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long_term.c

/*
 * Copyright 1992 by Jutta Degener and Carsten Bormann, Technische
 * Universitaet Berlin.  See the accompanying file "COPYRIGHT" for
 * details.  THERE IS ABSOLUTELY NO WARRANTY FOR THIS SOFTWARE.
 */

/* $Header: /tmp_amd/presto/export/kbs/jutta/src/gsm/RCS/long_term.c,v 1.6 1996/07/02 12:33:19 jutta Exp $ */

#include <stdio.h>
#include <assert.h>

#include "private.h"

#include "gsm.h"
#include "proto.h"

/*
 *  4.2.11 .. 4.2.12 LONG TERM PREDICTOR (LTP) SECTION
 */


/*
 * This module computes the LTP gain (bc) and the LTP lag (Nc)
 * for the long term analysis filter.   This is done by calculating a
 * maximum of the cross-correlation function between the current
 * sub-segment short term residual signal d[0..39] (output of
 * the short term analysis filter; for simplification the index
 * of this array begins at 0 and ends at 39 for each sub-segment of the
 * RPE-LTP analysis) and the previous reconstructed short term
 * residual signal dp[ -120 .. -1 ].  A dynamic scaling must be
 * performed to avoid overflow.
 */

 /* The next procedure exists in six versions.  First two integer
  * version (if USE_FLOAT_MUL is not defined); then four floating
  * point versions, twice with proper scaling (USE_FLOAT_MUL defined),
  * once without (USE_FLOAT_MUL and FAST defined, and fast run-time
  * option used).  Every pair has first a Cut version (see the -C
  * option to toast or the LTP_CUT option to gsm_option()), then the
  * uncut one.  (For a detailed explanation of why this is altogether
  * a bad idea, see Henry Spencer and Geoff Collyer, ``#ifdef Considered
  * Harmful''.)
  */

#ifndef  USE_FLOAT_MUL

#ifdef      LTP_CUT

static void Cut_Calculation_of_the_LTP_parameters P5((st, d,dp,bc_out,Nc_out),

      struct gsm_state * st,

      register word     * d,        /* [0..39]  IN    */
      register word     * dp,       /* [-120..-1]     IN    */
      word        * bc_out,   /*          OUT   */
      word        * Nc_out    /*          OUT   */
)
{
      register int      k, lambda;
      word        Nc, bc;
      word        wt[40];

      longword    L_result;
      longword    L_max, L_power;
      word        R, S, dmax, scal, best_k;
      word        ltp_cut;

      register word     temp, wt_k;

      /*  Search of the optimum scaling of d[0..39].
       */
      dmax = 0;
      for (k = 0; k <= 39; k++) {
            temp = d[k];
            temp = GSM_ABS( temp );
            if (temp > dmax) {
                  dmax = temp;
                  best_k = k;
            }
      }
      temp = 0;
      if (dmax == 0) scal = 0;
      else {
            assert(dmax > 0);
            temp = gsm_norm( (longword)dmax << 16 );
      }
      if (temp > 6) scal = 0;
      else scal = 6 - temp;
      assert(scal >= 0);

      /* Search for the maximum cross-correlation and coding of the LTP lag
       */
      L_max = 0;
      Nc    = 40; /* index for the maximum cross-correlation */
      wt_k  = SASR(d[best_k], scal);

      for (lambda = 40; lambda <= 120; lambda++) {
            L_result = (longword)wt_k * dp[best_k - lambda];
            if (L_result > L_max) {
                  Nc    = lambda;
                  L_max = L_result;
            }
      }
      *Nc_out = Nc;
      L_max <<= 1;

      /*  Rescaling of L_max
       */
      assert(scal <= 100 && scal >= -100);
      L_max = L_max >> (6 - scal);  /* sub(6, scal) */

      assert( Nc <= 120 && Nc >= 40);

      /*   Compute the power of the reconstructed short term residual
       *   signal dp[..]
       */
      L_power = 0;
      for (k = 0; k <= 39; k++) {

            register longword L_temp;

            L_temp   = SASR( dp[k - Nc], 3 );
            L_power += L_temp * L_temp;
      }
      L_power <<= 1;    /* from L_MULT */

