rpe.c

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/*
 * 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.
 */

/* $Header$ */

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

#include "private.h"

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

/*  4.2.13 .. 4.2.17  RPE ENCODING SECTION
 */

/* 4.2.13 */
#ifdef K6OPT
#include "k6opt.h"
#else
static void Weighting_filter P2((e, x),
   register word  * e,     /* signal [-5..0.39.44] IN  */
   word     * x      /* signal [0..39] OUT */
)
/*
 *  The coefficients of the weighting filter are stored in a table
 *  (see table 4.4).  The following scaling is used:
 *
 * H[0..10] = integer( real_H[ 0..10] * 8192 );
 */
{
   /* word        wt[ 50 ]; */

   register longword L_result;
   register int      k /* , i */ ;

   /*  Initialization of a temporary working array wt[0...49]
    */

   /* for (k =  0; k <=  4; k++) wt[k] = 0;
    * for (k =  5; k <= 44; k++) wt[k] = *e++;
    * for (k = 45; k <= 49; k++) wt[k] = 0;
    *
    *  (e[-5..-1] and e[40..44] are allocated by the caller,
    *  are initially zero and are not written anywhere.)
    */
   e -= 5;

   /*  Compute the signal x[0..39]
    */
   for (k = 0; k <= 39; k++) {

      L_result = 8192 >> 1;

      /* for (i = 0; i <= 10; i++) {
       * L_temp   = GSM_L_MULT( wt[k+i], gsm_H[i] );
       * L_result = GSM_L_ADD( L_result, L_temp );
       * }
       */

#undef   STEP
#define  STEP( i, H )   (e[ k + i ] * (longword)H)

      /*  Every one of these multiplications is done twice --
       *  but I don't see an elegant way to optimize this.
       *  Do you?
       */

#ifdef   STUPID_COMPILER
      L_result += STEP( 0,    -134 ) ;
      L_result += STEP( 1,    -374 )  ;
                  /* + STEP(  2,    0    )  */
      L_result += STEP( 3,    2054 ) ;
      L_result += STEP( 4,    5741 ) ;
      L_result += STEP( 5,    8192 ) ;
      L_result += STEP( 6,    5741 ) ;
      L_result += STEP( 7,    2054 ) ;
             /* + STEP( 8,    0    )  */
      L_result += STEP( 9,    -374 ) ;
      L_result += STEP( 10,   -134 ) ;
#else
      L_result +=
        STEP(  0,    -134 )
      + STEP(  1,    -374 )
        /* + STEP(   2,    0    )  */
      + STEP(  3,    2054 )
      + STEP(  4,    5741 )
      + STEP(  5,    8192 )
      + STEP(  6,    5741 )
      + STEP(  7,    2054 )
        /* + STEP(   8,    0    )  */
      + STEP(  9,    -374 )
      + STEP(10,  -134 )
      ;
#endif

      /* L_result = GSM_L_ADD( L_result, L_result ); (* scaling(x2) *)
       * L_result = GSM_L_ADD( L_result, L_result ); (* scaling(x4) *)
       *
       * x[k] = SASR( L_result, 16 );
       */

      /* 2 adds vs. >>16 => 14, minus one shift to compensate for
       * those we lost when replacing L_MULT by '*'.
       */

      L_result = SASR( L_result, 13 );
      x[k] =  (word)(  L_result < MIN_WORD ? MIN_WORD
         : (L_result > MAX_WORD ? MAX_WORD : L_result ));
   }
}
#endif /* K6OPT */

/* 4.2.14 */

static void RPE_grid_selection P3((x,xM,Mc_out),
   word     * x,     /* [0..39]     IN  */
   word     * xM,    /* [0..12]     OUT */
   word     * Mc_out /*       OUT */
)
/*
 *  The signal x[0..39] is used to select the RPE grid which is
 *  represented by Mc.
 */
{
   /* register word  temp1;   */
   register int      /* m, */  i;
   register longword L_result, L_temp;
   longword    EM;   /* xxx should be L_EM? */
   word        Mc;

   longword    L_common_0_3;

