/***************************  Fraunhofer IIS FDK Tools  **********************

                        (C) Copyright Fraunhofer IIS (2001)
                               All Rights Reserved

    Please be advised that this software and/or program delivery is
    Confidential Information of Fraunhofer and subject to and covered by the

    Fraunhofer IIS Software Evaluation Agreement
    between Google Inc. and  Fraunhofer
    effective and in full force since March 1, 2012.

    You may use this software and/or program only under the terms and
    conditions described in the above mentioned Fraunhofer IIS Software
    Evaluation Agreement. Any other and/or further use requires a separate agreement.


   $Id$
   Author(s):   Josef Hoepfl, DSP Solutions
   Description: Fix point FFT

   This software and/or program is protected by copyright law and international
   treaties. Any reproduction or distribution of this software and/or program,
   or any portion of it, may result in severe civil and criminal penalties, and
   will be prosecuted to the maximum extent possible under law.

   History:
   20-APR-2010  A. Tritthart  replaced modulo operations with comparisons in fft15
                to avoid failures with ARM RVCT 4.0 compiler
                Tuned fft15 by 18% (Cortex-A8) to 25% (ARM926) by reprogramming
                with merged loops.

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

#include "fft.h"

#include "fft_rad2.h"
#include "FDK_tools_rom.h"





#define F3C(x) STC(x)

#define     C31       (F3C(0x91261468))      /* FL2FXCONST_DBL(-0.86602540)   */

/* Performs the FFT of length 3 according to the algorithm after winograd.
   No scaling of the input vector because the scaling is already done in the rotation vector. */
static FORCEINLINE void fft3(FIXP_DBL *RESTRICT pDat)
{
  FIXP_DBL r1,r2;
  FIXP_DBL s1,s2;
  /* real part */
  r1      = pDat[2] + pDat[4];
  r2      = fMult((pDat[2] - pDat[4]), C31);
  pDat[0] = pDat[0] + r1;
  r1      = pDat[0] - r1 - (r1>>1);

  /* imaginary part */
  s1      = pDat[3] + pDat[5];
  s2      = fMult((pDat[3] - pDat[5]), C31);
  pDat[1] = pDat[1] + s1;
  s1      = pDat[1] - s1 - (s1>>1);

  /* combination */
  pDat[2] = r1 - s2;
  pDat[4] = r1 + s2;
  pDat[3] = s1 + r2;
  pDat[5] = s1 - r2;
}


//#define F5C(x) ((FIXP_DBL)x)
#define F5C(x) STC(x)

#define     C51       (F5C(0x79bc3854))      /* FL2FXCONST_DBL( 0.95105652)   */
#define     C52       (F5C(0x9d839db0))      /* FL2FXCONST_DBL(-1.53884180/2) */
#define     C53       (F5C(0xd18053ce))      /* FL2FXCONST_DBL(-0.36327126)   */
#define     C54       (F5C(0x478dde64))      /* FL2FXCONST_DBL( 0.55901699)   */
#define     C55       (F5C(0xb0000001))      /* FL2FXCONST_DBL(-1.25/2)       */

/* performs the FFT of length 5 according to the algorithm after winograd */
static FORCEINLINE void fft5(FIXP_DBL *RESTRICT pDat)
{
  FIXP_DBL r1,r2,r3,r4;
  FIXP_DBL s1,s2,s3,s4;
  FIXP_DBL t;

  /* real part */
  r1      = pDat[2] + pDat[8];
  r4      = pDat[2] - pDat[8];
  r3      = pDat[4] + pDat[6];
  r2      = pDat[4] - pDat[6];
  t       = fMult((r1-r3), C54);
  r1      = r1 + r3;
  pDat[0] = pDat[0] + r1;
  /* Bit shift left because of the constant C55 which was scaled with the factor 0.5 because of the representation of
     the values as fracts */
  r1      = pDat[0] + (fMultDiv2(r1, C55) <<(2));
  r3      = r1 - t;
  r1      = r1 + t;
  t       = fMult((r4 + r2), C51);
  /* Bit shift left because of the constant C55 which was scaled with the factor 0.5 because of the representation of
     the values as fracts */
  r4      = t + (fMultDiv2(r4, C52) <<(2));
  r2      = t + fMult(r2, C53);

  /* imaginary part */
  s1      = pDat[3] + pDat[9];
  s4      = pDat[3] - pDat[9];
  s3      = pDat[5] + pDat[7];
  s2      = pDat[5] - pDat[7];
  t       = fMult((s1 - s3), C54);
  s1      = s1 + s3;
  pDat[1] = pDat[1] + s1;
  /* Bit shift left because of the constant C55 which was scaled with the factor 0.5 because of the representation of
     the values as fracts */
  s1      = pDat[1] + (fMultDiv2(s1, C55) <<(2));
  s3      = s1 - t;
  s1      = s1 + t;
  t       = fMult((s4 + s2), C51);
  /* Bit shift left because of the constant C55 which was scaled with the factor 0.5 because of the representation of
     the values as fracts */
  s4      = t + (fMultDiv2(s4, C52) <<(2));
  s2      = t + fMult(s2, C53);

  /* combination */
  pDat[2] = r1 + s2;
  pDat[8] = r1 - s2;
  pDat[4] = r3 - s4;
  pDat[6] = r3 + s4;

  pDat[3] = s1 - r2;
  pDat[9] = s1 + r2;
  pDat[5] = s3 + r4;
  pDat[7] = s3 - r4;
}




#define N3                    3
#define N5                    5
#define N6                    6
#define N15                   15

/* Performs the FFT of length 15. It is split into FFTs of length 3 and length 5. */
static inline void fft15(FIXP_DBL *pInput)
{
#if FORCE_CRITICAL_CODE_FOR_RVCT4
  FIXP_DBL  accu;
  int j;
#endif
  FIXP_DBL  aDst[2*N15];
  FIXP_DBL  aDst1[2*N15];
  int    i,k,l;

  /* Sort input vector for fft's of length 3
  input3(0:2)   = [input(0) input(5) input(10)];
  input3(3:5)   = [input(3) input(8) input(13)];
  input3(6:8)   = [input(6) input(11) input(1)];
  input3(9:11)  = [input(9) input(14) input(4)];
  input3(12:14) = [input(12) input(2) input(7)]; */
#if FORCE_CRITICAL_CODE_FOR_RVCT4
  /* This branch generate failures on RVCT 4.0 with ARM926/ARM1136/ARM1176/C-R4, but not on Cortex-A8 */
  pSrc = pInput;
  pDst = aDst;
  for(i=0,l=0,k=0; i<N5; i++)
  {
    for(j=0; j<N3; j++)
    {
      pDst[k]   = pSrc[l];
      pDst[k+1] = pSrc[l+1];
      k += 2;
      l += 2*N5;
      if (l >= (2*N15))
        l -= (2*N15);
    }
    l += (2*N3);
    if (l >= (2*N15))
      l -= (2*N15);
  }
  /* Perform 5 times the fft of length 3
  output3(0:2)   = fft3(input3(0:2));
  output3(3:5)   = fft3(input3(3:5));
  output3(6:8)   = fft3(input3(6:8));
  output3(9:11)  = fft3(input3(9:11));
  output3(12:14) = fft3(input3(12:14)); */
  pSrc=aDst;
  for(i=0; i<N5; i++)
  {
    fft3(pSrc);
    pSrc += (2*N3);
  }

