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"
37 /* sin((M_PI * x / (2*n)) */
38 #define SIN(s,n,x) (s->costab[(n) - (x)])
40 /* cos((M_PI * x / (2*n)) */
41 #define COS(s,n,x) (s->costab[x])
43 static void ff_dst_calc_I_c(DCTContext *ctx, FFTSample *data)
45 int n = 1 << ctx->nbits;
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);
55 tmp1 = (tmp1 - tmp2) * 0.5f;
57 data[n - i] = s - tmp1;
61 ctx->rdft.rdft_calc(&ctx->rdft, data);
65 for(i = 1; i < n-2; i += 2) {
66 data[i + 1] += data[i - 1];
67 data[i ] = -data[i + 2];
73 static void ff_dct_calc_I_c(DCTContext *ctx, FFTSample *data)
75 int n = 1 << ctx->nbits;
77 float next = -0.5f * (data[0] - data[n]);
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);
90 tmp1 = (tmp1 + tmp2) * 0.5f;
92 data[n - i] = tmp1 + s;
95 ctx->rdft.rdft_calc(&ctx->rdft, data);
99 for(i = 3; i <= n; i += 2)
100 data[i] = data[i - 2] - data[i];
103 static void ff_dct_calc_III_c(DCTContext *ctx, FFTSample *data)
105 int n = 1 << ctx->nbits;
108 float next = data[n - 1];
109 float inv_n = 1.0f / n;
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);
117 data[i ] = c * val1 + s * val2;
118 data[i + 1] = s * val1 - c * val2;
123 ctx->rdft.rdft_calc(&ctx->rdft, data);
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);
131 data[i ] = tmp1 + csc;
132 data[n - i - 1] = tmp1 - csc;
136 static void ff_dct_calc_II_c(DCTContext *ctx, FFTSample *data)
138 int n = 1 << ctx->nbits;
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);
148 tmp1 = (tmp1 + tmp2) * 0.5f;
151 data[n-i-1] = tmp1 - s;
154 ctx->rdft.rdft_calc(&ctx->rdft, data);
156 next = data[1] * 0.5;
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);
165 data[i ] = c * inr + s * ini;
169 next += s * inr - c * ini;
173 static void dct32_func(DCTContext *ctx, FFTSample *data)
175 ctx->dct32(data, data);
178 av_cold int ff_dct_init(DCTContext *s, int nbits, enum DCTTransformType inverse)
184 s->inverse = inverse;
186 ff_init_ff_cos_tabs(nbits+2);
188 s->costab = ff_cos_tabs[nbits+2];
190 s->csc2 = av_malloc(n/2 * sizeof(FFTSample));
192 if (ff_rdft_init(&s->rdft, nbits, inverse == DCT_III) < 0) {
197 for (i = 0; i < n/2; i++)
198 s->csc2[i] = 0.5 / sin((M_PI / (2*n) * (2*i + 1)));
201 case DCT_I : s->dct_calc = ff_dct_calc_I_c; break;
202 case DCT_II : s->dct_calc = ff_dct_calc_II_c ; break;
203 case DCT_III: s->dct_calc = ff_dct_calc_III_c; break;
204 case DST_I : s->dct_calc = ff_dst_calc_I_c; break;
207 if (inverse == DCT_II && nbits == 5)
208 s->dct_calc = dct32_func;
211 if (HAVE_MMX) ff_dct_init_mmx(s);
216 av_cold void ff_dct_end(DCTContext *s)
218 ff_rdft_end(&s->rdft);