decod.c

语音编解码算法G.723.1的C语言算法原代码

#include <stdlib.h>
#include <stdio.h>
#include <string.h>

#include "typedef.h"
#include "basop.h"
#include "cst_lbc.h"
#include "tab_lbc.h"
#include "lbccodec.h"
#include "decod.h"
#include "util_lbc.h"
#include "lpc.h"
#include "lsp.h"
#include "exc_lbc.h"

/*
   The following structure contains all the static decoder
      variables.
*/

DECSTATDEF  DecStat  ;


/*
**
** Function:        Init_Decod()
** 
** Description:     Initializes non-zero state variables
**          for the decoder.
**
** Links to text:   Section 3.11
** 
** Arguments:       None
** 
** Outputs:     None
** 
** Return value:    None
** 
*/
void  Init_Decod( )
{
   int   i  ;

   /* Initialize encoder data structure with zeros */
   memset(&DecStat, 0, sizeof(DECSTATDEF));

   /* Initialize the previously decoded LSP vector to the DC vector */
   for ( i = 0 ; i < LpcOrder ; i ++ )
      DecStat.PrevLsp[i] = LspDcTable[i] ;

   /* Initialize the gain scaling unit memory to a constant */
   DecStat.Gain = (Word16) 0x1000 ;

    return;
}


/*
**
** Function:        Decod()
**
** Description:     Implements G.723 dual-rate decoder for  a frame 
**          of speech
**
** Links to text:   Section 3
** 
** Arguments:
**      
**  Word16 *DataBuff    Empty buffer
**  Word16 Vinp[]       Encoded frame (22/26 bytes) 
** 

** Outputs:
**
**  Word16 DataBuff[]   Decoded frame (480 bytes)
** 
** Return value:
** 
**  Flag            Always True
** 
*/

Flag    Decod( Word16 *DataBuff, char *Vinp, Word16 Crc )
{
    int   i,j   ;
    int n;
    Word32   Senr ;
    Word16   QntLpc[SubFrames*LpcOrder] ;
    Word16   AcbkCont[SubFrLen] ;

    Word16   LspVect[LpcOrder] ;
    Word16   Temp[PitchMax+Frame] ;
    Word16  *Dpnt ;

    LINEDEF  Line ;
    PFDEF    Pf[SubFrames] ;

    /*
    * Decode the packed bitstream for the frame.  (Text: Section 4;
    * parts of sections 2.17, 2.18)
    */
    Line = Line_Unpk( Vinp, Crc ) ;

    /* 
    * Update the frame erasure count (Text: Section 3.10)
    */
    if ( Line.Crc != (Word16) 0 )
        DecStat.Ecount = add( DecStat.Ecount, (Word16) 1 ) ;
    else
        DecStat.Ecount = (Word16) 0 ;

    if ( DecStat.Ecount > (Word16) ErrMaxNum )
        DecStat.Ecount = (Word16) ErrMaxNum ;

    /*
    * Decode the LSP vector for subframe 3.  (Text: Section 3.2)
    */
    Lsp_Inq( LspVect, DecStat.PrevLsp, Line.LspId, Line.Crc ) ;

    /*
    * Interpolate the LSP vectors for subframes 0--2.  Convert the
    * LSP vectors to LPC coefficients.  (Text: Section 3.3)
    */
   Lsp_Int( QntLpc, LspVect, DecStat.PrevLsp ) ;

   /* Copy the LSP vector for the next frame */
   for ( i = 0 ; i < LpcOrder ; i ++ )
      DecStat.PrevLsp[i] = LspVect[i] ;

   /*
    * In case of no erasure, update the interpolation gain memory.
    * Otherwise compute the interpolation gain (Text: Section 3.10)
    */
   if ( DecStat.Ecount == (Word16) 0 ) 
   {
      DecStat.InterGain = add( Line.Sfs[SubFrames-2].Mamp, Line.Sfs[SubFrames-1].Mamp ) ;
      DecStat.InterGain = shr( DecStat.InterGain, (Word16) 1 ) ;
      DecStat.InterGain = FcbkGainTable[DecStat.InterGain] ;
   }
   else
      DecStat.InterGain = mult_r( DecStat.InterGain, (Word16) 0x6000 ) ;


