dl/sp/src/omxSP_FFTInit_R_F32.c

/*
 *  Copyright (c) 2013 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree. An additional intellectual property rights grant can be found
 *  in the file PATENTS.  All contributing project authors may
 *  be found in the AUTHORS file in the root of the source tree.
 *
 *  This is a modification of omxSP_FFTInit_R_S32.c to support float
 *  instead of S32.
 */

#include "dl/api/armCOMM.h"
#include "dl/api/armOMX.h"
#include "dl/api/omxtypes.h"
#include "dl/sp/api/armSP.h"
#include "dl/sp/api/omxSP.h"

/**
 * Function: omxSP_FFTInit_R_F32
 *
 * Description:
 * Initialize the real forward-FFT specification information struct.
 *
 * Remarks:
 * This function is used to initialize the specification structures
 * for functions <ippsFFTFwd_RToCCS_F32_Sfs> and
 * <ippsFFTInv_CCSToR_F32_Sfs>. Memory for *pFFTSpec must be
 * allocated prior to calling this function. The number of bytes
 * required for *pFFTSpec can be determined using
 * <FFTGetBufSize_R_F32>.
 *
 * Parameters:
 * [in]  order       base-2 logarithm of the desired block length;
 *                         valid in the range [0,12].
 * [out] pFFTFwdSpec pointer to the initialized specification structure.
 *
 * Return Value:
 * Standard omxError result. See enumeration for possible result codes.
 *
 */
OMXResult omxSP_FFTInit_R_F32(OMXFFTSpec_R_F32* pFFTSpec, OMX_INT order) {
  OMX_INT i;
  OMX_INT j;
  OMX_FC32* pTwiddle;
  OMX_FC32* pTwiddle1;
  OMX_FC32* pTwiddle2;
  OMX_FC32* pTwiddle3;
  OMX_FC32* pTwiddle4;
  OMX_F32* pBuf;
  OMX_U16* pBitRev;
  OMX_U32 pTmp;
  OMX_INT Nby2;
  OMX_INT N;
  OMX_INT M;
  OMX_INT diff;
  OMX_INT step;
  OMX_F32 x;
  OMX_F32 y;
  OMX_F32 xNeg;
  ARMsFFTSpec_R_FC32* pFFTStruct = 0;

  pFFTStruct = (ARMsFFTSpec_R_FC32 *) pFFTSpec;

  /* if order zero no init is needed */
  if (order == 0) {
    pFFTStruct->N = 1;
    pFFTStruct->pTwiddle = NULL;
    pFFTStruct->pBuf = (OMX_F32 *)
        (sizeof(ARMsFFTSpec_R_SC32) + (OMX_S8*) pFFTSpec);

    return OMX_Sts_NoErr;
  }

  /* Validate args */
  if (!pFFTSpec || (order < 0) || (order > TWIDDLE_TABLE_ORDER))
    return OMX_Sts_BadArgErr;

  /* Do the initializations */
  Nby2 = 1 << (order - 1);
  N = Nby2 << 1;

  /* optimized implementations don't use bitreversal */
  pBitRev = NULL;

  pTwiddle = (OMX_FC32 *) (sizeof(ARMsFFTSpec_R_SC32) + (OMX_S8*) pFFTSpec);

  /* Align to 32 byte boundary */
  pTmp = ((OMX_U32)pTwiddle) & 31;
  if (pTmp)
    pTwiddle = (OMX_FC32*) ((OMX_S8*)pTwiddle + (32 - pTmp));

  pBuf = (OMX_F32*) (sizeof(OMX_FC32)*(5*N/8) + (OMX_S8*) pTwiddle);

  /* Align to 32 byte boundary */
  pTmp = ((OMX_U32)pBuf)&31;                 /* (OMX_U32)pBuf % 32 */
  if (pTmp)
    pBuf = (OMX_F32*) ((OMX_S8*)pBuf + (32 - pTmp));