  /* Scaling of the input vector of the fft5 with the scale factor 0.125 */
  pSrc=aDst;
  for(j=0; j<(2*N3*N5); j++)
  {
    accu = pSrc[j];
    /* 2 bit right shift */
    accu >>= 2;
    pSrc[j] = accu;
  }
#else
  {
    const FIXP_DBL *pSrc = pInput;
    FIXP_DBL *RESTRICT pDst = aDst;
    /* Merge 3 loops into one, skip call of fft3 */
    for(i=0,l=0,k=0; i<N5; i++, k+=6)
    {
      pDst[k+0] = pSrc[l];
      pDst[k+1] = pSrc[l+1];
      l += 2*N5;
      if (l >= (2*N15))
          l -= (2*N15);

      pDst[k+2] = pSrc[l];
      pDst[k+3] = pSrc[l+1];
      l += 2*N5;
      if (l >= (2*N15))
          l -= (2*N15);
      pDst[k+4] = pSrc[l];
      pDst[k+5] = pSrc[l+1];
      l += (2*N5) + (2*N3);
      if (l >= (2*N15))
          l -= (2*N15);

      /* fft3 merged with shift right by 2 loop */
      FIXP_DBL r1,r2,r3;
      FIXP_DBL s1,s2;
      /* real part */
      r1      = pDst[k+2] + pDst[k+4];
      r2      = fMult((pDst[k+2] - pDst[k+4]), C31);
      s1      = pDst[k+0];
      pDst[k+0] = (s1 + r1)>>2;
      r1      = s1 - (r1>>1);

      /* imaginary part */
      s1      = pDst[k+3] + pDst[k+5];
      s2      = fMult((pDst[k+3] - pDst[k+5]), C31);
      r3      = pDst[k+1];
      pDst[k+1] = (r3 + s1)>>2;
      s1      = r3 - (s1>>1);

      /* combination */
      pDst[k+2] = (r1 - s2)>>2;
      pDst[k+4] = (r1 + s2)>>2;
      pDst[k+3] = (s1 + r2)>>2;
      pDst[k+5] = (s1 - r2)>>2;
    }
  }
#endif
  /* Sort input vector for fft's of length 5
  input5(0:4)   = [output3(0) output3(3) output3(6) output3(9) output3(12)];
  input5(5:9)   = [output3(1) output3(4) output3(7) output3(10) output3(13)];
  input5(10:14) = [output3(2) output3(5) output3(8) output3(11) output3(14)]; */
  /* Merge 2 loops into one, brings about 10% */
  {
    const FIXP_DBL *pSrc = aDst;
    FIXP_DBL *RESTRICT pDst = aDst1;
    for(i=0,l=0,k=0; i<N3; i++, k+=10)
    {
      l = 2*i;
      pDst[k+0] = pSrc[l+0];
      pDst[k+1] = pSrc[l+1];
      pDst[k+2] = pSrc[l+0+(2*N3)];
      pDst[k+3] = pSrc[l+1+(2*N3)];
      pDst[k+4] = pSrc[l+0+(4*N3)];
      pDst[k+5] = pSrc[l+1+(4*N3)];
      pDst[k+6] = pSrc[l+0+(6*N3)];
      pDst[k+7] = pSrc[l+1+(6*N3)];
      pDst[k+8] = pSrc[l+0+(8*N3)];
      pDst[k+9] = pSrc[l+1+(8*N3)];
      fft5(&pDst[k]);
    }
  }
  /* Sort output vector of length 15
  output = [out5(0)  out5(6)  out5(12) out5(3)  out5(9)
            out5(10) out5(1)  out5(7)  out5(13) out5(4)
            out5(5)  out5(11) out5(2)  out5(8)  out5(14)]; */
  /* optimize clumsy loop, brings about 5% */
  {
    const FIXP_DBL *pSrc = aDst1;
    FIXP_DBL *RESTRICT pDst = pInput;
    for(i=0,l=0,k=0; i<N3; i++, k+=10)
    {
      pDst[k+0] = pSrc[l];
      pDst[k+1] = pSrc[l+1];
      l += (2*N6);
      if (l >= (2*N15))
          l -= (2*N15);
      pDst[k+2] = pSrc[l];
      pDst[k+3] = pSrc[l+1];
      l += (2*N6);
      if (l >= (2*N15))
          l -= (2*N15);
      pDst[k+4] = pSrc[l];
      pDst[k+5] = pSrc[l+1];
      l += (2*N6);
      if (l >= (2*N15))
          l -= (2*N15);
      pDst[k+6] = pSrc[l];
      pDst[k+7] = pSrc[l+1];
      l += (2*N6);
      if (l >= (2*N15))
          l -= (2*N15);
      pDst[k+8] = pSrc[l];
      pDst[k+9] = pSrc[l+1];
      l += 2;    /* no modulo check needed, it cannot occur */
    }
  }
}

#define W_PiFOURTH STC(0x5a82799a)
#ifndef SUMDIFF_PIFOURTH
#define SUMDIFF_PIFOURTH(diff,sum,a,b) \
  { \
    FIXP_DBL wa, wb;\
    wa = fMultDiv2(a, W_PiFOURTH);\
    wb = fMultDiv2(b, W_PiFOURTH);\
    diff = wb - wa;\
    sum  = wb + wa;\
  }
#endif

/* This version is more overflow save, but less cycle optimal. */
#define SUMDIFF_EIGTH(x, y, ix, iy, vr, vi, ur, ui) \
  vr = (x[ 0 + ix]>>1) + (x[16 + ix]>>1);  /* Re A + Re B */ \
  vi = (x[ 8 + ix]>>1) + (x[24 + ix]>>1);     /* Re C + Re D */ \
  ur = (x[ 1 + ix]>>1) + (x[17 + ix]>>1);  /* Im A + Im B */ \
  ui = (x[ 9 + ix]>>1) + (x[25 + ix]>>1);     /* Im C + Im D */ \
  y[ 0 + iy] = vr + vi;     /* Re A' = ReA + ReB +ReC + ReD */    \
  y[ 4 + iy] = vr - vi;     /* Re C' = -(ReC+ReD) + (ReA+ReB) */  \
  y[ 1 + iy] = ur + ui;     /* Im A' = sum of imag values */      \
  y[ 5 + iy] = ur - ui;     /* Im C' = -Im C -Im D +Im A +Im B */ \
  vr -= x[16 + ix];              /* Re A - Re B */ \
  vi = vi - x[24 + ix];          /* Re C - Re D */ \
  ur -= x[17 + ix];              /* Im A - Im B */ \
  ui = ui - x[25 + ix];          /* Im C - Im D */ \
  y[ 2 + iy] = ui + vr;          /* Re B' = Im C - Im D  + Re A - Re B */ \
  y[ 6 + iy] = vr - ui;          /* Re D' = -Im C + Im D + Re A - Re B */ \
  y[ 3 + iy] = ur - vi;          /* Im B'= -Re C + Re D + Im A - Im B */  \
  y[ 7 + iy] = vi + ur;          /* Im D'= Re C - Re D + Im A - Im B */

static const FIXP_SPK fft16_w16[2] = { {{STC(0x7641af3d), STC(0x30fbc54d)}}, {{ STC(0x30fbc54d), STC(0x7641af3d)}} };

