+
−/*************************************************************************
+
−*
+
−*      GSM AMR-NB speech codec   R98   Version 7.6.0   December 12, 2001
+
−*                                R99   Version 3.3.0                
+
−*                                REL-4 Version 4.1.0                
+
−*
+
−********************************************************************************
+
−*
+
−*      File             : pstfilt.c
+
−*      Purpose          : Performs adaptive postfiltering on the synthesis
+
−*                       : speech
+
−*
+
−********************************************************************************
+
−*/
+
−
+
−/*
+
−********************************************************************************
+
−*                         MODULE INCLUDE FILE AND VERSION ID
+
−********************************************************************************
+
−*/
+
−#include "namespace.h"
+
−#include "pstfilt.h"
+
− 
+
−/*
+
−********************************************************************************
+
−*                         INCLUDE FILES
+
−********************************************************************************
+
−*/
+
−#include "tw_amr.h"
+
−#include "typedef.h"
+
−#include "basic_op.h"
+
−#include "memops.h"
+
−#include "weight_a.h"
+
−#include "residu.h"
+
−#include "syn_filt.h"
+
−#include "preemph.h"
+
−#include "no_count.h"
+
−#include "cnst.h"
+
−
+
−/*
+
−********************************************************************************
+
−*                         LOCAL VARIABLES AND TABLES
+
−********************************************************************************
+
−*/
+
−/*---------------------------------------------------------------*
+
− *    Postfilter constant parameters (defined in "cnst.h")       *
+
− *---------------------------------------------------------------*
+
− *   L_FRAME     : Frame size.                                   *
+
− *   L_SUBFR     : Sub-frame size.                               *
+
− *   M           : LPC order.                                    *
+
− *   MP1         : LPC order+1                                   *
+
− *   MU          : Factor for tilt compensation filter           *
+
− *   AGC_FAC     : Factor for automatic gain control             *
+
− *---------------------------------------------------------------*/
+
−
+
−#define L_H 22  /* size of truncated impulse response of A(z/g1)/A(z/g2) */
+
−
+
−/* Spectral expansion factors */
+
−static const Word16 gamma3_MR122[M] = {
+
−  22938, 16057, 11240, 7868, 5508,
+
−  3856, 2699, 1889, 1322, 925
+
−};
+
−
+
−static const Word16 gamma3[M] = {
+
−  18022, 9912, 5451, 2998, 1649, 907, 499, 274, 151, 83
+
−};
+
−
+
−static const Word16 gamma4_MR122[M] = {
+
−  24576, 18432, 13824, 10368, 7776,
+
−  5832, 4374, 3281, 2461, 1846
+
−};
+
−
+
−static const Word16 gamma4[M] = {
+
−  22938, 16057, 11240, 7868, 5508, 3856, 2699, 1889, 1322, 925
+
−};
+
−
+
−/*
+
−********************************************************************************
+
−*                         PUBLIC PROGRAM CODE
+
−********************************************************************************
+
−*/
+
−
+
−/*************************************************************************
+
−*
+
−*  Function:   Post_Filter_reset
+
−*  Purpose:    Initializes state memory to zero
+
−*
+
−**************************************************************************
+
−*/
+
−void Post_Filter_reset (Post_FilterState *state)
+
−{
+
−  Set_zero (state->mem_syn_pst, M);
+
−  Set_zero (state->res2, L_SUBFR);
+
−  Set_zero (state->synth_buf, L_FRAME + M);
+
−  agc_reset(&state->agc_state);
+
−  preemphasis_reset(&state->preemph_state);
+
−}
+
−
+
−/*
+
−**************************************************************************
+
−*  Function:  Post_Filter
+
−*  Purpose:   postfiltering of synthesis speech.
