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.
33 #include "libavutil/error.h"
34 #include "libavutil/mathematics.h"
35 #include "libavutil/mem.h"
39 /* sin((M_PI * x / (2 * n)) */
40 #define SIN(s, n, x) (s->costab[(n) - (x)])
42 /* cos((M_PI * x / (2 * n)) */
43 #define COS(s, n, x) (s->costab[x])
45 static void dst_calc_I_c(DCTContext *ctx, FFTSample *data)
47 int n = 1 << ctx->nbits;
51 for (i = 1; i < n / 2; i++) {
52 float tmp1 = data[i ];
53 float tmp2 = data[n - i];
54 float s = SIN(ctx, n, 2 * i);
57 tmp1 = (tmp1 - tmp2) * 0.5f;
59 data[n - i] = s - tmp1;
63 ctx->rdft.rdft_calc(&ctx->rdft, data);
67 for (i = 1; i < n - 2; i += 2) {
68 data[i + 1] += data[i - 1];
69 data[i] = -data[i + 2];
75 static void dct_calc_I_c(DCTContext *ctx, FFTSample *data)
77 int n = 1 << ctx->nbits;
79 float next = -0.5f * (data[0] - data[n]);
81 for (i = 0; i < n / 2; i++) {
83 float tmp2 = data[n - i];
84 float s = SIN(ctx, n, 2 * i);
85 float c = COS(ctx, n, 2 * i);
92 tmp1 = (tmp1 + tmp2) * 0.5f;
94 data[n - i] = tmp1 + s;
97 ctx->rdft.rdft_calc(&ctx->rdft, data);
101 for (i = 3; i <= n; i += 2)
102 data[i] = data[i - 2] - data[i];
105 static void dct_calc_III_c(DCTContext *ctx, FFTSample *data)
107 int n = 1 << ctx->nbits;
110 float next = data[n - 1];
111 float inv_n = 1.0f / n;
113 for (i = n - 2; i >= 2; i -= 2) {
114 float val1 = data[i];
115 float val2 = data[i - 1] - data[i + 1];
116 float c = COS(ctx, n, i);
117 float s = SIN(ctx, n, i);
119 data[i] = c * val1 + s * val2;
120 data[i + 1] = s * val1 - c * val2;
125 ctx->rdft.rdft_calc(&ctx->rdft, data);
127 for (i = 0; i < n / 2; i++) {
128 float tmp1 = data[i] * inv_n;
129 float tmp2 = data[n - i - 1] * inv_n;
130 float csc = ctx->csc2[i] * (tmp1 - tmp2);
133 data[i] = tmp1 + csc;
134 data[n - i - 1] = tmp1 - csc;
138 static void dct_calc_II_c(DCTContext *ctx, FFTSample *data)
140 int n = 1 << ctx->nbits;
144 for (i = 0; i < n / 2; i++) {
145 float tmp1 = data[i];
146 float tmp2 = data[n - i - 1];
147 float s = SIN(ctx, n, 2 * i + 1);
150 tmp1 = (tmp1 + tmp2) * 0.5f;
153 data[n-i-1] = tmp1 - s;
156 ctx->rdft.rdft_calc(&ctx->rdft, data);
158 next = data[1] * 0.5;
161 for (i = n - 2; i >= 0; i -= 2) {
162 float inr = data[i ];
163 float ini = data[i + 1];
164 float c = COS(ctx, n, i);
165 float s = SIN(ctx, n, i);
167 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 av_cold int ff_dct_init(DCTContext *s, int nbits, enum DCTTransformType inverse)
185 memset(s, 0, sizeof(*s));
188 s->inverse = inverse;
190 if (inverse == DCT_II && nbits == 5) {
191 s->dct_calc = dct32_func;
193 ff_init_ff_cos_tabs(nbits + 2);
195 s->costab = ff_cos_tabs[nbits + 2];
196 s->csc2 = av_malloc_array(n / 2, sizeof(FFTSample));
198 return AVERROR(ENOMEM);
200 if ((ret = ff_rdft_init(&s->rdft, nbits, inverse == DCT_III)) < 0) {
205 for (i = 0; i < n / 2; i++)
206 s->csc2[i] = 0.5 / sin((M_PI / (2 * n) * (2 * i + 1)));
209 case DCT_I : s->dct_calc = dct_calc_I_c; break;
210 case DCT_II : s->dct_calc = dct_calc_II_c; break;
211 case DCT_III: s->dct_calc = dct_calc_III_c; break;
212 case DST_I : s->dct_calc = dst_calc_I_c; break;
216 s->dct32 = ff_dct32_float;
224 av_cold void ff_dct_end(DCTContext *s)
226 ff_rdft_end(&s->rdft);