LNK_SECTION_CODE_L1
inline void fft_16(FIXP_DBL *RESTRICT x)
{
  FIXP_DBL vr, vi, ur, ui;
  FIXP_DBL y[32];

  SUMDIFF_EIGTH(x, y, 0,  0, vr, vi, ur, ui);
  SUMDIFF_EIGTH(x, y, 4,  8, vr, vi, ur, ui);
  SUMDIFF_EIGTH(x, y, 2, 16, vr, vi, ur, ui);
  SUMDIFF_EIGTH(x, y, 6, 24, vr, vi, ur, ui);

// xt1 =  0
// xt2 =  8
  vr = y[ 8];
  vi = y[ 9];
  ur = y[ 0]>>1;
  ui = y[ 1]>>1;
  x[ 0] = ur + (vr>>1);
  x[ 1] = ui + (vi>>1);
  x[ 8] = ur - (vr>>1);
  x[ 9] = ui - (vi>>1);

// xt1 =  4
// xt2 = 12
  vr = y[13];
  vi = y[12];
  ur = y[ 4]>>1;
  ui = y[ 5]>>1;
  x[ 4] = ur + (vr>>1);
  x[ 5] = ui - (vi>>1);
  x[12] = ur - (vr>>1);
  x[13] = ui + (vi>>1);

// xt1 = 16
// xt2 = 24
  vr = y[24];
  vi = y[25];
  ur = y[16]>>1;
  ui = y[17]>>1;
  x[16] = ur + (vr>>1);
  x[17] = ui + (vi>>1);
  x[24] = ur - (vr>>1);
  x[25] = ui - (vi>>1);

// xt1 = 20
// xt2 = 28
  vr = y[29];
  vi = y[28];
  ur = y[20]>>1;
  ui = y[21]>>1;
  x[20] = ur + (vr>>1);
  x[21] = ui - (vi>>1);
  x[28] = ur - (vr>>1);
  x[29] = ui + (vi>>1);

  // xt1 =  2
// xt2 = 10
  SUMDIFF_PIFOURTH(vi, vr, y[10], y[11])
  //vr = fMultDiv2((y[11] + y[10]),W_PiFOURTH);
  //vi = fMultDiv2((y[11] - y[10]),W_PiFOURTH);
  ur = y[ 2];
  ui = y[ 3];
  x[ 2] = (ur>>1) + vr;
  x[ 3] = (ui>>1) + vi;
  x[10] = (ur>>1) - vr;
  x[11] = (ui>>1) - vi;

// xt1 =  6
// xt2 = 14
  SUMDIFF_PIFOURTH(vr, vi, y[14], y[15])
  ur = y[ 6];
  ui = y[ 7];
  x[ 6] = (ur>>1) + vr;
  x[ 7] = (ui>>1) - vi;
  x[14] = (ur>>1) - vr;
  x[15] = (ui>>1) + vi;

// xt1 = 18
// xt2 = 26
  SUMDIFF_PIFOURTH(vi, vr, y[26], y[27])
  ur = y[18];
  ui = y[19];
  x[18] = (ur>>1) + vr;
  x[19] = (ui>>1) + vi;
  x[26] = (ur>>1) - vr;
  x[27] = (ui>>1) - vi;

// xt1 = 22
// xt2 = 30
  SUMDIFF_PIFOURTH(vr, vi, y[30], y[31])
  ur = y[22];
  ui = y[23];
  x[22] = (ur>>1) + vr;
  x[23] = (ui>>1) - vi;
  x[30] = (ur>>1) - vr;
  x[31] = (ui>>1) + vi;

// xt1 =  0
// xt2 = 16
  vr = x[16];
  vi = x[17];
  ur = x[ 0]>>1;
  ui = x[ 1]>>1;
  x[ 0] = ur + (vr>>1);
  x[ 1] = ui + (vi>>1);
  x[16] = ur - (vr>>1);
  x[17] = ui - (vi>>1);

// xt1 =  8
// xt2 = 24
  vi = x[24];
  vr = x[25];
  ur = x[ 8]>>1;
  ui = x[ 9]>>1;
  x[ 8] = ur + (vr>>1);
  x[ 9] = ui - (vi>>1);
  x[24] = ur - (vr>>1);
  x[25] = ui + (vi>>1);

// xt1 =  2
// xt2 = 18
  cplxMultDiv2(&vi, &vr, x[19], x[18], fft16_w16[0]);
  ur = x[ 2];
  ui = x[ 3];
  x[ 2] = (ur>>1) + vr;
  x[ 3] = (ui>>1) + vi;
  x[18] = (ur>>1) - vr;
  x[19] = (ui>>1) - vi;

// xt1 = 10
// xt2 = 26
  cplxMultDiv2(&vr, &vi, x[27], x[26], fft16_w16[0]);
  ur = x[10];
  ui = x[11];
  x[10] = (ur>>1) + vr;
  x[11] = (ui>>1) - vi;
  x[26] = (ur>>1) - vr;
  x[27] = (ui>>1) + vi;

// xt1 =  4
// xt2 = 20
  SUMDIFF_PIFOURTH(vi, vr, x[20], x[21])
  ur = x[ 4];
  ui = x[ 5];
  x[ 4] = (ur>>1) + vr;
  x[ 5] = (ui>>1) + vi;
  x[20] = (ur>>1) - vr;
  x[21] = (ui>>1) - vi;

// xt1 = 12
// xt2 = 28
  SUMDIFF_PIFOURTH(vr, vi, x[28], x[29])
  ur = x[12];
  ui = x[13];
  x[12] = (ur>>1) + vr;
  x[13] = (ui>>1) - vi;
  x[28] = (ur>>1) - vr;
  x[29] = (ui>>1) + vi;

// xt1 =  6
// xt2 = 22
  cplxMultDiv2(&vi, &vr, x[23], x[22], fft16_w16[1]);
  ur = x[ 6];
  ui = x[ 7];
  x[ 6] = (ur>>1) + vr;
  x[ 7] = (ui>>1) + vi;
  x[22] = (ur>>1) - vr;
  x[23] = (ui>>1) - vi;

