08ffd3708b
No change in performance if they do not vary. Originally committed as revision 17840 to svn://svn.ffmpeg.org/ffmpeg/trunk
77 lines
2.3 KiB
C
77 lines
2.3 KiB
C
/*
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* Delay Locked Loop based time filter
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* Copyright (c) 2009 Samalyse
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* Author: Olivier Guilyardi <olivier samalyse com>
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*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include "config.h"
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#include "avformat.h"
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#include "timefilter.h"
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struct TimeFilter {
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/// Delay Locked Loop data. These variables refer to mathematical
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/// concepts described in: http://www.kokkinizita.net/papers/usingdll.pdf
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double cycle_time;
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double feedback2_factor;
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double feedback3_factor;
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double integrator2_state;
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};
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TimeFilter * ff_timefilter_new(double feedback2_factor, double feedback3_factor)
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{
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TimeFilter *self = av_mallocz(sizeof(TimeFilter));
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self->integrator2_state = 1.0;
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self->feedback2_factor = feedback2_factor;
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self->feedback3_factor = feedback3_factor;
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return self;
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}
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void ff_timefilter_destroy(TimeFilter *self)
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{
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av_freep(&self);
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}
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void ff_timefilter_reset(TimeFilter *self)
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{
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self->cycle_time = 0;
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}
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void ff_timefilter_update(TimeFilter *self, double system_time, double period)
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{
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if (!self->cycle_time) {
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/// init loop
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self->cycle_time = system_time;
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} else {
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double loop_error;
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self->cycle_time+= self->integrator2_state * period;
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/// calculate loop error
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loop_error = system_time - self->cycle_time;
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/// update loop
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self->cycle_time += self->feedback2_factor * loop_error;
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self->integrator2_state += self->feedback3_factor * loop_error / period;
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}
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}
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double ff_timefilter_read(TimeFilter *self)
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{
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return self->cycle_time;
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}
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