   EM = 0;
   Mc = 0;

   /* for (m = 0; m <= 3; m++) {
    * L_result = 0;
    *
    *
    * for (i = 0; i <= 12; i++) {
    *
    *    temp1    = SASR( x[m + 3*i], 2 );
    *
    *    assert(temp1 != MIN_WORD);
    *
    *    L_temp   = GSM_L_MULT( temp1, temp1 );
    *    L_result = GSM_L_ADD( L_temp, L_result );
    * }
    *
    * if (L_result > EM) {
    *    Mc = m;
    *    EM = L_result;
    * }
    * }
    */

#undef   STEP
#define  STEP( m, i )      L_temp = SASR( x[m + 3 * i], 2 );   \
            L_result += L_temp * L_temp;

   /* common part of 0 and 3 */

   L_result = 0;
   STEP( 0, 1 ); STEP( 0, 2 ); STEP( 0, 3 ); STEP( 0, 4 );
   STEP( 0, 5 ); STEP( 0, 6 ); STEP( 0, 7 ); STEP( 0, 8 );
   STEP( 0, 9 ); STEP( 0, 10); STEP( 0, 11); STEP( 0, 12);
   L_common_0_3 = L_result;

   /* i = 0 */

   STEP( 0, 0 );
   L_result <<= 1;   /* implicit in L_MULT */
   EM = L_result;

   /* i = 1 */

   L_result = 0;
   STEP( 1, 0 );
   STEP( 1, 1 ); STEP( 1, 2 ); STEP( 1, 3 ); STEP( 1, 4 );
   STEP( 1, 5 ); STEP( 1, 6 ); STEP( 1, 7 ); STEP( 1, 8 );
   STEP( 1, 9 ); STEP( 1, 10); STEP( 1, 11); STEP( 1, 12);
   L_result <<= 1;
   if (L_result > EM) {
      Mc = 1;
      EM = L_result;
   }

   /* i = 2 */

   L_result = 0;
   STEP( 2, 0 );
   STEP( 2, 1 ); STEP( 2, 2 ); STEP( 2, 3 ); STEP( 2, 4 );
   STEP( 2, 5 ); STEP( 2, 6 ); STEP( 2, 7 ); STEP( 2, 8 );
   STEP( 2, 9 ); STEP( 2, 10); STEP( 2, 11); STEP( 2, 12);
   L_result <<= 1;
   if (L_result > EM) {
      Mc = 2;
      EM = L_result;
   }

   /* i = 3 */

   L_result = L_common_0_3;
   STEP( 3, 12 );
   L_result <<= 1;
   if (L_result > EM) {
      Mc = 3;
      EM = L_result;
   }

   /**/

   /*  Down-sampling by a factor 3 to get the selected xM[0..12]
    *  RPE sequence.
    */
   for (i = 0; i <= 12; i ++) xM[i] = x[Mc + 3*i];
   *Mc_out = Mc;
}

/* 4.12.15 */

static void APCM_quantization_xmaxc_to_exp_mant P3((xmaxc,exp_out,mant_out),
   word     xmaxc,      /* IN    */
   word     * exp_out,  /* OUT   */
   word     * mant_out )   /* OUT  */
{
   word  exp, mant;

   /* Compute exponent and mantissa of the decoded version of xmaxc
    */

   exp = 0;
   if (xmaxc > 15) exp = SASR(xmaxc, 3) - 1;
   mant = xmaxc - (exp << 3);

   if (mant == 0) {
      exp  = -4;
      mant = 7;
   }
   else {
      while (mant <= 7) {
         mant = mant << 1 | 1;
         exp--;
      }
      mant -= 8;
   }

   assert( exp  >= -4 && exp <= 6 );
   assert( mant >= 0 && mant <= 7 );

