xref: /aosp_15_r20/external/aac/libFDK/src/fft_rad2.cpp (revision e54365361535b070c2db7374cec45c159c7d0e7a)

/* -----------------------------------------------------------------------------
Software License for The Fraunhofer FDK AAC Codec Library for Android

© Copyright  1995 - 2018 Fraunhofer-Gesellschaft zur Förderung der angewandten
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 1.    INTRODUCTION
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AAC's HE-AAC and HE-AAC v2 versions are regarded as today's most efficient
general perceptual audio codecs. AAC-ELD is considered the best-performing
full-bandwidth communications codec by independent studies and is widely
deployed. AAC has been standardized by ISO and IEC as part of the MPEG
specifications.

Patent licenses for necessary patent claims for the FDK AAC Codec (including
those of Fraunhofer) may be obtained through Via Licensing
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----------------------------------------------------------------------------- */

/******************* Library for basic calculation routines ********************

   Author(s):   M. Lohwasser, M. Gayer

   Description:

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

#include "fft_rad2.h"

#include "scramble.h"

#define __FFT_RAD2_CPP__

#if defined(__arm__)
#include "arm/fft_rad2_arm.cpp"

#elif defined(__GNUC__) && defined(__mips__) && defined(__mips_dsp)
#include "mips/fft_rad2_mips.cpp"

#endif

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

    functionname: dit_fft (analysis)
    description:  dit-tukey-algorithm
                  scrambles data at entry
                  i.e. loop is made with scrambled data
    returns:
    input:
    output:

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

#ifndef FUNCTION_dit_fft

void dit_fft(FIXP_DBL *x, const INT ldn, const FIXP_STP *trigdata,
             const INT trigDataSize) {
  const INT n = 1 << ldn;
  INT trigstep, i, ldm;

  C_ALLOC_ALIGNED_CHECK(x);

  scramble(x, n);
  /*
   * 1+2 stage radix 4
   */

  for (i = 0; i < n * 2; i += 8) {
    FIXP_DBL a00, a10, a20, a30;
    a00 = (x[i + 0] + x[i + 2]) >> 1; /* Re A + Re B */
    a10 = (x[i + 4] + x[i + 6]) >> 1; /* Re C + Re D */
    a20 = (x[i + 1] + x[i + 3]) >> 1; /* Im A + Im B */
    a30 = (x[i + 5] + x[i + 7]) >> 1; /* Im C + Im D */

    x[i + 0] = a00 + a10; /* Re A' = Re A + Re B + Re C + Re D */
    x[i + 4] = a00 - a10; /* Re C' = Re A + Re B - Re C - Re D */
    x[i + 1] = a20 + a30; /* Im A' = Im A + Im B + Im C + Im D */
    x[i + 5] = a20 - a30; /* Im C' = Im A + Im B - Im C - Im D */

    a00 = a00 - x[i + 2]; /* Re A - Re B */
    a10 = a10 - x[i + 6]; /* Re C - Re D */
    a20 = a20 - x[i + 3]; /* Im A - Im B */
    a30 = a30 - x[i + 7]; /* Im C - Im D */

    x[i + 2] = a00 + a30; /* Re B' = Re A - Re B + Im C - Im D */
    x[i + 6] = a00 - a30; /* Re D' = Re A - Re B - Im C + Im D */
    x[i + 3] = a20 - a10; /* Im B' = Im A - Im B - Re C + Re D */
    x[i + 7] = a20 + a10; /* Im D' = Im A - Im B + Re C - Re D */
  }

  for (ldm = 3; ldm <= ldn; ++ldm) {
    INT m = (1 << ldm);
    INT mh = (m >> 1);
    INT j, r;

    trigstep = ((trigDataSize << 2) >> ldm);

    FDK_ASSERT(trigstep > 0);

    /* Do first iteration with c=1.0 and s=0.0 separately to avoid loosing to
       much precision. Beware: The impact on the overal FFT precision is rather
       large. */
    { /* block 1 */

      j = 0;

      for (r = 0; r < n; r += m) {
        INT t1 = (r + j) << 1;
        INT t2 = t1 + (mh << 1);
        FIXP_DBL vr, vi, ur, ui;

