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/*
* Delay Locked Loop based time filter
* Copyright (c) 2009 Samalyse
* Author: Olivier Guilyardi <olivier samalyse com>
*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "config.h"
#include "avformat.h"
#include "timefilter.h"
struct TimeFilter {
/// Delay Locked Loop data. These variables refer to mathematical
/// concepts described in: http://www.kokkinizita.net/papers/usingdll.pdf
double cycle_time;
double feedback2_factor;
double feedback3_factor;
double integrator2_state;
};
TimeFilter * ff_timefilter_new(double period, double feedback2_factor, double feedback3_factor)
{
TimeFilter *self = av_mallocz(sizeof(TimeFilter));
self->integrator2_state = period;
self->feedback2_factor = feedback2_factor;
self->feedback3_factor = feedback3_factor;
return self;
}
void ff_timefilter_destroy(TimeFilter *self)
{
av_freep(&self);
}
void ff_timefilter_reset(TimeFilter *self)
{
self->cycle_time = 0;
}
void ff_timefilter_update(TimeFilter *self, double system_time)
{
if (!self->cycle_time) {
/// init loop
self->cycle_time = system_time;
} else {
double loop_error;
self->cycle_time+= self->integrator2_state;
/// calculate loop error
loop_error = system_time - self->cycle_time;
/// update loop
self->cycle_time += self->feedback2_factor * loop_error;
self->integrator2_state += self->feedback3_factor * loop_error;
}
}
double ff_timefilter_read(TimeFilter *self)
{
return self->cycle_time;
}
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