   *exp_out  = exp;
   *mant_out = mant;
}

static void APCM_quantization P5((xM,xMc,mant_out,exp_out,xmaxc_out),
   word     * xM,    /* [0..12]     IN */

   word     * xMc,      /* [0..12]     OUT   */
   word     * mant_out, /*          OUT   */
   word     * exp_out,  /*       OUT   */
   word     * xmaxc_out /*       OUT   */
)
{
   int   i, itest;

   word  xmax, xmaxc, temp, temp1, temp2;
   word  exp, mant;


   /*  Find the maximum absolute value xmax of xM[0..12].
    */

   xmax = 0;
   for (i = 0; i <= 12; i++) {
      temp = xM[i];
      temp = GSM_ABS(temp);
      if (temp > xmax) xmax = temp;
   }

   /*  Qantizing and coding of xmax to get xmaxc.
    */

   exp   = 0;
   temp  = SASR( xmax, 9 );
   itest = 0;

   for (i = 0; i <= 5; i++) {

      itest |= (temp <= 0);
      temp = SASR( temp, 1 );

      assert(exp <= 5);
      if (itest == 0) exp++;     /* exp = add (exp, 1) */
   }

   assert(exp <= 6 && exp >= 0);
   temp = exp + 5;

   assert(temp <= 11 && temp >= 0);
   xmaxc = gsm_add( SASR(xmax, temp), exp << 3 );

   /*   Quantizing and coding of the xM[0..12] RPE sequence
    *   to get the xMc[0..12]
    */

   APCM_quantization_xmaxc_to_exp_mant( xmaxc, &exp, &mant );

   /*  This computation uses the fact that the decoded version of xmaxc
    *  can be calculated by using the exponent and the mantissa part of
    *  xmaxc (logarithmic table).
    *  So, this method avoids any division and uses only a scaling
    *  of the RPE samples by a function of the exponent.  A direct
    *  multiplication by the inverse of the mantissa (NRFAC[0..7]
    *  found in table 4.5) gives the 3 bit coded version xMc[0..12]
    *  of the RPE samples.
    */


   /* Direct computation of xMc[0..12] using table 4.5
    */

   assert( exp <= 4096 && exp >= -4096);
   assert( mant >= 0 && mant <= 7 );

   temp1 = 6 - exp;     /* normalization by the exponent */
   temp2 = gsm_NRFAC[ mant ];    /* inverse mantissa      */

   for (i = 0; i <= 12; i++) {

      assert(temp1 >= 0 && temp1 < 16);

      temp = xM[i] << temp1;
      temp = (word)GSM_MULT( temp, temp2 );
      temp = SASR(temp, 12);
      xMc[i] = temp + 4;      /* see note below */
   }

   /*  NOTE: This equation is used to make all the xMc[i] positive.
    */

   *mant_out  = mant;
   *exp_out   = exp;
   *xmaxc_out = xmaxc;
}

/* 4.2.16 */

static void APCM_inverse_quantization P4((xMc,mant,exp,xMp),
   register word  * xMc,   /* [0..12]        IN    */
   word     mant,
   word     exp,
   register word  * xMp)   /* [0..12]        OUT   */
/*
 *  This part is for decoding the RPE sequence of coded xMc[0..12]
 *  samples to obtain the xMp[0..12] array.  Table 4.6 is used to get
 *  the mantissa of xmaxc (FAC[0..7]).
 */
{
   int   i;
   word  temp, temp1, temp2, temp3;

   assert( mant >= 0 && mant <= 7 );

   temp1 = gsm_FAC[ mant ];   /* see 4.2-15 for mant */
   temp2 = gsm_sub( 6, exp ); /* see 4.2-15 for exp  */
   temp3 = gsm_asl( 1, gsm_sub( temp2, 1 ));

   for (i = 13; i--;) {

      assert( *xMc <= 7 && *xMc >= 0 );   /* 3 bit unsigned */

      /* temp = gsm_sub( *xMc++ << 1, 7 ); */
      temp = (*xMc++ << 1) - 7;          /* restore sign   */
      assert( temp <= 7 && temp >= -7 );  /* 4 bit signed   */

      temp <<= 12;            /* 16 bit signed  */
      temp = (word)GSM_MULT_R( temp1, temp );
      temp = GSM_ADD( temp, temp3 );
      *xMp++ = gsm_asr( temp, temp2 );
   }
}

