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
43static void dst_calc_I_c(DCTContext *ctx, FFTSample *data)
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
73static void dct_calc_I_c(DCTContext *ctx, FFTSample *data)
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
103static void dct_calc_III_c(DCTContext *ctx, FFTSample *data)
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
136static void dct_calc_II_c(DCTContext *ctx, FFTSample *data)
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
172static void dct32_func(DCTContext *ctx, FFTSample *data)
173{
174    ctx->dct32(data, data);
175}
176
177av_cold int ff_dct_init(DCTContext *s, int nbits, enum DCTTransformType inverse)
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
195        if (ff_rdft_init(&s->rdft, nbits, inverse == DCT_III) < 0) {
196            av_free(s->csc2);
197            return -1;
198        }
199
200        for (i = 0; i < n / 2; i++)
201            s->csc2[i] = 0.5 / sin((M_PI / (2 * n) * (2 * i + 1)));
202
203        switch (inverse) {
204        case DCT_I  : s->dct_calc = dct_calc_I_c;   break;
205        case DCT_II : s->dct_calc = dct_calc_II_c;  break;
206        case DCT_III: s->dct_calc = dct_calc_III_c; break;
207        case DST_I  : s->dct_calc = dst_calc_I_c;   break;
208        }
209    }
210
211    s->dct32 = ff_dct32_float;
212    if (ARCH_X86)
213        ff_dct_init_x86(s);
214
215    return 0;
216}
217
218av_cold void ff_dct_end(DCTContext *s)
219{
220    ff_rdft_end(&s->rdft);
221    av_free(s->csc2);
222}
223