coeff. and fill with coefficients */
  fill_lp_2_to_1(&h0, &lenh0);

  return
    fir_initialization(		/* Returns: pointer to SCD_FIR-struct */
		       lenh0,	/* In: number of FIR-coefficients */
		       h0,	/* In: pointer to array with FIR-cof. */
		       2.0,	/* In: gain factor for FIR-coeffic. */
		       2l,	/* In: Up-sampling factor */
		       'U'	/* In: Switch to upsampling procedure */
    );
}
/* ..................... End of hq_up_1_to_2_init() ..................... */



/*
  ============================================================================

        SCD_FIR *hq_down_3_to_1_init (void);
        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~

        Description:
        ~~~~~~~~~~~~

        Initialization routine for high quality FIR downsampling filter
        by factor of 3.

        Parameters:  none.
        ~~~~~~~~~~~

        Return value:
        ~~~~~~~~~~~~~
        Returns a pointer to struct SCD_FIR;

        Author: <[e-mail]>
        ~~~~~~~

        History:
        ~~~~~~~~
        28.Feb.92 v1.0 Release of 1st version <[e-mail]>

 ============================================================================
*/
SCD_FIR        *hq_down_3_to_1_init()
{
  float          *h0;		/* pointer to array with FIR coeff. */
  long            lenh0;	/* number of FIR coefficients */


  /* allocate array for FIR coeff. and fill with coefficients */
  fill_lp_3_to_1(&h0, &lenh0);

  return
    fir_initialization(		/* Returns: pointer to SCD_FIR-struct */
		       lenh0,	/* In: number of FIR-coefficients */
		       h0,	/* In: pointer to array with FIR-cof. */
		       1.0,	/* In: gain factor for FIR-coeffic. */
		       3l,	/* In: Down-sampling factor */
		       'D'	/* In: switch to down-sampling proc. */
    );
}
/* .................... End of hq_down_3_to_1_init() ..................... */



/*
  ============================================================================

        SCD_FIR *hq_up_1_to_3_init (void);
        ~~~~~~~~~~~~~~~~~~~~~~~~~~

        Description:
        ~~~~~~~~~~~~

        Initialization routine for high quality FIR upsampling filter
        by factor of 3.

        Parameters:  none.
        ~~~~~~~~~~~

        Return value:
        ~~~~~~~~~~~~~
        Returns a pointer to struct SCD_FIR;

        Author: <[e-mail]>
        ~~~~~~~

        History:
        ~~~~~~~~
        28.Feb.92 v1.0 Release of 1st version <[e-mail]>

 ============================================================================
*/
SCD_FIR        *hq_up_1_to_3_init()
{
  float          *h0;		/* pointer to array with FIR coeff. */
  long            lenh0;	/* number of FIR coefficients */


  /* allocate array for FIR coeff. and fill with coefficients */
  fill_lp_3_to_1(&h0, &lenh0);

  return
    fir_initialization(		/* Returns: pointer to SCD_FIR-struct */
		       lenh0,	/* In: number of FIR-coefficients */
		       h0,	/* In: pointer to array with FIR-cof. */
		       3.0,	/* In: gain factor for FIR-coeffic. */
		       3l,	/* In: Up-sampling factor */
		       'U'	/* In: switch to upsampling procedure */
    );
}
/* ...................... End of hq_up_1_to_3_init() ...................... */


/*
  ============================================================================

        void fill_lp_2_to_1 (float **h0, long *lenh0);
        ~~~~~~~~~~~~~~~~~~~

        Description:
        ~~~~~~~~~~~~

        Initialize pointer to array with of FIR coefficients of a low
        pass filter for up/down sampling filter with factor 2:1 or 1:2
        and 24-bit representation.

        Parameters:
        ~~~~~~~~~~~
        h0:    (Out) pointer to array with FIR coefficients
        lenh0: (Out) pointer to number of coefficients


        Return value:
        ~~~~~~~~~~~~~
        None.

        Author: <[e-mail]>
        ~~~~~~~

        History:
        ~~~~~~~~
        28.Feb.92 v1.0 Release of 1st version <[e-mail]>

 ============================================================================
*/
#define f24 (float)0x00800000
#define lenh02 118

void            fill_lp_2_to_1(h0, lenh0)
  float          *h0[];
  long           *lenh0;
{
  static float    h02[lenh02] = {
    1584. / f24, 805. / f24, -4192. / f24, -8985. / f24,
    -5987. / f24, 2583. / f24, 4657. / f24, -3035. / f24,
    -7004. / f24, 1542. / f24, 8969. / f24, 567. / f24,
    -10924. / f24, -3757. / f24, 12320. / f24, 7951. / f24,
    -12793. / f24, -13048. / f24, 11923. / f24, 18793. / f24,
    -9331. / f24, -24802. / f24, 4694. / f24, 30570. / f24,
    2233. / f24, -35439. / f24, -11526. / f24, 38680. / f24,
    23114. / f24, -39474. / f24, -36701. / f24, 36999. / f24,
    51797. / f24, -30419. / f24, -67658. / f24, 18962. / f24,
    83318. / f24, -1927. / f24, -97566. / f24, -21284. / f24,
    108971. / f24, 51215. / f24, -115837. / f24, -88430. / f24,
    116130. / f24, 133716. / f24, -107253. / f24, -188497. / f24,
    85497. / f24, 255795. / f24, -44643. / f24, -342699. / f24,
    -28185. / f24, 468096. / f24, 167799. / f24, -696809. / f24,
    -519818. / f24, 1446093. / f24, 3562497. / f24, 3562497. / f24,
    1446093. / f24, -519818. / f24, -696809. / f24, 167799. / f24,
    468096. / f24, -28185. / f24, -342699. / f24, -44643. / f24,
    255795. / f24, 85497. / f24, -188497. / f24, -107253. / f24,
    133716. / f24, 116130. / f24, -88430. / f24, -115837. / f24,
    51215. / f24, 108971. / f24, -21284. / f24, -97566. / f24,
    -1927. / f24, 83318. / f24, 18962. / f24, -67658. / f24,
    -30419. / f24, 51797. / f24, 36999. / f24, -36701. / f24,
    -39474. / f24, 23114. / f24, 38680. / f24, -11526. / f24,
    -35439. / f24, 2233. / f24, 30570. / f24, 4694. / f24,
    -24802. / f24, -9331. / f24, 18793. / f24, 11923. / f24,
    -13048. / f24, -12793. / f24, 7951. / f24, 12320. / f24,
    -3757. / f24, -10924. / f24, 567. / f24, 8969. / f24,
    1542. / f24, -7004. / f24, -3035. / f24, 4657. / f24,