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|---|---|---|---|
| 1 | /* | ||
| 2 | * reference discrete cosine transform (double precision) | ||
| 3 | * Copyright (C) 2009 Dylan Yudaken | ||
| 4 | * | ||
| 5 | * This file is part of FFmpeg. | ||
| 6 | * | ||
| 7 | * FFmpeg is free software; you can redistribute it and/or | ||
| 8 | * modify it under the terms of the GNU Lesser General Public | ||
| 9 | * License as published by the Free Software Foundation; either | ||
| 10 | * version 2.1 of the License, or (at your option) any later version. | ||
| 11 | * | ||
| 12 | * FFmpeg is distributed in the hope that it will be useful, | ||
| 13 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | ||
| 14 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | ||
| 15 | * Lesser General Public License for more details. | ||
| 16 | * | ||
| 17 | * You should have received a copy of the GNU Lesser General Public | ||
| 18 | * License along with FFmpeg; if not, write to the Free Software | ||
| 19 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA | ||
| 20 | */ | ||
| 21 | |||
| 22 | /** | ||
| 23 | * @file | ||
| 24 | * reference discrete cosine transform (double precision) | ||
| 25 | * | ||
| 26 | * @author Dylan Yudaken (dyudaken at gmail) | ||
| 27 | * | ||
| 28 | * @note This file could be optimized a lot, but is for | ||
| 29 | * reference and so readability is better. | ||
| 30 | */ | ||
| 31 | |||
| 32 | #include "libavutil/mathematics.h" | ||
| 33 | #include "dctref.h" | ||
| 34 | |||
| 35 | static double coefficients[8 * 8]; | ||
| 36 | |||
| 37 | /** | ||
| 38 | * Initialize the double precision discrete cosine transform | ||
| 39 | * functions fdct & idct. | ||
| 40 | */ | ||
| 41 | 5 | av_cold void ff_ref_dct_init(void) | |
| 42 | { | ||
| 43 | unsigned int i, j; | ||
| 44 | |||
| 45 |
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45 | for (j = 0; j < 8; ++j) { |
| 46 | 40 | coefficients[j] = sqrt(0.125); | |
| 47 |
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320 | for (i = 8; i < 64; i += 8) { |
| 48 | 280 | coefficients[i + j] = 0.5 * cos(i * (j + 0.5) * M_PI / 64.0); | |
| 49 | } | ||
| 50 | } | ||
| 51 | 5 | } | |
| 52 | |||
| 53 | /** | ||
| 54 | * Transform 8x8 block of data with a double precision forward DCT <br> | ||
| 55 | * This is a reference implementation. | ||
| 56 | * | ||
| 57 | * @param block pointer to 8x8 block of data to transform | ||
| 58 | */ | ||
| 59 | 460000 | void ff_ref_fdct(short *block) | |
| 60 | { | ||
| 61 | /* implement the equation: block = coefficients * block * coefficients' */ | ||
| 62 | |||
| 63 | unsigned int i, j, k; | ||
| 64 | double out[8 * 8]; | ||
| 65 | |||
| 66 | /* out = coefficients * block */ | ||
| 67 |
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4140000 | for (i = 0; i < 64; i += 8) { |
| 68 |
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| 69 | 29440000 | double tmp = 0; | |
| 70 |
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264960000 | for (k = 0; k < 8; ++k) { |
| 71 | 235520000 | tmp += coefficients[i + k] * block[k * 8 + j]; | |
| 72 | } | ||
| 73 | 29440000 | out[i + j] = tmp * 8; | |
| 74 | } | ||
| 75 | } | ||
| 76 | |||
| 77 | /* block = out * (coefficients') */ | ||
| 78 |
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| 79 |
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| 80 | 29440000 | double tmp = 0; | |
| 81 |
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| 82 | 235520000 | tmp += out[i + k] * coefficients[j * 8 + k]; | |
| 83 | } | ||
| 84 | 29440000 | block[i + j] = floor(tmp + 0.499999999999); | |
| 85 | } | ||
| 86 | } | ||
| 87 | 460000 | } | |
| 88 | |||
| 89 | /** | ||
| 90 | * Transform 8x8 block of data with a double precision inverse DCT <br> | ||
| 91 | * This is a reference implementation. | ||
| 92 | * | ||
| 93 | * @param block pointer to 8x8 block of data to transform | ||
| 94 | */ | ||
| 95 | 1080000 | void ff_ref_idct(short *block) | |
| 96 | { | ||
| 97 | /* implement the equation: block = (coefficients') * block * coefficients */ | ||
| 98 | |||
| 99 | unsigned int i, j, k; | ||
| 100 | double out[8 * 8]; | ||
| 101 | |||
| 102 | /* out = block * coefficients */ | ||
| 103 |
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| 104 |
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| 105 | 69120000 | double tmp = 0; | |
| 106 |
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| 107 | 552960000 | tmp += block[i + k] * coefficients[k * 8 + j]; | |
| 108 | } | ||
| 109 | 69120000 | out[i + j] = tmp; | |
| 110 | } | ||
| 111 | } | ||
| 112 | |||
| 113 | /* block = (coefficients') * out */ | ||
| 114 |
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| 115 |
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| 116 | 69120000 | double tmp = 0; | |
| 117 |
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| 118 | 552960000 | tmp += coefficients[k + i] * out[k + j]; | |
| 119 | } | ||
| 120 | 69120000 | block[i * 8 + j] = floor(tmp + 0.5); | |
| 121 | } | ||
| 122 | } | ||
| 123 | 1080000 | } | |
| 124 |