ec_gains.cpp

实现3GPP的GSM中AMR语音的CODECS。

        st->gbuf[i - 1] = st->gbuf[i];
    }
    st->gbuf[4] = *gain_code;

    return;
}

------------------------------------------------------------------------------
 RESOURCES USED [optional]

 When the code is written for a specific target processor the
 the resources used should be documented below.

 HEAP MEMORY USED: x bytes

 STACK MEMORY USED: x bytes

 CLOCK CYCLES: (cycle count equation for this function) + (variable
                used to represent cycle count for each subroutine
                called)
     where: (cycle count variable) = cycle count for [subroutine
                                     name]

------------------------------------------------------------------------------
 CAUTION [optional]
 [State any special notes, constraints or cautions for users of this function]

------------------------------------------------------------------------------
*/
void ec_gain_code_update(
    ec_gain_codeState *st,    /* i/o : State struct                     */
    Word16 bfi,               /* i   : flag: frame is bad               */
    Word16 prev_bf,           /* i   : flag: previous frame was bad     */
    Word16 *gain_code,        /* i/o : decoded innovation gain          */
    Flag   *pOverflow
)
{
    Word16 i;

    /* limit gain_code by previous good gain if previous frame was bad */
    if (bfi == 0)
    {
        if (prev_bf != 0)
        {
            if (sub(*gain_code, st->prev_gc, pOverflow) > 0)
            {
                *gain_code = st->prev_gc;
            }
        }
        st->prev_gc = *gain_code;
    }

    /* update EC states: previous gain, gain buffer */
    st->past_gain_code = *gain_code;

    for (i = 1; i < 5; i++)
    {
        st->gbuf[i - 1] = st->gbuf[i];
    }
    st->gbuf[4] = *gain_code;

    return;
}

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

/*
------------------------------------------------------------------------------
 FUNCTION NAME: ec_gain_pitch
------------------------------------------------------------------------------
 INPUT AND OUTPUT DEFINITIONS

 Inputs:
  st = pointer to a pointer to a structure containing code
       state data of stucture type ec_gain_pitchState
  state = state of the state machine of type Word16
  pOverflow = pointer to overflow indicator of type Flag

  Outputs:
  state = pointer to a pointer to a structure containing code
          state data of stucture type ec_gain_pitchState
  gain_pitch = pointer to pitch gain (Q14) of type Word16
  pOverflow = 1 if there is an overflow else it is zero.

 Returns:
    None.

 Global Variables Used:
    None.

 Local Variables Needed:
    None.

------------------------------------------------------------------------------
 FUNCTION DESCRIPTION

 This function conceals the error using code gain implementation in this
 function.

------------------------------------------------------------------------------
 REQUIREMENTS

 None.

------------------------------------------------------------------------------
 REFERENCES

 ec_gain.c, UMTS GSM AMR speech codec, R99 - Version 3.2.0, March 2, 2001

------------------------------------------------------------------------------
 PSEUDO-CODE


    static const Word16 pdown[7] =
    {
        32767, 32112, 32112, 26214,
        9830, 6553, 6553
    };

    Word16 tmp;

    // calculate median of last five gains
    tmp = gmed_n (st->pbuf, 5);

    // new gain = minimum(median, past_gain) * pdown[state]
    if (sub (tmp, st->past_gain_pit) > 0)
    {
        tmp = st->past_gain_pit;
    }
    *gain_pitch = mult (tmp, pdown[state]);


------------------------------------------------------------------------------
 RESOURCES USED [optional]

 When the code is written for a specific target processor the
 the resources used should be documented below.

 HEAP MEMORY USED: x bytes

 STACK MEMORY USED: x bytes

 CLOCK CYCLES: (cycle count equation for this function) + (variable
                used to represent cycle count for each subroutine
                called)
     where: (cycle count variable) = cycle count for [subroutine
                                     name]

------------------------------------------------------------------------------
 CAUTION [optional]
 [State any special notes, constraints or cautions for users of this function]

------------------------------------------------------------------------------
*/
void ec_gain_pitch(
    ec_gain_pitchState *st, /* i/o : state variables                   */
    Word16 state,           /* i   : state of the state machine        */
    Word16 *gain_pitch,     /* o   : pitch gain (Q14)                  */
    Flag   *pOverflow
)
{
    static const Word16 pdown[7] =
    {
        32767, 32112, 32112, 26214,
        9830, 6553, 6553
    };

    Word16 tmp;

    /* calculate median of last five gains */
    tmp = gmed_n(st->pbuf, 5);

    /* new gain = minimum(median, past_gain) * pdown[state] */
    if (sub(tmp, st->past_gain_pit, pOverflow) > 0)
    {
        tmp = st->past_gain_pit;
    }
    *gain_pitch = mult(tmp, pdown[state], pOverflow);
}

/****************************************************************************/
/*
------------------------------------------------------------------------------
 FUNCTION NAME: ec_gain_pitch_reset
------------------------------------------------------------------------------
 INPUT AND OUTPUT DEFINITIONS

 Inputs:
  state = state of the state machine of type Word16
  pOverflow = pointer to overflow indicator of type Flag

  Outputs:
  state = pointer to a pointer to a structure containing code
          state data of stucture type ec_gain_pitchState
  pOverflow = 1 if there is an overflow else it is zero.

 Returns:
    None.

 Global Variables Used:
    None.

 Local Variables Needed:
    None.

------------------------------------------------------------------------------
 FUNCTION DESCRIPTION

 Function:   ec_gain_pitch_reset
 Purpose:    Resets state memory

------------------------------------------------------------------------------
 REQUIREMENTS

 None.