   /*
    * Generate the excitation for the frame
    */
   for ( i = 0 ; i < PitchMax ; i ++ )
      Temp[i] = DecStat.PrevExc[i] ;

   Dpnt = &Temp[PitchMax] ;

   if ( DecStat.Ecount == (Word16) 0 ) 
   {

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

         /* Generate the fixed codebook excitation for a
            subframe. (Text: Section 3.5) */
         Fcbk_Unpk( Dpnt, Line.Sfs[i], Line.Olp[i>>1], (Word16) i ) ;

         /* Generate the adaptive codebook excitation for a
            subframe. (Text: Section 3.4) */
         Decod_Acbk( AcbkCont, &Temp[SubFrLen*i], Line.Olp[i>>1], Line.Sfs[i].AcLg, Line.Sfs[i].AcGn ) ;

     /* Add the adaptive and fixed codebook contributions to
            generate the total excitation. */
         for ( j = 0 ; j < SubFrLen ; j ++ ) 
		 {
            Dpnt[j] = shl( Dpnt[j], (Word16) 1 ) ;
            Dpnt[j] = add( Dpnt[j], AcbkCont[j] ) ;
		 }

         Dpnt += SubFrLen ;
	  }

      /* Save the excitation */
      for ( j = 0 ; j < Frame ; j ++ )
         DataBuff[j] = Temp[PitchMax+j] ;

      /* Normalize the excitation */
      Vec_Norm( Temp, (Word16) (PitchMax+Frame) ) ;

      /* Compute interpolation index. (Text: Section 3.10) */
      DecStat.InterIndx = Comp_Info( Temp, Line.Olp[SubFrames/2-1] ) ;

      /* Compute pitch post filter coefficients.  (Text: Section 3.6) */
      if ( UsePf )
         for ( i = 0 ; i < SubFrames ; i ++ )
            Pf[i] = Comp_Lpf( Temp, Line.Olp[i>>1], (Word16) i ) ;

      /* Reload the original excitation */
      for ( j = 0 ; j < PitchMax ; j ++ )
         Temp[j] = DecStat.PrevExc[j] ;
      for ( j = 0 ; j < Frame ; j ++ )
         Temp[PitchMax+j] = DataBuff[j] ;

      /* Perform pitch post filtering for the frame.  (Text: Section
         3.6) */
      if ( UsePf )
         for ( i = 0 ; i < SubFrames ; i ++ )
            Filt_Lpf( DataBuff, Temp, Pf[i], (Word16) i ) ;	
   }
   else 
   {
      /* If a frame erasure has occurred, regenerate the
         signal for the frame. (Text: Section 3.10) */
      Regen( DataBuff, Temp, DecStat.InterIndx, DecStat.InterGain, DecStat.Ecount, &DecStat.Rseed ) ;
   }

   /* Update the previous excitation for the next frame */
   for ( j = 0 ; j < PitchMax ; j ++ )
      DecStat.PrevExc[j] = Temp[Frame+j] ;


   /*
    * Synthesize the speech for the frame
    */
   Dpnt = DataBuff ;
   for ( i = 0 ; i < SubFrames ; i ++ ) 
   {

      /* Compute the synthesized speech signal for a subframe.
      * (Text: Section 3.7)
      */
      Synt( Dpnt, &QntLpc[i*LpcOrder] ) ;

      if ( UsePf ) 
	  {

         /* Do the formant post filter. (Text: Section 3.8) */
         Senr = Spf( Dpnt, &QntLpc[i*LpcOrder] ) ;

         /* Do the gain scaling unit.  (Text: Section 3.9) */
         Scale( Dpnt, Senr ) ;
	  }

      Dpnt += SubFrLen ;
   }

   return (Flag) True ;
}