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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 FFmpeg.
8  *
9  * FFmpeg 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  * FFmpeg 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 FFmpeg; if not, write to the Free Software
21  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
22  */
23 
24 /**
25  * @file
26  * (Inverse) Discrete Cosine Transforms. These are also known as the
27  * type II and type III DCTs respectively.
28  */
29 
30 #include <math.h>
31 #include <string.h>
32 
33 #include "libavutil/mathematics.h"
34 #include "dct.h"
35 #include "dct32.h"
36 
37 /* sin((M_PI * x / (2 * n)) */
38 #define SIN(s, n, x) (s->costab[(n) - (x)])
39 
40 /* cos((M_PI * x / (2 * n)) */
41 #define COS(s, n, x) (s->costab[x])
42 
44 {
45  int n = 1 << ctx->nbits;
46  int i;
47 
48  data[0] = 0;
49  for (i = 1; i < n / 2; i++) {
50  float tmp1 = data[i ];
51  float tmp2 = data[n - i];
52  float s = SIN(ctx, n, 2 * i);
53 
54  s *= tmp1 + tmp2;
55  tmp1 = (tmp1 - tmp2) * 0.5f;
56  data[i] = s + tmp1;
57  data[n - i] = s - tmp1;
58  }
59 
60  data[n / 2] *= 2;
61  ctx->rdft.rdft_calc(&ctx->rdft, data);
62 
63  data[0] *= 0.5f;
64 
65  for (i = 1; i < n - 2; i += 2) {
66  data[i + 1] += data[i - 1];
67  data[i] = -data[i + 2];
68  }
69 
70  data[n - 1] = 0;
71 }
72 
74 {
75  int n = 1 << ctx->nbits;
76  int i;
77  float next = -0.5f * (data[0] - data[n]);
78 
79  for (i = 0; i < n / 2; i++) {
80  float tmp1 = data[i];
81  float tmp2 = data[n - i];
82  float s = SIN(ctx, n, 2 * i);
83  float c = COS(ctx, n, 2 * i);
84 
85  c *= tmp1 - tmp2;
86  s *= tmp1 - tmp2;
87 
88  next += c;
89 
90  tmp1 = (tmp1 + tmp2) * 0.5f;
91  data[i] = tmp1 - s;
92  data[n - i] = tmp1 + s;
93  }
94 
95  ctx->rdft.rdft_calc(&ctx->rdft, data);
96  data[n] = data[1];
97  data[1] = next;
98 
99  for (i = 3; i <= n; i += 2)
100  data[i] = data[i - 2] - data[i];
101 }
102 
104 {
105  int n = 1 << ctx->nbits;
106  int i;
107 
108  float next = data[n - 1];
109  float inv_n = 1.0f / n;
110 
111  for (i = n - 2; i >= 2; i -= 2) {
112  float val1 = data[i];
113  float val2 = data[i - 1] - data[i + 1];
114  float c = COS(ctx, n, i);
115  float s = SIN(ctx, n, i);
116 
117  data[i] = c * val1 + s * val2;
118  data[i + 1] = s * val1 - c * val2;
119  }
120 
121  data[1] = 2 * next;
122 
123  ctx->rdft.rdft_calc(&ctx->rdft, data);
124 
125  for (i = 0; i < n / 2; i++) {
126  float tmp1 = data[i] * inv_n;
127  float tmp2 = data[n - i - 1] * inv_n;
128  float csc = ctx->csc2[i] * (tmp1 - tmp2);
129 
130  tmp1 += tmp2;
131  data[i] = tmp1 + csc;
132  data[n - i - 1] = tmp1 - csc;
133  }
134 }
135 
137 {
138  int n = 1 << ctx->nbits;
139  int i;
140  float next;
141 
142  for (i = 0; i < n / 2; i++) {
143  float tmp1 = data[i];
144  float tmp2 = data[n - i - 1];
145  float s = SIN(ctx, n, 2 * i + 1);
146 
147  s *= tmp1 - tmp2;
148  tmp1 = (tmp1 + tmp2) * 0.5f;
149 
150  data[i] = tmp1 + s;
151  data[n-i-1] = tmp1 - s;
152  }
153 
154  ctx->rdft.rdft_calc(&ctx->rdft, data);
155 
156  next = data[1] * 0.5;
157  data[1] *= -1;
158 
159  for (i = n - 2; i >= 0; i -= 2) {
160  float inr = data[i ];
161  float ini = data[i + 1];
162  float c = COS(ctx, n, i);
163  float s = SIN(ctx, n, i);
164 
165  data[i] = c * inr + s * ini;