      /*  Normalization of L_max and L_power
       */

      if (L_max <= 0)  {
            *bc_out = 0;
            return;
      }
      if (L_max >= L_power) {
            *bc_out = 3;
            return;
      }

      temp = gsm_norm( L_power );

      R = SASR( L_max   << temp, 16 );
      S = SASR( L_power << temp, 16 );

      /*  Coding of the LTP gain
       */

      /*  Table 4.3a must be used to obtain the level DLB[i] for the
       *  quantization of the LTP gain b to get the coded version bc.
       */
      for (bc = 0; bc <= 2; bc++) if (R <= gsm_mult(S, gsm_DLB[bc])) break;
      *bc_out = bc;
}

#endif      /* LTP_CUT */

static void Calculation_of_the_LTP_parameters P4((d,dp,bc_out,Nc_out),
      register word     * d,        /* [0..39]  IN    */
      register word     * dp,       /* [-120..-1]     IN    */
      word        * bc_out,   /*          OUT   */
      word        * Nc_out    /*          OUT   */
)
{
      register int      k, lambda;
      word        Nc, bc;
      word        wt[40];

      longword    L_max, L_power;
      word        R, S, dmax, scal;
      register word     temp;

      /*  Search of the optimum scaling of d[0..39].
       */
      dmax = 0;

      for (k = 0; k <= 39; k++) {
            temp = d[k];
            temp = GSM_ABS( temp );
            if (temp > dmax) dmax = temp;
      }

      temp = 0;
      if (dmax == 0) scal = 0;
      else {
            assert(dmax > 0);
            temp = gsm_norm( (longword)dmax << 16 );
      }

      if (temp > 6) scal = 0;
      else scal = 6 - temp;

      assert(scal >= 0);

      /*  Initialization of a working array wt
       */

      for (k = 0; k <= 39; k++) wt[k] = SASR( d[k], scal );

      /* Search for the maximum cross-correlation and coding of the LTP lag
       */
      L_max = 0;
      Nc    = 40; /* index for the maximum cross-correlation */

      for (lambda = 40; lambda <= 120; lambda++) {

# undef STEP
#           define STEP(k)    (longword)wt[k] * dp[k - lambda]

            register longword L_result;

            L_result  = STEP(0)  ; L_result += STEP(1) ;
            L_result += STEP(2)  ; L_result += STEP(3) ;
            L_result += STEP(4)  ; L_result += STEP(5)  ;
            L_result += STEP(6)  ; L_result += STEP(7)  ;
            L_result += STEP(8)  ; L_result += STEP(9)  ;
            L_result += STEP(10) ; L_result += STEP(11) ;
            L_result += STEP(12) ; L_result += STEP(13) ;
            L_result += STEP(14) ; L_result += STEP(15) ;
            L_result += STEP(16) ; L_result += STEP(17) ;
            L_result += STEP(18) ; L_result += STEP(19) ;
            L_result += STEP(20) ; L_result += STEP(21) ;
            L_result += STEP(22) ; L_result += STEP(23) ;
            L_result += STEP(24) ; L_result += STEP(25) ;
            L_result += STEP(26) ; L_result += STEP(27) ;
            L_result += STEP(28) ; L_result += STEP(29) ;
            L_result += STEP(30) ; L_result += STEP(31) ;
            L_result += STEP(32) ; L_result += STEP(33) ;
            L_result += STEP(34) ; L_result += STEP(35) ;
            L_result += STEP(36) ; L_result += STEP(37) ;
            L_result += STEP(38) ; L_result += STEP(39) ;

            if (L_result > L_max) {

                  Nc    = lambda;
                  L_max = L_result;
            }
      }

      *Nc_out = Nc;

      L_max <<= 1;

      /*  Rescaling of L_max
       */
      assert(scal <= 100 && scal >=  -100);
      L_max = L_max >> (6 - scal);  /* sub(6, scal) */

      assert( Nc <= 120 && Nc >= 40);

      /*   Compute the power of the reconstructed short term residual
       *   signal dp[..]
       */
      L_power = 0;
      for (k = 0; k <= 39; k++) {

            register longword L_temp;

            L_temp   = SASR( dp[k - Nc], 3 );
            L_power += L_temp * L_temp;
      }
      L_power <<= 1;    /* from L_MULT */

