cor_h_x2.cpp

实现3GPP的GSM中AMR语音的CODECS。

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/****************************************************************************************
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/cor_h_x2.c

     Date: 11/07/2001

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

 Description: Created a separate file for cor_h_x2 function.

 Description: Fixed typecasting issue with TI C compiler and defined one
              local variable per line. Updated copyright year.

 Description: Added #define for log2(32) = 5.

 Description: Added call to round() and L_shl() functions in the last FOR
              loop to make code bit-exact.

 Description: Added pOverflow as a variable that's passed in for the EPOC
              modifications.

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

 Description: Using intrinsics from fxp_arithmetic.h .

 Description: Replacing fxp_arithmetic.h with basic_op.h.

 Description:

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

/*----------------------------------------------------------------------------
; INCLUDES
----------------------------------------------------------------------------*/
#include "typedef.h"
#include "cnst.h"
#include "cor_h_x.h"
#include "cor_h_x2.h" // BX
#include "basic_op.h"

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


/*----------------------------------------------------------------------------
; DEFINES
; Include all pre-processor statements here. Include conditional
; compile variables also.
----------------------------------------------------------------------------*/
#define LOG2_OF_32  5

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

/*----------------------------------------------------------------------------
; LOCAL STORE/BUFFER/POINTER DEFINITIONS
; Variable declaration - defined here and used outside this module
----------------------------------------------------------------------------*/


/*
------------------------------------------------------------------------------
 FUNCTION NAME: cor_h_x2
------------------------------------------------------------------------------
 INPUT AND OUTPUT DEFINITIONS

 Inputs:
    h = vector containing the impulse response of the weighted synthesis
        filter; vector contents are of type Word16; vector length is
        2 * L_SUBFR
    x = target signal vector; vector contents are of type Word16; vector
        length is L_SUBFR
    dn = vector containing the correlation between the target and the
         impulse response; vector contents are of type Word16; vector
         length is L_CODE
    sf = scaling factor of type Word16 ; 2 when mode is MR122, 1 for all
         other modes
    nb_track = number of ACB tracks (Word16)
    step = step size between pulses in one track (Word16)
    pOverflow = pointer to overflow (Flag)

 Outputs:
    dn contents are the newly calculated correlation values
    pOverflow = 1 if the math functions called by cor_h_x2 result in overflow
    else zero.

 Returns:
    None

 Global Variables Used:
    None

 Local Variables Needed:
    None

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

 This function computes the correlation between the target signal (x) and the
 impulse response (h).

 The correlation is given by: d[n] = sum_{i=n}^{L-1} x[i] h[i-n],
 where: n=0,...,L-1

 d[n] is normalized such that the sum of 5 maxima of d[n] corresponding to
 each position track does not saturate.

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

 None

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

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

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

The original etsi reference code uses a global flag Overflow. However, in the
actual implementation a pointer to a the overflow flag is passed in.

void cor_h_x2 (
    Word16 h[],    // (i): impulse response of weighted synthesis filter
    Word16 x[],    // (i): target
    Word16 dn[],   // (o): correlation between target and h[]
    Word16 sf,     // (i): scaling factor: 2 for 12.2, 1 for others
    Word16 nb_track,// (i): the number of ACB tracks
    Word16 step    // (i): step size from one pulse position to the next
                           in one track
)
{
    Word16 i, j, k;
    Word32 s, y32[L_CODE], max, tot;

    // first keep the result on 32 bits and find absolute maximum

    tot = 5;

    for (k = 0; k < nb_track; k++)
    {
        max = 0;
        for (i = k; i < L_CODE; i += step)
        {
            s = 0;
            for (j = i; j < L_CODE; j++)
                s = L_mac (s, x[j], h[j - i]);

            y32[i] = s;

            s = L_abs (s);
            if (L_sub (s, max) > (Word32) 0L)
                max = s;
        }
        tot = L_add (tot, L_shr (max, 1));
    }

    j = sub (norm_l (tot), sf);

    for (i = 0; i < L_CODE; i++)
    {
        dn[i] = pv_round (L_shl (y32[i], j));
    }
}

------------------------------------------------------------------------------
 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 cor_h_x2(
    Word16 h[],    /* (i): impulse response of weighted synthesis filter */
    Word16 x[],    /* (i): target                                        */
    Word16 dn[],   /* (o): correlation between target and h[]            */
    Word16 sf,     /* (i): scaling factor: 2 for 12.2, 1 for others      */
    Word16 nb_track,/* (i): the number of ACB tracks                     */
    Word16 step,   /* (i): step size from one pulse position to the next
                           in one track                                  */
    Flag *pOverflow
)
{
    register Word16 i;
    register Word16 j;
    register Word16 k;
    Word32 s;
    Word32 y32[L_CODE];
    Word32 max;
    Word32 tot;


    /* first keep the result on 32 bits and find absolute maximum */
    tot = LOG2_OF_32;
    for (k = 0; k < nb_track; k++)
    {
        max = 0;
        for (i = k; i < L_CODE; i += step)
        {
            s = 0;

            for (j = i; j < L_CODE; j++)
            {
                s = amrnb_fxp_mac_16_by_16bb((Word32)x[j], (Word32)h[j-i], s);
            }

            s = s << 1;
            y32[i] = s;
            s = L_abs(s);

            if (s > max)
            {
                max = s;
            }
        }
        tot = (tot + (max >> 1));
    }

    j = sub(norm_l(tot), sf, pOverflow);

    for (i = 0; i < L_CODE; i++)
    {
        dn[i] = pv_round(L_shl(y32[i], j, pOverflow), pOverflow);
    }

    return;
}