/***************************************************************************

 *

 *  FILE NAME:  decoder.c

 *

 *         Usage : decoder  bitstream_file  synth_file

 *

 *         Format for bitstream_file:

 *           244  words (2-byte) containing 244 bits.

 *               Bit 0 = 0x0000 and Bit 1 = 0x0001

 *

 *         Format for synth_file:

 *           Synthesis is written to a binary file of 16 bits data.

 *

 ***************************************************************************/



#include <string.h>



#include "typedef.h"

#include "basic_op.h"

#include "sig_proc.h"

#include "codec.h"

#include "cnst.h"

#include "d_homing.h"





/* These constants define the number of consecutive parameters

   that function decoder_homing_frame_test() checks */



#define WHOLE_FRAME 57

#define TO_FIRST_SUBFRAME 18





Word16 synth_buf[L_FRAME + M];



/* L_FRAME, M, PRM_SIZE, AZ_SIZE, SERIAL_SIZE: defined in "cnst.h" */



/*-----------------------------------------------------------------*

 *             Global variables                                    *

 *-----------------------------------------------------------------*/



/*-----------------------------------------------------------------*

 *            Main decoder routine                                 *

 *-----------------------------------------------------------------*/



void Decode( Word16 *in, Word32 size, Word32 filter, Word32 mask, Word16 *out )

{

    Word16 *synth;              /* Synthesis                  */

    Word16 parm[PRM_SIZE + 1];  /* Synthesis parameters       */

    Word16 serial[SERIAL_SIZE+1]; /* Serial stream              */

    Word16 Az_dec[AZ_SIZE];     /* Decoded Az for post-filter */

                                /* in 4 subframes, length= 44 */

    Word16 i, frame, temp;



    Word16 TAF, SID_flag;



    Word16 reset_flag;

    static Word16 reset_flag_old = 1;



    /*-----------------------------------------------------------------*

     *           Read passed arguments and open in/out files           *

     *-----------------------------------------------------------------*/



    /*-----------------------------------------------------------------*

     *           Initialization of decoder                             *

     *-----------------------------------------------------------------*/



    synth = synth_buf + M;



    reset_dec (); /* Bring the decoder and receive DTX to the initial state */



    /*-----------------------------------------------------------------*

     *            Loop for each "L_FRAME" speech data                  *

     *-----------------------------------------------------------------*/



    frame = 0;



    while (size > 0)

    {

				serial[0] = 0;

				memcpy( &serial[1], in, SERIAL_SIZE*2 );

				in += SERIAL_SIZE;

				size -= L_FRAME;



        SID_flag = 0;//serial[245];         /* Receive SID flag */

        TAF = 0;//serial[246];              /* Receive TAF flag */



        Bits2prm_12k2 (serial, parm);   /* serial to parameters   */



        if (parm[0] == 0)               /* BFI == 0, perform DHF check */

        {

            if (reset_flag_old == 1)    /* Check for second and further

                                           successive DHF (to first subfr.) */

            {

                reset_flag = decoder_homing_frame_test (&parm[1],

                                                        TO_FIRST_SUBFRAME);

            }

            else

            {

                reset_flag = 0;

            }

        }

        else                          /* BFI==1, bypass DHF check (frame

                                           is taken as not being a DHF) */

        {

            reset_flag = 0;

        }



        if ((reset_flag != 0) && (reset_flag_old != 0))

        {

            /* Force the output to be the encoder homing frame pattern */



            for (i = 0; i < L_FRAME; i++)

            {

                synth[i] = EHF_MASK;

            }

        }

        else

        {

            Decoder_12k2 (parm, synth, Az_dec, TAF, SID_flag);/* Synthesis */



						if (filter)

							Post_Filter (synth, Az_dec);                      /* Post-filter */



            for (i = 0; i < L_FRAME; i++) 

                /* Upscale the 15 bit linear PCM to 16 bits,

                   then truncate to 13 bits */

            {

                temp = shl (synth[i], 1);

								if (mask)

									synth[i] = temp & 0xfff8;

            }



        }                       /* else */



				memcpy( out, synth, L_FRAME*2 );

				out += L_FRAME;



        /* BFI == 0, perform check for first DHF (whole frame) */

        if ((parm[0] == 0) && (reset_flag_old == 0))

        {

            reset_flag = decoder_homing_frame_test (&parm[1], WHOLE_FRAME);

        }



        if (reset_flag != 0)

        {

            /* Bring the decoder and receive DTX to the home state */

            reset_dec ();

        }

        reset_flag_old = reset_flag;



    }                           /* while */

}