/*
  * (I)DCT Transforms
  * Copyright (c) 2009 Peter Ross <pross@xvid.org>
  * Copyright (c) 2010 Alex Converse <alex.converse@gmail.com>
  * Copyright (c) 2010 Vitor Sessak
  *
  * 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 St, Fifth Floor, Boston, MA  02110-1301  USA
  */
 
 /**

  * @file

  * (Inverse) Discrete Cosine Transforms. These are also known as the
  * type II and type III DCTs respectively.
  */
 
 #include <math.h>

 #include <string.h>

 #include "libavutil/mathematics.h"

 #include "dct.h"

 #include "dct32.h"

 /* sin((M_PI * x / (2 * n)) */
 #define SIN(s, n, x) (s->costab[(n) - (x)])

 /* cos((M_PI * x / (2 * n)) */
 #define COS(s, n, x) (s->costab[x])

 static void dst_calc_I_c(DCTContext *ctx, FFTSample *data)

 {
     int n = 1 << ctx->nbits;
     int i;
 
     data[0] = 0;

     for (i = 1; i < n / 2; i++) {
         float tmp1   = data[i    ];
         float tmp2   = data[n - i];
         float s      = SIN(ctx, n, 2 * i);
 
         s           *= tmp1 + tmp2;
         tmp1         = (tmp1 - tmp2) * 0.5f;
         data[i]      = s + tmp1;
         data[n - i]  = s - tmp1;

     }
 

     data[n / 2] *= 2;

     ctx->rdft.rdft_calc(&ctx->rdft, data);

 
     data[0] *= 0.5f;
 

     for (i = 1; i < n - 2; i += 2) {
         data[i + 1] +=  data[i - 1];
         data[i]      = -data[i + 2];

     }
 

     data[n - 1] = 0;

 }
 

 static void dct_calc_I_c(DCTContext *ctx, FFTSample *data)

 {
     int n = 1 << ctx->nbits;
     int i;
     float next = -0.5f * (data[0] - data[n]);
 

     for (i = 0; i < n / 2; i++) {
         float tmp1 = data[i];

         float tmp2 = data[n - i];

         float s    = SIN(ctx, n, 2 * i);
         float c    = COS(ctx, n, 2 * i);

 
         c *= tmp1 - tmp2;
         s *= tmp1 - tmp2;
 
         next += c;
 

         tmp1        = (tmp1 + tmp2) * 0.5f;
         data[i]     = tmp1 - s;

         data[n - i] = tmp1 + s;
     }
 

     ctx->rdft.rdft_calc(&ctx->rdft, data);

     data[n] = data[1];
     data[1] = next;
 

     for (i = 3; i <= n; i += 2)

         data[i] = data[i - 2] - data[i];
 }
 

 static void dct_calc_III_c(DCTContext *ctx, FFTSample *data)

 {
     int n = 1 << ctx->nbits;
     int i;
 

     float next  = data[n - 1];

     float inv_n = 1.0f / n;

     for (i = n - 2; i >= 2; i -= 2) {

         float val1 = data[i];

         float val2 = data[i - 1] - data[i + 1];

         float c    = COS(ctx, n, i);
         float s    = SIN(ctx, n, i);

         data[i]     = c * val1 + s * val2;

         data[i + 1] = s * val1 - c * val2;
     }

     data[1] = 2 * next;

     ctx->rdft.rdft_calc(&ctx->rdft, data);

     for (i = 0; i < n / 2; i++) {

         float tmp1 = data[i]         * inv_n;

         float tmp2 = data[n - i - 1] * inv_n;

         float csc  = ctx->csc2[i] * (tmp1 - tmp2);

         tmp1            += tmp2;
         data[i]          = tmp1 + csc;
         data[n - i - 1]  = tmp1 - csc;

     }

 }
 

 static void dct_calc_II_c(DCTContext *ctx, FFTSample *data)

 {
     int n = 1 << ctx->nbits;
     int i;

     float next;

     for (i = 0; i < n / 2; i++) {
         float tmp1 = data[i];

         float tmp2 = data[n - i - 1];

         float s    = SIN(ctx, n, 2 * i + 1);

         s    *= tmp1 - tmp2;
         tmp1  = (tmp1 + tmp2) * 0.5f;

         data[i]     = tmp1 + s;

         data[n-i-1] = tmp1 - s;
     }

     ctx->rdft.rdft_calc(&ctx->rdft, data);

     next     = data[1] * 0.5;

     data[1] *= -1;

     for (i = n - 2; i >= 0; i -= 2) {
         float inr = data[i    ];
         float ini = data[i + 1];

         float c   = COS(ctx, n, i);
         float s   = SIN(ctx, n, i);

         data[i]     = c * inr + s * ini;
         data[i + 1] = next;

         next += s * inr - c * ini;

     }

 }
 

 static void dct32_func(DCTContext *ctx, FFTSample *data)
 {
     ctx->dct32(data, data);

 }
 

 av_cold int ff_dct_init(DCTContext *s, int nbits, enum DCTTransformType inverse)

 {
     int n = 1 << nbits;
     int i;
 

     memset(s, 0, sizeof(*s));
 

     s->nbits   = nbits;
     s->inverse = inverse;

     if (inverse == DCT_II && nbits == 5) {
         s->dct_calc = dct32_func;
     } else {

         ff_init_ff_cos_tabs(nbits + 2);

         s->costab = ff_cos_tabs[nbits + 2];

         s->csc2   = av_malloc_array(n / 2, sizeof(FFTSample));

         if (!s->csc2)
             return AVERROR(ENOMEM);

         if (ff_rdft_init(&s->rdft, nbits, inverse == DCT_III) < 0) {

             av_freep(&s->csc2);

             return -1;
         }

         for (i = 0; i < n / 2; i++)
             s->csc2[i] = 0.5 / sin((M_PI / (2 * n) * (2 * i + 1)));

         switch (inverse) {

         case DCT_I  : s->dct_calc = dct_calc_I_c;   break;
         case DCT_II : s->dct_calc = dct_calc_II_c;  break;
         case DCT_III: s->dct_calc = dct_calc_III_c; break;
         case DST_I  : s->dct_calc = dst_calc_I_c;   break;

         }

     }

     s->dct32 = ff_dct32_float;

     if (ARCH_X86)
         ff_dct_init_x86(s);

     return 0;
 }
 

 av_cold void ff_dct_end(DCTContext *s)
 {
     ff_rdft_end(&s->rdft);

     av_freep(&s->csc2);

 }