FFmpeg coverage


Directory: ../../../ffmpeg/
File: src/libavcodec/dctref.c
Date: 2021-09-24 20:55:06
Exec Total Coverage
Lines: 34 34 100.0%
Branches: 28 28 100.0%

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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 520000 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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68
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69 33280000 double tmp = 0;
70
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71 266240000 tmp += coefficients[i + k] * block[k * 8 + j];
72 }
73 33280000 out[i + j] = tmp * 8;
74 }
75 }
76
77 /* block = out * (coefficients') */
78
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79
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80 33280000 double tmp = 0;
81
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82 266240000 tmp += out[i + k] * coefficients[j * 8 + k];
83 }
84 33280000 block[i + j] = floor(tmp + 0.499999999999);
85 }
86 }
87 520000 }
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 1140000 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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105 72960000 double tmp = 0;
106
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107 583680000 tmp += block[i + k] * coefficients[k * 8 + j];
108 }
109 72960000 out[i + j] = tmp;
110 }
111 }
112
113 /* block = (coefficients') * out */
114
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116 72960000 double tmp = 0;
117
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118 583680000 tmp += coefficients[k + i] * out[k + j];
119 }
120 72960000 block[i * 8 + j] = floor(tmp + 0.5);
121 }
122 }
123 1140000 }
124