/* 4.2.17 */

static void RPE_grid_positioning P3((Mc,xMp,ep),
   word     Mc,      /* grid position  IN */
   register word  * xMp,      /* [0..12]     IN */
   register word  * ep     /* [0..39]     OUT   */
)
/*
 *  This procedure computes the reconstructed long term residual signal
 *  ep[0..39] for the LTP analysis filter.  The inputs are the Mc
 *  which is the grid position selection and the xMp[0..12] decoded
 *  RPE samples which are upsampled by a factor of 3 by inserting zero
 *  values.
 */
{
   int   i = 13;

   assert(0 <= Mc && Mc <= 3);

        switch (Mc) {
                case 3: *ep++ = 0;
                case 2:  do {
                                *ep++ = 0;
                case 1:         *ep++ = 0;
                case 0:         *ep++ = *xMp++;
                         } while (--i);
        }
        while (++Mc < 4) *ep++ = 0;

   /*

   int i, k;
   for (k = 0; k <= 39; k++) ep[k] = 0;
   for (i = 0; i <= 12; i++) {
      ep[ Mc + (3*i) ] = xMp[i];
   }
   */
}

/* 4.2.18 */

/*  This procedure adds the reconstructed long term residual signal
 *  ep[0..39] to the estimated signal dpp[0..39] from the long term
 *  analysis filter to compute the reconstructed short term residual
 *  signal dp[-40..-1]; also the reconstructed short term residual
 *  array dp[-120..-41] is updated.
 */

#if 0 /* Has been inlined in code.c */
void Gsm_Update_of_reconstructed_short_time_residual_signal P3((dpp, ep, dp),
   word  * dpp,      /* [0...39] IN */
   word  * ep,    /* [0...39] IN */
   word  * dp)    /* [-120...-1]  IN/OUT  */
{
   int      k;

   for (k = 0; k <= 79; k++)
      dp[ -120 + k ] = dp[ -80 + k ];

   for (k = 0; k <= 39; k++)
      dp[ -40 + k ] = gsm_add( ep[k], dpp[k] );
}
#endif   /* Has been inlined in code.c */

void Gsm_RPE_Encoding P5((S,e,xmaxc,Mc,xMc),

   struct gsm_state * S,

   word  * e,     /* -5..-1][0..39][40..44   IN/OUT  */
   word  * xmaxc, /*             OUT */
   word  * Mc,    /*             OUT */
   word  * xMc)      /* [0..12]        OUT */
{
   word  x[40];
   word  xM[13], xMp[13];
   word  mant, exp;

   Weighting_filter(e, x);
   RPE_grid_selection(x, xM, Mc);

   APCM_quantization(   xM, xMc, &mant, &exp, xmaxc);
   APCM_inverse_quantization(  xMc,  mant,  exp, xMp);

   RPE_grid_positioning( *Mc, xMp, e );

}

void Gsm_RPE_Decoding P5((S, xmaxcr, Mcr, xMcr, erp),
   struct gsm_state  * S,

   word     xmaxcr,
   word     Mcr,
   word     * xMcr,  /* [0..12], 3 bits      IN */
   word     * erp  /* [0..39]       OUT   */
)
{
   word  exp, mant;
   word  xMp[ 13 ];

   APCM_quantization_xmaxc_to_exp_mant( xmaxcr, &exp, &mant );
   APCM_inverse_quantization( xMcr, mant, exp, xMp );
   RPE_grid_positioning( Mcr, xMp, erp );

}