      /*  Normalization of L_max and L_power
       */

      if (L_max <= 0)  {
            *bc_out = 0;
            return;
      }
      if (L_max >= L_power) {
            *bc_out = 3;
            return;
      }

      temp = gsm_norm( L_power );

      R = SASR( L_max   << temp, 16 );
      S = SASR( L_power << temp, 16 );

      /*  Coding of the LTP gain
       */

      /*  Table 4.3a must be used to obtain the level DLB[i] for the
       *  quantization of the LTP gain b to get the coded version bc.
       */
      for (bc = 0; bc <= 2; bc++) if (R <= gsm_mult(S, gsm_DLB[bc])) break;
      *bc_out = bc;
}

#else /* USE_FLOAT_MUL */

#ifdef      LTP_CUT

static void Cut_Calculation_of_the_LTP_parameters P5((st, d,dp,bc_out,Nc_out),
      struct gsm_state * st,        /*              IN      */
      register word     * d,        /* [0..39]  IN    */
      register word     * dp,       /* [-120..-1]     IN    */
      word        * bc_out,   /*          OUT   */
      word        * Nc_out    /*          OUT   */
)
{
      register int      k, lambda;
      word        Nc, bc;
      word        ltp_cut;

      float       wt_float[40];
      float       dp_float_base[120], * dp_float = dp_float_base + 120;

      longword    L_max, L_power;
      word        R, S, dmax, scal;
      register word     temp;

      /*  Search of the optimum scaling of d[0..39].
       */
      dmax = 0;

      for (k = 0; k <= 39; k++) {
            temp = d[k];
            temp = GSM_ABS( temp );
            if (temp > dmax) dmax = temp;
      }

      temp = 0;
      if (dmax == 0) scal = 0;
      else {
            assert(dmax > 0);
            temp = gsm_norm( (longword)dmax << 16 );
      }

      if (temp > 6) scal = 0;
      else scal = 6 - temp;

      assert(scal >= 0);
      ltp_cut = (longword)SASR(dmax, scal) * st->ltp_cut / 100; 


      /*  Initialization of a working array wt
       */

      for (k = 0; k < 40; k++) {
            register word w = SASR( d[k], scal );
            if (w < 0 ? w > -ltp_cut : w < ltp_cut) {
                  wt_float[k] = 0.0;
            }
            else {
                  wt_float[k] =  w;
            }
      }
      for (k = -120; k <  0; k++) dp_float[k] =  dp[k];

      /* Search for the maximum cross-correlation and coding of the LTP lag
       */
      L_max = 0;
      Nc    = 40; /* index for the maximum cross-correlation */

      for (lambda = 40; lambda <= 120; lambda += 9) {

            /*  Calculate L_result for l = lambda .. lambda + 9.
             */
            register float *lp = dp_float - lambda;

            register float    W;
            register float    a = lp[-8], b = lp[-7], c = lp[-6],
                        d = lp[-5], e = lp[-4], f = lp[-3],
                        g = lp[-2], h = lp[-1];
            register float  E; 
            register float  S0 = 0, S1 = 0, S2 = 0, S3 = 0, S4 = 0,
                        S5 = 0, S6 = 0, S7 = 0, S8 = 0;

#           undef STEP
#           define      STEP(K, a, b, c, d, e, f, g, h) \
                  if ((W = wt_float[K]) != 0.0) {     \
                  E = W * a; S8 += E;           \
                  E = W * b; S7 += E;           \
                  E = W * c; S6 += E;           \
                  E = W * d; S5 += E;           \
                  E = W * e; S4 += E;           \
                  E = W * f; S3 += E;           \
                  E = W * g; S2 += E;           \
                  E = W * h; S1 += E;           \
                  a  = lp[K];             \
                  E = W * a; S0 += E; } else (a = lp[K])

#           define      STEP_A(K)   STEP(K, a, b, c, d, e, f, g, h)
#           define      STEP_B(K)   STEP(K, b, c, d, e, f, g, h, a)
#           define      STEP_C(K)   STEP(K, c, d, e, f, g, h, a, b)
#           define      STEP_D(K)   STEP(K, d, e, f, g, h, a, b, c)
#           define      STEP_E(K)   STEP(K, e, f, g, h, a, b, c, d)
#           define      STEP_F(K)   STEP(K, f, g, h, a, b, c, d, e)
#           define      STEP_G(K)   STEP(K, g, h, a, b, c, d, e, f)
#           define      STEP_H(K)   STEP(K, h, a, b, c, d, e, f, g)

