www.pudn.com > g729a.rar > BITS.C, change:1996-10-01,size:4254b


/* 
   ITU-T G.729A Speech Coder    ANSI-C Source Code 
   Version 1.1    Last modified: September 1996 
 
   Copyright (c) 1996, 
   AT&T, France Telecom, NTT, Universite de Sherbrooke 
   All rights reserved. 
*/ 
 
/*****************************************************************************/ 
/* bit stream manipulation routines                                          */ 
/*****************************************************************************/ 
#include "typedef.h" 
#include "ld8a.h" 
#include "tab_ld8a.h" 
 
/* prototypes for local functions */ 
static void  int2bin(Word16 value, Word16 no_of_bits, Word16 *bitstream); 
static Word16   bin2int(Word16 no_of_bits, Word16 *bitstream); 
 
/*---------------------------------------------------------------------------- 
 * prm2bits_ld8k -converts encoder parameter vector into vector of serial bits 
 * bits2prm_ld8k - converts serial received bits to  encoder parameter vector 
 * 
 * The transmitted parameters are: 
 * 
 *     LPC:     1st codebook           7+1 bit 
 *              2nd codebook           5+5 bit 
 * 
 *     1st subframe: 
 *          pitch period                 8 bit 
 *          parity check on 1st period   1 bit 
 *          codebook index1 (positions) 13 bit 
 *          codebook index2 (signs)      4 bit 
 *          pitch and codebook gains   4+3 bit 
 * 
 *     2nd subframe: 
 *          pitch period (relative)      5 bit 
 *          codebook index1 (positions) 13 bit 
 *          codebook index2 (signs)      4 bit 
 *          pitch and codebook gains   4+3 bit 
 *---------------------------------------------------------------------------- 
 */ 
void prm2bits_ld8k( 
 Word16   prm[],           /* input : encoded parameters  (PRM_SIZE parameters)  */ 
  Word16 bits[]            /* output: serial bits (SERIAL_SIZE ) bits[0] = bfi 
                                    bits[1] = 80 */ 
) 
{ 
   Word16 i; 
   *bits++ = SYNC_WORD;     /* bit[0], at receiver this bits indicates BFI */ 
   *bits++ = SIZE_WORD;     /* bit[1], to be compatible with hardware      */ 
 
   for (i = 0; i < PRM_SIZE; i++) 
     { 
        int2bin(prm[i], bitsno[i], bits); 
        bits += bitsno[i]; 
     } 
 
   return; 
} 
 
/*---------------------------------------------------------------------------- 
 * int2bin convert integer to binary and write the bits bitstream array 
 *---------------------------------------------------------------------------- 
 */ 
static void int2bin( 
 Word16 value,             /* input : decimal value         */ 
 Word16 no_of_bits,        /* input : number of bits to use */ 
 Word16 *bitstream         /* output: bitstream             */ 
) 
{ 
   Word16 *pt_bitstream; 
   Word16   i, bit; 
 
   pt_bitstream = bitstream + no_of_bits; 
 
   for (i = 0; i < no_of_bits; i++) 
   { 
     bit = value & (Word16)0x0001;      /* get lsb */ 
     if (bit == 0) 
         *--pt_bitstream = BIT_0; 
     else 
         *--pt_bitstream = BIT_1; 
     value >>= 1; 
   } 
} 
 
/*---------------------------------------------------------------------------- 
 *  bits2prm_ld8k - converts serial received bits to  encoder parameter vector 
 *---------------------------------------------------------------------------- 
 */ 
void bits2prm_ld8k( 
 Word16 bits[],            /* input : serial bits (80)                       */ 
 Word16   prm[]            /* output: decoded parameters (11 parameters)     */ 
) 
{ 
   Word16 i; 
   for (i = 0; i < PRM_SIZE; i++) 
     { 
        prm[i] = bin2int(bitsno[i], bits); 
        bits  += bitsno[i]; 
     } 
 
} 
 
/*---------------------------------------------------------------------------- 
 * bin2int - read specified bits from bit array  and convert to integer value 
 *---------------------------------------------------------------------------- 
 */ 
static Word16 bin2int(       /* output: decimal value of bit pattern */ 
 Word16 no_of_bits,          /* input : number of bits to read       */ 
 Word16 *bitstream           /* input : array containing bits        */ 
) 
{ 
   Word16   value, i; 
   Word16 bit; 
 
   value = 0; 
   for (i = 0; i < no_of_bits; i++) 
   { 
     value <<= 1; 
     bit = *bitstream++; 
     if (bit == BIT_1)  value += 1; 
   } 
   return(value); 
}