post_pro.cpp

实现3GPP的GSM中AMR语音的CODECS。

/* ------------------------------------------------------------------
 * Copyright (C) 2008 PacketVideo
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
 * express or implied.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 * -------------------------------------------------------------------
 */
/****************************************************************************************
Portions of this file are derived from the following 3GPP standard:

    3GPP TS 26.073
    ANSI-C code for the Adaptive Multi-Rate (AMR) speech codec
    Available from http://www.3gpp.org

(C) 2004, 3GPP Organizational Partners (ARIB, ATIS, CCSA, ETSI, TTA, TTC)
Permission to distribute, modify and use this file under the standard license
terms listed above has been obtained from the copyright holder.
****************************************************************************************/
/*
------------------------------------------------------------------------------



 Pathname: ./audio/gsm-amr/c/src/post_pro.c
 Functions:
           Post_Process_reset
           Post_Process

     Date: 04/03/2000

------------------------------------------------------------------------------
 REVISION HISTORY

 Description: Updated template used to PV coding template. First attempt at
          optimizing C code.

 Description: Deleted variables listed in the Local Stores Needed/Modified
          sections. Optimized the "else" portion of the first "if"
          statement in Post_Process function.

 Description: Made grouping more explicit in the calculation of
          signal[i] << 1 in the Post_Process function.

 Description: Added setting of Overflow flag in inlined code.

 Description: Synchronized file with UMTS version 3.2.0. Updated coding
              template. Removed unnecessary include files.

 Description: Replaced basic_op.h with the header file of the math functions
              used in the file.

 Description: Made the following changes per comments from Phase 2/3 review:
              1. Updated copyright year.
              2. Fixed typecasting issue with TI C compiler.
              3. Used short-hand notation for math operations, e.g., "+=",
                 in the code.

 Description: Removed the functions post_pro_init and post_pro_exit.
 The post_pro related structure is no longer dynamically allocated.

 Description: Added pOverflow as a passed in variable as per changes needed
              for the EPOC release.

 Description: Optimized file to reduce clock cycle usage. Updated copyright
              year and removed unused files in Include section.

 Description:  Replaced OSCL mem type functions and eliminated include
               files that now are chosen by OSCL definitions

 Description:  Replaced "int" and/or "char" with OSCL defined types.

 Description: Changed round function name to pv_round to avoid conflict with
              round function in C standard library.

 Description:

------------------------------------------------------------------------------
 MODULE DESCRIPTION

 This file contains the function that performs post-processing on the output
 speech. Post-processing include filtering the output speech through a second
 order high pass filter with cutoff frequency of 60 Hz, and up-scaling the
 output speech by a factor of 2. In addition to the post-processing function
 itself, a post-processing initialization function, post-processing reset
 function, and post-processing exit function are also included in this file.

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


/*----------------------------------------------------------------------------
; INCLUDES
----------------------------------------------------------------------------*/
#include "post_pro.h"
#include "typedef.h"
#include "basic_op.h"

/*----------------------------------------------------------------------------
; MACROS
; Define module specific macros here
----------------------------------------------------------------------------*/


/*----------------------------------------------------------------------------
; DEFINES
; Include all pre-processor statements here. Include conditional
; compile variables also.
----------------------------------------------------------------------------*/

/*----------------------------------------------------------------------------
; LOCAL FUNCTION DEFINITIONS
; Function Prototype declaration
----------------------------------------------------------------------------*/

/*----------------------------------------------------------------------------
; LOCAL VARIABLE DEFINITIONS
; Variable declaration - defined here and used outside this module
----------------------------------------------------------------------------*/

/* filter coefficients (fc = 60 Hz) */
static const Word16 b[3] = {7699, -15398, 7699};
static const Word16 a[3] = {8192, 15836, -7667};

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

 Inputs:
    state = pointer to a structure of type Post_ProcessState

 Outputs:
    structure pointed to by state will have all its fields initialized
      to zero

 Returns:
    return_value = 0, if reset was successful; -1, otherwise (int)

 Global Variables Used:
    None

 Local Variables Needed:
    None

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

 This function initializes state memory to zero.

