| 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 | |
| 43 | static 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 | |
| 73 | static 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 | |
| 103 | static 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 | |
| 136 | static 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 | |
| 172 | static void dct32_func(DCTContext *ctx, FFTSample *data) |
| 173 | { |
| 174 | ctx->dct32(data, data); |
| 175 | } |
| 176 | |
| 177 | av_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_freep(&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 | |
| 218 | av_cold void ff_dct_end(DCTContext *s) |
| 219 | { |
| 220 | ff_rdft_end(&s->rdft); |
| 221 | av_freep(&s->csc2); |
| 222 | } |