2 Copyright (C) 2012-2015 Carl Hetherington <cth@carlh.net>
4 This file is part of DCP-o-matic.
6 DCP-o-matic is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 2 of the License, or
9 (at your option) any later version.
11 DCP-o-matic is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with DCP-o-matic. If not, see <http://www.gnu.org/licenses/>.
22 #include "frame_rate_change.h"
23 #include "compose.hpp"
30 about_equal (double a, double b)
32 /* A film of F seconds at f FPS will be Ff frames;
33 Consider some delta FPS d, so if we run the same
34 film at (f + d) FPS it will last F(f + d) seconds.
36 Hence the difference in length over the length of the film will
37 be F(f + d) - Ff frames
42 So if we accept a difference of 1 frame, ie 1/f seconds, we can
49 So for a 3hr film, ie F = 3 * 60 * 60 = 10800, the acceptable
50 FPS error is 1/F ~= 0.0001 ~= 10-e4
53 return (fabs (a - b) < 1e-4);
57 FrameRateChange::FrameRateChange (double source_, int dcp_)
62 , change_speed (false)
64 if (fabs (source / 2.0 - dcp) < fabs (source - dcp)) {
65 /* The difference between source and DCP frame rate will be lower
66 (i.e. better) if we skip.
69 } else if (fabs (source * 2 - dcp) < fabs (source - dcp)) {
70 /* The difference between source and DCP frame rate would be better
71 if we repeated each frame once; it may be better still if we
72 repeated more than once. Work out the required repeat.
74 repeat = round (dcp / source);
77 speed_up = dcp / (source * factor());
78 change_speed = !about_equal (speed_up, 1.0);
82 FrameRateChange::description () const
86 if (!skip && repeat == 1 && !change_speed) {
87 description = _("Content and DCP have the same rate.\n");
90 description = _("DCP will use every other frame of the content.\n");
91 } else if (repeat == 2) {
92 description = _("Each content frame will be doubled in the DCP.\n");
93 } else if (repeat > 2) {
94 description = String::compose (_("Each content frame will be repeated %1 more times in the DCP.\n"), repeat - 1);
98 double const pc = dcp * 100 / (source * factor());
99 description += String::compose (_("DCP will run at %1%% of the content speed.\n"), pc);