166  data[i + 1] = next;
167 
168  next += s * inr - c * ini;
169  }
170 }
171 
173 {
174  ctx->dct32(data, data);
175 }
176 
178 {
179  int n = 1 << nbits;
180  int i;
181 
182  memset(s, 0, sizeof(*s));
183 
184  s->nbits = nbits;
185  s->inverse = inverse;
186 
187  if (inverse == DCT_II && nbits == 5) {
188  s->dct_calc = dct32_func;
189  } else {
190  ff_init_ff_cos_tabs(nbits + 2);
191 
192  s->costab = ff_cos_tabs[nbits + 2];
193  s->csc2 = av_malloc_array(n / 2, sizeof(FFTSample));
194  if (!s->csc2)
195  return AVERROR(ENOMEM);
196 
197  if (ff_rdft_init(&s->rdft, nbits, inverse == DCT_III) < 0) {
198  av_freep(&s->csc2);
199  return -1;
200  }
201 
202  for (i = 0; i < n / 2; i++)
203  s->csc2[i] = 0.5 / sin((M_PI / (2 * n) * (2 * i + 1)));
204 
205  switch (inverse) {
206  case DCT_I : s->dct_calc = dct_calc_I_c; break;
207  case DCT_II : s->dct_calc = dct_calc_II_c; break;
208  case DCT_III: s->dct_calc = dct_calc_III_c; break;
209  case DST_I : s->dct_calc = dst_calc_I_c; break;
210  }
211  }
212 
213  s->dct32 = ff_dct32_float;
214  if (ARCH_X86)
215  ff_dct_init_x86(s);
216 
217  return 0;
218 }
219 
221 {
222  ff_rdft_end(&s->rdft);
223  av_freep(&s->csc2);
224 }
av_cold void ff_rdft_end(RDFTContext *s)
Definition: rdft.c:132
const char * s
Definition: avisynth_c.h:768
static void dct32_func(DCTContext *ctx, FFTSample *data)
Definition: dct.c:172
void(* dct_calc)(struct DCTContext *s, FFTSample *data)
Definition: dct.h:37
ptrdiff_t const GLvoid * data
Definition: opengl_enc.c:101
const float * costab
Definition: dct.h:35
Definition: avfft.h:95
static void dct_calc_I_c(DCTContext *ctx, FFTSample *data)
Definition: dct.c:73
RDFTContext rdft
Definition: dct.h:34
void ff_dct_init_x86(DCTContext *s)
Definition: dct_init.c:29
#define av_cold
Definition: attributes.h:82
int nbits
Definition: dct.h:32
DCTTransformType
Definition: avfft.h:93
#define AVERROR(e)
Definition: error.h:43
float FFTSample
Definition: avfft.h:35
void(* rdft_calc)(struct RDFTContext *s, FFTSample *z)
Definition: rdft.h:60
Definition: avfft.h:97
static void dct_calc_II_c(DCTContext *ctx, FFTSample *data)
Definition: dct.c:136
AVFormatContext * ctx
Definition: movenc.c:48
Definition: dct.h:31
#define COS(s, n, x)
Definition: dct.c:41
int n
Definition: avisynth_c.h:684
void ff_dct32_float(float *dst, const float *src)
static void dct_calc_III_c(DCTContext *ctx, FFTSample *data)
Definition: dct.c:103
int inverse
Definition: dct.h:33
void(* dct32)(FFTSample *out, const FFTSample *in)
Definition: dct.h:38
av_cold int ff_dct_init(DCTContext *s, int nbits, enum DCTTransformType inverse)
Set up DCT.
Definition: dct.c:177
#define ff_init_ff_cos_tabs
Definition: fft.h:141
Definition: avfft.h:94
FFTSample * csc2
Definition: dct.h:36
static void dst_calc_I_c(DCTContext *ctx, FFTSample *data)
Definition: dct.c:43
#define SIN(s, n, x)
Definition: dct.c:38
static AVCodec * c
av_cold void ff_dct_end(DCTContext *s)
Definition: dct.c:220
#define av_freep(p)
#define M_PI
Definition: mathematics.h:52
static uint32_t inverse(uint32_t v)
find multiplicative inverse modulo 2 ^ 32
Definition: asfcrypt.c:35
#define av_malloc_array(a, b)
Definition: avfft.h:96
av_cold int ff_rdft_init(RDFTContext *s, int nbits, enum RDFTransformType trans)
Set up a real FFT.
Definition: rdft.c:99