+
−/*
+
−********************************************************************************
+
−*
+
−*      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             : enc_lag3.c
+
−*      Purpose          : Encoding of fractional pitch lag with 1/3 resolution.
+
−*
+
−********************************************************************************
+
−*/
+
−/*
+
−********************************************************************************
+
−*                         MODULE INCLUDE FILE AND VERSION ID
+
−********************************************************************************
+
−*/
+
−#include "namespace.h"
+
−#include "enc_lag3.h"
+
− 
+
−/*
+
−********************************************************************************
+
−*                         INCLUDE FILES
+
−********************************************************************************
+
−*/
+
−#include "typedef.h"
+
−#include "basic_op.h"
+
−#include "no_count.h"
+
−#include "cnst.h"
+
−
+
−/*
+
−********************************************************************************
+
−*                         PUBLIC PROGRAM CODE
+
−********************************************************************************
+
−*/
+
−/*************************************************************************
+
− *
+
− *   FUNCTION:  Enc_lag3
+
− *
+
− *   PURPOSE:  Encoding of fractional pitch lag with 1/3 resolution.
+
− *
+
− *   DESCRIPTION:
+
− *                    First and third subframes:
+
− *                    --------------------------
+
− *   The pitch range is divided as follows:
+
− *           19 1/3  to   84 2/3   resolution 1/3
+
− *           85      to   143      resolution 1
+
− *
+
− *   The period is encoded with 8 bits.
+
− *   For the range with fractions:
+
− *     index = (T-19)*3 + frac - 1;
+
− *                         where T=[19..85] and frac=[-1,0,1]
+
− *   and for the integer only range
+
− *     index = (T - 85) + 197;        where T=[86..143]
+
− *
+
− *                    Second and fourth subframes:
+
− *                    ----------------------------
+
− *   For the 2nd and 4th subframes a resolution of 1/3 is always used,
+
− *   and the search range is relative to the lag in previous subframe.
+
− *   If t0 is the lag in the previous subframe then
+
− *   t_min=t0-5   and  t_max=t0+4   and  the range is given by
+
− *        t_min - 2/3   to  t_max + 2/3
+
− *
+
− *   The period in the 2nd (and 4th) subframe is encoded with 5 bits:
+
− *     index = (T-(t_min-1))*3 + frac - 1;
+
− *                 where T=[t_min-1..t_max+1]
+
− *
+
− *************************************************************************/
+
−Word16
+
−Enc_lag3(                /* o  : Return index of encoding             */
+
−    Word16 T0,           /* i  : Pitch delay                          */
+
−    Word16 T0_frac,      /* i  : Fractional pitch delay               */
+
−    Word16 T0_prev,      /* i  : Integer pitch delay of last subframe */
+
−    Word16 T0_min,       /* i  : minimum of search range              */
+
−    Word16 T0_max,       /* i  : maximum of search range              */
+
−    Word16 delta_flag,   /* i  : Flag for 1st (or 3rd) subframe       */
+
−    Word16 flag4         /* i  : Flag for encoding with 4 bits        */
+
−    )
+
−{
+
−   Word16 index, i, tmp_ind, uplag;
+
−   Word16 tmp_lag;
+
−   
+
−   test (); 
+
−   if (delta_flag == 0)
+
−   {  /* if 1st or 3rd subframe */
+
−
+
−      /* encode pitch delay (with fraction) */
+
−      
+
−      test (); 
+
−      if (sub (T0, 85) <= 0)
+
−      {
+
−         /* index = T0*3 - 58 + T0_frac   */
+
−         i = add (add (T0, T0), T0);
+
−         index = add (sub (i, 58), T0_frac);
+
−      }
+
−      else
+
−      {
+
−         index = add (T0, 112);
+
−      }
+
−   }
+
−   else
+
−   {   /* if second or fourth subframe */
+
−      test (); 
+
−      if (flag4 == 0) {
+
−
+
−         /* 'normal' encoding: either with 5 or 6 bit resolution */
+
−
+
−         /* index = 3*(T0 - T0_min) + 2 + T0_frac */
+
−         i = sub (T0, T0_min);
+
−         i = add (add (i, i), i);
+
−         index = add (add (i, 2), T0_frac);
+
−      }
+
−      else {
+
−         
+
−         /* encoding with 4 bit resolution */
+
−         
+
−         tmp_lag = T0_prev;                                   move16 ();
+
−
+
−         test ();
+
−         if ( sub( sub(tmp_lag, T0_min), 5) > 0)
+
−            tmp_lag = add (T0_min, 5);
+
−         test ();
+
−         if ( sub( sub(T0_max, tmp_lag), 4) > 0)
+
−            tmp_lag = sub (T0_max, 4);
+
−         
+
−         uplag = add (add (add (T0, T0), T0), T0_frac);
+
−         
+
−         i = sub (tmp_lag, 2);
+
−         tmp_ind = add (add (i, i), i);
+
−         
+
−         test ();
+
−         if (sub (tmp_ind, uplag) >= 0) { 
+
−            index = add (sub (T0, tmp_lag), 5);
+
−         } 
+
−         else
+
−         {
+
−            i = add (tmp_lag, 1);
+
−            i = add (add (i, i), i);
+
−
+
−            test ();
+
−            if (sub (i, uplag) > 0) {
+
−                index = add ( sub (uplag, tmp_ind), 3);                
+
−            }
+
−            else {
+
−               index = add (sub (T0, tmp_lag), 11);
+
−            }
+
−         }
+
−         
+
−      } /* end if (encoding with 4 bit resolution) */
+
−   }   /* end if (second of fourth subframe) */
+
−   
+
−   return index;
+
−}