1/*
2 * This file is part of FFmpeg.
3 *
4 * FFmpeg is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU Lesser General Public
6 * License as published by the Free Software Foundation; either
7 * version 2.1 of the License, or (at your option) any later version.
8 *
9 * FFmpeg is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
12 * Lesser General Public License for more details.
13 *
14 * You should have received a copy of the GNU Lesser General Public
15 * License along with FFmpeg; if not, write to the Free Software
16 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
17 */
18
19#include "libavutil/rational.h"
20
21#include "mpeg12.h"
22#include "mpeg12data.h"
23
24const AVRational ff_mpeg12_frame_rate_tab[16] = {
25    {    0,    0},
26    {24000, 1001},
27    {   24,    1},
28    {   25,    1},
29    {30000, 1001},
30    {   30,    1},
31    {   50,    1},
32    {60000, 1001},
33    {   60,    1},
34  // Xing's 15fps: (9)
35    {   15,    1},
36  // libmpeg3's "Unofficial economy rates": (10-13)
37    {    5,    1},
38    {   10,    1},
39    {   12,    1},
40    {   15,    1},
41    {    0,    0},
42};
43
44void ff_mpeg12_find_best_frame_rate(AVRational frame_rate,
45                                    int *code, int *ext_n, int *ext_d,
46                                    int nonstandard)
47{
48    int mpeg2 = ext_n && ext_d;
49    int max_code = nonstandard ? 12 : 8;
50    int c, n, d, best_c, best_n, best_d;
51    AVRational best_error = { INT_MAX, 1 };
52
53    // Default to NTSC if the inputs make no sense.
54    best_c = 4;
55    best_n = best_d = 1;
56
57    for (c = 1; c <= max_code; c++) {
58        if (av_cmp_q(frame_rate, ff_mpeg12_frame_rate_tab[c]) == 0) {
59            best_c = c;
60            goto found;
61        }
62    }
63
64    for (c = 1; c <= max_code; c++) {
65        for (n = 1; n <= (mpeg2 ? 4 : 1); n++) {
66            for (d = 1; d <= (mpeg2 ? 32 : 1); d++) {
67                AVRational test, error;
68                int cmp;
69
70                test = av_mul_q(ff_mpeg12_frame_rate_tab[c],
71                                (AVRational) { n, d });
72
73                cmp = av_cmp_q(test, frame_rate);
74                if (cmp == 0) {
75                    best_c = c;
76                    best_n = n;
77                    best_d = d;
78                    goto found;
79                }
80
81                if (cmp < 0)
82                    error = av_div_q(frame_rate, test);
83                else
84                    error = av_div_q(test, frame_rate);
85
86                cmp = av_cmp_q(error, best_error);
87                if (cmp < 0 || (cmp == 0 && n == 1 && d == 1)) {
88                    best_c = c;
89                    best_n = n;
90                    best_d = d;
91                    best_error = error;
92                }
93            }
94        }
95    }
96
97found:
98    *code = best_c;
99    if (mpeg2) {
100        *ext_n = best_n - 1;
101        *ext_d = best_d - 1;
102    }
103}
104