// xt1 = 14
// xt2 = 30
  cplxMultDiv2(&vr, &vi, x[31], x[30], fft16_w16[1]);
  ur = x[14];
  ui = x[15];
  x[14] = (ur>>1) + vr;
  x[15] = (ui>>1) - vi;
  x[30] = (ur>>1) - vr;
  x[31] = (ui>>1) + vi;
}

#ifndef FUNCTION_fft_32
static const FIXP_SPK fft32_w32[6] =
{
  {{ STC(0x7641af3d), STC(0x30fbc54d)}}, {{ STC(0x30fbc54d), STC(0x7641af3d)}}, {{ STC(0x7d8a5f40), STC(0x18f8b83c)}},
  {{ STC(0x6a6d98a4), STC(0x471cece7)}}, {{ STC(0x471cece7), STC(0x6a6d98a4)}}, {{ STC(0x18f8b83c), STC(0x7d8a5f40)}}
};

LNK_SECTION_CODE_L1
inline void fft_32(FIXP_DBL *x)
{

#define W_PiFOURTH STC(0x5a82799a)

  FIXP_DBL vr,vi,ur,ui;
  FIXP_DBL y[64];

  /*
   * 1+2 stage radix 4
   */

/////////////////////////////////////////////////////////////////////////////////////////

  // i = 0
  vr = (x[ 0] + x[32])>>1;  /* Re A + Re B */
  vi = (x[16] + x[48]);     /* Re C + Re D */
  ur = (x[ 1] + x[33])>>1;  /* Im A + Im B */
  ui = (x[17] + x[49]);     /* Im C + Im D */

  y[ 0] = vr + (vi>>1);     /* Re A' = ReA + ReB +ReC + ReD */
  y[ 4] = vr - (vi>>1);     /* Re C' = -(ReC+ReD) + (ReA+ReB) */
  y[ 1] = ur + (ui>>1);     /* Im A' = sum of imag values */
  y[ 5] = ur - (ui>>1);     /* Im C' = -Im C -Im D +Im A +Im B */

  vr -= x[32];              /* Re A - Re B */
  vi = (vi>>1) - x[48];     /* Re C - Re D */
  ur -= x[33];              /* Im A - Im B */
  ui = (ui>>1) - x[49];     /* Im C - Im D */

  y[ 2] = ui + vr;          /* Re B' = Im C - Im D  + Re A - Re B */
  y[ 6] = vr - ui;          /* Re D' = -Im C + Im D + Re A - Re B */
  y[ 3] = ur - vi;          /* Im B'= -Re C + Re D + Im A - Im B */
  y[ 7] = vi + ur;          /* Im D'= Re C - Re D + Im A - Im B */

  //i=8
  vr = (x[ 8] + x[40])>>1;  /* Re A + Re B */
  vi = (x[24] + x[56]);     /* Re C + Re D */
  ur = (x[ 9] + x[41])>>1;  /* Im A + Im B */
  ui = (x[25] + x[57]);     /* Im C + Im D */

  y[ 8] = vr + (vi>>1);     /* Re A' = ReA + ReB +ReC + ReD */
  y[12] = vr - (vi>>1);     /* Re C' = -(ReC+ReD) + (ReA+ReB) */
  y[ 9] = ur + (ui>>1);     /* Im A' = sum of imag values */
  y[13] = ur - (ui>>1);     /* Im C' = -Im C -Im D +Im A +Im B */

  vr -= x[40];              /* Re A - Re B */
  vi = (vi>>1) - x[56];     /* Re C - Re D */
  ur -= x[41];              /* Im A - Im B */
  ui = (ui>>1) - x[57];     /* Im C - Im D */

  y[10] = ui + vr;          /* Re B' = Im C - Im D  + Re A - Re B */
  y[14] = vr - ui;          /* Re D' = -Im C + Im D + Re A - Re B */
  y[11] = ur - vi;          /* Im B'= -Re C + Re D + Im A - Im B */
  y[15] = vi + ur;          /* Im D'= Re C - Re D + Im A - Im B */

  //i=16
  vr = (x[ 4] + x[36])>>1;  /* Re A + Re B */
  vi = (x[20] + x[52]);     /* Re C + Re D */
  ur = (x[ 5] + x[37])>>1;  /* Im A + Im B */
  ui = (x[21] + x[53]);     /* Im C + Im D */

  y[16] = vr + (vi>>1);     /* Re A' = ReA + ReB +ReC + ReD */
  y[20] = vr - (vi>>1);     /* Re C' = -(ReC+ReD) + (ReA+ReB) */
  y[17] = ur + (ui>>1);     /* Im A' = sum of imag values */
  y[21] = ur - (ui>>1);     /* Im C' = -Im C -Im D +Im A +Im B */

  vr -= x[36];              /* Re A - Re B */
  vi = (vi>>1) - x[52];     /* Re C - Re D */
  ur -= x[37];              /* Im A - Im B */
  ui = (ui>>1) - x[53];     /* Im C - Im D */

  y[18] = ui + vr;          /* Re B' = Im C - Im D  + Re A - Re B */
  y[22] = vr - ui;          /* Re D' = -Im C + Im D + Re A - Re B */
  y[19] = ur - vi;          /* Im B'= -Re C + Re D + Im A - Im B */
  y[23] = vi + ur;          /* Im D'= Re C - Re D + Im A - Im B */

  //i=24
  vr = (x[12] + x[44])>>1;  /* Re A + Re B */
  vi = (x[28] + x[60]);     /* Re C + Re D */
  ur = (x[13] + x[45])>>1;  /* Im A + Im B */
  ui = (x[29] + x[61]);     /* Im C + Im D */

  y[24] = vr + (vi>>1);     /* Re A' = ReA + ReB +ReC + ReD */
  y[28] = vr - (vi>>1);     /* Re C' = -(ReC+ReD) + (ReA+ReB) */
  y[25] = ur + (ui>>1);     /* Im A' = sum of imag values */
  y[29] = ur - (ui>>1);     /* Im C' = -Im C -Im D +Im A +Im B */

  vr -= x[44];              /* Re A - Re B */
  vi = (vi>>1) - x[60];     /* Re C - Re D */
  ur -= x[45];              /* Im A - Im B */
  ui = (ui>>1) - x[61];     /* Im C - Im D */

  y[26] = ui + vr;          /* Re B' = Im C - Im D  + Re A - Re B */
  y[30] = vr - ui;          /* Re D' = -Im C + Im D + Re A - Re B */
  y[27] = ur - vi;          /* Im B'= -Re C + Re D + Im A - Im B */
  y[31] = vi + ur;          /* Im D'= Re C - Re D + Im A - Im B */

