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
7 * This file is part of FFmpeg.
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.
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.
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
26 * (Inverse) Discrete Cosine Transforms. These are also known as the
27 * type II and type III DCTs respectively.
31 #include "libavutil/mathematics.h"
38 /* sin((M_PI * x / (2*n)) */
39 #define SIN(s,n,x) (s->costab[(n) - (x)])
41 /* cos((M_PI * x / (2*n)) */
42 #define COS(s,n,x) (s->costab[x])
44 static void ff_dst_calc_I_c(DCTContext *ctx, FFTSample *data)
46 int n = 1 << ctx->nbits;
50 for(i = 1; i < n/2; i++) {
51 float tmp1 = data[i ];
52 float tmp2 = data[n - i];
53 float s = SIN(ctx, n, 2*i);
56 tmp1 = (tmp1 - tmp2) * 0.5f;
58 data[n - i] = s - tmp1;
62 ff_rdft_calc(&ctx->rdft, data);
66 for(i = 1; i < n-2; i += 2) {
67 data[i + 1] += data[i - 1];
68 data[i ] = -data[i + 2];
74 static void ff_dct_calc_I_c(DCTContext *ctx, FFTSample *data)
76 int n = 1 << ctx->nbits;
78 float next = -0.5f * (data[0] - data[n]);
80 for(i = 0; i < n/2; i++) {
81 float tmp1 = data[i ];
82 float tmp2 = data[n - i];
83 float s = SIN(ctx, n, 2*i);
84 float c = COS(ctx, n, 2*i);
91 tmp1 = (tmp1 + tmp2) * 0.5f;
93 data[n - i] = tmp1 + s;
96 ff_rdft_calc(&ctx->rdft, data);
100 for(i = 3; i <= n; i += 2)
101 data[i] = data[i - 2] - data[i];
104 static void ff_dct_calc_III_c(DCTContext *ctx, FFTSample *data)
106 int n = 1 << ctx->nbits;
109 float next = data[n - 1];
110 float inv_n = 1.0f / n;
112 for (i = n - 2; i >= 2; i -= 2) {
113 float val1 = data[i ];
114 float val2 = data[i - 1] - data[i + 1];
115 float c = COS(ctx, n, i);
116 float s = SIN(ctx, n, i);
118 data[i ] = c * val1 + s * val2;
119 data[i + 1] = s * val1 - c * val2;
124 ff_rdft_calc(&ctx->rdft, data);
126 for (i = 0; i < n / 2; i++) {
127 float tmp1 = data[i ] * inv_n;
128 float tmp2 = data[n - i - 1] * inv_n;
129 float csc = ctx->csc2[i] * (tmp1 - tmp2);
132 data[i ] = tmp1 + csc;
133 data[n - i - 1] = tmp1 - csc;
137 static void ff_dct_calc_II_c(DCTContext *ctx, FFTSample *data)
139 int n = 1 << ctx->nbits;
143 for (i=0; i < n/2; i++) {
144 float tmp1 = data[i ];
145 float tmp2 = data[n - i - 1];
146 float s = SIN(ctx, n, 2*i + 1);
149 tmp1 = (tmp1 + tmp2) * 0.5f;
152 data[n-i-1] = tmp1 - s;
155 ff_rdft_calc(&ctx->rdft, data);
157 next = data[1] * 0.5;
160 for (i = n - 2; i >= 0; i -= 2) {
161 float inr = data[i ];
162 float ini = data[i + 1];
163 float c = COS(ctx, n, i);
164 float s = SIN(ctx, n, i);
166 data[i ] = c * inr + s * ini;
170 next += s * inr - c * ini;
174 static void dct32_func(DCTContext *ctx, FFTSample *data)
176 ctx->dct32(data, data);
179 void ff_dct_calc(DCTContext *s, FFTSample *data)
181 s->dct_calc(s, data);
184 av_cold int ff_dct_init(DCTContext *s, int nbits, enum DCTTransformType inverse)
190 s->inverse = inverse;
192 ff_init_ff_cos_tabs(nbits+2);
194 s->costab = ff_cos_tabs[nbits+2];
196 s->csc2 = av_malloc(n/2 * sizeof(FFTSample));
198 if (ff_rdft_init(&s->rdft, nbits, inverse == DCT_III) < 0) {
203 for (i = 0; i < n/2; i++)
204 s->csc2[i] = 0.5 / sin((M_PI / (2*n) * (2*i + 1)));
207 case DCT_I : s->dct_calc = ff_dct_calc_I_c; break;
208 case DCT_II : s->dct_calc = ff_dct_calc_II_c ; break;
209 case DCT_III: s->dct_calc = ff_dct_calc_III_c; break;
210 case DST_I : s->dct_calc = ff_dst_calc_I_c; break;
213 if (inverse == DCT_II && nbits == 5)
214 s->dct_calc = dct32_func;
217 if (HAVE_MMX) ff_dct_init_mmx(s);
222 av_cold void ff_dct_end(DCTContext *s)
224 ff_rdft_end(&s->rdft);