dct.c
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1 /*
2  * (I)DCT Transforms
3  * Copyright (c) 2009 Peter Ross <pross@xvid.org>
4  * Copyright (c) 2010 Alex Converse <alex.converse@gmail.com>
5  * Copyright (c) 2010 Vitor Sessak
6  *
7  * This file is part of Libav.
8  *
9  * Libav is free software; you can redistribute it and/or
10  * modify it under the terms of the GNU Lesser General Public
11  * License as published by the Free Software Foundation; either
12  * version 2.1 of the License, or (at your option) any later version.
13  *
14  * Libav is distributed in the hope that it will be useful,
15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
17  * Lesser General Public License for more details.
18  *
19  * You should have received a copy of the GNU Lesser General Public
20  * License along with Libav; if not, write to the Free Software
21  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
22  */
23 
30 #include <math.h>
31 
32 #include "libavutil/mathematics.h"
33 #include "dct.h"
34 #include "dct32.h"
35 
36 /* sin((M_PI * x / (2 * n)) */
37 #define SIN(s, n, x) (s->costab[(n) - (x)])
38 
39 /* cos((M_PI * x / (2 * n)) */
40 #define COS(s, n, x) (s->costab[x])
41 
43 {
44  int n = 1 << ctx->nbits;
45  int i;
46 
47  data[0] = 0;
48  for (i = 1; i < n / 2; i++) {
49  float tmp1 = data[i ];
50  float tmp2 = data[n - i];
51  float s = SIN(ctx, n, 2 * i);
52 
53  s *= tmp1 + tmp2;
54  tmp1 = (tmp1 - tmp2) * 0.5f;
55  data[i] = s + tmp1;
56  data[n - i] = s - tmp1;
57  }
58 
59  data[n / 2] *= 2;
60  ctx->rdft.rdft_calc(&ctx->rdft, data);
61 
62  data[0] *= 0.5f;
63 
64  for (i = 1; i < n - 2; i += 2) {
65  data[i + 1] += data[i - 1];
66  data[i] = -data[i + 2];
67  }
68 
69  data[n - 1] = 0;
70 }
71 
73 {
74  int n = 1 << ctx->nbits;
75  int i;
76  float next = -0.5f * (data[0] - data[n]);
77 
78  for (i = 0; i < n / 2; i++) {
79  float tmp1 = data[i];
80  float tmp2 = data[n - i];
81  float s = SIN(ctx, n, 2 * i);
82  float c = COS(ctx, n, 2 * i);
83 
84  c *= tmp1 - tmp2;
85  s *= tmp1 - tmp2;
86 
87  next += c;
88 
89  tmp1 = (tmp1 + tmp2) * 0.5f;
90  data[i] = tmp1 - s;
91  data[n - i] = tmp1 + s;
92  }
93 
94  ctx->rdft.rdft_calc(&ctx->rdft, data);
95  data[n] = data[1];
96  data[1] = next;
97 
98  for (i = 3; i <= n; i += 2)
99  data[i] = data[i - 2] - data[i];
100 }
101 
103 {
104  int n = 1 << ctx->nbits;
105  int i;
106 
107  float next = data[n - 1];
108  float inv_n = 1.0f / n;
109 
110  for (i = n - 2; i >= 2; i -= 2) {
111  float val1 = data[i];
112  float val2 = data[i - 1] - data[i + 1];
113  float c = COS(ctx, n, i);
114  float s = SIN(ctx, n, i);
115 
116  data[i] = c * val1 + s * val2;
117  data[i + 1] = s * val1 - c * val2;
118  }
119 
120  data[1] = 2 * next;
121 
122  ctx->rdft.rdft_calc(&ctx->rdft, data);
123 
124  for (i = 0; i < n / 2; i++) {
125  float tmp1 = data[i] * inv_n;
126  float tmp2 = data[n - i - 1] * inv_n;
127  float csc = ctx->csc2[i] * (tmp1 - tmp2);
128 
129  tmp1 += tmp2;
130  data[i] = tmp1 + csc;
131  data[n - i - 1] = tmp1 - csc;
132  }
133 }
134 
136 {
137  int n = 1 << ctx->nbits;
138  int i;
139  float next;
140 
141  for (i = 0; i < n / 2; i++) {
142  float tmp1 = data[i];
143  float tmp2 = data[n - i - 1];
144  float s = SIN(ctx, n, 2 * i + 1);
145 
146  s *= tmp1 - tmp2;
147  tmp1 = (tmp1 + tmp2) * 0.5f;
148 
149  data[i] = tmp1 + s;
150  data[n-i-1] = tmp1 - s;
151  }
152 
153  ctx->rdft.rdft_calc(&ctx->rdft, data);
154 
155  next = data[1] * 0.5;
156  data[1] *= -1;
157 
158  for (i = n - 2; i >= 0; i -= 2) {
159  float inr = data[i ];
160  float ini = data[i + 1];
161  float c = COS(ctx, n, i);
162  float s = SIN(ctx, n, i);
163 
164  data[i] = c * inr + s * ini;
165  data[i + 1] = next;
166 
167  next += s * inr - c * ini;
168  }
169 }
170 
171 static void dct32_func(DCTContext *ctx, FFTSample *data)
172 {
173  ctx->dct32(data, data);
174 }
175 
177 {
178  int n = 1 << nbits;
179  int i;
180 
181  memset(s, 0, sizeof(*s));
182 
183  s->nbits = nbits;
184  s->inverse = inverse;
185 
186  if (inverse == DCT_II && nbits == 5) {
187  s->dct_calc = dct32_func;
188  } else {
189  ff_init_ff_cos_tabs(nbits + 2);
190 
191  s->costab = ff_cos_tabs[nbits + 2];
192  s->csc2 = av_malloc(n / 2 * sizeof(FFTSample));
193 
194  if (ff_rdft_init(&s->rdft, nbits, inverse == DCT_III) < 0) {
195  av_free(s->csc2);
196  return -1;
197  }
198 
199  for (i = 0; i < n / 2; i++)
200  s->csc2[i] = 0.5 / sin((M_PI / (2 * n) * (2 * i + 1)));
201 
202  switch (inverse) {
203  case DCT_I : s->dct_calc = ff_dct_calc_I_c; break;
204  case DCT_II : s->dct_calc = ff_dct_calc_II_c; break;
205  case DCT_III: s->dct_calc = ff_dct_calc_III_c; break;
206  case DST_I : s->dct_calc = ff_dst_calc_I_c; break;
207  }
208  }
209 
210  s->dct32 = ff_dct32_float;
211  if (HAVE_MMX)
212  ff_dct_init_mmx(s);
213 
214  return 0;
215 }
216 
218 {
219  ff_rdft_end(&s->rdft);
220  av_free(s->csc2);
221 }