  // i = 32
  vr = (x[ 2] + x[34])>>1;  /* Re A + Re B */
  vi = (x[18] + x[50]);     /* Re C + Re D */
  ur = (x[ 3] + x[35])>>1;  /* Im A + Im B */
  ui = (x[19] + x[51]);     /* Im C + Im D */

  y[32] = vr + (vi>>1);     /* Re A' = ReA + ReB +ReC + ReD */
  y[36] = vr - (vi>>1);     /* Re C' = -(ReC+ReD) + (ReA+ReB) */
  y[33] = ur + (ui>>1);     /* Im A' = sum of imag values */
  y[37] = ur - (ui>>1);     /* Im C' = -Im C -Im D +Im A +Im B */

  vr -= x[34];              /* Re A - Re B */
  vi = (vi>>1) - x[50];     /* Re C - Re D */
  ur -= x[35];              /* Im A - Im B */
  ui = (ui>>1) - x[51];     /* Im C - Im D */

  y[34] = ui + vr;          /* Re B' = Im C - Im D  + Re A - Re B */
  y[38] = vr - ui;          /* Re D' = -Im C + Im D + Re A - Re B */
  y[35] = ur - vi;          /* Im B'= -Re C + Re D + Im A - Im B */
  y[39] = vi + ur;          /* Im D'= Re C - Re D + Im A - Im B */

  //i=40
  vr = (x[10] + x[42])>>1;  /* Re A + Re B */
  vi = (x[26] + x[58]);     /* Re C + Re D */
  ur = (x[11] + x[43])>>1;  /* Im A + Im B */
  ui = (x[27] + x[59]);     /* Im C + Im D */

  y[40] = vr + (vi>>1);     /* Re A' = ReA + ReB +ReC + ReD */
  y[44] = vr - (vi>>1);     /* Re C' = -(ReC+ReD) + (ReA+ReB) */
  y[41] = ur + (ui>>1);     /* Im A' = sum of imag values */
  y[45] = ur - (ui>>1);     /* Im C' = -Im C -Im D +Im A +Im B */

  vr -= x[42];              /* Re A - Re B */
  vi = (vi>>1) - x[58];     /* Re C - Re D */
  ur -= x[43];              /* Im A - Im B */
  ui = (ui>>1) - x[59];     /* Im C - Im D */

  y[42] = ui + vr;          /* Re B' = Im C - Im D  + Re A - Re B */
  y[46] = vr - ui;          /* Re D' = -Im C + Im D + Re A - Re B */
  y[43] = ur - vi;          /* Im B'= -Re C + Re D + Im A - Im B */
  y[47] = vi + ur;          /* Im D'= Re C - Re D + Im A - Im B */

  //i=48
  vr = (x[ 6] + x[38])>>1;  /* Re A + Re B */
  vi = (x[22] + x[54]);     /* Re C + Re D */
  ur = (x[ 7] + x[39])>>1;  /* Im A + Im B */
  ui = (x[23] + x[55]);     /* Im C + Im D */

  y[48] = vr + (vi>>1);     /* Re A' = ReA + ReB +ReC + ReD */
  y[52] = vr - (vi>>1);     /* Re C' = -(ReC+ReD) + (ReA+ReB) */
  y[49] = ur + (ui>>1);     /* Im A' = sum of imag values */
  y[53] = ur - (ui>>1);     /* Im C' = -Im C -Im D +Im A +Im B */

  vr -= x[38];              /* Re A - Re B */
  vi = (vi>>1) - x[54];     /* Re C - Re D */
  ur -= x[39];              /* Im A - Im B */
  ui = (ui>>1) - x[55];     /* Im C - Im D */

  y[50] = ui + vr;          /* Re B' = Im C - Im D  + Re A - Re B */
  y[54] = vr - ui;          /* Re D' = -Im C + Im D + Re A - Re B */
  y[51] = ur - vi;          /* Im B'= -Re C + Re D + Im A - Im B */
  y[55] = vi + ur;          /* Im D'= Re C - Re D + Im A - Im B */

  //i=56
  vr = (x[14] + x[46])>>1;  /* Re A + Re B */
  vi = (x[30] + x[62]);     /* Re C + Re D */
  ur = (x[15] + x[47])>>1;  /* Im A + Im B */
  ui = (x[31] + x[63]);     /* Im C + Im D */

  y[56] = vr + (vi>>1);     /* Re A' = ReA + ReB +ReC + ReD */
  y[60] = vr - (vi>>1);     /* Re C' = -(ReC+ReD) + (ReA+ReB) */
  y[57] = ur + (ui>>1);     /* Im A' = sum of imag values */
  y[61] = ur - (ui>>1);     /* Im C' = -Im C -Im D +Im A +Im B */

  vr -= x[46];              /* Re A - Re B */
  vi = (vi>>1) - x[62];     /* Re C - Re D */
  ur -= x[47];              /* Im A - Im B */
  ui = (ui>>1) - x[63];     /* Im C - Im D */

  y[58] = ui + vr;          /* Re B' = Im C - Im D  + Re A - Re B */
  y[62] = vr - ui;          /* Re D' = -Im C + Im D + Re A - Re B */
  y[59] = ur - vi;          /* Im B'= -Re C + Re D + Im A - Im B */
  y[63] = vi + ur;          /* Im D'= Re C - Re D + Im A - Im B */


  FIXP_DBL *xt = &x[0];
  FIXP_DBL *yt = &y[0];

  int j = 4;
  do
  {
    vr = yt[8];
    vi = yt[9];
    ur = yt[0]>>1;
    ui = yt[1]>>1;
    xt[ 0] = ur + (vr>>1);
    xt[ 1] = ui + (vi>>1);
    xt[ 8] = ur - (vr>>1);
    xt[ 9] = ui - (vi>>1);

    vr = yt[13];
    vi = yt[12];
    ur = yt[4]>>1;
    ui = yt[5]>>1;
    xt[ 4] = ur + (vr>>1);
    xt[ 5] = ui - (vi>>1);
    xt[12] = ur - (vr>>1);
    xt[13] = ui + (vi>>1);

    SUMDIFF_PIFOURTH(vi, vr, yt[10], yt[11])
    ur = yt[2];
    ui = yt[3];
    xt[ 2] = (ur>>1) + vr;
    xt[ 3] = (ui>>1) + vi;
    xt[10] = (ur>>1) - vr;
    xt[11] = (ui>>1) - vi;

