/*
  * MDCT/IMDCT transforms

  * Copyright (c) 2002 Fabrice Bellard

  *

  * This file is part of FFmpeg.
  *
  * FFmpeg is free software; you can redistribute it and/or

  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either

  * version 2.1 of the License, or (at your option) any later version.

  *

  * FFmpeg is distributed in the hope that it will be useful,

  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public

  * License along with FFmpeg; if not, write to the Free Software

  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

  */

 #include <stdlib.h>
 #include <string.h>
 #include "libavutil/common.h"

 #include "libavutil/mathematics.h"
 #include "fft.h"

 #include "fft-internal.h"

 /**

  * @file

  * MDCT/IMDCT transforms.
  */
 

 #if CONFIG_FFT_FLOAT
 #   define RSCALE(x) (x)
 #else
 #   define RSCALE(x) ((x) >> 1)
 #endif
 

 /**
  * init MDCT or IMDCT computation.

  */

 av_cold int ff_mdct_init(FFTContext *s, int nbits, int inverse, double scale)

 {
     int n, n4, i;

     double alpha, theta;

     int tstep;

 
     memset(s, 0, sizeof(*s));
     n = 1 << nbits;

     s->mdct_bits = nbits;
     s->mdct_size = n;

     n4 = n >> 2;

     s->mdct_permutation = FF_MDCT_PERM_NONE;

 
     if (ff_fft_init(s, s->mdct_bits - 2, inverse) < 0)
         goto fail;
 
     s->tcos = av_malloc(n/2 * sizeof(FFTSample));

     if (!s->tcos)
         goto fail;

     switch (s->mdct_permutation) {

     case FF_MDCT_PERM_NONE:
         s->tsin = s->tcos + n4;
         tstep = 1;
         break;
     case FF_MDCT_PERM_INTERLEAVE:
         s->tsin = s->tcos + 1;
         tstep = 2;
         break;
     default:

         goto fail;

     }

     theta = 1.0 / 8.0 + (scale < 0 ? n4 : 0);
     scale = sqrt(fabs(scale));

     for(i=0;i<n4;i++) {

         alpha = 2 * M_PI * (i + theta) / n;

         s->tcos[i*tstep] = FIX15(-cos(alpha) * scale);
         s->tsin[i*tstep] = FIX15(-sin(alpha) * scale);

     }
     return 0;
  fail:

     ff_mdct_end(s);

     return -1;
 }
 

 /**
  * Compute the middle half of the inverse MDCT of size N = 2^nbits,
  * thus excluding the parts that can be derived by symmetry
  * @param output N/2 samples
  * @param input N/2 samples
  */

 void ff_imdct_half_c(FFTContext *s, FFTSample *output, const FFTSample *input)

 {

     int k, n8, n4, n2, n, j;

     const uint16_t *revtab = s->revtab;

     const FFTSample *tcos = s->tcos;
     const FFTSample *tsin = s->tsin;
     const FFTSample *in1, *in2;

     FFTComplex *z = (FFTComplex *)output;

     n = 1 << s->mdct_bits;

     n2 = n >> 1;
     n4 = n >> 2;

     n8 = n >> 3;

 
     /* pre rotation */
     in1 = input;
     in2 = input + n2 - 1;
     for(k = 0; k < n4; k++) {
         j=revtab[k];
         CMUL(z[j].re, z[j].im, *in2, *in1, tcos[k], tsin[k]);
         in1 += 2;
         in2 -= 2;
     }

     s->fft_calc(s, z);

 
     /* post rotation + reordering */

     for(k = 0; k < n8; k++) {
         FFTSample r0, i0, r1, i1;
         CMUL(r0, i1, z[n8-k-1].im, z[n8-k-1].re, tsin[n8-k-1], tcos[n8-k-1]);
         CMUL(r1, i0, z[n8+k  ].im, z[n8+k  ].re, tsin[n8+k  ], tcos[n8+k  ]);
         z[n8-k-1].re = r0;
         z[n8-k-1].im = i0;
         z[n8+k  ].re = r1;
         z[n8+k  ].im = i1;

     }

 }
 
 /**
  * Compute inverse MDCT of size N = 2^nbits
  * @param output N samples
  * @param input N/2 samples
  */

 void ff_imdct_calc_c(FFTContext *s, FFTSample *output, const FFTSample *input)

 {

     int k;

     int n = 1 << s->mdct_bits;

     int n2 = n >> 1;
     int n4 = n >> 2;

     ff_imdct_half_c(s, output+n4, input);

     for(k = 0; k < n4; k++) {
         output[k] = -output[n2-k-1];
         output[n-k-1] = output[n2+k];

     }
 }
 
 /**

  * Compute MDCT of size N = 2^nbits
  * @param input N samples
  * @param out N/2 samples
  */

 void ff_mdct_calc_c(FFTContext *s, FFTSample *out, const FFTSample *input)

 {
     int i, j, n, n8, n4, n2, n3;

     FFTDouble re, im;

     const uint16_t *revtab = s->revtab;

     const FFTSample *tcos = s->tcos;
     const FFTSample *tsin = s->tsin;

     FFTComplex *x = (FFTComplex *)out;

     n = 1 << s->mdct_bits;

     n2 = n >> 1;
     n4 = n >> 2;
     n8 = n >> 3;
     n3 = 3 * n4;
 
     /* pre rotation */
     for(i=0;i<n8;i++) {

         re = RSCALE(-input[2*i+n3] - input[n3-1-2*i]);
         im = RSCALE(-input[n4+2*i] + input[n4-1-2*i]);

         j = revtab[i];
         CMUL(x[j].re, x[j].im, re, im, -tcos[i], tsin[i]);
 

         re = RSCALE( input[2*i]    - input[n2-1-2*i]);
         im = RSCALE(-input[n2+2*i] - input[ n-1-2*i]);

         j = revtab[n8 + i];
         CMUL(x[j].re, x[j].im, re, im, -tcos[n8 + i], tsin[n8 + i]);
     }
 

     s->fft_calc(s, x);

     /* post rotation */

     for(i=0;i<n8;i++) {
         FFTSample r0, i0, r1, i1;
         CMUL(i1, r0, x[n8-i-1].re, x[n8-i-1].im, -tsin[n8-i-1], -tcos[n8-i-1]);
         CMUL(i0, r1, x[n8+i  ].re, x[n8+i  ].im, -tsin[n8+i  ], -tcos[n8+i  ]);
         x[n8-i-1].re = r0;
         x[n8-i-1].im = i0;
         x[n8+i  ].re = r1;
         x[n8+i  ].im = i1;

     }
 }
 

 av_cold void ff_mdct_end(FFTContext *s)

 {
     av_freep(&s->tcos);

     ff_fft_end(s);

 }