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

 None

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

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

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

int Post_Process_reset (Post_ProcessState *state)
{
  if (state == (Post_ProcessState *) NULL){
      fprint(stderr, "Post_Process_reset: invalid parameter\n");
      return -1;
  }

  state->y2_hi = 0;
  state->y2_lo = 0;
  state->y1_hi = 0;
  state->y1_lo = 0;
  state->x0 = 0;
  state->x1 = 0;

  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 Post_Process_reset(Post_ProcessState *state)
{
    if (state == (Post_ProcessState *) NULL)
    {
        /*  fprint(stderr, "Post_Process_reset: invalid parameter\n");  */
        return(-1);
    }

    state->y2_hi = 0;
    state->y2_lo = 0;
    state->y1_hi = 0;
    state->y1_lo = 0;
    state->x0 = 0;
    state->x1 = 0;

    return(0);
}

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

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

 Inputs:
    st = pointer to a structure of type Post_ProcessState
    signal = buffer containing the input signal (Word16)
    lg = length of the input signal (Word16)
    pOverflow = pointer to overflow indicator of type Flag

 Outputs:
    structure pointed to by st contains new filter input and output values
    signal buffer contains the HP filtered and up-scaled input signal
    pOverflow points to 1 if overflow occurs in the math functions called
              else it points to 0.

 Returns:
    return_value = 0 (int)

 Global Variables Used:
    a = buffer containing filter coefficients
    b = buffer containing filter coefficients

 Local Variables Needed:
    None

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

 This function performs post-processing on the output speech signal. First,
 the output speech goes through a second order high pass filter with a
 cutoff frequency of 60 Hz. Then, the filtered output speech is multiplied
 by a factor of 2. The algorithm implemented follows the following difference
 equation:

 y[i] = b[0]*x[i]*2 + b[1]*x[i-1]*2 + b[2]*x[i-2]*2 + a[1]*y[i-1] + a[2]*y[i-2];

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

 None

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

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

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

int Post_Process (
    Post_ProcessState *st,  //i/o : post process state
    Word16 signal[],        //i/o : signal
    Word16 lg               //i   : length of signal
    )
{
    Word16 i, x2;
    Word32 L_tmp;

    for (i = 0; i < lg; i++)
    {
        x2 = st->x1;
        st->x1 = st->x0;
        st->x0 = signal[i];

        // y[i] = b[0]*x[i]*2 + b[1]*x[i-1]*2 + b140[2]*x[i-2]/2
        //                    + a[1]*y[i-1] + a[2] * y[i-2];

        L_tmp = Mpy_32_16 (st->y1_hi, st->y1_lo, a[1]);
        L_tmp = L_add (L_tmp, Mpy_32_16 (st->y2_hi, st->y2_lo, a[2]));
        L_tmp = L_mac (L_tmp, st->x0, b[0]);
        L_tmp = L_mac (L_tmp, st->x1, b[1]);
        L_tmp = L_mac (L_tmp, x2, b[2]);
        L_tmp = L_shl (L_tmp, 2);

        //Multiplication by two of output speech with saturation.
        signal[i] = pv_round(L_shl(L_tmp, 1));

        st->y2_hi = st->y1_hi;
        st->y2_lo = st->y1_lo;
        L_Extract (L_tmp, &st->y1_hi, &st->y1_lo);
    }

    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]

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

void Post_Process(
    Post_ProcessState *st,  /* i/o : post process state                   */
    Word16 signal[],        /* i/o : signal                               */
    Word16 lg,              /* i   : length of signal                     */
    Flag   *pOverflow
)
{
    Word16 i, x2;
    Word32 L_tmp;

    Word16 *p_signal;
    Word16 c_a1 = a[1];
    Word16 c_a2 = a[2];
    Word16 c_b0 = b[0];
    Word16 c_b1 = b[1];
    Word16 c_b2 = b[2];

    p_signal = &signal[0];

    for (i = 0; i < lg; i++)
    {
        x2 = st->x1;
        st->x1 = st->x0;
        st->x0 = *(p_signal);

        /*  y[i] = b[0]*x[i]*2 + b[1]*x[i-1]*2 + b140[2]*x[i-2]/2  */
        /*                     + a[1]*y[i-1] + a[2] * y[i-2];      */

        L_tmp = ((Word32) st->y1_hi) * c_a1;
        L_tmp += (((Word32) st->y1_lo) * c_a1) >> 15;
        L_tmp += ((Word32) st->y2_hi) * c_a2;
        L_tmp += (((Word32) st->y2_lo) * c_a2) >> 15;
        L_tmp += ((Word32) st->x0) * c_b0;
        L_tmp += ((Word32) st->x1) * c_b1;
        L_tmp += ((Word32) x2) * c_b2;
        L_tmp <<= 3;


        /* Multiplication by two of output speech with saturation. */

        *(p_signal++) = pv_round(L_shl(L_tmp, 1, pOverflow), pOverflow);

        st->y2_hi = st->y1_hi;
        st->y2_lo = st->y1_lo;

        st->y1_hi = (Word16)(L_tmp >> 16);
        st->y1_lo = (Word16)((L_tmp >> 1) - ((Word32) st->y1_hi << 15));

    }

    return;
}