Move dctref prototypes to a header file
[libav.git] / libavcodec / dctref.c
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 libavcodec/dctref.c
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 av_cold void ff_ref_dct_init(void)
42 {
43 unsigned int i, j;
44
45 for (j = 0; j < 8; ++j) {
46 coefficients[j] = sqrt(0.125);
47 for (i = 8; i < 64; i += 8) {
48 coefficients[i + j] = 0.5 * cos(i * (j + 0.5) * M_PI / 64.0);
49 }
50 }
51 }
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 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 for (i = 0; i < 64; i += 8) {
68 for (j = 0; j < 8; ++j) {
69 double tmp = 0;
70 for (k = 0; k < 8; ++k) {
71 tmp += coefficients[i + k] * block[k * 8 + j];
72 }
73 out[i + j] = tmp * 8;
74 }
75 }
76
77 /* block = out * (coefficients') */
78 for (j = 0; j < 8; ++j) {
79 for (i = 0; i < 64; i += 8) {
80 double tmp = 0;
81 for (k = 0; k < 8; ++k) {
82 tmp += out[i + k] * coefficients[j * 8 + k];
83 }
84 block[i + j] = floor(tmp + 0.499999999999);
85 }
86 }
87 }
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 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 for (i = 0; i < 64; i += 8) {
104 for (j = 0; j < 8; ++j) {
105 double tmp = 0;
106 for (k = 0; k < 8; ++k) {
107 tmp += block[i + k] * coefficients[k * 8 + j];
108 }
109 out[i + j] = tmp;
110 }
111 }
112
113 /* block = (coefficients') * out */
114 for (i = 0; i < 8; ++i) {
115 for (j = 0; j < 8; ++j) {
116 double tmp = 0;
117 for (k = 0; k < 64; k += 8) {
118 tmp += coefficients[k + i] * out[k + j];
119 }
120 block[i * 8 + j] = floor(tmp + 0.5);
121 }
122 }
123 }