  /*
   * Filling Twiddle factors :
   *
   * exp^(-j*2*PI*k/ (N/2) ) ; k=0,1,2,...,3/4(N/2)
   *
   * N/2 point complex FFT is used to compute N point real FFT The
   * original twiddle table "armSP_FFT_F32TwiddleTable" is of size
   * (MaxSize/8 + 1) Rest of the values i.e., upto MaxSize are
   * calculated using the symmetries of sin and cos The max size of
   * the twiddle table needed is 3/4(N/2) for a radix-4 stage
   *
   * W = (-2 * PI) / N
   * N = 1 << order
   * W = -PI >> (order - 1)
   */

  M = Nby2 >> 3;
  diff = TWIDDLE_TABLE_ORDER - (order - 1);
  /* step into the twiddle table for the current order */
  step = 1 << diff;

  x = armSP_FFT_F32TwiddleTable[0];
  y = armSP_FFT_F32TwiddleTable[1];
  xNeg = 1;

  if ((order - 1) >= 3) {
    /* i = 0 case */
    pTwiddle[0].Re = x;
    pTwiddle[0].Im = y;
    pTwiddle[2*M].Re = -y;
    pTwiddle[2*M].Im = xNeg;
    pTwiddle[4*M].Re = xNeg;
    pTwiddle[4*M].Im = y;

    for (i = 1; i <= M; i++) {
      j = i*step;

      x = armSP_FFT_F32TwiddleTable[2*j];
      y = armSP_FFT_F32TwiddleTable[2*j+1];

      pTwiddle[i].Re = x;
      pTwiddle[i].Im = y;
      pTwiddle[2*M-i].Re = -y;
      pTwiddle[2*M-i].Im = -x;
      pTwiddle[2*M+i].Re = y;
      pTwiddle[2*M+i].Im = -x;
      pTwiddle[4*M-i].Re = -x;
      pTwiddle[4*M-i].Im = y;
      pTwiddle[4*M+i].Re = -x;
      pTwiddle[4*M+i].Im = -y;
      pTwiddle[6*M-i].Re = y;
      pTwiddle[6*M-i].Im = x;
    }
  } else if ((order - 1) == 2) {
    pTwiddle[0].Re = x;
    pTwiddle[0].Im = y;
    pTwiddle[1].Re = -y;
    pTwiddle[1].Im = xNeg;
    pTwiddle[2].Re = xNeg;
    pTwiddle[2].Im = y;
  } else if ((order-1) == 1) {
    pTwiddle[0].Re = x;
    pTwiddle[0].Im = y;
  }

  /*
   * Now fill the last N/4 values : exp^(-j*2*PI*k/N) ;
   * k=1,3,5,...,N/2-1 These are used for the final twiddle fix-up for
   * converting complex to real FFT
   */

  M = N >> 3;
  diff = TWIDDLE_TABLE_ORDER - order;
  step = 1 << diff;

  pTwiddle1 = pTwiddle + 3*N/8;
  pTwiddle4 = pTwiddle1 + (N/4 - 1);
  pTwiddle3 = pTwiddle1 + N/8;
  pTwiddle2 = pTwiddle1 + (N/8 - 1);

  x = armSP_FFT_F32TwiddleTable[0];
  y = armSP_FFT_F32TwiddleTable[1];
  xNeg = 1;

  if (order >=3) {
    for (i = 1; i <= M; i += 2) {
      j = i*step;

      x = armSP_FFT_F32TwiddleTable[2*j];
      y = armSP_FFT_F32TwiddleTable[2*j+1];

      pTwiddle1[0].Re = x;
      pTwiddle1[0].Im = y;
      pTwiddle1 += 1;
      pTwiddle2[0].Re = -y;
      pTwiddle2[0].Im = -x;
      pTwiddle2 -= 1;
      pTwiddle3[0].Re = y;
      pTwiddle3[0].Im = -x;
      pTwiddle3 += 1;
      pTwiddle4[0].Re = -x;
      pTwiddle4[0].Im = y;
      pTwiddle4 -= 1;
    }
  } else {
    if (order == 2) {
      pTwiddle1[0].Re = -y;
      pTwiddle1[0].Im = xNeg;
    }
  }


  /* Update the structure */
  pFFTStruct->N = N;
  pFFTStruct->pTwiddle = pTwiddle;
  pFFTStruct->pBitRev = pBitRev;
  pFFTStruct->pBuf = pBuf;

  return OMX_Sts_NoErr;
}