            STEP_A( 0); STEP_B( 1); STEP_C( 2); STEP_D( 3);
            STEP_E( 4); STEP_F( 5); STEP_G( 6); STEP_H( 7);

            STEP_A( 8); STEP_B( 9); STEP_C(10); STEP_D(11);
            STEP_E(12); STEP_F(13); STEP_G(14); STEP_H(15);

            STEP_A(16); STEP_B(17); STEP_C(18); STEP_D(19);
            STEP_E(20); STEP_F(21); STEP_G(22); STEP_H(23);

            STEP_A(24); STEP_B(25); STEP_C(26); STEP_D(27);
            STEP_E(28); STEP_F(29); STEP_G(30); STEP_H(31);

            STEP_A(32); STEP_B(33); STEP_C(34); STEP_D(35);
            STEP_E(36); STEP_F(37); STEP_G(38); STEP_H(39);

            if (S0 > L_max) { L_max = S0; Nc = lambda;     }
            if (S1 > L_max) { L_max = S1; Nc = lambda + 1; }
            if (S2 > L_max) { L_max = S2; Nc = lambda + 2; }
            if (S3 > L_max) { L_max = S3; Nc = lambda + 3; }
            if (S4 > L_max) { L_max = S4; Nc = lambda + 4; }
            if (S5 > L_max) { L_max = S5; Nc = lambda + 5; }
            if (S6 > L_max) { L_max = S6; Nc = lambda + 6; }
            if (S7 > L_max) { L_max = S7; Nc = lambda + 7; }
            if (S8 > L_max) { L_max = S8; Nc = lambda + 8; }

      }
      *Nc_out = Nc;

      L_max <<= 1;

      /*  Rescaling of L_max
       */
      assert(scal <= 100 && scal >=  -100);
      L_max = L_max >> (6 - scal);  /* sub(6, scal) */

      assert( Nc <= 120 && Nc >= 40);

      /*   Compute the power of the reconstructed short term residual
       *   signal dp[..]
       */
      L_power = 0;
      for (k = 0; k <= 39; k++) {

            register longword L_temp;

            L_temp   = SASR( dp[k - Nc], 3 );
            L_power += L_temp * L_temp;
      }
      L_power <<= 1;    /* from L_MULT */

      /*  Normalization of L_max and L_power
       */

      if (L_max <= 0)  {
            *bc_out = 0;
            return;
      }
      if (L_max >= L_power) {
            *bc_out = 3;
            return;
      }

      temp = gsm_norm( L_power );

      R = SASR( L_max   << temp, 16 );
      S = SASR( L_power << temp, 16 );

      /*  Coding of the LTP gain
       */

      /*  Table 4.3a must be used to obtain the level DLB[i] for the
       *  quantization of the LTP gain b to get the coded version bc.
       */
      for (bc = 0; bc <= 2; bc++) if (R <= gsm_mult(S, gsm_DLB[bc])) break;
      *bc_out = bc;
}

#endif /* LTP_CUT */

static void Calculation_of_the_LTP_parameters P4((d,dp,bc_out,Nc_out),
      register word     * d,        /* [0..39]  IN    */
      register word     * dp,       /* [-120..-1]     IN    */
      word        * bc_out,   /*          OUT   */
      word        * Nc_out    /*          OUT   */
)
{
      register int      k, lambda;
      word        Nc, bc;

      float       wt_float[40];
      float       dp_float_base[120], * dp_float = dp_float_base + 120;

      longword    L_max, L_power;
      word        R, S, dmax, scal;
      register word     temp;

      /*  Search of the optimum scaling of d[0..39].
       */
      dmax = 0;

      for (k = 0; k <= 39; k++) {
            temp = d[k];
            temp = GSM_ABS( temp );
            if (temp > dmax) dmax = temp;
      }

      temp = 0;
      if (dmax == 0) scal = 0;
      else {
            assert(dmax > 0);
            temp = gsm_norm( (longword)dmax << 16 );
      }

      if (temp > 6) scal = 0;
      else scal = 6 - temp;

      assert(scal >= 0);

