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/*
Copyright (C) 2012-2015 Carl Hetherington <cth@carlh.net>
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#include <cmath>
#include "frame_rate_change.h"
#include "compose.hpp"
#include "i18n.h"
using std::string;
static bool
about_equal (double a, double b)
{
/* A film of F seconds at f FPS will be Ff frames;
Consider some delta FPS d, so if we run the same
film at (f + d) FPS it will last F(f + d) seconds.
Hence the difference in length over the length of the film will
be F(f + d) - Ff frames
= Ff + Fd - Ff frames
= Fd frames
= Fd/f seconds
So if we accept a difference of 1 frame, ie 1/f seconds, we can
say that
1/f = Fd/f
ie 1 = Fd
ie d = 1/F
So for a 3hr film, ie F = 3 * 60 * 60 = 10800, the acceptable
FPS error is 1/F ~= 0.0001 ~= 10-e4
*/
return (fabs (a - b) < 1e-4);
}
FrameRateChange::FrameRateChange (double source_, int dcp_)
: source (source_)
, dcp (dcp_)
, skip (false)
, repeat (1)
, change_speed (false)
{
if (fabs (source / 2.0 - dcp) < fabs (source - dcp)) {
/* The difference between source and DCP frame rate will be lower
(i.e. better) if we skip.
*/
skip = true;
} else if (fabs (source * 2 - dcp) < fabs (source - dcp)) {
/* The difference between source and DCP frame rate would be better
if we repeated each frame once; it may be better still if we
repeated more than once. Work out the required repeat.
*/
repeat = round (dcp / source);
}
speed_up = dcp / (source * factor());
change_speed = !about_equal (speed_up, 1.0);
}
string
FrameRateChange::description () const
{
string description;
if (!skip && repeat == 1 && !change_speed) {
description = _("Content and DCP have the same rate.\n");
} else {
if (skip) {
description = _("DCP will use every other frame of the content.\n");
} else if (repeat == 2) {
description = _("Each content frame will be doubled in the DCP.\n");
} else if (repeat > 2) {
description = String::compose (_("Each content frame will be repeated %1 more times in the DCP.\n"), repeat - 1);
}
if (change_speed) {
double const pc = dcp * 100 / (source * factor());
description += String::compose (_("DCP will run at %1%% of the content speed.\n"), pc);
}
}
return description;
}
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