    SUMDIFF_PIFOURTH(vr, vi, yt[14], yt[15])
    ur = yt[6];
    ui = yt[7];

    xt[ 6] = (ur>>1) + vr;
    xt[ 7] = (ui>>1) - vi;
    xt[14] = (ur>>1) - vr;
    xt[15] = (ui>>1) + vi;
    xt += 16;
    yt += 16;
  } while (--j != 0);

  vr = x[16];
  vi = x[17];
  ur = x[ 0]>>1;
  ui = x[ 1]>>1;
  x[ 0] = ur + (vr>>1);
  x[ 1] = ui + (vi>>1);
  x[16] = ur - (vr>>1);
  x[17] = ui - (vi>>1);

  vi = x[24];
  vr = x[25];
  ur = x[ 8]>>1;
  ui = x[ 9]>>1;
  x[ 8] = ur + (vr>>1);
  x[ 9] = ui - (vi>>1);
  x[24] = ur - (vr>>1);
  x[25] = ui + (vi>>1);

  vr = x[48];
  vi = x[49];
  ur = x[32]>>1;
  ui = x[33]>>1;
  x[32] = ur + (vr>>1);
  x[33] = ui + (vi>>1);
  x[48] = ur - (vr>>1);
  x[49] = ui - (vi>>1);

  vi = x[56];
  vr = x[57];
  ur = x[40]>>1;
  ui = x[41]>>1;
  x[40] = ur + (vr>>1);
  x[41] = ui - (vi>>1);
  x[56] = ur - (vr>>1);
  x[57] = ui + (vi>>1);

  cplxMultDiv2(&vi, &vr, x[19], x[18], fft32_w32[0]);
  ur = x[ 2];
  ui = x[ 3];
  x[ 2] = (ur>>1) + vr;
  x[ 3] = (ui>>1) + vi;
  x[18] = (ur>>1) - vr;
  x[19] = (ui>>1) - vi;

  cplxMultDiv2(&vr, &vi, x[27], x[26], fft32_w32[0]);
  ur = x[10];
  ui = x[11];
  x[10] = (ur>>1) + vr;
  x[11] = (ui>>1) - vi;
  x[26] = (ur>>1) - vr;
  x[27] = (ui>>1) + vi;

  cplxMultDiv2(&vi, &vr, x[51], x[50], fft32_w32[0]);
  ur = x[34];
  ui = x[35];
  x[34] = (ur>>1) + vr;
  x[35] = (ui>>1) + vi;
  x[50] = (ur>>1) - vr;
  x[51] = (ui>>1) - vi;

  cplxMultDiv2(&vr, &vi, x[59], x[58], fft32_w32[0]);
  ur = x[42];
  ui = x[43];
  x[42] = (ur>>1) + vr;
  x[43] = (ui>>1) - vi;
  x[58] = (ur>>1) - vr;
  x[59] = (ui>>1) + vi;

  SUMDIFF_PIFOURTH(vi, vr, x[20], x[21])
  ur = x[ 4];
  ui = x[ 5];
  x[ 4] = (ur>>1) + vr;
  x[ 5] = (ui>>1) + vi;
  x[20] = (ur>>1) - vr;
  x[21] = (ui>>1) - vi;

  SUMDIFF_PIFOURTH(vr, vi, x[28], x[29])
  ur = x[12];
  ui = x[13];
  x[12] = (ur>>1) + vr;
  x[13] = (ui>>1) - vi;
  x[28] = (ur>>1) - vr;
  x[29] = (ui>>1) + vi;

  SUMDIFF_PIFOURTH(vi, vr, x[52], x[53])
  ur = x[36];
  ui = x[37];
  x[36] = (ur>>1) + vr;
  x[37] = (ui>>1) + vi;
  x[52] = (ur>>1) - vr;
  x[53] = (ui>>1) - vi;

  SUMDIFF_PIFOURTH(vr, vi, x[60], x[61])
  ur = x[44];
  ui = x[45];
  x[44] = (ur>>1) + vr;
  x[45] = (ui>>1) - vi;
  x[60] = (ur>>1) - vr;
  x[61] = (ui>>1) + vi;


  cplxMultDiv2(&vi, &vr, x[23], x[22], fft32_w32[1]);
  ur = x[ 6];
  ui = x[ 7];
  x[ 6] = (ur>>1) + vr;
  x[ 7] = (ui>>1) + vi;
  x[22] = (ur>>1) - vr;
  x[23] = (ui>>1) - vi;

  cplxMultDiv2(&vr, &vi, x[31], x[30], fft32_w32[1]);
  ur = x[14];
  ui = x[15];
  x[14] = (ur>>1) + vr;
  x[15] = (ui>>1) - vi;
  x[30] = (ur>>1) - vr;
  x[31] = (ui>>1) + vi;

  cplxMultDiv2(&vi, &vr, x[55], x[54], fft32_w32[1]);
  ur = x[38];
  ui = x[39];
  x[38] = (ur>>1) + vr;
  x[39] = (ui>>1) + vi;
  x[54] = (ur>>1) - vr;
  x[55] = (ui>>1) - vi;

  cplxMultDiv2(&vr, &vi, x[63], x[62], fft32_w32[1]);
  ur = x[46];
  ui = x[47];

  x[46] = (ur>>1) + vr;
  x[47] = (ui>>1) - vi;
  x[62] = (ur>>1) - vr;
  x[63] = (ui>>1) + vi;

  vr = x[32];
  vi = x[33];
  ur = x[ 0]>>1;
  ui = x[ 1]>>1;
  x[ 0] = ur + (vr>>1);
  x[ 1] = ui + (vi>>1);
  x[32] = ur - (vr>>1);
  x[33] = ui - (vi>>1);

  vi = x[48];
  vr = x[49];
  ur = x[16]>>1;
  ui = x[17]>>1;
  x[16] = ur + (vr>>1);
  x[17] = ui - (vi>>1);
  x[48] = ur - (vr>>1);
  x[49] = ui + (vi>>1);

  cplxMultDiv2(&vi, &vr, x[35], x[34], fft32_w32[2]);
  ur = x[ 2];
  ui = x[ 3];
  x[ 2] = (ur>>1) + vr;
  x[ 3] = (ui>>1) + vi;
  x[34] = (ur>>1) - vr;
  x[35] = (ui>>1) - vi;

  cplxMultDiv2(&vr, &vi, x[51], x[50], fft32_w32[2]);
  ur = x[18];
  ui = x[19];
  x[18] = (ur>>1) + vr;
  x[19] = (ui>>1) - vi;
  x[50] = (ur>>1) - vr;
  x[51] = (ui>>1) + vi;

  cplxMultDiv2(&vi, &vr, x[37], x[36], fft32_w32[0]);
  ur = x[ 4];
  ui = x[ 5];
  x[ 4] = (ur>>1) + vr;
  x[ 5] = (ui>>1) + vi;
  x[36] = (ur>>1) - vr;
  x[37] = (ui>>1) - vi;

  cplxMultDiv2(&vr, &vi, x[53], x[52], fft32_w32[0]);
  ur = x[20];
  ui = x[21];
  x[20] = (ur>>1) + vr;
  x[21] = (ui>>1) - vi;
  x[52] = (ur>>1) - vr;
  x[53] = (ui>>1) + vi;

  cplxMultDiv2(&vi, &vr, x[39], x[38], fft32_w32[3]);
  ur = x[ 6];
  ui = x[ 7];
  x[ 6] = (ur>>1) + vr;
  x[ 7] = (ui>>1) + vi;
  x[38] = (ur>>1) - vr;
  x[39] = (ui>>1) - vi;

  cplxMultDiv2(&vr, &vi, x[55], x[54], fft32_w32[3]);
  ur = x[22];
  ui = x[23];
  x[22] = (ur>>1) + vr;
  x[23] = (ui>>1) - vi;
  x[54] = (ur>>1) - vr;
  x[55] = (ui>>1) + vi;