      /*  Initialization of a working array wt
       */

      for (k =    0; k < 40; k++) wt_float[k] =  SASR( d[k], scal );
      for (k = -120; k <  0; k++) dp_float[k] =  dp[k];

      /* Search for the maximum cross-correlation and coding of the LTP lag
       */
      L_max = 0;
      Nc    = 40; /* index for the maximum cross-correlation */

      for (lambda = 40; lambda <= 120; lambda += 9) {

            /*  Calculate L_result for l = lambda .. lambda + 9.
             */
            register float *lp = dp_float - lambda;

            register float    W;
            register float    a = lp[-8], b = lp[-7], c = lp[-6],
                        d = lp[-5], e = lp[-4], f = lp[-3],
                        g = lp[-2], h = lp[-1];
            register float  E; 
            register float  S0 = 0, S1 = 0, S2 = 0, S3 = 0, S4 = 0,
                        S5 = 0, S6 = 0, S7 = 0, S8 = 0;

#           undef STEP
#           define      STEP(K, a, b, c, d, e, f, g, h) \
                  W = wt_float[K];        \
                  E = W * a; S8 += E;           \
                  E = W * b; S7 += E;           \
                  E = W * c; S6 += E;           \
                  E = W * d; S5 += E;           \
                  E = W * e; S4 += E;           \
                  E = W * f; S3 += E;           \
                  E = W * g; S2 += E;           \
                  E = W * h; S1 += E;           \
                  a  = lp[K];             \
                  E = W * a; S0 += E

#           define      STEP_A(K)   STEP(K, a, b, c, d, e, f, g, h)
#           define      STEP_B(K)   STEP(K, b, c, d, e, f, g, h, a)
#           define      STEP_C(K)   STEP(K, c, d, e, f, g, h, a, b)
#           define      STEP_D(K)   STEP(K, d, e, f, g, h, a, b, c)
#           define      STEP_E(K)   STEP(K, e, f, g, h, a, b, c, d)
#           define      STEP_F(K)   STEP(K, f, g, h, a, b, c, d, e)
#           define      STEP_G(K)   STEP(K, g, h, a, b, c, d, e, f)
#           define      STEP_H(K)   STEP(K, h, a, b, c, d, e, f, g)

            STEP_A( 0); STEP_B( 1); STEP_C( 2); STEP_D( 3);
            STEP_E( 4); STEP_F( 5); STEP_G( 6); STEP_H( 7);

            STEP_A( 8); STEP_B( 9); STEP_C(10); STEP_D(11);
            STEP_E(12); STEP_F(13); STEP_G(14); STEP_H(15);

            STEP_A(16); STEP_B(17); STEP_C(18); STEP_D(19);
            STEP_E(20); STEP_F(21); STEP_G(22); STEP_H(23);

            STEP_A(24); STEP_B(25); STEP_C(26); STEP_D(27);
            STEP_E(28); STEP_F(29); STEP_G(30); STEP_H(31);

            STEP_A(32); STEP_B(33); STEP_C(34); STEP_D(35);
            STEP_E(36); STEP_F(37); STEP_G(38); STEP_H(39);

            if (S0 > L_max) { L_max = S0; Nc = lambda;     }
            if (S1 > L_max) { L_max = S1; Nc = lambda + 1; }
            if (S2 > L_max) { L_max = S2; Nc = lambda + 2; }
            if (S3 > L_max) { L_max = S3; Nc = lambda + 3; }
            if (S4 > L_max) { L_max = S4; Nc = lambda + 4; }
            if (S5 > L_max) { L_max = S5; Nc = lambda + 5; }
            if (S6 > L_max) { L_max = S6; Nc = lambda + 6; }
            if (S7 > L_max) { L_max = S7; Nc = lambda + 7; }
            if (S8 > L_max) { L_max = S8; Nc = lambda + 8; }
      }
      *Nc_out = Nc;

      L_max <<= 1;

      /*  Rescaling of L_max
       */
      assert(scal <= 100 && scal >=  -100);
      L_max = L_max >> (6 - scal);  /* sub(6, scal) */

      assert( Nc <= 120 && Nc >= 40);

