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/* 
   ITU-T G.729 Annex C+ - Reference C code for floating point 
                         implementation of G.729 Annex C+ 
                         (integration of Annexes B, D and E) 
                          Version 2.1 of October 1999 
*/ 
/* 
 File : DECLAGCP.C 
*/ 
#include "typedef.h" 
#include "ld8k.h" 
#include "ld8cp.h" 
 
/*------------------------------------------------------------------------* 
*    Function dec_lag3cp                                                 * 
*             ~~~~~~~~                                                   * 
*   Decoding of fractional pitch lag with 1/3 resolution.                * 
* See "enc_lag3.c" for more details about the encoding procedure.        * 
*------------------------------------------------------------------------*/ 
 
void dec_lag3cp(   /* Decode the pitch lag                   */ 
                int index,       /* input : received pitch index           */ 
                int pit_min,     /* input : minimum pitch lag              */ 
                int pit_max,     /* input : maximum pitch lag              */ 
                int i_subfr,     /* input : subframe flag                  */ 
                int *T0,         /* output: integer part of pitch lag      */ 
                int *T0_frac,    /* output: fractional part of pitch lag   */ 
                int rate 
                ) 
{ 
    int i; 
    int T0_min, T0_max; 
     
    if (i_subfr == 0)                  /* if 1st subframe */ 
    { 
        if (index < 197) 
        { 
            *T0 = (index+2)/3 + 19; 
            *T0_frac = index - *T0*3 + 58; 
        } 
        else 
        { 
            *T0 = index - 112; 
            *T0_frac = 0; 
        } 
    } 
     
    else  /* second subframe */ 
    { 
        /* find T0_min and T0_max for 2nd subframe */ 
         
        T0_min = *T0 - 5; 
        if (T0_min < pit_min) 
            T0_min = pit_min; 
         
        T0_max = T0_min + 9; 
        if(T0_max > pit_max) 
        { 
            T0_max = pit_max; 
            T0_min = T0_max -9; 
        } 
         
         
        if (rate == G729D) {  /* 4 bit lag in 2nd subframe (6.4 kbit/s) */ 
             
            index = index & 15; /* 4 bits delta lag; assure only 4 bits used */ 
            if (index <= 3) { 
                *T0 = T0_min + index; 
                *T0_frac = 0; 
            } 
            else if (index < 12) { 
                *T0_frac = index % 3; 
                *T0 = (index - *T0_frac) / 3 + T0_min + 2; 
                if (*T0_frac == 2) { 
                    *T0_frac = -1; 
                    (*T0)++; 
                } 
            } 
            else { 
                *T0 = T0_min + 6 + index - 12; 
                *T0_frac = 0; 
            } 
        } 
        else {          /* 5 bit lag in 2nd subframe */ 
            i = (index+2)/3 - 1; 
            *T0 = i + T0_min; 
            *T0_frac = index - 2 - i*3; 
        } 
 
    } 
     
     
    return; 
}