+
−*  Description:
+
−*      The postfiltering process is described as follows:
+
−*
+
−*          - inverse filtering of syn[] through A(z/0.7) to get res2[]
+
−*          - tilt compensation filtering; 1 - MU*k*z^-1
+
−*          - synthesis filtering through 1/A(z/0.75)
+
−*          - adaptive gain control
+
−*
+
−**************************************************************************
+
−*/
+
−int Post_Filter (
+
−    Post_FilterState *st, /* i/o : post filter states                        */
+
−    enum Mode mode,       /* i   : AMR mode                                  */
+
−    Word16 *syn,          /* i/o : synthesis speech (postfiltered is output) */
+
−    Word16 *Az_4          /* i   : interpolated LPC parameters in all subfr. */
+
−)
+
−{
+
−    /*-------------------------------------------------------------------*
+
−     *           Declaration of parameters                               *
+
−     *-------------------------------------------------------------------*/
+
−
+
−    Word16 Ap3[MP1], Ap4[MP1];  /* bandwidth expanded LP parameters */
+
−    Word16 *Az;                 /* pointer to Az_4:                 */
+
−                                /*  LPC parameters in each subframe */
+
−    Word16 i_subfr;             /* index for beginning of subframe  */
+
−    Word16 h[L_H];
+
−
+
−    Word16 i;
+
−    Word16 temp1, temp2;
+
−    Word32 L_tmp;
+
−    Word16 *syn_work = &st->synth_buf[M]; move16 ();
+
−
+
−    /*-----------------------------------------------------*
+
−     * Post filtering                                      *
+
−     *-----------------------------------------------------*/
+
−
+
−    Copy (syn, syn_work , L_FRAME);
+
−
+
−    Az = Az_4;
+
−
+
−    for (i_subfr = 0; i_subfr < L_FRAME; i_subfr += L_SUBFR)
+
−    {
+
−       /* Find weighted filter coefficients Ap3[] and ap[4] */
+
−
+
−       test (); test ();
+
−       if (sub(mode, MR122) == 0 || sub(mode, MR102) == 0)
+
−       {
+
−          Weight_Ai (Az, gamma3_MR122, Ap3);
+
−          Weight_Ai (Az, gamma4_MR122, Ap4);
+
−       }
+
−       else
+
−       {
+
−          Weight_Ai (Az, gamma3, Ap3);
+
−          Weight_Ai (Az, gamma4, Ap4);
+
−       }
+
−       
+
−       /* filtering of synthesis speech by A(z/0.7) to find res2[] */
+
−       
+
−       Residu (Ap3, &syn_work[i_subfr], st->res2, L_SUBFR);
+
−       
+
−       /* tilt compensation filter */
+
−       
+
−       /* impulse response of A(z/0.7)/A(z/0.75) */
+
−
+
−       Copy (Ap3, h, M + 1);
+
−       Set_zero (&h[M + 1], L_H - M - 1);
+
−       Syn_filt (Ap4, h, h, L_H, &h[M + 1], 0);
+
−        
+
−       /* 1st correlation of h[] */
+
−       
+
−       L_tmp = L_mult (h[0], h[0]);
+
−       for (i = 1; i < L_H; i++)
+
−       {
+
−          L_tmp = L_mac (L_tmp, h[i], h[i]);
+
−       }
+
−       temp1 = extract_h (L_tmp);
+
−       
+
−       L_tmp = L_mult (h[0], h[1]);
+
−       for (i = 1; i < L_H - 1; i++)
+
−       {
+
−          L_tmp = L_mac (L_tmp, h[i], h[i + 1]);
+
−       }
+
−       temp2 = extract_h (L_tmp);
+
−       
+
−       test (); 
+
−       if (temp2 <= 0)
+
−       {
+
−          temp2 = 0;          move16 (); 
+
−       }
+
−       else
+
−       {
+
−          temp2 = mult (temp2, MU);
+
−          temp2 = div_s (temp2, temp1);
+
−       }
+
−
+
−       preemphasis (&st->preemph_state, st->res2, temp2, L_SUBFR);
+
−
+
−       /* filtering through  1/A(z/0.75) */
+
−
+
−       Syn_filt (Ap4, st->res2, &syn[i_subfr], L_SUBFR, st->mem_syn_pst, 1);
+
−
+
−       /* scale output to input */
+
−
+
−       agc (&st->agc_state, &syn_work[i_subfr], &syn[i_subfr],
+
−            AGC_FAC, L_SUBFR);
+
−       
+
−       Az += MP1;
+
−    }
+
−
+
−    /* update syn_work[] buffer */
+
−
+
−    Copy (&syn_work[L_FRAME - M], &syn_work[-M], M);
+
−
+
−    return 0;
+
−}