        // cplxMultDiv2(&vi, &vr, x[t2+1], x[t2], (FIXP_SGL)1.0, (FIXP_SGL)0.0);
        vi = x[t2 + 1] >> 1;
        vr = x[t2] >> 1;

        ur = x[t1] >> 1;
        ui = x[t1 + 1] >> 1;

        x[t1] = ur + vr;
        x[t1 + 1] = ui + vi;

        x[t2] = ur - vr;
        x[t2 + 1] = ui - vi;

        t1 += mh;
        t2 = t1 + (mh << 1);

        // cplxMultDiv2(&vr, &vi, x[t2+1], x[t2], (FIXP_SGL)1.0, (FIXP_SGL)0.0);
        vr = x[t2 + 1] >> 1;
        vi = x[t2] >> 1;

        ur = x[t1] >> 1;
        ui = x[t1 + 1] >> 1;

        x[t1] = ur + vr;
        x[t1 + 1] = ui - vi;

        x[t2] = ur - vr;
        x[t2 + 1] = ui + vi;
      }

    } /* end of  block 1 */

    for (j = 1; j < mh / 4; ++j) {
      FIXP_STP cs;

      cs = trigdata[j * trigstep];

      for (r = 0; r < n; r += m) {
        INT t1 = (r + j) << 1;
        INT t2 = t1 + (mh << 1);
        FIXP_DBL vr, vi, ur, ui;

        cplxMultDiv2(&vi, &vr, x[t2 + 1], x[t2], cs);

        ur = x[t1] >> 1;
        ui = x[t1 + 1] >> 1;

        x[t1] = ur + vr;
        x[t1 + 1] = ui + vi;

        x[t2] = ur - vr;
        x[t2 + 1] = ui - vi;

        t1 += mh;
        t2 = t1 + (mh << 1);

        cplxMultDiv2(&vr, &vi, x[t2 + 1], x[t2], cs);

        ur = x[t1] >> 1;
        ui = x[t1 + 1] >> 1;

        x[t1] = ur + vr;
        x[t1 + 1] = ui - vi;

        x[t2] = ur - vr;
        x[t2 + 1] = ui + vi;

        /* Same as above but for t1,t2 with j>mh/4 and thus cs swapped */
        t1 = (r + mh / 2 - j) << 1;
        t2 = t1 + (mh << 1);

        cplxMultDiv2(&vi, &vr, x[t2], x[t2 + 1], cs);

        ur = x[t1] >> 1;
        ui = x[t1 + 1] >> 1;

        x[t1] = ur + vr;
        x[t1 + 1] = ui - vi;

        x[t2] = ur - vr;
        x[t2 + 1] = ui + vi;

        t1 += mh;
        t2 = t1 + (mh << 1);

        cplxMultDiv2(&vr, &vi, x[t2], x[t2 + 1], cs);

        ur = x[t1] >> 1;
        ui = x[t1 + 1] >> 1;

        x[t1] = ur - vr;
        x[t1 + 1] = ui - vi;

        x[t2] = ur + vr;
        x[t2 + 1] = ui + vi;
      }
    }

    { /* block 2 */
      j = mh / 4;

      for (r = 0; r < n; r += m) {
        INT t1 = (r + j) << 1;
        INT t2 = t1 + (mh << 1);
        FIXP_DBL vr, vi, ur, ui;

        cplxMultDiv2(&vi, &vr, x[t2 + 1], x[t2], STC(0x5a82799a),
                     STC(0x5a82799a));

        ur = x[t1] >> 1;
        ui = x[t1 + 1] >> 1;

        x[t1] = ur + vr;
        x[t1 + 1] = ui + vi;

        x[t2] = ur - vr;
        x[t2 + 1] = ui - vi;

        t1 += mh;
        t2 = t1 + (mh << 1);

        cplxMultDiv2(&vr, &vi, x[t2 + 1], x[t2], STC(0x5a82799a),
                     STC(0x5a82799a));

        ur = x[t1] >> 1;
        ui = x[t1 + 1] >> 1;

        x[t1] = ur + vr;
        x[t1 + 1] = ui - vi;

        x[t2] = ur - vr;
        x[t2 + 1] = ui + vi;
      }
    } /* end of block 2 */
  }
}

#endif