------------------------------------------------------------------------------
 REFERENCES

 ec_gain.c, UMTS GSM AMR speech codec, R99 - Version 3.2.0, March 2, 2001

------------------------------------------------------------------------------
 PSEUDO-CODE

int ec_gain_pitch_reset (ec_gain_pitchState *state)
{
  Word16 i;

  if (state == (ec_gain_pitchState *) NULL){
      // fprintf(stderr, "ec_gain_pitch_reset: invalid parameter\n");
      return -1;
  }

  for(i = 0; i < 5; i++)
      state->pbuf[i] = 1640;
  state->past_gain_pit = 0;
  state->prev_gp = 16384;

  return 0;
}

------------------------------------------------------------------------------
 RESOURCES USED [optional]

 When the code is written for a specific target processor the
 the resources used should be documented below.

 HEAP MEMORY USED: x bytes

 STACK MEMORY USED: x bytes

 CLOCK CYCLES: (cycle count equation for this function) + (variable
                used to represent cycle count for each subroutine
                called)
     where: (cycle count variable) = cycle count for [subroutine
                                     name]

------------------------------------------------------------------------------
 CAUTION [optional]
 [State any special notes, constraints or cautions for users of this function]

------------------------------------------------------------------------------
*/
Word16 ec_gain_pitch_reset(ec_gain_pitchState *state)
{
    Word16 i;

    if (state == (ec_gain_pitchState *) NULL)
    {
        /* fprintf(stderr, "ec_gain_pitch_reset: invalid parameter\n"); */
        return -1;
    }

    for (i = 0; i < 5; i++)
        state->pbuf[i] = 1640;
    state->past_gain_pit = 0;
    state->prev_gp = 16384;

    return 0;
}

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


/*
------------------------------------------------------------------------------
 FUNCTION NAME: ec_gain_pitch_update
------------------------------------------------------------------------------
 INPUT AND OUTPUT DEFINITIONS

 Inputs:
  st = pointer to a pointer to a structure containing code
       state data of stucture type ec_gain_pitchState
  bfi = flag indicating the frame is bad of type Word16
  prev_bf = flag indicating the previous frame was bad of type Word16
  gain_pitch = pointer to pitch gain of type Word16
  pOverflow = pointer to overflow indicator of type Flag

  Outputs:
  state = pointer to a pointer to a structure containing code
          state data of stucture type ec_gain_pitchState
  gain_pitch = pointer to pitch gain of type Word16
  pOverflow = 1 if there is an overflow else it is zero.

 Returns:
    None.

 Global Variables Used:
    None.

 Local Variables Needed:
    None.

------------------------------------------------------------------------------
 FUNCTION DESCRIPTION

  Purpose     : update the pitch gain concealment state;
                limit gain_pitch if the previous frame was bad
                Call this function always after decoding (or concealing)
                the gain

------------------------------------------------------------------------------
 REQUIREMENTS

 None.

------------------------------------------------------------------------------
 REFERENCES

 ec_gain.c, UMTS GSM AMR speech codec, R99 - Version 3.2.0, March 2, 2001

------------------------------------------------------------------------------
 PSEUDO-CODE

    Word16 i;

    if (bfi == 0)
    {
        if (prev_bf != 0)
        {
            if (sub (*gain_pitch, st->prev_gp) > 0)
            {
                *gain_pitch = st->prev_gp;
            }
        }
        st->prev_gp = *gain_pitch;
    }

    st->past_gain_pit = *gain_pitch;

    if (sub (st->past_gain_pit, 16384) > 0)  // if (st->past_gain_pit > 1.0)
    {
        st->past_gain_pit = 16384;
    }
    for (i = 1; i < 5; i++)
    {
        st->pbuf[i - 1] = st->pbuf[i];
    }
    st->pbuf[4] = st->past_gain_pit;


------------------------------------------------------------------------------
 RESOURCES USED [optional]

 When the code is written for a specific target processor the
 the resources used should be documented below.

 HEAP MEMORY USED: x bytes

 STACK MEMORY USED: x bytes

 CLOCK CYCLES: (cycle count equation for this function) + (variable
                used to represent cycle count for each subroutine
                called)
     where: (cycle count variable) = cycle count for [subroutine
                                     name]

------------------------------------------------------------------------------
 CAUTION [optional]
 [State any special notes, constraints or cautions for users of this function]

------------------------------------------------------------------------------
*/
void ec_gain_pitch_update(
    ec_gain_pitchState *st, /* i/o : state variables                   */
    Word16 bfi,             /* i   : flag: frame is bad                */
    Word16 prev_bf,         /* i   : flag: previous frame was bad      */
    Word16 *gain_pitch,     /* i/o : pitch gain                        */
    Flag   *pOverflow
)
{
    Word16 i;

    if (bfi == 0)
    {
        if (prev_bf != 0)
        {
            if (sub(*gain_pitch, st->prev_gp, pOverflow) > 0)
            {
                *gain_pitch = st->prev_gp;
            }
        }
        st->prev_gp = *gain_pitch;
    }

    st->past_gain_pit = *gain_pitch;

    if (sub(st->past_gain_pit, 16384, pOverflow) > 0)
        /* if (st->past_gain_pit > 1.0) */
    {
        st->past_gain_pit = 16384;
    }
    for (i = 1; i < 5; i++)
    {
        st->pbuf[i - 1] = st->pbuf[i];
    }
    st->pbuf[4] = st->past_gain_pit;
}