      /*   Compute the power of the reconstructed short term residual
       *   signal dp[..]
       */
      L_power = 0;
      for (k = 0; k <= 39; k++) {

            register longword L_temp;

            L_temp   = SASR( dp[k - Nc], 3 );
            L_power += L_temp * L_temp;
      }
      L_power <<= 1;    /* from L_MULT */

      /*  Normalization of L_max and L_power
       */

      if (L_max <= 0)  {
            *bc_out = 0;
            return;
      }
      if (L_max >= L_power) {
            *bc_out = 3;
            return;
      }

      temp = gsm_norm( L_power );

      R = SASR( L_max   << temp, 16 );
      S = SASR( L_power << temp, 16 );

      /*  Coding of the LTP gain
       */

      /*  Table 4.3a must be used to obtain the level DLB[i] for the
       *  quantization of the LTP gain b to get the coded version bc.
       */
      for (bc = 0; bc <= 2; bc++) if (R <= gsm_mult(S, gsm_DLB[bc])) break;
      *bc_out = bc;
}

#ifdef      FAST
#ifdef      LTP_CUT

static void Cut_Fast_Calculation_of_the_LTP_parameters P5((st,
                                          d,dp,bc_out,Nc_out),
      struct gsm_state * st,        /*              IN      */
      register word     * d,        /* [0..39]  IN    */
      register word     * dp,       /* [-120..-1]     IN    */
      word        * bc_out,   /*          OUT   */
      word        * Nc_out    /*          OUT   */
)
{
      register int      k, lambda;
      register float    wt_float;
      word        Nc, bc;
      word        wt_max, best_k, ltp_cut;

      float       dp_float_base[120], * dp_float = dp_float_base + 120;

      register float    L_result, L_max, L_power;

      wt_max = 0;

      for (k = 0; k < 40; ++k) {
            if      ( d[k] > wt_max) wt_max =  d[best_k = k];
            else if (-d[k] > wt_max) wt_max = -d[best_k = k];
      }

      assert(wt_max >= 0);
      wt_float = (float)wt_max;

      for (k = -120; k < 0; ++k) dp_float[k] = (float)dp[k];

      /* Search for the maximum cross-correlation and coding of the LTP lag
       */
      L_max = 0;
      Nc    = 40; /* index for the maximum cross-correlation */

      for (lambda = 40; lambda <= 120; lambda++) {
            L_result = wt_float * dp_float[best_k - lambda];
            if (L_result > L_max) {
                  Nc    = lambda;
                  L_max = L_result;
            }
      }

      *Nc_out = Nc;
      if (L_max <= 0.)  {
            *bc_out = 0;
            return;
      }

      /*  Compute the power of the reconstructed short term residual
       *  signal dp[..]
       */
      dp_float -= Nc;
      L_power = 0;
      for (k = 0; k < 40; ++k) {
            register float f = dp_float[k];
            L_power += f * f;
      }

      if (L_max >= L_power) {
            *bc_out = 3;
            return;
      }

      /*  Coding of the LTP gain
       *  Table 4.3a must be used to obtain the level DLB[i] for the
       *  quantization of the LTP gain b to get the coded version bc.
       */
      lambda = L_max / L_power * 32768.;
      for (bc = 0; bc <= 2; ++bc) if (lambda <= gsm_DLB[bc]) break;
      *bc_out = bc;
}

#endif /* LTP_CUT */

static void Fast_Calculation_of_the_LTP_parameters P4((d,dp,bc_out,Nc_out),
      register word     * d,        /* [0..39]  IN    */
      register word     * dp,       /* [-120..-1]     IN    */
      word        * bc_out,   /*          OUT   */
      word        * Nc_out    /*          OUT   */
)
{
      register int      k, lambda;
      word        Nc, bc;

      float       wt_float[40];
      float       dp_float_base[120], * dp_float = dp_float_base + 120;

      register float    L_max, L_power;

      for (k = 0; k < 40; ++k) wt_float[k] = (float)d[k];
      for (k = -120; k < 0; ++k) dp_float[k] = (float)dp[k];