  SUMDIFF_PIFOURTH(vi, vr, x[40], x[41])
  ur = x[ 8];
  ui = x[ 9];
  x[ 8] = (ur>>1) + vr;
  x[ 9] = (ui>>1) + vi;
  x[40] = (ur>>1) - vr;
  x[41] = (ui>>1) - vi;

  SUMDIFF_PIFOURTH(vr, vi, x[56], x[57])
  ur = x[24];
  ui = x[25];
  x[24] = (ur>>1) + vr;
  x[25] = (ui>>1) - vi;
  x[56] = (ur>>1) - vr;
  x[57] = (ui>>1) + vi;

  cplxMultDiv2(&vi, &vr, x[43], x[42], fft32_w32[4]);
  ur = x[10];
  ui = x[11];

  x[10] = (ur>>1) + vr;
  x[11] = (ui>>1) + vi;
  x[42] = (ur>>1) - vr;
  x[43] = (ui>>1) - vi;

  cplxMultDiv2(&vr, &vi, x[59], x[58], fft32_w32[4]);
  ur = x[26];
  ui = x[27];
  x[26] = (ur>>1) + vr;
  x[27] = (ui>>1) - vi;
  x[58] = (ur>>1) - vr;
  x[59] = (ui>>1) + vi;

  cplxMultDiv2(&vi, &vr, x[45], x[44], fft32_w32[1]);
  ur = x[12];
  ui = x[13];
  x[12] = (ur>>1) + vr;
  x[13] = (ui>>1) + vi;
  x[44] = (ur>>1) - vr;
  x[45] = (ui>>1) - vi;

  cplxMultDiv2(&vr, &vi, x[61], x[60], fft32_w32[1]);
  ur = x[28];
  ui = x[29];
  x[28] = (ur>>1) + vr;
  x[29] = (ui>>1) - vi;
  x[60] = (ur>>1) - vr;
  x[61] = (ui>>1) + vi;

  cplxMultDiv2(&vi, &vr, x[47], x[46], fft32_w32[5]);
  ur = x[14];
  ui = x[15];
  x[14] = (ur>>1) + vr;
  x[15] = (ui>>1) + vi;
  x[46] = (ur>>1) - vr;
  x[47] = (ui>>1) - vi;

  cplxMultDiv2(&vr, &vi, x[63], x[62], fft32_w32[5]);
  ur = x[30];
  ui = x[31];
  x[30] = (ur>>1) + vr;
  x[31] = (ui>>1) - vi;
  x[62] = (ur>>1) - vr;
  x[63] = (ui>>1) + vi;
}
#endif /* #ifndef FUNCTION_fft_32 */


/**
 * \brief Apply rotation vectors to a data buffer.
 * \param cl length of each row of input data.
 * \param l total length of input data.
 * \param pVecRe real part of rotation ceofficient vector.
 * \param pVecIm imaginary part of rotation ceofficient vector.
 */
static inline void fft_apply_rot_vector(FIXP_DBL *RESTRICT pData, const int cl, const int l, const FIXP_STB *pVecRe, const FIXP_STB *pVecIm)
{
  FIXP_DBL re, im;
  FIXP_STB vre, vim;

  int i, c;

  for(i=0; i<cl; i++) {
    re  = pData[2*i];
    im  = pData[2*i+1];

    pData[2*i]   = re>>2; /* * 0.25 */
    pData[2*i+1] = im>>2; /* * 0.25 */
  }
  for(; i<l; i+=cl)
  {
    re  = pData[2*i];
    im  = pData[2*i+1];

    pData[2*i]   = re>>2; /* * 0.25 */
    pData[2*i+1] = im>>2; /* * 0.25 */

    for (c=i+1; c<i+cl; c++)
    {
      re  = pData[2*c]>>1;
      im  = pData[2*c+1]>>1;
      vre = *pVecRe++;
      vim = *pVecIm++;

      cplxMultDiv2(&pData[2*c+1], &pData[2*c], im, re, vre, vim);
    }
  }
}

#define FFT_TWO_STAGE_MACRO_ENABLE


#ifdef FFT_TWO_STAGE_MACRO_ENABLE

#define fftN2(pInput, length, dim1, dim2, fft_func1, fft_func2, RotVectorReal, RotVectorImag) \
{ \
  int       i, j; \
 \
  C_ALLOC_SCRATCH_START(aDst, FIXP_DBL, length*2); \
  C_ALLOC_SCRATCH_START(aDst2, FIXP_DBL, dim2*2); \
 \
  FDK_ASSERT(length == dim1*dim2); \
 \
  /* Perform dim2 times the fft of length dim1. The input samples are at the address of pSrc and the \
  output samples are at the address of pDst. The input vector for the fft of length dim1 is built \
  of the interleaved samples in pSrc, the output samples are stored consecutively. \
  */ \
  { \
    const FIXP_DBL* pSrc = pInput; \
    FIXP_DBL  *RESTRICT pDst = aDst; \
    \
    for(i=0; i<dim2; i++) \
    { \
      for(j=0; j<dim1; j++) \
      { \
        pDst[2*j]   = pSrc[2*j*dim2]; \
        pDst[2*j+1] = pSrc[2*j*dim2+1]; \
      } \
      \
      fft_func1(pDst); \
      pSrc += 2; \
      pDst = pDst + 2*dim1; \
    } \
  } \
  \
  /* Perform the modulation of the output of the fft of length dim1 */ \
  fft_apply_rot_vector(aDst, dim1, length, RotVectorReal, RotVectorImag); \
  \
  /* Perform dim1 times the fft of length dim2. The input samples are at the address of aDst and the \
  output samples are at the address of pInput. The input vector for the fft of length dim2 is built \
  of the interleaved samples in aDst, the output samples are stored consecutively at the address \
  of pInput. \
  */ \
  { \
    const FIXP_DBL* pSrc       = aDst; \
    FIXP_DBL *RESTRICT pDst    = aDst2; \
    FIXP_DBL *RESTRICT pDstOut = pInput; \
    \
    for(i=0; i<dim1; i++) \
    { \
      for(j=0; j<dim2; j++) \
      { \
        pDst[2*j]   = pSrc[2*j*dim1]; \
        pDst[2*j+1] = pSrc[2*j*dim1+1]; \
      } \
      \
      fft_func2(pDst); \
      \
      for(j=0; j<dim2; j++) \
      { \
        pDstOut[2*j*dim1]   = pDst[2*j]; \
        pDstOut[2*j*dim1+1] = pDst[2*j+1]; \
      } \
      pSrc += 2; \
      pDstOut += 2; \
    } \
  } \
  \
  C_ALLOC_SCRATCH_END(aDst2, FIXP_DBL, dim2*2); \
  C_ALLOC_SCRATCH_END(aDst, FIXP_DBL, length*2); \
} \