      /* Search for the maximum cross-correlation and coding of the LTP lag
       */
      L_max = 0;
      Nc    = 40; /* index for the maximum cross-correlation */

      for (lambda = 40; lambda <= 120; lambda += 9) {

            /*  Calculate L_result for l = lambda .. lambda + 9.
             */
            register float *lp = dp_float - lambda;

            register float    W;
            register float    a = lp[-8], b = lp[-7], c = lp[-6],
                        d = lp[-5], e = lp[-4], f = lp[-3],
                        g = lp[-2], h = lp[-1];
            register float  E; 
            register float  S0 = 0, S1 = 0, S2 = 0, S3 = 0, S4 = 0,
                        S5 = 0, S6 = 0, S7 = 0, S8 = 0;

#           undef STEP
#           define      STEP(K, a, b, c, d, e, f, g, h) \
                  W = wt_float[K];        \
                  E = W * a; S8 += E;           \
                  E = W * b; S7 += E;           \
                  E = W * c; S6 += E;           \
                  E = W * d; S5 += E;           \
                  E = W * e; S4 += E;           \
                  E = W * f; S3 += E;           \
                  E = W * g; S2 += E;           \
                  E = W * h; S1 += E;           \
                  a  = lp[K];             \
                  E = W * a; S0 += E

#           define      STEP_A(K)   STEP(K, a, b, c, d, e, f, g, h)
#           define      STEP_B(K)   STEP(K, b, c, d, e, f, g, h, a)
#           define      STEP_C(K)   STEP(K, c, d, e, f, g, h, a, b)
#           define      STEP_D(K)   STEP(K, d, e, f, g, h, a, b, c)
#           define      STEP_E(K)   STEP(K, e, f, g, h, a, b, c, d)
#           define      STEP_F(K)   STEP(K, f, g, h, a, b, c, d, e)
#           define      STEP_G(K)   STEP(K, g, h, a, b, c, d, e, f)
#           define      STEP_H(K)   STEP(K, h, a, b, c, d, e, f, g)

            STEP_A( 0); STEP_B( 1); STEP_C( 2); STEP_D( 3);
            STEP_E( 4); STEP_F( 5); STEP_G( 6); STEP_H( 7);

            STEP_A( 8); STEP_B( 9); STEP_C(10); STEP_D(11);
            STEP_E(12); STEP_F(13); STEP_G(14); STEP_H(15);

            STEP_A(16); STEP_B(17); STEP_C(18); STEP_D(19);
            STEP_E(20); STEP_F(21); STEP_G(22); STEP_H(23);

            STEP_A(24); STEP_B(25); STEP_C(26); STEP_D(27);
            STEP_E(28); STEP_F(29); STEP_G(30); STEP_H(31);

            STEP_A(32); STEP_B(33); STEP_C(34); STEP_D(35);
            STEP_E(36); STEP_F(37); STEP_G(38); STEP_H(39);

            if (S0 > L_max) { L_max = S0; Nc = lambda;     }
            if (S1 > L_max) { L_max = S1; Nc = lambda + 1; }
            if (S2 > L_max) { L_max = S2; Nc = lambda + 2; }
            if (S3 > L_max) { L_max = S3; Nc = lambda + 3; }
            if (S4 > L_max) { L_max = S4; Nc = lambda + 4; }
            if (S5 > L_max) { L_max = S5; Nc = lambda + 5; }
            if (S6 > L_max) { L_max = S6; Nc = lambda + 6; }
            if (S7 > L_max) { L_max = S7; Nc = lambda + 7; }
            if (S8 > L_max) { L_max = S8; Nc = lambda + 8; }
      }
      *Nc_out = Nc;

      if (L_max <= 0.)  {
            *bc_out = 0;
            return;
      }

      /*  Compute the power of the reconstructed short term residual
       *  signal dp[..]
       */
      dp_float -= Nc;
      L_power = 0;
      for (k = 0; k < 40; ++k) {
            register float f = dp_float[k];
            L_power += f * f;
      }

      if (L_max >= L_power) {
            *bc_out = 3;
            return;
      }

      /*  Coding of the LTP gain
       *  Table 4.3a must be used to obtain the level DLB[i] for the
       *  quantization of the LTP gain b to get the coded version bc.
       */
      lambda = L_max / L_power * 32768.;
      for (bc = 0; bc <= 2; ++bc) if (lambda <= gsm_DLB[bc]) break;
      *bc_out = bc;
}