#else /* FFT_TWO_STAGE_MACRO_ENABLE */

/* select either switch case of function pointer. */
//#define FFT_TWO_STAGE_SWITCH_CASE

static inline void fftN2(
        FIXP_DBL *pInput,
        const int length,
        const int dim1,
        const int dim2,
        void (* const fft1)(FIXP_DBL *),
        void (* const fft2)(FIXP_DBL *),
        const FIXP_STB *RotVectorReal,
        const FIXP_STB *RotVectorImag
        )
{
  /* The real part of the input samples are at the addresses with even indices and the imaginary
  part of the input samples are at the addresses with odd indices. The output samples are stored
  at the address of pInput
  */
  FIXP_DBL  *pSrc, *pDst, *pDstOut;
  int       i, j;

  C_ALLOC_SCRATCH_START(aDst, FIXP_DBL, length*2);
  C_ALLOC_SCRATCH_START(aDst2, FIXP_DBL, dim2*2);
     
  FDK_ASSERT(length == dim1*dim2);

  /* Perform dim2 times the fft of length dim1. The input samples are at the address of pSrc and the
  output samples are at the address of pDst. The input vector for the fft of length dim1 is built
  of the interleaved samples in pSrc, the output samples are stored consecutively.
  */
  pSrc = pInput;
  pDst = aDst;
  for(i=0; i<length/dim1; i++)
  {
    for(j=0; j<length/dim2; j++)
    {
      pDst[2*j]   = pSrc[2*j*dim2];
      pDst[2*j+1] = pSrc[2*j*dim2+1];
    }

    /* fft of size dim1 */
#ifndef FFT_TWO_STAGE_SWITCH_CASE
    fft1(pDst);
#else
    switch (dim1) {
      case 3: fft3(pDst); break;
      case 4: fft_4(pDst); break;
      case 5: fft5(pDst); break;
      case 8: fft_8(pDst); break;
      case 15: fft15(pDst); break;
      case 16: fft_16(pDst); break;
      case 32: fft_32(pDst); break;
      /*case 64: fft_64(pDst); break;*/
      case 128: fft_128(pDst); break;
    }
#endif
    pSrc += 2;
    pDst = pDst + 2*length/dim2;
  }

  /* Perform the modulation of the output of the fft of length dim1 */
  pSrc=aDst;
  fft_apply_rot_vector(pSrc, length/dim2, length, RotVectorReal, RotVectorImag);

  /* Perform dim1 times the fft of length dim2. The input samples are at the address of aDst and the
  output samples are at the address of pInput. The input vector for the fft of length dim2 is built
  of the interleaved samples in aDst, the output samples are stored consecutively at the address
  of pInput.
  */
  pSrc    = aDst;
  pDst    = aDst2;
  pDstOut = pInput;
  for(i=0; i<length/dim2; i++)
  {
    for(j=0; j<length/dim1; j++)
    {
      pDst[2*j]   = pSrc[2*j*dim1];
      pDst[2*j+1] = pSrc[2*j*dim1+1];
    }

#ifndef FFT_TWO_STAGE_SWITCH_CASE
    fft2(pDst);
#else
    switch (dim2) {
      case 3: fft3(pDst); break;
      case 4: fft_4(pDst); break;
      case 5: fft5(pDst); break;
      case 8: fft_8(pDst); break;
      case 15: fft15(pDst); break;
      case 16: fft_16(pDst); break;
      case 32: fft_32(pDst); break;
      /*case 64: fft_64(pDst); break;*/
      case 128: fft_128(pDst); break;
    }
#endif

    for(j=0; j<length/dim1; j++)
    {
      pDstOut[2*j*dim1]   = pDst[2*j];
      pDstOut[2*j*dim1+1] = pDst[2*j+1];
    }
    pSrc += 2;
    pDstOut += 2;
  }

  C_ALLOC_SCRATCH_END(aDst2, FIXP_DBL, dim2*2);
  C_ALLOC_SCRATCH_END(aDst, FIXP_DBL, length*2);
}

#endif /* FFT_TWO_STAGE_MACRO_ENABLE */












#define SCALEFACTOR60         5
/**
The function performs the fft of length 60. It is splittet into fft's of length 4 and fft's of
length 15. Between the fft's a modolation is calculated.
*/
static inline void fft60(FIXP_DBL *pInput, INT *pScalefactor)
{
  fftN2(
          pInput, 60, 4, 15, 
          fft_4, fft15,
          RotVectorReal60, RotVectorImag60
          );
  *pScalefactor += SCALEFACTOR60;
}



/* Fallback implementation in case of no better implementation available. */

#define SCALEFACTOR240        7

/**
The function performs the fft of length 240. It is splittet into fft's of length 16 and fft's of
length 15. Between the fft's a modulation is calculated.
*/
static inline void fft240(FIXP_DBL *pInput, INT *pScalefactor)
{
  fftN2(
          pInput, 240, 16, 15, 
          fft_16, fft15,
          RotVectorReal240, RotVectorImag240
          );
  *pScalefactor += SCALEFACTOR240;
}


#define SCALEFACTOR480        8
#define N32                   32
#define TABLE_SIZE_16        (32/2)

/**
The function performs the fft of length 480. It is splittet into fft's of length 32 and fft's of
length 15. Between the fft's a modulation is calculated.
*/
static inline void fft480(FIXP_DBL *pInput, INT *pScalefactor)
{
  fftN2(
          pInput, 480, 32, 15, 
          fft_32, fft15,
          RotVectorReal480, RotVectorImag480
          );
  *pScalefactor += SCALEFACTOR480;
}

void fft(int length, FIXP_DBL *pInput, INT *pScalefactor)
{
  if (length == 32)
  {
      fft_32(pInput);
      *pScalefactor += SCALEFACTOR32;
  }
  else
  {
  
  switch (length) {
    case 16:
      fft_16(pInput);
      *pScalefactor += SCALEFACTOR16;
      break;
    case 8:
      fft_8(pInput);
      *pScalefactor += SCALEFACTOR8;
      break;
    case 3:
      fft3(pInput);
      break;
    case 4:
      fft_4(pInput);
      *pScalefactor += SCALEFACTOR4;
      break;
    case 5:
      fft5(pInput);
      break;
    case 15:
      fft15(pInput);
      *pScalefactor += 2;
      break;
    case 60:
      fft60(pInput, pScalefactor);
      break;
    case 64:
      dit_fft(pInput, 6, SineTable512, 512);
      *pScalefactor += SCALEFACTOR64;
      break;
    case 240:
      fft240(pInput, pScalefactor);
      break;
    case 256:
      dit_fft(pInput, 8, SineTable512, 512);
      *pScalefactor += SCALEFACTOR256;
      break;
    case 480:
      fft480(pInput, pScalefactor);
      break;
    case 512:
      dit_fft(pInput, 9, SineTable512, 512);
      *pScalefactor += SCALEFACTOR512;
      break;
    default:
      FDK_ASSERT(0); /* FFT length not supported! */
      break;
  }
  }
}


void ifft(int length, FIXP_DBL *pInput, INT *scalefactor)
{
  switch (length) {
    default:
      FDK_ASSERT(0); /* IFFT length not supported! */
      break;
  }
}