#endif      /* FAST      */
#endif      /* USE_FLOAT_MUL */


/* 4.2.12 */

static void Long_term_analysis_filtering P6((bc,Nc,dp,d,dpp,e),
      word        bc,   /*                            IN  */
      word        Nc,   /*                            IN  */
      register word     * dp, /* previous d     [-120..-1]        IN  */
      register word     * d,  /* d        [0..39]                 IN  */
      register word     * dpp,      /* estimate [0..39]                 OUT */
      register word     * e   /* long term res. signal [0..39]    OUT */
)
/*
 *  In this part, we have to decode the bc parameter to compute
 *  the samples of the estimate dpp[0..39].  The decoding of bc needs the
 *  use of table 4.3b.  The long term residual signal e[0..39]
 *  is then calculated to be fed to the RPE encoding section.
 */
{
      register int      k;
      register longword ltmp;

#     undef STEP
#     define STEP(BP)                           \
      for (k = 0; k <= 39; k++) {               \
            dpp[k]  = GSM_MULT_R( BP, dp[k - Nc]);    \
            e[k]  = GSM_SUB( d[k], dpp[k] );    \
      }

      switch (bc) {
      case 0:     STEP(  3277 ); break;
      case 1:     STEP( 11469 ); break;
      case 2: STEP( 21299 ); break;
      case 3: STEP( 32767 ); break; 
      }
}

void Gsm_Long_Term_Predictor P7((S,d,dp,e,dpp,Nc,bc),       /* 4x for 160 samples */

      struct gsm_state  * S,

      word  * d,  /* [0..39]   residual signal  IN    */
      word  * dp, /* [-120..-1] d'        IN    */

      word  * e,  /* [0..39]              OUT   */
      word  * dpp,      /* [0..39]              OUT   */
      word  * Nc, /* correlation lag            OUT   */
      word  * bc  /* gain factor                OUT   */
)
{
      assert( d  ); assert( dp ); assert( e  );
      assert( dpp); assert( Nc ); assert( bc );

#if defined(FAST) && defined(USE_FLOAT_MUL)
      if (S->fast) 
#if   defined (LTP_CUT)
            if (S->ltp_cut)
                  Cut_Fast_Calculation_of_the_LTP_parameters(S,
                        d, dp, bc, Nc);
            else
#endif /* LTP_CUT */
                  Fast_Calculation_of_the_LTP_parameters(d, dp, bc, Nc );
      else 
#endif /* FAST & USE_FLOAT_MUL */
#ifdef LTP_CUT
            if (S->ltp_cut)
                  Cut_Calculation_of_the_LTP_parameters(S, d, dp, bc, Nc);
            else
#endif
                  Calculation_of_the_LTP_parameters(d, dp, bc, Nc);

      Long_term_analysis_filtering( *bc, *Nc, dp, d, dpp, e );
}

/* 4.3.2 */
void Gsm_Long_Term_Synthesis_Filtering P5((S,Ncr,bcr,erp,drp),
      struct gsm_state  * S,

      word              Ncr,
      word              bcr,
      register word           * erp,         /* [0..39]                  IN */
      register word           * drp    /* [-120..-1] IN, [-120..40] OUT */
)
/*
 *  This procedure uses the bcr and Ncr parameter to realize the
 *  long term synthesis filtering.  The decoding of bcr needs
 *  table 4.3b.
 */
{
      register longword ltmp; /* for ADD */
      register int            k;
      word              brp, drpp, Nr;

      /*  Check the limits of Nr.
       */
      Nr = Ncr < 40 || Ncr > 120 ? S->nrp : Ncr;
      S->nrp = Nr;
      assert(Nr >= 40 && Nr <= 120);

      /*  Decoding of the LTP gain bcr
       */
      brp = gsm_QLB[ bcr ];

      /*  Computation of the reconstructed short term residual 
       *  signal drp[0..39]
       */
      assert(brp != MIN_WORD);

      for (k = 0; k <= 39; k++) {
            drpp   = GSM_MULT_R( brp, drp[ k - Nr ] );
            drp[k] = GSM_ADD( erp[k], drpp );
      }

      /*
       *  Update of the reconstructed short term residual signal
       *  drp[ -1..-120 ]
       */

      for (k = 0; k <= 119; k++) drp[ -120 + k ] = drp[ -80 + k ];
}

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